Search

Copyright of Canadian Journal of Ophthalmology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: When the temperature of a fuel cell vehicle is repeatedly reduced to subzero temperatures, volume changes by water/ice transformations and frost heave mechanism can cause microstructural changes in membrane–electrode assemblies (MEA), and a resultant permanent decrease in the performance of fuel cell stacks. In this study, five MEAs manufactured by different methods, were tested under repeated freeze–thaw (F–T) cycles between −20 °C and 10 °C, and the variations in their electrochemical and microstructural characteristics were analyzed according to the initial microstructures. When the MEAs were prepared by spraying catalyst inks on polymer membranes, no significant microstructural changes were observed. In the case of two supplied MEAs, void formations at the electrolyte/electrode interface or vertical cracks within the catalyst layers were observed after 120 F–T cycles. Void formation seems to be responsible for performance degradation as a result of ohmic loss, but the effect of cracks in the catalyst layers was not confirmed. In 120 F–T cycles, activation overpotentials and concentration overpotentials did not increase significantly for any of the MEAs, even although gradual decreases in the electrochemically active surface area of the platinum catalysts and changes in the porous structure were observed. [ABSTRACT FROM AUTHOR]

Abstract: Water removal from proton exchange membrane fuel cells (PEMFC) is of great importance to improve start-up ability and mitigate cell degradation when the fuel cell operates at subfreezing temperatures. In this study, we report water removal characteristics under various shut down conditions including a dry gas-purging step. In order to estimate the dehydration level of the electrolyte membrane, the high frequency resistance of the fuel cell stack was observed. Also, a novel method for measuring the amount of residual water in the fuel cell was developed to determine the amount of water removal. The method used the phase change of liquid water and was successfully applied to examine the water removal characteristics. Based on these works, the effects of several parameters such as purging time, flow rate of purging gas, operation current, and stack temperature on the amount of residual water were investigated. [Copyright &y& Elsevier]

Daytime radiative cooling is an innovative way to counter the temperature increase caused by solar exposure inside buildings, cars, and industries without consuming energy. To improve the radiative cooling performance, the light-to-heat energy conversion through solar reflection should be minimized, while the heat radiation in the wavelength range of 8–13 µm (atmospheric window) should be maximized. In this work, colored emitters for daytime radiative cooling are fabricated with silica-embedded perovskite nanocrystals, which can be colored with high light-to-photon conversion in the solar spectrum instead of light-to-heat conversion, and coated onto a highly mid-IR-radiative white emitter. The fabricated white, green, and red emitters for daytime radiative cooling exhibit sub-ambient cooling temperatures of 4.2, 3.6, and 1.7 °C, respectively, in outdoor measurements. Additionally, the enhancement of the daytime cooling performance by the light-photon conversion is proven through the comparison experiments and numerical calculation. These colored emitters for radiative cooling are more aesthetically pleasing than conventional white- and metallic-colored surface emitters, and are expected to diversify the applications for daytime radiative cooling. This research is the colored mid-IR emitters with silica-embedded perovskite nanocrystals for daytime radiative cooling, which are more aesthetically pleasing than conventional white and metallic colored surface emitters. And, the enhancement of the daytime cooling performance by the light-photon conversion is proven through the comparison experiments and numerical calculation. ga1 • The colored mid-IR emitters for daytime radiative cooling were fabricated using SiO 2 -embedded perovskite nanocrystals (NCs). • Perovskite NCs have high PLQY, resulting in efficient daytime radiative cooling by light-to-photon conversion. • The white, green and red colored emitters showed sub- or near- ambient cooling of 4.2 ℃, 3.6 ℃ and 1.7 ℃ during the daytime. • The developed colored emitters show the efficient outdoor cooling performance than commercial painted emitters. [ABSTRACT FROM AUTHOR]

• 8 ton/day gasification process was operated using waste fuel for power generation. • Various experiments were conducted for finding optimal conditions of gasification. • Average cold gas efficiency and carbon conversion ratio were 71.30 and 72.07%. • Continuous operation was achieved for about 140 h and average power generation 235 kW. • Design factors of commercial process has been derived by successful plant operation. An 8 ton/day solid refuse fuel gasification process with air oxidant was operated under various conditions to generate electricity. Solid refuse fuels with fluff type feedstock were fabricated from municipal solid wastes. The tested experimental conditions included feedstock charging rate into the gasifier, equivalence ratio, and oxygen enrichment; varying these conditions resulted in different gasification characteristics, such as cold gas efficiency and carbon conversion ratio. Optimum conditions were a charging rate of 50 to 60% by volume (504.71 to 605.65 kg/Sm2) of feedstock in the gasifier, equivalence ratio of 0.21 to 0.33, and no oxygen enrichment. Average cold gas efficiency and carbon conversion ratio were 71.30% and 72.07%, respectively, at optimum conditions. Pollutants such as dust, tar, and gases, were analyzed at the outlet of the cleaning facility and gasifier, and their low concentrations in the producer gas were sufficient to allow for operation of the gas engine. The gasification process exhibited stable operation over 288 h, which included the facility check period. The average gasifier temperature was 825 °C, 17.14% by volume of producer gas was syngas, and gas engine power generation was 235 kWh during this period; power consumption of the entire system was 68 kWh. These results demonstrate that the gasification process for converting solid waste to energy can be operated at a commercial scale. [ABSTRACT FROM AUTHOR]

Abstract: Polycrystalline Tm3+/Yb3+ co-doped CaMoO4 UC phosphors were successfully synthesized by a complex citrate-gel method and their upconversion (UC) luminescence was investigated. Under excitation at 980nm, Tm3+/Yb3+ co-doped CaMoO4 showed bright blue emission near 475nm generated by the 1G4→3H6 transition and strong NIR UC emission around 796nm generated by the 3H4→3H6 transition, with weak red emission near 650nm due to the 3F2→3H6 transition. The optimum doping concentrations of Tm3+ and Yb3+ for the highest UC luminescence were investigated, and the related UC mechanism of Tm3+/Yb3+ co-doped CaMoO4 depending on pump power was studied in detail. [Copyright &y& Elsevier]

Abstract: Yellow upconversion (UC) luminescence is observed in Ho3+/Yb3+ co-doped CaMoO4 synthesized by complex citrate-gel method. Under 980nm excitation, Ho3+/Yb3+ co-doped CaMoO4 exhibited yellow emission based on green emission near 543nm generated by 4F4, 5S2 → 5I8 transition and strong red emission around 656nm generated by 5F5 → 5I8 transition, which are assigned to the intra 4f transitions of Ho3+ ions. The optimum doping concentration of Ho3+ and Yb3+ was investigated for highest upconversion luminescence. Based on pump power dependence, upconversion mechanism of Ho3+/Yb3+ co-doped CaMoO4 was studied in detail. [Copyright &y& Elsevier]

Abstract: For PEMFC operation, water management is very important to provide both sufficient proton conductivity and mass transport. Therefore, in this study, the effect of the relative humidity (38–87%) on cell performance is examined for PEMFC MEAs with various Nafion® ionomer contents. The MEAs were fabricated using a CCM (catalyst-coated membrane) spraying method. As the relative humidity of the cathodes (RHC) increases, the cell voltages at 0.4 and 1.2A/cm2 increased for a MEA with 20wt% ionomer. This can be explained in terms of the expansion of active sites with enhanced ionic conductivity (activation overpotential). In contrast, with a higher RHC value, the cell voltages for 35wt% ionomer (more hydrophilic) gradually decreased as a result of slower gas transport (concentration overpotential). For MEAs with intermediate ionomer contents, 25 and 30wt%, the cell voltages at 0.4A/cm2 showed maximum values at a RHC of 67%, at which point the mass transport begins to be the more dominant factor. The highest unit cell performance was observed in a MEA with an ionomer content of 25wt% at a RHC of 59% and in a MEA at 20wt% ionomer content at a higher humidity of 87%. [ABSTRACT FROM AUTHOR]

Abstract: Composite membranes with inorganic substances can retain water and allow the operation of polymer electrolyte membrane fuel cells (PEMFCs) at high temperature under low humidity. In this work, the single cell was operated at high temperature using silica–Nafion composite membrane in addition with silica in catalyst layer. The cell was operated at various temperatures under different relative humidity conditions. We observed that the single cell performance decreased steeply as the cell temperature increased. The role of silica in the catalyst layer at high temperature operation was studied by varying the silica content in the catalyst layers. There was a gradual decrease in cell performance when the silica content increased in catalyst layer. The single cell performance of membrane electrode assemblies (MEAs) with composite membrane and electrode was higher than that of MEA with commercial Nafion 112 membrane for high temperature operation. [Copyright &y& Elsevier]

Abstract: Composite membranes with hydrophilic substances can retain water and allow the operation of proton exchange membrane fuel cells (PEMFCs) under non-humidified conditions. In this work, thin Nafion composite membranes with silica are prepared to operate a PEMFC with dry fuel and oxidant. In addition, the role of silica in the catalyst layer as a water retainer is studied. In particular, the anode and the cathode are modified separately to elucidate the effect of silica. The incorporation of silica in the membrane and the catalyst layer enhances single-cell performance under non-humidified operation. The cell performance of membrane–electrode assemblies using the composite membrane and electrode is higher than that of a MEA using commercial Nafion 111 membrane under non-humidified conditions. [Copyright &y& Elsevier]

Abstract: The performances of the proton exchange membrane fuel cell (PEMFC), direct formic acid fuel cell (DFAFC) and direct methanol fuel cell (DMFC) with sulfonated poly(ether sulfone) membrane are reported. Pt/C was coated on the membrane directly to fabricate a MEA for PEMFC operation. A single cell test was carried out using H2/air as the fuel and oxidant. A current density of 730mAcm−2 at 0.60V was obtained at 70°C. Pt–Ru (anode) and Pt (cathode) were coated on the membrane for DMFC operations. It produced 83mWcm−2 maximum power density. The sulfonated poly(ether sulfone) membrane was also used for DFAFC operation under several different conditions. It showed good cell performances for several different kinds of polymer electrolyte fuel cell applications. [Copyright &y& Elsevier]

Abstract: Membrane-electrode assemblies (MEAs) were fabricated by the decal transfer method with various Nafion ionomer contents (10–40 wt%) and their single cell performance and electrochemical characteristics were examined in atmospheric air at relative humidities of 25–95%. At high humidity (95%), the MEA performance was the highest with a cathode ionomer content of 30 and 20 wt% at 0.6 and 0.4 V, respectively. The optimum ionomer content of the decal MEAs increased with decreasing humidity, because of the change in the oxygen transport rate (water flooding) and number of active sites (ionic resistance). The concentration overpotential gradually increased with relative humidity up to about 0.4 V at 0.8 A/cm2, which was not considered in previous studies using pressurized air and oxygen. The combined effect of the electrochemical active surface area and ionic resistance of the cathodes on the activation overpotential was also investigated, focusing on intermediate and low humidity levels, using a newly developed impedance analysis method. [Copyright &y& Elsevier]

Abstract: We analyzed the effects of ionomer content on the proton exchange membrane fuel cell (PEMFC) performance of membrane electrode assemblies (MEAs) fabricated by a catalyst-coated membrane (CCM) spraying method in partially humidified atmospheric air and hydrogen. When high loading Pt/C catalysts (45.5 wt.%) were used, we observed that catalytic activity was not directly proportional to electrochemical active surface area (EAS). This suggests that ionic conductivity through ionomers in catalyst layers is also an important factor affecting MEA performance. In addition, the effects of mass transport were experimentally evaluated by manipulating the air stoichiometry ratio at the cathodes. MEA performance was more sensitive to flow rates under conditions of higher ionomer content. Due to the combined effect of EAS, ionic conductivity, and mass transfer characteristics (all of which varied according to the ionomer content), an MEA with 30 wt.% ionomer content at the cathode (25 wt.% at the anode) was shown to yield the best performance. [Copyright &y& Elsevier]

Abstract: Porous carbon with high surface area and pore volume can allow fine dispersion of metal nano-particles. Mesoporous carbon (MC) with high surface area was synthesized using soft colloidal template route. Pt/C catalysts with different platinum loadings were prepared from home-made MC and chloroplatinic acid solution using wet impregnation. The particle size calculated from TEM analysis showed the Pt particle size of 2.7, 3.4 and 3.6nm for 20, 40 and 80wt.% Pt/MC catalysts, respectively. The Pt particles on the porous carbon support were found to be in uniform shape and narrow range of particle size. The dispersion feature of MC-supported Pt catalysts was also compared with that of a home-made Pt catalyst supported on commercial Vulcan carbon. CO stripping and CV analysis of MC-supported Pt catalysts showed higher mass activity for electrochemical reactions under fuel cell conditions. [Copyright &y& Elsevier]

Abstract: The major functions of bipolar plates in fuel cell systems are to transport effectively the reactants and the products to and from the electrodes, and to collect efficiently the current that is generated in the cell. A suitable approach to enhance the performance of the bipolar plate with respect to mass transport is to optimize the channel dimension and shape. In this study, the impact of the cathode channel depth on the performance of direct methanol fuel cells is investigated. When the channel depth of the bipolar plate is decreased from 1.0 to 0.3mm, the cell performance increases and also remains stable during continuous operation of the cell. The decreased channel depth leads to an increase in the linear velocity of the reactants and products at a given volumetric flow rate that, in turn, facilitates their mass transport. Furthermore, in smaller channels (shallower channels), the pressure drop is increased and this can lead to an increase in partial pressure of the oxygen, which has a positive impact on cell performance. The effect of cathode channel depth on the transport behaviour of reactants and products is studied by means of employing the transparent plates, which are designed to monitor visually the flow of reactants and products in the cathode channels. Additionally, the pressure drop and linear velocity in the cell is calculated by using a computational fluid dynamics (CFD) technique. [Copyright &y& Elsevier]

Abstract: Several different shut-down procedures were carried out to reduce the degradation of membrane electrode assembly (MEA) in a proton exchange membrane fuel cell (PEMFC). The effects of close/open state of outlets of a single cell and application of a dummy load during the shut-down on the degradation of the MEA were investigated. Also, we elucidated the relationship between the thickness of the electrolyte membrane and the degradation of the MEA for different shut-down procedures. When a thin electrolyte membrane was used, the closer of outlets mitigated the degradation during on/off operation. For the thicker electrolyte membrane, the dummy load which eliminates residual hydrogen and oxygen in the electrodes should be applied to lower the degradation. [Copyright &y& Elsevier]

Abstract: Sodium borohydride (NaBH4) in the presence of sodium hydroxide as a stabilizer is a hydrogen generation source with high hydrogen storage efficiency and stability. It generates hydrogen by self-hydrolysis in aqueous solution. In this work, a Co–B catalyst is prepared on a porous nickel foam support and a system is assembled that can uniformly supply hydrogen at >6.5Lmin−1 for 120min for driving 400-W polymer electrolyte membrane fuel cells (PEMFCs). For optimization of the system, several experimental conditions were changed and their effect investigated. If the concentration of NaBH4 in aqueous solution is increased, the hydrogen generation rate increases, but a high concentration of NaBH4 causes the hydrogen generation rate to decrease because of increased solution viscosity. The hydrogen generation rate is also enhanced when the flow rate of the solution is increased. An integrated system is used to supply hydrogen to a PEMFCs stack, and about 465W power is produced at a constant loading of 30A. [Copyright &y& Elsevier]

• Extracellular vesicles (EVs) of Streptococcus equi were purified. • Screening EV proteome revealed 32 potential vaccine candidates (PVCs). • Mice vaccinated with EVs intraperitoneally were protected against S. equi infection. • S. equi EVs may serve as vaccines against S. equi infections. Streptococcus equi subspecies equi is a pathogenic bacterium that causes strangles, a highly contagious respiratory infection in horses and other equines. The limitations of current vaccines against S. equi infection warrants the development of an affordable, safe, and effective vaccine. Because gram-positive extracellular vesicles (EVs) transport various immunogenic antigens, they are attractive vaccine candidates. Here, we purified the EVs of S. equi ATCC 39506 and evaluated them as a vaccine candidate against S. equi infection in mice. As an initial step, comparative proteomic analysis was performed to characterize the functional features of the EVs. Reverse vaccinology and knowledge-based annotations were then used to screen potential vaccine candidates (PVCs) for S. equi ATCC 39506. Finally, 32 PVCs were found to be enriched in the EV fraction, suggesting the usefulness of this fraction as a vaccine. Importantly, a significantly higher survival rate after S. equi infection was detected in mice immunized with S. equi -derived EVs via the intraperitoneal route than in mice immunized with heat-killed bacteria. Of note, immunoprecipitation-mass spectrometry results validated various immunogenic antigens within the EV proteome. In conclusion, our results suggest that S. equi -derived EVs can serve as a vaccine candidate against S. equi infection. [ABSTRACT FROM AUTHOR]

Purpose: To describe the morphologic features of ischemic diabetic maculopathy by high-resolution optical coherence tomography (OCT) and their correlation with the damaged foveal avascular zone (FAZ) on fluorescein angiography (FA). Design: Observational case series. Participants: One hundred twenty-four eyes of 63 patients with diabetic retinopathy and acceptable FA and OCT images were studied. Twenty-three normal fellow eyes of 23 nondiabetic patients with unilateral acute central serous choroidopathy also were studied. Methods: High-speed Fourier-domain OCT was used with a speckle noise-reduction technique to obtain detailed horizontal and vertical images through the center of the fovea and horizontal raster scans every 100 μm. Foveal ganglion cell layer (GCL) damage was identified on OCT as an evident difference in foveal thickness and contour compared with a normal fovea or as asymmetry within the fovea. Fluorescein angiography was performed by confocal scanning laser ophthalmoscope (HRA 2; Heidelberg Engineering, Heidelberg, Germany), and FAZ damage visible during the FA arterial phase was graded according to the Early Treatment Diabetic Retinopathy Study (ETDRS) FA grading system. Correlations were sought between foveal GCL damage identified on OCT and FA capillary dropout sites. Main Outcome Measures: Foveal GCL damage on OCT, the size of the foveola on OCT (defined as the area of GCL thickness <10 μm), ETDRS grading of FAZ on FA, and visual acuity. Results: Among the 124 eyes with diabetic retinopathy, 62 (50%) had FA evidence of either FAZ damage higher than grade 1 or FAZ capillary loss. In these eyes, damage to the FAZ seen on FA also could be detected on OCT (positive predictive value, 84.5%; negative predictive value, 72.9%), and locations of FAZ damage seen on FA corresponded well with sites of foveal GCL damage on OCT. In nondiabetic, normal eyes, the size of the foveola on OCT matched the size of the FAZ on FA. Conclusions: Evidence of foveal GCL damage on OCT is a good indicator of macular ischemic damage in eyes with diabetic retinopathy. Although in this study FA was more sensitive than OCT in detecting vascular damage, OCT provides objective results and seems to be a good noninvasive substitute for FA. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. [Copyright &y& Elsevier]