| 1. |
- Andersson, Tobias, 1976, et al.
(författare)
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Country of birth and mortality risk in hypertension with and without diabetes: the Swedish primary care cardiovascular database.
- 2021
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Ingår i: Journal of hypertension. - 1473-5598. ; 39:6, s. 1155-1162
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Tidskriftsartikel (refereegranskat)abstract
- Hypertension and diabetes are common and are both associated with high cardiovascular morbidity and mortality. We aimed to investigate associations between mortality risk and country of birth among hypertensive individuals in primary care with and without concomitant diabetes, which has not been studied previously. In addition, we aimed to study the corresponding risks of myocardial infarction and ischemic stroke.This observational cohort study of 62557 individuals with hypertension diagnosed 2001-2008 in the Swedish Primary Care Cardiovascular Database assessed mortality by the Swedish Cause of Death Register, and myocardial infarction and ischemic stroke by the National Patient Register. Cox regression models were used to estimate study outcome hazard ratios by country of birth and time updated diabetes status, with adjustments for multiple confounders.During follow-up time without diabetes using Swedish-born as reference, adjusted mortality hazard ratios per country of birth category were Finland: 1.26 (95% confidence interval 1.15-1.38), high-income European countries: 0.84 (0.74-0.95), low-income European countries: 0.84 (0.71-1.00) and non-European countries: 0.65 (0.56-0.76). The corresponding adjusted mortality hazard ratios during follow-up time with diabetes were high-income European countries: 0.78 (0.63-0.98), low-income European countries: 0.74 (0.57-0.96) and non-European countries: 0.56 (0.44-0.71). During follow-up without diabetes, the corresponding adjusted hazard ratio of myocardial infarction was increased for Finland: 1.16 (1.01-1.34), whereas the results for ischemic stroke were inconclusive.In Sweden, hypertensive immigrants (with the exception for Finnish-born) with and without diabetes have a mortality advantage, as compared to Swedish-born.
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| 2. |
- Andersson, Tobias, 1976, et al.
(författare)
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Mortality trends and cause of death in patients with new-onset type 2 diabetes and controls: A 24-year follow-up prospective cohort study.
- 2018
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Ingår i: Diabetes research and clinical practice. - : Elsevier BV. - 1872-8227 .- 0168-8227. ; 138, s. 81-89
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Tidskriftsartikel (refereegranskat)abstract
- Our aim was to assess causes of death and temporal changes in excess mortality among patients with new-onset type 2 diabetes in Skaraborg, Sweden.Patients from the Skaraborg Diabetes Register with prospectively registered new-onset type 2 diabetes 1991-2004 were included. Five individual controls matched for sex, age, geographical area and calendar year of study entry were selected using population records. Causes of deaths until 31 December 2014 were retrieved from the Cause of Death Register. Adjusted excess mortality among patients and temporal changes of excess mortality were calculated using Poisson models. Cumulative incidences of cause-specific mortality were calculated by competing risk regression.During 24years of follow-up 4364 deaths occurred among 7461 patients in 90,529 person-years (48.2/1000 person-years, 95% CI 46.8-49.7), and 18,541 deaths in 479,428 person-years among 37,271 controls (38.7/1000 person-years, 38.1-39.2). The overall adjusted mortality hazard ratio was 1.47 (p<.0001) among patients diagnosed at study start 1991 and decreased by 2% (p<.0001) per increase in calendar year of diagnosis until 2004. Excess mortality was mainly attributed to endocrine and cardiovascular cause of death with crude subdistributional hazard ratios of 5.06 (p<.001) and 1.22 (p<.001).Excess mortality for patients with new-onset type 2 diabetes was mainly attributed to deaths related to diabetes and the cardiovascular system, and decreased with increasing year of diagnosis 1991-2004. Possible explanations could be temporal trends of earlier diagnosis due to lowered diagnostic thresholds and intensified diagnostic activities, as well as improved treatment.
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| 3. |
- Andersson, Tobias, 1976, et al.
(författare)
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The impact of diabetes, education and income on mortality and cardiovascular events in hypertensive patients: A cohort study from the Swedish Primary Care Cardiovascular Database (SPCCD).
- 2020
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 15:8
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Tidskriftsartikel (refereegranskat)abstract
- In this study we aimed to estimate the effect of diabetes, educational level and income on the risk of mortality and cardiovascular events in primary care patients with hypertension.We followed 62,557 individuals with hypertension diagnosed 2001-2008, in the Swedish Primary Care Cardiovascular Database. Study outcomes were death, myocardial infarction, and ischemic stroke, assessed using national registers until 2012. Cox regression models were used to estimate adjusted hazard ratios of outcomes according to diabetes status, educational level, and income.During follow-up, 13,231 individuals died, 9981 were diagnosed with diabetes, 4431 with myocardial infarction, and 4433 with ischemic stroke. Hazard ratios (95% confidence intervals) for diabetes versus no diabetes: mortality 1.57 (1.50-1.65), myocardial infarction 1.24 (1.14-1.34), and ischemic stroke 1.17 (1.07-1.27). Hazard ratios for diabetes and ≤9 years of school versus no diabetes and >12 years of school: mortality 1.56 (1.41-1.73), myocardial infarction 1.36 (1.17-1.59), and ischemic stroke 1.27 (1.08-1.50). Hazard ratios for diabetes and income in the lowest fifth group versus no diabetes and income in the highest fifth group: mortality 3.82 (3.36-4.34), myocardial infarction 2.00 (1.66-2.42), and ischemic stroke 1.91 (1.58-2.31).Diabetes combined with low income was associated with substantial excess risk of mortality, myocardial infarction and ischemic stroke among primary care patients with hypertension.
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| 4. |
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| 5. |
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| 6. |
- Boström, Per Staffan
(författare)
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Resurstillväxt via innovationskapital
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Under senaste decennierna har en allt större andel av företags resurser utgjorts av s k osynliga tillgångar, immateriella tillgångar, såsom ägarandelar i utvecklingsbolag, investering i avknoppningsbolag och utveckling av idéer i inkubatorer, samtidigt som de resurser som finns under ett företags juridiska kontroll i bland annat samarbetsprojekt inom FoU, relativt sett också har minskat. Resurstillväxt är en central fråga i de organisationer som studeras i denna avhandling men ofta finns en `obalans´ i relationen mellan identifierade materiella/immateriella resurser och oidentifierade immateriella resurser. Med denna utgångspunkt studeras i avhandlingen dessa förändringar och hur det påverkar företags möjlighet att strategiskt agera kring utveckling av företagets innovationskapital och hur den ekonomiska styrningen då påverkas. Resultatet av den sammanlagda, systemiska analysen av samtliga `case´ i avhandlingen indikerar att den interna resurstillväxt som genereras och redovisas i olika former, drivs av förhållanden orsakade av externa förändringar men har också möjliggjorts av ledningens strategiska prioriteringar avseende företagets resursbas. Även om litteraturen argumenterar i överensstämmelse med vad analysen visar, indikerar fallen på behovet av utvecklade riktlinjer för hur innovations- och affärsledning vid verksamhet på en konkurrensutsatt utvecklingsmarknad kan förnya och modifiera ett företags resursbas. För att komma till rätta med detta pekar avhandlingen på behovet av att väga möjligheter och risker i strategiska beslut, att tillämpa ett multidisciplinärt synsätt och att använda finansiella och tekniska verktyg som är anpassade till de många frågeställningar om hur man kan stärka företagets innovationskapital.Forskningen tyder på att företag bör fokusera på resurser och förmågor som, i en förväntad och kommunicerad situation har potential att effektivisera företagets långsiktiga konkurrenspositionering, och samtidigt utveckla organisatoriska processer för att hantera kort- och långsiktiga utmaningar och osäkerheter. Baserat på avhandlingens empiri utvecklas modeller för att stödja ledningens hantering av resursbasen, modeller som kan bidra till både kortsiktiga och långsiktiga förändringar av företagens innovationskapital. Avhandlingen identifierar ett antal resursbaserade företagsspecifika strategier som företag kan välja för sina materiella och immateriella resurser. Strategierna stödjer företagsspecifika mål avseende innovationssamarbeten och, med hänsyn till företagets tidsaspekt, en långsiktigt hållbar konkurrensförmåga och konkurrensfördel.
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| 7. |
- Liss, Per, et al.
(författare)
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Renal effects of CO2 and iodinated contrast media in patients undergoing renovascular intervention : a prospective, randomized study
- 2005
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Ingår i: Journal of Vascular and Interventional Radiology. - 1051-0443 .- 1535-7732. ; 16:1, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: CO2 gas has been proposed for use instead of iodinated contrast media in angiographic examinations in patients at risk of developing renal failure from contrast media. The influence of intraarterial injection of CO2 with small added amounts of ioxaglate (200 mgI/mL) or ioxaglate alone on renal function in patients with suspected renal artery stenosis was studied in a prospective, randomized study. MATERIALS AND METHODS: One hundred twenty-three patients underwent renovascular intervention (n = 83) and/or renal angiography (n = 40) for suspected renal artery stenosis. Patients with a serum creatinine concentration less than 200 micromol/L (n = 82) were randomized prospectively to receive CO2 with small added amounts of ioxaglate (n = 37) or only ioxaglate (n = 45). Patients with serum creatinine levels greater than 200 micromol/L (n = 41) were not randomized and initially received CO2. Serum creatinine concentrations were measured within 1 day before and 1 day, 2 days, and 2-3 weeks after the procedure. RESULTS: The amount of injected CO2 did not relate to an increase in serum creatinine level. In the randomized groups, and also when the whole patient sample was considered, the amount of injected iodine was significantly correlated (P = .011) with an increase in serum creatinine level and a decrease in estimated creatinine clearance after 2 days. Among the randomized patients, one in the CO2 group and three in the ioxaglate group had a more than 25% increase in serum creatinine level within the first 2 days after the intervention. CONCLUSION: The risk of impairment of renal function is lower after injection of CO2 with small amounts of added ioxaglate compared with injection of a larger amount of ioxaglate alone. The larger the amount of administered iodinated contrast medium, the greater the risk of development of renal failure.
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| 8. |
- Alalam, Hanna, et al.
(författare)
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A High-Throughput Method for Screening for Genes Controlling Bacterial Conjugation of Antibiotic Resistance.
- 2020
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Ingår i: mSystems. - 2379-5077. ; 5:6
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Tidskriftsartikel (refereegranskat)abstract
- The rapid horizontal transmission of antibiotic resistance genes on conjugative plasmids between bacterial host cells is a major cause of the accelerating antibiotic resistance crisis. There are currently no experimental platforms for fast and cost-efficient screening of genetic effects on antibiotic resistance transmission by conjugation, which prevents understanding and targeting conjugation. We introduce a novel experimental framework to screen for conjugation-based horizontal transmission of antibiotic resistance between >60,000 pairs of cell populations in parallel. Plasmid-carrying donor strains are constructed in high-throughput. We then mix the resistance plasmid-carrying donors with recipients in a design where only transconjugants can reproduce, measure growth in dense intervals, and extract transmission times as the growth lag. As proof-of-principle, we exhaustively explore chromosomal genes controlling F-plasmid donation within Escherichia coli populations, by screening the Keio deletion collection in high replication. We recover all seven known chromosomal gene mutants affecting conjugation as donors and identify many novel mutants, all of which diminish antibiotic resistance transmission. We validate nine of the novel genes' effects in liquid mating assays and complement one of the novel genes' effect on conjugation (rseA). The new framework holds great potential for exhaustive disclosing of candidate targets for helper drugs that delay resistance development in patients and societies and improve the longevity of current and future antibiotics. Further, the platform can easily be adapted to explore interspecies conjugation, plasmid-borne factors, and experimental evolution and be used for rapid construction of strains.IMPORTANCE The rapid transmission of antibiotic resistance genes on conjugative plasmids between bacterial host cells is a major cause of the accelerating antibiotic resistance crisis. There are currently no experimental platforms for fast and cost-efficient screening of genetic effects on antibiotic resistance transmission by conjugation, which prevents understanding and targeting conjugation. We introduce a novel experimental framework to screen for conjugation-based horizontal transmission of antibiotic resistance between >60,000 pairs of cell populations in parallel. As proof-of-principle, we exhaustively explore chromosomal genes controlling F-plasmid donation within E. coli populations. We recover all previously known and many novel chromosomal gene mutants that affect conjugation efficiency. The new framework holds great potential for rapid screening of compounds that decrease transmission. Further, the platform can easily be adapted to explore interspecies conjugation, plasmid-borne factors, and experimental evolution and be used for rapid construction of strains.
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| 9. |
- Alopaeus, Tea, et al.
(författare)
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Med de nya svenska klimatmålen i sikte : Gapanalys samt strategier och förutsättningar för att nå etappmålen 2030 med utblick mot 2045
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Under våren 2017 presenterade Naturvårdsverket scenarier för hur växthusgasutsläppen i Sverige skulle kunna utvecklas till 2035. Sedan Naturvårdsverket presenterade scenarierna har ett nytt klimatpolitiskt ramverk för Sverige beslutats av riksdagen med nya klimatmål till 2030, 2040 och 2045. Regeringen har även presenterat ett antal nya styrmedel i budgetpropositionen.Naturvårdsverket ska inom miljömålssystemet löpande och strategiskt analysera och utvärdera styrmedel och åtgärder. Naturvårdsverket har mellan maj och november 2017 gjort en första uppföljning mot de nya klimatmålen. I denna rapport presenteras hur beslutade och planerade styrmedel kan komma att falla ut givet olika antagande. En översiktlig analys av styrmedel görs också.Arbetsgruppens sammansättning har varierat över tid. Sammantaget har följande personer på Naturvårdsverket deltagit i arbetsgruppen: Tea Alopaeus (projektledare), Björn Boström, Mats Björsell, Martin Boije, Joanna Dickinson, Dag Henning, Daniel Engström Stenson, Eva Jernbäcker (projektledare till september), Julien Morel, Miriam Münnich Vass, Karl-Anders Stigzelius, Ulrika Svensson, Per Wollin.Stockholm 29 november 2017Björn RisingerGeneraldirektör
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| 10. |
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| 11. |
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Andersson, Tobias, 1976, et al.
(författare)
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The effect of statins on mortality and cardiovascular disease in primary care hypertensive patients without other cardiovascular disease or diabetes.
- 2023
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Ingår i: European journal of preventive cardiology. - 2047-4881. ; 30:17, s. 1883-1894
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Tidskriftsartikel (refereegranskat)abstract
- Studies in primary health care (PHC) assessing the effect of primary prevention with statins on mortality and cardiovascular disease (CVD) are scarce. This study aimed to estimate the effect of statins on all-cause mortality, cardiovascular mortality, myocardial infarction (MI) and stroke in individuals in PHC with hypertension without CVD or diabetes.Using the Swedish PHC quality assurance register QregPV, the study included 13 193 individuals with hypertension without CVD or diabetes, who had filled a first statin prescription between 2010 and 2016, and 13 193 matched controls without a filled statin prescription at index date. Controls were matched on sex and propensity score using clinical data and data from national registers on co-morbidities, prescriptions, and socioeconomic status. The effect of statins was estimated in Cox regression models.During a median of 4.2 years of follow-up, 395 individuals in the statin group versus 475 in the control group died, 197 versus 232 died of cardiovascular disease, 171 versus 191 had a MI, and 161 versus 181 had a stroke. The treatment effect of statins was significant for all-cause mortality (HR 0.83, 95% confidence interval [CI] 0.74-0.93) and cardiovascular mortality (HR 0.85, 95% CI 0.72-0.998). Overall, no significant treatment effect of statins was seen for MI (HR 0.89, 95% CI 0.74-1.07), but there was a significant interaction with sex (p=0.008) with decreased risk of MI for women but not for men (HR 0.66, 95% CI 0.49-0.88 versus HR 1.09, 95% CI 0.86-1.38).Primary prevention with statins in PHC was associated with reduced risk of all-cause mortality, cardiovascular mortality, and in women, lower risk of MI.
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| 16. |
- Baden, Susanne P., 1952, et al.
(författare)
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Relative importance of trophic interactions and nutrient enrichment in seagrass ecosystems: A broad-scale field experiment in the Baltic-Skagerrak area.
- 2010
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Ingår i: Limnology and Oceanography. - 1541-5856. ; 55:3, s. 1435-1448
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of eutrophication and predation in structuring seagrass Zostera marina L. ecosystems was assessed in a field experiment in three regions along an estuarine salinity gradient, from southern Finland to the Skagerrak area of the Swedish west coast. All regions are considered to be affected by eutrophication and overfishing but differ in the abundance of intermediate predators (e.g., small fish, shrimp, and crabs), mesograzers, and the biomass of epiphytic algae. Using transplanted Zostera (eelgrass), nutrient levels and intermediate predator abundance were manipulated in a full-factorial cage experiment. On the Swedish west coast, where ambient densities of mesograzers are very low, epiphytic algae responded strongly to nutrient enrichment, resulting in significantly reduced growth of eelgrass. At the Baltic sites however, where ambient densities of mesograzers are high, no significant growth of epiphytic algae was detected, and only grazer biomass responded to nutrient enrichment. Predation from small fish, shrimp, and crabs decreased the biomass of mesograzers by . 98% on the Swedish west coast, but natural predators had no significant effect on mesograzers biomass at the Baltic sites. Predation and nutrient enrichment interacted to affect the growth of eelgrass by controlling the biomass of mesograzers and nuisance algae. The differing effect of nutrient enrichment and grazing in the three regions may therefore be a result of the prevailing low and high predation pressure on mesograzers in Zostera. This absence or presence of predation may derive from interregional changes in trophic interactions, possibly caused by a combination of eutrophication and overfishing.
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| 17. |
- Bager, Johan-Emil, et al.
(författare)
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Blood pressure levels and risk of haemorrhagic stroke in patients with atrial fibrillation and oral anticoagulants: results from The Swedish Primary Care Cardiovascular Database of Skaraborg.
- 2021
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Ingår i: Journal of hypertension. - 1473-5598. ; 39:8, s. 1670-1677
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Tidskriftsartikel (refereegranskat)abstract
- To assess the risk of haemorrhagic stroke at different baseline SBP levels in a primary care population with hypertension, atrial fibrillation and newly initiated oral anticoagulants (OACs).We identified 3972 patients with hypertension, atrial fibrillation and newly initiated OAC in The Swedish Primary Care Cardiovascular Database of Skaraborg. Patients were followed from 1 January 2006 until a first event of haemorrhagic stroke, death, cessation of OAC or 31 December 2016. We analysed the association between continuous SBP and haemorrhagic stroke with a multivariable Cox regression model and plotted the hazard ratio as a function of SBP with a restricted cubic spline with 130mmHg as reference.There were 40 cases of haemorrhagic stroke during follow-up. Baseline SBP in the 145-180mmHg range was associated with a more than doubled risk of haemorrhagic stroke, compared with a SBP of 130mmHg.In this cohort of primary care patients with hypertension and atrial fibrillation, we found that baseline SBP in the 145-180mmHg range, prior to initiation of OAC, was associated with a more than doubled risk of haemorrhagic stroke, as compared with an SBP of 130mmHg. This suggests that lowering SBP to below 145mmHg, prior to initiation of OAC, may decrease the risk of haemorrhagic stroke in patients with hypertension and atrial fibrillation.
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| 18. |
- Bager, Johan-Emil, et al.
(författare)
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Hypertension: sex-related differences in drug treatment, prevalence and blood pressure control in primary care.
- 2023
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Ingår i: Journal of human hypertension. - : Springer Science and Business Media LLC. - 1476-5527. ; 37, s. 662-670
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Forskningsöversikt (refereegranskat)abstract
- Antihypertensive treatment is equally beneficial for reducing cardiovascular risk in both men and women. Despite this, the drug treatment, prevalence and control of hypertension differ between men and women. Men and women respond differently, particularly with respect to the risk of adverse events, to many antihypertensive drugs. Certain antihypertensive drugs may also be especially beneficial in the setting of certain comorbidities - of both cardiovascular and extracardiac nature - which also differ between men and women. Furthermore, hypertension in pregnancy can pose a considerable therapeutic challenge for women and their physicians in primary care. In addition, data from population-based studies and from real-world data are inconsistent regarding whether men or women attain hypertension-related goals to a higher degree. In population-based studies, women with hypertension have higher rates of treatment and controlled blood pressure than men, whereas real-world, primary-care data instead show better blood pressure control in men. Men and women are also treated with different antihypertensive drugs: women use more thiazide diuretics and men use more angiotensin-enzyme inhibitors and calcium-channel blockers. This narrative review explores these sex-related differences with guidance from current literature. It also features original data from a large, Swedish primary-care register, which showed that blood pressure control was better in women than men until they reached their late sixties, after which the situation was reversed. This age-related decrease in blood pressure control in women was not, however, accompanied by a proportional increase in use of antihypertensive drugs and female sex was a significant predictor of less intensive antihypertensive treatment.
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| 19. |
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| 20. |
- Bentzel, Sara, et al.
(författare)
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Long-term secondary prevention and outcome following acute coronary syndrome: Real-world results from the Swedish Primary Care Cardiovascular Database (SPCCD)
- 2024
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Ingår i: European journal of preventive cardiology. - 2047-4881. ; 31:7, s. 812-821
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Tidskriftsartikel (refereegranskat)abstract
- Most studies of treatment adherence after acute coronary syndrome (ACS) are based on prescribed drugs and lack long-term follow-up or consecutive data on risk factor control. We studied the long-term treatment adherence, risk factor control and its association to recurrent ACS and death.We retrospectively included 3765 patients (mean age 75 years, 40% women) with incident ACS from 1 January 2006 until 31 December 2010 from the SPCCD-SKA database. All patients were followed until 31 December 2014 or death. We recorded blood pressure (BP), low density lipoprotein-cholesterol (LDL-C), recurrent ACS and death. We used data on dispensed drugs to calculate proportion of days covered for secondary prevention medications. Cox regressions were used to analyse the association of achieved BP and LDL-C to recurrent ACS and death.The median follow-up time was 4.8 years. Proportion of patients that reached BP <140/90mmHg was 58% year 1 and 66% year 8. 65% of the patients reached LDL-C<2.5mmol/L at year 1 and 56% at year 8, however adherence to statins varied from 43% to 60%. Only 62% of the patients had yearly measured BP, and only 28% yearly measured LDL-C. SBP was not associated with a higher risk of recurrent ACS or death. LDL-C of 3.0mmol/L were associated with a higher risk of recurrent ACS [HR 1.19 (95% CI 1.00-1.40)] and death HR 1.26 [(95% CI 1.08-1.47)] compared to an LDL-C 1.8mmol/L.This observational long-term real-world study demonstrates low drug adherence and potential for improvement of risk factors after ACS. Furthermore, the study confirms that uncontrolled LDL-C is associated with adverse outcome even in this older population.
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| 21. |
- Bokrantz, Tove, et al.
(författare)
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Antihypertensive drug classes and the risk of hip fracture: results from the Swedish primary care cardiovascular database.
- 2020
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Ingår i: Journal of hypertension. - 1473-5598. ; 38:1, s. 167-175
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Tidskriftsartikel (refereegranskat)abstract
- Hypertension and fractures related to osteoporosis are major public health problems that often coexist. This study examined the associations between exposure to different antihypertensive drug classes and the risk of hip fracture in hypertensive patients.We included 59246 individuals, 50 years and older, diagnosed with hypertension during 2001-2008 in the Swedish Primary Care Cardiovascular Database. Patients were followed from 1 January 2006 (or the date of diagnosis of hypertension) until they had their first hip fracture, died, or reached the end of the study on 31 December 2012. Cox proportional hazards models were used to calculate the risk of hip fracture across types of antihypertensive medications, adjusted for age, sex, comorbidity, medications, and socioeconomic factors.In total, 2593 hip fractures occurred. Compared to nonusers, current use of bendroflumethiazide or hydrochlorothiazide was associated with a reduced risk of hip fracture (hazard ratio 0.86; 95% CI 0.75-0.98 and hazard ratio 0.84; 95% CI 0.74-0.96, respectively), as was use of fixed drug combinations containing a thiazide (hazard ratio 0.69; 95% CI 0.57-0.83). Current use of loop diuretics was associated with an increased risk of hip fracture (hazard ratio 1.23; 95% CI 1.11-1.35). No significant associations were found between the risk of hip fracture and current exposure to beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, aldosterone-receptor blockers or calcium channel blockers.In this large observational study of hypertensive patients, the risk of hip fracture differed across users of different antihypertensive drugs, results that could have practical implications when choosing antihypertensive drug therapy.
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| 25. |
- Boström, Agneta, 1948-
(författare)
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Sharing lived experience : How upper secondary school chemistry teachers and students use narratives to make chemistry more meaningful
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation concerns the place of teachers’ and students’ narratives in making school chemistry more meaningful to students. The material was collected at upper secondary school courses and consists of interviews with six experienced chemistry teachers, five adult students attending evening classes and six younger students. The methodological and theoretical approach is mainly inspired by John Dewey’s (1925, 1938) notion of continuity and by narrative inquiry as formulated by Clandinin & Connelly (2000). In defining narratives as a way of knowing, Bruner’s (1996, 2002) distinction between paradigmatic and narrative cognition is used, as well as his ideas about the past, the present and the possible.The findings show how teachers use narratives from their own lived experience as well as from other people’s lives in order to make chemistry more meaningful. Moreover, they use a narrative format to make their scientific explanations meaningful. Students use narratives or stories connected to their own lived experience to make sense of chemistry. These results show how chemistry can be made part of a meaningful context through sharing lived experience by means of storytelling. Narratives are used to make everyday life and chemistry class experiences continuous in the sense suggested by Dewey (1938). In accordance with his thoughts on experience, narratives are of help in the science classroom not only in making science more relevant and interesting, but also easier to understand. In the dissertation numerous examples of such stories are given and their role in learning chemistry is discussed.The stories of the teachers and students in the study are retold and analysed according to additional analytic tools in order to further document their role in teaching chemistry. It is argued that the collected narratives constitute an ingredient in teachers’ pedagogical content knowledge, PCK, according to Shulman (1986). How they can be used in different content areas of science and chemistry is discussed. The content of the narratives is also related to the Swedish curriculum, to the findings of the ROSE project and to Roberts’s (1982) knowledge emphases. The content analyses show that narratives make chemistry in class pluralistic in allowing the lived experiences of teachers and students to interact with the scientific facts.The final discussion concerning narrative inquiry is inspired by what Clandinin & Connelly (2000) wrote about “clashes at the boundaries”. The specific boundary in this dissertation is situated between canonical science teaching methods on the one hand and the use of narratives in teaching and narrative inquiry as research method on the other hand. Reductionism alone cannot explain nature and the complexity of life (Dewey 1925, 1938 and Midgley 2004), and the results of this dissertation show that narratives are used by both students and teachers in order to make sense of chemistry. Narratives constitute a way to make the reductionist knowing of science part of a more meaningful whole in accordance with Dewey’s holistic ideas about education.The results of this study suggest that teaching narratives can – and should – be used in science as a complement to other, more scientifically oriented educational methods. Thus, it supports many of the efforts made within context-based approaches, such as Case Studies, LCP (Large Context Problems), PBL (Problem-Based Learning), the Salter’s method and the Storyline method. Further implications of the results for teaching, learning, teacher education and research are explored.
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| 26. |
- Boström, Curt-Åke, et al.
(författare)
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Regionala spridningsbilder av kväveoxider, ozon och kolväten
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Miljövårdsenheten vid Länsstyrelsen i Stockholms län har i samarbete med IVL genomfört ett projekt där diffusionsprovtagare, s k passiva mottagare, använts för att mäta och beskriva haltförhållanden i luft över hela länet och i olika miljöer. Naturvårdsverket har finansierat projektet med medel för specialprojekt, och därtill har Vägverket, Region Stockholm bidragit med medel. Syftet med projektet har främst varit att testa om diffusionsprovtagare är lämpliga hjälpmedel för att kartera halter av luftföroreningar över stora ytor som har en komplex blandning av emissionskällor. Samtidigt har en test av provtagarnas mätsäkerhet och mätnogrannhet skett. Om mätningarna lyckades skulle detta ge ett dataunderlag som möjliggjorde jämförelser mellan mätpunkter i hela länet...
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| 27. |
- Boström, Gustaf, et al.
(författare)
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Antidepressant use and mortality in very old people
- 2016
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Ingår i: International psychogeriatrics. - : Cambridge University Press. - 1041-6102 .- 1741-203X. ; 28:7, s. 1201-1210
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Antidepressant treatment may increase the risk of death. The association between antidepressants and mortality has been evaluated in community-dwelling older people, but not in representative samples of very old people, among whom dementia, multimorbidity, and disability are common.METHODS: Umeå 85+/GERDA study participants (n = 992) aged 85, 90, and ≥95 years were followed for up to five years. Cox proportional hazard regression models were used to analyze mortality risk associated with baseline antidepressant treatment, adjusted for potential confounders.RESULTS: Mean age was 89 years; 27% of participants had dementia, 20% had stroke histories, 29% had heart failure, and 16% used antidepressants. In age- and sex-adjusted analyses, antidepressant use was associated with a 76% increased mortality risk (hazard ratio [HR] = 1.76; 95% confidence interval [CI], 1.41-2.19). Adding adjustment for Geriatric Depression Scale score, HR was 1.62 (95% CI, 1.29-2.03). The association was not significant when adjusting for additional confounding factors (HR = 1.08; 95% CI, 0.85-1.38). Interaction analyses in the fully adjusted model revealed a significant interaction between sex and antidepressant use (HR: 1.76; 95% CI, 1.05-2.94). Among male and female antidepressant users, the HRs for death were 0.76 (95% CI, 0.47-1.24) and 1.28 (95% CI, 0.97-1.70), respectively.CONCLUSION: Among very old people, baseline antidepressant treatment does not seem to be independently associated with increased mortality risk. However, the risk may be different in men and women. This difference and the potential risk of initial treatment require further investigation in future cohort studies of very old people.
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| 28. |
- Boström, Johan, 1978-
(författare)
-
Att möjliggöra tekniklärande i konstruktionsaktiviteter : En aktionsforskningsstudie i förskolan
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation examines how technology learning is made possible through teacher-led construction activities in preschool. The dissertation also examines how the preschool teachers’ role and the design of the construction activities were affected by different historical and societal structures as well as the collaboration between research and practice.The dissertation is based on an action research study that was carried out with a group of preschool teachers in two preschool units. In order to develop the preschool practice, the group carried out three different construction activities that were videotaped and analyzed.The results of the dissertation indicate that the preschool teachers used a number of different technology didactic tools to support the children in their technology learning. At the same time, the results show that some children were given much more input in the problem-solving process that took place during the activities, while other children did not have that much of an opportunity for such influence. Both the children's ability to come up with suggestions for solutions and the preschool teachers' confirmation of the children played an important role in this process. The results also indicate that the preschool teachers' assumptions about technology, about the children, about the preschool and about their own role in the activities influenced their actions. The study shows that the design of the activities may be influenced by the history of construction activities in preschool, as well as the gender coding of the technology.In summary, this study indicates that taking on the role of the active and guiding adult in a construction activity is just the first step in creating activities that are as inclusive as possible. The preschool teacher also needs to reflect on how the staging of these activities facilitates or limits children's different actions. It is also important to understand how different choices (e.g., activities, tools, materials) affect the activities that are staged.The dissertation also shows that there may be tension between the researcher and the participants in an action research project in preschool. There may be power structures between researchers and participants that are not entirely easy to handle.
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| 29. |
- Boström, Johan, et al.
(författare)
-
Rethinking construction in preschool : discerning didactic strategies in Swedish preschool activities
- 2022
-
Ingår i: International journal of technology and design education. - : Springer. - 0957-7572 .- 1573-1804. ; 32, s. 2039-2061
-
Tidskriftsartikel (refereegranskat)abstract
- Even though construction tasks have a long history as an activity in the Swedish preschool, technology as a content matter (e.g., construction) is relatively new. Hence, preschool teachers are generally unsure of the content of technology and how to handle it from a teaching perspective. Thus, there is need for deeper understanding of how construction tasks in preschool can be enacted and what kind of premises are offered to the children. To investigate this, we took our stance in activity theory and the concepts of mediating artifacts, rules and division of labour. This helped us discern what type of instructional practices that were enacted by preschool teachers when working with construction tasks. Activity theory in combination with thematic analysis helped us distinguish four general didactic actions that the teachers used to bring about the construction task-to engage, to guide, to coordinate, to show. These four strategies were then formulated into specific technology didactic actions through the perspectives of technology as product, process and concepts.
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| 30. |
- Boström, Johan, 1978-
(författare)
-
Teknik i förskolan – att motverka traditionella könsroller : En aktionsforskningsstudie
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study shows that developing a gender sensitive technology education in apreschool setting is a very complex and multifaceted task. The preschool, andthe preschool teachers, are expected to help the children develop their technologicalawareness and interest in technology without being limited by traditionalperspectives on gender. However, as research has shown, teachers’ expectationsof children’s behaviour and interest in leisure time activities aregendered and reflect historically developed gendered roles in relation to technology.As this study shows there is a palpable risk of the preschool teacherson one hand focusing on girls and boys as homogenous groups, where a singleindividual gets to represent the group as a whole; and on the other hand, missinggender structures if the mindset is that gender does not factor into theirtreatment of the children at all – that they, automatically in their role astechers, act gender neutral. In this study, the pedagogical conversation wasimportant for the teachers possibility to reflect about their own preconceptions.However, the conversation did not seem to be enough, it was also importantfor the teachers to get to see and reflect on how they actually interactedwith the children in the technological activities. Only then did the teachersactually start to question their preconceptions and began to discuss new waysof acting.
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| 31. |
- Boström, Johan, et al.
(författare)
-
Who counts? : Legitimate solutions in construction activities in preschool
- 2023
-
Ingår i: International journal of technology and design education. - : Springer. - 0957-7572 .- 1573-1804. ; 33, s. 1309-1344
-
Tidskriftsartikel (refereegranskat)abstract
- As has been pointed out in previous research, teacher-led learning plays an important role in developing preschool children's technological skills and technological self-esteem. What is missing in research are more detailed analysis of how the children's and teachers' actions and interactions shape the learning process. In order to study this within the field of construction, an action research project was conducted, where construction activities were developed, implemented and revised in an iterative procedure. Data from the second cycle were analyzed for this article using graphic transcriptions and multimodal analysis, with a focus on action, interaction and experience from a pragmatist perspective. Our findings show that children who quickly and decisively engage with the material, the teachers and their peers in suggesting which material to use and/or how the material can be used, end up in a central role in the design process. These children (or their actions) often get legitimized by the teachers. Thus, in order to give children access to equal opportunities in the construction activities, it is important for teachers to understand how the children's construction-focused actions become constitutive and what their role in that process is.
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| 32. |
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| 33. |
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| 34. |
- Boström, Ola, 1963, et al.
(författare)
-
A new neck injury criterion candidate-based on injury findings in the cervical spinal ganglia after experimental neck extension trauma
- 1996
-
Ingår i: PROCEEDINGS OF THE 1996 INTERNATIONAL IRCOBI CONFERENCE ON THE BIOMECHANICS OF IMPACT, SEPTEMBER 11-13, DUBLIN, IRELAND. ; , s. 123-136
-
Konferensbidrag (refereegranskat)abstract
- In this study a mathematical model, based on Navier Stokes equations, was developed and validated against experimental data. This model predicts the pressure changes in the spinal canal as a function of the volume change inside the canal during neck bending in the x-z (sagittal) plane. Another aim of the study was to investigate pressure phenomena and ganglion injuries at static neck extension loading and dynamic neck extension trauma with a head-restraint present. Experiments on pigs were conducted. Preliminary results indicate that ganglion injuries, as well as pressure transients inside the spinal canal, seem to correlate to the phase shift when the neck passes an s-shape (or maximal retraction) during the rearward motion of the head. That is, when the upper neck quickly changes from a flexion to an extension shape. Static loading of the neck resulted in no signs of injuries to the ganglia. A possible candidate for a neck injury criterion is presented, based on the relative acceleration between the top and the bottom of the cervical spine. A tolerance level based on the pig tests is also discussed.
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| 35. |
- Boström, Ola, 1963, et al.
(författare)
-
Comparison of car seats in low speed rear-end impacts using the BioRID dummy and the new neck injury criterion (NIC).
- 2000
-
Ingår i: Accident Analysis and Prevention. ; 32:2, s. 321-328
-
Tidskriftsartikel (refereegranskat)abstract
- Long-term whiplash associated disorders (WAD) 1-3 sustained in low velocity rear-end impacts is the most common disability injury in Sweden. Therefore, to determine neck injury mechanisms and develop methods to measure neck-injury related parameters are of importance for current crash-safety research. A new neck injury criterion (NIC) has previously been proposed and evaluated by means of dummy, human and mathematical rear-impact simulations. So far, the criterion appears to be sensitive to the major car and collision related risk factors for injuries with long-term consequences. To further evaluate the applicability of NIC, four seats were tested according to a recently proposed sled-test procedure. 'Good' as well as 'bad' seats were chosen on the basis of a recently presented disability risk ranking list. The dummy used in the current tests was the Biofidelic Rear Impact Dummy (BioRID). The results of this study showed that NICmax values were generally related to the real-world risk of long-term WAD 1-3. Furthermore, these results suggested that NICmax calculated from sled tests using the BioRID dummy can be used for evaluating the neck injury risk of different car seats.
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| 36. |
- Boström, Ola, 1963, et al.
(författare)
-
Prediction of neck injuries in rear impacts based on accident data and simulations
- 1997
-
Ingår i: PROCEEDINGS OF THE 1997 INTERNATIONAL IRCOBI CONFERENCE ON THE BIOMECHANICS OF IMPACT. ; , s. 251-264
-
Konferensbidrag (refereegranskat)abstract
- Whiplash associated disorders, occurring in car accidents, are an increasing problem worldwide. According to real-life data from police records, the struck car's velocity change (delta V) and occupant gender are two of the most important factors related to Abbreviated Injury Scale (AIS) 1 neck injuries. In this study, a new rear-impact ranking of cars based on 4432 police reported accidents is presented. The ranking concerns the relative neck injury risk and compensates for the influences of car weight and gender. Moreover, some important factors influencing the risk of AIS 1 neck injury are proposed. These include: the stiffness, damping and yielding characteristics of the seat back, the muscle response of the occupant, and the delta V of the struck car and acceleration pulse. Using a mathematical model it is shown that the influence from these factors can be explained by a recently proposed neck injury criterion (NIC). This criterion is based on the neck motion at the passage of full neck retraction. The NIC, based on a number of volunteer tests, is analysed and validated. The consequence of injury outcome of an observed overall seat back stiffening is also discussed. In conclusion, for delta V below 20 km/h, real-life data show that the geometry of the head restraint is of minor importance. A seat back with low yielding limit or soft performance may be preferable. Moreover, the new NIC seems to be a good predictor of real-life neck injuries.
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| 37. |
- Boström, Per, 1982-
(författare)
-
”Det här är ju dött tåg liksom…” : en studie av metaforer för ROMANTISK KÄRLEK i talad svenska
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this study is to investigate the metaphorization of ROMANTIC LOVE in spoken Swedish. The study is based on 4 semi-structured focus group conversations with participants in two age groups; 24–33 and 50–54. A Swedish short film and questions related to the film were used as stimuli for the conversations. Research questions asked are 1) How is the concept of ROMANTIC LOVE metaphorized in the recorded group conversations? 2) How does the metaphorization vary between the conversations? and 3) What cultural model for ROMANTIC LOVE in the conversations can be reconstructed based on identified metaphorizations? The study is situated within Cognitive Linguistics and the framework of Conceptual Metaphor Theory and a Discourse Dynamics Approach to Metaphor. Consequently, metaphor is seen as a cognitive, linguistic, socio-cultural and discursive phenomenon, where metaphorization is a dynamic process that develops, adapts and flows within the conversations and between the participants. Accordingly, the identified metaphorizations are considered to be influenced by the speakers and their embodied experiences, their embodied cognition, the discourse event, and socio-cultural aspects of metaphorization. The focus of the present study, ROMANTIC LOVE, is considered as a dynamic concept based on philosophical, feminist, psychological and metaphorical research. Metaphors are identified through a discourse dynamic version of MIP and MIPVU.From the analyses, 6 systematic metaphors are proposed, where ROMANTIC LOVE is metaphorized as a PHYSICAL OBJECT (incl. as a POSSESSION and as a LIVING ORGANISM), as a CONTAINER (incl. CONSTRUCTION and BODY as a CONTAINER), as TRAVELLING together (with primary focus on TRAVELLING together rather than SOURCE or TARGET), as a UNITY (with focus on how a UNITY is ESTABLISHED, MAINTAINED and DISSOLVED, ideally by two COMPATIBLE partners), as a PHYSICAL and NATURAL FORCE and as a DISEASE (where LOVE can affect a person’s perception and sanity). In addition, ROMANTIC LOVE is, in a small number of expressions, metaphorized as a CRIME, as a PHYSICAL CONFLICT and as a GAME. The variation in metaphorization is small between the conversations. Some metaphorizations seem to be related to the age of the participants. ROMANTIC LOVE ismoreover something people usually have influence over and in some ways can control. In total, 780 metaphorical expressions and 9 source domains are identified. Departing from the interplay betweenmetaphorization and culture, a cultural model for ROMANTIC LOVE is reconstructed, where a multifaceted, embodied and experiential concept of ROMANTIC LOVE emerges.
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| 38. |
- Boström, Pontus, 1982, et al.
(författare)
-
Hypoxia converts human macrophages into triglyceride-loaded foam cells.
- 2006
-
Ingår i: Arteriosclerosis, thrombosis, and vascular biology. - 1524-4636. ; 26:8, s. 1871-6
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Atherosclerotic lesions have regions that are hypoxic. Because the lesion contains macrophages that are loaded with lipid, we investigated whether hypoxia can influence the accumulation of lipids in these cells. METHODS AND RESULTS: Exposure of human macrophages to hypoxia for 24 hours resulted in an increased formation of cytosolic lipid droplets and an increased accumulation of triglycerides. Exposure of the macrophages to oxidized low-density lipoprotein (oxLDL) increased the accumulation of cytosolic lipid droplets because of an increase in cellular cholesterol esters. The accumulation of lipid droplets in oxLDL-treated cells was further increased after hypoxia, caused by an increased level of triglycerides. Expression analyses combined with immunoblot or RT-PCR demonstrated that hypoxia increased the expression of several genes that could promote the accumulation of lipid droplets. Hypoxia increased the mRNA and protein levels of adipocyte differentiation-related protein (ADRP). It is well known that an increased expression of ADRP increases the formation of lipid droplets. Hypoxia decreased the expression of enzymes involved in beta-oxidation (acyl-coenzyme A synthetase and acyl-coenzyme A dehydrogenase) and increased the expression of stearoyl-coenzyme A desaturase, an important enzyme in the fatty acid biosynthesis. Moreover, exposure to hypoxia decreased the rate of beta-oxidation, whereas the accumulation of triglycerides increased. CONCLUSIONS: The results demonstrate that exposure of human macrophages to hypoxia causes an accumulation of triglyceride-containing cytosolic lipid droplets. This indicates that the hypoxia present in atherosclerotic lesions can contribute to the formation of the lipid-loaded macrophages that characterize the lesion and to the accumulation of triglycerides in such lesions.
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| 39. |
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| 40. |
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| 41. |
- Boström, Per Staffan, 1946-
(författare)
-
RESURSTILLVÄXT. : Målet för hållbar utveckling och hållbar tillväxt!
-
Annan publikation (populärvet., debatt m.m.)abstract
- Bokprojektet ”HÅLLBAR TILLVÄXT – 2000-talets ledarutmaning” Detta bokprojekt som nu föreligger i ett första manus är uppstarten på en longitudinell och företagsnära forskning om hållbart och resurseffektivt företagande. Projektet som påbörjades 2002 är framförallt engagerat i frågan hur begreppet ”Sustainable Growth”, hållbar tillväxt, ska bli lättare att kommunicera och förstå för att vara användbart i företagets affärsverksamhet. Projektet har genomförts i samarbete med ett antal företag. Successivt har det också uppstått ett behov att finna ett tydligt mål, en enkel formel och en arbetsform för långsiktiga beslut och styrning mot ekonomiskt hållbar tillväxt av alla resurser (per definition) i en organisation. Projektet avhandlar därför innebörden av begreppet RESURSTILLVÄXT.
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| 42. |
- Boström, Pontus, 1982, et al.
(författare)
-
The SNARE protein SNAP23 and the SNARE-interacting protein Munc18c in human skeletal muscle are implicated in insulin resistance/type 2 diabetes.
- 2010
-
Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 59:8, s. 1870-8
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Our previous studies suggest that the SNARE protein synaptosomal-associated protein of 23 kDa (SNAP23) is involved in the link between increased lipid levels and insulin resistance in cardiomyocytes. The objective was to determine whether SNAP23 may also be involved in the known association between lipid accumulation in skeletal muscle and insulin resistance/type 2 diabetes in humans, as well as to identify a potential regulator of SNAP23. RESEARCH DESIGN AND METHODS: We analyzed skeletal muscle biopsies from patients with type 2 diabetes and healthy, insulin-sensitive control subjects for expression (mRNA and protein) and intracellular localization (subcellular fractionation and immunohistochemistry) of SNAP23, and for expression of proteins known to interact with SNARE proteins. Insulin resistance was determined by a euglycemic hyperinsulinemic clamp. Potential mechanisms for regulation of SNAP23 were also investigated in the skeletal muscle cell line L6. RESULTS: We showed increased SNAP23 levels in skeletal muscle from patients with type 2 diabetes compared with that from lean control subjects. Moreover, SNAP23 was redistributed from the plasma membrane to the microsomal/cytosolic compartment in the patients with the type 2 diabetes. Expression of the SNARE-interacting protein Munc18c was higher in skeletal muscle from patients with type 2 diabetes. Studies in L6 cells showed that Munc18c promoted the expression of SNAP23. CONCLUSIONS: We have translated our previous in vitro results into humans by showing that there is a change in the distribution of SNAP23 to the interior of the cell in skeletal muscle from patients with type 2 diabetes. We also showed that Munc18c is a potential regulator of SNAP23.
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| 43. |
- Boström-Rost, Per, 1988-, et al.
(författare)
-
Informative Path Planning for Active Tracking of Agile Targets
- 2019
-
Ingår i: Proceedings of 2019 IEEE Aerospace Conference. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538668542 - 9781538668559 ; , s. 1-11
-
Konferensbidrag (refereegranskat)abstract
- This paper proposes a method to generate informative trajectories for a mobile sensor that tracks agile targets.The goal is to generate a sensor trajectory that maximizes the tracking performance, captured by a measure of the covariance matrix of the target state estimate. The considered problem is acombination of estimation and control, and is often referred to as informative path planning (IPP). When using nonlinear sensors, the tracking performance depends on the actual measurements, which are naturally unavailable in the planning stage.The planning problem hence becomes a stochastic optimization problem, where the expected tracking performance is used inthe objective function. The main contribution of this work is anapproximation of the problem based on deterministic sampling of the predicted target distribution. This is in contrast to prior work, where only the most likely target trajectory is considered.It is shown that the proposed method greatly improves the ability to track agile targets, compared to a baseline approach.
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| 44. |
- Boström-Rost, Per, et al.
(författare)
-
Informative Path Planning in the Presence of Adversarial Observers
- 2019
-
Ingår i: 2019 22th International Conference on Information Fusion (FUSION). - : Institute of Electrical and Electronics Engineers (IEEE). - 9780996452786 - 9781728118406
-
Konferensbidrag (refereegranskat)abstract
- This paper considers the problem of gathering information about features of interest in adversarial environments using mobile robots equipped with sensors. The problem is formulated as an informative path planning problem where the objective is to maximize the gathered information while minimizing the tracking performance of the adversarial observer. The optimization problem, that at first glance seems intractable to solve to global optimality, is shown to be equivalent to a mixed-integer semidefinite program that can be solved to global optimality using off-the-shelf optimization tools.
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| 45. |
- Boström-Rost, Per, et al.
(författare)
-
On Global Optimization for Informative Path Planning
- 2018
-
Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 2:4, s. 833-838
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of path planning for mobilesensors with the task of target monitoring is considered. A receding horizon optimal control approach based on the information filter is presented, where the limited field of view of the sensor can be modeled by introducing binary variables. The resulting nonlinear mixed integer problem to be solved in each sample, with no apparent tractable solution, is shown to be equivalent to a problem that robustly can be solved to global optimality using off-the-shelf optimization tools.
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| 46. |
- Boström-Rost, Per, 1988-
(författare)
-
On Informative Path Planning for Tracking and Surveillance
- 2019
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis studies a class of sensor management problems called informative path planning (IPP). Sensor management refers to the problem of optimizing control inputs for sensor systems in dynamic environments in order to achieve operational objectives. The problems are commonly formulated as stochastic optimal control problems, where to objective is to maximize the information gained from future measurements. In IPP, the control inputs affect the movement of the sensor platforms, and the goal is to compute trajectories from where the sensors can obtain measurements that maximize the estimation performance. The core challenge lies in making decisions based on the predicted utility of future measurements.In linear Gaussian settings, the estimation performance is independent of the actual measurements. This means that IPP becomes a deterministic optimal control problem, for which standard numerical optimization techniques can be applied. This is exploited in the first part of this thesis. A surveillance application is considered, where a mobile sensor is gathering information about features of interest while avoiding being tracked by an adversarial observer. The problem is formulated as an optimization problem that allows for a trade-off between informativeness and stealth. We formulate a theorem that makes it possible to reformulate a class of nonconvex optimization problems with matrix-valued variables as convex optimization problems. This theorem is then used to prove that the seemingly intractable IPP problem can be solved to global optimality using off-the-shelf optimization tools.The second part of this thesis considers tracking of a maneuvering target using a mobile sensor with limited field of view. The problem is formulated as an IPP problem, where the goal is to generate a sensor trajectory that maximizes the expected tracking performance, captured by a measure of the covariance matrix of the target state estimate. When the measurements are nonlinear functions of the target state, the tracking performance depends on the actual measurements, which depend on the target’s trajectory. Since these are unavailable in the planning stage, the problem becomes a stochastic optimal control problem. An approximation of the problem based on deterministic sampling of the distribution of the predicted target trajectory is proposed. It is demonstrated in a simulation study that the proposed method significantly increases the tracking performance compared to a conventional approach that neglects the uncertainty in the future target trajectory.
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| 47. |
- Boström-Rost, Per, 1988-, et al.
(författare)
-
Optimal Range and Beamwidth for Radar Tracking of Maneuvering Targets Using Nearly Constant Velocity Filters
- 2020
-
Ingår i: Proceedings of 2020 IEEE Aerospace Conference. - 9781728127347 - 9781728127354
-
Konferensbidrag (refereegranskat)abstract
- For a given radar system on an unmanned air vehicle, this work proposes a method to find the optimal tracking rangeand the optimal beamwidth for tracking a maneuvering target. An inappropriate optimal range or beamwidth is indicative ofthe need for a redesign of the radar system. An extended Kalman filter (EKF) is employed to estimate the state of the target using measurements of the range and bearing from the sensor to the target. The proposed method makes use of an alpha-beta filter to predict the expected tracking performanceof the EKF. Using an assumption of the maximum acceleration of the target, the optimal tracking range (or beamwidth) is determined as the one that minimizes the maximum mean squared error (MMSE) of the position estimates while satisfying a user-defined constraint on the probability of losing track of the target.The applicability of the design method is verified using Monte Carlo simulations.
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| 48. |
- Boström-Rost, Per, 1988-, et al.
(författare)
-
PMBM Filter With Partially Grid-Based Birth Model With Applications in Sensor Management
- 2022
-
Ingår i: IEEE Transactions on Aerospace and Electronic Systems. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9251 .- 1557-9603 .- 2371-9877. ; 58:1, s. 530-540
-
Tidskriftsartikel (refereegranskat)abstract
- This article introduces a Poisson multi-Bernoulli mixture (PMBM) filter in which the intensities of target birth and undetected targets are grid-based. A simplified version of the Rao-Blackwellized point mass filter is used to predict the intensity of undetected targets and to initialize tracks of targets detected for the first time. The grid approximation can efficiently represents intensities with abrupt changes with relatively few grid points compared to the number of Gaussian components needed in conventional PMBM implementations. This is beneficial in scenarios where the sensors field of view is limited. The proposed method is illustrated in a sensor management setting, where trajectories of sensors with limited fields of view are controlled to search for and track the targets in a region of interest.
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| 49. |
- Boström-Rost, Per, 1988-, et al.
(författare)
-
Sensor management for search and track using the Poisson multi-Bernoulli mixture filter
- 2021
-
Ingår i: IEEE Transactions on Aerospace and Electronic Systems. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9251 .- 1557-9603. ; 57:5, s. 2771-2783
-
Tidskriftsartikel (refereegranskat)abstract
- A sensor management method for joint multi-target search and track problems is proposed, where a single user-defined parameter allows for a trade-off between the two objectives. The multi-target density is propagated using the Poisson multi-Bernoulli mixture filter, which eliminates the need for a separate handling of undiscovered targets and provides the theoretical foundation for a unified search and track method. Monte Carlo simulations of two scenarios are used to evaluate the performance of the proposed method.
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| 50. |
- Boström-Rost, Per, 1988-
(författare)
-
Sensor Management for Target Tracking Applications
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many practical applications, such as search and rescue operations and environmental monitoring, involve the use of mobile sensor platforms. The workload of the sensor operators is becoming overwhelming, as both the number of sensors and their complexity are increasing. This thesis addresses the problem of automating sensor systems to support the operators. This is often referred to as sensor management. By planning trajectories for the sensor platforms and exploiting sensor characteristics, the accuracy of the resulting state estimates can be improved. The considered sensor management problems are formulated in the framework of stochastic optimal control, where prior knowledge, sensor models, and environment models can be incorporated. The core challenge lies in making decisions based on the predicted utility of future measurements.In the special case of linear Gaussian measurement and motion models, the estimation performance is independent of the actual measurements. This reduces the problem of computing sensing trajectories to a deterministic optimal control problem, for which standard numerical optimization techniques can be applied. A theorem is formulated that makes it possible to reformulate a class of nonconvex optimization problems with matrix-valued variables as convex optimization problems. This theorem is then used to prove that globally optimal sensing trajectories can be computed using off-the-shelf optimization tools. As in many other fields, nonlinearities make sensor management problems more complicated. Two approaches are derived to handle the randomness inherent in the nonlinear problem of tracking a maneuvering target using a mobile range-bearing sensor with limited field of view. The first approach uses deterministic sampling to predict several candidates of future target trajectories that are taken into account when planning the sensing trajectory. This significantly increases the tracking performance compared to a conventional approach that neglects the uncertainty in the future target trajectory. The second approach is a method to find the optimal range between the sensor and the target. Given the size of the sensor's field of view and an assumption of the maximum acceleration of the target, the optimal range is determined as the one that minimizes the tracking error while satisfying a user-defined constraint on the probability of losing track of the target. While optimization for tracking of a single target may be difficult, planning for jointly maintaining track of discovered targets and searching for yet undetected targets is even more challenging. Conventional approaches are typically based on a traditional tracking method with separate handling of undetected targets. Here, it is shown that the Poisson multi-Bernoulli mixture (PMBM) filter provides a theoretical foundation for a unified search and track method, as it not only provides state estimates of discovered targets, but also maintains an explicit representation of where undetected targets may be located. Furthermore, in an effort to decrease the computational complexity, a version of the PMBM filter which uses a grid-based intensity to represent undetected targets is derived.
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