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| 2. |
- 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. |
- Bolldén, Karin, 1980-
(författare)
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Online teaching practices : Sociomaterial matters in higher education settings
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study was to describe and analyse online teaching practices in the Swedish higher education context. The study had an online ethnographic approach and was based on empirical data on the teaching in two university courses. The study rested primarily on observational data but interviews and available documents also formed the basis for analysis. Empirical data were analysed with a perspective of practice theory – a perspective within a sociomaterial account. The results showed that online teaching was characterised by an embodied sociomaterial practice. The teacher’s body could be understood as both multiple and closely interwoven with technology. Furthermore, the teacher’s body was used in the teaching situation to reduce technological complexity but also, along with other forms of materiality, to prefigure what kind of teaching would take place. Teacher interventions in online environments could furthermore be understood as relational to both technology (that is the virtual material arrangement) and teachers’ doings and sayings (that is the teaching practice). Teacher interventions were aimed at making the arrangement intelligible for the students. The study showed that teacher interventions arranged both students and information and communication technology (ICT) in order to make them work as a teaching practice. The teaching practice that emerged was characterised as an interplay between virtual materiality and social practice, where asymmetricrelations between teachers and the ICT prevailed.
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| 5. |
- Bolldén, Karin, 1980-
(författare)
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Teachers' embodied presence in online teaching practices
- 2016
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Ingår i: Studies in Continuing Education. - : Taylor & Francis. - 0158-037X .- 1470-126X. ; 38:1
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to examine teachers’ embodiments online. The analysis is based ononline ethnographic data from two online courses in higher education settings usingdifferent information and communication technologies. The perspective of practicetheory and the concepts of being a body, having a body and the instrumental body wereused to analyse how teachers step into an embodied presence. The embodied presencedepends on both teacher judgements and what the technology offers. The finding addsto the understanding of the concept of teacher presence online, in showing that teacherembodiment occurs online and furthermore that the body could be understood asmultiple. The result also shows how online and offline bodies hang together,actualising the offline body in the online setting, which in turn raises questions onthe dualism of online and offline. Teachers also deliberately used their embodimentsand bodily traces online in order to sustain presence and to bring about certain teachingpractices. Their bodily positioning signalled what kind of teaching that would takeplace. A deliberate positioning of the online body in a virtual world also helped toreduce the complexity of the arrangements for the students.
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| 6. |
- Bolldén, Karin
(författare)
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The emergence of online teaching practices : A sociomaterial analysis
- 2016
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Ingår i: Learning, Media & Technology. - : Routledge. - 1743-9884 .- 1743-9892. ; 41:3, s. 444-462
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this article was to analyse relations between online teaching practices and their virtual material arrangements. Two higher education online settings were studied using an online ethnographic approach in which observation of the teaching process was of central importance. The first setting was a course in education carried out on itslearning© (a learning management system) and the second setting was a language course in Second Life® (a virtual world). A sociomaterial perspective based on practice theory was used in the analysis, and the focal point was the co-constitutive relation between teaching practices and material arrangements in online settings. A number of relations between practice and arrangement were identified and analysed in the results section. It is argued that the relation between online arrangements and practice is not fixed and determined beforehand, but emerges and alters as the teaching unfolds.
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| 7. |
- Dienus, Olaf, et al.
(författare)
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Norovirus Dynamics in Wastewater Discharges and in the Recipient Drinking Water Source: Long-Term Monitoring and Hydrodynamic Modeling
- 2016
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 50:20, s. 10851-10858
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Tidskriftsartikel (refereegranskat)abstract
- Norovirus (NoV) that enters drinking water sources with wastewater discharges is a common cause of waterborne outbreaks. The impact of wastewater treatment plants (WWTPs) on the river Gota alv (Sweden) was studied using monitoring and hydrodynamic modeling. The concentrations of NoV genogroups (GG) I and II in samples collected at WWTPs and drinking water intakes (source water) during one year were quantified using duplex real-time reverse-transcription polymerase chain reaction. The mean (standard deviation) NoV GGI and GGII genome concentrations were 6.2 (1.4) and 6.8 (1.8) in incoming wastewater and 5.3 (1.4) and 5.9 (1.4) log(10) genome equivalents (g.e.) L-1 in treated wastewater, respectively. The reduction at the WWTPs varied between 0.4 and 1.1 log(10) units. In source water, the concentration ranged from below the detection limit to 3.8 log(10) g.e. L-1. NoV GGII was detected in both wastewater and source water more frequently during the cold than the warm period of the year. The spread of NoV in the river was simulated using a three-dimensional hydrodynamic model. The modeling results indicated that the NoV GGI and GGII genome concentrations in source water may occasionally be up to 2.8 and 1.9 log(10) units higher, respectively, than the concentrations measured during the monitoring project.
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| 8. |
- Ek, Anna, et al.
(författare)
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Physical Activity and Mobile Phone Apps in the Preschool Age: Perceptions of Teachers and Parents
- 2019
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Ingår i: JMIR mhealth and uhealth. - : JMIR Publications. - 2291-5222. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Physical activity (PA) is already beneficial at the preschool age. In many countries, young children spend most of their days in the preschool setting, making it a common arena for PA interventions. Mobile health tools are becoming increasingly popular to promote PA in different populations; however, little is known about the interest for and how the preschool setting could incorporate such a tool.OBJECTIVE:This study aimed to examine how teachers and parents perceive PA in preschool-aged children in general and their perceptions of how a mobile phone app could be used to promote PA in the preschool setting.METHODS:Semistructured interviews were conducted with 15 teachers (93%, [14/15] women, mean age 43.5 years, 47%, [7/15] with a university degree and 10 parents [91%, 9/10] women, mean age 38.9 years, all with a university degree) recruited from 2 urban preschools in central Sweden. The interviews were recorded, fully transcribed, coded, and analyzed using thematic analysis by means of an inductive approach.RESULTS:The analysis revealed 4 themes: (1) children are physically active by nature, (2) the environment as a facilitator or a barrier, (3) prerequisites of the adult world, and (4) an app in the preschool setting-challenges and possibilities. Parents and teachers perceived preschoolers as being spontaneously physically active; however, high-intensity PA was perceived as low. The PA was specifically performed during the day in the preschool. Identified facilitators of PA were access to safe and engaging outdoor environments such as forests, spacious indoor areas, and adult involvement. Adult involvement was considered especially important for children preferring sedentary activities. Identified barriers for PA were restricted indoor and outdoor space, rules for indoor activities, and lack of adult involvement because of time constraints. The teachers perceived that they had limited skills and experiences using apps in general, although they also acknowledged the increasing role of technological tools in the curriculum. Thus, the teachers expressed an interest for an app designed as a support tool for them, especially for situations when PA was limited because of perceived barriers. They suggested the app to include accessible information regarding the health benefits of PA in children linked to a library of activities for different settings and seasons. Parents suggested interactive app features including problem-solving tasks and music and dance, but not video clips as they made children passive.CONCLUSIONS:Vigorous PA was perceived as low in preschool-aged children. Future tailoring of interventions in the preschool setting should work around barriers and support facilitators to PA, especially PA of high intensity. In such work, an app could serve as a source of inspiration for PA in different ages, settings, and seasons and thus reduce environmental and structural inequalities in the preschool setting.
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| 9. |
- Escalera, Edwin, et al.
(författare)
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The production of porous brick material from diatomaceous earth and Brazil nut shell ash
- 2015
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 98, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- Diatomaceous earth was mixed with Brazil nut shell ash (BNS ash) in different amounts between 0 and 30 wt% and sintered at temperatures between 750 and 950 °C. The BNS ash contains 33 wt% K2O and 11 wt% CaO mainly in carbonate form. The addition of BNS ash into the diatomaceous earth caused significant changes of the microstructure after sintering. The BNS ash addition produces lightweight porous bricks with acceptable strength at lower sintering temperature. The best combination of strength and porosity was achieved for a mixture of 10 wt% of BNS ash in the diatomaceous earth sintered at 850 °C. The achieved high porosity was 49%, density 1.06 g/cm3, thermal conductivity 0.20 W/(m K) and the compressive strength was 8.5 MPa.
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| 10. |
- Fagher, Kristina, et al.
(författare)
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An eHealth Application of Self-Reported Sports-Related Injuries and Illnesses in Paralympic Sport : Pilot Feasibility and Usability Study
- 2017
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Ingår i: JMIR Human Factors. - Toronto, Canada : JMIR Publications. - 2292-9495. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Sport participation is associated with a risk of sports-related injuries and illnesses, and Paralympic athletes’ additional medical issues can be a challenge to health care providers and medical staff. However, few prospective studies have assessed sports-related injuries and illnesses in Paralympic sport (SRIIPS) over time. Advances in mobile phone technology and networking systems offer novel opportunities to develop innovative eHealth applications for collection of athletes’ self-reports. Using eHealth applications for collection of self-reported SRIIPS is an unexplored area, and before initiation of full-scale research of SRIIPS, the feasibility and usability of such an approach needs to be ascertained.Objective: The aim of this study was to perform a 4-week pilot study and (1) evaluate the monitoring feasibility and system usability of a novel eHealth application for self-reported SRIIPS and (2) report preliminary data on SRIIPS.Methods: An eHealth application for routine collection of data from athletes was developed and adapted to Paralympic athletes. A 4-week pilot study was performed where Paralympic athletes (n=28) were asked to weekly self-report sport exposure, training load, general well-being, pain, sleep, anxiety, and possible SRIIPS. The data collection was followed by a poststudy use assessment survey. Quantitative data related to the system use (eg, completed self-reports, missing responses, and errors) were analyzed using descriptive statistics. The qualitative feasibility and usability data provided by the athletes were condensed and categorized using thematic analysis methods.Results: The weekly response rate was 95%. The athletes were of the opinion that the eHealth application was usable and feasible but stated that it was not fully adapted to Paralympic athletes and their impairments. For example, it was difficult to understand how a new injury or illness should be identified when the impairment was involved. More survey items related to the impairments were requested, as the athletes perceived that injuries and illnesses often occurred because of the impairment. Options for description of multifactorial incidents including an injury, an illness, and the impairment were also insufficient. Few technical issues were encountered, but athletes with visual impairment reported usability difficulties with the speech synthesizer. An incidence rate of 1.8 injuries and 1.7 illnesses per 100 hours of athlete exposure were recorded. The weekly pain prevalence was 56% and the impairment contributed to 20% of the reported incidents.Conclusions: The novel eHealth-based application for self-reported SRIIPS developed and tested in this pilot study was generally feasible and usable. With some adaptation to accommodate Paralympic athletes’ prerequisites and improved technical support for athletes with visual impairment, this application can be recommended for use in prospective studies of SRIIPS.
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