Graphene based catalyst supports for high temperature PEM fuel cell application

In this study, the effect of graphene nanoplatelet (GNP) and graphene oxide (GO) based carbon supports on polybenzimidazole (PBI) based high temperature proton exchange membrane fuel cells (HT-PEMFCs) performances were investigated. Pt/GNP and Pt/GO catalysts were synthesized by microwave assisted chemical reduction support. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brauner, Emmet and Teller (BET) analysis and high resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure and morphology of the as-prepared catalysts. The electrochemical surface area (ESA) was studied by cyclic voltammetry (CV). The results showed deposition of smaller Pt nanoparticles with uniform distribution and higher ECSA for Pt/GNP compared to Pt/GO. The Pt/GNP and Pt/GO catalysts were tested in 25 cm² active area single HT-PEMFC with H₂/air at 160 °C without humidification. Performance evaluation in HT-PEMFC shows current densities of 0.28, 0.17 and 0.22 A/cm² for the Pt/GNP, Pt/C and Pt/GO catalysts based MEAs at 160 °C, respectively. The maximum power density was obtained for MEA prepared by Pt/GNP catalyst with H₂/Air dry reactant gases as 0.34, 0.40 and 0.46 W/cm² at 160 °C, 175 °C and 190 °C, respectively. Graphene based catalyst supports exhibits an enhanced HT-PEMFC performance in both low and high current density regions. The results indicate the graphene catalyst support could be utilized as the catalyst support for HT-PEMFC application.     

The effects of Co/Ce loading ratio and reaction conditions on CDRM performance of CoCe/ZrO2 catalysts

This work mainly aims to establish a link between Co/Ce loading ratio in CoCe/ZrO₂ catalysts and their Carbon Dioxide Reforming of Methane (CDRM) performance. In this context, catalysts with different Co and Ce loadings were prepared and characterized via BET, XRD, HRTEM-EDX, XPS and Raman, and parametrically tested under different CDRM conditions. Dispersion of Co particles was nonhomogeneous on all samples. For the sample with the highest Co/Ce ratio (10%Co2%Ce/ZrO₂), higher amount of lattice oxygen vacancies and lowest degree of ceria reduction were determined. Raman analysis showed that graphitic carbon coexisted with amorphous carbon on the surface of all spent samples. The extent of side reactions prevailed in determining selectivity. It was expressed that both CoCe synergistic interaction and synchronous contribution of Ce and ZrO₂ were enhanced for the samples having lower Co/Ce ratio. It was confirmed that Ce is only responsible for oxygen transfer but not its formation.     

The effect of substrate composition on the electrochemical and mechanical properties of PEO coatings on Mg alloys

Plasma electrolytic oxidation (PEO) is a unique surface treatment technology which is based on anodic oxidation forming ceramic oxide coatings on the surface of light alloys such as Mg, Al and Ti. In the present study, PEO coatings prepared on AZ91D, AZ31B, AM60B and AM50B Mg alloys have been investigated. Surface morphology and elemental composition of coatings were determined using scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). SEM results showed that the coating exhibited a porous top surface layer and a subsequent dense layer with micro-pores and shrinkage cracks. Phase analysis of coatings was carried out by X-ray diffraction (XRD). XRD analyses indicated that PEO coatings on AZ alloys had higher amount of Periclase (MgO) followed by the presence of Spinel (MgAl₂O₄) e.g. on the AZ91D alloy compared to that on AM series alloys. In order to examine the effect of substrate composition on adhesion strength of PEO coating scratch tests were carried out. Electrochemical corrosion tests were undertaken by means of potentiodynamic polarization technique in 3.5% NaCl solution at room temperature (20 ± 2 °C). Corrosion test results indicated that the corrosion rates of coated Mg alloys decreased by nearly two orders of magnitude as compared to bare Mg alloys. PEO coatings on AZ series alloys showed better corrosion resistance and higher adhesion properties than AM series alloys. In addition to the PEO processing parameters, such are mainly attributes of the compositional variations of the substrate alloys which are responsible for the formation, phase contents and structural properties of the PEO coatings.     

Co-delivery of pemetrexed and miR-21 antisense oligonucleotide by lipid-polymer hybrid nanoparticles and effects on glioblastoma cells

Abstract

Combination therapy using anticancer drugs and nucleic acid is a more promising strategy to overcome multidrug resistance in cancer and to enhance apoptosis. In this study, lipid-polymer hybrid nanoparticles (LPNs), which contain both pemetrexed and miR-21 antisense oligonucleotide (anti-miR-21), have been developed for treatment of glioblastoma, the most aggressive type of brain tumor. Prepared LPNs have been well characterized by particle size distribution and zeta potential measurements, determination of encapsulation efficiency, and in vitro release experiments. Morphology of LPNs was determined by transmission electron microscopy. LPNs had a hydrodynamic size below 100?nm and exhibited sustained release of pemetrexed up to 10?h. Encapsulation of pemetrexed in LPNs increased cellular uptake from 6% to 78%. Results of confocal microscopy analysis have shown that co-delivery of anti-miR-21 significantly improved accumulation of LPNs in the nucleus of U87MG cells. Nevertheless, more effective cytotoxicity results could not be obtained due to low concentration of anti-miR-21, loaded in LPNs. We expect that the effective drug delivery systems can be obtained with higher concentration of anti-miR-21 for the treatment of glioblastoma.     

Solving inverse Sturm–Liouville problem with separated boundary conditions by using two different input data

In this study, we consider Sturm–Liouville (SL) equation under the separated boundary conditions on a finite interval. We get the approximate solutions of inverse SL problem by using different input data as eigenvalues and nodes (zeros of eigenfunctions), separately, and calculate the computed errors related to the obtained approximate solutions. To calculate the approximate solutions, we use Chebyshev interpolation technique by applying first kind of Chebyshev polynomials. Eventually, the numerical results are presented by providing some examples.     

Physiological and subjective evaluation of a human-robot object hand-over task

In the context of task sharing between a robot companion and its human partners, the notions of safe and compliant hardware are not enough. It is necessary to guarantee ergonomic robot motions. Therefore, we have developed Human Aware Manipulation Planner (Sisbot et al., 2010), a motion planner specifically designed for human–robot object transfer by explicitly taking into account the legibility, the safety and the physical comfort of robot motions. The main objective of this research was to define precise subjective metrics to assess our planner when a human interacts with a robot in an object hand-over task. A second objective was to obtain quantitative data to evaluate the effect of this interaction. Given the short duration, the “relative ease” of the object hand-over task and its qualitative component, classical behavioral measures based on accuracy or reaction time were unsuitable to compare our gestures. In this perspective, we selected three measurements based on the galvanic skin conductance response, the deltoid muscle activity and the ocular activity. To test our assumptions and validate our planner, an experimental set-up involving Jido, a mobile manipulator robot, and a seated human was proposed. For the purpose of the experiment, we have defined three motions that combine different levels of legibility, safety and physical comfort values. After each robot gesture the participants were asked to rate them on a three dimensional subjective scale. It has appeared that the subjective data were in favor of our reference motion. Eventually the three motions elicited different physiological and ocular responses that could be used to partially discriminate them.     

Effect of Near-Fault Vertical Ground Motions on Seismic Response of Highway Overcrossings

Results of comprehensive nonlinear response history analyses on a range of configurations representing typical highway overcrossings subjected to combined effects of vertical and horizontal components of near-fault ground motions are reported. Current seismic design guidelines in California neglect the vertical components of ground motions for peak ground accelerations less than 0.6?g and provide rather simplistic measures to account for vertical effects when they need to be incorporated in the design. Results from the numerical simulations show that the vertical components of ground motions cause significant amplification in the axial force demand in the columns and moment demands in the girder at both the midspan and at the face of the bent cap. Axial capacity of the columns and moment capacity of the girder at the face of the bent cap were generally found to be sufficient to resist the amplification in the respective demands due to vertical effects. However, midspan moments in negative bending due to vertical motions are found to exceed the capacity of the girder. The amplified midspan moments lead to yielding of the top reinforcement resulting in average peak strains on the order of 1%. It is concluded that seismic demand analysis of ordinary highway bridges in general and overcrossings in particular should incorporate provisions for considering the adverse vertical effects of near-fault ground motions.     

A solid-state dye-sensitized solar cell based on a novel ionic liquid gel and ZnO nanoparticles on a flexible polymer substrate

This paper describes a new strategy to make a full solid-state, flexible, dye-sensitized solar cell (DSSC) based on novel ionic liquid gel, organic dye, ZnO nanoparticles and carbon nanotube (CNT) thin film stamped onto a polyethylene terephthalate (PET) substrate. The CNTs serve both as the charge collector and as scaffolds for the growth of ZnO nanoparticles, where the black dye molecules are anchored. It opens up the possibility of developing a continuous roll to roll processing for THE mass production of DSSCs.     

Acetylene Dicarboxylic Acid Diallyl Ester: A Versatile Monomer for Thiol–Ene Photocured Networks

Thiol–ene photopolymerization (TEP) is a highly advantageous method for the curing of unsaturated monomers, and the design of novel monomers to be used in TEP is an active area of research. The feasibility and the versatility of novel acetylene dicarboxylic acid diallyl ester (ACDAE)-based monomers are synthesized and demonstrated. The electron deficient acetylenic core in ACDAE allows to apply three different click reactions, aza-Michael, thio-Michael, and metal-free azide–alkyne cycloaddition reactions, efficiently on it. Thus, three novel allylic monomers are synthesized and are used to prepare thiol–ene photopolymerized networks. All monomers are synthesized in good yields and structurally characterized by ¹H NMR and Fourier-transform infrared spectroscopy (FTIR) measurements. Thermal, thermomechanical, and mechanical properties, flame retardancy, transmittance, and the wettability of the networks are determined.     

Imidazole modified acrylate-containing photocured hydrogels for the efficient removal of malachite green dye from aqueous solutions

In this work, we aimed to prepare a simple and an efficient adsorbent for the removal of toxic, cationic dye; malachite green (MG). We reviewed many previous studies and designed our adsorbent based on the rationale that (1) acidic groups containing monomers which are capable of making hydrogen bonds (or electrostatic interactions) with MG are very effective in adsorption and (2) π-π stacking enhances the adsorption capacity. We first synthesized an imidazole-acrylate adduct and used it for the preparation of photocured hydrogels. The imidazole-acrylate adduct was characterized by H NMR and FTIR spectroscopy. The effect of experimental conditions on the MG adsorption properties of the hydrogels such as the effect of pH, time and MG concentration were also investigated. Under the optimum conditions (pH = 6 and 220 min contact time) at room temperature, the maximum adsorption capacity was found as high as 714.28 mg/g. The results showed that the adsorption process of the optimum hydrogel, which can be used 4 times without a significant loss in its adsorption capacity, fits the Langmuir isotherm model. The hydrogel adsorbent displayed good selectivity and reusability.