Transparent PMMA/silica nanocomposites containing silica nanoparticles coating under supercritical conditions

This work reports the preparation of PMMA/silica nanocomposites with high optical transparency and enhanced mechanical properties using a melt compounding method. The surface of SiO₂ particles was modified with a γ-methacryloxypropyltrimethoxy silane coupling agent in a supercritical carbon dioxide-ethanol mixture and by conventional procedure. Dispersion of silica nanoparticles in ethanol at low temperatures plays an important role in deagglomeration and dispersion of nanosilica, which leads to the optimal particle-matrix bonding in composites. The optimal mechanical and optical properties were found for composites loaded with 5 wt% silica nanoparticles treated under supercritical coating method.     

The Expression Pattern of Surface Markers in Canine Adipose-Derived Mesenchymal Stem Cells

The influence of cultivation on the expression pattern of canine adipose-derived mesenchymal stem cells (cAD-MSCs) surface markers, contributing to, among others, the promotion of growth, proliferation, differentiation and immunomodulatory mechanisms of an excellent therapeutic, is still unknown. To fill the gap, we investigated CD90, CD44, CD73, CD29, CD271, CD105, CD45 and CD14 patterns of expression at the protein level with flow cytometry and mRNA level using a real-time polymerase chain reaction array. Gentle variations of expression occurred during cultivation, along with increased CD90, CD44 and CD29 expression, low and decreasing CD271 and CD73 expression and a decrease of initially high CD105. As expected, CD45 and CD14 were not expressed by cAD-MSCs. Interestingly, we discovered a significant decrease of CD73 expression, compared to early (P1–P3) to late (P4–P6) passages, although the CD73 gene expression was found to be stable. The percentage of positive cells was found to be higher for all positive markers up to P4. As CD73′s one important feature is a modulation from a pro-inflammatory environment to an anti-inflammatory milieu, the expression of CD73 in our conditions indicate the need to consider the time cells spend in vitro before being transplanted into patients, since it could impact their favourable therapeutical properties.     

Properties and drug release profile of poly(N-isopropylacrylamide) microgels functionalized with maleic anhydride and alginate

This study highlights the advantages of functionalized poly(N-isopropylacrylamide) (PNIPAAm) microgels over pure PNIPAAm microgels in terms of polymer network properties and drug release profiles. PNIPAAm network was modified by addition of maleic anhydride (MA) as a comonomer and by formation of interpenetrating polymer network in the presence of alginate. The functionalized thermosensitive microgels in the size range from 20 to 80 μm and with better performance in comparison with pure PNIPAAm microgels were prepared by inverse suspension polymerization. The impact of MA and alginate on the PNIPAAm microgel structure was evaluated through analysis of microgel size, size distribution, volume phase transition temperature (VPTT), equilibrium swelling ratio as well as morphology of the system. It was shown that the controlled modification of PNIPAAm network could result in microgels of considerably improved swelling capacity with unchanged thermosensitivity and maintained open pore morphology. In addition, drug release behavior of microgels could be markedly altered. Release of procaine hydrochloride from the selected microgels was studied using Franz diffusion cell at temperatures below and above VPTT of the microgels. Temperature-controlled drug release pattern was dependent on the type of functionalization of PNIPAAm network. According to drug loading properties and drug release mechanism, PNIPAAm/MA copolymer microgels demonstrated the optimal performances.     

CO Methanation Over Ru�CAl2O3 Catalysts: Effects of Chloride Doping on Reaction Activity and Selectivity

The selective CO methanation (CO-SMET) process via Ru?CAl₂O₃ catalysts was investigated as a tool for complete CO removal in fuel processors, when the H₂-rich gas so produced is employed for PEM-FCs applications to vehicles, boats, yachts and residential co-generators. CO-SMET seems, in fact, to be a good alternative to the most widely used CO preferential oxidation (CO-PROX) process. The performance of Ru-based catalysts on alumina carrier for efficient CO removal through CO-SMET was studied, exploring the role of two different Ru precursors (chloride and nitrate), and the doping effect of chloride and of Ru load (1%, 3% and 5%). First, two catalytic families (Ru?CAl₂O₃_Cl and Ru?CAl₂O₃_NO₃) were prepared by incipient wetness impregnation of alumina powder synthesized via solution combustion synthesis, by varying the Ru load. Then, based on the best obtained results, a third catalytic family was prepared adding chloride to Ru?CAl₂O₃_NO₃ catalysts by impregnation. The CO removal performance was determined at catalyst powder level in a fixed bed micro reactor. Better performances were exhibited when Ru was deposited from chloride precursor, but the post-addition of chlorine to fresh Ru?CAl₂O₃ catalysts prepared with nitrate precursor tremendously improved their selectivity toward CO methanation. In particular, with both 1% and 3% Ru?CAl_NO₃ catalyst chlorine doped, complete CO conversion was reached in a proper temperature range where the CO₂ methanation was suitably kept at a low acceptable level.     

Synthesis, characterization and drug release properties of thermosensitive poly(N-isopropylacrylamide) microgels

Nanocomposite membranes (NCMs) were prepared by using the solution casting technique by incorporating the different amounts like 6, 8, 10 wt.% of Preyssler type heteropolyacid nanoparticles to the sodium alginate. Prepared NCMs were utilized for the sorption and permeation studies for the aqueous isopropanol solutions at different concentrations. Sorption experiment enabled the study of interactions between the components of the mixture and the polymer. Flory-Huggins interaction parameters between the permeating molecules and polymer and solubility parameters were determined to explain the sorption behavior of the NCMs. Permeation properties of the NCMs were tested by applying them for pervaporation dehydration of IPA at different concentrations. Different PV parameters like separation factor, flux, Permeance and selectivity were calculated to explain the permeation behavior of the NCMs. In this study, increased sorption, permeation and selectivity was observed for the NCMs than pristine sodium alginate membrane, indicating that NCMs are efficient for PV dehydration of the IPA. Solution-diffusion model was adopted to study the mass transfer through the membrane by calculating the diffusion coefficients.     

Contact states recognition in robotic part mating based on support vector machines

In order to autonomously execute part mating, an intelligent robot should be able to carry out active compliant motion. Contact states recognition machine is a missing link for implementation of this kind of motion within an intelligent robotic assembly system. In this paper, we present an approach to design contact states recognition machines for various types of part mating problems. We have chosen generalized mating force as a basic feature measured from the process. Starting from force measurements, online recognition is carried out using class boundaries and transduction mappings obtained during offline training. The basis for the proposed offline training procedure is not experimental data but a mechanical model of the part mating process. This enables supervised training without requiring numerous experiments. Furthermore, this has allowed extraction of qualitative features from the analytical model of mating force. To provide good time localization and phase correctness, we have utilized discrete wavelet transform for feature extraction. The obtained patterns have been classified using support vector machines to obtain a recognition machine with good generalization properties. The proposed machine is elaborated and experimentally verified using case study of cylindrical part mating with chamfer crossing. We have used quasi-static model of insertion force as a starting point in the training process. Exploiting some characteristics of Daubechies wavelets, we have managed to extract features that are independent on characteristics of the concrete cylindrical part mating. Finally, the generated machine was evaluated using intensive real-world experiments. Herein we have shown that performance of the generated contact states recognition machine was excellent.     

High‐Molecular‐Weight Polyoxirane Copolymers and their Use in High‐Performance Dye‐Sensitized Solar Cells

Low‐crystalline random and gradient P(EO‐co‐PO) copolymers and amorphous PPO and PBO of high molecular weight were synthesized by anionic coordination polymerization. Polymer gel electrolytes based on these (co)polymers were prepared and tested for long‐term performance of DSSC. The DSSC based on P(EO‐co‐PO) copolymers have longer life time compared to the homo‐PEO‐ and homo‐PPO‐based DSSC, respectively. The cells containing the chemically crosslinked copolymer gel exhibited a high efficiency of 6% after 25 d performance, whereas the solar cells based on physically crosslinked copolymer gel showed fast degradation.

     

Altered susceptibility of granary weevil Sitophilus granarius (L.) (Coleoptera: Curculionidae) populations to insecticides after selection with pirimiphos-methyl and deltamethrin

Toxicity of the contact insecticides dichlorvos, malathion, chlorpyrifos-methyl, pirimiphos-methyl, deltamethrin and cypermethrin to granary weevil Sitophilus granarius (L.) adults from five populations previously selected with deltamethrin and pirimiphos-methyl, and two populations that had no contact with pesticides over an interval of 12 generations, was investigated in the laboratory by application to filter paper. The populations originated from storage facilities situated in different parts of the former Yugoslavia.A population originating from Apatin and one from Belgrade Port were selected three times each at the LD₅₀ level with deltamethrin and pirimiphos-methyl, respectively. In separate experiments, weevils from Belgrade Port were selected once at the pirimiphos-methyl LD₇₀ level and Bijeljina and Kikinda populations both once at the deltamethrin LD₇₀ level. All selection doses were at a level obtained from determining weevil mortality after 24 h of exposure to treated filter paper.Compared with the toxicity to laboratory weevils, the weevils from Apatin after the third selection were found to be 32.1 and 51.9 times less susceptible to deltamethrin at the LD₅₀ and LD₉₅ levels, respectively, while those from Belgrade Port were 2.7 and 3.2 times less susceptible to pirimiphos-methyl. Selection of Belgrade Port weevils at the pirimiphos-methyl LD₇₀ did not significantly affect their susceptibility to that insecticide but it caused a significant decrease in deltamethrin toxicity, which is indicative of a cross-resistance between the two compounds. Selection of Bijeljina weevils caused an increased resistance to deltamethrin, while selection of Kikinda weevils had little effect on their susceptibility to dichlorvos, but it caused a significant decrease in malathion and cypermethrin toxicity, and resistance to deltamethrin markedly increased (RR=238.8 at LD₅₀ and 660.8 at LD₉₅ levels, compared with laboratory weevils). Chlorpyrifos-methyl was the most toxic insecticide to all populations, while cypermethrin was the least toxic compound.