Phase Separation of Binary Charged Particle Systems with Small Size Disparities using a Dusty Plasma.

The phase separation in binary mixtures of charged particles has been investigated in a dusty plasma under microgravity on parabolic flights. A method based on the use of fluorescent dust particles was developed that allows us to distinguish between particles of slightly different size. A clear trend towards phase separation even for smallest size (charge) disparities is observed. The diffusion flux is directly measured from the experiment and uphill diffusion coefficients have been determined.

Effect of confinement on the mode dynamics of dipole clusters.

Dynamical properties of colloidal clusters composed of paramagnetic beads are presented. The clusters were trapped either in a parabolic trough or in a hard-wall confinement. In order to access the dynamics of the ensembles, the instantaneous normal mode (INM) approach is utilized, which uses cluster configurations as an input. The peaks in the mode spectra weaken when the system size is increased and when the coupling strength is lowered. The short-time diffusive properties of the clusters are deduced using the INM technique. It is found that angular diffusion is always larger than radial diffusion regardless of the shape of the external trap. Further, short-time diffusion seems to be almost independent of the coupling strength in the solid regime, but decreases with increasing packing fraction and size of the ensembles. In general, it is found that diffusion is larger for parabolically confined than for hard-wall trapped clusters.

Games, hormones, and "dark" personalities: Dark tetrad and the effects of violent gaming on aggression, cortisol, and testosterone.

We investigated how playing a violent versus non-violent video game affects cortisol and testosterone levels, whether these hormonal changes increase implicit aggressive cognition, and whether so-called Dark Tetrad personality traits (i.e., Machiavellianism, psychopathy, narcissism, everyday sadism) moderate these effects. Fifty-four men played either a violent or a non-violent video game for 25 min. Participants provided salivary samples at the beginning of the experiment (T1), after 25 min of gameplay (T2), and 20 min after gameplay ended (T3). In the violent condition, participants showed a significant decrease in cortisol levels (T1 to T2) and a significant negative trend in cortisol levels from T1 to T3. Moreover, higher Machiavellianism scores were related to a significantly stronger decrease in cortisol (T1 to T2) in this condition. In the non-violent condition, however, participants with higher scores in Machiavellianism had a higher increase in cortisol (T1 to T2). In contrast to changes in hormonal levels, there were no significant effects on implicit aggressive cognition. The present findings illustrate the complex interplay between personality, hormones, and game content, thus further specifying current notions on the effects of violent video games. Playing a violent video game can have a stress-reducing calming effect depending on personality traits such as Machiavellianism and the psychological need satisfaction associated with it. Also, the fact that VVG exposure was not automatically accompanied by an aggression-increasing effect proves that simple cause-effect models are not sufficiently specified without taking the underlying mechanisms into account.

The allure of the forbidden: breaking taboos, frustration, and attraction to violent video games.

Although people typically avoid engaging in antisocial or taboo behaviors, such as cheating and stealing, they may succumb in order to maximize their personal benefit. Moreover, they may be frustrated when the chance to commit a taboo behavior is withdrawn. The present study tested whether the desire to commit a taboo behavior, and the frustration from being denied such an opportunity, increases attraction to violent video games. Playing violent games allegedly offers an outlet for aggression prompted by frustration. In two experiments, some participants had no chance to commit a taboo behavior (cheating in Experiment 1, stealing in Experiment 2), others had a chance to commit a taboo behavior, and others had a withdrawn chance to commit a taboo behavior. Those in the latter group were most attracted to violent video games. Withdrawing the chance for participants to commit a taboo behavior increased their frustration, which in turn increased their attraction to violent video games.

Complex plasma research under microgravity conditions.

The future of complex plasma research under microgravity condition, in particular on the International Space Station ISS, is discussed. First, the importance of this research and the benefit of microgravity investigations are summarized. Next, the key knowledge gaps, which could be topics of future microgravity research are identified. Here not only fundamental aspects are proposed but also important applications for lunar exploration as well as artificial intelligence technology are discussed. Finally, short, middle and long-term recommendations for complex plasma research under microgravity are given.

Instantaneous normal mode analysis of melting of finite dust clusters.

The experimental melting transition of finite two-dimensional dust clusters in a dusty plasma is analyzed using the method of instantaneous normal modes. In the experiment, dust clusters are heated in a thermodynamic equilibrium from a solid to a liquid state using a four-axis laser manipulation system. The fluid properties of the dust cluster, such as the diffusion constant, are measured from the instantaneous normal mode analysis. Thereby, the phase transition of these finite clusters is approached from the liquid phase. From the diffusion constants, unique melting temperatures have been assigned to dust clusters of various sizes that very well reflect their dynamical stability properties.

Uncovering the Role of Mindfulness in Autonomous Motivation across Physical Education and Leisure Time: Extending the Trans-Contextual Model.

Mindfulness is assumed to foster the ability to consistently act in line with one's authentic self; a skill which has been found to enhance students' autonomous motivated behavior in the educational context. However, evidence regarding how mindfulness can be integrated into existing conceptual frameworks such as the trans-contextual model is scarce. Therefore, the present study aimed to evaluate the role of mindfulness in students' autonomous motivation in the school and leisure time contexts. Overall, N = 1877 students (M = 14.74 years, SD = 2.63) indicated their self-reported mindfulness, their perceived need for support in physical education, their autonomous motivation during physical education and leisure time, as well as their perceived behavioral control, attitude, subjective norm, and intention toward physical activity. Physical activity was additionally measured physiologically for n = 240 students using accelerometers. Path model analyses revealed that the inclusion of mindfulness substantially improved the trans-contextual model fit. Perceived autonomy support positively predicted mindfulness, which, in turn, predicted autonomous motivation in physical education and leisure time, attitude, subjective norm, and perceived behavioral control. Furthermore, mediation analyses revealed the significant indirect effects of mindfulness on physiological and self-reported physical activity. Based on these results, mindfulness can be considered a key factor in fostering students' motivation to become physically active.

Simulations and experiments of phase separation in binary dusty plasmas.

Molecular dynamics simulations of binary dusty plasmas have been performed and their behavior with respect to the phase separation process has been analyzed. The simulated system was inspired by experimental research on phase separation in dusty plasmas under microgravity on parabolic flights. Despite vortex formation in the experiment and in the simulations the phase separation could be identified. From the simulations it is found that even the smallest charge disparities lead to phase separation. The separation is due to the force imbalance on the two species and the separation becomes weaker with increasing mean particle size. In comparison, experiments on the phase separation have been performed and analyzed in view of the separation dynamics. It is found that the experimental results are reproduced by the simulation regarding the dependency on the size disparity of the two particle species.

Configurational temperature of multispecies dusty plasmas.

The dust charge of the two species in a binary mixture of particles in a dusty plasma has been measured using the concept of configurational temperature. There, the dust charge and the respective dust charge ratio are determined from the comparison of the instantaneous particle positions and the kinetic temperature. For that purpose, experiments of binary mixtures of melamine-formaldehyde and silica particles have been evaluated. The configurational temperature approach has also been checked against simulations. From these analyses it is found that the charge ratio of the two species can be obtained quite accurately, whereas for the determination of the absolute charge values a good knowledge of the confining potential is required.

Charge measurement of SiO_{2} nanoparticles in an rf plasma by ir absorption.

We have performed measurements of the ir absorption of SiO_{2} nanoparticles confined in an argon radiofrequency plasma discharge using a Fourier transform infrared spectrometer. By varying the gas pressure of the discharge and duty cycle of the applied radiofrequency voltage, we observed a shift of the absorption peak of SiO_{2}. We attributed this shift to charge-dependent absorption features of SiO_{2}. The charge-dependent shift has been calculated for SiO_{2} particles, and from comparisons with the experiment the particle charge has been retrieved using our infrared phonon resonance shift method. With the two different approaches of changing the gas pressure and altering the duty cycle, we are able to deduce a relative change of the particle charge with pressure variations and an absolute estimate of the charge with the duty cycle.

Psychological Contract Violation or Basic Need Frustration? Psychological Mechanisms Behind the Effects of Workplace Bullying.

Workplace bullying is a phenomenon that can have serious detrimental effects on health, work-related attitudes, and the behavior of the target. Particularly, workplace bullying exposure has been linked to lower level of general well-being, job satisfaction, vigor, and performance and higher level of burnout, workplace deviance, and turnover intentions. However, the psychological mechanisms behind these relations are still not well-understood. Drawing on psychological contract and self-determination theory (SDT), we hypothesized that perceptions of contract violation and the frustration of basic needs mediate the relationship between workplace bullying exposure and well-being, attitudinal, and behavioral outcomes. Self-reported data were collected among employees with different working backgrounds (N = 1,257) via Amazon's Mechanical Turk in an online survey. Results showed that feelings of contract violation and frustration of basic needs accounted for unique variation in well-being, work satisfaction, burnout, vigor, and turnover intentions, pointing to individual contributions of both psychological mechanisms. However, when controlled for frustration of basic needs, feelings of psychological contract violation were no longer a mediator between workplace bullying exposure and work performance. Helping employees to deal effectively with workplace bullying exposure might buffer its negative effects and reduce their experienced frustration of basic needs, preserving their well-being, vigor, and work performance and, eventually, prevent burnout. The present study is the first to concurrently elucidate the proposed psychological mechanisms and unique contributions of psychological contract violation and frustration of basic needs in the context of workplace bullying.

Effects of Emotional Music on Facial Emotion Recognition in Children with Autism Spectrum Disorder (ASD).

Impaired facial emotion recognition in children with Autism Spectrum Disorder (ASD) is in contrast to their intact emotional music recognition. This study tested whether emotion congruent music enhances facial emotion recognition. Accuracy and reaction times were assessed for 19 children with ASD and 31 controls in a recognition task with angry, happy, or sad faces. Stimuli were shown with either emotionally congruent or incongruent music or no music. Although children with ASD had higher reaction times than controls, accuracy only differed when incongruent or no music was played, indicating that congruent emotional music can boost facial emotion recognition in children with ASD. Emotion congruent music may support emotion recognition in children with ASD, and thus may improve their social skills.

Erratum: Configurational temperature in dusty plasmas [Phys. Rev. E 99, 063203 (2019)].

This corrects the article DOI: 10.1103/PhysRevE.99.063203.

Experimental investigation of phase separation in binary dusty plasmas under microgravity.

Three-dimensionally extended dusty plasmas containing mixtures of two particle species of different size have been investigated under microgravity conditions. To distinguish the species even at small size disparities, one of the species is marked with a fluorescent dye, and a modified two-camera video microscopy setup is used for position determination and tracking. Phase separation is found even when the size disparity is below 5%. Particles are tracked to obtain the diffusion flux, and resulting diffusion coefficients are calculated to be about -10^{-6}mm^{2}/s, which is in the expected range for a phase separation process driven by plasma forces. Additionally, a measure for the strength of the phase separation is presented that allows us to quickly characterize measurements. There is a clear correlation between size disparity and phase separation strength.

Modes of three-dimensional dust crystals in dusty plasmas.

Three-dimensional finite systems of charged dust particles confined to concentric spherical shells in a dusty plasma, so-called "Yukawa balls," have been studied experimentally with respect to their dynamic properties. For that purpose, the three-dimensional thermal Brownian motion of the dust particles around their equilibrium positions was reconstructed with high accuracy. From that the dynamic properties in the form of mode patterns and frequencies are obtained from singular value decomposition and normal mode analysis. The dynamics of the Yukawa balls was found to be dominated by large-scale low-frequency shearlike modes.

Three-Dimensional Reconstruction of Individual Particles in Dense Dust Clouds: Benchmarking Camera Orientations and Reconstruction Algorithms.

In dusty plasmas, determining the three-dimensional particle positions and trajectories of individual particles is often required. This paper benchmarks two approaches capable of reconstructing the trajectories of particles in three dimensions. The influences of the particle number, the particle number density, and the orientation of the individual cameras are studied. Additionally, the demands on the desired image quality, required for these algorithms, are discussed. The reader is given practical information for the appropriate reconstruction approach and camera positioning that should/could be used in a specific application.

Configurational temperature in dusty plasmas.

The temperature of a dust ensemble in a dusty plasma is one of its most fundamental properties. Here, we present experiments using the configurational temperature as a for the temperature analysis in dusty plasmas. Using a model of the particle interactions, the configurational temperature allows us to determine the temperature of the dust ensemble from measurements of the particle positions, rather than particle velocities. The basic concept will be presented and the technique is applied to two-dimensional finite clusters as well as three-dimensional data from an extended dust cloud. Additionally, the configurational temperature can be used to derive the particle charge and the screening length from a comparison with the standard kinetic temperature.

Escaping reality through videogames is linked to an implicit preference for virtual over real-life stimuli.

BACKGROUND: From the theory of compensatory Internet use, escapism through videogames may constitute a coping strategy that is sometimes helpful but, in some cases, maladaptive. To date, however, evidence supporting this view has been gathered only through the use of explicit self-reported questionnaires, which are known to be biased. Accordingly, the aim of the current study was to test whether the escapism motive is related to a preference for the virtual environment. METHOD: A laboratory task that allowed the measurement of implicit attitudes, namely, the Affect Misattribution Procedure, was created with stimuli from real world and videogames. The task was administered online with a series of questionnaire and completed by 273 online gamers from the community. RESULTS: Participants had more positive attitudes toward pictures depicting virtual environments than toward those depicting real environments. Furthermore, participants who frequently used videogames to escape real life and were highly engaged in video gaming had a more pronounced positive implicit attitude toward virtual environments. DISCUSSION: This study contributes to a better understanding of the psychological processes underlying escapism in videogames and calls for a refinement of the escapism construct, which can be related to both problematic (i.e., potential coping strategy) and nonproblematic patterns of videogame use. Among the limitations, it should be noted that the selection of stimuli related to videogames is restricted to one genre of game, and that the participants' environment could not be controlled due to the online design.

Fluorescent microspheres as tracer particles in dusty plasmas.

A technique has been developed to derive the dynamic properties of an ensemble of particles in dusty plasmas by using fluorescent tracer particles. The tracers form an integral part of the entire dust system. The dynamic properties of the dust system is reconstructed from the motion of the tracer. This technique allows long-duration experiments and is applied to a two-dimensional Coulomb cluster where the flow field, intershell rotation, and stagnation points of the flow have been identified.

Particle positioning techniques for dusty plasma experiments.

Video microscopy is a widely applied diagnostic to investigate the structure and the dynamics of particles in dusty plasmas. Reliable algorithms are required to accurately recover particle positions from the camera images. Here, four different particle positioning techniques have been tested on artificial and experimental data of dusty plasma situations. Two methods that rely on pixel-intensity thresholds were found to be strongly affected by pixel-locking errors and by noise. Two other methods-one applying spatial bandpass filters and the other fitting polynomials to the intensity pattern-yield subpixel resolution under various conditions. These two methods have been shown to be ideally suited to recover particle positions even from small-scale fluctuations that are used to derive the normal mode spectra of finite dust clusters.