On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)

Context. Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The reference frame is defined by the positions and proper motions at epoch 2016.0 for a specific set of extragalactic sources in the (E)DR3 catalogue. Aims. We describe the construction of Gaia-CRF3 and its properties in terms of the distributions in magnitude, colour, and astrometric quality. Methods. Compact extragalactic sources in Gaia DR3 were identified by positional cross-matching with 17 external catalogues of quasi-stellar objects (QSO) and active galactic nuclei (AGN), followed by astrometric filtering designed to remove stellar contaminants. Selecting a clean sample was favoured over including a higher number of extragalactic sources. For the final sample, the random and systematic errors in the proper motions are analysed, as well as the radio-optical offsets in position for sources in the third realisation of the International Celestial Reference Frame (ICRF3). Results. Gaia-CRF3 comprises about 1.6 million QSO-like sources, of which 1.2 million have five-parameter astrometric solutions in Gaia DR3 and 0.4 million have six-parameter solutions. The sources span the magnitude range G = 13-21 with a peak density at 20.6 mag, at which the typical positional uncertainty is about 1 mas. The proper motions show systematic errors on the level of 12 μas yr-1 on angular scales greater than 15 deg. For the 3142 optical counterparts of ICRF3 sources in the S/X frequency bands, the median offset from the radio positions is about 0.5 mas, but it exceeds 4 mas in either coordinate for 127 sources. We outline the future of Gaia-CRF in the next Gaia data releases. Appendices give further details on the external catalogues used, how to extract information about the Gaia-CRF3 sources, potential (Galactic) confusion sources, and the estimation of the spin and orientation of an astrometric solution

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

The benefits of playing video games

Item does not contain fulltextVideo games are a ubiquitous part of almost all children’s and adolescents’ lives, with 97% playing for at least one hour per day in the United States. The vast majority of research by psychologists on the effects of “gaming” has been on its negative impact: the potential harm related to violence, addiction, and depression. We recognize the value of that research; however, we argue that a more balanced perspective is needed, one that considers not only the possible negative effects but also the benefits of playing these games. Considering these potential benefits is important, in part, because the nature of these games has changed dramatically in the last decade, becoming increasingly complex, diverse, realistic, and social in nature. A small but significant body of research has begun to emerge, mostly in the last five years, documenting these benefits. In this article, we summarize the research on the positive effects of playing video games, focusing on four main domains: cognitive, motivational, emotional, and social. By integrating insights from developmental, positive, and social psychology, as well as media psychology, we propose some candidate mechanisms by which playing video games may foster real-world psychosocial benefits. Our aim is to provide strong enough evidence and a theoretical rationale to inspire new programs of research on the largely unexplored mental health benefits of gaming. Finally, we end with a call to intervention researchers and practitioners to test the positive uses of video games, and we suggest several promising directions for doing so.13 p

Games for the assessment and treatment of mental health

Contains fulltext : 177663.pdf (publisher's version ) (Open Access)The community for research on video games for assessment and intervention for mental health spans multiple disciplines, from cognitive sciences, computer science, and interaction design, to psychology, neurobiology, and medicine. The goal of this workshop is to bring together an international group of researchers to discuss the current state of games for mental health and formulate a plan for moving this research agenda forward in the CHI PLAY community. The workshop has the following objectives: Bring together an international group of researchers. Create an overview of current game-based approaches for the assessment and interventions of mental health. Discuss interests and directions for innovation. Identify overlap between research groups. Define a plan for knowledge exchange and collaboration between groups -- e.g., through internships, research visits, invited presentations, and formal and informal collaborations. Participants will have the opportunity to gain knowledge about the state of the international research community interested in game-based solutions for mental health. There will be opportunities to meet peers in different stages of their careers and discuss opportunities for future collaborations to consolidate a community in this emerging area.CHI PLAY '17: Annual Symposium on Computer-Human Interaction in Play (Amsterdam, the Netherlands, October 15 - 18, 2017

Social embodiment in directional stepping behavior

Item does not contain fulltextEmbodiment theories emphasize the role played by sensory and motor processes in psychological states, such as social information processing. Motivated by this idea, we examined how whole-body postural behaviors couple to social affective cues, viz., pictures of smiling and angry faces. We adopted a Simon-like paradigm, whereby healthy female volunteers were asked to select and initiate a forward or backward step on a force plate in response to the gender of the poser (male/female), regardless of emotion. Detailed analysis of the spatiotemporal unfolding of the body center of pressure during the steps revealed that task-irrelevant emotion had no effect on the initiation times of the steps, i.e., there was no evidence of an affective Simon effect. An unexpected finding was that steps were initiated relatively slow in response to female angry faces. This Stroop-like effect suggests that postural behavior is influenced by whether certain stimulus features match or mismatch

Videospellen: De positieve effecten

Nearly all children and adolescents play video games, with up to 99 % of boys and 94 % of girls in the United States doing so. Research into the effects of video games has almost exclusively focused on negative effects (e.g. aggression and addiction). However, a full understanding of the impact of video games requires this research to be supplemented with research into the benefits of playing video games. This is particularly important since video games have diversified in the last decade and now include more realistic, complex and social game content. In this article we aim to summarize the emerging body of research on the benefits of playing video games. We focus on four domains in which benefits may occur: cognitive, motivational, emotional, and social. Possible mechanisms are discussed that may underlie the generalization of positive effects of video games on real-world benefits. Our aim is to inspire new research into the potentially positive effects of video games on mental health and we call on intervention researchers and practitioners to put these effects to the test