A note on compactly generated co-t-structures

The idea of a co-t-structure is almost "dual" to that of a t-structure, but with some important differences. This note establishes co-t-structure analogues of Beligiannis and Reiten's corresponding results on compactly generated t-structures.Comment: 10 pages; details added to proofs, small correction in the main resul

Measuring presence with verbal versus pictorial scales: a comparison between online- and ex post-ratings

In this study, we compare subjective online- and post-immersion measures. Although its relevance appears obvious from a theoretical and applied research perspective, this question has not yet been addressed in previous studies. In addition, we also compare verbally and pictorially anchored scales. These factors were measured in different contents using a 2×2×2 design. We manipulated time of measure (online vs. ex post), type of measure (verbal vs. visual), and content (language vs. language-free). Participants (N=162) evaluated two video clips in terms of presence. No differences between averaged online- and post-immersion measures were found and online judgments did not interfere with the sensation of presence. In line with findings from other areas of research, the use of pictorially anchored items has major advantages. Our results suggest that those items require less mental workload and assess the sensation of presence more directly than verbally anchored items. We discuss the theoretical implications of our finding

Virtual reality public speaking training: effectiveness and user technology acceptance

Public speaking is a fundamental task in many professional or personal situations. At the same time, there is widespread fear of it, and it takes practice to present well. Previous studies suggest that Virtual Reality Public Speaking Training (VRPST) offers a promising opportunity for this. However, studies evaluating objective and subjective indicators are lacking so far, and valid control conditions are missing in previous studies. We aimed to overcome these drawbacks. In our experiment, participants (N = 42) had the task of presenting a card game to a four-person audience using five provided PowerPoint slides within a time limit of 5 minutes. They prepared either using VRPST or using common self-directed preparation (control condition), being randomly assigned to a condition. Both groups were instructed to prepare for the task at home and given 30 min to learn the rules of the game and present them using the slides. The control group was given an additional 30 min to prepare individually for the presentation task at home. The experimental group received an additional 30-min VRPST session. This training session was done without specific feedback and the presentation was repeated three times. The quality of the rule explanation, the audience-assessed presentation quality, and the subjects� self-assessed presentation quality were measured. Our results indicate that the VRPST is effective. Subjects who completed the VRPST did a better job of explaining the rules and were better rated by the audience. In addition, the experimental subjects also tended to rate their presentation better in the VRPST condition. Further analyses of those participants who completed the VRPST show high technology acceptance. Our results show the VR training had a significant performance-enhancing effect and that participants would use the VRPST if it were available to them. It seems that practicing a presentation in VR is useful and even better than a conventional preparation

How to Get There When You Are There Already? Defining Presence in Virtual Reality and the Importance of Perceived Realism

The aim of the current opinion paper is to challenge the current definition of presence in the context of virtual reality (VR). Opticians do not only measure visual acuity but also the visual field, stereoscopic vision, and color vision. In the same vein, presence researchers are encouraged to not only measure the experience of “being there” in the sense of attentional allocation to the virtual environment (VE), but also the perceived realism of the VE. Perceived realism is the result of an evaluation of the virtual world regarding (1) the subjective degree of reality of the depicted environment and (2) its overall plausibility and credibility. Thus, the sense of presence in a VE is conceived as a composite of being there and perceived realism. When in VR, a user will inevitably compare the look of virtual objects to real-world objects and judge the level of congruence (Sutcliffe and Gault, 2004). The user evaluates the plausibility and naturalness of the depicted world as well as the ease of interaction within the VE by answering questions such as: is there a shadow cast? Are the proportions of objects correct? Does the environment correspond to my own movements? Does my virtual body match the proportions of my real body? Just like the visual features, a story and its characters are also evaluated in terms of consistency and plausibility (Park et al., 2010; Gorini et al., 2011): are the consequences of actions plausible? Is the story coherent in itself? Does the causal sequence of events make sense? The answers to these questions define the degree of perceived realism. Perceived realism leads to the experience that a user not only feels surrounded by the VE, but rather has a compelling sense of reality and in extreme cases even forgets that he or she is wearing a head-mounted display (HMD). Previous papers on presence are based on the assumption that realism enhances presence (e.g., Heeter, 1992; Welch et al., 1996; Lombard and Ditton, 1997; Bystrom et al., 1999) suggested a conceptualization of presence as the degree to which a medium seems realistic. Interestingly, perceived realism is nevertheless not part of the most widely used presence definitions. It is either a possible trigger of presence or is blended in with the term being there. The conceptualization of presence as the experience of being there in a mediated environment dominates current presence definitions. Being there is strongly associated with attentional allocation and the sensation of being surrounded and absorbed by a mediated world. However, we claim that presence in VR requires much more than just being there. With the widespread use of immersive VR technology, it has become an easy task to absorb users in a VE. Thus, judgments about the realism of the VE become increasingly important. Being there and perceived realism are both important but yet different aspects of presence. They need to be combined in order to (1) adequately describe and define the experience of presence and (2) to obtain an appropriate and more complete assessment of presence in VR. Thus, theories and measures of presence need to be extended and establish perceived realism as an important domain besides being there. Presence in VR as a Two-Dimen

Virtual reality public speaking training: effectiveness and user technology acceptance

Public speaking is a fundamental task in many professional or personal situations. At the same time, there is widespread fear of it, and it takes practice to present well. Previous studies suggest that Virtual Reality Public Speaking Training (VRPST) offers a promising opportunity for this. However, studies evaluating objective and subjective indicators are lacking so far, and valid control conditions are missing in previous studies. We aimed to overcome these drawbacks. In our experiment, participants (N = 42) had the task of presenting a card game to a four-person audience using five provided PowerPoint slides within a time limit of 5 minutes. They prepared either using VRPST or using common self-directed preparation (control condition), being randomly assigned to a condition. Both groups were instructed to prepare for the task at home and given 30 min to learn the rules of the game and present them using the slides. The control group was given an additional 30 min to prepare individually for the presentation task at home. The experimental group received an additional 30-min VRPST session. This training session was done without specific feedback and the presentation was repeated three times. The quality of the rule explanation, the audience-assessed presentation quality, and the subjects’ self-assessed presentation quality were measured. Our results indicate that the VRPST is effective. Subjects who completed the VRPST did a better job of explaining the rules and were better rated by the audience. In addition, the experimental subjects also tended to rate their presentation better in the VRPST condition. Further analyses of those participants who completed the VRPST show high technology acceptance. Our results show the VR training had a significant performance-enhancing effect and that participants would use the VRPST if it were available to them. It seems that practicing a presentation in VR is useful and even better than a conventional preparation

Grindr Users Take More Risks, but Are More Open to Human Immunodeficiency Virus (HIV) Pre-exposure Prophylaxis: Could This Dating App Provide a Platform for HIV Prevention Outreach?

BackgroundTechnology has changed the way that men who have sex with men (MSM) seek sex. More than 60% of MSM in the United States use the internet and/or smartphone-based geospatial networking apps to find sex partners. We correlated use of the most popular app (Grindr) with sexual risk and prevention behavior among MSM.MethodsA nested cohort study was conducted between September 2018 and June 2019 among MSM receiving community-based human immunodeficiency virus (HIV) and sexually transmitted infection (STI) screening in central San Diego. During the testing encounter, participants were surveyed for demographics, substance use, risk behavior (previous 3 months), HIV pre-exposure prophylaxis (PrEP) use, and Grindr usage. Participants who tested negative for HIV and who were not on PrEP were offered immediate PrEP.ResultsThe study included 1256 MSM, 1090 of whom (86.8%) were not taking PrEP. Overall, 580 of 1256 (46%) participants indicated that they used Grindr in the previous 7 days. Grindr users reported significantly higher risk behavior (greater number of male partners and condomless sex) and were more likely to test positive for chlamydia or gonorrhea (8.6% vs 4.7% of nonusers; P = .005). Grindr users were also more likely to be on PrEP (18.7% vs 8.7% of nonusers; P < .001) and had fewer newly diagnosed HIV infections (9 vs 26 among nonusers; P = .014). Grindr users were also nearly twice as likely as nonusers to initiate PrEP (24.6% vs 14%; P < .001).ConclusionsGiven the higher risk behavior and greater acceptance of PrEP among MSM who used Grindr, Grindr may provide a useful platform to promote HIV and STI testing and increase PrEP uptake

Understanding the psychological impact of the COVID-19 pandemic and containment measures: an empirical model of stress

Epidemics such as COVID-19 and corresponding containment measures are assumed to cause psychological stress. In a survey during the lockdown in Switzerland (n = 1565), we found substantially increased levels of stress in the population. In particular, individuals who did not agree with the containment measures, as well as those who saw nothing positive in the crisis, experienced high levels of stress. In contrast, individuals who are part of a risk group or who are working in healthcare or in essential shops experienced similar stress lev-els as the general public. The psychological mechanisms that determine stress, caused by the COVID-19 pandemic and containment measures, are not yet clear. Thus, we conducted a path analysis to gain a deeper understanding of the psychological mechanisms that lead to stress. Experiencing fear of the disease is a key driver for being worried. Our model fur-ther shows that worries about the individual, social, and economic consequences of the cri-sis, strongly boost stress. The infection rate in the canton (i.e., state) of residence also contributes to stress. Positive thinking and perceived social, organizational, and govern-mental support mitigate worries and stress. Our findings indicate that containment mea-sures increase worries and stress, especially for those who feel that these measures either are not sufficient or go too far. Thus, highlighting positive aspects of the crisis and convinc-ing people of the effectiveness and necessity of mitigation measures can, not only promote compliance, but also reduce stress. Our model suggests that people who feel protected by the authorities have fewer worries, which can, in turn, limit the negative impact of the crisis on mental health

Learning by teaching in immersive virtual reality – Absorption tendency increases learning outcomes

We investigated the learning outcome of teaching an agent via immersive virtual reality (IVR) in two experiments. In Experiment 1, we compared IVR to a less immersive desktop setting and a control condition (writing a summary). Learning outcomes of participants who had explained the topic to an agent via IVR were better. However, this was only the case for participants who scored high on absorption tendency. In Experiment 2, we investigated whether including social cues in the task instructions enhances learning in participants explaining a topic to an agent. Instruction manipulation affected learning as a function of absorption tendency: Low-absorption participants benefitted most from being instructed to imagine they were helping a student peer pass an upcoming test, while high-absorption participants benefitted more when they were to explain the text to a virtual agent. The findings highlight the crucial role of personality traits in learning by teaching in IVR

Investigating Membrane Material Alternatives for Air Revitalization in Space

Recently, NASA’s ultimate goal has been to launch a crewed Mars mission. However, the current system used for carbon dioxide (CO2) removal in air revitalization in the International Space Station (ISS) is not equipped to handle beyond low-earth-orbit missions. The Carbon Dioxide Removal Assembly (CDRA) is a complex system that relies heavily on sorbent materials and faces challenges in reliability, energy efficiency, and material degradation. Although the CDRA has operated well in the ISS for the past two decades, health effects from high CO2 levels are amongst the most common complaints from and challenges for astronauts. Recent developments in membrane technology prove to be a promising alternative to sorbent-based systems for CO2 removal. Maintaining high selectivity for CO2 with a reasonable permeability, at such low partial pressures and in the presence of water, is among the main challenges of using membranes in this application. In this work, we have created a membrane-based model with appropriate conditions to identify the membrane technology for this application. We expect to determine a working range of critical parameters such as permeability, selectivity, and membrane area for successful CO2 separation. We will also be comparing the thermodynamic efficiency of a membrane-based process to that of the CDRA to pin-point areas of improvement

The Illusion of Being Located in Dynamic Virtual Environments. Can Eye Movement Parameters Predict Spatial Presence?

Attention allocation towards the mediated environment is assumed to be a necessary precondition to feel localized in a virtual world. In presence research, however, the potential of eye movement research has not been fully exploited so far. In this study, participants (N=44) rode on a virtual roller coaster simulation. We compare participants scoring high versus low on presence. During the ride, the eye movements and subjective ex post presence judgments were assessed. We found high sensations of presence to be associated with fewer fixations and a tendency towards longer fixation durations. In contrast to the immersive tendency trait, eye movement parameters can predict presence