Expansion of core–shell PS/PMMA particles

Structured micrometric polystyrene/poly(methyl methacrylate) particles were obtained by suspension polymerization and their expansion behavior was investigated using n‐pentane as blowing agent. The expanded particles presented two distinct microstructures with an outer region (PMMA‐rich shell) composed by cells of about 10 µm while the center of the particle (PS‐rich core) had much larger cells (50–100 μm). The core–shell particles did not expand at 100°C meaning that the PMMA shell hindered the expansion of the particles. Maximum expansion was dependent on the PMMA concentration and also on the heating temperature and the increase in the PMMA molar mass led to a delay in the onset of the process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4521–4527, 2013     

Treatment of Chronic Kidney Disease with Extracellular Vesicles from Mesenchymal Stem Cells and CD133+ Expanded Cells: A Comparative Preclinical Analysis

Chronic kidney disease (CKD) is characterized by structural abnormalities and the progressive loss of kidney function. Extracellular vesicles (EVs) from human umbilical cord tissue (hUCT)-derived mesenchymal stem cells (MSCs) and expanded human umbilical cord blood (hUCB)-derived CD133⁺ cells (eCD133⁺) maintain the characteristics of the parent cells, providing a new form of cell-free treatment. We evaluated the effects of EVs from hUCT-derived MSCs and hUCB-derived CD133⁺ cells on rats with CDK induced by an adenine-enriched diet. EVs were isolated by ultracentrifugation and characterized by nanoparticle tracking analysis (NTA) and electron microscopy. The animals were randomized and divided into the MSC-EV group, eEPC-EV group and control group. Infusions occurred on the seventh and 14th days after CKD induction. Evaluations of kidney function were carried out by biochemical and histological analyses. Intense labeling of the α-SMA protein was observed when comparing the control with MSC-EVs. In both groups treated with EVs, a significant increase in serum albumin was observed, and the increase in cystatin C was inhibited. The results indicated improvements in renal function in CKD, demonstrating the therapeutic potential of EVs derived from MSCs and eCD133⁺ cells and suggesting the possibility that in the future, more than one type of EV will be used concurrently.     

Semi-Empirical Modeling of Gas–Liquid Mass Transfer in Gas–Liquid–Liquid Systems in Stirred Tanks

Two semi-empirical models of gas–liquid mass transfer in gas–liquid–liquid systems are presented, one for the case where the dispersed liquid phase has a positive spreading coefficient S > 0, the other for S < 0. The models are based on mathematical expressions inspired by assumed mass transfer mechanisms, which are different depending on the oil spreading characteristics. Model simulations compare well with experimental data (up to oil phase holdup ? ～ 0.1), managing to simulate the shape of the experimental curves of oxygen mass transfer enhancement factor E vs. ? for the air–water–heptane (S > 0) and air–water–dodecane (S < 0) systems, better than other models available in the literature.     

Removal of lindane using electrokinetic soil flushing coupled with air stripping

Journal of Applied Electrochemistry - This paper evaluates the remediation of soil spiked with lindane using a combined treatment consisting of electrokinetic soil flushing (EKSF) with air...     

Determining the residual alcohol in biodiesel through its flash point

A simple low cost method is proposed for the quantitative analysis of residual alcohol in biodiesel through determination of the flash point, with which it is correlated. Methyl ester biodiesels from vegetable oils such as corn, soy and sunflower were prepared. The ethyl ester was obtained from soy oil and methyl biodiesel was also synthesized from bovine fat. In all cases it became very evident that there is a direct correlation between the flash point and the residual alcohol content in the prepared biodiesel. Therefore this parameter can be used to directly determine the residual alcohol content of the product.     

Preparation,structure, and properties of montmorillonite/cellulose II/natural rubber nanocomposites

In this work, sodium montmorillonite clay was added, as filler, to nanocomposites of natural rubber (NR) and cellulose II (regenerated cellulose) in amounts varying from 0 to 5 phr (per hundred resin). Natural rubber (NR)/cellulose II/montmorillonite nanocomposites were prepared by co‐coagulating NR latex, montmorillonite aqueous suspension and cellulose xanthate. The clay was previously exfoliated in water, and the resulting suspension was then added to the mixture of NR latex with cellulose xanthate. Morphological, rheometric, mechanical, and dynamic mechanical properties were evaluated, and an increase in these properties was observed upon the addition of cellulose and clay nanomaterials to the rubber matrix. The results show the advantage in using cellulose as a nanopolymer as well as MMT as nanofiller. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synergistic action between Caryocar coriaceum Wittm. fixed oil with aminoglycosides in vitro

The oil obtained from the Caryocar coriaceum Wittm. (pequi) fruit pulp (C. coriaceum fixed oil – CCFO), rich in fatty acids, has been secularly employed by traditional medicine in the treatment of respiratory affections, skin inflammation, and wounds. These observations encouraged us to investigate the antimicrobial activity of CCFO and to investigate its effect in combination with aminoglycosides. The minimum inhibitory concentration (MIC) of CCFO alone and associated with aminoglycosides against Escherichia coli and Staphylococcus aureus strains were determined using microdilution assay. CCFO alone had a MIC of 512 µg/mL against E. coli and S. aureus resistant strains. Combining the CCFO with aminoglycosides reduced the MIC of aminoglycosides against the resistant strains of E. coli and S. aureus. The results obtained indicate that CCFO displays a significant synergistic antibiotic effect when combined with aminoglycosides, demonstrating that the oil constituents (fatty acids) may act as potentiators of the antibiotic activity of aminoglycosides. These properties make CCFO oil an interesting alternative as a remedy or nutraceutical against multiresistant bacteria, preventing the development of resistance by these microorganisms. Practical applications: This article demonstrates the capacity of the C. coriaceum oil to enhance the antibiotic activity of aminoglycosides. This activity could represent a new way to combat the growing bacterial resistance to antibiotics, an important problem of public health.     

Polyethylenes produced with zirconocene immobilized on MAO-modified silicas

The effect of Al content on MAO-modified silicas was evaluated on catalyst activity, on polymer properties and on residual metal content in the resulting polyethylenes. MAO-modified silicas were prepared by impregnating MAO toluene solutions in concentration range between 0.5 and 20.0 wt% Al/SiO₂. Commercial MAO-modified silica (Witco) containing 24.4 wt% Al/SiO₂ was used for comparative reasons. The resulting modified-silicas were employed as supports for grafting (nBuCp)₂ZrCl₂. Using external MAO as cocatalyst (Al/Zr=2000) no difference in catalyst activity was observed. Nevertheless, for Al/Zr=500, catalyst activities were shown to be higher for supported zirconocene systems containing 0.0-2.0 wt% Al/SiO₂ range. According to DSC analysis, one T_m peak was detected for polymer obtained with catalyst prepared with 0.5 wt% Al/SiO₂ (135 °C), but two T_m peaks were observed for polymers obtained with catalysts prepared with 10.0 wt% Al/SiO₂ (136 and 141 °C) and 20.0 wt% Al/SiO₂ (133 and 141 °C).     

Arabinosylated phenolics obtained from SO2‐steam‐pretreated sugarcane bagasse

A pentose‐rich hydrolysate fraction obtained by extraction of steam‐pretreated sugarcane bagasse was analysed with regard to dissolved phenolics. The liquid obtained after steam pretreatment (2% SO₂ (w/w) at 190 °C for 5 min) was divided into two parts: one containing dissolved compounds originating from hemicellulose (with xylose as the dominating compound), and the other containing predominantly dissolved compounds originating from lignin. Using nuclear magnetic resonance, the main dissolved compounds originating from lignin were identified as the glycosylated aromatics, 5‐O‐(trans‐feruloyl)‐L‐Arabinofuranose and 5‐O‐(trans‐coumaroyl)‐L‐Arabinofuranose, together with p‐coumaric acid and small amounts of more common free phenolics such as p‐hydroxybenzaldehyde, p‐hydroxybenzoic acid and vanillin. The phenolic compounds were analysed and quantified using reversed‐phase high‐performance liquid chromatography. The findings show that SO₂ steam explosion opened up new degradation pathways during lignin degradation. Copyright © 2012 Society of Chemical Industry     

Poly(ethylene glycol)-interpenetrated genipin-crosslinked chitosan hydrogels: Structure,pH responsiveness,gelation kinetics,and rheology

In the development of pH-responsive chitosan-based hydrogels, achieving reproducible porosity and swelling behavior is essential for the design of hydrogel networks. Herein, we enhance the level of control in hydrogel microarchitecture by incorporating poly(ethylene glycol) (PEG) into the chitosan–genipin matrix. Hydrogels, varied in composition, were synthesized under mild conditions (37°C, 1 atm, 24 hr), yielding microporous structures with a pore diameter ranging from 11 to 57 μm and an average cross-sectional porosity of approximately 40–64%. Compared to chitosan–genipin hydrogels without PEG, presence of PEG in concentrations up to 1.9 mM generated the same effect as would increase in genipin content, yielding structures with a smaller pore diameter, a lower swelling degree in pH 2 buffer and a higher elastic modulus. Considering cost effectiveness and scale-up, reducing genipin content by the addition of PEG is favorable. Importantly, hydrogel samples containing higher concentrations of PEG (2.9 mM and above) showed a sudden increase in the swelling degree accompanied with a decrease in the elastic modulus. Findings showcase the potential variation in the composition of these hydrogels has in yielding scaffolds with significantly different physico-chemical behaviors.