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Nature-based Tourism in Renewable Energy Landscapes: Attitudes of Tourism Stakeholders
No full textWith increasing renewable energy infrastructure (REI) developments and growing nature-based tourism (NBT), their encounters are becoming more likely. To facilitate sustainable
development of both, it is important to gain more knowledge on the complex
interrelationships between NBT and REI, which is the overarching aim of this thesis. The
thesis provides an overview of existing knowledge on interrelationships between REI and
tourism by conducting a review of relevant academic literature. It furthermore investigates
the NBT-REI nexus by using a case study approach with a focus on the Icelandic Central
Highlands, which contain vast wilderness areas and are important for both NBT and
renewable energy harnessing. The primary data for this thesis was collected by employing
questionnaire surveys, semi-structured interviews, open-ended diaries, and participant
observation. The results reveal low compatibility of present-day NBT and REI, especially
in areas perceived by tourism stakeholders as wilderness. Tourists view proposed REI as
highly unsuitable in wilderness areas due to its negative impacts on wilderness experience.
Correspondingly, tourism service providers prefer to limit REI developments in natural
areas of the Central Highlands. According to tourism service providers, proposed wind
farms are more suitable in areas with few tourists, limited attractions, low degree of
naturalness, limited visibility of wind turbines, and urgent local need for energy. Notably,
tourism service providers tend to perceive the impacts of proposed REI on NBT as more
negative compared to existing REI. The perceived spatial extent of these impacts varies
among tourism service providers. It depends on the reasoning used while estimating the
impact areas, which falls into three categories: visibility of REI, tourist mobility, and
changes in travel patterns and tourism demand due to REI. These findings suggest that
tourism destinations should be viewed as elements of larger tourism networks, which are
likely to be impacted by REI. Tourism service providers view the Central Highlands and
its wilderness as a valuable resource that should be protected from further REI
developments. However, issues such as ensuring access to the area might lead to conflicts
between NBT and nature conservation and hinder preservation of wilderness. The findings
of this doctoral thesis demonstrate that the context surrounding each REI project, namely
various factors related to its location, REI itself and the perceptions and preferences of
tourism stakeholders play a crucial role in shaping potential impacts of REI on NBT.
Therefore, they should be taken into consideration when planning REI developments in
natural areas.Samfara aukinni uppbyggingu mannvirkja til framleiðslu endurnýjanlegrar orku og
vaxandi náttúruferðamennsku aukast líkur á árekstrum á milli þessara greina. Til að stuðla
að sjálfbærri þróun beggja greinanna er mikilvægt að afla aukinnar þekkingar á flóknu
samhengi á milli greinanna og er það meginmarkmið þessarar ritgerðar. Í ritgerðinni er
með ítarlegri heimildarýni gefið yfirlit yfir það sem er nú þegar vitað um tengsl
orkumannvirkja og ferðaþjónustu. Enn fremur var gerð tilviksrannsókn á miðhálendi
Íslands sem ætlað er auka enn frekar við þekkingu á tengslum náttúruferðamennsku og
orkumannvirkja þar sem miðhálendið er bæði mikilvægt fyrir náttúruferðamennsku og fyrir
framleiðslu á endurnýjanlegri orku. Rannsóknin byggist á gögnum sem safnað var með
spurningalistakönn-unum, hálfstýrðum viðtölum, dagbókum og þátttökuathugun
rannsakanda. Niðurstöðurnar sýna að sú náttúruferðamennska sem stunduð er á svæðinu nú á tímum fer ekki vel saman við virkjunarmannvirki, sér í lagi á svæðum sem
hagsmunaaðilar í ferðaþjónustu líta á sem víðerni. Ferðamenn telja fyrirhuguð
orkumannvirki ekki henta á óbyggðum svæðum vegna neikvæðra áhrifa mannvirkjanna á
það hvernig þeir upplifa víðerni. Í samræmi við viðhorf ferðamannanna vilja
ferðaþjónustuaðilar takmarka uppbyggingu orkumannvirkja á náttúrusvæðum, sér í lagi á
miðhálendinu. Að mati ferðaþjónustuaðila eru fyrirhuguð vindorkuver talin viðunandi á
svæðum sem hafa takmarkað aðdráttarafl fyrir ferðamenn og fáir ferðamenn fara um. Að
mati þeirra eiga vindorkuver einnig betur við á byggðum svæðum en náttúrulegum, auk
þess sem ákjósanlegra þykir að þau sjáist ekki víða að. Ferðaþjónustuaðilar voru þó
umburðarlyndari gagnvart vindorkuverum ef brýn staðbundin þörf var talin á aukinni
orkuframleiðslu. Almennt telja ferðaþjónustuaðilar að fyrirhuguð orkuver komi til með að
hafa neikvæðari áhrif en þau orkuver sem fyrir eru hafa haft. Munur er á mati
ferðaþjónustuaðila á umfangi þessara áhrifa og fara röksemdirnar sem notaðar eru við það mat einkum eftir þrennu: sýnileika orkumannvirkjanna, hreyfanleika ferðamanna og þeim breytingum sem verða á ferðamynstri og eftirspurn ferðamanna vegna orkumannvirkja. Niðurstöðurnar benda til þess að það verði að horfa á ferðamannastaði sem einstaka þætti í heildarkerfi ferðaþjónustunnar sem líklegt er að verði fyrir áhrifum af orkumannvirkjum. Ferðaþjónustuaðilar líta á miðhálendið og víðerni sem þar eru sem dýrmæta auðlind fyrir ferðaþjónustuna sem ætti að vernda fyrir frekari uppbyggingu orkumannvirkja. Hins vegar gætu atriði eins og bætt aðgengi inn á svæðið leitt til árekstra milli náttúruferðamennsku og náttúruverndar og staðið í vegi fyrir verndun víðerna. Niðurstöður þessarar doktorsritgerðar draga fram mikilvægi þess að skoða heildstætt áhrif hverrar virkjunar fyrir sig ásamt því að greina hvaða áhrif hagsmunaaðilar í ferðaþjónustu telja orkumannvirki geta mögulega haft á náttúruferðamennskuEimskip University Fund, Icelandic Research Fund (grant number: 229084-051), the Icelandic Ministry for the Environment and Natural Resources, the Steering committee for the Icelandic Master Plan for Nature Protection and Energy Utilization
Stability and dynamics of chiral magnetic structures in ferro- and antiferromagnets
Get PDFReduction of the size of magnetic bits for data storage, transfer and processing of
information down to the nanoscale would lay the foundation for large advances in
information technology, both in terms of processing speed and energy efficiency. Such
a development requires analysis of the stability of localized magnetic states with respect
to thermal fluctuations and random external influences. In the dissertation, these issues
are investigated in the framework of harmonic transition state theory. The lifetime of
skyrmions and antiskyrmions, two examples of chiral magnetic structures, is calculated
using various values of materials parameters, such as the ratio of the lattice constant
to the skyrmion size. The energy barrier for skyrmion collapse is found to approach
the Belavin-Polyakov lower bound of the energy of a topological soliton in the σ -
model, and the entropy contribution to the pre-exponential factor in the Arrhenius rate
expression for the lifetime is found to approach a constant. As a result, the skyrmion
lifetime can, for large enough number of spins, correspond to thermal stability at
room temperature even without magnetic dipole–dipole interaction. Calculations of
skyrmions in antiferromagnets are also presented, and their properties compared with
skyrmions in corresponding ferromagnets. The rates of skyrmion collapse and escape
through the boundary of a track, as well as the binding to and collapse at a non-magnetic
impurity, are calculated as a function of an applied magnetic field. The lifetime of
antiskyrmions in an Mn–Pt–Sn tetragonal Heusler material has been calculated using an
atomic scale representation including nearly a million spins. The long lifetime observed
experimentally at room temperature is found to result from energetic effects rather than
entropic effects in this system. The properties of antiskyrmions in ferromagnetic and
antiferromagnetic thin films are analyzed using an energy conserving transformation of
skyrmion spin configuration and vectors in the extended Heisenberg Hamiltonian. The
dynamics as well as thermal stability of antiskyrmions and corresponding skyrmions
can easily be compared using the transformation.Smækkun seguleininga fyrir gagnageymslu leggur grunninn að miklum framförum í
upplýsingatækni, bæði hvað varðar hraða og orkunotkun. Slík þróun krefst greiningar á
stöðugleika staðbundinna segulástanda með tilliti til varmaorku og tilviljunarkenndra
utanaðkomandi áhrifa. Í ritgerðinni eru þessi atriði rannsökuð með því að nota virkjun-
arástandskenninguna innan kjörsveifilsnálgunarinnar. Líftími skyrmeinda er reiknaður
út fyrir ýmis gildi á hlutfallinu milli grindarfastans og stærðar skyrmeindarinnar. Orku-
þröskuldurinn fyrir eyðingu skyrmeindar nálgast Belavin-Polyakov neðri mörk á orku
stakeindar í σ -líkaninu og óreiðuframlagið til forveldisstuðulsins í Arrhenius líkingunni
stefnir á fasta. Þar af leiðandi Líftími skyrmeindar getur skrymeind verið nægjanlega
stöðug við stofuhita ef hún samanstendur af nægjanlega stórum fjölda spuna, jafnvel þótt
tvískauts-tvískauts víxlverkun sé ekki tekin með í reikninginn. Gerðir eru útreikningar
á skyrmeindum í andseglandi efnum og eiginleikar þeirra bornir saman við skyrmeindir
í samseglandi efnum. Hraðafastinn fyrir eyðingu skyrmeindar inni í efninu, sem og
brotthvarf skyrmeindar í gegnum jaðra segulefnisins og binding við óseglandi óhrein-
indi, er reiknaður sem fall af álögðu segulsviði. Líftími andskyrmeinda við stofuhita í
Mn–Pt–Sn Heusler efni hefur verið reiknaður út með því að nota atómskala líkan sem
inniheldur næstum milljón spuna. Niðurstöður reikninganna sýna að sá langi líftími
sem hefur verið ákvarðaður með mælingum á tilraunastofu stafar af hárri virkjunarorku
frekar en entrópíuáhrifum í þessu kerfi. Eiginleikar andskyrmeinda í samseglandi og
andseglandi þunnum húðum eru greindir með vörpun á spunavigrum og útvíkkuðum
Heisenberg Hamilton virkja. Auðvelt er að bera saman færslueiginleika sem og varma-
fræðilegan stöðugleika andskyrmeinda og samsvarandi skyrmeinda með þessari vörpun
Þjóðarspegillinn XXII: Ágripabók og dagskrá: Ráðstefna í félagsvísindum 27. -28. október 2022
No full textMunnheilsa aldraðra einstaklinga. Lífsgæði íbúa og munnheilsuvernd á íslenskum hjúkrunarheimilum
No full textBackground: Good oral health is fundamental for general health, wellbeing and quality of life for all age groups. Little information exists on the oral health of older adults living in Icelandic nursing homes and how they perceive their oral health and quality of life (Paper I, II). Further, regular oral hygiene is important for oral health promotion and preventing the development of oral diseases, especially for frail older adults living in long-term care. The literature contains little information on oral care in nursing homes and regarding oral health attitudes and beliefs among nursing home staff.
Aim: First, this work aimed to screen oral health among residents in Icelandic nursing homes and explore the association between the number of decayed, missing and filled teeth (DMFT), dental prostheses, oral health problems, nutrition problems and quality of life (Papers I, II). Second, it aimed to study oral health beliefs and attitudes to oral care among staff working in these same nursing homes and compare the results between professions, along with the association between positive and negative oral health beliefs and oral care (Paper III).
Methods: Papers I and II report a cross-sectional study of 82 residents living in two nursing homes. Their oral health was screened according to international standards using the Oral Health Survey (OHS) and Oral Health Impact Profile (OHIP-49) to collect data on residents’ self-perceived oral health problems and their association with functional, physical, and social limitations and quality of life (Paper I). The self-perceived oral health problems and the association between oral health and nutrition problems were also studied using specific questions from the OHIP-49 (Paper II). Paper III was a cross-sectional study among nursing staff (N = 200) working in two nursing homes in Reykjavík and nearby municipalities. Data were collected using the Nursing Dental Coping Belief Scale (DCBS) to study their beliefs about being able to control oral health outcomes with oral care.
Results: In Papers I and II, a total of 73 residents (89%) completed the study. Their mean age was 86.8 years (± 5.7), ranging from 73 to 100 years. Edentate residents believed that their oral health negatively impacted their general wellbeing and quality of life compared with dentate residents. Both the number of DMFT (67.5%) and the mean DMFT index (25.7 3.3) were high, indicating a high prevalence of oral diseases in this sample. The prevalence of untreated oral symptoms was high (67%), and these were significantly more common among residents who had dwelled longer in the nursing home (Paper I). Most (59%) residents had some teeth, whereas others were edentulous. Residents who had dwelled longer than a year in the nursing home significantly more often had less taste sensitivity (p = 0.015), changed taste perception (p = 0.029) and chewing difficulties (p = 0.041) compared to residents who had stayed in the nursing home for less time. Edentate residents frequently had nutrition-related problems (M = 4.8 ± 2.5, range 0 to 8) and poor oral health, which can be an important predictor of malnutrition (Paper II).
In Paper III, a total of 109 employees (54.5%) participated in the study, with a mean age of 38.5 years (± 15.8), ranging from 18 to 70 years. Staff with oral health education scored lower on the DCBS than their peers with no oral health education, which indicates that oral health education resulted in positive oral health beliefs. Nevertheless, most nursing home staff in this study had limited or no oral health education or practical training in oral care. The results show that oral health education may promote positive oral health beliefs and aid staff to believe that their oral care can reduce oral health problems among residents.
Conclusion: Oral care standards should be revised in nursing homes to guarantee oral care according to individualised needs. Staff must have specific oral health education and training. They need access to appropriate oral health assessment tools for regular screening to prevent the development of oral diseases and modify oral care plans when needed. To cope with oral care in nursing homes, authorities, politicians, health professionals, nursing staff and associates working in geriatric care could work together to create an oral care policy to lower the burden of oral diseases among residents.Bakgrunnur: Góð munnheilsa er mikilvæg fyrir alla aldurshópa og stuðlar að góðri almennri heilsu, vellíðan og lífsgæðum. Litlar upplýsingar eru fyrirliggjandi um munnheilsu íbúa á hjúkrunarheimilum og hvernig þeir upplifa eigin tannheilsu og tengd lífsgæði (Vísindagrein I og II). Eins er mikilvægt að viðhalda munnheilsu með reglulegri munnhirðu til að koma í veg fyrir þróun munnsjúkdóma, ekki síst hjá þeim sem eru orðnir hrumir og búa á stofnunum. Ekki eru fyrirliggjandi upplýsingar um hvernig staðið er að munnheilsuvernd á íslenskum hjúkrunarheimilum eða hver viðhorf eru meðal starfsfólk til munnheilbrigðisþjónustu í starfi sínu.
Markmið: Í fyrsta lagi, að skima munnheilsu íbúa á hjúkrunarheimilum og kanna sérstaklega hvernig fjöldi skemmdra, fylltra og tapaðra tanna og tegund tanngerva hefðu áhrif á munnheilsutengd lífsgæði og skoða tengsl milli munnheilsu og næringartengdra vandamála (Vísindagrein I og II). Í öðru lagi, að rannsaka viðhorf starfsfólks á þessum heimilum til munnheilsuverndar og bera niðurstöður saman milli fagstétta. Sérstaklega var skoðað hvort jákvætt og neikvætt viðhorf starfsfólks hefði mögulega tengsl við fagleg störf þeirra við munnheilsuvernd.
Aðferðir: Vísindagreinar I og II lýsa þversniðsrannsókn meðal íbúa (N = 82) á tveimur hjúkrunarheimilum á höfuðborgarsvæðinu, þar var munnheilsa þátttakenda skoðuð og skráð samkvæmt alþjóðlegum skoðunarstaðli (Oral Health Survey, OHS) og lagður fyrir lífsgæðakvarði (Oral Health Impact Profile, OHIP-49), sem mælir neikvæð áhrif munnkvilla á félagslega–, sálræna– og líkamlega virkni einstaklingsins og lífsgæði (Vísindagrein I). Jafnframt voru skoðuð tengsl milli munnheilsu íbúa, lífsgæða og næringartengdra vandamála með átta sértækum spurningum úr OHIP-49 lífsgæðakvarðanum (Vísindagrein II). Vísindagrein III lýsti þversniðsrannsókn meðal starfsfólks (N = 200) á tveimur hjúkrunarheimilum á höfuðborgarsvæðinu. Lagður var fyrir þýddur og staðfærður spurningarlisti Viðhorf til munnheilsuverndar (e. Nursing Dental Coping Belief Scale, DCBS) sem metur trú starfsfólks á því að þeir geti og búi yfir hæfni til að geta haft áhrif á framgöngu munnkvilla hjá sjúklingum í þeirra umsjá.
Niðurstöður: Vísindagreinar I og II sýna niðurstöður úr þversniðsrannsókn meðal íbúa á tveimur hjúkrunarheimilum. Alls luku 73 íbúar eða rúmlega 89% þátttöku í rannsókninni, meðalaldur var 86,8 ár (± 5,7) og aldurs spönn 73-100 ár. Tannlausir íbúar upplifðu neikvæðari áhrif eigin munnheilsu á almenna líðan og lífsgæði í samanburði við tennta íbúa. Fjöldi skemmdra, tapaðra og fylltra tanna var mikill (67,5%) og meðal tannátustuðull hár (M = 25,7 3,3), sem bendir til þess að útbreiðsla munnkvilla sé algeng í þessum hóp. Enn fremur var hlutfall ómeðhöndlaðra munnkvilla hátt hjá þátttakendum (67%) og reyndust íbúar með lengri búsetu á hjúkrunarheimili vera martækt oftar útsettir fyrir að vera með ómeðhöndlaða munnkvilla (Vísindagrein I). Meirihluti íbúa (59%) hafði einhverjar tennur en aðrir voru tannlausir, þeir íbúar sem höfðu búið lengur en ár á hjúkrunarheimili upplifðu martækt oftar skert bragðskyn (p = 0,015), breytt bragðskyn (p = 0,029) og erfiðleika við að tyggja mat (p = 0,041) en þeir sem búið höfðu þar skemur. Tannlausir íbúar skoruðu hátt að meðaltali á kvarða sem mælir næringartengd vandamál (M = 4,8 ± 2,5, min 0 – 8 max) og íbúar sem voru metnir með slæma munnheilsu DMFT-28), sem getur verið mikilvægur fyrirboði um aukna hættu á vannæringu (Vísindagrein II). Vísindagrein III, þátttaka í rannsókninni var 54,5% (109/200), meðalaldur var 38,5 ár (15,8) og aldurs spönn 18-70 ár. Starfsfólk með menntun í munnheilsuvernd skoraði marktækt lægra á spurningarlistanum Viðhorf til munnheilsuverndar en starfsfólk án hennar, sem bendir til þess að þeir sem hafi hlotið menntun í munnheilsuvernd séu með jákvæðara viðhorf til munnheilbrigðisþjónustu í starfi sínu. Algengast var að ófaglærðir starfsmenn sinntu daglegri munnhirðu íbúa en þeir voru ólíklegastir til að hafa menntun á því sviði. Samkvæmt niðurstöðum rannsóknarinnar stuðlar þekking á munnheilsuvernd að aukinni trú starfsfólks á að það hafi getu til að draga úr þróun munnkvilla meðal íbúa.
Ályktun: Álykta má að endurskoða þurfi munnheilsuvernd á hjúkrunarheimilum, til að tryggja að hún sé í samræmi við einstaklingsbundnar þarfir íbúa. Nauðsynlegt er að starfsfólk hafi sértæka menntun í munnheilsuvernd aldraðra og búi yfir skimunartæki í forvarnarskyni til að meta reglulega munnheilsu íbúa og framgang munnkvilla. Með samstilltri þverfræðilegri samvinnu heilbrigðisstétta og aðstoðarfólks í öldrunarhjúkrun með aðkomu hagsmunaaðila og stjórnvalda mætti endurskoða munnheilbrigðisþjónustu á þessum vettvangi og leita lausna til að draga úr sjúkdómsbyrði munnkvilla meðal íbúa
The order in disorder: Magnetism in amorphous cobalt-based thin films and heterostructures
Get PDFThe work in this thesis is focused on understanding the emergent properties of amorphous magnetic materials. Amorphous materials lack long-range structural ordering, characteristic of crystalline materials. Instead, these materials exhibit medium-to-short range order. In elemental form, metals
always form crystals but can be amorphized by alloying with other metals of different atomic radii.
To study the magnetic properties of amorphous magnetic metals, we use CoAlZr and TbCo of various compositions, both in single layers and nanolaminates. The samples were fabricated using direct current magnetron sputtering in an ultra-high vacuum system. Structural characterization was done using x-ray reflectivity and grazing incidence x-ray diffraction. The magnetic properties were measured using magneto-optic Kerr effect, vibrating sample magnetometry, and polarized neutron reflectometry.
First, we show how the magnetic properties of the ferromagnetic Co are affected by diluting it with non-magnetic AlZr. We find that the critical temperature and magnetization of CoAlZr depends on composition, and decreases linearly with increasing AlZr content. Due to the disordered structure, there is a local distribution in Co concentration with regions of high and low Co density. We find a surprising manifestation of this chemical modulation, which emerges as competing anisotropies. By analyzing the anisotropy as a function of composition, we can define quantitatively a cobalt composition distribution on the nanoscale (Paper III). Similar to the CoAlZr, we also observe competing anisotropy in the TbCo alloy. We find, by analyzing the effective anisotropy as a function of composition and thickness, that there are two competing anisotropy terms in the TbCo layer: interface and bulk anisotropy. The interface favors in-plane magnetization while the bulk favors perpendicular magnetization (Paper IV).
In the second part of this study, we focus on hybrid structures composed of multilayers of alternating high- and low- CoAlZr and bilayers of TbCo and CoAlZr. In the CoAlZr multilayers, we find that within the low- layer there is a non-zero magnetization at three times its intrinsic ordering temperature which extends through at least 10~nm. This is due to the proximity to the ferromagnetic (high ) layer (Paper I). In the TbCo/CoAlZr bilayers, we investigate the exchange coupling between two layers with crossed magnetic anisotropies. We find that a 7.5~nm interface layer of the CoAlZr is strongly exchange coupled to the TbCo with a magnetization perpendicular to the plane and switches in unison with the TbCo layer (Paper II). To resolve the depth dependence of the magnetization, these hybrid structures are then investigated further using polarized neutron reflectivity (Paper V)
Rannsókn á neðanjarðar örversamfélögum í basalti á eldfjallaeyjunni Surtsey við Ísland
No full textSurtsey is a volcanic island located on the south-east offshore extension of the Icelandic
rift zone. It was formed during successive eruptions from the seafloor in 1963-1967 and
has been officially protected and studied ever since. It represents an exceptional natural
setting for studying colonization and succession of life on land. Also for subsurface
microbial communities associated with newly formed basaltic tuff deposits in a seawater hydrothermal system that is still active and at temperatures approaching the presumed
thermal limit for functional life. During an international drilling operation at Surtsey in
2017, drill core samples at successive depths as well as associated hot fluids and surface
fumes from fumaroles were collected for microbial investigations. This thesis presents the
first and most comprehensive research of the Surtsey subsurface biosphere. Multiple
approaches were combined on the rare and unique samples to increase the knowledge of
microbial communities inhabiting the oceanic subsurface and of the processes that sustain
such life. These included molecular analyses of environmental DNA through 16S rRNA
gene amplicon and metagenome sequencing, isolation and characterization of bacterial
strains and microscopic investigations. Based on the DNA concentration, the microbial cell
numbers present in the drill cores were estimated to range from about 5×104 to 1×106
cells
per gram of sample. The Surtsey subsurface is therefore a low biomass environment,
making the samples extremely sensitive to external contamination. It is nevertheless a
diverse habitat that hosts bacterial and archaeal clades, including extremophiles, that have
been previously detected in other terrestrial and marine environments. Yet, many clades
belonged to unknown lineages. Predictive functional analyses based on taxonomic
identifications revealed that the Surtsey subsurface biosphere is composed of heterotrophic
microorganisms as well as chemoautotrophs involved in the sulfur, nitrogen, and methane
cycles. However, these results could not be strengthened by the functional metagenomic
investigations as they were inconclusive. Numerous enrichment cultures were initiated
using different conditions and media and resulted in nearly 200 isolated bacterial strains,
which included several novel species. One novel thermophilic bacterial species,
Rhodothermus bifroesti, was fully characterized and its genome was sequenced and
compared with those of the two other described Rhodothermus species. Comparative
analyses revealed that 2.15% of the amplicon sequence variants from the 16S rRNA gene
amplicon sequence datasets were represented by cultivated strains using standard methods.
Finally, putative microbial structures adhering to the basaltic tuff were discovered inside
the numerous interconnected vesicles found in the basaltic glass. All of the findings point
to an active microbial colonization of the Surtsey deposits within 50 years after the
eruptions ended, with possible sources of colonization coming from the surrounding
ecosystems via microbial dissemination and possible adaptations. The thesis establishes a
foundation for future research on the microbial communities that inhabit the Surtsey
subsurface and their temporal succession in the face of a cooling and changing
hydrothermal environment
A type system with subtyping for WebAssembly’s stack polymorphism
Get PDFPost-print (lokagerð höfundar)We propose a new type system for WebAssembly. It is a refinement of the type system from the language specification and is based on type qualifiers and subtyping. In the WebAssembly specification, a typable instruction sequence gets many different types, depending in particular on whether it contains instructions such as br (unconditional branch) that are stack-polymorphic in an unusual way. But one cannot single out a canonical type for a typable instruction sequence satisfactorily. We introduce qualifiers on code types to distinguish between the two flavors of stack polymorphism that occur in WebAssembly and a subtyping relation on such qualified types. Our type system gives every typable instruction sequence a canonical type that is principal. We show that the new type system is in a precise relationship to the type system given in the WebAssembly specification. In addition, we describe a typed functional-style big-step semantics based on this new type system underpinned by an indexed graded monad and prove that it prevents stack-manipulation related runtime errors. We have formalized our type system, inference algorithm, and semantics in Agda.This work was supported by the Icelandic Research Fund grant no. 196323-053.Peer reviewed (ritrýnd grein
Atomistic spin simulations of electric-field-assisted nucleation and annihilation of magnetic skyrmions in Pd/Fe/Ir(111)
Get PDFWe provide a theoretical background for electric-field-assisted thermally activated writing and deleting of magnetic skyrmions in ultrathin transition-metal films. We apply an atomistic spin model, which includes the exchange interaction, the Dzyaloshinskii-Moriya interaction, and the magnetocrystalline anisotropy energy. The strengths of the magnetic interactions are taken from density functional theory (DFT) calculations for a Pd/Fe bilayer on the Ir(111) surface. We systematically vary all magnetic interactions up to ~\% reating the magnetoelectric effect in linear response. The critical magnetic fields marking the onset of the skyrmion phase and the field-polarized phase shift considerably upon varying the interaction constants due to the electric field. Based on harmonic transition state theory, we calculate the transition rates for skyrmion nucleation and annihilation, which are in good agreement with experimental values for Pd/Fe/Ir(111). The field-dependent variation of energy barriers and preexponential factors leads to large changes of the transition rates, which are accompanied by changes in skyrmion radii. Finally, we simulate the electric-field-dependent writing and deleting of magnetic skyrmions in Pd/Fe/Ir(111) based on the master equation and transition rates obtained using the magnetic interactions calculated via DFT for electric fields of ~V/{\AA}. The magnetic-field-dependent skyrmion probability follows a Fermi-Dirac distribution function of the free energy difference of the skyrmion state and the ferromagnetic (FM) state. The probability function for the opposite electric field directions is in striking agreement with experimental results [Romming {\it et al.}, Science {\bf 341}, 636 (2013)].Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via Project No. 414321830 (HE3292/11-1), the Icelandic Research Fund (Grants No. 217750 and No. 184949), the University of Iceland Research Fund (Grant No. 15673), the Russian Science Foundation (Grant No. 19-72-10138), and the Swedish Research Council (Grant No. 2020-05110).Peer Reviewe
Thermal generation of droplet soliton in chiral magnet
Get PDFControlled creation of localized magnetic textures beyond conventional π-skyrmions is an important problem in the field of magnetism. Here, by means of spin dynamics simulations, Monte Carlo simulations, and harmonic transition state theory we demonstrate that an elementary chiral magnetic soliton with zero topological charge—the chiral droplet—can be created by thermal fluctuations in the presence of the tilted magnetic field. The proposed protocol relies on an unusual kinetics combining the effects of the entropic stabilization and low-energy barrier for the nucleation of a topologically trivial state. Following this protocol by varying temperature and the tilt of the external magnetic field, one can selectively generate chiral droplets or π-skyrmions in a single system. The coexistence of two distinct magnetic solitons establishes a basis for a rich magnetization dynamics and opens up the possibility for the construction of more complex magnetic textures such as skyrmion bags and skyrmions with chiral kinks.Deutsche Forschungsgemeinschaft (DFG) through SPP 2137 "Skyrmionics" Grant No. KI 2078/1-1, the Russian Science Foundation (Grant No. 19-72-10138), the Icelandic Research Fund (Grant Nos. 184949 and 217750), the University of Iceland Research Fund
(Grant No. 15673), and the Swedish Research Council (Grant No. 2020-05110)Peer Reviewe
Tengsl svefns og hugrænna þátta meðal íslenskra ungmenna
No full textAbstract
Background: Insufficient sleep is associated with an increased risk of a variety
of negative health outcomes and has been shown to adversely affect academic
and cognitive function. Despite strong evidence of the deleterious effects of
short and disrupted sleep on health, studies that use objective methods to
measure adolescent free-living sleep, in general, and its association with
academic and cognitive performance, specifically, are scarce, particularly
during the critical transition from compulsory to secondary education.
Aim: The aim of this research was to use objective measures to
quantify the free-living sleep of Icelandic adolescents at ages 15 and 17, as
they transition from compulsory to secondary education, and to determine
whether their sleep patterns are associated with academic and cognitive
outcomes.
Methods: The study sample came from six elementary schools in Reykjavík,
Iceland. One week of free-living sleep measured with wrist actigraphy was
collected at two time points. The first wave of data collection occurred in 2015,
where 280 participants had valid sleep data (mean age 15.9±0.3 years). Two
years later, 199 participants had valid sleep data (mean age of 17.7±0.3 years).
In total, 145 participants had complete data at both data collection points.
During the first wave of data collection, academic achievement was objectively
quantified using the combined score from standardized national examinations
administered to all 10th grade students in mathematics, English, and Icelandic.
During the second wave of data collection, an n-back working memory task and
Posner cue-target visual attention task were used to objectively assess
cognitive function.
Results: Over all measured nights at both time points, Icelandic adolescents
averaged late bedtimes (00:43 at age 15, 01:12 at age 17), short total sleep
time (6.6 ± 0.7 h/night at age 15 and 6.2 ± 0.7 h/night at age 17) and high
variability in total sleep time (weekly standard deviations of 1.3 h and 1.4 h at
ages 15 and 17, respectively). Thus, during the two year change from age 15 to
age 17, students sleep duration decreased, night-to-night variability in sleep duration increased, and students went to bed 29 min/night later. Cross-sectional regression of the data collected at age 15 in those with standardized exam scores (n=253) demonstrated that both bedtime and night-to-night variability in total sleep time were negatively associated with the average score across all topics. Similarly, cross-sectional analysis of students who underwent cognitive function testing at age 17 (n=160) showed that time in bed the night before cognitive testing was negatively associated with response times during the most challenging memory task. However, sleep measures the night before
did not correlate with performance on the attention task and weekly sleep parameters were not associated with either cognitive task.
Conclusion: In general, Icelandic students go to bed late and have short and
inconsistent sleep schedules at both age 15 and age 17. Cross-sectional results
at age 15 indicate that those with earlier bedtimes and more consistent sleep
schedules score higher on national exams. In addition, the cross-sectional
results at age 17 demonstrated that shorter time in bed the night prior to the
cognitive testing was associated with poorer performance on the most
challenging short-term memory task. Despite the presence of several
significant associations, the relationship between free-living sleep and
academic and cognitive task performance in healthy adolescents is less clear
than that identified in laboratory studies or with self-report, perhaps due to
high night-to-night sleep variation. Future studies with longer observation
periods and interventional components could further clarify the relationship
between free-living sleep and academic and cognitive performance in
adolescents.Bakgrunnur: Fyrri rannsóknir hafa sýnt fram á að nægur svefn á unglingsárum
er lífsnauðsynlegur, og að stuttur og ófullnægjandi svefn getur haft áhrif á
andlega og líkamlega heilsu. Enn fremur hefur verið sýnt fram á að stuttur
svefn getur haft neikvæð áhrif á námsárangur og hugræna virkni. Þrátt fyrir
sterkar vísbendingar um skaðleg áhrif ófullnægjandi svefns á heilsuna skortir
rannsóknir sem mæla svefn hlutlægt (við frjálsar aðstæður). Einnig
skortir rannsóknir sem nota hlutlægar mælingar til að kanna tengsl svefns á
námsárangur og hugræna frammistöðu, sérstaklega á þessum mikilvæga tíma
þegar ungmenni færa sig úr grunnskóla og yfir í framhaldsskóla.
Markmið: Meginmarkmið þessarar doktorsritgerðar var að nota
hlutlæga mælikvarða til að mæla svefn íslenskra ungmenna á aldrinum 15 til 17
ára, við skólaskiptin úr grunnskóla yfir í framhaldsskóla, og að skoða
hvort svefnmynstur þeirra tengist námsárangri og hugrænum þáttum.
Aðferðir: Rannsóknarúrtakið kom frá sex grunnskólum í Reykjavík. Gögnum var
safnað vorið 2015, þar sem 280 þátttakendur höfðu gild gögn um svefn
(meðalaldur 15,9 ± 0,3 ár). Tveimur árum síðar höfðu 199 þátttakendur gild
svefngögn (meðalaldur 17,7 ± 0,3 ár). Hægt var að tengja gögn hjá 145
nemendum á báðum tímapunktum. Svefn var mældur í eina viku með
actigraph hreyfimæli sem var staðsettur á úlnliði. Í fyrri gagnasöfnun árið 2015
var meðaleinkunn í samræmdum prófum í íslensku, stærðfræði og ensku notuð
sem mælikvarði á námsárangur. Tveimur árum seinna var hugræn virkni mæld
með n-back minnisprófi og Posner cue-target athyglisprófi. Við mat á gögnum
var notast við ýmsar tölfræðilegar greiningar, keyrðar í R tölfræðiforritinu.
Niðurstöður: Íslensk ungmenni fara að meðaltali seint í rúmið (00:43 við 15 ára
aldur, 01:12 við 17 aldur) og heildar svefntími er stuttur (6,6 ± 0,7 klst /nótt 15
ára og 6,2 ± 0,7 klst./nótt 17 ára). Enn fremur er breytileiki í svefni hár á báðum
tímapunktum (1,3 klst./nótt og 1,4 klst). Þegar heildarbreyting á svefni frá 15 til
17 ára aldurs er skoðuð, sést að svefnlengd nemanda minnkar, svefnbreytileiki
á nóttu eykst og nemendur fara að meðtali að sofa 29 mínútum seinna. Við
fyrri gagnasöfnun, árið 2015 (n=253) fundust neikvæð tengsl á milli
svefnlengdar, háttatíma og einkunna á samræmdu prófi sem gefur til kynna að
nemendur sem fara fyrr að sofa og eru með minni breytileika í svefni fá hærri
meðaleinkunn á prófunum. Svipað fannst í seinni gagnasöfnun árið 2017
(n=160), en þar sást að styttri tími í rúminu nóttina fyrir hugræna prófið tengdist slakari árangri, en þó aðeins á mest krefjandi minnisprófinu. Hins vegar voru ekki tengsl á milli svefns kvöldið áður og frammistöðu á athyglisprófinu og engin tengsl fundust á milli heildarsvefns yfir vikuna og niðurstöðum á minnis- og athyglisprófinu.
Samantekt: Almennt fara íslensk ungmenni seint að sofa og svefnbreytileiki er
hár bæði við 15 og 17 ára aldur. Að sama skapi styttist svefnlengd á tveggja ára
tímabili þegar nemendur útskrifast úr 10. bekk og skipta yfir í framhaldsskóla.
Þversniðsniðurstöður við 15 ára aldur sýna að svefngæði og háttatími hafa áhrif
á einkunnir, en þeir nemendur sem fara fyrr að sofa og eru með lítinn
breytileika í svefni fá hærri einkunnir í samræmdum prófum. Að auki sýndu
niðurstöður við 17 ára aldur að styttri tími í rúminu nóttina fyrir hugrænu
prófin tengdist slakari frammistöðu á mest krefjandi minnisverkefninu. Svefn
virðist því hafa áhrif á hugræna þætti hjá 17 ára unglingum. Þrátt fyrir að fyrri
rannsóknir hafi sýnt mikilvæg tengsl milli svefns og hugrænnar frammistöðu hjá
heilbrigðum unglingum, virðast tengslin sem mælast hlutlægt vera óljósari en
þau sem koma fram á rannsóknarstofu eða sem mæld eru með huglægum
mælitækjum eins og spurningalistum. Ein skýringin getur verið mikill breytileiki
í svefni hjá úrtakinu en framtíðarrannsóknir með lengri athugunartímabilum og
íhlutunum gætu skýrt sambandið milli svefns og náms- og hugræns árangurs
hjá unglingum enn frekar.Háskólasjóður Eimskipafélags Íslands, Rannsóknamiðstöð Íslands (RANNÍS