| 1. |
- Aarstad, Olav, et al.
(författare)
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Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils
- 2017
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.
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| 2. |
- Aslam, Tayyba N., et al.
(författare)
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A survey of preferences for respiratory support in the intensive care unit for patients with acute hypoxaemic respiratory failure
- 2023
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Ingår i: Acta Anaesthesiologica Scandinavica. - : WILEY. - 0001-5172 .- 1399-6576. ; 67:10, s. 1383-1394
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundWhen caring for mechanically ventilated adults with acute hypoxaemic respiratory failure (AHRF), clinicians are faced with an uncertain choice between ventilator modes allowing for spontaneous breaths or ventilation fully controlled by the ventilator. The preferences of clinicians managing such patients, and what motivates their choice of ventilator mode, are largely unknown. To better understand how clinicians preferences may impact the choice of ventilatory support for patients with AHRF, we issued a survey to an international network of intensive care unit (ICU) researchers.MethodsWe distributed an online survey with 32 broadly similar and interlinked questions on how clinicians prioritise spontaneous or controlled ventilation in invasively ventilated patients with AHRF of different severity, and which factors determine their choice.ResultsThe survey was distributed to 1337 recipients in 12 countries. Of these, 415 (31%) completed the survey either fully (52%) or partially (48%). Most respondents were identified as medical specialists (87%) or physicians in training (11%). Modes allowing for spontaneous ventilation were considered preferable in mild AHRF, with controlled ventilation considered as progressively more important in moderate and severe AHRF. Among respondents there was strong support (90%) for a randomised clinical trial comparing spontaneous with controlled ventilation in patients with moderate AHRF.ConclusionsThe responses from this international survey suggest that there is clinical equipoise for the preferred ventilator mode in patients with AHRF of moderate severity. We found strong support for a randomised trial comparing modes of ventilation in patients with moderate AHRF.
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| 3. |
- Broekman, Maarten J. E., et al.
(författare)
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Evaluating expert-based habitat suitability information of terrestrial mammals with GPS-tracking data
- 2022
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 31:8, s. 1526-1541
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Macroecological studies that require habitat suitability data for many species often derive this information from expert opinion. However, expert-based information is inherently subjective and thus prone to errors. The increasing availability of GPS tracking data offers opportunities to evaluate and supplement expert-based information with detailed empirical evidence. Here, we compared expert-based habitat suitability information from the International Union for Conservation of Nature (IUCN) with habitat suitability information derived from GPS-tracking data of 1,498 individuals from 49 mammal species.Location: Worldwide.Time period: 1998-2021.Major taxa studied: Forty-nine terrestrial mammal species.Methods: Using GPS data, we estimated two measures of habitat suitability for each individual animal: proportional habitat use (proportion of GPS locations within a habitat type), and selection ratio (habitat use relative to its availability). For each individual we then evaluated whether the GPS-based habitat suitability measures were in agreement with the IUCN data. To that end, we calculated the probability that the ranking of empirical habitat suitability measures was in agreement with IUCN's classification into suitable, marginal and unsuitable habitat types.Results: IUCN habitat suitability data were in accordance with the GPS data (> 95% probability of agreement) for 33 out of 49 species based on proportional habitat use estimates and for 25 out of 49 species based on selection ratios. In addition, 37 and 34 species had a > 50% probability of agreement based on proportional habitat use and selection ratios, respectively.Main conclusions: We show how GPS-tracking data can be used to evaluate IUCN habitat suitability data. Our findings indicate that for the majority of species included in this study, it is appropriate to use IUCN habitat suitability data in macroecological studies. Furthermore, we show that GPS-tracking data can be used to identify and prioritize species and habitat types for re-evaluation of IUCN habitat suitability data.
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| 4. |
- Herfindal, Ivar, et al.
(författare)
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Population persistence in a landscape context : the case of endangered arctic fox populations in Fennoscandia
- 2010
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 33:5, s. 932-941
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic fragmentation of habitat and populations is recognized as one of the most important factors influencing loss of biodiversity. Since it is difficult to quantify demographic parameters in small populations, we need alternative methods to elucidate important factors affecting the viability of local populations. The Fennoscandian arctic fox inhabits a naturally fragmented alpine tundra environment, but historic anthropogenic impacts have further fragmented its distribution. After almost 80 yr of protection, the population remains critically endangered. Both intrinsic factors (related to the isolation and size of sub-populations) and extrinsic factors (related to environmental conditions influencing patch quality and interspecific competition) have been proposed as explanations for the lack of population growth. To distinguish between these hypotheses, we conducted a spatially explicit analysis that compares areas where the species has persisted with areas where it has become locally extinct. We used characteristics of the fragments of alpine tundra habitat and individual arctic fox breeding dens (including both currently active dens and historically active dens) within the fragments to evaluate the importance of habitat characteristics and connectivity in explaining variation in persistence within a fragment. The number of reproductive events in a fragment was related to the size of the fragment, but not more than expected following a 1:1 relationship, suggesting little effect of fragment size on the relative number of reproductions. The likelihood of a den being used for breeding was positively associated with factors minimising interspecific competition as well as increasing within-fragment connectivity. These results support the idea that the failure of Fennoscandian arctic fox to recover is caused by demographic factors that can be related to fine-scale Allee or Allee-like effects, as well as environmental influences related to increased competition and exclusion by red foxes
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| 5. |
- Herum, Kate M., et al.
(författare)
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Syndecan-4 Protects the Heart From the Profibrotic Effects of Thrombin-Cleaved Osteopontin
- 2020
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Ingår i: Journal of the American Heart Association. - 2047-9980. ; 9:3, s. 013518-013518
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Tidskriftsartikel (refereegranskat)abstract
- Background: Pressure overload of the heart occurs in patients with hypertension or valvular stenosis and induces cardiac fibrosis because of excessive production of extracellular matrix by activated cardiac fibroblasts. This initially provides essential mechanical support to the heart, but eventually compromises function. Osteopontin is associated with fibrosis; however, the underlying signaling mechanisms are not well understood. Herein, we examine the effect of thrombin-cleaved osteopontin on fibrosis in the heart and explore the role of syndecan-4 in regulating cleavage of osteopontin. Methods and Results: Osteopontin was upregulated and cleaved by thrombin in the pressure-overloaded heart of mice subjected to aortic banding. Cleaved osteopontin was higher in plasma from patients with aortic stenosis receiving crystalloid compared with blood cardioplegia, likely because of less heparin-induced inhibition of thrombin. Cleaved osteopontin and the specific osteopontin peptide sequence RGDSLAYGLR that is exposed after thrombin cleavage both induced collagen production in cardiac fibroblasts. Like osteopontin, the heparan sulfate proteoglycan syndecan-4 was upregulated after aortic banding. Consistent with a heparan sulfate binding domain in the osteopontin cleavage site, syndecan-4 was found to bind to osteopontin in left ventricles and cardiac fibroblasts and protected osteopontin from cleavage by thrombin. Shedding of the extracellular part of syndecan-4 was more prominent at later remodeling phases, at which time levels of cleaved osteopontin were increased. Conclusions: Thrombin-cleaved osteopontin induces collagen production by cardiac fibroblasts. Syndecan-4 protects osteopontin from cleavage by thrombin, but this protection is lost when syndecan-4 is shed in later phases of remodeling, contributing to progression of cardiac fibrosis.
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| 6. |
- Strand, Olav, et al.
(författare)
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Vindkraft och renar : En kunskapssammanställning
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna rapport har vi sammanfattat elva olika undersökningar som studerat effekterna av vindkraftparker och kraftledningar på renar. Effekterna av tekniska ingrepp och störningar i allmänhet, och effekter av vindkraftparker i synnerhet, har studerats av olika forskargrupper. Dessa insatser har gjort att vi idag har bättre kunskap om anläggningars effekter på renar och rennäringen. Vid en del tillfällen har olika undersökningar gett till synes motstridiga resultat. I denna rapport försöker vi förklara de olika resultaten från respektive undersökning.Med detta som bakgrund drar vi slutsatsen att en vindkraftpark alltid potentiellt kan ge negativa effekter på miljö och samhälle. Dessa effekter och påverkansfaktorer sammanfattas nedan. Påverkansfaktorerna bör ses i ett sammanhang, där ett vindkraftverk bör betraktas som en enhet där summan av påverkansfaktorerna ger en samlad effekt. Dessutom bör de kumulativa effekterna av annan belastning i området som påverkar renbetesområdena tas med i värderingen av effekterna från en vindkraftsanläggning. För att förstå de samlade effekterna är det viktigt att inkludera alla årstider i undersökningarna och att täcka en tidshorisont som är lång nog för att fånga upp miljömässiga variationer och därmed också ändringar i användningen av betesområden. Utöver detta bör man beakta annan mänsklig aktivitet och ingrepp som gjorts i området innan vindkraftverk etablerats.Vägar: Vägar medför ökad trafik och ökad tillgänglighet. Renar undviker vägar och de leder till att renarnas naturliga rörelsemönster hindras. Undantag från detta kan vara vägar som byggs i områden som redan har mycket infrastruktur eller vägar som har mycket lite trafik. Erfarenheterna visar att stängning av vägar kan vara en effektiv åtgärd, men svår att upprätthålla över tid.Kraftledningar: Effekterna av kraftledningar är fortsatt oklara. Nyare studier där man använt GPS och data som samlats in före och efter utbyggnad visar att byggarbeten kan leda till ett relativt starkt undvikande. Men undersökningarna visar också att kraftledningar i driftsperioden om sommaren och hösten har mindre negativa effekter än vad som tidigare antagits. Renar har en förmåga att se UV-ljus under vintern. Hypoteser som förklarar de till synes varierande effekterna av kraftledningar bör följas upp med detaljerade undersökningar, särskilt med avseende på effekter på vintern.Vindkraftverk och rotorer: Vid två av de undersökta vindkraftsparkerna i Sverige och i en ny studie från Norge har man funnit att renar har reducerat sin användning av områden som ligger inom 3–5 km från sådana anläggningar. Samtidigt har en studie i Sverige och tre undersökningar i Norge inte dokumenterat någon reducerad habitatanvändning i närområdet till vindkraftsanläggningar. Vi diskuterar orsaken till detta och ger förklaringar till de olika resultaten. De kan bero både på topografi, betesförhållanden, närhet till annan infrastruktur och försöksdesign av de olika undersökningarna.För att stärka kunskapen om effekter av vindkraftverk på renar finns behov av långsiktiga studier. Dessa bör ta hänsyn till de samlade effekterna av vindkraftverk och se på betydelsen av den samlade belastningen inom renbetesområdet. Undersökningarna bör vara långsiktiga (pågå över flera år) för att ge en förståelse av hur årsvariationen påverkar habitatanvändning och andra faktorer mellan åren. Sådana framtida studier bör också inkludera samhällsvetenskapliga studier och integrera lokal och kulturell kunskap.Avslutningsvis ger vi rekommendationer om framtida forskningssatsningar om renar, renskötsel och vindkraft. Vi diskuterar också hur traditionell kunskap bör integreras i framtida undersökningar för att forskningen ska kunna ta fram ett kunskapsunderlag som är så relevant som möjligt.
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