<Emphasis Type="Italic">St-MMA-BuA</Emphasis> terpolymerization in emulsion: II. The kinetic azeotropy and the problem of homogeneity in composition

An analysis of the kinetic azeotropy of the terpolymer from styrene(St)-methyl methacrylate(MMA)-butyl acrylate(BuA) in emulsion polymerization is effectuated. The objective is to determine the conditions for obtaining terpolymers uniform in composition. In this regard, a composition near to the unitary azeotrope is used in batch, semicontinuous and seeded emulsion polymerization processes. As expected, the monomer partition between the different phases modifies the terpolymer composition, in particular at the beginning of the semicontinuous processes. It is also observed that the unitary azeotrope in batch and semicontinuous emulsion polymerization is conserved in a large range of conversion due to the constancy of monomer concentration and radicals in the particle. In this way, a terpolymer with almost an accumulated constant composition is obtained in the seeded process. A thermodynamic analysis of the kinetic azeotropy is also made. The correspondence between the azeotropes of the binary copolymers and the values of the Flory interaction parameters of the monomers χ _ιj is correlated. It is found that the lesser repulsion of the St-MMA pair respect to that of St-BuA provoked that the composition of the terpolymer tends to the copolymer azeotrope of St-MMA.     

Structural,electric modulus and complex impedance analysis of ZnO/TiO2 composite ceramics

ZnO/TiO₂ composite ceramics have been prepared by solid‐state reaction technique at 900°C. The X‐ray diffraction results revealed the formation of secondary phases referred to as spinel Zn₂TiO₄ and hexagonal ZnTiO₃. The structural analysis showed that all the composites that have been prepared have a polycrystalline nature and a hexagonal wurtzite structure. The complex modulus (M) and electric impedance of the samples have been investigated by broadband dielectric spectroscopy in a wide range of temperature (40°C‐110°C) and frequency (0.1 Hz to 10 MHz). The modulus plots (M′′, M′) illustrate the presence of non‐Debye type of relaxations attributed to the effects of interfacial and dipolar polarizations. The real and the imaginary parts of the impedance are well fitted to equivalent circuit models. At high temperatures, Z″_max varies from 0.03 × 10⁶ to 4.9 × 10⁶ Ω when the TiO₂ doping concentration increases from 1 to 7 wt%. From the obtained results, the secondary phase ZnTiO₃ plays an important role in the electrical properties.     

Effect of Processing Conditions on Drying Kinetics and Particle Microstructure of Carrot

The drying of carrot particles (6 mm × 6 mm × 12 mm) was studied in a tunnel dryer; a vacuum-freeze dryer, either with or without infrared radiation; a pulsed fluidized-bed dryer assisted by microwave radiation; and combinations of these methods. The effect of two freezing rates (quick freezing in liquid nitrogen and slow freezing in a household freezer) was also studied.

The drying kinetics for these drying methods were determined and modeled, and the dried products were subjected to texture (hardness), color, and rehydration analysis, as well as 2D and 3D image analysis of pictures from scanning electron microscope.

The combination of freeze drying with other dehydration techniques reduces the drying time by 6–70%, although, in general, the structural damage increases with respect to freeze drying alone. The hybrid drying systems did not show significant differences in drying times either for quick- or slow-frozen samples. The combination of freeze drying followed by conventional drying reduces the drying time between 23 and 40% on average.

The Page empirical model represents adequately the entire drying process for combined methods, with specific parameters for each drying zone. The values of effective diffusivity calculated with the simplified constant diffusivity model agree with those reported in the literature.     

The Formation of a 12-Hydroxystearic Acid/Vegetable Oil Organogel Under Shear and Thermal Fields

External laminar oscillatory shear applied during crystallization in combination with different temperature fields was used to modify the microstructure and physical properties of edible oil organogels. Crystallization at a high cooling rate (30 °C/min) resulted in a spherulitic microstructure with a higher oil-binding capacity, lower storage modulus and lower yield stress compared with a material (with a fibrillar microstructure) crystallized at a slow cooling rate (1 °C/min). The application of an oscillatory shear resulted in the formation of novel microstructures depending on the cooling regime used. The application of an oscillatory shear (strain > 500 % and frequency = 1 Hz) resulted in the thickening of fibers observed in the slow-cooled material and an increased incidence of spherulite nucleation in the rapidly cooled material. Increasing the frequency of the oscillatory shear applied did not change the microstructure for the slow-cooled gel but further increased the incidence of nucleation for the rapidly cooled gel. The application of controlled-strain oscillatory shear to the crystallizing gel at either cooling rates resulted in an oily and very soft, paste-like material. This material had a lower storage modulus and poorer oil-binding capacity compared with the same gel crystallized statically. Reduction of the oscillatory strain from a maximum of 1500 to 500 % moderately mitigated the loss of mechanical properties and oil-binding capacity although these properties were in no way comparable to those obtained from static crystallization. The study shows that the application of oscillatory shear and different cooling regimes can be used to tailor a crystalline organogel. However, the application of continuous shear must be done with care as application of excessive shear can result in a complete breakdown in gel structure and large amounts of oil loss.     

Minor Components in Canola Oil and Effects of Refining on These Constituents: A Review

Crude canola oil is composed mainly of triacylglycerols but contains considerable amounts of desirable and undesirable minor components. Crude canola oil is refined in order to remove undesirable minor compounds that make this oil unusable in food products. However, refining can also cause the removal of desirable health-promoting minor components from the oil. The first section of this review describes the chemical composition of canola oil, followed by a brief introduction to the effects of minor components on canola oil quality and stability. Following a review of traditional canola oil refining methods, the effects of individual refining stages on the removal of both desirable and undesirable components from canola oil are presented and contrasted with other common vegetable oils.     

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.     

Hydrolytic degradation of nanocomposites based on poly(l‐lactic acid) and layered double hydroxides modified with a model drug

Hydrolytic degradation of a nanocomposite of poly(L‐lactic acid), PLA, and a layered double hydroxide (LDH) modified with the drug 4‐biphenyl acetic acid (Bph) has been studied. PLA/LDH‐Bph nanocomposite was prepared by solvent casting with 5 wt % of drug modified LDH and the hydrolytic degradation was carried out in a PBS solution at pH 7.2 and 37 °C. Neat PLA with 5 wt % 4‐biphenyl acetic acid was studied as reference material (PLA/Bph). The materials were studied by WAXS, TEM, TGA, DSC, SEM, FTIR, SEC and contact angle measurements. For PLA/Bph, an acid catalytic effect, caused by the drug, accelerates PLA mass loss. However, for PLA/LDH‐Bph, the presence of LDH produces a barrier effect that initially reduces the diffusion of the oligomers produced during hydrolytic degradation. DSC results demonstrate that Bph induces faster PLA crystallization and this effect is reduced in PLA/LDH‐Bph nanocomposites because of their lower drug content. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43648.