Degradation kinetics of epoxidized soybean oil composites filled with sisal fiber

Epoxidized soybean oil (ESO) composites were cured with methyl tetrahydrophthalic anhydride (MTHPA) and 2,4,6-tris(dimethylaminomethyl)phenol (DEH 35) as a catalyst, sisal fibers were added at 10% and 30% of percent per weight. Composites curing was monitored using Fourier transform infrared spectroscopy, whereas the thermal stability and the degradation kinetics were investigated using thermogravimetry (TG). ESO/MTHPA/DEH35/S10 and ESO/MTHPA/DEH35/S30 composites displayed curing temperatures approximately 100°C lower related to ESO/MTHPA/DEH35, as well as higher degree of conversion. Sisal addition improved the thermal stability, shifting the weight loss shifting the weight loss onset to higher temperature (from 82 to 120°C). Thermal degradation energy $$ was determined using Friedman, Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall models. Sisal significantly increased $$, especially in the intermediate phase (α = 0.2 and 0.8). The degradation kinetics was investigated by TG, and the degradation mechanisms modeled using Kamal-Sourour, Sestack-Berggren, and 1st order (F1), showed excellent fit, with R² > 0.99. Acquired results demonstrate that sisal fiber addition benefited the curing process and increased the thermal stability of ESO composites.     

Strength Degradation and Failure Mechanisms of Electron-Beam Physical-Vapor-Deposited Thermal Barrier Coatings

Failure mechanisms were determined for electron-beam physical-vapor-deposited thermal barrier coating (TBC) systems from the degradation of mechanical properties and microstructural changes in a furnace cycle test. Bond strength degradation for TBCs resulted from the initiation and growth of interfacial delamination defects between the yttria-stabilized zirconia topcoat and the thermally grown alumina (TGO). It is proposed that defects started from concave depressions in the bondcoat surface created by the grit-blast-cleaning process and that defect growth was driven by the reduction in compressive strain in the TGO as the alumina deformed into and displaced the bondcoat during the cooling cycles. Inclusion of yttrium in the substrate resulted in a doubling of the furnace cycle life of the TBCs because of enhanced fracture toughness of the TGO-bondcoat interface.     

Single-phase and binary phase nanogranular ferrites for magnetic hyperthermia application

The study demonstrates the performance of heating efficiency in single-phase and binary phase spinel ferrite nanosystems. Ferrimagnetic cobalt ferrite (CoFe₂O₄) (CFO) and superparamagnetic copper ferrite/copper oxide (CuFe₂O₄/CuO) (CuF) nanosystems of different particle sizes were synthesized through a microwave-assisted coprecipitation method. The heating behavior was observed in range of both field amplitudes (8-24 kA/m at 516 kHz) and frequencies (325-973 kHz at 12 kA/m). The heating efficiency was analyzed and compared by means of particle size, magnetization, effective anisotropy constant, and Néel relaxation mechanism. Indeed, the heating rate was maximized in larger ferrite particles with low effective anisotropy constant. Moreover, though the magnetization and effective anisotropy constant of single-phase CoFe₂O₄ nanoparticles were higher, the binary phase CuFe₂O₄/CuO nanosystems of similar crystallite size (28 nm) exhibited superior heating efficiency (4.21°C/s). For a field amplitude and frequency of 24 kA/m and 516 kHz, the heating rate of CuF and CFO ferrites with different crystallite sizes decreased in the order of 4.21 > 2.14 > 0.58 > 0.52°C/s for 29 nm > 25 nm > 12 nm > 15 nm, respectively. The results emphasize that binary phase ferrite nanoparticles are better thermoseeds than the single-phase ferrites for the magnetic hyperthermia application.     

Activity of α‐Aminoadipate Reductase Depends on the N‐Terminally Extending Domain

L ‐α‐Aminoadipic acid reductases catalyze the ATP‐ and NADPH‐dependent reduction of L ‐α‐aminoadipic acid to the corresponding 6‐semialdehyde during fungal L ‐lysine biosynthesis. These reductases resemble peptide synthetases with regard to their multidomain composition but feature a unique domain of elusive function—now referred to as an adenylation activating (ADA) domain—that extends the reductase N‐terminally. Truncated enzymes based on NPS3, the L ‐α‐aminoadipic acid reductase of the basidiomycete Ceriporiopsis subvermispora, lacking the ADA domain either partially or entirely were tested for activity in vitro, together with an ADA‐adenylation didomain and the ADA domainless adenylation domain. We provide evidence that the ADA domain is required for substrate adenylation: that is, the initial step of the catalytic turnover. Our biochemical data are supported by in silico modeling that identified the ADA domain as a partial peptide synthetase condensation domain.     

Comparison of 10,11‐Dehydrocurvularin Polyketide Synthases from Alternaria cinerariae and Aspergillus terreus Highlights Key Structural Motifs

Iterative type I polyketide synthases (PKSs) from fungi are multifunctional enzymes that use their active sites repeatedly in a highly ordered sequence to assemble complex natural products. A phytotoxic macrolide with anticancer properties, 10,11‐dehydrocurvularin (DHC), is produced by cooperation of a highly reducing (HR) iterative PKS and a non‐reducing (NR) iterative PKS. We have identified the DHC gene cluster in Alternaria cinerariae, heterologously expressed the active HR PKS (Dhc3) and NR PKS (Dhc5) in yeast, and compared them to corresponding proteins that make DHC in Aspergillus terreus. Phylogenetic analysis and homology modeling of these enzymes identified variable surfaces and conserved motifs that are implicated in product formation.     

Produktschonende Betriebs‐ und Designparameter von Wärmeübertragern für temperaturempfindliche Prozessströme

To allow the calculation of product degradation rates as extension to the currently used thermotechnical design calculations for heat exchangers, a volume‐related, reaction‐kinetic approach was developed. Therefore, a model system was selected and the product protection design parameters were determined for a lab‐scale heat exchanger with the help of simulations. The validation was demonstrated in an experiment. Additionally, the product‐protecting operating parameters for the heat exchanger were calculated with a technically relevant set of compounds.     

Metformin Reduces Lipogenesis Markers in Obese Mice Fed a Low-Carbohydrate and High-Fat Diet

Lipogenesis is the process by which fatty acids are synthesized. In metabolic syndrome, an insulin resistant state along with high plasma levels of free fatty acids (FFA) and hyperglycemia may contribute to the lipogenic process. The aim of the present study was to investigate the effects of oral administration of metformin on the expression of lipogenic genes and glycemic profile in mice fed with low‐carbohydrate high‐fat diet by evaluating their metabolic profile. SWISS male mice were divided into 4 groups (N = 7) that were fed with standard (ST), standard plus metformin (ST + MET), low‐carbohydrate high‐fat diet (LCHFD) and low‐carbohydrate high‐fat diet plus metformin (LCHFD + MET) (100 mg kg^?1 diet) diets respectively. Food intake, body weight and blood parameters, such as glucose tolerance, insulin sensitivity, glucose, HDL‐c, total cholesterol, triglycerides, ASL and ALT levels were assessed. Histological analyses were performed on hematoxylin and eosin‐stained epididymal adipose tissue histological specimens. The expression levels of peroxisome proliferator‐activated receptor (PPARγ), sterol regulatory element‐binding protein 1 (SREBP1), fatty acid synthase (FAS) and acetyl‐CoA carboxylase (ACC), were assessed by RT‐PCR. This study showed that metformin decreased adipocyte area, body weight and food consumption in obese animals when compared to the standard group. Furthermore, the expression of lipogenic markers in adipose tissue were diminished in obese animals treated with metformin. This data showed that oral administration of metformin improved glucose and lipid metabolic parameters in white adipose tissue by reducing the expression of lipogenesis markers, suggesting an important clinical application of MET in treating obesity‐related diseases in metabolic syndrome.     

Polymeric Hollow‐Fiber Bundles as Immersed Heat Exchangers

Plastic immersed heat exchangers are used in various applications where chemically neutral and noncorrosive equipment is required. Their potential competitors, namely, polymeric hollow‐fiber bundles, were investigated. Three different fiber bundles were tested as immersed coolers of a hot reservoir. Two types of polypropylene hollow fibers with various outside diameters were employed. Fibers were twisted with different curvature to achieve better distribution and improve natural convection on their outer surface. Calculation by experimental results was compared with the equation for natural convection across the horizontal cylinder, which overestimates heat transfer coefficients and can be applied for only rough estimation. Experimentally achieved pressure drops agreed well with theoretical prediction for laminar flow.     

Remendable polymers via reversible Diels–Alder cycloaddition of anthracene‐containing copolymers with fullerenes

Poly(lauryl methacrylate)s with anthracene moieties in the side chain were converted with C₆₀‐fullerene and phenyl‐C₆₁‐butyric acid methyl ester (PCBM), resulting in new remendable (self‐healing) polymeric materials. The utilization of differently substituted anthracene monomers enabled the tuning of the reactivity and the resulting mechanical properties. Copolymers with different contents of the anthracene moieties were synthesized and characterized using size exclusion chromatography, ¹H nuclear magnetic resonance (NMR) spectroscopy as well as differential scanning calorimetry (DSC). ¹H NMR spectroscopic studies were utilized in order to investigate the reversibility of the Diels–Alder reaction between copolymers with C₆₀‐fullerene and PCBM, respectively, in solution. In order to investigate the conversion of the polymers with C₆₀‐fullerene and PCBM in bulk, additionally, DSC, nanoindentation, rheology, atomic force microscopy (AFM), 3D microscopy, simultaneous thermal analysis (STA) and FT‐Raman investigations were performed. The fullerene‐containing copolymers could be healed in a temperature range of 40–80 °C. Consequently, a new generation of low temperature remendable polymers could be established. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45916.