Sex Differences in Mountain Bike Accidents in Austria from 2006 to 2018: A Retrospective Analysis.

Woyke, Simon, Anja Hütter, Christopher Rugg, Willi Tröger, Bernd Wallner, Mathias Ströhle, and Peter Paal. Sex differences in mountain bike accidents in Austria from 2006 to 2018: a retrospective analysis. High Alt Med Biol. 25:89-93, 2024. Introduction: Mountain biking is becoming increasingly popular, and mountain bike (MTB) accidents are on the rise. The aim of this study was to assess sex differences in mountain biking accidents in the Austrian Alps. Methods: This retrospective study includes all MTB accidents in Austria from 2006 to 2018. Data were collected by Alpine Police officers and recorded in a national digital registry. Results: The accidents involved 5,095 mountain bikers (81% men and 19% women). The number of MTB accidents rose markedly from 208 in 2006 to 725 in 2018. Men wore a helmet more often than did women (95% vs. 92%; p = 0.001). The most common injury category was "wound/bleeding" for both sexes (men 40% and women 41%). Women were more frequently transported by helicopter or terrestrially (p > 0.001). Conclusion: In the Austrian Alps, the number of MTB accidents more than tripled between 2006 and 2018. Women were involved in only one fifth of all accidents. Sex differences in MTB accidents include (1) women wearing helmets less often, (2) women being less frequently injured, (3) women suffering fewer serious injuries, and (4) women being more frequently transported by helicopter or terrestrially, while men more often did not require transportation.

First-principles study of the magnetic exchange forces between the RuO2 (110) surface and Fe tip.

Magnetic exchange force microscopy (MExFM) is an important experimental technique for mapping the magnetic structure of surfaces with atomic resolution relying on the spin-dependent short-range exchange interaction between a magnetic tip and a magnetic surface. RuO2 is a significant compound with applications in heterogeneous catalysis and electrocatalysis. It has been characterized recently as an antiferromagnetic (AFM) material, and its magnetism has been predicted somewhat surprisingly to play an important role in its catalytic properties. In the current study, we explore theoretically whether MExFM can visualize the magnetic surface structure of RuO2 . We use density functional theory (DFT) calculations to extract the exchange interactions between a ferromagnetic Fe tip interacting with an AFM RuO2 (110) surface, as a function of tip-surface distance and the position of the tip over the surface. Mimicking the MExFM experiment, these data are then used to calculate the normalized frequency shift of an oscillating cantilever tip versus the minimum tip-surface distance, and construct corrugation height line profiles. It is found that the exchange interaction between tip and surface is strongest for a parallel configuration of the spins of the tip and of the surface; it is weakest for an anti-parallel orientation. In a corrugation profile, this gives rise to a sizable height difference of 25 pm between the spin-up and spin-down Ru atoms in the RuO2 (110) surface at a normalized frequency shift γ ${\gamma }$ =-10.12 fNm1/2 . The O atoms in the surface are not or hardly visible in the corrugation profile.

Challenges of modeling nanostructured materials for photocatalytic water splitting.

Understanding the water splitting mechanism in photocatalysis is a rewarding goal as it will allow producing clean fuel for a sustainable life in the future. However, identifying the photocatalytic mechanisms by modeling photoactive nanoparticles requires sophisticated computational techniques based on multiscale modeling. In this review, we will survey the strengths and drawbacks of currently available theoretical methods at different length and accuracy scales. Understanding the surface-active site through Density Functional Theory (DFT) using new, more accurate exchange-correlation functionals plays a key role for surface engineering. Larger scale dynamics of the catalyst/electrolyte interface can be treated with Molecular Dynamics albeit there is a need for more generalizations of force fields. Monte Carlo and Continuum Modeling techniques are so far not the prominent path for modeling water splitting but interest is growing due to the lower computational cost and the feasibility to compare the modeling outcome directly to experimental data. The future challenges in modeling complex nano-photocatalysts involve combining different methods in a hierarchical way so that resources are spent wisely at each length scale, as well as accounting for excited states chemistry that is important for photocatalysis, a path that will bring devices closer to the theoretical limit of photocatalytic efficiency.

Tailoring the Performance of ZnO for Oxygen Evolution by Effective Transition Metal Doping.

In the quest for active and inexpensive (photo)electrocatalysts, atomistic simulations of the oxygen evolution reaction (OER) are essential for understanding the catalytic process of water splitting at solid surfaces. In this paper, the enhancement of the OER by first-row transition-metal (TM) doping of the abundant semiconductor ZnO was studied using density functional theory (DFT) calculations on a substantial number of possible structures and bonding geometries. The calculated overpotential for undoped ZnO was 1.0 V. For TM dopants in the 3d series from Mn to Ni, the overpotentials decreased from 0.9 V for Mn and 0.6 V for Fe down to 0.4 V for Co, and rose again to 0.5 V for Ni and 0.8 V for Cu. The overpotentials were analyzed in terms of the binding to the surface of the species involved in the four reaction steps of the OER. The Gibbs free energies associated with the adsorption of these intermediate species increased in the series from Mn to Zn, but the difference between OH and OOH adsorption (the species involved in the first, respectively the third reaction step) was always in the range 3.0-3.3 eV, despite a considerable variation in possible bonding geometries. The bonding of the O intermediate species (involved in the second reaction step), which is optimal for Co, and to a somewhat lesser extend for Ni, then ultimately determined the overpotential. These results implied that both Co and Ni are promising dopants for increasing the activity of ZnO-based anodes for the OER.

Simple and Fast High-Yield Synthesis of Silver Nanowires.

Silver nanowires (AgNWs) combine high electrical conductivity with low light extinction in the visible and are used in a wide range of applications, from transparent electrodes, to temperature and pressure sensors. The most common strategy for the production of AgNWs is the polyol synthesis, which always leads to the formation of silver nanoparticles as byproducts. These nanoparticles degrade the performance of AgNWs' based devices and have to be eliminated by several purification steps. Here, we report a simple and fast synthesis of AgNWs with minimal formation of byproducts, as confirmed by the spectral purity of the final solution. Our synthetic strategy relies on the use of freshly prepared AgCl and on the minimization of gas evolution inside the reaction vessel. The observed synthetic improvements can be of general validity for the polyol synthesis of metallic nanostructures of different shapes and compositions.

Charge carrier dynamics and photocatalytic activity of {111} and {100} faceted Ag3PO4 particles.

Silver orthophosphate is a highly promising visible light photocatalyst with high quantum yield for solar driven water oxidation. Recently, the performance of this material has been further enhanced using facet-controlled synthesis. The tetrahedral particles with {111} exposed facets demonstrate higher photocatalytic performance than the cubic particles with {100} exposed facets. However, the reason behind this large difference in photocatalytic performance is still not understood. In this work, we study the free charge carrier dynamics, such as mobility, lifetime, and diffusion lengths, for the {111}-faceted tetrahedral and the {100}-faceted cubic particles using time-resolved microwave conductivity measurements. An order of magnitude higher charge carrier mobility and diffusion length are found for the tetrahedral particles as compared to the cubic particles. The differences in crystal structure, surface composition, and optical properties are investigated in order to understand how these properties impact the charge carrier dynamics and the photocatalytic performance of differently faceted particles.

Electrochemistry of Sputtered Hematite Photoanodes: A Comparison of Metallic DC versus Reactive RF Sputtering.

The water splitting activity of hematite is sensitive to the film processing parameters due to limiting factors such as a short hole diffusion length, slow oxygen evolution kinetics, and poor light absorptivity. In this work, we use direct current (DC) magnetron sputtering as a fast and cost-effective route to deposit metallic iron thin films, which are annealed in air to obtain well-adhering hematite thin films on F:SnO2-coated glass substrates. These films are compared to annealed hematite films, which are deposited by reactive radio frequency (RF) magnetron sputtering, which is usually used for depositing metal oxide thin films, but displays an order of magnitude lower deposition rate. We find that DC sputtered films have much higher photoelectrochemical activity than reactive RF sputtered films. We show that this is related to differences in the morphology and surface composition of the films as a result of the different processing parameters. This in turn results in faster oxygen evolution kinetics and lower surface and bulk recombination effects. Thus, fabricating hematite thin films by fast and cost-efficient metallic iron deposition using DC magnetron sputtering is shown to be a valid and industrially relevant route for hematite photoanode fabrication.

The importance of charge redistribution during electrochemical reactions: a density functional theory study of silver orthophosphate (Ag3PO4).

The structural sensitivity of silver orthophosphate (Ag3PO4) for photo-electrochemical water oxidation on (100), (110) and (111) surfaces has recently been reported by experimental studies (D. J. Martin et al., Energy Environ. Sci., 2013, 6, 3380-3386). The (111) surface showed the highest performance with an oxygen evolution rate of 10 times higher than the other surfaces. The high performance of the (111) surface was attributed to high hole mobility, high surface energy and, in a recent theoretical study (Z. Ma et al., RSC Adv., 2017, 7, 23994-24003), to a lower OH adsorption energy and the band structure. The investigations are based on a few structures and a full atomistic picture of the Ag3PO4 under electrochemical reactions is still missing. Therefore, we report here a systematic study of the oxygen evolution reaction (OER) of Ag3PO4 (100), (110), and (111) surfaces by density functional theory (DFT) calculations. Through a detailed investigation of the reaction energies and the overpotentials of OER on all possible surface orientations with all possible terminations and different involvement of Ag adsorption sites, we can confirm that (111) surfaces are highly active. However, surface orientation was not found to exclusively determine the electrochemical activity; neither did the number of Ag atoms involved in the adsorption of the intermediate species nor the type of surface termination or the different potential determining reaction steps. By using Bader charge analysis and investigation of the charge redistribution during OER, we found that the highest activity, i.e. lowest overpotential, is related to the charge redistribution of two OER steps, namely the Oad and the HOOad formation. If the charge redistribution between these steps is small, then the overpotential is small and, hence, the activity is high. Charge redistributions are usually small for the (111) surface and therefore the (111) surface is usually the most active one. The concept of charge redistribution being decisive for the high activity of Ag3PO4 may open a new design strategy for materials with highly efficient electrochemical surfaces.

Why does NiOOH cocatalyst increase the oxygen evolution activity of α-Fe2O3?

Nickel oxyhydroxide (NiOOH) is known to increase the oxygen evolution reaction (OER) performance of hematite (Fe2O3) photoanodes. In recent experimental studies, it has been reported that the increased OER activity is related to the activation of the hematite (α-Fe2O3) surface by NiOOH rather than the activity of NiOOH itself. In this study, we investigate the reason behind the higher activity and the low overpotentials for NiOOH-Fe2O3 photoanodes using first principles calculations. To study the activity of possible catalytic sites, different geometries with NiOOH as a cluster and as a strip geometry on hematite (110) surfaces are studied. Density functional theory + U calculations are carried out to determine the OER activity at different sites of these structures. The geometry with a continuous strip of NiOOH on hematite is stable and is able to explain the activity. We found that the Ni atoms at the edge sites of the NiOOH cocatalyst are catalytically more active than Ni atoms on the basal plane of the cocatalyst; the calculated overpotentials are as low as 0.39 V.

Enhanced electrochemical water oxidation: the impact of nanoclusters and nanocavities.

The structures of transition metal surfaces and metal oxides are commonly believed to have a significant effect on the catalytic reactions. Density functional theory calculations are therefore used in this study to investigate the oxygen evolution reaction (OER) over nanostructured, i.e. nanocluster and nanocavity, surfaces of hematite (Fe2O3). The calculated results demonstrate an optimum nanocluster size with respect to the OER overpotential. The presence of nanoclusters on the electrode is regarded as an attractive strategy for increasing the activity in photoelectrochemical water splitting. However, in this work, we found that the presence of a nanocavity is a more effective strategy for lowering the overpotential compared to nanoclusters. This finding of the nanocavity-favoured OER for hematite surfaces is verified by similar simulations of WO3 surfaces.

Modeling and Simulations in Photoelectrochemical Water Oxidation: From Single Level to Multiscale Modeling.

This review summarizes recent developments, challenges, and strategies in the field of modeling and simulations of photoelectrochemical (PEC) water oxidation. We focus on water splitting by metal-oxide semiconductors and discuss topics such as theoretical calculations of light absorption, band gap/band edge, charge transport, and electrochemical reactions at the electrode-electrolyte interface. In particular, we review the mechanisms of the oxygen evolution reaction, strategies to lower overpotential, and computational methods applied to PEC systems with particular focus on multiscale modeling. The current challenges in modeling PEC interfaces and their processes are summarized. At the end, we propose a new multiscale modeling approach to simulate the PEC interface under conditions most similar to those of experiments. This approach will contribute to identifying the limitations at PEC interfaces. Its generic nature allows its application to a number of electrochemical systems.

Electrical conductivity and crystallization of amorphous bismuth ruthenate thin films deposited by spray pyrolysis.

Amorphous oxide thin films with tailored functionality will be crucial for the next generation of micro-electro-mechanical-systems (MEMS). Due to potentially favorable electronic and catalytic properties, amorphous bismuth ruthenate thin films might be applied in this regard. We report on the deposition of amorphous bismuth ruthenate thin films by spray pyrolysis, their crystallization behavior and electrical conductivity. At room temperature the 200 nm thin amorphous films exhibit a high electrical conductivity of 7.7 × 10(4) S m(-1), which was found to be slightly thermally activated (E(a) = 4.1 × 10(-3) eV). It follows that a long-range order of the RuO(6) octahedra is no precondition for the electrical conductivity of Bi(3)Ru(3)O(11). Upon heating to the temperature range between 490 °C and 580 °C the initially amorphous films crystallize rapidly. Simultaneously, a transition from a dense and continuous film to isolated Bi(3)Ru(3)O(11) particles on the substrate takes place. Solid-state agglomeration is proposed as the mechanism responsible for disintegration. The area specific resistance of Bi(3)Ru(3)O(11) particles contacted by Pt paste on gadolinia doped ceria electrolyte pellets was found to be 7 Ω cm(2) at 607 °C in air. Amorphous bismuth ruthenate thin films are proposed for application in electrochemical devices operating at low temperatures, where a high electrical conductivity is required.