The hydrogen evolution reaction (HER) is a crucial electrochemical process for the proposed hydrogen economy since it has the potential to provide pure hydrogen for fuel cells. Nowadays, hydrogen ...electroproduction is considerably expensive, so promoting the development of new non-noble catalysts for the cathode of alkaline electrolyzers appears as a suitable way to reduce the costs of this technology. In this sense, a series of tungsten-based carbide materials have been synthesized by the urea-glass route as candidates to improve the HER in alkaline media. Moreover, two different pyridinium-based ionic liquids were employed to modify the surface of the carbide grains and control the amount and nature of their surface species. The main results indicate that the catalyst surface composition is modified in the hybrid materials, which are then distinguished by the appearance of tungsten suboxide structures. This implies the action of ionic liquids as reducing agents. Consequently, differential electrochemical mass spectrometry (DEMS) is used to precisely determine the onset potentials and rate-determining steps (RDS) for the HER in alkaline media. Remarkably, the modified surfaces show high catalytic performance (overpotentials between 45 and 60 mV) and RDS changes from Heyrovsky–Volmer to Heyrovsky as the surface oxide structures get reduced. H2O molecule reduction is then faster at tungsten suboxide, which allows the formation of the adsorbed hydrogen at the surface, boosting the catalytic activity and the kinetics of the alkaline HER.
A study has been carried out of nanotubular anodic films formed on titanium at 20
V in fluoride/glycerol electrolyte, containing up to 50
vol.% water. Anodizing was terminated at a charge of 1
C
cm
...−2. Addition of water resulted in an increased current and significantly reduced tube length associated with increased oxygen gas evolution. Films formed in the absence of added water were amorphous by electron diffraction, whereas water addition also led to the formation of anatase and rutile. The barrier layer was relatively thin for electrolyte of low water content, due to either a voltage drop in the electrolyte close to the anode or to a change in the film composition affecting the electric field across the layer. Ribbing of the external walls of the nanotubes was more evident in the presence of water. It is suggested that dissolution of a fluoride-rich layer, which separates the nanotubes, accompanies the nanotube growth, with the dissolution allowing transient film formation at the external walls of the nanotubes when the residual layer is sufficiently thin.
Background
Mental health for engineering undergraduates is an urgent topic for engineering educators. Narratives of engineering education requiring suffering may create or exacerbate problematic ...perceptions around stress and mental health in engineering. This study explored the roles of stress and mental health in engineering culture. We sought to explore: (1) how engineering students describe their experiences related to stress and mental health and (2) norms and expectations engineering students share about stress and mental health. Qualitative interview data were collected from 30 students who had previously responded to a college-wide survey.
Results
Codes related to experiences with stress and mental health in engineering were organized in a bioecological systems model and analyzed for emergent themes depicting engineering culture. The study identified three themes related to stress and mental health in engineering culture: (1) engineering workload as a defining stressor, (2) specific barriers that prevent engineering students from seeking help for mental health concerns, and (3) reliance on peers to cope with stress and mental health distress.
Conclusions
Our analysis provided insight into how engineering students perceive norms around stress and mental health in engineering and how this impacts help-seeking for mental health challenges. These findings have important implications for developing interventions and positive cultures that support student mental health.
The ability to control the three-dimensional architecture of graphene-based materials following a rational design is essential for technological applications. Here we demonstrate that the ...electrochemical etching can be used as a surgical tool to tailor the morphology of graphene electrodes and to impart special features, like micrometric channels and controlled mesoporosity (foams). The final materials, thanks to the high surface area, can represent a promising class of carbon-based supercapacitors. Otherwise, new materials can be prepared using a bottom-up strategy that exploits the self-assembly of the graphene oxide quantum dots produced during the electrochemical erosion. The advantages of this second approach reside not only in the possibility to downscale the control over the spatial organization as compared to the use of conventional micrometric graphene sheets, but also in the introduction of the intrinsic luminescent properties of the quantum dots in the final material. As a proof of concept we report the preparation of luminescent nanospheres by exploiting the self-organization of the graphene oxide quantum dots around frozen water nuclei.
Summary Introduction There is an ongoing debate about the optimal use of metal-on-metal (MoM) bearings in total hip replacement, since there are uncertainties about local and systemic adverse effects ...due to wear and corrosion of these bearings. Despite various national recommendations, efforts to achieve international harmonization of specific evidence-based recommendations for best practice are still lacking. Hypothesis An international consensus study group should be able to develop recommendations on the use and monitoring of MoM bearings, preferably at the European level, through a multidisciplinary approach, by integrating the perspectives of various stakeholders. Materials and methods Twenty-one experts representing three stakeholder groups and eight countries participated in this European consensus study, which consisted of a consensus meeting, subsequent structured discussion, and consensus voting. Results The current statement defines first of all benefits, local and systemic risks, as well as uncertain issues related to MoM bearings. Safety assessment after implantation of MoM comprises all patients. A closer follow-up is recommended for large head MoM (≥ 36 mm) and resurfacing. In these implants basic follow-up should consist of x-rays and metal ion measurement of cobalt in whole blood, performed with GF-AAS or ICP-MS. Clinical and/or radiographic abnormality as well as elevated ion levels needs additional imaging (ultrasound, CT-scan and/or MARS-MRI). Cobalt values less than 2 μg/L are probably devoid of clinical concern, the threshold value for clinical concern is expected to be within the range of 2–7 μg/L. Discussion This is the first multinational, interdisciplinary, and multiprofessional approach for developing a recommendation for the use and monitoring of MoM bearings in total hip replacement. The current recommendations are in partial agreement with previous statements regarding the extent of follow-up and imaging techniques. They however differ from previous communications regarding measurement of metal ions and especially the investigated medium, technique, and eventual threshold levels. Level of evidence Level V, expert opinion/agreement conference.
Food-deceptive flowers are pollinated by animals that expect a reward but are cheated. Such plants profit from their similarity to rewarding plants and should develop signals that hinder ...discrimination. We use artificial rewarding model flowers and nonrewarding mimicking flowers that present similar visual cues. We test how additional scent cues change flower choice of the mimic by bumble bees (Bombus terrestris) in two situations: (1) both flower types are simultaneously present and can be compared by the pollinator, and (2) both flower types are encountered successively in the absence of each other. We find that in situation 1, discrimination learning is greater if scents are used as cues for identifying the mimic, whether the mimic has a different scent or if it is scentless while the model is scented. In situation 2, a generalization task, a scented mimic is avoided faster than a scentless one. Discrimination of the mimic is poorest if it has the same scent as the model, thus demonstrating a potential for scent mimicry, which has not yet been proved to exist among differently rewarding flowers. Thus, the best strategy for a mimic would be to have the same scent as the model, but this strategy may not be used due to evolutionary constraints. Alternatively, if there are several potential models, then having no scent would be a better strategy than mimicking just one of the models. In situation 1 flower discrimination by color cues is enhanced in the mere presence of scent, compared to unscented controls, even if the scent does not provide a distinguishable cue itself. The results indicate that the presence of scent may enhance color discrimination by improving attention towards visual cues and/or that combined color/odor cues may lead to better memory formation and retrieval.
Flexible, large area electronics - macroelectronics - using amorphous silicon, low-temperature polysilicon, or various organic and inorganic nanocrystalline semiconductor materials is beginning to ...show great promise. While much of the activity in macroelectronics has been display-centric, a number of applications where macroelectronics is needed to enable solutions that are otherwise not feasible are beginning to attract technical and/or commercial interest. In this paper, we discuss the application drivers and the technology needs and device performance requirements to enable high performance applications to include RF systems.
Self-organized titania nanotubes produced by electrochemical anodization in organic media for efficient photocatalytic degradation of volatile organic gas pollutants.
Self-assembled titanium oxide ...nanotubular (NTs) arrays with vertical arrangement, tailored morphological properties and variable thickness were prepared by electrochemical anodization in ethylene glycol containing electrolytes. The NTs present significant UV photocatalysis against toluene and benzene at ppb concentrations, under normal conditions of temperature and pressure. The photocatalytic activity depends on the length of the NT arrays, showing a tendency of saturation for thickness above 2.5
μm and maximum efficiency for samples with thickness of 12
μm. The optimum NT structures outperform over standard Degussa P25 films rendering them very promising for outdoor photocatalytic applications.
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