| 1. |
- Alm, Love, et al.
(författare)
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MMS Observations of Multiscale Hall Physics in the Magnetotail
- 2019
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Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007.
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Tidskriftsartikel (refereegranskat)abstract
- We present Magnetospheric Multiscale mission (MMS) observations of Hall physics in the magnetotail, which compared to dayside Hall physics is a relatively unexplored topic. The plasma consists of electrons, moderately cold ions (T similar to 1.5 keV) and hot ions (T similar to 20 keV). MMS can differentiate between the cold ion demagnetization region and hot ion demagnetization regions, which suggests that MMS was observing multiscale Hall physics. The observed Hall electric field is compared with a generalized Ohm's law, accounting for multiple ion populations. The cold ion population, despite its relatively high initial temperature, has a significant impact on the Hall electric field. These results show that multiscale Hall physics is relevant over a much larger temperature range than previously observed and is relevant for the whole magnetosphere as well as for other astrophysical plasma.
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| 2. |
- Azarov, Alexander, et al.
(författare)
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Defect annealing kinetics in ZnO implanted with Zn substituting elements : Zn interstitials and Li redistribution
- 2019
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 125:7
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Tidskriftsartikel (refereegranskat)abstract
- It is known that the behavior of residual Li in ion implanted ZnO depends on the preferential localization of the implants, in particular, forming characteristic Li depleted or Li pile-up regions for Zn or O sublattice occupation of the implants due to the corresponding excess generation of Zn and O interstitials in accordance with the so-called "+1 model." However, the present study reveals that conditions for the radiation damage annealing introduce additional complexity into the interpretation of the Li redistribution trends. Specifically, four implants residing predominantly in the Zn-sublattice, but exhibiting different lattice recovery routes, were considered. Analyzing Li redistribution trends in these samples, it is clearly shown that Li behavior depends on the defect annealing kinetics which is a strong function of the implanted fluence and ion species. Thus, Li depleted and Li pile-up regions (or even combinations of the two) were observed and correlated with the defect evolution in the samples. It is discussed how the observed Li redistribution trends can be used for better understanding a thermal evolution of point defects in ZnO and, in particular, energetics and migration properties of Zn interstitials.
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| 3. |
- Bathen, M. E., et al.
(författare)
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Anisotropic and plane-selective migration of the carbon vacancy in SiC : Theory and experiment
- 2019
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 100:1
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the migration mechanism of the carbon vacancy (VC) in silicon carbide (SiC) using a combination of theoretical and experimental methodologies. The VC, commonly present even in state-of-the-art epitaxial SiC material, is known to be a carrier lifetime killer and therefore strongly detrimental to device performance. The desire for VC removal has prompted extensive investigations involving its stability and reactivity. Despite suggestions from theory that VC migrates exclusively on the C sublattice via vacancy-atom exchange, experimental support for such a picture is still unavailable. Moreover, the existence of two inequivalent locations for the vacancy in 4H-SiC [hexagonal, VC(h), and pseudocubic, VC(k)] and their consequences for VC migration have not been considered so far. The first part of the paper presents a theoretical study of VC migration in 3C- and 4H-SiC. We employ a combination of nudged elastic band (NEB) and dimer methods to identify the migration mechanisms, transition state geometries, and respective energy barriers for VC migration. In 3C-SiC, VC is found to migrate with an activation energy of EA=4.0 eV. In 4H-SiC, on the other hand, we anticipate that VC migration is both anisotropic and basal-plane selective. The consequence of these effects is a slower diffusivity along the axial direction, with a predicted activation energy of EA=4.2 eV, and a striking preference for basal migration within the h plane with a barrier of EA=3.7 eV, to the detriment of the k-basal plane. Both effects are rationalized in terms of coordination and bond angle changes near the transition state. In the second part, we provide experimental data that corroborates the above theoretical picture. Anisotropic migration of VC in 4H-SiC is demonstrated by deep level transient spectroscopy (DLTS) depth profiling of the Z1/2 electron trap in annealed samples that were subject to ion implantation. Activation energies of EA=(4.4±0.3) eV and EA=(3.6±0.3) eV were found for VC migration along the c and a directions, respectively, in excellent agreement with the analogous theoretical values. The corresponding prefactors of D0=0.54cm2/s and 0.017cm2/s are in line with a simple jump process, as expected for a primary vacancy point defect.
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| 4. |
- Davidson, N., et al.
(författare)
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Supporting self-care of adolescents with nut allergy through video and mobile educational tools
- 2017
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Ingår i: Conference on Human Factors in Computing Systems - Proceedings. - New York, NY, USA : ACM.
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Konferensbidrag (refereegranskat)abstract
- Anaphylaxis is a life-threatening allergic reaction which is rapid in onset. Adolescents living with anaphylaxis risk often lack the knowledge and skills required to safely manage their condition or talk to friends about it. We designed an educational intervention comprising group discussion around videos of simulated anaphylaxis scenarios and a mobile application containing video-based branching anaphylaxis narratives. We trialed the intervention with 36 nut allergic adolescents. At 1-year follow-up participants had improved adrenaline auto-injector skills and carriage, disease- and age-specific Quality of Life and confidence in anaphylaxis management. At 3-year follow-up adrenaline carriage improved further and confidence remained higher. Participants expressed how the education session was a turning point in taking control of their allergy and how the app facilitated sharing about anaphylaxis with others. We contribute insights regarding design of mobile self-care and peer-support applications for health in adolescence, and discuss strengths and limitations of video-based mobile health interventions.
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| 5. |
- Denton, R. E., et al.
(författare)
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Determining L-M-N Current Sheet Coordinates at the Magnetopause From Magnetospheric Multiscale Data
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:3, s. 2274-2295
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Tidskriftsartikel (refereegranskat)abstract
- We discuss methods to determine L-M-N coordinate systems for current sheet crossings observed by the Magnetospheric Multiscale (MMS) spacecraft mission during ongoing reconnection, where e(L) is the direction of the reconnecting component of the magnetic field, B, and e(N) is normal to the magnetopause. We present and test a new hybrid method, with e(L) estimated as the maximum variance direction of B (MVAB) and e(N) as the direction of maximum directional derivative of B, and then adjust these directions to be perpendicular. In the best case, only small adjustment is needed. Results from this method, applied to an MMS crossing of the dayside magnetopause at 1305:45UT on 16 October 2015, are discussed and compared with those from other methods for which e(N) is obtained by other means. Each of the other evaluations can be combined with e(L) from MVAB in a generalized hybrid approach to provide an L-M-N system. The quality of the results is judged by eigenvalue ratios, constancy of directions using different data segments and methods, and expected sign and magnitude of the normal component of B. For this event, the hybrid method appears to produce e(N) accurate to within less than 10 degrees. We discuss variance analysis using the electric current density, J, or the J x B force, which yield promising results, and minimum Faraday residue analysis and MVAB alone, which can be useful for other events. We also briefly discuss results from our hybrid method and MVAB alone for a few other MMS reconnection events. Plain Language Summary We discuss methods for determining coordinate systems in order to study magnetic reconnection events at the magnetopause, the boundary between the ionized gas in the region of space dominated by the Earth's magnetic field and the ionized gas coming from the solar wind. We introduce a new method that combines results from multiple methods in order to determine the three coordinate directions in space. We demonstrate this method by applying it to an event observed by the Magnetospheric Multiscale spacecraft on 16 October 2015 and at other times.
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| 6. |
- Dow, Andy, et al.
(författare)
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Between grassroots and the hierarchy : Lessons learned from the design of a public services directory
- 2018
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Ingår i: Conference on Human Factors in Computing Systems - Proceedings. - New York, NY, USA : ACM. - 9781450356206 - 9781450356213
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Konferensbidrag (refereegranskat)abstract
- There is a growing interest in HCI research studying technology for citizen engagement in civic issues. We are now seeing issues around technologies for empowerment and participation, long discussed in HCI literature, appropriated and formalised in government legislation. In the UK, recent reforms stipulate that community-based service information should be published in continuously updated, collaboratively designed and maintained, online platforms. We report on a qualitative study where we worked with stakeholders involved in the collaborative design, development and implementation of such a platform. Our findings highlight tensions between the grassroots desire to innovate and local governments' rigid compliance with statutory obligation. We pose a series of challenges and opportunities for HCI researchers engaged in the design of civic technologies to consider going forward, addressing issues of engagement in policy, measures of participation and tools for enabling participatory processes in public institutions. © 2018 Copyright is held by the owner/author(s).
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| 7. |
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| 8. |
- Dow, Andy, et al.
(författare)
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ThoughtCloud : Exploring the Role of Feedback Technologies in Care Organisations
- 2016
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Ingår i: 34TH ANNUAL CHI CONFERENCE ON HUMAN FACTORS IN COMPUTING SYSTEMS, CHI 2016. - New York, NY, USA : ASSOC COMPUTING MACHINERY. ; , s. 3625-3636
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Konferensbidrag (refereegranskat)abstract
- ThoughtCloud is a lightweight, situated, digital feedback system designed to allow voluntary and community sector care organisations to gather feedback and opinions from those who use their services. In this paper we describe the design and development of ThoughtCloud and its evaluation through a series of deployments with two organisations. Using the system, organisations were able to pose questions about the activities that they provide and gather data in the form of ratings, video or audio messages. We conducted observations of ThoughtCloud in use, analysed feedback received, and conducted interviews with those who 'commissioned' feedback around the value of comments received about their organisation. Our findings highlight how simple, easily deployable digital systems can support new feedback processes within care organisations and provide opportunities for understanding the personal journeys and experiences of vulnerable individuals who use these care services.
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| 9. |
- Dow, Andy, et al.
(författare)
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What Happens to Digital Feedback? : Studying the Use of a Feedback Capture Platform by Care Organisations
- 2017
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Ingår i: PROCEEDINGS OF THE 2017 ACM SIGCHI CONFERENCE ON HUMAN FACTORS IN COMPUTING SYSTEMS (CHI'17). - New York, NY, USA : ASSOC COMPUTING MACHINERY. ; , s. 5813-5825
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Konferensbidrag (refereegranskat)abstract
- In this paper we report on a four-month long field trial of ThoughtCloud, a feedback collection platform that allows people to leave ratings and audio or video responses to simple prompts. ThoughtCloud was trialled with four organisations providing care services for people with disabilities. We conducted interviews with staff and volunteers that used ThoughtCloud before, during and after its deployment, and workshops with service users and staff. While the collection of feedback was high, only one organisation regularly reviewed and responded to collected opinions. Furthermore, tensions arose around data access and sharing, and the mismatch of values between 'giving voice' and the capacity for staff to engage in feedback practices. We contribute insights into the challenges faced in using novel technologies in resource constrained organisations, and discuss opportunities for designs that give greater agency to service users to engage those that care for them in reflecting and responding to their opinions.
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| 10. |
- Fuselier, S. A., et al.
(författare)
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High-density O+ in Earth's outer magnetosphere and its effect on dayside magnetopause magnetic reconnection
- 2019
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 124:12, s. 10257-10269
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Tidskriftsartikel (refereegranskat)abstract
- The warm plasma cloak is a source of magnetospheric plasma that contain significant O+. When the O+ density in the magnetosphere near the magnetopause is >0.2 cm(-3) and the H+ density is <1.5 cm(-3), then O+ dominates the magnetospheric ion mass density by more than a factor of 2. A survey is conducted of such O+-rich warm plasma cloak intervals and their effect on reconnection at the Earth's magnetopause. The survey uses data from the Magnetospheric Multiscale mission (MMS) and the results are compared and combined with a previous survey of the warm plasma cloak. Overall, the warm plasma cloak and the O+-rich warm plasma cloak reduce the magnetopause reconnection rate by >20% due to mass-loading only about 2% to 4% of the time. However, during geomagnetic storms, O+ dominates the mass density of the warm plasma cloak and these mass densities are very high. Therefore, a separate study is conducted to determine the effect of the warm plasma cloak on magnetopause reconnection during geomagnetically disturbed times. This study shows that the warm plasma cloak reduces the reconnection rate significantly about 25% of the time during disturbed conditions.
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