Opin vísindi

 

Nýlega bætt við

Verk
Hot, tired and hungry : The snacking behaviour and food cravings of firefighters during multi-day simulated wildfire suppression
(2020-04) Gupta, Charlotte C.; Ferguson, Sally A.; Aisbett, Brad; Dominiak, Michelle; Chappel, Stephanie E.; Sprajcer, Madeline; Fullagar, Hugh H.K.; Khalesi, Saman; Guy, Joshua H.; Vincent, Grace E.; Department of Sport Science
Firefighters are exposed to numerous stressors during wildfire suppression, including working in hot temperatures and sleep restricted conditions. Research has shown that when sleep restricted, individuals choose foods higher in carbohydrates, fat, and sugar, and have increased cravings for calorie dense foods. However, there is currently no research on the combined effect of heat and sleep restriction on snacking behaviour. Conducting secondary analyses from a larger study, the current study aimed to investigate the impact of heat and sleep restriction on snacking behaviour and food cravings. Sixty-six firefighters completed three days of simulated physically demanding firefighting work and were randomly allocated to either the control (n = 18, CON; 19 °C, 8h sleep opportunity), sleep restricted (n = 16, SR; 19 °C, 4-h sleep opportunity), hot (n = 18, HOT; 33 °C, 8h sleep opportunity), or hot and sleep restricted (n = 14 HOT + SR; 33 °C, 4-h sleep opportunity) condition. During rest periods firefighters were able to self-select sweet, savoury, or healthy snacks from a ration pack and were asked to rate their hunger, fullness, and cravings every two hours (eating block). Mixed model analyses revealed no difference in total energy intake between conditions, however there was a significant interaction between eating block and condition, with those in the CON, HOT, and HOT + SR condition consuming significantly more energy between 1230 and 1430 compared to the SR condition (p = 0.002). Sleep restriction and heat did not impact feelings of hunger and fullness across the day, and did not lead to greater cravings for snacks, with no differences between conditions. These findings suggest that under various simulated firefighting conditions, it is not the amount of food that differs but the timing of food intake, with those that are required to work in hot conditions while sleep restricted more likely to consume food between 1230 and 1430. This has potential implications for the time of day in which a greater amount of food should be available for firefighters.
Verk
Optimal Metastability-Containing Sorting via Parallel Prefix Computation
(2020-02-01) Bund, Johannes; Lenzen, Christoph; Medina, Moti; Department of Computer Science
Friedrichs et al. (TC 2018) showed that metastability can be contained when sorting inputs arising from time-to-digital converters, i.e., measurement values can be correctly sorted without resolving metastability using synchronizers first. However, this work left open whether this can be done by small circuits. We show that this is indeed possible, by providing a circuit that sorts Gray code inputs (possibly containing a metastable bit) and has asymptotically optimal depth and size. Our solution utilizes the parallel prefix computation (PPC) framework (JACM 1980). We improve this construction by bounding its fan-out by an arbitrary f\geq 3f≥3, without affecting depth and increasing circuit size by a small constant factor only. Thus, we obtain the first PPC circuits with asymptotically optimal size, constant fan-out, and optimal depth. To show that applying the PPC framework to the sorting task is feasible, we prove that the latter can, despite potential metastability, be decomposed such that the core operation is associative. We obtain asymptotically optimal metastability-containing sorting networks. We complement these results with simulations, independently verifying the correctness as well as small size and delay of our circuits. Proofs are omitted in this version; the article with full proofs is provided online at http://arxiv.org/abs/1911.00267.
Verk
Environmental and individual correlates of depressive symptoms in Iceland : The role of season, environmental mood responses and circadian preference
(University of Akureyri, 2026-11) Zelinski, Lada; Höller, Yvonne; Ólafsson, Ragnar P.; Bathke, Arne C.; Centre for Doctoral Studies
Í þessari ritgerð er sjónum beint, í þremur rannsóknum, að umhverfis- og eintaklingsbundnum þáttum í þunglyndiseinkennum á Íslandi -landi sem liggur norðarlega og mikill munur er á dagsbirtu og veðurfari eftir árstíðum. Í fyrstu rannsókninni var notaður skimunarlisti ásamt hálfstöðluðu geðgreiningarviðtali til að meta árstíðabundnar sveiflur í þunglyndiseinkennum og þunglyndisröskun í lagskiptu úrtaki Íslendinga. Vegið algengi árstíðabundins þunglyndis var mun hærra samkvæmt skimunarlista, eða 17,86%, heldur en samkvæmt geðgreiningarviðtali, eða 2,24%, sem er í samræmi við rannsóknir í löndum nær miðbaug og bendir til ofmats á áhrifum hnattlegu landa á þunglyndi, ef sjálfsmatsskimunarlistar eru eingöngu notaðir. Í annarri rannsókninni voru skoðuð tengsl skaps fólks við staðbundið hita- og birtustig og hvort þeir þættir tengdust alvarleika þunglyndiseinkenna. Niðurstöður sýndu að verra skap þegar kalt var í veðri og dagsbirta minni, tengdist alvarlegri einkennum og að tengsl hitastigs og þunglyndiseinkenna var háð (ó)þoli fólks fyrir kaldara hitastigi. Í þriðju rannsókninni var dægursveifluhneigð og neysla orkudrykkja skoðuð í tengslum við einkenni þunglyndis og svefnleysis með árstíðabundnum mælingum í eitt ár. Niðurstöður sýndu að kvöldhneigt fólk hafði meiri þunglyndiseinkenni á grunnlínu að sumri og að neysla orkudrykkja tengdist þunglynlyndiseinkennum þegar tók að hausta, sér í lagi hjá kvöldheigðu fólki. Samantekið, benda niðurstöður þessara þriggja rannsókna til að árstíðabundið þunglyndi, greint sem geðröskun í geðgreiningarviðtali, sé tiltölulega sjaldgæft en að sveiflur í þunglyndiseinkennum eftir árstíðum sé mun algengari þegar miðað er við sjálfsmat fólks. Niðurstöðurnar benda einnig til að áhrif umhverfisþátta á þunglyndiseinkenni séu háð einstaklingsbundnu mati og þoli fólks, frekar en þáttunum einum og sér og að tengsl orkudrykkja við þunglyndiseinkenni séu háð dægursveifluhneigð og árstíðum. Niðurstöður rannsóknaverkefnisins benda til að tengsl árstíðabundninna umhverfisþátta og þunglyndiseinkenna séu háð einstaklingsbundnum tilhneigingum. Loftslagsbreytingar móta umhverfi og aðstæður fólks. Aukinn skilningur á samspili umhverfis og einstaklingsbundinna þátta er því mikilvægur og getur nýst til að afmarka viðkvæma hópa og veita markvissari fræðslu og stuðning.
Verk
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.
Verk
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.

Flokkar í Opnum vísindum

Veldu flokk til að skoða.

Niðurstöður 1 - 9 af 9

Öll gögn í Opnum vísindum eru vernduð af ákvæðum höfundalaga og með öllum réttindum áskildum, nema annað sé tekið fram.