Cell Swelling by Osmosis: a Variational Approach

A very simple model for cell swelling by osmosis is introduced, resulting in a parabolic free boundary problem. In case of radially symmetric initial conditions, it is shown that the model can be viewed as a gradient flow involving entropy, surface area and the Wasserstein metric. This observation is used to construct solutions and explain the presence and nature of osmosis

Comparing Virtual Reality to Conventional Simulator Visuals: Effects of Peripheral Visual Cues in Roll-Axis Tracking Tasks

This paper compares the effects of peripheral visual cues on manual control between a conventional fixed-base simulator and virtual reality. The results were also compared with those from a previous experiment conducted in a motion-base simulator. Fifteen participants controlled a system with second-order dynamics in a disturbance-rejection task. Tracking performance, control activity, simulator sickness questionnaire answers, and biometrics were collected. Manual control behavior was modeled for the first time in a virtual reality environment. Virtual reality did not degrade participants manual control performance or alter their control behavior. However, peripheral cues were significantly more effective in virtual reality. Control activity decreased for all conditions with peripheral cues. The trends introduced by the peripheral visual cues from the previous experiment were replicated. Finally, VR was not more nauseogenic than the conventional simulator. These results suggest that virtual reality might be a good alternative to conventional fixed-base simulators for training manual control skills

Rotational and Translational Velocity and Acceleration Thresholds for the Onset of Cybersickness in Virtual Reality

This paper determined rotational and translational velocity and acceleration thresholds for the onset of cybersickness. Cybersickness causes discomfort and discourages the widespread use of virtual reality systems for both recreational and professional use. Visual motion or optic flow is known to be one of the main causes of cybersickness due to the sensory conflict it creates with the vestibular system. The aim of this experiment is to detect rotational and translational velocity and acceleration thresholds that cause the onset of cybersickness. Participants were exposed to a moving particle field in virtual reality for a few seconds per run. The field moved in different directions (longitudinal, lateral, roll, and yaw), with different velocity profiles (steady and accelerating), and different densities. Using a staircase procedure, that controlled the speed or acceleration of the field, we detected the threshold at which participant started to feel temporary symptoms of cybersickness. The optic flow was quantified for each motion type and by modifying the number of features, the same amount of optic flow was present in each scene. Having the same optic flow in each scene allows a direct comparison of the thresholds. The results show that the velocity and acceleration thresholds for rotational optic flow were significantly lower than for translational optic flow. The thresholds suggestively decreased with the decreasing particle density of the scene. Finally, it was found that all the rotational and translational thresholds strongly correlate with each other. While the mean values of the thresholds could be used as guidelines to develop virtual reality applications, the high variability between individuals implies that the individual tuning of motion controls would be more effective to reduce cybersickness while minimizing the impact on the experience of immersion

How to Mix Molecules with Mathematics

In this paper we develop two methods to calculate thermodynamic properties of mixtures. Starting point are the basic assumptions that also form the basis for the COSMO-RS model. In this approach, the individual molecules are represented by their geometrical shape with an electrical charge density on their surfaces. Next, the surface is split up into surface segments each with its own charge. In COSMO-RS a strong reduction is introduced by treating the segments as if they are completely independent. In the present study we take into account that the coupling between two patches is essentially dependent on the charge distribution on neighboring segments and on the local geometrical structure of the surface. Two approaches are followed. The first one points out how the model equations, which comprise the optimization of the entropy and conservation of internal energy, can efficiently be solved in general, thus also if the dependency between segments and the local geometry is included in the expression for the coupling energy between segments. In the second method the configuration with maximal entropy and prescribed energy is sought via simulation. Successive molecular configurations of the mixture are simulated and updated via a genetic algorithm to optimize the entropy. The second method is more time consuming but very general

In the Shadow of Tolerance: the discursive context of Dutch-born Muslim youth

Despite a public discourse on tolerance, anxiety about immigrants, Islam and the preservation of Dutch values has amplified fear of Muslim youth in the Netherlands. In this context, Dutch-born Muslim youth endure social and systemic discrimination that affects all aspects of their futures, including available educational opportunities and eventually their prospects for employment. ased on a one-year qualitative study conducted in Amsterdam, this article explores the lived experience of Dutch-born Muslim youth caught at the intersection of national policies and local realities. Grounded in critical literature originating in the Netherlands and in Europe, this inquiry triangulates participant observations, focus groups with youth ( n = 25) and interviews with youth workers ( n = 25) to disclose the hostile discursive contexts faced by Muslim youth. Findings indicate that anti-Muslim and anti-immigrant discourses permeate the everyday experiences of Muslim youth, including the practices and structures of youth programs they attend. The study raises questions about multicultural policies that appear progressive and attempt to build social cohesion but may in fact further alienate and oppress Muslim youth. It also reveals how Muslim youth navigate oppression by agentically constructing their identities while resisting the dehumanizing categories in which they are placed.</jats:p

Differences in Leadership Styles Between Genders: Outcomes and Effectiveness on Team Success

The overall research problem addressed in this study is the gender role expectations of leaders and the undervaluation of women leaders. It is important for organizations and followers to understand that women can be as or more effective than men leaders. The purpose of this research was to examine the different leadership styles between men and women that promoted the success of a team, guided by Relational-Cultural Theory (RCT), which holds that that people develop gender role expectations of others behavior based on a sex-based division of labor. The foundation of this study was leadership theory that includes that trait, behavior, and power can explain who some leaders succeed and other leaders fail. The study used a quantitative ex post facto research design, with data, including demographic descriptive data. The MLQ revealed the leaders leadership style. The Team Excellence and Collaborative Team Leader Questionnaire measured efficiency and success of the leader in completing the research activity. An independent-samples t-test was conducted to determine if there was a difference between genders with respect to leadership styles. The results of the t-test showed a significant difference in the leadership styles based on gender. The female leadership style tends to be transformational and the male leadership style is most likely transactional. An ANOVA was also used to determine if there was a difference among three leadership styles with respect to team success. The results of the ANOVA were statistically significant and indicated greater team success when the leadership was either transactional or transformational, than authoritative. There was no difference in team success between transformational-led and transactional-led teams