Development of tailored high-performance and durable electrocatalysts for advanced PEM fuel cells

A family of novel carbon materials with intermediate surface area and varying morphology and surface chemistry were used to prepare Pt/C catalysts by two different preparation procedures; a chemical impregnation method and a microwave-assisted polyol method. The catalysts were thoroughly characterized, and their electrochemical performance and stability were investigated with rotating disc electrode (RDE) cyclic voltammetric (CV) measurements. The intermediate-surface-area carbon supports gave catalysts with much greater support stability than a widely used standard catalyst. The novel catalysts had lower electrochemical surface area than the reference, but their specific electrocatalytic activity towards the oxygen-reduction reaction (ORR) was much higher, and some of them also featured higher mass-specific ORR activity than the reference. The series of catalysts prepared by the microwave-assisted polyol method featured smaller Pt nanoparticles and higher activities than those prepared by impregnation. On the other hand, the impregnated catalysts showed better durability of the Pt particles. The most promising catalysts were selected and elaborated in further optimized preparation procedures to obtain quantities sufficient for their use in proton-exchange membrane fuel cells (PEMFCs).     

Peptide‐Passivated Lead Halide Perovskite Nanocrystals Based on Synergistic Effect between Amino and Carboxylic Functional Groups

A new strategy has been developed using peptides with amino and carboxylic functional groups as passivating ligands to produce methyl ammonium lead bromide (CH₃NH₃PbBr₃) perovskite nanocrystals (PNCs) with excellent optical properties. The well‐passivated PNCs can only be obtained when both amino and carboxylic groups are involved, and this is attributed to the protonation reaction between ? NH₂ and ? COOH that is essential for successful passivation of the PNCs. To better understand this synergistic effect, peptides with different lengths have been studied and compared. Due to the polar nature of peptides, peptide‐passivated PNCs (denoted as PNCs_peptide) aggregate and precipitate from nonpolar toluene solvent, resulting in a high product yield (≈44%). Furthermore, the size of PNCs_peptide can be varied from ≈3.9 to 8.6 nm by adjusting the concentration of the peptide, resulting in tunable optical properties due to the quantum confinement effect. In addition, CsPbBr₃ PNCs are also synthesized with peptides as capping ligands, further demonstrating the generality and versatility of this strategy, which is important for generating high quality PNCs for photonics applications including light‐emitting diodes, optical sensing, and imaging.     

Morphological and structural properties of neutron-irradiated B12C3 boron carbide microcrystals

Boron carbide B₁₂C₃ microcrystals were neutron irradiated at four different fluences, namely at 1.09, 2.19, 3.28 and 4.38 × 10¹⁶ n cm^?2. The structural properties were studied by means of Raman spectroscopy, revealing that the neutron induced structural defects are focused toward the interstitial chains of B₁₂C₃. The morphology of the B₁₂C₃ samples was studied by means of secondary electron imaging showing that the neutron irradiation did not modify the size distribution of the microcrystals.     

A Delay Aware Super-Peer Selection Algorithm for Gradient Topology Utilizing Learning Automata

Wireless Personal Communications - Peer-to-peer network is organized on top of another network as an overlay network. Super peer network is one of the peer-to-peer networks. A super peer, in a...     

Toward Cross-Border Engineering Management: Development and Test of a Practice for Idea Generation in Customer–Supplier DFM Teams

Growing inter-organizational dependence within business ecosystems necessitates more intensive cooperation between various organizational functions, not only sales and purchasing. Engineering management is one of the functions typically regarded as an in-house activity. Prior research acknowledges certain cooperative forms such as early supplier involvement, but it falls short on identifying practices of grass-roots level cooperation. However, it is the quality of the interaction between supplier and customer that is decisive if the advantages of collaboration are to materialize. This study aims to fill this obvious gap in both theory and practice by developing and testing an inter-organizational practice for co-ideation in a supplier-customer relationship. Specifically, a way of working for idea generation to improve inter-organizational learning within specific Design for Manufacturing meetings between an industrial corporation and two of its important suppliers is developed. The evaluation of the tested co-ideation practice indicated that, in comparison to the traditional way of working, the new practice contributed to a greater number of generated ideas, was found useful in practice, and expert ratings suggested that the ideas generated were of adequate quality. The implication for practice is the proposed procedure that aims to build a safe psychological environment and help participants to transcend existing behavioral roles as representatives of suppliers and customers.     

Insights on Antioxidant Assays for Biological Samples Based on the Reduction of Copper Complexes—The Importance of Analytical Conditions

Total antioxidant capacity assays are recognized as instrumental to establish antioxidant status of biological samples, however the varying experimental conditions result in conclusions that may not be transposable to other settings. After selection of the complexing agent, reagent addition order, buffer type and concentration, copper reducing assays were adapted to a high-throughput scheme and validated using model biological antioxidant compounds of ascorbic acid, Trolox (a soluble analogue of vitamin E), uric acid and glutathione. A critical comparison was made based on real samples including NIST-909c human serum certified sample, and five study samples. The validated method provided linear range up to 100 µM Trolox, (limit of detection 2.3 µM; limit of quantification 7.7 µM) with recovery results above 85% and precision <5%. The validated developed method with an increased sensitivity is a sound choice for assessment of TAC in serum samples.     

Severity of nicotine dependence moderates performance on perceptual-motor tests of attention.

Acute abstinence from cigarette smoking by nicotine-dependent smokers has been linked with cognitive deficits, but the role of nicotine dependence per se in these effects is not known. We therefore tested the relationships of nicotine dependence and smoking history with performance in perceptual-motor, timed tests of attention. Nicotine-dependent smokers (n = 37) and nonsmokers (n = 48), 18-55 years old, took both the d2 Test of Attention and the Digit Symbol Test on each of 2 test days. For smokers, testing on one day began after ad libitum smoking (<45 min since last cigarette); and on the other day, it began after overnight abstinence (>13 hr since last cigarette). On each test day, there were two test blocks with an intervening break, when only the smokers each smoked one cigarette. There were no significant effects of abstinence or of smoking one cigarette on the performance of smokers; however, across conditions, the smokers' performance on both tests correlated negatively with severity of nicotine dependence but not lifetime cigarette consumption or cigarette craving. Smokers with high nicotine dependence performed more slowly on both tests than less dependent smokers or nonsmokers. The findings suggest that severity of nicotine dependence and slowness in perceptual-motor tasks of attention share an underlying basis.