Numerical non-LTE 3D radiative transfer using a multigrid method

3D non-LTE radiative transfer problems are computationally demanding, and this sets limits on the size of the problems that can be solved. So far Multilevel Accelerated Lambda Iteration (MALI) has been to the method of choice to perform high-resolution computations in multidimensional problems. The disadvantage of MALI is that its computing time scales as $\mathcal{O}(n^2)$, with $n$ the number of grid points. When the grid gets finer, the computational cost increases quadratically. We aim to develop a 3D non-LTE radiative transfer code that is more efficient than MALI. We implement a non-linear multigrid, fast approximation storage scheme, into the existing Multi3D radiative transfer code. We verify our multigrid implementation by comparing with MALI computations. We show that multigrid can be employed in realistic problems with snapshots from 3D radiative-MHD simulations as input atmospheres. With multigrid, we obtain a factor 3.3-4.5 speedup compared to MALI. With full-multigrid the speed-up increases to a factor 6. The speedup is expected to increase for input atmospheres with more grid points and finer grid spacing. Solving 3D non-LTE radiative transfer problems using non-linear multigrid methods can be applied to realistic atmospheres with a substantial speed-up.Comment: Accepted for publication by A&

Melaniserte fokale muskelforandringer hos Atlantisk laks : interaksjoner mellom infeksjon og immunitet

Atlantic salmon (Salmo salar) farming has increased rapidly in Norway over the last 50 years. However, the large-scale farming of salmon battles serious health problems. There are currently many adverse conditions threatening animal welfare and decreasing profits in the production. Among these threats are infectious diseases, some of which have been controlled with vaccination. Other infectious agents have however proved difficult to control, and therefore, the industry suffers numerous outbreaks of such diseases every year. In addition to infectious diseases, conditions affecting the quality of the end-product, such as melanised focal changes in the fillet, also known as black spots, are of major concern to the industry. The melanised focal changes were recognised as a quality problem in the beginning of the third millennium. From then on, industry representatives have complained that the changes have increased in frequency. As many as 10-50 % of the fillets at the abattoirs have been reported to be melanised, resulting in quality degradation or destruction of the fillet. The economic loss related to the condition is estimated to 0.5-1 billion NOK annually in Norway. The changes commonly occur in the cranio-ventral part of the fillet but can also be seen in other areas such as the dorsal musculature or confined to the red musculature under the skin. The condition was early on linked to vaccination and thought to emerge as the result of erroneous intra-muscular injection or displacement and storage of oil-adjuvant in the muscle. This was believed to attract immune cells including pigment-producing melano-macrophages, causing chronic myositis and focal discoloration in the musculature. The fact that melanised focal changes have never been reported in wild (un-vaccinated) Atlantic salmon supported this hypothesis. However, later studies showed that also un-vaccinated salmon could develop melanised focal changes under farming conditions. Thus, the search for other etiological causes continued which included dietary ingredients, various infectious agents, and several management-related issues. None of these factors alone have been shown to cause melanised focal changes, however, changes in feed composition and certain changes in the management have been shown to affect the prevalence and/or severity of the changes.Oppdrett av Atlantisk laks (Salmo salar) har vært i sterk vekst de siste 50 årene i Norge. Allikevel sloss næringen med alvorlige helseproblemer hos fisken. Flere tapsbringende sykdommer truer dyrevelferden og svekker fortjenesten i produksjonen. Blant de fremste truslene er de infeksiøse sykdommene. Noen av disse er godt kontrollert grunnet omfattende vaksinering, mens andre er relativt ukontrollerte, med gjentagende utbrudd hvert år. I tillegg til de infeksiøse sykdommene, er det flere kvalitetsproblemer som forringer kvaliteten på sluttproduktet, f.eks. misfargete, svarte områder i fileten, også kjent som melaninflekker eller svarte flekker. Melaninflekker ble anerkjent som et kvalitetsproblem på tidlig 2000-tall. Problemet har siden den gang økt i omfang. Så mye som 10-30 % av filetene på slakteriet rapporteres å ha melaninforandringer, hvilket resulterer i kvalitetsnedgradering eller i verste fall destruksjon. Det økonomiske tapet for norsk oppdrettsnæring relatert til melaninforandringer er estimert til mellom 0,5-1 milliard årlig. Flekkene finnes vanligvis kranio-ventralt i fileten, men kan også forekomme andre steder, som f.eks. diffust langs ryggmuskulaturen eller avgrenset til den røde muskulaturen rett under huden. Melaninflekker ble først antatt forårsaket av vaksinering, enten som et resultat av feilstikk i muskulaturen eller re-distribusjon og lagring av olje-adjuvans (vaksinehjelpestoff) i fileten. Dette ville medført en kronisk muskelbetennelse, hvor blant annet melano-makrofager blir rekruttert; en type pigment-produserende hvit blodcelle. Pigmentet i betennelsesreaksjonen er årsaken til den svarte misfargningen av fileten. Uvaksinert villaks har heller aldri blitt rapportert å ha melaninforandringer i muskulaturen, hvilket støttet hypotesen om vaksinering som årsak. I strid med hypotesen ble det senere vist at også uvaksinert laks kunne utvikle melaninflekker under oppdrettsforhold. Dermed begynte søket etter andre underliggende årsaker. Fôret som benyttes til oppdrettslaks har lenge vært mistenkt som medvirkende, men også diverse infeksiøse agens og faktorer knyttet til driftsforhold har vært undersøkt. Ingen av disse årsakene har alene vist seg å kunne forårsake melaninflekker, men endringer i fôrkomposisjonen og enkelte faktorer i driftsforhold har vist seg å påvirke frekvensen og/eller alvorlighetsgraden av flekkene.Mowi AS

Physical activity in light of affordances in outdoor environments: qualitative observation studies of 3–5 years olds in kindergarten

This article examines the characteristic of affordances of different outdoor environments, related to the influences of children’s physical activity levels. Qualitative observation studies in a Norwegian kindergarten were conducted of 3- to 5-year-olds into the natural environment and in the kindergarten’s outdoor area. An ecological approach was important from both an analytical and theoretical point of view, using concepts from Gibson’s (The ecological approach to visual perception. Houghton Mifflin Company, Bosten, 1979) theory of affordances. The concepts of affordances in an environment can explain children’s movement behaviour. The findings reveal that situations with high physical activity levels among the children are more often created in natural environments than in the kindergarten’s outdoor environment. Natural environments offer potential qualities that are a catalyst for physical activity. The study shows that certain characteristic of the physical outdoor environment are important for children’s opportunities and inspiration for physical active play. The findings also show that social possibilities and opportunities, human interactions, in the environment have the greatest influence on the duration and intensity of physically active play. The need for knowledge on physical and social opportunities in outdoor environments, educational practice and the content of outdoor time in kindergartens should be given greater attention.publishedVersio

PENGARUH DIVERSITAS DIREKSI TERHADAP PROFITABILITAS

Penelitian ini bertujuan untuk mengetahui pengaruh diversitas direksi terhadap profitabilitas yang dilihat dari masa jabat, latar belakang pendidikan dan kebangsaan. Pengamatan dilakukan terhadap 136 perusahaan yang terdaftar di Bursa Efek Indonesia (BEI) untuk periode tahun 2013-2014. Metode yang digunakan dalam penelitian ini adalah kuantitatif verifikatif. Teknik pengambilan sampel menggunakan pendekatan purposive sampling dan menghasilkan 99 perusahaan yang menjadi sampel penelitian. Teknik analisis data yang digunakan adalah model regresi data panel. Hasil pengujian menunjukkan bahwa masa jabat dan kebangsaan direksi berpengaruh terhadap profitabilitas perusahaan. Sementara itu, latar belakang pendidikan direksi tidak berpengaruh terhadap profitabilitas perusahaa

When student-activating teaching conflict with students' desire for efficiency. A communication perspective on undergraduate students' media use

acceptedVersio

Ellerman bombs and UV bursts: transient events in chromospheric current sheets

Ellerman bombs (EBs) and UV bursts are both brightenings related to flux emergence regions and specifically to magnetic flux of opposite polarity that meet in the photosphere. These two reconnection-related phenomena, nominally formed far apart, occasionally occur in the same location and at the same time, thus challenging our understanding of reconnection and heating of the lower solar atmosphere. We consider the formation of an active region, including long fibrils and hot and dense coronal plasma. The emergence of a untwisted magnetic flux sheet, injected $2.5$~Mm below the photosphere, is studied as it pierces the photosphere and interacts with the preexisting ambient field. Specifically, we aim to study whether EBs and UV bursts are generated as a result of such flux emergence and examine their physical relationship. The Bifrost radiative magnetohydrodynamics code was used to model flux emerging into a model atmosphere that contained a fairly strong ambient field, constraining the emerging field to a limited volume wherein multiple reconnection events occur as the field breaks through the photosphere and expands into the outer atmosphere. Synthetic spectra of the different reconnection events were computed using the $1.5$D RH code and the fully 3D MULTI3D code. The formation of UV bursts and EBs at intensities and with line profiles that are highly reminiscent of observed spectra are understood to be a result of the reconnection of emerging flux with itself in a long-lasting current sheet that extends over several scale heights through the chromosphere. Synthetic diagnostics suggest that there are no compelling reasons to assume that UV bursts occur in the photosphere. Instead, EBs and UV bursts are occasionally formed at opposite ends of a long current sheet that resides in an extended bubble of cool gas.Comment: 10 pages, 8 figures, accepted by A&

Dealing with increased complexity. Teachers’ reflections on the use of tablets in school

This article focuses on the emerging complexity that schools and teachers are currently addressing – a complexity that comprises one of the key characteristics of society today. The article explores how teachers in primary school experience the opportunities and challenges posed by the use of tablets in terms of implementation, learning activities and classroom management. In group interviews teachers at two Norwegian primary schools thematise these issues. We argue that there is a need to elucidate the subjective interpretations of technology if we are to understand how teachers integrate tablets in teaching. The article highlights how and why we have to develop a wider understanding of the new complexity, which can make situations in the classroom unpredictable and problematic. Although the teachers seldom consider complexity as a subject worthy of attention, it is possible to see it more indirectly in how new methods and activities are presented, but also as part of how they underline the indisputable need for well-defined classroom management. The article concludes by calling for more knowledge about teachers’ reflections on how to facilitate learning processes in the interplay between subject content, learning goals and activities, and organizational frameworks.publishedVersio

Three-dimensional modeling of the Ca II H&K lines in the solar atmosphere

CHROMIS, a new imaging spectrometer at the Swedish 1-m Solar Telescope (SST), can observe the chromosphere in the H and K lines of Ca II at high spatial and spectral resolution. Accurate modeling as well as an understanding of the formation of these lines are needed to interpret the SST/CHROMIS observations. Such modeling is computationally challenging because these lines are influenced by strong departures from local thermodynamic equilibrium, three-dimensional radiative transfer, and partially coherent resonance scattering of photons. We aim to model the CaII H&K lines in 3D model atmospheres to understand their formation and to investigate their diagnostic potential for probing the chromosphere. We model the synthetic spectrum of Ca II using the radiative transfer code Multi3D in three different radiation-magnetohydrodynamic model atmospheres computed with the Bifrost code. We classify synthetic intensity profiles according to their shapes and study how their features are related to the physical properties in the model atmospheres. We investigate whether the synthetic data reproduce the observed spatially-averaged line shapes, center-to-limb variation and compare with SST/CHROMIS images. The spatially-averaged synthetic line profiles show too low central emission peaks, and too small separation between the peaks. The trends of the observed center-to-limb variation of the profiles properties are reproduced by the models. The Ca II H&K line profiles provide a temperature diagnostic of the temperature minimum and the temperature at the formation height of the emission peaks. The Doppler shift of the central depression is an excellent probe of the velocity in the upper chromosphere.Comment: 19 pages, 20 figures, accepted for publication by A&

Ungdom og cannabis : en longitudinell kvalitativ studie om holdninger til cannabisbruk blant ungdom

Bakgrunn: Cannabis er det mest utbredte illegale rusmiddelet i bruk blant ungdom i Norge. Tidlig oppstart med cannabis er assosiert med flere negative helsekonsekvenser og sammen med en observert økning i styrkegraden i dagens cannabis, er dette av bekymring for folkehelsen. Ungdomstiden er en fase hvor grunnleggende holdninger formes og utvikles, der risikoatferd som utprøving av rusmidler ikke er uvanlig. Det blir vist til flere faktorer som kan påvirke til cannabisbruk blant ungdom. Formål: Studiens formål er å undersøke hvilke holdninger dagens ungdom i Norge har til cannabis, og hvordan disse holdningene eventuelt endrer seg fra 10. klasse på ungdomsskolen (tidspunkt ungdomsskole – TU) til 3. trinn på videregående skole (tidspunkt videregående - TV). Fremgangsmåten for å undersøke ungdommens holdninger er å identifisere de faktorer som kan påvirke holdningene. Studiens problemstilling er dermed: Hva påvirker holdningene ungdom har til bruk av cannabis, og endres holdningene fra ungdomsskolen til videregående skole? Metode: Studien har tatt i bruk kvalitativ metode, med empiri bestående av semistrukturerte individuelle intervjuer. Empirien er blitt samlet inn med en longitudinell tilnærming, med intervjuer ved to tidspunkt med de samme deltakerne. For å analysere datamaterialet ble tematisk analyse brukt innledningsvis, før det ble brukt en longitudinell analyse for å se på eventuelle forandringer og utvikling innenfor hvert tema funnet i den tematiske analysen. Resultater: Analysen førte til fem hovedtema som bidrar til å besvare problemstillingen: «Aksept til bruk», «Konsekvenser ved bruk», «Påvirkning fra miljøet», «Cannabisrusen» og «Identitet». Det ble i varierende grad observert en utvikling innenfor hvert av temaene, og gjennomgående var det noen forskjeller i holdninger blant de som selv hadde erfaring med cannabis versus de uten erfaring. Konklusjon: Det ses en utvikling fra TU til TV mot en økt aksept for bruk av cannabis sammen med en opplevelse av at det ikke er et så farlig rusmiddel. Dette viste seg både hos ungdommene med og uten egen erfaring med cannabis. Resultatene var likevel ikke ensbetydende med en økt aksept for cannabis, og det ble også vist til at holdningene til cannabis var varierende blant ungdommene.Background: Cannabis is the most widely used illegal drug among adolescents in Norway. Early initiation with cannabis is associated with several negative health consequences, which combined with an observed increase in cannabis potency makes it a public health concern. Adolescence is the phase where attitudes are formed and developed, and risk behaviors such as substance use is common. Several factors are referred to that can influence cannabis use among adolescents. Purpose: The purpose of the study was to investigate the attitudes towards cannabis among adolescents in Norway, and how these attitudes may change from 10th grade (Baseline interview - TU) to the last year of pre-university education (Follow-up interview - TV). This was done by identifying and investigate the factors influencing attitudes. The research question was: What influence adolescents’ attitudes towards cannabis, and are there any changes in the attitudes from 10th grade to the last year of pre-university education? Method: This study has used qualitative method, with empirical data consisting of semistructured individual interviews conducted through a prospective study with one follow-up. To analyze the interviews, initially thematic analysis was used, before a longitudinal analysis was used to investigate possible changes and developments within each topic found in the thematic analysis. Results: The analysis led to five main themes that contribute to answer the research question: “Acceptance of use”, “Consequences of use”, “Impact from the environment”, “Cannabis intoxication” and “Identity”. An observed evolvement was identified to various degrees within each topic, and in general there was some difference in attitudes between adolescents with personal experience of use versus the adolescents without experience. Conclusion: The findings indicate a change in the adolescents´ attitudes towards cannabis from TU to TV into an acceptance of cannabis use together with descriptions of cannabis as less harmful. This was seen both among adolescents with personal experience with cannabis and those without experience. However, the results were not equal to an increasing accept or normalization towards cannabis, and it was also pointed out that attitudes towards cannabis varied among the adolescents.M-FO