1,773 research outputs found

    Plasma composition in a sigmoidal anemone active region

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    Using spectra obtained by the EIS instrument onboard Hinode, we present a detailed spatially resolved abundance map of an active region (AR)-coronal hole (CH) complex that covers an area of 359 arcsec x 485 arcsec. The abundance map provides first ionization potential (FIP) bias levels in various coronal structures within the large EIS field of view. Overall, FIP bias in the small, relatively young AR is 2-3. This modest FIP bias is a consequence of the AR age, its weak heating, and its partial reconnection with the surrounding CH. Plasma with a coronal composition is concentrated at AR loop footpoints, close to where fractionation is believed to take place in the chromosphere. In the AR, we found a moderate positive correlation of FIP bias with nonthermal velocity and magnetic flux density, both of which are also strongest at the AR loop footpoints. Pathways of slightly enhanced FIP bias are traced along some of the loops connecting opposite polarities within the AR. We interpret the traces of enhanced FIP bias along these loops to be the beginning of fractionated plasma mixing in the loops. Low FIP bias in a sigmoidal channel above the AR's main polarity inversion line where ongoing flux cancellation is taking place, provides new evidence of a bald patch magnetic topology of a sigmoid/flux rope configfiuration.Comment: For on-line animation, see http://www.mssl.ucl.ac.uk/~db2/fip_intensity.gif. Accepted by Ap

    Expansion of magnetic clouds in the outer heliosphere

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    A large amount of magnetized plasma is frequently ejected from the Sun as coronal mass ejections (CMEs). Some of these ejections are detected in the solar wind as magnetic clouds (MCs) that have flux rope signatures. Magnetic clouds are structures that typically expand in the inner heliosphere. We derive the expansion properties of MCs in the outer heliosphere from one to five astronomical units to compare them with those in the inner heliosphere. We analyze MCs observed by the Ulysses spacecraft using insitu magnetic field and plasma measurements. The MC boundaries are defined in the MC frame after defining the MC axis with a minimum variance method applied only to the flux rope structure. As in the inner heliosphere, a large fraction of the velocity profile within MCs is close to a linear function of time. This is indicative of} a self-similar expansion and a MC size that locally follows a power-law of the solar distance with an exponent called zeta. We derive the value of zeta from the insitu velocity data. We analyze separately the non-perturbed MCs (cases showing a linear velocity profile almost for the full event), and perturbed MCs (cases showing a strongly distorted velocity profile). We find that non-perturbed MCs expand with a similar non-dimensional expansion rate (zeta=1.05+-0.34), i.e. slightly faster than at the solar distance and in the inner heliosphere (zeta=0.91+-0.23). The subset of perturbed MCs expands, as in the inner heliosphere, at a significantly lower rate and with a larger dispersion (zeta=0.28+-0.52) as expected from the temporal evolution found in numerical simulations. This local measure of the expansion also agrees with the distribution with distance of MC size,mean magnetic field, and plasma parameters. The MCs interacting with a strong field region, e.g. another MC, have the most variable expansion rate (ranging from compression to over-expansion)

    Monolithically integrated heterodyne optical phase-lock loop with RF XOR phase detector

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    We present results for an heterodyne optical phase-lock loop (OPLL), monolithically integrated on InP with external phase detector and loop filter, which phase locks the integrated laser to an external source, for offset frequencies tuneable between 0.6 GHz and 6.1 GHz. The integrated semiconductor laser emits at 1553 nm with 1.1 MHz linewidth, while the external laser has a linewidth less than 150 kHz. To achieve high quality phase locking with lasers of these linewidths, the loop delay has been made less than 1.8 ns. Monolithic integration reduces the optical path delay between the laser and photodiode to less than 20 ps. The electronic part of the OPLL was implemented using a custom-designed feedback circuit with a propagation delay of similar to 1 ns and an open-loop bandwidth greater than 1 GHz. The heterodyne signal between the locked slave laser and master laser has phase noise below. 90 dBc/Hz for frequency offsets greater than 20 kHz and a phase error variance in 10 GHz bandwidth of 0.04 rad(2). (C) 2011 Optical Society of Americ

    Stellar Iron Abundances at the Galactic Center

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    We present measurements of [Fe/H] for six M supergiant stars and three giant stars within 0.5 pc of the Galactic Center (GC) and one M supergiant star within 30 pc of the GC. The results are based on high-resolution (lambda / Delta lambda =40,000) K-band spectra, taken with CSHELL at the NASA Infrared Telescope Facility.We determine the iron abundance by detailed abundance analysis,performed with the spectral synthesis program MOOG.The mean [Fe/H] of the GC stars is determined to be near solar,[Fe/H] = +0.12 ±\pm 0.22. Our analysis is a differential analysis, as we have observed and applied the same analysis technique to eleven cool, luminous stars in the solar neighborhood with similar temperatures and luminosities as the GC stars. The mean [Fe/H] of the solar neighborhood comparison stars, [Fe/H] = +0.03 ±\pm 0.16, is similar to that of the GC stars. The width of the GC [Fe/H] distribution is found to be narrower than the width of the [Fe/H] distribution of Baade's Window in the bulge but consistent with the width of the [Fe/H] distribution of giant and supergiant stars in the solar neighborhood.Comment: 41 pages, 9 figures, ApJ, in pres

    Teaching Threshold Concepts in Virtual Reality: Exploring the Conceptual Requirements for Systems Design.

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    In a complex world students need to be equipping with a range of capabilities that will enable them to be critical and flexible learners and citizens. The central research objective in this paper is to explore the argument that virtual reality (VR) technologies, collaborative learning approaches and recognition of the values and importance of thresholds to learning are components that can equip students in and for the future. Threshold concepts are specific concepts which are identified as essential in the acquisition of thinking, learning and communication of understanding within a specific subject of learning. Threshold experiences occur when learners identify moments of “learning leaps” which are cognitive transformations or changes in conceptual role for the learner, enabling them to work at higher levels of abstraction and creativity. Virtual reality technology is increasingly applied in education and can be used to test multiple threshold concepts and applied to open problems that allow for low-stress and real-time interactions as well as supporting collaborative groups with rapid interactions. Applications built on VR can engage, immerse, and guide learners in ways not yet undertaken in the education of threshold concepts. Through literature review we explore the definitions of threshold concepts, VR technologies, and the opportunities for teaching threshold concepts using VR technologies. We additionally predict possible limitations of the technologies. Further, we propose a systems design approach as informed by our literature review

    Educating professionals to support self-management in people with asthma or diabetes: protocol for a systematic review and scoping exercise

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    This report is independent research funded by the National Institute for Health Research (Programme Development Grants, Implementing supported asthma self-management in routine clinical care: designing, refining, piloting and evaluating a whole systems implementation within an MRC Phase IV programme of research, RP-DG-1213-10008). The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health. This work is sponsored by the University of Edinburgh. The funder and sponsor have not had any role in developing the protocol

    Integrating Rocketbox Avatars with the Ubiq Social VR platform

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    Having a truly ethical, unbiased technology, requires people devel-oping and using this technology to have an equal opportunity to participate in its creation. In this sense, open-access tools are a way to share best practices and enhance collaboration. In this paper, we will present the integration of the Microsoft Rocketbox avatar library into the Unity networking library Ubiq. We will see how they may contribute to the research in the field of populated virtual environments

    The Influence of Avatar Realism and Similarity in Shaping Group Dynamics in Collaborative Virtual Environments

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    Given the increasing use of social virtual reality applications, it is crucial to understand the impact of avatar design on social dynamics in populated virtual environments. This study investigates the impact of avatar realism and avatar similarity on dyadic relationships, with participants embodying either cartoony or realistic avatars. Participants interact with counterparts using the same or opposite avatar type, resulting in three conditions across pairs: realistic avatars group, cartoony avatars group, and mixed avatars group (one using a realistic avatar, the other a cartoony avatar). Through collaboration on puzzle tasks designed to foster interaction and cooperation, participants' experiences are assessed using a blend of questionnaires and behavioural metrics. The findings suggest that dyads perform better at collaborative tasks in the realistic avatars group condition, while the mixed avatars group outperforms the cartoony avatars group. These results provide valuable insights for optimizing avatar design and avatar similarity to enhance collaborative virtual environments
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