Combination of nuclear magnetic resonance spectroscopy and nonlinear methods to analyze the copolymerization of phosphonic acid derivatives

We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The ¹H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of r_HEMA = 1.83; r_ECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256.     

Gold Stabilized with Iridium on Ceria–Niobia Catalyst: Activity and Stability for CO Oxidation

Topics in Catalysis - Monometallic gold and iridium, and bimetallic gold–iridium on ceria–niobia (Nb2O5–CeO2) catalysts were synthesized by deposition–precipitation with...     

Steric and electronic effects on mesophase stability of segmented liquid crystalline polymers with arylazomethine pendant groups

Summary The kinetics of DL-lactide polymerization was studied in CH₂Cl₂ at 25°C and in toluene at 70°C with HAPENAlOMe, a new Schiff's base complex derived from 2-hydroxyacetophenone and ethylenediamine. A higher polymerization rate is observed with this initiator as compared to other previously reported Al-alkoxides complexes. The polymerization with HAPENAlOMe is also shown to be a living process in both solvents. Moreover, the polymerization proceeds to quite high conversion without significant occurrence of transesterification reactions as confirmed from ¹³C NMR and SEC analysis. Received: 4 October 1999/Accepted: 6 December 1999     

Phenol degradation by Fenton's process using catalytic in situ generated hydrogen peroxide

The recent reported pathway using oxygen and formic acid at ambient conditions has been utilized to generate hydrogen peroxide in situ for the degradation of phenol. An alumina supported palladium catalyst prepared via impregnation was used for this purpose. Almost full destruction of phenol was carried out within 6 h corresponding to the termination of 100 mM formic acid at the same time. In addition, a significant mineralization (60%) was attained. A simulated conventional Fenton process (CFP) using continuous addition of 300 ppm H₂O₂ displayed maximum 48% mineralization. Study of different doses of formic acid showed that decreasing the initial concentration of formic acid caused faster destruction of phenol and its toxic intermediates. The catalytic in situ generation of hydrogen peroxide system demonstrated interesting ability to oxidize phenol without the addition of Fenton's catalyst (ferrous ion). Lower Pd content catalysts (Pd1/Al and Pd0.5/Al) despite of producing higher hydrogen peroxide amount for bulk purposes, did not reach the same efficiency as the Pd5/Al catalyst in phenol degradation. The later catalyst showed a remarkable repeatability so that more than 90% phenol degradation along with 57% mineralization was attained by the used catalyst after twice recovery. Higher temperature (45 °C) gave rise to faster degradation of phenol resulting to almost the same mineralization degree as obtained at ambient temperature. Meanwhile, Pd leaching studied by atomic adsorption proved excellent stability of the catalysts.     

Coupled simulation of the flue gas and process gas side of a steam cracker convection section

A coupled simulation of the flue gas and process gas side of the convection section of a steam cracker is performed, making use of the CFD software package Fluent. A detailed overview of the operating mode of the different heat exchangers suspended in the convection section is obtained. The asymmetric inlet flow field of the flue gas in the convection section, and the radiation from the convection section walls leads to large differences in outlet temperatures of the tubes located in the same row. The flow fields and temperature fields in the tubes of a single heat exchanger differ significantly with e.g., outlet temperatures of the hydrocarbon‐steam mixture ranging from 820 K to 852 K. Moreover, the simulations reveal the presence of hot spots on the lowest tube row, possibly causing fouling. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Catalytic Epoxidation and Sulfoxidation Activity of a Dioxomolybdenum(VI) Complex Bearing a Chiral Tetradentate Oxazoline Ligand

A dioxomolybdenum(vi) complex bearing a tetradentate anionic N,O oxazoline ligand with four stereocenters has been studied as a catalyst in the liquid-phase epoxidation of 17 different aliphatic and aromatic olefins (including prochiral, racemate or pure enantiomers) using tert-butyl hydroperoxide as the oxidant. Epoxide selectivities of up to 100% and variable epoxide yields (3–100% within 24 h) were obtained. Although the complex generally exhibited low or no chiral induction ability, diastereoselectivity was significant in some cases (in the reaction of limonene, for example). Kinetic studies and recycling tests with the substrates cis-cyclooctene and trans-β-methylstyrene showed that the catalyst is stable and reusable, and recycling is facilitated by immobilization of the complex in a room temperature ionic liquid. Preliminary results show that the complex may have a broad substrate scope, not only for olefin epoxidation, but also for the dehydrogenation of alcohols to carbonyl compounds and the sulfoxidation of sulfides to sulfoxides.     

Characterization of Oil Precipitate and Oil Extracted from Condensed Corn Distillers Solubles

Oil extracted from condensed corn distillers solubles (CCDS) can form a semi-solid and waxy precipitate at the bottom of containers during storage. CCDS is a good source to recover oil, and such oil can be converted to biodiesel. Precipitate formation in the extracted oil is mainly a physical stability problem, but it may become a performance problem for biodiesel. The objective of the present work was to determine the composition of the CCDS oil precipitate and also determine if valuable phytosterols were present in high concentration. The free fatty acid (FFA) content was very high, 35.7%, and fatty acid composition of the FFA fraction was predominantly palmitic acid, 70.3%. The solid appearance was mainly due to a high percentage of high-melting point free saturated fatty acid. The total unsaponifiable matter was 2.0%, and total phytosterol content was 8.6 mg/g of CCDS oil precipitate. Therefore, CCDS oil precipitate is a not an enriched source of phytosterols compared to total sterols present in crude corn oil (15.6 mg/g oil). The wax content was high, 2.5 mg/g of CCDS oil precipitate compared to 0.5 mg/g of crude corn oil. CCDS oil that is uncentrifugable but polar solvent extractable (trapped oil fraction) was also characterized and found to contain more polar lipids than those in the free oil fraction (centrifugable oil).     

Drug-Induced Lysosomal Impairment Is Associated with the Release of Extracellular Vesicles Carrying Autophagy Markers

Amiodarone is a cationic amphiphilic drug used as an antiarrhythmic agent. It induces phospholipidosis, i.e., the accumulation of phospholipids within organelles of the endosomal–lysosomal system. Extracellular vesicles (EVs) are membrane-enclosed structures released by any type of cell and retrieved in every fluid of the body. EVs have been initially identified as a system to dispose cell waste, but they are also considered to be an additional manner to transmit intercellular signals. To understand the role of EVs in drug-induced phospholipidosis, we investigated EVs release in amiodarone-treated HEK-293 cells engineered to produce fluorescently labelled EVs. We observed that amiodarone induces the release of a higher number of EVs, mostly of a large/medium size. EVs released upon amiodarone treatment do not display significant morphological changes or altered size distribution, but they show a dose-dependent increase in autophagy associated markers, indicating a higher release of EVs with an autophagosome-like phenotype. Large/medium EVs also show a higher content of phospholipids. Drugs inducing lysosomal impairment such as chloroquine and bafilomycin A1 similarly prompt a higher release of EVs enriched in autophagy markers. This result suggests a mechanism associated with amiodarone-induced lysosomal impairment more than a connection with the accumulation of specific undigested substrates. Moreover, the implementation of the lysosomal function by overexpressing TFEB, a master gene regulator of lysosomal biogenesis, prevents the amiodarone-induced release of EVs, suggesting that this could be a feasible target to attenuate drug-induced abnormalities.     

Antifungal Peptides and Proteins to Control Toxigenic Fungi and Mycotoxin Biosynthesis

The global challenge to prevent fungal spoilage and mycotoxin contamination on food and feed requires the development of new antifungal strategies. Antimicrobial peptides and proteins (AMPs) with antifungal activity are gaining much interest as natural antifungal compounds due to their properties such as structure diversity and function, antifungal spectrum, mechanism of action, high stability and the availability of biotechnological production methods. Given their multistep mode of action, the development of fungal resistance to AMPs is presumed to be slow or delayed compared to conventional fungicides. Interestingly, AMPs also accomplish important biological functions other than antifungal activity, including anti-mycotoxin biosynthesis activity, which opens novel aspects for their future use in agriculture and food industry to fight mycotoxin contamination. AMPs can reach intracellular targets and exert their activity by mechanisms other than membrane permeabilization. The mechanisms through which AMPs affect mycotoxin production are varied and complex, ranging from oxidative stress to specific inhibition of enzymatic components of mycotoxin biosynthetic pathways. This review presents natural and synthetic antifungal AMPs from different origins which are effective against mycotoxin-producing fungi, and aims at summarizing current knowledge concerning their additional effects on mycotoxin biosynthesis. Antifungal AMPs properties and mechanisms of action are also discussed.