CO oxidation on a single Pd atom supported on magnesia

The oxidation of CO on single Pd atoms anchored to MgO(100) surface oxygen vacancies is studied with temperature-programmed-reaction mass-spectrometry and infrared spectroscopy. In one-heating-cycle experiments CO$_2$, formed from O$_2$ and CO preadsorbed at 90 K, is detected at 260 K and 500 K. Ab-initio simulations suggest two reaction routes, with Pd(CO)$_2$O$_2$ and Pd(CO$_3$)CO found as precursors for the low and high temperature channels, respectively. Both reactions result in annealing of the vacancy and induce migration and coalescence of the remaining Pd-CO to form larger clusters.Comment: 4 pages, 3 figures, scheduled for publication in PRL 18 June 200

Impact de la communication dans le processus d’acquisition d’habiletés motrices :: expérimentation de deux méthodes en éducation physique avec des élèves allophones et francophones

Ce travail de mémoire développe une expérimentation en éducation physique qui a comme objectif de chercher la manière la plus adaptée de réaliser un apprentissage d’habileté motrice en tenant compte des difficultés de communication. Le but est de réaliser des formes finales de mouvements sur les thèmes de l’athlétisme (lancer du poids) et des agrès (barres asymétriques) avec deux méthodes d’apprentissage différentes. Un de ces processus d’apprentissage intègre les nouvelles technologies et plus particulièrement des iPads. Cette étude s’est déroulée durant 4 semaines au sein de deux classes du cycle 3 de l’école obligatoire de La Chaux-de-Fonds dont une classe d’accueil composée d’élèves allophones. Les résultats démontrent que la grande majorité des élèves, qu’ils soient francophones ou allophones, préfèrent une méthode d’apprentissage enseignée traditionnellement. Selon eux, il suffirait d’y intégrer la vidéoscopie pour que le niveau de maîtrise de l’activité soit optimal. Cet écrit est composé de trois parties. La problématique développe l’identification des deux objets de recherche, l’état des connaissances sur le problème et les questions et objectifs de recherche. La méthodologie définit la nature du corpus et les méthodes retenues pour le recueil des données. Finalement, l’analyse décrit les résultats obtenus et la solution envisagée

gafro: Geometric Algebra for Robotics

Geometry is a fundamental part of robotics and there have been various frameworks of representation over the years. Recently, geometric algebra has gained attention for its property of unifying many of those previous ideas into one algebra. While there are already efficient open-source implementations of geometric algebra available, none of them is targeted at robotics applications. We want to address this shortcoming with our library gafro. This article presents an overview of the implementation details as well as a tutorial of gafro, an efficient c++ library targeting robotics applications using geometric algebra. The library focuses on using conformal geometric algebra. Hence, various geometric primitives are available for computation as well as rigid body transformations. The modeling of robotic systems is also an important aspect of the library. It implements various algorithms for calculating the kinematics and dynamics of such systems as well as objectives for optimisation problems. The software stack is completed by python bindings in pygafro and a ROS interface in gafro_ros

Synthesis of monodispersed model catalysts using softlanding cluster deposition

In nanocatalysis, clusters deposited on solid, well-defined surfaces play an important role. For the detection of size effects it is, however, important to prepare samples consisting of deposited clusters of a single size, as their chemical properties change with the exact number of atoms in the cluster. In this paper, the experimental tools are presented to prepare such model systems. The existence of monodispersed clusters is confirmed by various experimental findings. First, the carbonyl formation of deposited Nin clusters shows no change in the nuclearity when comparing the size of the deposited clusters with one of the formed carbonyls. Second, scanning tunneling microscopy (STM) studies show that fragmentation of Sin clusters upon deposition can be excluded. In addition, the adsorption behavior of CO on deposited Pd atoms points to the existence of single atoms on the surface. Furthermore, CO oxidation results on Aun clusters confirm the existence of monodispersed clusters trapped on well-defined adsorption sites. Finally, we use Monte-Carlo simulations to define the range of clusters and defect densities, for which monodispersed clusters can be expecte

Response Burden and Dropout in a Probability-Based Online Panel Study – A Comparison between an App and Browser-Based Design

Survey respondents can complete web surveys using different Internet-enabled devices (PCs versus mobile phones and tablets) and using different software (web browser versus a mobile software application, “app”). Previous research has found that completing questionnaires via a browser on mobile devices can lead to higher breakoff rates and reduced measurement quality compared to using PCs, especially where questionnaires have not been adapted for mobile administration. A key explanation is that using a mobile browser is more burdensome and less enjoyable for respondents. There are reasons to assume apps should perform better than browsers, but so far, there have been few attempts to assess this empirically. In this study, we investigate variation in experienced burden across device and software in wave 1 of a three- wave panel study, comparing an app with a browser-based survey, in which sample members were encouraged to use a mobile device. We also assess device/software effects on participation at wave 2. We find that compared to mobile browser respondents, app respondents were less likely to drop out of the study after the first wave and the effect of the device used was mediated by subjective burden experienced during wave 1

Data Privacy Concerns as a Source of Resistance to Complete Mobile Data Collection Tasks Via a Smartphone App

Smartphones present many interesting opportunities for survey research, particularly through the use of mobile data collection applications (apps). There is still much to learn, however, about how to integrate apps in general population surveys. Recent studies investigating hypothetical willingness to complete mobile data collection tasks via an app suggest there may be substantial resistance, in particular, due to concerns around data privacy. There is not much evidence about how privacy concerns influence actual decisions to participate in app-based surveys. Theoretical approaches to understanding privacy concerns and survey participation decisions would suggest that the influence of the former over the latter is likely to vary situationally. In this paper, we present results from a methodological experiment conducted in the context of a three-wave probability-based online panel survey of the general population as part of the 2019 Swiss Election Study ("Selects") testing different ways of recruiting participants to an app. Questions included at wave 1 about online data privacy concerns and comfort sharing different types of data with academic researchers allow us to assess their impact on both hypothetical willingness to download a survey app for completing questionnaires, to take and share photos, and to share the smartphone's GPS location and actual completion of these tasks. Our findings confirm that general concerns about online data privacy do influence hypothetical willingness to complete mobile data collection tasks, but may be overridden by how comfortable people feel about sharing specific types of data with researchers. When it comes to actual compliance with task requests, however, neither privacy concerns nor comfort sharing data seem to matter. We conclude with recommendations for exploring these relationships further in future app-based studies