Publikationer från Umeå universitet
Not a member yet
55455 research outputs found
Sort by
To own or share e-scooters? : Factors in ownership and sharing of e-scooters
No full textThis paper aims to determine how consumer innovativeness, susceptibility to interpersonal influence, personal norms, and innovation attribute perceptions affect the consumer decision to use, share, and own an e-scooter. The decision to use encompasses traveling using an e-scooter, sharing means using an e-scooter on a demand basis, and owning means buying an e-scooter for personal use. Consequently, this paper contributes to understanding novel mobility modes that aim to decrease the environmental problems in transport. It also develops knowledge about green innovations that could be perceived as causing more environmental problems than their traditional counterparts. A survey was conducted in Sweden with 1002 participants, who were non-users, owners, and sharers of e-scooters. Structural equation modelling showed that susceptibility to interpersonal influence and perceived safety attributes of e-scooters consistently positively influence decisions to use and own. This paper increases the understanding of factors influencing e-scooter use, sharing, and ownership, which is valuable for e-scooter businesses and service providers, transport agencies, and policy-maker
Near triple arrays
No full textWe introduce near triple arrays as binary row-column designs with at most two consecutive values for the replication numbers of symbols, for the intersection sizes of pairs of rows, pairs of columns and pairs of a row and a column. Near triple arrays form a common generalization of such well-studied classes of designs as triple arrays, (near) Youden rectangles and Latin squares. We enumerate near triple arrays for a range of small parameter sets and show that they exist in the vast majority of the cases considered. As a byproduct, we obtain the first complete enumerations of 6×10 triple arrays on 15 symbols, 7×8 triple arrays on 14 symbols and 5×16 triple arrays on 20 symbols. Next, we give several constructions for families of near triple arrays, and e.g. show that near triple arrays with 3 rows and at least 6 columns exist for any number of symbols. Finally, we investigate a duality between row and column intersection sizes of a row-column design, and covering numbers for pairs of symbols by rows and columns. These duality results are used to obtain necessary conditions for the existence of near triple arrays. This duality also provides a new unified approach to earlier results on triple arrays and balanced grids
Biogeochemical response to drying-rewetting in riparian soils influences carbon mobilization
No full textOrganic-rich riparian soils in northern boreal landscapes are often the primary source of organic and inorganic carbon (C) to headwater streams. During extreme hydro-climatic events, such as droughts, the production and mobilization of C in these soils may be sensitive to changes in groundwater levels. Yet, the biogeochemical effects of drying and rewetting have been under-investigated in boreal riparian zones, particularly when compared to peat soils in discrete landscape components (i.e., mires). Here, we experimentally assess the response of riparian soil cores to simulated drought and rewetting and test whether mobilization of dissolved organic matter (DOM), carbon dioxide (CO2), and methane (CH4) are altered by geochemical and biological drivers over a two-month rewetting period. Drought oxidized the soil profile, upregulated activities of oxidative enzymes, and replenished terminal electron acceptors (TEAs), most notably sulfate (SO42−), which likely suppressed DOM concentrations over the short term. However, over the longer term, soil DOM mobilization increased in response to rewetting, unrelated to the intensity of experimental drought. Enzyme activity during the rewetting phase indicates that the persistent increases in DOM may be linked to microbially-mediated decomposition of organic matter following drought. By contrast, CO2 production was sensitive to drought intensity, with concentrations suppressed in soils subjected to the most extreme drying treatment. Elevated SO42− concentrations also delayed the recovery of CH4 production in soils by creating a pool of more favorable TEAs. Our results collectively show that mobilization of different C forms in riparian soils is influenced by drying-rewetting events through multiple biogeochemical mechanisms operating at different time scales. These findings have broader implications for the lateral transfer of organic and inorganic C from riparian zones to streams in response to predicted increases in climate variability
Sublingual immunotherapy in children with asthma : a population-based register study
No full textBackground: Daily sublingual immunotherapy (SLIT) for 3 years reduces symptoms of allergic disease and induces tolerance. Real-life data from children with asthma receiving SLIT are scarce. Objective: We used population-based data to describe characteristics, SLIT duration, and changes in morbidity in children with asthma prescribed SLIT. Methods: The study included children (5-17 years) with asthma who were prescribed SLIT, and who were registered in the Swedish National Airway Register (SNAR) before SLIT initiation (N = 1,514), of whom 782 had post-SLIT recordings in the SNAR. Age, sex, Asthma Control Test score (≤19 denotes uncontrolled asthma), spirometry data, number of SLIT tablets dispensed, and socioeconomic background were extracted from the SNAR and other national registers. SLIT duration was classified as <4, ≥4, >12, or >24 months. Results: SLIT was more common in boys (69%) and adolescents (71%). Most children had parents with higher education (70%), and 25% had uncontrolled asthma. SLIT duration of ≥4, >12, and >24 months was identified in 86%, 50%, and 30%, respectively. Parents with higher education were associated with SLIT duration of ≥4 months (odds ratio = 3.69; 95% confidence interval 2.75-4.96). SLIT duration of >12 months was associated with lower risk of post-SLIT uncontrolled asthma (adjusted odds ratio = 0.49; 95% confidence interval, 0.25-0.99). No associations were found between SLIT duration of ≥4, >12, or >24 months and changes in spirometry. Conclusion: Longer SLIT duration was associated with higher education in parents and lower risk of uncontrolled asthma. Measures to improve persistence in SLIT in children with asthma may have important clinical implications
Invasive Eurasian minnow alters the trophic niche and growth of brown trout in high-latitude lakes
No full textInvasive species pose a major threat to aquatic ecosystems, particularly in high-latitude lakes which are characterised by low biodiversity. In northern Europe, the Eurasian minnow (Phoxinus phoxinus) has colonised lakes historically dominated by salmonids, raising concerns about the impacts of invasive cyprinids on native fish populations and food webs. We compared the trophic niche, growth, and maturation of brown trout (Salmo trutta) in lakes with and without minnow and assessed dietary overlap between the two species using stomach content and stable isotope analyses. Stable isotope analysis revealed that in lakes with minnow, trout exhibited more pronounced ontogenetic niche shifts from pelagic to littoral feeding and towards higher trophic positions compared to lakes with only trout. The isotope data also showed that small trout overlapped in trophic niche with minnows. Stomach content analysis revealed a shift in trout prey use, with reduced consumption of Eurycercus lamellatus and Gammarus lacustris, increased use of surface insects and a transition towards partial piscivory (prevalence of piscivory 5.5%). Despite potential resource competition at early life stages and shifts in diet, when coexisting with minnow, trout grew faster and females showed a tendency to mature earlier. Overall, the presence of invasive minnow does not appear to negatively affect native trout. This is likely due to a combination of flexible resource use and the opportunistic piscivory exhibited by trout. Since our study systems were recently invaded, the findings provide new insights into how native salmonids respond to invasive species shortly after their establishment in small high-latitude lakes
Bisection width, discrepancy, and eigenvalues of hypergraphs
No full textA celebrated result of Alon from 1993 states that any d-regular graph on n vertices (where d=O(n1/9)) has a bisection with at most [Formula presented.] edges, and this is optimal. Recently, this result was greatly extended by Räty, Sudakov, and Tomon. We build on the ideas of the latter, and use a semidefinite programming inspired approach to prove the following variant for hypergraphs: every r-uniform d-regular hypergraph on n vertices (where d≪n1/2) has a bisection of size at most [Formula presented.] for some c=c(r)>0. This bound is the best possible up to the precise value of c. Moreover, a bisection achieving this bound can be found by a polynomial-time randomized algorithm. The minimum bisection is closely related to discrepancy. We also prove sharp bounds on the discrepancy and so called positive discrepancy of hypergraphs, extending results of Bollobás and Scott. Furthermore, we discuss implications about Alon-Boppana type bounds. We show that if H is an r-uniform d-regular hypergraph, then certain notions of second largest eigenvalue λ2 associated with the adjacency tensor satisfy λ2≥Ωr(d), improving results of Li and Mohar
Near infrared spectroscopy versus stump pressure in detecting cerebral ischemia during carotid endarterectomy : a prospective multicenter observational study
No full textBackground: Determining the need for shunt use during carotid endarterectomy (CEA) under general anesthesia (GA) can be based on different methods, and one of the most common is stump pressure (SP). Previous studies have found favorable results of near infrared spectroscopy (NIRS). Methods: Patients undergoing CEA in 2 swedish hospitals were prospectively included. SP, rSO2 at different timepoints as well as neurological symptoms during surgery were reported for all patients. Receiver operating curve (ROC) analysis was used to determine the optimal cutoff points for SP and rSO2. Results: A total of 293 patients underwent CEA under local anesthesia (LA) and 66 under GA in 2 hospitals. Thirty two patients operated under LA had neurological symptoms. A relative change in ipsilateral rSO2 ≤ −9% had a negative predictive value (NPV) of 99% in detecting neurological symptoms during clamping. Patients who developed neurological symptoms during clamping had lower ΔrSO2 (−14% ± 6% vs. −4 ± 5%, P < 0.001) and lower SP (36 ± 21 mm Hg vs. 56 ± 19 mm Hg, P < 0.001) compared to those who did not. A ΔrSO2 of ≤ −9% had a sensitivity of 91% (95% confidence interval (CI): 75–98%) and a specificity of 82% (95% CI: 77–87%) in predicting cerebral ischemia, whereas a SP < 50 mm Hg had a sensitivity of 78% (95% CI: 58–91%) and a specificity of 60% (95% CI: 54–67%). Conclusion: This study found that NIRS could reduce unnecessary shunting while still having a higher sensitivity compared to SP. Additionally, it can also monitor shunt patency
Your everyday hero: media representations of civic safety engagements
No full textThis article explores how civil society-based safety engagements are represented in Swedish news media, and how these representations are mediated through emotions. In a political climate where “increased safety” has become a dominant goal, we analyze how media narratives construct emotional regimes around safety and responsibility. Drawing on Stuart Halls work on representation and theories of emotions, we show how news media not only reflect but help (re)produce emotional and spatial geographies of (un)safety through personalized storytelling and emotive language. Focusing on personal portrayals of grassroots safety initiatives, such as women-led taxi services and local volunteer efforts, we demonstrate how emotions such as fear and frustration are articulated as morally productive and politically legitimate responses to unsafety. These narratives represent engagement as a matter of individual initiative and personal responsibility, often along gendered and racialized lines. Women are depicted as self-governing subjects whose emotional investments justify their civic actions, aligning with neoliberal ideals of responsibilized citizenship. Media participates in an emotional politics that valorizes agency and affective community while depoliticizing broader issues of inequality and exclusion. These representations risk obscuring the structural causes of unsafety by recasting safety as a matter of personal duty rather than collective or institutional responsibility
From precision to perception: Human-in-the-loop evaluation of keyword extraction for internet-scale contextual advertising
No full textKeyword extraction is a foundational task in natural language processing, underpinning countless real-world applications. One of these is contextual advertising, where keywords help predict the topical congruence between ads and their surrounding media contexts to enhance advertising effectiveness. Recent advances in artificial intelligence have improved keyword extraction capabilities but also introduced concerns about computational cost. Moreover, although the end-user experience is of vital importance, human evaluation of keyword extraction performances remains under-explored. This study provides a comparative evaluation of prevalent keyword extraction algorithms with different levels of complexity represented by TF-IDF, KeyBERT, and Llama 2. To evaluate their effectiveness, a mixed-methods approach is employed, combining quantitative benchmarking with qualitative assessments from 855 participants through four survey-based experiments. The findings demonstrate that KeyBERT achieves an effective balance between user preferences and computational efficiency, compared to the other algorithms. We observe a clear overall preference for gold-standard keywords, but there is a misalignment between algorithmic benchmark performance and user ratings. This reveals a long-overlooked gap between traditional precision-focused metrics and user-perceived algorithm efficiency. The study underscores the importance of human-in-the-loop evaluation methodologies and proposes analytical tools to facilitate their implementation
Lack of increase in mercury contamination in coastal Western Australia since European settlement
No full textCurrent knowledge of long-term mercury (Hg) deposition is predominantly based on studies from the Northern Hemisphere, leading to a geographical bias in the comprehension of the global Hg cycle. Aiming to contribute to fill this knowledge gap, our study presents a high-resolution Hg record of a seagrass Posidonia australis sedimentary archive encompassing the last 3300 years in the Waychinicup estuary (Western Australia, WA). This setting is an ideal site for studying the natural Hg cycle, as it is located in the southwest of the state, outside the prevailing wind patterns that transport emissions from major Hg sources. Our results show that Hg concentrations fluctuated from ∼1300 BCE to 100 CE with a shift in the paleorecord around 350 BCE, which could potentially be associated with an intensified El Niño Southern Oscillation period. From around 100 until ∼1880 CE, the Hg concentration remained relatively constant (∼2 μg kg−1) with an increase up to 8 μg kg−1 from 1880 CE until present. Although Hg accumulation doubled since European settlement in WA (from 2.4 to 4.8 μg m−2 yr−1), such an increase can be explained by enhanced organic carbon accumulation, rather than changes in external Hg fluxes. Therefore, our study showcases the importance of considering biogeochemical processes when reconstructing long-term Hg accumulation based on sedimentary archives. Furthermore, the results demonstrate the key role of seagrass meadows as natural paleoarchives of environmental contamination, providing valuable insights into human impacts on coastal areas and to establish pre-anthropogenic baseline metal concentrations