Opin vísindi
Opin vísindi er varðveislusafn vísindaefnis og doktorsritgerða í opnum aðgangi á vegum íslenskra háskóla og Landsbókasafns Íslands - Háskólabókasafns.
Opinn aðgangur að rannsóknaniðurstöðum er í samræmi við 10. gr. laga nr. 3/2003 um opinberan stuðning við vísindarannsóknir sem og kröfur innlendra og erlendra rannsóknasjóða. Markmiðið með opnum aðgangi er að niðurstöður rannsókna séu aðgengilegar sem flestum óhindrað og án endurgjalds á rafrænu formi. Vistun í varðveislusafninu er varanleg og ætlað að tryggja aðgang að vísindaefni íslenskra háskóla í opnum aðgangi um ókomna tíð. Varðveislusafnið Opin vísindi er tengt við rannsóknagáttina IRIS og rannsóknaniðurstöður í opnum aðgangi sem eru skráðar í IRIS eru um leið vistaðar og gerðar aðgengilegar til framtíðar í varðveislusafninu. Með því að safna þessu efni saman í eitt safn verður aðgangur að því einfaldur og þægilegur fyrir alla sem vilja kynna sér það og geta þannig notið þess öfluga vísindastarfs sem fram fer í háskólum landsins.
Varðveislusafnið er OpenAIRE / OpenAIREplus samhæft og samrýmist kröfum sem gerðar eru um birtingu rannsóknaniðurstaðna úr verkefnum sem styrkt eru úr evrópsku rannsóknaáætlununum FP7 og H2020.
Varðveislusafnið notar opna hugbúnaðinn DSpace.
Opinn aðgangur að rannsóknaniðurstöðum er í samræmi við 10. gr. laga nr. 3/2003 um opinberan stuðning við vísindarannsóknir sem og kröfur innlendra og erlendra rannsóknasjóða. Markmiðið með opnum aðgangi er að niðurstöður rannsókna séu aðgengilegar sem flestum óhindrað og án endurgjalds á rafrænu formi. Vistun í varðveislusafninu er varanleg og ætlað að tryggja aðgang að vísindaefni íslenskra háskóla í opnum aðgangi um ókomna tíð. Varðveislusafnið Opin vísindi er tengt við rannsóknagáttina IRIS og rannsóknaniðurstöður í opnum aðgangi sem eru skráðar í IRIS eru um leið vistaðar og gerðar aðgengilegar til framtíðar í varðveislusafninu. Með því að safna þessu efni saman í eitt safn verður aðgangur að því einfaldur og þægilegur fyrir alla sem vilja kynna sér það og geta þannig notið þess öfluga vísindastarfs sem fram fer í háskólum landsins.
Varðveislusafnið er OpenAIRE / OpenAIREplus samhæft og samrýmist kröfum sem gerðar eru um birtingu rannsóknaniðurstaðna úr verkefnum sem styrkt eru úr evrópsku rannsóknaáætlununum FP7 og H2020.
Varðveislusafnið notar opna hugbúnaðinn DSpace.
Nýlega bætt við
Definition of excessive daytime sleepiness in the general population : Feeling sleepy relates better to sleep-related symptoms and quality of life than the Epworth Sleepiness Scale score. Results from an epidemiological study
(2019-12-01) Thorarinsdottir, Elin H.; Bjornsdottir, Erla; Benediktsdottir, Bryndis; Janson, Christer; Gislason, Thorarinn; Aspelund, Thor; Kuna, Samuel T.; Pack, Allan I.; Arnardottir, Erna S.; Department of Engineering; Department of Computer Science
Many different subjective tools are being used to measure excessive daytime sleepiness (EDS) but the most widely used is the Epworth Sleepiness Scale (ESS). However, it is unclear if using the ESS is adequate on its own when assessing EDS. The aim of this study was to estimate the characteristics and prevalence of EDS using the ESS and the Basic Nordic Sleep Questionnaire (BNSQ) in general population samples. Participants aged 40 years and older answered questions about sleepiness, health, sleep-related symptoms and quality of life. Two groups were defined as suffering from EDS: those who scored >10 on the ESS (with increased risk of dozing off) and those reporting feeling sleepy during the day ≥3 times per week on the BNSQ. In total, 1,338 subjects (53% male, 74.1% response rate) participated, 13.1% reported an increased risk of dozing off, 23.2% reported feeling sleepy and 6.4% reported both. The prevalence of restless leg syndrome, nocturnal gastroesophageal reflux, difficulties initiating and maintaining sleep and nocturnal sweating was higher among subjects reporting feeling sleepy compared to non-sleepy subjects. Also, subjects reporting feeling sleepy had poorer quality of life and reported more often feeling unrested during the day than non-sleepy subjects. However, subjects reporting increased risk of dozing off (ESS > 10) without feeling sleepy had a similar symptom profile as the non-sleepy subjects. Therefore, reporting only risk of dozing off without feeling sleepy may not reflect problematic sleepiness and more instruments in addition to ESS are needed when evaluating daytime sleepiness.
Entropy-driven phase transition in a non-collinear antiferromagnet due to higher-order exchange interactions
(Springer Nature, 2026-01-09) Kollwitz, Leo; Goerzen, Moritz A.; Beyer, Bjarne; Schrautzer, Hendrik; Heinze, Stefan; Faculty of Physical Sciences (UI); Raunvísindadeild (HÍ); School of Engineering and Natural Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ)
The 3Q state arises due to the superposition of three symmetry equivalent spin spirals stabilized by higher-order exchange interactions. It has been predicted more than 20 years ago but was only recently discovered in a Mn monolayer on the Re(0001) surface. To date little is known about the thermodynamic properties of this intriguing non-coplanar spin state. Here, we reveal a lowtemperature phase transition between the 3Q and the row-wise antiferromagnetic state in this system via Monte Carlo simulations based on an atomistic spin model parametrized by density functional theory. By modeling the free energy landscape in terms of thermal excitations we derive an analytical expression of the partition function, which allows us to prove that the phase transition is driven by entropy. The predicted phase transition is not unique to Mn/Re(0001) but appears for a wide range of magnetic interaction parameters and is expected to occur also for other multi-Q states.
Eigenmode following for direct entropy calculation and characterisation of magnetic systems
(Springer Nature, 2026-07-13) von Malottki, S.; Goerzen, Moritz A.; Schrautzer, Hendrik; Bessarab, Pavel F.; Heinze, Stefan; Faculty of Physical Sciences (UI); Raunvísindadeild (HÍ); School of Engineering and Natural Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ)
The effect of entropy can be crucial for magnetic skyrmions, and in some cases, its accurate prediction has been prevented by the limitations of the harmonic approximation. We present an eigenmode following method (EMF) that has been developed for the numerical scanning of the potential energy surface and the direct calculation of entropy and pre-exponential factors of transition rates. While the concepts of following eigenmodes and numerical direct entropy calculation have been known individually, their combination yields a new and general way of effective sampling of the energy surface for high-accuracy treatment of non-harmonic eigenmodes. For this, the EMF method requires iterative updates of the eigenpairs of the softest eigenmodes that need the most accurate modelling. In contrast to other methods, EMF does not move “uphill" or “downhill" in energy to find stationary points, but to obtain energy curves. By numerical integration of the Boltzmann factor along these curves, the partition functions of the following eigenmodes can be calculated without making assumptions of their form. We introduce the general theoretical background and algorithm of the EMF method before providing test calculations and relevant use cases in the framework of atomistic spin simulations with a focus on magnetic skyrmion collapse.
Impact of higher-order exchange on the lifetime of skyrmions and antiskyrmions
(Springer Nature, 2026-03-23) Schrautzer, Hendrik; Goerzen, Moritz A.; Beyer, Bjarne; Haldar, Soumyajyoti; Bessarab, Pavel F.; Heinze, Stefan; Faculty of Physical Sciences (UI); Raunvísindadeild (HÍ); School of Engineering and Natural Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ)
Reliable control of skyrmion lifetime is essential for realizing spintronic devices, yet the role of higherorder exchange—which can lead to skyrmion stabilization—remains largely unexplored. Here we calculate lifetimes of isolated skyrmions and antiskyrmions at transition-metal interfaces based on an atomistic spin model that includes all fourth-order exchange terms. Within harmonic transition-state theory, we evaluate both energetic and entropic contributions and find substantially enhanced lifetimes when higher-order exchange is included. The four-spin four-site interaction raises the energy barrier and lowers the curvature of the energy landscape at the collapse saddle point, increasing the pre-exponential factor. We show that skyrmions and antiskyrmions can remain thermally stable even without Dzyaloshinskii-Moriya interaction (DMI), and that tuning the four-spin term by a small amount modulates the prefactor over orders of magnitude. Our results identify higher-order exchange as a promising route to stabilize topological magnetic textures—in particular in systems lacking DMI—and to engineer their thermally activated decay.
Chemical warfare in a degraded land: The allelopathic capacity and allelochemical diversity of Empetrum nigrum in Icelandic tundra ecosystems
(University of Iceland, School of Engineering and Natural Sciences, Faculty of Life and Environmental Sciences, 2026-11-11) Ryde, Ingvild; Prof. Emerita Ingibjörg Svala Jónsdóttir; Faculty of Life and Environmental Sciences (UI); Líf- og umhverfisvísindadeild (HÍ); School of Engineering and Natural Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ)
Iceland has major issues with land degradation due to centuries of unsustainable land use. Degraded Icelandic tundra ecosystems do not easily recover after removing one of the main drivers of degradation – livestock overgrazing – and they appear to be “trapped” in degraded states. It is important to identify the “trapping mechanisms” potentially interfering with restoration efforts to avoid further loss of plant and soil resources. One such mechanism may be “chemical warfare” through the release of allelochemicals by unpalatable plants that inhibit seed germination and seedling growth in neighbouring species and modify ecosystem processes. The aim of this thesis was to investigate the role of the unpalatable and allelopathic evergreen dwarf shrub Empetrum nigrum in keeping degraded Icelandic tundra ecosystems trapped in degraded states, by assessing the allelopathic capacity and allelochemical diversity of Icelandic Empetrum. This thesis comprises three research papers based on bioassays and chemical analyses following targeted and untargeted liquid chromatography-mass spectrometry metabolomics approaches.
The results show that volcanic soils alleviate the allelopathic capacity of Empetrum considerably when compared with non-volcanic soils, reducing negative soil legacy effects of Empetrum-associated soils. Nevertheless, the allelopathic capacity of Empetrum is likely high enough to retard seedling establishment in Icelandic tundra ecosystems, considering the high amount of Empetrum leaf biomass in the system. The synoecious Empetrum group hermaphroditum was found to have a stronger allelopathic capacity than the monoecious nigrum group, partly explained by higher foliar concentrations of the previously designated key allelochemical Batatasin-III. Furthermore, male nigrum plants were found to have a stronger allelopathic capacity than female nigrum plants. That means that the magnitude of Empetrum allelopathic capacities likely vary with the relative abundance of intra-specific groups and sexes. These allelopathically distinct groups and sexes were used as a biological system to identify more potential Empetrum allelochemicals. The untargeted chemical analysis revealed an Empetrum chemical profile characterized by putative phenolics and terpenoids as expected, but also naphthalene- and alkaloid-derivatives which have not been recorded in Empetrum before. Chemical profiles were clearly distinct between the Empetrum groups, whereas there were no clear differences between the nigrum sexes. The allelopathic capacity of Empetrum may be driven by terpenoids, naphthalenes, alkaloids, and various phenolics besides Batatasin-III. Thereby, this thesis broadens our understanding of how Empetrum may chemically interact with its environment and is the first step towards expanding our mechanistic understanding of Empetrum allelopathic effects.
In conclusion, Icelandic Empetrum has a high allelopathic capacity and produces a wide range of potential allelochemicals by which it may contribute to keeping Icelandic tundra ecosystems trapped in degraded states. Future studies should aim to assess Empetrum allelopathic capacities in natural Icelandic tundra ecosystems and how they may change with climate warming.
Flokkar í Opnum vísindum
Veldu flokk til að skoða.
- University of Iceland
- University of Akureyri
- Bifröst University
- Hólar University College
- IRIS
- Agricultural University of Iceland
- National and University Library of Iceland
- Iceland University of the Arts