Opin visindi
Not a member yet
2982 research outputs found
Sort by
Charge and heat transport in semiconductor core-shell nanowires with temperature bias
Get PDFIn this dissertation, we calculate the electronic charge and heat transport generated by a temperature gradient and a chemical potential bias in tubular semiconductor nanowires, in the presence of a magnetic field. We use the Landauer-Büttiker approach to calculate charge current, electronic heat current, Seebeck coefficient, thermal conductivity, and figure of merit. We also study the influence of the crosssection shape and shell thickness on the electronic conduction properties of tubular nanowires. Then, charge and heat transport in tubular nanowires for different polygonal cross-sections and different numbers of impurities with various strengths are studied. Effects of transverse geometry on the thermal conductivity of Si and Ge nanowires are investigated by using molecular dynamics simulations with the LAMMPS software. We consider nanowires with different polygonal cross-sections, tubular (hollow) nanowires, and core/shell nanowires with combinations of Si/Ge and Ge/Si. We also study the diffusion and phonon drag thermopower in Si nanowires through numerical calculations with tight-binding models and quantum transport
Policy on school autonomy over curriculum development - A case study of four upper secondary schools in Iceland
No full textThis thesis explores the policy on increased school autonomy over curriculum development in upper secondary schools in Iceland which was introduced in 2008. The main arguments for the establishment of the policy were the need for more diverse study due to societal changes and the growing numbers of students entering upper secondary schools after completing compulsory education. The aim of this study is to increase understanding of how this policy has been understood and enacted by school stakeholders and what they believe it has accomplished for students. A multiple case study of four schools was designed to explore the implications of the policy, both within the context of each school and also across the schools. Two main sources of data are used: interviews as the primary source and documents to provide contextual data on the schools and support evidence gathered from the interviews. The schools were visited in 2018 and interviews were conducted with school leaders, teachers, students and parents.
The study demonstrates how the interplay between a range of contextual factors influenced the way each school perceived their scope and ability to utilise the policy to make changes, notably divided professional beliefs, financial challenges and barriers, and the impact of students’ choice. Findings reveal a disparity between what school leaders and teachers expected from the policy and what they experienced when enacting it in their local context. This was largely due to the impact of other policy initiatives, notably the shortening of the study time for matriculation, increased bureaucracy, and more complex administration. These created challenges for school leaders as managers of change, particularly in relation to the policy’s impact on teachers’ job security. In terms of the stated aim of the policy and what has been accomplished for students, evidence of greater diversity of study was identified, but this varied considerably between schools and across subjects, demonstrating the importance of understanding the policy effects in relation to the specific context of each school. While students reported that greater flexibility and moves away from summative assessments had created study better suited to their needs, barriers to equal access to study remain, due to academic, geographical and demographic constraints. The study concludes by providing recommendations for policy development and suggesting that further measures are required if the policy and students’ choice are to function together effectively in the Icelandic context.Í þessari rannsókn er sjónum beint að stefnu um aukið sjálfstæði framhaldsskóla á
Íslandi yfir þróun námskrár. Meginrökin fyrir setningu stefnunnar árið 2008 voru aukin
þörf fyrir fjölbreytt nám vegna samfélagslegra breytinga og vaxandi fjöldi nemenda sem
fer í framhaldsskóla eftir að hafa lokið grunnskóla. Markmið rannsóknarinnar er að auka
skilning á því hvernig þessi stefna hefur verið skilin og framkvæmd af hagsmunaðilum
skóla og hverju hún er talin hafa áorkað fyrir nemendur. Tilviksrannsókn í fjórum
framhaldsskólum var hönnuð til að rannsaka áhrif stefnunnar bæði með hliðsjón af
aðstæðum hvers skóla og með samanburði milli skóla. Tvær meginuppsprettur gagna
eru notaðar: viðtöl sem frumheimildir og ritaðar heimildir til að lýsa skólum og
aðstæðum þeirra og styðja við gögn úr viðtölum. Skólarnir voru heimsóttir árið 2018
og viðtöl tekin við stjórnendur, kennara, foreldra og nemendur.
Rannsóknin sýnir hvernig samspil margvíslegra aðstæðubundinna þátta hafði áhrif á
hvernig skólarnir skynjuðu svigrúm sitt og getu til að nýta stefnuna til að gera
breytingar. Í þessu samhengi höfðu einkum áhrif skiptar faglegar skoðanir,
fjárhagslegar áskoranir og hindranir og val nemenda. Niðurstöður sýna misræmi milli
væntinga stjórnenda og kennara til stefnunnar og þess sem þeir upplifðu þegar kom að
framkvæmd stefnunnar í staðbundnu samhengi. Þetta tengdist að miklu leyti áhrifum frá
öðrum stefnuáherslum sem voru í gangi á sama tíma, einkum styttingu á námstíma til
stúdentsprófs, auknu skrifræði og flóknari stjórnsýslu. Framkvæmd stefnunnar
framkallaði áskoranir í starfi leiðtoga skóla sem stjórnendur breytinga, sérstaklega í
tengslum við áhrif stefnunnar á starfsöryggi kennara. Með hliðsjón af yfirlýstum
markmiðum stefnunnar og hverju hún hefur áorkað fyrir nemendur þá eru vísbendingar
um að fjölbreytni náms hafi aukist en að áhrifin séu mismunandi milli skóla og milli
námsgreina, sem dregur fram mikilvægi þess að skilja áhrifin í tengslum við sérstakar
aðstæður hvers skóla. Þrátt fyrir að nemendur hafi greint frá því að aukinn sveigjanleiki
og áhersla á símat í stað lokaprófa hafi leitt til þess að námið henti þörfum þeirra betur,
þá finnast enn hindranir fyrir jöfnu aðgengi að námi sem tengjast árangri í bóknámi og
landfræðilegum og lýðfræðilegum takmörkunum. Í tengslum við niðurstöður rannsóknar
eru lagðar fram tillögur er varða þróun á stefnunni. Jafnframt er dregin sú ályktun að
frekari aðgerða sé þörf ef stefnan um sjálfstæði skóla og skólaval eigi að geta virkað
saman á árangursríkan hátt með hliðsjón af staðbundnum aðstæðum á Íslandi
Platform for decoupling experience managers and environments
Get PDFExperience Management employs Artificial Intelligence technologies to enhance people's interactive application experiences by dynamically modifying the environment during the experience. In game-related research, there is a prevailing trend where each experience manager is tightly integrated with the specific environment it can manipulate. This integration poses a challenge in comparing different managers within a single environment or a single manager across multiple environments.
In this dissertation, I propose a solution to address this issue by introducing EM-Glue, an intermediary software platform that decouples experience managers from the environments they can modify. Prior to presenting the solution, I provide a comprehensive problem description and conduct a literature review to explore the current state of the field. Subsequently, I outline the platform's structural design, including a communication protocol facilitating interaction between managers and environments, as well as the regular communication process.
Additionally, I develop a use case to evaluate the effectiveness of the proposed solution. This involves employing an environment and two experience managers: the Camelot Wrapper, a software I constructed to extend the interactive visualization engine Camelot and connect it to the platform, PaSSAGE, an existing experience manager adapted for use with the platform, and a random experience manager. The evaluation results demonstrate the platform's ability to decouple experience managers from environments, enabling future work to compare experience managers across multiple environments
Samfélagslungnabólga meðal fullorðinna: Rannsóknir á völdum þáttum sem tengjast horfum og lifun
Get PDFInngangur. Þrátt fyrir að næstum öld sé liðin frá uppgötvun penisillíns og að langt sé liðið síðan bólusetningar hófust gegn Streptococcus pneumoniae (pneumokokkum), algengasta orsakavaldi lungnabólgu fullorðinna, er enn um algengan og alvarlegan sjúkdóm að ræða. Með hækkandi aldri verður greining lungnabólgu oft erfiðari; einkenni verða gjarnan ósértækari, erfiðara er að ná góðum myndum af lungum og lengri tíma getur tekið fyrir íferðir í lungum að verða sýnilegar á myndrannsókn. Þrátt fyrir þetta er skortur á rannsóknum sem bera saman þá sem eru með klínísk einkenni lungnabólgu en án greinilegra íferða á lungnamynd við hina sem eru með samfélagslungnabólgu (klínísk einkenni ásamt staðfestri íferð á lungnamynd). Sumar fyrri rannsóknir hafa bent til þess að gjöf asetýlsalicýlsýru (ASA) geti dregið úr dauðsföllum í kjölfar lungnabólgu en aðrar ekki. Meinvaldar lungnabólgu geta skyndilega breyst eins og gerðist í heimsfaraldri SARS-CoV-2 og mikilvægt að bregðast við og lýsa nýjum sjúkdómum, s.s. þeim sem meinvaldurinn veldur, áhættuþáttum og mögulegri meðferð. Upplýsingar skortir um tengsl kæfisvefns við tilurð alvarlegar COVID-19 lungnabólgu, þar sem margir áhættuþættir sjúkdómanna eru sameiginlegir er mikilvægt að leiðrétta fyrir þeim.
Markmið. Í fyrsta lagi að bera saman tilfelli með klínísk einkenni lungnabólgu en án greinilegra íferða við tilfelli samfélagslungnabólgu með sérstaka áherslu á dánartíðni (Grein I). Í öðru lagi að kanna hvort ASA tengdist bættri lifun tilfella sem greindust með pneumokokkalungnabólgu (Grein II). Í þriðja lagi að kanna hvort kæfisvefn tengdist alvarlegri COVID-19 lungnabólgu (Grein III).
Efni og aðferðir. Þrjú aðskilin gagnasöfn voru notuð. Í fyrsta lagi var gögnum safnað um tilfelli sem lögðust inn með grun um lungnabólgu á framskyggnan máta á eins árs tímabili 2018-2019 (grein 1). Í öðru lagi var notast við afturskyggnt gagnasafn allra staðfestra ífarandi pneumókokkasýkinga 1975-2019 á Íslandi. Í þriðja lagi var gagnasafn um öll tilfelli með COVID-19 á Íslandi árið 2020 notað og upplýsingar frá Landspítala um kæfisvefnstilfelli.
Grein 1. Lógistísk aðhvarfsgreining var notuð til að meta dánartíðni við 30 daga eftir leiðréttingu fyrir aldri, kyni, Charlson stigun á sjúkdómsbyrði og fyrir 1 árs dánartíðni var einnig leiðrétt fyrir reykingum, búsetu á hjúkrunarheimili og tilvist meðferðartakmarkana. Framkvæmdar voru endurteknar tilreiknanir á gagnaeyðum, í 8.5% tilfella vantaði upplýsingar um reykingar.
Grein 2. Öll tilfelli 1975-2019 á Íslandi sem höfðu jákvæða blóðræktun með S. pneumoniae og staðfesta lungnabólgu samkvæmt myndrannsókn af lungum voru í rannsóknarhópnum. Aðalsamanburðurinn fólst í að bera saman lifun við 30-daga, 90-daga og 1-ár með því að notast við líkindaskorsvigtun, eftir því hvort sjúklingarnir voru að taka ASA við greiningu sýkingarinnar.
Grein 3. Öll tilfelli sem greindust með COVID-19 á árinu 2020 voru í úrtakinu, tilfelli sem höfðu farið í svefnskimun og reyndust með ≥5 öndunarhlé á mínútu voru skilgreind sem kæfisvefnstilfelli. Endapunktur rannsóknarinnar var dauði eða sjúkrahúsinnlögn. Framkvæmdar voru lógistískar aðhvarfsgreiningar og líkindaskorsvigtun, fyllt var í gagnaeyður með endurteknum tilreikningum.
Niðurstöður.
Grein 1. Klínísk einkenni lungnabólgu en án greinilegra íferða var um helmingi óalgengari innlagnarástæða en samfélagslungnabólga. Tilfelli með samfélagslungnabólgu voru líklegri til að mælast með hækkaðan líkamshita, hærra CRP, greinast með S. pneumoniae og að fá sýklalyfjameðferð en ólíklegri til að greinast með sýkingu af völdum öndunarfæraveira. Leiðrétt líkindahlutfall dauða þeirra sem voru með klínísk einkenni lungnabólgu en án íferða miðað við þá sem voru með samfélagslungnabólgu innan 30 daga var 0.86 (95% öryggisbil (ÖB) 0.40-1.85) en 1.25 (95% ÖB 0.81-1.95) við 1 ár.
Grein 2. Tilfellin sem voru að taka ASA við innlögn voru ólík tilfellum sem voru ekki að taka lyfið þegar undirliggjandi sjúkdómar, reykingar, áfengisfíkn og aldur voru skoðuð. Ásættanleg leiðrétting náðist með líkindaskorsvigtun. ASA tilfelli höfðu betri lifun á tímabilinu 0-7 dögum eftir sýkingu (Hættuhlutfall (HH), 0.42, 95% CI 0.19-0.92), en ekki milli 7-30 daga eftir greiningu (HH 1.08, 95% CI 0.46-2.55). Meðal HH yfir 1 ár sýndi betri lifun ASA tilfella en þeirra sem ekki voru á lyfinu (HH 0.48, 9%CI 0.31-0.75).
Grein 3. COVID-19 tilfelli sem höfðu kæfisvefn voru líklegri til að þurfa innlögn eða deyja en tilfelli sem voru með COVID-19 en ekki kæfisvefn í fullleiðréttu módeli (2.0 95% CI 1.2-3.2). Áhrifin voru sterkari í minna leiðréttum módelum. Næmisgreiningar sýndu svipuð áhrif.
Ályktanir. Klínísk einkenni lungnabólgu án íferða er algeng ástæða innlagna og þrátt fyrir að íferð sjáist ekki við myndrannsókn var dánartíðnin ekki marktækt lægri. Notkun á ASA tengist lægri dánartíðni þeirra sem greinast með ífarandi pneumókokkalungnabólgu en þörf er á rannsóknum sem leiðrétta fyrir mögulegri skekkju heilbrigðari notenda. Kæfisvefn er áhættuþáttur fyrir sjúkrahúsinnlögn eða dauða meðal þeirra sem greinast með COVID-19 að teknu tilliti til bjögunarþátta.Abstract
Introduction. Despite almost a century passing since the discovery of
penicillin and many years since the initiation of vaccinations against
Streptococcus pneumoniae, this principal cause of pneumonia among adults,
pneumonia is still a common and serious disease. Increasing age often
complicates the diagnosis of pneumonia with fewer specific symptoms,
difficulty obtaining radiographs of sufficient quality and sometimes a lag in
infiltrates becoming visible. Studies are lacking comparing cases that have
symptoms of pneumonia without radiographic confirmation of an infiltrate
(SPWI) with those that have symptoms of pneumonia with radiographic
confirmation (community-acquired pneumonia, CAP). Some earlier studies
indicated that acetylsalicylic acid (ASA) decreased mortality following
pneumonia, but others did not. Pneumonia etiology can suddenly change, as
observed recently in the SARS-CoV-2 pandemic, highlighting the importance
of timely studies on new or re-emerging pathogens and diseases, risk factors
and possible treatments. Information is lacking on the association of
obstructive sleep apnea (OSA) with severe COVID-19.
Goals. The first goal was to compare clinical characteristics and mortality of
SPWI cases to CAP cases (Paper I). Secondly, to examine if ASA was
associated with improved survival among those with invasive pneumococcal
pneumonia (Paper II). Lastly, to assess if OSA was associated with severe
COVID-19 pneumonia (Paper III).
Methods. Three different datasets were used. In the first paper we performed
a prospective study on cases hospitalized with suspected pneumonia over a
one-year period (2018-2019). In the second paper we used a retrospective
dataset on all invasive pneumocccal infections 1975-2019 in Iceland. In the
third paper we used a dataset on all COVID-19 infections in Iceland in the year
2020 and information on cases from a sleep study from Landspitali- The
National University Hospital of Iceland (LUH).
Paper 1. For analysis of mortality at 30 days logistic regression was used
adjusting for age, sex and Charlson comorbidity index (CCI); for the 1-year
outcome analysis, do not resuscitate directive, smoking, and nursing home
residence were added. Multiple imputations were performed on missing data.
iv
Paper 2. All adult cases in Iceland 1975-2019 with a positive blood culture for
S. pneumoniae along with symptoms and signs of pneumonia were included.
The main outcome was survival at 30 and 90 days and at 1 year comparing
those using ASA to those not using ASA, using Cox regression with inverse
probability weighting for covariate adjustment.
Paper 3. All cases with a COVID-19 diagnosis in 2020 were included, cases
with an apnea-hypopnea index (AHI) ≥ 5 per minute were defined as OSA. A
combined outcome of hospitalization or death was used as the main outcome.
Logistic regression and propensity score weighting were used for adjustment,
multiple imputations were performed on missing data.
Results
Paper I. The incidence of SPWI requiring hospital admission was one half of
that of CAP. CAP cases more frequently had fever (≥38°C), higher CRP value,
S. pneumoniae as microbial etiology and more frequently received antibiotic
therapy, but cases in the CAP group less frequently had a respiratory virus
identified. The adjusted odds of mortality for SPWI cases compared with CAP
within 30 days was 0.86 (95% confidence interval (CI) 0.40-1.85) but1.25 (95%
CI 0.81-1.95) at 1 year.
Paper II. There were differences between the groups taking ASA or not in
terms of underlying illnesses, smoking, alcoholism, and age. After propensity
score weighting an accepatable balance was reached. After adjustment, ASA
cases had a better survival 0-7 days after diagnosis (HR 0.42, 95% CI 0.19-
0.92), but not between 7-30 days (1.08 95% CI 0.46-2.55). Average HR over
1-year showed a better survival for the ASA cases compared to those not on
ASA (HR 0.48, 9%CI 0.31-0.75).
Paper III. COVID-19 cases with OSA were more likely to need hospitalization
or die than cases that had COVID-19 but without a prior OSA diagnosis in a
fully adjusted model (2.0 95% CI 1.2-3.2). The association was stronger in
models which adjusted for fewer comorbidities. The effects held in sensitivity
analyses.
Conclusion. SPWI is a common reason for hospitalization and despite lacking
radiographic infiltrates, mortality was not much lower than in CAP. The use of
ASA is associated with lower mortality among those diagnosed with invasive
pneumococcal pneumonia, but studies adjusting for healthy user bias are
needed. OSA is a risk factor for hospitalization or death among those
diagnosed with COVID-19.• The Icelandic Centre for Research (Rannís, grant number 217716-051)
• The Doctoral Grants of The University of Iceland Research Fund
• The Scientific Fund of Landspitali—The National University Hospital of Iceland
• The Scandinavian Society for Antimicrobial Chemotherapy Foundation (SSAC
Foundation)
• The Foundation of St. Josef´s Hospital
• The Geriatric council of Iceland (Öldrunarráð Íslands
Endurmat á hlutverki háskólastigsins: Greining á þriðja hlutverki háskóla á Íslandi
No full textThis study revolves around Third Mission (TM) activities in Iceland and the factors
that influence the development of such activities within a small economy. In the
context of higher education institutions, TM can be seen as a socio-economic
mission of a university, which comes after the first mission of teaching and the
second mission of research.
The objective of the study is to provide recommendations for universities on how to
achieve the TM best practices that will foster the more traditional missions within
academia by analysing collaboration patterns and socio-economic engagement. The
data derive from a literature review, semi-structured interviews, and a population
survey.
The findings reveal a general lack of TM activities caused by shortages of time,
incentives, networks, and resources such as financial means, but a general
optimism and willingness to participate more are also present. Overall, TM activities
in the form of direct exploitation of research through contract research or
commercialisation are very limited among academics in Iceland. There are hardly
any differences between universities regarding the aforementioned results, but TM
activities are influenced by the type of discipline, publication performance, work
experience, and personality traits such as openness.
Based on these outcomes, the main recommendation drawn from this study is that
TM activities – including those that have so far been less considered or recognised
even though they often have the potential to yield societal impact in the long-term –
be acknowledged more. Additionally, universities should adopt appropriate
assessment and incentive systems to support TM, change recruitment guidelines so
a more diverse academic staff can be hired, establish interdisciplinary networks,
and incorporate TM into the first two missions of research and teaching. However,
for this to work, greater financial resources are needed.Þessi rannsókn fjallar um þriðja hlutverk háskóla á Íslandi og þá þætti sem hafa
áhrif á slíkt hlutverk í litlu hagkerfi. Líta má á þriðja hlutverkið sem
frumkvöðlastarfsemi háskóla, þegar fyrsta hlutverkið er kennsla og annað hlutverk
eru rannsóknir.
Í rannsókninni er samstarfsmynstur háskóla, fyrirtækja og stofnana greint sem og
félagsleg og efnahagsleg þátttaka háskólakennara. Stuðst er við hálf-stöðluð viðtöl,
spurningalistakönnum og fræðilegt yfirlit. Niðurstöður eru notaðar til að veita
háskólum ráð til að efla og styðja við þriðja hlutverkið.
Niðurstöður sýna almennt að þriðja hlutverk háskóla er mjög takmarkað meðal
háskóla á Íslandi og stafar það af tímaskorti, lítilli hvatningu, takmörkuðu tengslaneti
og skorti á fjármagni. Mjög lítill munur er á milli háskóla í þeim efnum, en nokkur
munum er á milli fræðigreina, starfsheita í háskóla og persónuleikaeinkennum.
Á grundvelli þessara niðurstaðna eru mótaðar tillögur til háskóla um að efla þriðja
hlutverkið sem svo aftur hefur möguleika á að efla samfélagsleg áhrif háskóla til
lengra tíma litið. Að auki ættu háskólar að taka upp viðeigandi mats- og hvatakerfi
til að styðja við þriðja hlutverkið, breyta ráðningarreglum til að ráða starfsfólk með
ólíka hæfileika, koma á þverfaglegu tengslaneti og tengja þriðja hlutverkið
við rannsóknir og kennslu. Til að svo megi verða þarf meira fjármagn til háskóla.
Að lokum er í doktorsritgerðinni lögð áhersla á mikilvægi virkrar félagslegrar- og
efnahagslegrar þátttöku fræðimanna á öllum fræðasviðum. Þáttur í því er að gera
þriðja hlutverkið sýnilegra innan og utan háskóla og taka tillit til slíkrar starfsemi í
hvata- og matskerfi háskóla. Með því vekur rannsóknin athygli á mikilvægi þess
að háskólar ræki frumkvöðlahlutverk sitt
Einstaklingsmunur á sjónrænum hlutakennslum: Rannsókn á fólki með og án taugaþroskaraskana
No full textThis thesis probes the intricate nature of visual object recognition, especially how visual recognition skills are associated or dissociated in developmental disorders and the neurotypical population. Our primary areas of focus include the role of object types, the importance of visual expertise, and the impact of visual working memory.
In our investigation into developmental dyslexia, we discovered that some dyslexic readers struggled with recognizing houses, but did not face the same challenges with face recognition. This finding raises doubt about the commonly held belief that dyslexia only pertains to reading difficulties. Furthermore, our subsequent research with the neurotypical population solidified the idea that recognizing faces is fundamentally different from recognizing pseudowords or houses. Intriguingly, we found that dyslexic readers tend to adopt a unified strategy for processing visual objects, regardless of whether the task centers on an object's individual features or its overall configuration. In contrast, typical readers appeared to adjust their approach based on both featural and configural information. Yet, this differentiation was less pronounced in our second study with the neurotypical population, suggesting the potential influence of task demands on visual processing methods.
Our third study sought to understand the influence of visual working memory on these recognition patterns. We pinpointed a notable connection between visual working memory precision for simple visual elements and the ability to recall the overall structure of houses. As this connection was not found to the same degree for objects of expertise, such findings imply that familiarity with an object can potentially lessen the strain on visual working memory. This connection, however, was not present when memorizing the specific features of houses, indicating that recalling the overall structure might place more demands on memory due to the combined need to remember individual features and their relative positions. Upon revisiting our initial findings, we hypothesize that the challenges dyslexic readers face in recognizing houses might be related to their visual working memory capacities.
To conclude, this research sheds valuable light on the multifaceted nature of visual object recognition, highlighting its complexities, the role of expertise, and the contributions of visual working memory. Our conclusions enhance our understanding of visual recognition processes in both typical individuals and those with developmental challenges.Þessi ritgerð snýst um sjónræn hlutakennsl, þá sérstaklega hvort og þá hvernig tilteknir
slíkir hæfileikar tengjast innbyrðis, annars vegar hjá fólki með taugaþroskaraskanir og
hins vegar í almennu þýði. Við rannsökum áhrif hlutagerðar, reynslu og sjónræns
vinnsluminnis.
Samkvæmt rannsókn okkar á lesblindu á sumt lesblint fólk erfitt með að bera kennsl á hús
en á ekki í sams konar erfiðleikum með að þekkja andlit. Þetta gengur gegn þeirri
hugmynd að lesblinda sé aðeins bundin við erfiðleika í lestri. Frekari rannsókn okkar á
almennu þýði ýtir enn frekari stoðum undir þá hugmynd að andlitskennsl séu í
grundvallaratriðum ólík því að bera kennsl á orðleysur eða hús. Áhugavert var að
lesblindir virtust nota sams konar aðferð í hlutaskynjun hvort sem um var að ræða einstaka
sjónræna þætti hluta eða tengsl þátta, á meðan ólesblint fólk virtist beita ólíkum aðferðum
eftir því hvort þættir eða tengsl þátta skiptu máli í hlutakennslum. Þessi munur á þáttum
og tengslum var ekki jafngreinilegur í seinni rannsókn okkar á almennu þýði sem getur
bent til að mismunandi verkefni geti kallað á ólíkar sjónskynjunaraðferðir.
Þriðja rannsókn okkar fjallaði um áhrif vinnsluminnis á sjónræn kennsl. Nákvæmni í
vinnsluminni fyrir einfalda sjónræna þætti tengdist sérstaklega getu fólks til þess að muna
uppbyggingu húsa. Þar sem slík tengsl voru veikari við hæfileika fólks til þess að muna
sérfræðihluti bendir það til þess að fyrri þekking á hlutum geti minnkað álag á sjónrænt
vinnsluminni. Ekki voru jafnsterk tengsl á milli vinnsluminnis og þess að muna einstaka
sjónræna þætti húsa. Þetta gæti þýtt að það að muna uppbyggingu hluta auki minnisálag
þar sem það krefst þess að fólk leggi á minnið bæði einstaka sjónræna þætti og innbyrðis
afstöðu þeirra. Í ljósi þessara niðurstaðna getur verið að vandkvæði lesblindra við að
þekkja hús í sjón tengist sjónrænni vinnsluminnisgetu þeirra.
Þessar rannsóknir auka skilning okkar á flóknu eðli sjónrænna hlutakennsla, bæði hjá fólki
með og án taugaþroskaraskana, og sýna fram á áhrif reynslunnar og þátt sjónræns
vinnsluminnis í því að þekkja hluti í sjón.
Lykilorð:
Lesblinda; Andlitskennsl; Hlutakennsl; Orðakennsl; Sjónrænt vinnsluminniThe Icelandic Research Fund (Grant No.174013-051), the University of Iceland Research Fund, and the University of Iceland Teaching Fund
Adaptive cellular evolution or cellular system drift in hares
Get PDFAdaptations occur at many levels, for example, from DNA sequence of regulatory elements and cellular homeostatic systems to organismal physiology and behaviour (Mayr, 1997). Established adaptations are maintained by purifying and stabilizing selection. Students of animal diversity tend to focus on higher order traits, anatomy, physiology, organismal function and interactions. The core cellular and metabolic systems of metazoans evolved early in their history and are assumed to be rather similar between groups. The housekeeping functions and core metabolic functions of cells are generally considered relatively static, especially among closely related species. The extent to which evolution shapes core cellular metabolism and physiology in animals is largely unexplored. Ecological opportunities or strong positive selection can alter basal metabolic rate, activity levels and life-history traits (e.g., life span, age of maturity, offspring number) and potentially lead to divergence in core cellular and metabolic trait systems (Norin & Metcalfe, 2019; Speakman, 2005). Furthermore, systems under stabilizing selection can also change. Developmental systems of related species may produce the same phenotype or structure, but experience drift that can alter connections and even lead to turnover of cogs in the system (True & Haag, 2001). Are the cellular functions of animals highly constrained, subject to cellular system drift or affected by positive selection? This was tackled by a new study by Kateryna Gaertner and colleagues in a From the Cover manuscript in this issue of Molecular Ecology (Gaertner et al., 2022), using fibroblasts from the closely related but ecologically distinct brown and mountain hares.The Icelandic Research Fund.Peer ReviewedPost-print (lokagerð höfundar
Numerical Investigation on the Acceleration Vibration Response of Linear Actuator
Get PDFThis work is licensed under the Creative Commons Attribution International
License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/This study is aimed to investigate the acceleration response of the non-commutated Direct Current (DC) linear actuator in a numerical approach. The linear actuator is often driven with the specified wave digital signal processing (DSP), which gets forced vibration. The acceleration response of the actuator matters because it is related to vibration intensity. As well, the experiments and technical datasheets report that after the resonance frequency, the acceleration decreased, and the vibration intensity also reduced. This work uses the vibration fundamental concepts and presents results via a numerical approach that significantly matches the available experiments.-The Center of Excellence (CoE) Research on AI and Simulation-Based Engineering at Exascale (RAISE), EU’s Horizon 2020 Research and Innovation Framework
Programme under the grant agreement No. 951733
-The EuroCC projects, EU’s Horizon 2020 Research and Innovation Framework
Programme under the grant agreement No. 951740Peer Reviewe
Long or short silicic magma residence time beneath Hekla volcano, Iceland?
Get PDFPre-print (óritrýnt handrit)Timescales of magma transfer and differentiation processes can be estimated when the magma differentiation mechanism is known. When conventional major and trace element analyses fail to distinguish between various processes of magma differentiation, isotope compositions can be useful. Lower Th isotope ratios in silicic relative to basaltic magmas at a given volcano could result from magma storage over a period of several tens of thousands of years, if the differentiation process was fractional crystallization alone, or from crustal anatexis on a much shorter timescale. Recently mapped bimodal tephra
layers from Mt. Hekla, Iceland, confirm lower (230Th/232Th) and higher Th/U in silicic versus mafic magmas. Higher Th/U
has been taken to indicate either apatite fractionation or partial crustal melting. In situ trace element analysis of apatite and the enveloping glass in basaltic andesite, dacite and rhyolite was undertaken to examine its capacity to fractionate trace elements and their ratios. Both Th and U are compatible in apatite with a partition coefficient ratio DU/DTh of 1. Hence, apatite crystallization and separation from the melt has a negligible effect on Th/U in Hekla magmas. Partial melting of hydrothermally altered crust remains the preferred mechanism for producing silicic melt beneath Hekla. Ten to twenty percent partial melting of metabasaltic crust with 0.4–1.2 wt% H2O produces dacite magma with 4–6% water. Absence of low δ18O values in Hekla magmas compared to silicic magmas of the rift zones suggests mild hydration of the hydrothermally altered crust. Silicic magma formation, storage, differentiation and eruption at Hekla occurred over a timescale of less than a few centuries. Decreasing production of rhyolite and dacite during the Holocene lifetime of Hekla suggests changes in the crustal magma source and readjustment of the magma system with time.Field work was fnanced by the bilateral “Jules Verne” programme between
France and Iceland and the “ClerVolc laboratoire d’excellence” programme of Agent Nationale de Recherche, France, and Rannis, the Icelandic Centre for Research, both of which funded the analytical work. This Laboratory of Excellence ClerVolc contribution #520