Publikationer från Umeå universitet
Not a member yet
55455 research outputs found
Sort by
Development of a Fourier Transform Spectrometer for Characterization of the Emission Spectrum of Superluminescent Diodes
No full textIn this project, a Fourier transform spectrometer (FTS) was developed to characterize the emission spectra of four different superluminescent diodes (SLDs): red, green, blue, and white. The spectrometer was based on a Michelson interferometer, enabling precise spectral analysis through interference-based measurements. To achieve accurate calibration of the optical path difference (OPD), a He-Ne laser was used as a reference to provide an equidistant sampling grid required for Fourier transformation. The moving mirror was translated at a constant velocity, and interferograms were recorded during the linear region where the signal remained stable. For each measurement, approximately 20,000 raw data points were collected per channel, and these were resampled based on the zero crossings of the He-Ne laser signal. Subsequently, Fourier transformation was applied to the resampled data to obtain the corresponding spectra. The resulting spectra successfully revealed the broadband emission characteristics of the SLDs. This study demonstrates that meaningful spectral information can be extracted using only a laser, a broadband source, and a few optical components, provided that appropriate signal processing techniques are applied. The results highlight the significance of the Fourier transform spectrometer design, which enables high-resolution spectral analysis through interferometric measurements
Active and healthy aging : the role of public, private and voluntary sectors in providing outdoor recreation for older adults
No full textAccess to outdoor leisure activities is central to supporting active and healthy ageing. To address the lack of research on services supporting continued engagement, this study examines how public, voluntary and private sectors provide outdoor recreation services for older adults. This study uses a qualitative research design to draw on interviews, a workshop, and field observations conducted in a Swedish municipality. Grounded in the capability approach and theories of active ageing, the study contributes to a better understanding of how opportunities for participation in outdoor recreation are shaped by service provision and structural conditions. This study identifies positive examples of outdoor recreation services but also gaps, characterised by the level of challenge in the activities that stakeholders in different sectors provide. Whereas activities provided by public senior centres were conducted in accessible terrain and inclusive for people with functional limitations, opportunities for slightly more challenging activities were lacking. Activities provided by voluntary organisations offered opportunities for more challenge, with the risk of exclusion for those with mobility limitations. The private sector, despite interest, did not actively provide outdoor recreation for older adults due to demand uncertainties. A structural barrier across all sectors was limited access to transport. This study contributes to the literature by identifying the need for tiered outdoor recreation programs, improved transport solutions, and cross-sector collaboration. While situated in a Swedish context, the findings offer conceptual and practical relevance for broader efforts to provide diversity in outdoor recreation services that support active ageing for different groups. A more coordinated, inclusive approach through policy and resource allocation across sectors is essential to support outdoor engagement in ageing populations.Accessible nature to promote active and healthy agein
BigOPERA : an OPportunistic and Elastic Resource Allocation for big data frameworks
No full textEfficient asset management is essential for optimizing the performance and scalability of modern Big Data (BD) frameworks. However, traditional resource allocation methods often suffer from static partitioning, inefficient resource utilization, and high operational costs, limiting their ability to adapt to fluctuating workloads dynamically. This paper introduces BigOPERA, an opportunistic and elastic resource allocation framework designed to enhance BD processing environments by integrating dedicated and non-dedicated computing assets. Leveraging containerization and a two-tiered scheduling mechanism, BigOPERA dynamically manages available resources to improve workload execution efficiency. Experimental results demonstrate that BigOPERA achieves up to 35% performance improvement over native Apache Spark configurations, significantly enhancing computational throughput while optimizing resource consumption. Our findings highlight the potential of BigOPERA in scalable, cost-effective, and sustainable BD processing
High-altitude retinopathy : a potential model for retinal haemorrhages in suspected shaken baby syndrome
No full textStridulation-like behaviour in the Red Wood ant (Formica rufa)
No full textInsects are known for communicating via sounds created by rubbing body parts, a behaviour referred to as stridulation. Red Wood ants (Formica rufa group) are not known to possess stridulatory organs and have historically been categorised as a non-stridulating species. In this exploratory study, we report that Red Wood ants generate stridulation-like sounds, being about 0.7 ± 0.2 seconds-long (mean ± standard deviation), rattling sounds that were repeatedly generated in our laboratory setting (about 0.6 productions h-1 individual-1). In addition, we assess Red Wood ant behavioural responses to playbacks of this stridulation-like sound. Our playback experiments show that the stridulation-like sound initiates a reduced locomotory speed among conspecifics, an effect not seen when the ants were exposed to silence. However, this response was not different from that generated by an artificial pure tone, making the use of this stridulation-like sound uncertain. We hypothesise that the stridulation-like sound is produced by rubbing the leg against a ridge structure located on the anterior margin of the pronotum, a structure that we describe using X-ray micro-tomography. Our exploratory study suggests that the recorded sound may be part of Formica ant communication that is hard to detect and easily missed in behavioural assays
Activation of the ChvG–ChvI pathway promotes survival during cell wall stress in Agrobacterium tumefaciens
No full textAgrobacterium tumefaciens shifts from a free-living soil bacterium to a plantinvading state upon encountering the plant root microenvironment. The acid-induced twocomponent sensor system ChvG–ChvI drives this shift and triggers a complex transcriptional program that promotes host invasion and survival against host immune defenses. Remarkably, ChvG–ChvI is also activated under cell wall stress conditions, suggesting that the transcriptional response may have a broader function. Here, we find that blocking cell wall synthesis either genetically or chemically leads to ChvG–ChvI activation. Mutations in key cell wall synthesis enzymes, such as penicillin-binding protein 1a and FtsW, suppress ChvG–ChvI activation in cell wall stress inducing conditions, suggesting that providing structural integrity is a primary function of the ChvG–ChvI regulon. Here, we investigated regulon components for this function. First, deletion of exoA, a gene required for production of the exopolysaccharide succinoglycan, confers resistance to multiple β-lactam antibiotics targeting different enzymes. Next, a class D β-lactamase is expressed that may contribute to the high level of β-lactam resistance in A. tumefaciens. Finally, outer membrane proteins are upregulated, suggesting that outer membrane remodeling may compensate for the accumulation of cell wall damage by providing structural integrity. Overall, we expand our understanding of mechanisms driving ChvG–ChvI activation and β-lactam resistance in a bacterial plant pathogen
MRI contrast accumulation in features of cerebral small vessel disease : blood-brain barrier dysfunction or elevated vascular density?
No full textBackground: White matter lesions (WML) and dilated perivascular spaces (PVS) are features of small vessel disease (SVD), commonly observed in aging and dementia, with unknown pathophysiology. Human studies have documented contrast accumulation within and in proximity of SVD-lesions. However, whether such observations mainly reflect excessive blood-brain barrier (BBB) leakage, or altered microvascular density in the investigated regions, remains unclear. Methods: To evaluate the roles of BBB leakage and vascular density in aging and SVD, dynamic contrast enhanced (DCE) MRI was used to estimate the permeability-surface area product (PS) and fractional plasma volume () in normal-appearing brain tissue and in proximity of and within WML and PVS in a population-based cohort (N = 56; 34/22 m/f; age 64 to 84 years). Analysis of variance (ANOVA) was used to assess regional differences in PS and and analysis of covariance (ANCOVA) was used to assess regional differences in PS with and vascular risk as covariates. Results: Pronounced increases in PS and were observed from normal-appearing white matter (NAWM) to WML peripheries to WMLs. Similar PS and increases were observed from basal ganglia (BG) to BG-PVS. Further, PS in NAWM and white matter (WM) PVS were found to increase with cortex-to-ventricular depth. However, ANCOVA models with as a covariate showed that variance in PS was mainly explained by vp (η2=0.17 to η2=0.35; all p < 10− 3), whereas the effect of region was only borderline-significant when comparing NAWM, WML peripheries and WML (p = 0.03) and non-significant for the other comparisons (p > 0.29). Conclusions: Our findings support the notion that contrast leakage across the BBB accumulates within and in proximity of SVD-related lesions. However, high contrast accumulation may mainly reflect high vascularization, and to a lesser degree than previously recognized BBB dysfunction
The conspiracy capitaliser : a tool for exploring the intersection of AI, politics and profit
No full textThe Conspiracy Capitaliser is a physical interface for Generative AI which allows the user to produce a bespoke conspiracy through the operation of knobs, switches and buttons. The original intent of the artefact was as a personal exploration of how conspiracy theories were being monetised against a backdrop of social media disinformation and how these observations could be communicated to the general public. While the artefact began as a non-functioning sculptural work, the advent of accessible AI models like ChatGPT allowed it to become fully functional and transformed it into a useful tool for design ethics, public awareness and a better understanding of the systems that lie behind these emerging technologies. This paper describes the evolution of the Conspiracy Capitaliser through its conception, creation, its exhibition and how it became a multi-faceted lens through which both the designer and the public could explore problematic intersections of profit and technology.DCODEUmArt
Agonistic design in practice : introducing agonism to interaction design pedagogy
No full textIn an increasingly technology-mediated world, agonistic design seeks to support agency over convenience in an attempt to give the user more determination over the technologies which may adversely affect them. This paper explores the experimental integration of agonistic design principles into an Interaction Design Masters course to address the emerging harms of algorithmic decision systems (ADS). Conducted with Interaction Design Master’s students at a Swedish University, the intervention introduced agonistic design through a seminar, tutorials, and projects which move from ideation, to prototyping, ending with public exhibition and reflection exercise. Drawing on frameworks supporting democratic design and constructive disagreement, the course challenged students to balance critical perspectives with practical design considerations. While challenges in adoption persisted, the experiment demonstrated its potential to foster critical engagement with emerging technologies. The findings inform future efforts to develop toolkits and promote sustainable socio-technical practices in design education and beyond.DCOD
Competition and cooperation : the plasticity of bacterial interactions across environments
No full textBacteria live in diverse communities, forming complex networks of interacting species. A central question in bacterial ecology is whether species engage in cooperative or competitive interactions. But this question often neglects the role of the environment. Here, we use genome-scale metabolic networks from two different open-access collections (AGORA and CarveMe) to assess pairwise interactions of different microbes in varying environmental conditions (provision of different environmental compounds). By computationally simulating thousands of environments for 10,000 pairs of bacteria from each collection, we found that most pairs were able to both compete and cooperate depending on the availability of environmental resources. This modeling approach allowed us to determine commonalities between environments that could facilitate the potential for cooperation or competition between a pair of species. Namely, cooperative interactions, especially obligate, were most common in less diverse environments. Further, as compounds were removed from the environment, we found interactions tended to degrade towards obligacy. However, we also found that on average at least one compound could be removed from an environment to switch the interaction from competition to facultative cooperation or vice versa. Together our approach indicates a high degree of plasticity in microbial interactions in response to the availability of environmental resources