Modification of the oxygen storage capacity of CeO2–ZrO2 mixed oxides after redox cycling aging

High surface area CeO₂–ZrO₂ mixed oxides were treated at 900–950°C either under wet air or under successive reducing and oxidizing atmospheres in order to study the evolution of the oxygen storage capacity (OSC) of these solids after different aging treatments. Several complementary methods were used to characterize the redox behavior: temperature programmed reduction (TPR) by H₂, TPO, magnetic susceptibility measurements to obtain the Ce³⁺ content, FT-IR spectroscopy of adsorbed methanol and a method to compare the oxygen buffering capacity (OBC) of the oxides.

All the results confirm that the mixed oxides exhibit better redox properties than pure ceria, particularly after aging. The enhancement in the OSC at moderate temperature has to be related to a deeper penetration of the reduction process from the surface into the under-layers. Redox cycling aging promotes the reduction at low temperature of all the mixed oxides, the improvement being much more important for low surface area aged samples. The magnitude of this effect does not depend on the BET surface areas which have similar values after cycling. This underlines the critical influence that the preparation and activation procedure have on the final OSC behaviors of the ceria–zirconia mixed oxides.     

Syntheses of Chiral Menthyl and Neomenthyl Sulfides,sulfoxides and sulfones

Attempts to synthesize stereospecifically menthanethiol ( 2 ) and menthyl thiocyanate ( 3 ) from suitable electrophilic neomenthyl substrates ( 4a–c ), and a variety of sulfur nucleophiles failed or predominantly led to β-elimination products. Almost quantitative yields of mixtures of 2 and its 3-epimer ( 8 ) were obtained by reductive cleavage of (−)-3-menthone ethylene dithioacetal ( 7 ), but stereoselectivity was low (ratio of 2/8 , 41:59) and the mixture could not be resolved. Recrystallization and subsequent oxidation of the dinitrophenyl sulfides of 2 and 8 allowed the isolation of the dinitrophenyl menthyl and neomenthyl sulfoxides ( 12 and 13 , respectively), and an irresolvable mixture of the sulfones 14 and 15 .     

Extracting rules from a (fuzzy/crisp) recurrent neural network using a self‐organizing map

Although the extraction of symbolic knowledge from trained feedforward neural networks has been widely studied, research in recurrent neural networks (RNN) has been more neglected, even though it performs better in areas such as control, speech recognition, time series prediction, etc. Nowadays, a subject of particular interest is (crisp/fuzzy) grammatical inference, in which the application of these neural networks has proven to be suitable. In this paper, we present a method using a self‐organizing map (SOM) for extracting knowledge from a recurrent neural network able to infer a (crisp/fuzzy) regular language. Identification of this language is done only from a (crisp/fuzzy) example set of the language. © 2000 John Wiley & Sons, Inc.     

Defects and Disorder in Covalent Organic Frameworks for Advanced Applications

Crystalline porous organic polymers (CPPs) or covalent organic frameworks (COFs), are composed by light elements linked by covalent bonds. Despite the remarkable progress attained, there are still bottlenecks limiting further development, some of them related to the presence of defects during their synthesis as well as in-depth understanding of structure of active centers and/or details of the reaction mechanism. Indeed, very often the proposed structures are far from reality because defects and disorders have not been considered. The present review provides an illustrative overview of “defects and disorder in COFs”. These defects include those not only generated during the synthesis and manipulation of COFs, but also lack of crystallinity, stacking disorder and network vacancies. The review starts giving general remarks on organic COFs and their synthetic methods, followed by different methods to play and manage defects, how to minimize them or how to take advantage of them to gain new properties and applications. Selected characterization techniques to quantify defective structures and active sites in COFs are also presented. Finally, the challenges and future opportunities in the field have been summarized in the last section.     

An exploratory study of child-centered play therapy with aggressive children.

Children exhibiting aggressive problem behaviors typically reach a peak of aggressive acts at an early age, providing evidence that early intervention for aggression is needed. Child-centered play therapy (CCPT) is 1 intervention that offers the child an environment in which aggression can be expressed and empathically responded to by a play therapist. Forty-one elementary school age children were assigned to a CCPT condition or a wait-list control group condition. Children who participated in 14 sessions of CCPT showed a moderate decrease in aggressive behaviors over children in the control group, according to effect sizes as reported by parents (N = 32). Teachers reported that both groups significantly improved over time (N = 41). Post hoc analysis revealed that children assigned to CCPT decreased aggressive behaviors statistically significantly and children assigned to control group demonstrated no statistically significant difference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Formulation and Characterization of Taxifolin‐Loaded Lipid Nanovesicles (Liposomes,Niosomes, and Transfersomes) for Beverage Fortification

In this study, nanovesicles such as transfersomes, niosomes, and liposomes prepared by an ethanol injection method (EIM) (EIM) and formulated with soybean lecithin, Tween 80, Span 60, and cholesterol, are used to improve the bioavailability of taxifolin, a natural antioxidant with beneficial properties for health and food preservation. Morphology, stability, and the in‐vitro release of the optimal formulations are fully examined. The obtained results indicate that taxifolin‐loaded nanovesicles present sizes ranging between 98 and 215 nm along with a narrow size distribution (polydispersity index less than 0.250). The zeta potential of nanovesicles is negative and in the range of ?20.40 to ?32.20 mV. The optimal formulations with the maximum encapsulation efficiency (72–75%) are the transfersomes formulated with lecithin and Tween 80 in the presence and absence of cholesterol. Additionally, in vitro release behavior of nanovesicles shows low taxifolin released (3.68–10.13%) at intestinal conditions, whereas more than 90% of taxifolin is released in gastrointestinal conditions. The compatibility between taxifolin and nanovesicles components is confirmed by FTIR. Transmission electron microscopy demonstrates spherical shaped particles around 200 nm. Backscattering profiles variations show the potential application of taxifolin nanovesicles for producing fortified apple juice with excellent physical stability. Practical Applications: Taxifolin is a flavanonol, which fulfills a particular task in preserving stable functions of the circulatory system owing to its special antioxidant ability and biological activity. Nevertheless, its low bioavailability is a salient drawback for biomedical and food applications. Thus, the current study is conducted to encapsulate taxifolin in nanovesicles (such as liposome, niosome, transfersome) by EIM to improve its bioavailability. Nanocarriers with relatively decent physical stability and high encapsulation efficiency can be brought about through Tween 80, soybean lecithin, and in the presence and absence of cholesterol as stabilizer which ensures the successful delivery of taxifolin to food formats such as beverages.     

Nitrous oxide formation in low temperature selective catalytic reduction of nitrogen oxides with V2O5/TiO2 catalysts

Nitric oxide and nitric dioxide compounds (NO_x) present in stack gases from nitric acid plants are usually eliminated by selective catalytic reduction (SCR) with ammonia. In this process, small quantities of nitrous oxide (N₂O) are produced. This undesirable molecule has a high greenhouse gas potential and a long lifetime in the atmosphere, where it can contribute to stratospheric ozone depletion. The influence of catalyst composition and some operating variables were evaluated in terms of N₂O formation, using V₂O₅/TiO₂ catalysts. High vanadia catalyst loading, nitric oxide inlet concentration and reaction temperature increase the generation of this undesirable compound. The results suggest that adsorbed ammonia not only reacts with NO via SCR, but also with small quantities of oxygen activated by the presence of NO. The mechanism proposed for N₂O generation at low temperature is based on the formation of surface V–ON species which may be produced by the partial oxidation of dissociatively adsorbed ammonia species with NO + O₂ (eventually NO₂). When these active sites are in close proximity they can interact to form an N₂O molecule. This mechanism seems to be affected by changes in the active site density produced by increasing the catalyst vanadia loading.     

Carbon formation and its influence on ethanol steam reforming over Ni/Al2O3 catalysts

Ethanol steam reforming was studied over Ni/Al₂O₃ catalysts. The effect of support (- and γ-Al₂O₃), metal loading and a comparison between conventional H₂ reduction with an activation method employing a CH₄/O₂ mixture was investigated. The properties of catalysts were studied by N₂ physisorption, X-ray diffraction (XRD) and temperature programmed reduction (TPR). After activity tests, the catalysts were analyzed by scanning electron microscopy (SEM) and thermogravimetric analysis (TG/DTA). Ni supported on γ-Al₂O₃ was more active for H₂ production than the catalyst supported on -Al₂O₃. Metal loading did not affect the catalytic performance. The alternative activation method with CH₄/O₂ mixture affected differently the activity and stability of the Ni/γ-Al₂O₃ and the Ni/-Al₂O₃ catalyst. This activation method increased significantly the stability of Ni/-Al₂O₃ compared to H₂ reduction. SEM and TG/DTA analysis indicate the formation of filamentous carbon during the CH₄/O₂ activation step, which is associated with the increasing catalyst activity and stability. The effect of temperature on the type of carbon formed was investigated; indicating that filamentous coke increased activity while encapsulating coke promoted deactivation. A discussion about carbon formation and the influence on the activity is presented.     

Synthesis and evaluation of compatibilizer based on interpenetrating polymer networks (IPN) for PET/LDPE blends

The present work considers the evaluation of recycled polymers, which are generally incompatible and are degraded during recycling with fatal consequences to their thermal and mechanical properties. Regarding this subject, the synthesis of a new compatibilizer in network form was carried out in order to counter such incompatibility. In this sense, low density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) were compatibilized via the implementation of an interpenetrating polymer network (IPN), which was specifically synthesized to possess chemical groups that are akin to both plastics, PET and LDPE. The effects of the relative amount of poly(acrylic acid) (PAA) in the compatibilizer and the amount in the blends of PET/LDPE were evaluated. The results show that mechanical properties and interfacial adhesion of PET/LDPE blends were modified and improved with the addition of the synthesized compatibilizer compared with a commercial compatibilizer (polyethylene grafted with maleic anhydride, PE‐g‐AA). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43704.     

Lipase-Catalyzed Production of Biodiesel by Hydrolysis of Waste Cooking Oil Followed by Esterification of Free Fatty Acids

Biodiesel is conventionally produced by alkaline‐catalyzed transesterification, which requires high‐purity oils. However, low‐quality oils can be used as feedstocks for the production of biodiesel by enzyme‐catalyzed reactions. The use of enzymes has several advantages, such as the absence of saponification side reactions, production of high‐purity glycerol co‐product, and low‐cost downstream processing. In this work, biodiesel was produced from lipase‐catalyzed hydrolysis of waste cooking oil (WCO) followed by esterification of the hydrolyzed WCO (HWCO). The hydrolysis of acylglycerols was carried out at 30 °C in salt‐free water (WCO/water ratio of 1:4, v/v) and the esterification of HWCO was carried out at 40 °C with ethanol in a solvent‐free medium (HWCO/ethanol molar ratio of 1:7). The hydrolysis and esterification steps were carried out using immobilized Thermomyces lanuginosus lipase (TLL/WCO ratio of 1:5.6, w/w) and immobilized Candida antarctica lipase B (10 wt%, CALB/HWCO) as biocatalysts, respectively. The hydrolysis of acylglycerols was almost complete after 12 h (ca. 94 %), and in the esterification step, the conversion was around 90 % after 6 h. The purified biodiesel had 91.8 wt% of fatty acid ethyl esters, 0.53 wt% of acylglycerols, 0.003 wt% of free glycerol, viscosity of 4.59 cP, and acid value of 10.88 mg KOH/g. Reuse hydrolysis and esterification assays showed that the immobilized enzymes could be recycled five times in 10‐h batches, under the conditions described above. TLL was greatly inactivated under the assay conditions, whereas CALB remained fully active. The results showed that WCO is a promising feedstock for use in the production of biodiesel.