| 1. |
- Aad, G., et al.
(author)
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- 2013
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Journal article (peer-reviewed)
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| 2. |
- Aad, G., et al.
(author)
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- 2013
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Journal article (peer-reviewed)
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| 3. |
- de Rezende, Susanna F.
(author)
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Lower Bounds and Trade-offs in Proof Complexity
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Propositional proof complexity is a field in theoretical computer science that analyses the resources needed to prove statements. In this thesis, we are concerned about the length of proofs and trade-offs between different resources, such as length and space.A classical NP-hard problem in computational complexity is that of determining whether a graph has a clique of size k. We show that for all k ≪ n^(1/4) regular resolution requires length n^Ω(k) to establish that an Erdős–Rényi graph with n vertices and appropriately chosen edge density does not contain a k-clique. In particular, this implies an unconditional lower bound on the running time of state-of-the-artalgorithms for finding a maximum clique.In terms of trading resources, we prove a length-space trade-off for the cutting planes proof system by first establishing a communication-round trade-off for real communication via a round-aware simulation theorem. The technical contri-bution of this result allows us to obtain a separation between monotone-AC^(i-1) and monotone-NC^i.We also obtain a trade-off separation between cutting planes (CP) with unbounded coefficients and cutting planes where coefficients are at most polynomial in thenumber of variables (CP*). We show that there are formulas that have CP proofs in constant space and quadratic length, but any CP* proof requires either polynomial space or exponential length. This is the first example in the literature showing any type of separation between CP and CP*.For the Nullstellensatz proof system, we prove a size-degree trade-off via a tight reduction of Nullstellensatz refutations of pebbling formulas to the reversible pebbling game. We show that for any directed acyclic graph G it holds that G can be reversibly pebbled in time t and space s if and only if there is a Nullstellensatzrefutation of the pebbling formula over G in size t + 1 and degree s.Finally, we introduce the study of cumulative space in proof complexity, a measure that captures the space used throughout the whole proof and not only the peak space usage. We prove cumulative space lower bounds for the resolution proof system, which can be viewed as time-space trade-offs where, when time is bounded, space must be large a significant fraction of the time.
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| 4. |
- Belle, Simon
(author)
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Abrupt rise in the contribution of CH4-derived carbon to benthic secondary production of a shallow hemiboreal/boreal lake
- 2018
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In: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 33, s. 969-976
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Journal article (peer-reviewed)abstract
- Understanding long-term carbon flows through aquatic food webs is essential to assess impact of climatic and environmental changes on lake ecosystems. We reconstructed temporal changes in carbon sources fuelling chironomid biomass in a small and shallow hemiboreal/boreal lake over the last 11 000 years. Results were compared with temporal dynamics of known potential controlling factors: summer air temperature, human activities, phytoplankton assemblages and organic matter composition. We report an abrupt rise in the contribution of methane-derived carbon to chironomid biomass. However, this sudden increase was not the consequence of drastic changes in the composition of sedimentary organic matter, mean air temperature, lake trophic state or human activities in the catchment area. Our results suggest that shallowing of the lake caused by sedimentary infilling processes was a possible driver of the expansion of anoxic zones, enhancing CH4 cycling in lake sediments. However, complementary studies are needed to better understand the mechanisms by which lake shallowing could affect carbon flows to aquatic consumers, and then better assess the natural dynamics of past carbon processing in the benthic food web of shallow lakes.
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| 5. |
- Belle, Simon, et al.
(author)
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Acidification of freshwater lakes in Scandinavia: impacts and recovery of chironomid communities under accelerating environmental changes
- 2024
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In: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 851, s. 585-600
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Journal article (peer-reviewed)abstract
- We re-examined the effects of acidification on Scandinavian freshwater lakes using paleolimnological reconstructions focused on subfossil chironomids. Our study showed a widespread shift in chironomid community composition occurring at around 1960 and corresponding with the maximum fallout of anthropogenic SO42- deposition. Results also showed that taxonomic turn-over was higher in chironomid records from nitrogen-limited lakes, likely due to the cumulative effects of acidification and eutrophication driven by atmospheric nitrogen deposition. Despite strong evidence of chemical recovery from acidification, all lake records failed to show a return to pre-acidified community compositions and most chironomid communities instead continue to follow the trajectories triggered by acidification. We hypothesized that when SO42- deposition started to decrease after 1980, a period also marked by rapid environmental and climatic changes, the influence of pH and/or other acidification-related variables in structuring chironomid community became less important, thus, giving more relative importance to other drivers, such as brownification and climatic processes. Results, therefore, suggest the key role of acidification in shaping the response of chironomid communities to future environmental changes. Future paleolimnological studies will contribute to better manage aquatic ecosystems recovering from acidification worldwide by allowing managers to quantify the efficacy of different management actions taken to mitigate acidification as well as to redefine appropriate restoration targets.
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| 6. |
- Troubitsyna, Elena
(author)
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Employing Redundancy to Leverage Cybersecurity Protection of Safety-Critical Systems
- 2023
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In: Proceedings - 2023 10th International Conference on Dependable Systems and Their Applications, DSA 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 282-287
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Conference paper (peer-reviewed)abstract
- Safety-critical systems become increasingly open and interconnected, which makes them a target of various cyberattacks. Such cyberattacks might jeopardise system safety and availability. Many safety-critical systems, such as railways, have a very long life cycle and hence, a large number of legacy components. The implementation of modern security protection mechanisms is often restricted due to the rigidness of legacy architecture and high re-certification costs. Therefore, it is desirable to efficiently utilise the potential already present in the system and enhance cybersecurity protection without major modifications. Safety-critical systems usually contain a high degree of redundancy required to achieve fault tolerance. In this paper, we investigate how to utilise redundancy to enhance cybersecurity protection. We demonstrate that by introducing diversity in the redundant architectures and implementing security monitoring, we can potentially enhance cybersecutiry protection of safety-critical systems.
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| 7. |
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| 8. |
- Mahama, Ruhia, 1985, et al.
(author)
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African immigrants in Sweden experiencing the threat of forced child removal
- 2024
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In: European Journal of Social Work. - : Informa UK Limited. - 1369-1457 .- 1468-2664. ; 27:2
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Journal article (peer-reviewed)abstract
- This study investigated the experiences of African parents living in Sweden around the concept of forced child removal. The study aimed at finding out their experiences and attitudes around the concept and how the threat of it affects their parenting styles and coping strategies in Sweden. Nine semi-structured qualitative interviews were made with participants of African origin living in Sweden. Data was analysed using a reflexive thematic analysis. An important contribution of the study to parenting amongst African immigrants in Sweden is knowledge gained of the shift from an authoritarian style of parenting towards an authoritative one. It is about going from punishing the children if they make mistakes in life to reasoning with them more about what is right to do in life. This knowledge is helpful for social workers working with this segment of the population because an authoritative style of parenting takes into consideration the autonomy of the child and, therefore, closer to the Swedish styles of parenting, than authoritarian styles, which can make interventions with such parents easier. Social workers, however, need to get closer to their clients to understand the motivations of this shift from individual clients as this might differ.
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| 13. |
- Bala, Sidona Valentina, et al.
(author)
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Measuring person-centred care in nurse-led outpatient rheumatology clinics
- 2018
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In: Musculoskeletal Care. - : John Wiley & Sons. - 1478-2189 .- 1557-0681. ; 16:2, s. 296-304
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Journal article (peer-reviewed)abstract
- Background: Measurement of person-centred care (PCC) outcomes is underdeveloped owing to the complexity of the concept and lack of conceptual clarity. A framework conceptualizing outpatient PCC in rheumatology nurse-led clinics has therefore been suggested and operationalized into the PCC instrument for outpatient care in rheumatology (PCCoc/rheum).Objective: The aim of the present study was to test the extent to which the PCCoc/rheum represents the underpinning conceptual outpatient PCC framework, and to assess its measurement properties as applied in nurse-led outpatient rheumatology clinics.Methods: The 24-item PCCoc/rheum was administered to 343 persons with rheumatoid arthritis from six nurse-led outpatient rheumatology clinics. Its measurement properties were tested by Rasch measurement theory.Results: Ninety-two per cent of individuals (n = 316) answered the PCCoc/rheum. Items successfully operationalized a quantitative continuum from lower to higher degrees of perceived PCC. Model fit was generally good, including lack of differential item functioning (DIF), and the PCCoc/rheum was able to separate individuals with a reliability of 0.88. The four response categories worked as intended, with the exception of one item. Item ordering provided general empirical support of a priori expectations, with the exception of three items that were omitted owing to multidimensionality, dysfunctional response categories and unexpected ordering. The 21-item PCCoc/rheum showed good accordance with the conceptual framework, improved fit, functioning response categories and no DIF, and its reliability was 0.86.Conclusion: We found general support for the appropriateness of the PCCoc/rheum as an outcome measure of patient-perceived PCC in nurse-led outpatient rheumatology clinics. While in need of further testing, the 21-item PCCoc/rheum has the potential to evaluate outpatient PCC from a patient perspective.
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| 14. |
- Bala, Sidona-Valentina
(author)
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Person-centered care in nurse-led outpatient rheumatology clinics. From experience to measurement.
- 2017
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Doctoral thesis (other academic/artistic)abstract
- AbstractAim: To describe and understand patients’ experiences as a means to conceptualize and evaluate outpatient person-centered care (PCC) in nurse-led rheumatoid arthritis (RA) clinics.Methods: Persons with RA were interviewed about how they experienced their nurse-led outpatient care and about the meaning of living with persistent RA. Interviews were analyzed by qualitative content analysis and hermeneuticphenomenology. Based on these results, existing PCC frameworks and hypothetical logical reasoning, a conceptual framework for nurse-led outpatient PCC was developed and used to operationalize a PCC instrument for outpatientcare in rheumatology (PCCoc/rheum). Acceptability and content validity of the PCCoc/rheum were evaluated, and its measurement properties were tested according to Rasch measurement theory (RMT).Results: The experience of nurse-led outpatient care was expressed as social environment, professional approach and value-adding measures, all relating to the degree of PCC. Living with persistent RA was revealed as an existence dominated by painful symptoms and treatment, radical changes and limitations in life, a continual struggle to cope with life and to master the illness, and a dependency on those who are close by and the world around. Results also pointed to the need for a stronger PCC approach. An outpatient framework was conceptualized with five related domains, and was used to develop the PCCoc/rheum, which showed good acceptability and contentvalidity. RMT supported the accordance between the PCCoc/rheum and the conceptual framework, and its measurement properties were generally supported.Conclusions: Experiences of persons with RA support a central role for PCC. The conceptual framework and the PCCoc/rheum have potentials to improve implementation and evaluation of outpatient PCC and contribute to qualityof care from a PCC perspective in nurse-led rheumatoid arthritis clinics.
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