Synthesis of Polystyrene/Hydrophobic SiO2 Composite Particles via Oil‐in‐Water Pickering Emulsion Polymerization

The aim of this work is to present a facile Pickering emulsion polymerization method for the synthesis of submicron polystyrene/SiO₂ core/shell composite particles. The commercial hydrophobic SiO₂ nanoparticles were used as stabilizing agent for creating a stable oil‐in‐water emulsion. Although the adsorption of hydrophobic SiO₂ nanoparticles in the emulsion system was unfavorable in terms of thermodynamics, by ultrasound treatment, self‐assembly of hydrophobic SiO₂ nanoparticles effectively stabilized oil‐in‐water Pickering emulsions during polymerization. Using 3 wt.% SiO₂ nanoparticles (based on styrene monomer) and 1:10 volume ratio of styrene monomer:water, the composite particles having average size of 790 nm and relatively narrow particles distribution were produced. With decreasing the volume ratio, smaller composite particles were created. Results from scanning electron microscope revealed that SiO₂ nanoparticles were located exclusively at the surface of the polystyrene latex particles. The SiO₂ content, determined by thermogravimetric analysis, was 12.6 wt.% in the composite particles. The route reported here may be used for the preparation of other composite nanostructures. POLYM. ENG. SCI., 59:E195–E199, 2019. © 2018 Society of Plastics Engineers     

Adaptive iterative learning control for robot manipulators

In this paper, we propose some adaptive iterative learning control (ILC) schemes for trajectory tracking of rigid robot manipulators, with unknown parameters, performing repetitive tasks. The proposed control schemes are based upon the use of a proportional-derivative (PD) feedback structure, for which an iterative term is added to cope with the unknown parameters and disturbances. The control design is very simple in the sense that the only requirement on the PD and learning gains is the positive definiteness condition and the bounds of the robot parameters are not needed. In contrast to classical ILC schemes where the number of iterative variables is generally equal to the number of control inputs, the second controller proposed in this paper uses just two iterative variables, which is an interesting fact from a practical point of view since it contributes considerably to memory space saving in real-time implementations. We also show that it is possible to use a single iterative variable in the control scheme if some bounds of the system parameters are known. Furthermore, the resetting condition is relaxed to a certain extent for a certain class of reference trajectories. Finally, simulation results are provided to illustrate the effectiveness of the proposed controllers.     

Optimal control of electromagnetic wave displacement with an unknown velocity of propagation

The aim of this paper is to control an electromagnetic wave that penetrates in a medium with some missing information about its physical properties. The missing value of wave velocity of propagation leads us to use averaged control notion which is recently introduced by E. Zuazua, also the boundary Dirichlet condition is unknown which requires using the notion of no-regret control introduced by J. L. Lions. In this work, we combine these two techniques where we introduce the notion of averaged no-regret control to solve our optimal control problem with missing data. The averaged no-regret control will be characterised by an optimality system.     

Velocity‐free attitude stabilization with inertial vector measurements

This paper deals with the attitude stabilization problem of a rigid body, where neither the angular velocity nor the attitude is used in the feedback; only body‐referenced vector measurements are needed. The proposed control scheme is based on an angular velocity observer‐like system relying solely on vector measurements. The proposed controller ensures almost global asymptotic stability and provides some interesting performance properties through an appropriate tuning of the control gains. The performance and effectiveness of the proposed control scheme are illustrated via simulation results where the control gains are adjusted using a nonlinear optimization. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of frying on the fatty acid composition in farmed and wild gilthead sea bream (Sparus aurata)

The effects of frying in soybean (FWSO) and olive oils (FWOO) on the fatty acid composition of farmed and wild gilthead sea bream Sparus aurata were evaluated. The fat content increased with both frying treatments. However, after FWOO the moisture content of the fish was reduced to a greater extent than that in fish FWSO. The concentration of saturated fatty acids (SFA) decreased significantly during both frying processes ( P  < 0.01). However, the concentration of monounsaturated fatty acids (MUFA) increased significantly in fish fried in olive oil ( P  < 0.01). The fried fish contained a higher level of n-6 polyunsaturated fatty acids (PUFA) and a lower level of n-3 PUFA compared to raw fish. The n-3/n-6 ratio decreased in wild fish FWSO and FWOO from 0.94 ± 0.08 to 0.15 ± 0.01 and 0.15 ± 0.02, respectively. In farmed bream, the ratios decreased from 2.51 ± 0.03 to 0.18 ± 0.03 and 0.36 ± 0.01, respectively. The concentration of trans fatty acids decreased significantly in both fish types after frying ( P  < 0.05). The frying process widely affected the EPA and DHA content, limiting the positive effects of n-3 PUFA.     

Partial oxidation of methane on co-precipitated Ni–Mg/Al catalysts modified with copper or iron

Methane transformation to hydrogen and synthesis gas (CO + H₂) by heterogenous catalysts can play an important role to secure the supply of energy, chemicals and fuels in the future. Methane is the main constituent of natural gas and biogas and it is also found in crystalline hydrates at the continental slopes of many oceans. In view of this vast reserves and resources, the use of methane as chemical feedstock has to be intensified. In this present work, (NiMg)Al catalysts doped with Fe or Cu, prepared by co-precipitation method and characterized by different techniques, were studied in the partial oxidation of methane (T_reaction = 750 °C, CH₄/O₂ ratio = 2). The effect of catalyst composition and pre-treatment conditions of these catalysts were investigated. Also, these catalysts show a very high activity and selectivity in the partial oxidation reaction, which depends on the conditions of catalysts preparation. The obtained results indicated increasing of activity and selectivity with decreasing calcination temperature and increasing nickel and aluminium contents in the catalysts composition. The solid doped with iron constituted the best catalyst for the total oxidation of methane and for the water–gas shift reaction. On the other hand, the addition of copper was remarkably improved the catalytic performances of the (NiMg)Al solid. So, the presence of this element supported the partial oxidation of methane with production of syngas (CO + H₂). With the addition of iron or copper for the catalyst composition, we were observed (in our previous work) the possibility of formation of NiM (M = Fe or Cu) alloy which increased nickel particles dispersion. In the case of copper, the reducibility of NiO was also assisted (TPR results) which increased catalytic activity in partial oxidation of methane.     

A methanol – Tolerant carbon supported Pt–Sn cathode catalysts

Carbon supported Pt–Sn bimetallic electrocatalysts with a Pt:Sn 90:10 atomic ratio were prepared by impregnation method and then heat treated at 300 and 500 °C under Helium atmosphere. The purpose of this work is to investigate the effect of tin addition to platinum for methanol tolerant oxygen reduction reaction. In this sense, structure and morphological properties of supported bimetallic catalysts were correlated to the catalytic performance. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations confirm the formation of Pt–Sn bimetallic electrocatalysts with a Pt single-phase material alloy and revealed an increase in the average particle size after heat treatment. The electrocatalytic activities of these samples for the oxygen reduction reaction (ORR) were examined in acidic medium using both a rotating disk (RDE) and a rotating ring disk (RRDE) electrodes. Compared with the Pt/C, Pt–Sn/C bimetallic catalysts show superior electrocatalytic activity towards ORR with an approaching four electron pathway leading to water formation. The specific and mass activity for ORR follow the order of Pt–Sn/C-500 ≈ Pt–Sn/C-300 > Pt–Sn/C > Pt/C. Furthermore, it is found that among the three Pt–Sn samples, Pt–Sn/C-500 exhibits the highest methanol tolerance. These experimental observations indicate that the addition of Sn into Pt is favorable to maximize the ORR performances of platinum and further the heat treatment is beneficial to improve the methanol tolerance behavior. On this basis, the novel Pt–Sn catalysts can be considered as potential candidates to be used as cathodes in Direct Methanol Fuel Cells.     

The influence of pH,hydrolysis and degree of substitution on the temperature‐sensitive properties of polyaspartamides

Temperature‐sensitive polyaspartamide obtained by the aminolysis reaction of polysuccinimide with isopropylamine has been proposed as a good material for biomedical applications. The polymer is susceptible to hydrolysis producing carboxyl groups; thus the temperature‐sensitive behavior of the polymer depends on pH. A set of polyaspartamides was synthesized with different degrees of hydrolysis (DH) and substitution (DS). The influence of DH, DS and pH on the lower critical solution temperature (LCST) of the polyaspartamides was studied. The LCST of the polyaspartamides increases as the pH increases and at the same pH the polymer with higher DH presents a higher LCST. Also, at the same pH an increment in the DS produces a decrease in the LCST. These tendencies are explained by the presence of a carboxylate group on the polyaspartamide structure. The behaviors can be tailored as functions of DS and DH enabling the use of temperature‐sensitive polyaspartamide in different biomedical applications where pH and/or temperature changes will trigger a drug delivery. © 2018 Society of Chemical Industry     

Nanoporous zirconium oxide prepared using the supramolecular templating approach

Hexagonal (Hx-ZrO₂) and lamellar (L-ZrO₂) phases of zirconium oxide have been prepared using the supramolecular templating approach. Long chain primary alkyl amines led to the formation of lamellar phases, while quaternary ammonium surfactants gave hexagonal phases. The materials have been characterized by XRD, TG/DTG, IR, XPS, SEM and EDX techniques. The influence of various synthesis parameters such as (i) the ZrO₂ surfactant ratio, (ii) the surfactant/water ratio, (iii) the nature of surfactant, (iv) the crystallization temperature and (v) the crystallization time have been investigated. The final solid products were found to be thermally unstable regardless of their structure. Removal of the surfactant from the mesopores by solvent extraction without damaging the structure was not possible.