Mean field diffusion models for precipitation in crystalline GaAs including surface tension and bulk stresses

Based on a thermodynamically consistent model for precipitation in gallium arsenide crystals including surface tension and bulk stresses by Dreyer and Duderstadt, we propose different mathematical models to describe the size evolution of liquid droplets in a crystalline solid. The first class of models treats the diffusion-controlled regime of interface motion, while the second class is concerned with the interface-controlled regime of interface motion. Our models take care of conservation of mass and substance. We consider homogenised models, where different length scales of the experimental situation have been exploited in order to simplify the equations. These homogenised models generalise the well-known Lifshitz-Slyozov-Wagner model for Ostwald ripening. Mean field models capture the main properties of our system and are well adapted for numerics and further analysis. Numerical evidence suggests in which case which one of the two regimes might be appropriate to the experimental situation

Designing Technologies to Support Professional and Workplace Learning for Situated Practice

The papers in this special section focus on designing technologies to support professional and workplace learning in situated practices. In an era of global, organizational, and technological change, all of which are transforming the world of work, professional and workplace learning are critical for employability and organizational competitiveness. A range of fundamental transformations is changing how people work. Digital technologies are replacing human labor and, at the same time, are accelerating the expansion of job roles and work practices. Work is becoming increasingly specialized, which means that professionals in collaborative and networked ways across discipline and organization boundaries. In parallel, labor is increasingly decentralized, making decisionmaking more distributed and raising the need for remote communication and collaboration. Subsequently, work is becoming more independent from time and place, as people connect, collaborate, and work via digital technologies. These changes come with a need for substantial and continuous workplace learning, and with the need for changes in how workplace learning happens. Of course, digital technologies are already used to provide learning and training in workplaces. However, most of these learning technologies have been developed for formal education (e.g., K- 12 and higher education) rather than in workplace contexts. There is a need to understand and evidence workplace learning needs and to further develop technologies that can support and scale workplace learning

Automatic detection of accommodation steps as an indicator of knowledge maturing

Jointly working on shared digital artifacts – such as wikis – is a well-tried method of developing knowledge collectively within a group or organization. Our assumption is that such knowledge maturing is an accommodation process that can be measured by taking the writing process itself into account. This paper describes the development of a tool that detects accommodation automatically with the help of machine learning algorithms. We applied a software framework for task detection to the automatic identification of accommodation processes within a wiki. To set up the learning algorithms and test its performance, we conducted an empirical study, in which participants had to contribute to a wiki and, at the same time, identify their own tasks. Two domain experts evaluated the participants’ micro-tasks with regard to accommodation. We then applied an ontology-based task detection approach that identified accommodation with a rate of 79.12%. The potential use of our tool for measuring knowledge maturing online is discussed

The impact of information presentation and cognitive dissonance on processing systematic review summaries: a randomized controlled trial on bicycle helmet legislation

Background: Summaries of systematic reviews are a reference method for the dissemination of research evidence on the effectiveness of public health interventions beyond the scientific community. Motivated reasoning and cognitive dissonance may interfere with readers’ ability to process the information included in such summaries. Methods: We conducted a web experiment on a panel of university-educated North Americans (N = 259) using a systematic review of the effectiveness of bicycle helmet legislation as a test case. The outcome variables were the perceived tentativeness of review findings and attitude toward bicycle helmet legislation. We manipulated two types of uncertainty: (i) deficient uncertainty (inclusion vs. non-inclusion of information on limitations of the studies included in the review) and (ii) consensus uncertainty (consensual findings showing legislation effectiveness vs. no evidence of effectiveness). We also examined whether reported expertise in helmet legislation and the frequency of wearing a helmet while cycling interact with the experimental factors. Results: None of the experimental manipulations had a main effect on the perceived tentativeness. The presentation of consensual efficacy findings had a positive main effect on the attitude toward the legislation. Self-reported expertise had a significant main effect on the perceived tentativeness, and exposing participants with reported expertise to results showing a lack of evidence of efficacy increased their favorable attitude toward the legislation. Participants’ helmet use was positively associated with their attitude toward the legislation (but not with perceived tentativeness). Helmet use did not interact with the experimental manipulations. Conclusions: Motivated reasoning and cognitive dissonance influence a reader’s ability to process information contained in a systematic review summary

Improving attitudes and knowledge in a citizen science project about urban bat ecology

In order to deal with the current, dramatic decline in biodiversity, the public at large needs to be aware of and participate in biodiversity research activities. One way to do this is citizen science projects, in which researchers collaborate with volunteering citizens in scientific research. However, it remains unclear whether engaging in such projects has an impact on the learning outcomes of volunteers. Previous research has so far presented mixed results on the improvement of citizens’ attitudes and knowledge, mostly because such research has focused only on single aspects of citizen science projects in case studies. To address these limitations, we investigated the impact of an urban bat ecology project on citizens’ attitudes and knowledge about bats, and on their engagement with citizen science. We also examined whether the degree of citizen participation (i.e., collecting data vs. collecting and analyzing data) had an influence on the outcomes. We conducted four field studies and used a survey-based, experimental, pre-/post-measurement design. To vary the degree of participation, we assessed the post measurement in one group directly after data collection, whereas, in a second group, we assessed it after data collection and analysis, at the end of the project. Across all studies, the results demonstrated that citizens’ content knowledge of urban bat ecology increased, and their attitudes toward bats and toward their engagement in citizen science improved during their participation. Citizens’ degrees of participation did not influence these outcomes. Thus, our research illustrates that citizen science can increase awareness of urban bat conservation, independently of citizens’ degree of participation. We discuss the implications of our findings for the citizen science community. © 2022 by the author(s)

Macroscopic diffusion models for precipitation in crystalline gallium arsenide

Ausgehend von einem thermodynamisch konsistenten Modell von Dreyer und Duderstadt für Tropfenbildung in Galliumarsenid-Kristallen, das Oberflächenspannung und Spannungen im Kristall berücksichtigt, stellen wir zwei mathematische Modelle zur Evolution der Größe flüssiger Tropfen in Kristallen auf. Das erste Modell behandelt das Regime diffusionskontrollierter Interface-Bewegung, während das zweite Modell das Regime Interface-kontrollierter Bewegung des Interface behandelt. Unsere Modellierung berücksichtigt die Erhaltung von Masse und Substanz. Diese Modelle verallgemeinern das wohlbekannte Mullins-Sekerka-Modell für die Ostwald-Reifung. Wir konzentrieren uns auf arsenreiche kugelförmige Tropfen in einem Galliumarsenid-Kristall. Tropfen können mit der Zeit schrumpfen bzw. wachsen, die Tropfenmittelpunkte sind jedoch fixiert. Die Flüssigkeit wird als homogen im Raum angenommen. Aufgrund verschiedener Skalen für typische Distanzen zwischen Tropfen und typischen Radien der flüssigen Tropfen können wir formal so genannte Mean-Field-Modelle herleiten. Für ein Modell im diffusionskontrollierten Regime beweisen wir den Grenzübergang mit Homogenisierungstechniken unter plausiblen Annahmen. Diese Mean-Field-Modelle verallgemeinern das Lifshitz-Slyozov-Wagner-Modell, welches rigoros aus dem Mullins-Sekerka-Modell hergeleitet werden kann, siehe Niethammer et al., und gut verstanden ist. Mean-Field-Modelle beschreiben die wichtigsten Eigenschaften unseres Systems und sind gut für Numerik und für weitere Analysis geeignet. Wir bestimmen mögliche Gleichgewichte und diskutieren deren Stabilität. Numerische Resultate legen nahe, wann welches der beiden Regimes gut zur experimentellen Situation passen könnte.Based on a thermodynamically consistent model for precipitation in gallium arsenide crystals including surface tension and bulk stresses by Dreyer and Duderstadt, we propose two different mathematical models to describe the size evolution of liquid droplets in a crystalline solid. The first model treats the diffusion-controlled regime of interface motion, while the second model is concerned with the interface-controlled regime of interface motion. Our models take care of conservation of mass and substance. These models generalise the well-known Mullins-Sekerka model for Ostwald ripening. We concentrate on arsenic-rich liquid spherical droplets in a gallium arsenide crystal. Droplets can shrink or grow with time but the centres of droplets remain fixed. The liquid is assumed to be homogeneous in space. Due to different scales for typical distances between droplets and typical radii of liquid droplets we can derive formally so-called mean field models. For a model in the diffusion-controlled regime we prove this limit by homogenisation techniques under plausible assumptions. These mean field models generalise the Lifshitz-Slyozov-Wagner model, which can be derived from the Mullins-Sekerka model rigorously, see Niethammer et al., and is well-understood. Mean field models capture the main properties of our system and are well adapted for numerics and further analysis. We determine possible equilibria and discuss their stability. Numerical evidence suggests in which case which one of the two regimes might be appropriate to the experimental situation

The Impact of Topic Characteristics and Threat on Willingness to Engage with Wikipedia Articles: Insights from Laboratory Experiments

A growing body of research aims to identify the factors that motivate people to make contributions in Wikipedia. We conducted two laboratory experiments to investigate the connections between topic characteristics, perception of threat, and willingness to engage with Wikipedia articles. In Study 1 (N = 83), we examined how topic familiarity, topic controversiality, and mortality salience influenced participants’ willingness to engage with Wikipedia articles. We presented the introduction parts of 20 Wikipedia articles and asked participants to rate each article with respect to familiarity and controversiality. In addition, we experimentally manipulated participants’ level of mortality salience in terms of the amount of threat they experienced when reading the article. Participants also indicated their willingness to engage with a particular article. The results revealed that familiar and controversial topics increased the willingness to engage with Wikipedia articles. Although mortality salience increased accessibility of death-related thoughts, it did not result in any changes in people’s willingness to work with the articles. The aim of Study 2 (N = 90) was to replicate the effects of topic characteristics by following a similar procedure. We additionally manipulated uncertainty salience by assigning participants to three experimental conditions: uncertainty salience, certainty salience, and non-salience. As expected, familiar and controversial topics were of high interest in terms of willingness to contribute. However, the manipulation of uncertainty salience did not yield any significant results despite the emergence of negative emotional states. In sum, we demonstrated that topic characteristics were factors that substantially influenced people’s willingness to engage with Wikipedia articles whereas perceived threat was not