| 1. |
- Ankelhed, Daniel, 1980-
(författare)
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On low order controller synthesis using rational constraints
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to design robust controllers, H-infinity synthesis is a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the plant, the problem is no longer convex and it is then relatively hard to solve. These problems become very complex, even when the order of the system to be controlled is low.The approach used in the thesis is based on formulating the constraint on the maximum order of the plant as a polynomial equation. By using the fact that the polynomial is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex polynomial function is to be minimized over a convex set defined by linear matrix inequalities.To solve this optimization problem, two methods have been proposed. The first method is a barrier method and the second one is a method based on a primal-dual framework. These methods have been evaluated on several problems and compared with a well-known method found in the literature. To motivate this choice of method, we have made a brief survey of available methods available for solving the same or related problems.The proposed methods emerged as the best methods among the three for finding lower order controllers with the same or similar performance as the full order controller. When the aim is to find the lowest order controller with no worse than +50% increase in the closed loop H-infinity norm, then the three compared methods perform equally well.
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| 2. |
- Bengtsson, Johan, et al.
(författare)
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A Robot Playing Scrabble Using Visual Feedback
- 2000
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Ingår i: IFAC Proceedings Volumes. ; 33:27, s. 551-556
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Tidskriftsartikel (refereegranskat)abstract
- Today most industrial robot systems use dedicated and rather limited sensors, and available control systems provide limited support for feedback control. Aiming towards more autonomous robot systems, we want to improve flexibility. The game Scrabble is used as a test problem capturing these aspects. Our approach is to incorporate visual servoing and a conventional powerful off-line prograrnrning (OLP) system into the real-time control system, providing task specification and visual debugging. We use the OLP tool Envision from Deneb and an ABB robot with reconfigured control system, where the control system has an Open Robot Control architecture (ORC). The vision system is connected to a host computer and the camera is attached to the robot gripper. By extending the control system, we have designed and implemented both the vision system and the application for the Scrabble game. Our system implementation shows that ORC constitutes a necessary support for incorporation of real-time visual feedback and that OLP may effectively be used with real-time feedback of sensor data.
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| 3. |
- Bruce, Michael G, et al.
(författare)
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International Circumpolar Surveillance System for invasive pneumococcal disease, 1999-2005
- 2008
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Ingår i: Emerging Infectious Diseases. - Atlanta, GA : National Center for Infectious Diseases, Centers for Disease Control and Prevention (CDC). - 1080-6040 .- 1080-6059. ; 14:1, s. 25-33
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Tidskriftsartikel (refereegranskat)abstract
- The International Circumpolar Surveillance System is a population-based surveillance network for invasive bacterial disease in the Arctic. The 7-valent pneumococcal conjugate vaccine (PCV7) was introduced for routine infant vaccination in Alaska (2001), northern Canada (2002-2006), and Norway (2006). Data for invasive pneumococcal disease (IPD) were analyzed to identify clinical findings, disease rates, serotype distribution, and antimicrobial drug susceptibility; 11,244 IPD cases were reported. Pneumonia and bacteremia were common clinical findings. Rates of IPD among indigenous persons in Alaska and northern Canada were 43 and 38 cases per 100,000 population, respectively. Rates in children <2 years of age ranged from 21 to 153 cases per 100,000 population. In Alaska and northern Canada, IPD rates in children <2 years of age caused by PCV7 serotypes decreased by >80% after routine vaccination. IPD rates are high among indigenous persons and children in Arctic countries. After vaccine introduction, IPD caused by non-PCV7 serotypes increased in Alaska.
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| 4. |
- Bylund, Annika, et al.
(författare)
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Anticancer effects of a plant lignan 7-hydroxymatairesinol on a prostate cancer model in vivo.
- 2005
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Ingår i: Experimental biology and medicine. - 1535-3702 .- 1535-3699. ; 230:3, s. 217-223
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Tidskriftsartikel (refereegranskat)abstract
- Clinical intervention studies and experimental studies with lignan-rich diets suggest that lignans may have inhibitory effects on prostate cancer, but no clinical or experimental studies with purified lignans have been published. The purpose of this study was to investigate the effect of a plant lignan 7-hydroxymatairesinol (HMR) on LNCaP human prostate cancer xenografts in athymic mice. Athymic nude male mice were injected subcutaneously with LNCaP cells. Starting 3 days after tumor cell injections, a control diet or a control diet supplemented with 0.15% or 0.30% of HMR was administered to mice and the tumor take rate and growth was observed for 9 weeks. HMR diet inhibited the growth of LNCaP tumors. Mice treated with HMR had smaller tumor volume, lower tumor take rate, increased proportion of nongrowing tumors, and higher tumor cell apoptotic index compared with controls. Furthermore, the cell proliferation index was reduced in mice receiving the 0.30% HMR diet compared with mice receiving the control diet. Our results suggest that dietary HMR started at the early phase of the tumor development inhibits the growth of the LNCaP human prostate cancer xenografts in athymic male mice.
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| 5. |
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| 6. |
- Dijken, Jan W.V. van, 1947-, et al.
(författare)
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Samarbete breddar forskning : Oral Biomaterialgruppen, Umeå
- 2008
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Ingår i: Tandläkartidningen. - : Sveriges Tandläkarförbund. ; 100:5, s. 74-79
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Vid institutionen för odontologi vid Umeå Universitet finns en lång tradition av biomaterialforskning. För drygt två år sedan samlades större delen av den forskningen i ett vetenskapligt nätverk. Här beskrivs ett axplock av det breda forskningsarbetet.
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| 7. |
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| 8. |
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| 9. |
- Hansson, Lars-Anders, et al.
(författare)
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Consumption patterns, complexity and enrichment in aquatic food chains
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1399, s. 901-906
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between consumers and prey, and their impact on biomass distribution among trophic levels, are central issues in both empirical and theoretical ecology. In a long-term experiment, where all organisms, including the top predator, were allowed to respond to environmental conditions by reproduction, we tested predictions from `prey-dependent' and `ratio-dependent' models. Prey-dependent models made correct predictions only in the presence of strong interactors in simple food chains, but failed to predict patterns in more complex situations. Processes such as omnivory, consumer excretion, and unsuitable prey-size windows (invulnerable prey) increased the complexity and created patterns resembling ratio-dependent consumption. However, whereas the prey-dependent patterns were created by the mechanisms predicted by the model, ratio-dependent patterns were not, suggesting that they may be right for the wrong reason'. We show here that despite the enormous complexity of ecosystems, it is possible to identify and disentangle mechanisms responsible for observed patterns in community structure, as well as in biomass development of organisms ranging in size from bacteria to fish.
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| 10. |
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| 11. |
- Hermansson, Ulric, et al.
(författare)
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Screening for high-risk and elevated alcohol consumption in day and shift workers by use of the AUDIT and CDT
- 2003
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Ingår i: Occupational Medicine. - : Oxford University Press (OUP). - 0962-7480 .- 1471-8405. ; 53:8, s. 518-526
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Tidskriftsartikel (refereegranskat)abstract
- The present findings on employees who attended for regular health examinations suggest that shift workers did not show a higher level of risky alcohol consumption than day workers, according to the results with the AUDIT, CDT and GGT. On the contrary, the two-shift workers appeared to drink significantly less.
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| 12. |
- Ive, Anders, et al.
(författare)
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Garbage collector interface
- 2002
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Ingår i: Proceedings of the Tenth Nordic Workshop on Programming and Software Development Tools and Techniques (NWPER 2002).
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Konferensbidrag (refereegranskat)abstract
- The purpose of the presented garbage collector interface is to provide a universal interface for many different implementations of garbage collectors. This is to simplify the integration and exchange of garbage collectors, but also to support incremental, non-conservative, and thread safe implementations. Due to the complexity of the interface, it is aimed at code generators and preprocessors. Experiences from ongoing implementations indicate that the garbage collector interface successfully provides the necessary functionality in an efficient way,
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| 13. |
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| 14. |
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| 15. |
- Lannergård, Anders, et al.
(författare)
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The time course of body temperature, serum amyloid A protein, C-reactive protein and interleukin-6 in patients with bacterial infection during the initial 3 days of antibiotic therapy
- 2009
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 41:9, s. 663-671
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Tidskriftsartikel (refereegranskat)abstract
- The accuracy of using body temperature, serum amyloid A (SAA), C-reactive protein (CRP) and interleukin-6 (IL-6) in the work-up for early or late step-down therapy after an initial course of intravenous cefuroxime was investigated. Eighty-one hospitalized patients with an initial course of cefuroxime were retrospectively classified with one of the following diagnoses: bacterial infection without known focus, pneumonia, bronchitis, pyelonephritis, skin and soft-tissue infections or fever of other origin. The majority of the patients had sepsis (91% or 74/81) of whom 6 patients had severe sepsis. The inter-individual variability of body temperature, SAA, CRP and IL-6 was considerable. The time course of SAA and CRP during the first 24 h in patients with sepsis with a short duration of illness but without septic shock showed increasing levels during the initial course of intravenous therapy. In contrast, body temperature and IL-6 decreased, regardless of illness duration. Beyond 24 h, all 4 biomarkers declined, again regardless of the duration of illness. After the initial course of cefuroxime, biomarkers were non-distinguishing in terms of guidance in the judgement of early or late step-down therapy. Further studies are proposed for biomarker guidance antibiotic therapy in sepsis patients without septic shock.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Persson, Anders, et al.
(författare)
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Effects of enrichment on simple aquatic food webs
- 2001
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 157:6, s. 654-669
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Tidskriftsartikel (refereegranskat)abstract
- Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on populations and that equilibrium population densities will change at the top trophic level and every second level below. We experimentally tested these predictions in three aquatic food web configurations subjected to either high or low nutrient additions. The results were structured by viewing the systems as either food chains or webs and showed that trophic level biomass increased with enrichment, which contradicts food chain theory. However, within each trophic level, food web configuration affected the extent to which different functional groups responded to enrichment. By dividing trophic levels into functional groups, based on vulnerability to consumption, we were able to identify significant effects that were obscured when systems were viewed as food chains. The results support the prediction that invulnerable prey may stabilize trophic-level dynamics by replacing other, more vulnerable prey. Furthermore, the vulnerable prey, such as Daphnia and edible algae, responded as predicted by the paradox of enrichment hypothesis; that is, variability in population density increased with enrichment. Hence, by describing ecosystems as a matrix of food web interactions, and by recognizing the interplay between interspecific competition and predation, a more complete description of the ecosystem function was obtained compared to when species were placed into distinct trophic levels.
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| 21. |
- Persson, Anders, et al.
(författare)
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Effects of enrichment on simple aquatic food webs
- 2001
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Ingår i: The American Naturalist. ; 157:6, s. 654-669
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Tidskriftsartikel (refereegranskat)abstract
- Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on
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| 22. |
- Qatarneh, Sharif, 1972-
(författare)
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Development of a Whole Body Atlas for Radiation Therapy Planning and Treatment Optimization
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of radiation therapy is to obtain the highest possible probability of tumor cure while minimizing adverse reactions in healthy tissues. A crucial step in the treatment process is to determine the location and extent of the primary tumor and its loco regional lymphatic spread in relation to adjacent radiosensitive anatomical structures and organs at risk. These volumes must also be accurately delineated with respect to external anatomic reference points, preferably on surrounding bony structures. At the same time, it is essential to have the best possible physical and radiobiological knowledge about the radiation responsiveness of the target tissues and organs at risk in order to achieve a more accurate optimization of the treatment outcome.A computerized whole body Atlas has therefore been developed to serve as a dynamic database, with systematically integrated knowledge, comprising all necessary physical and radiobiological information about common target volumes and normal tissues. The Atlas also contains a database of segmented organs and a lymph node topography, which was based on the Visible Human dataset, to form standard reference geometry of organ systems. The reference knowledgebase and the standard organ dataset can be utilized for Atlas-based image processing and analysis in radiation therapy planning and for biological optimization of the treatment outcome. Atlas-based segmentation procedures were utilized to transform the reference organ dataset of the Atlas into the geometry of individual patients. The anatomic organs and target volumes of the database can be converted by elastic transformation into those of the individual patient for final treatment planning. Furthermore, a database of reference treatment plans was started by implementing state-of-the-art biologically based radiation therapy planning techniques such as conformal, intensity modulated, and radiobiologically optimized treatment planning.The computerized Atlas can be viewed as a central framework that contains different forms of optimal treatment plans linked to all the essential information needed in treatment planning, which can be adapted to a given patient, in order to speed up treatment plan convergence. The Atlas also offers a platform to synthesize the results of imaging studies through its advanced geometric transformation and segmentation procedures. The whole body Atlas is anticipated to become a physical and biological knowledgebase that can facilitate, speed up and increase the accuracy in radiation therapy planning and treatment optimization.
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| 23. |
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| 24. |
- Rydh, Anders, et al.
(författare)
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Radioimmunotherapy of DU-145 tumours in nude mice--a pilot study with E4, a novel monoclonal antibody against prostate cancer.
- 1999
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 38:8, s. 1075-1079
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Tidskriftsartikel (refereegranskat)abstract
- The anti-tumour effect of the 131I-labelled antiprostate monoclonal antibody (MAb) E4 was studied in an experimental model with 41 nude mice, subcutaneously xenografted with a human prostate cancer cell line (DU-145). The mice were divided into four study groups, i.e. one receiving single and another repeated injections of the radiolabelled MAb. A third group was injected with non-labelled MAb, and the fourth served as an untreated control group. The tumour volumes increased similarly in all groups during the 27-day observation period. The tumour tissue was morphologically disintegrated in the group that received repeated radioimmunotherapy (RIT). The tumours from this group contained large fluid-filled cystic parts and demonstrated pronounced cellular and subcellular polymorphism in the remaining viable tumour tissue. The untreated control tumours and single therapy tumours remained solid. The proportion of the total tumour volume that consisted of viable tumour cells, as determined by morphometric techniques, was significantly lower in the 131I-E4-treated groups. The use of 131I-labelled E4 MAb has thus demonstrated a promising therapeutic potential.
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| 25. |
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| 26. |
- Viberg, Anders, et al.
(författare)
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A population pharmacokinetic model for cefuroxime using cystatin C as a marker of renal function
- 2006
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Ingår i: British Journal of Clinical Pharmacology. - : Wiley. - 0306-5251 .- 1365-2125. ; 62:3, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Since cefuroxime mainly is excreted by renal filtration, dosing is currently based on serum creatinine (Scr) or creatinine clearance (CLcr). However, it has been suggested that cystatin C (CysC) is superior to Scr as a marker of renal function. The aim of this prospective study was to develop a population model that describes the pharmacokinetics of cefuroxime and to investigate the usefulness of CysC as a covariate of the model parameters. Methods: Ninety-seven patients were studied (CLcr range 6.5-115 ml min(-1)). Blood samples (n = 407) for the determination of cefuroxime were withdrawn according to a sparse data sampling schedule and analysed by liquid chromatography mass spectrometry. The population analysis was performed in NONMEM. Results: A two-compartment model described the data well. The biomarkers Scr, CLcr and CysC were evaluated as covariates on clearance (CL). The model that included CysC generated the best fit. In the final population model CL was a function of CysC and body weight, whereas V-1 was only a function of body weight. Final parameter estimates (relative standard errors) were 6.00 (3.2%) l h(-1), 11.4 (5.3%) l and 5.11 (11%) l for CL, V-1 and V-2, respectively. Conclusion: Based on the results of the present study, and because CysC is practical to use in the clinic, it is suggested that individual dosing of cefuroxime may be based on CysC rather than on Scr or CLcr. Furthermore, our final population model may be useful as a tool when designing new dosing schedules for cefuroxime.
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| 27. |
- Wan, Y., et al.
(författare)
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First reported nonpeptide AT1 receptor agonist (L-162,313) acts as an AT2 receptor agonist in vivo
- 2004
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Ingår i: J Med Chem. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 47:6, s. 1536-1546
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Tidskriftsartikel (refereegranskat)abstract
- In this investigation, it is demonstrated that the first nonpeptide AT(1) receptor agonist L-162,313 (1), disclosed in 1994, also acts as an agonist at the AT(2) receptor. In anesthetized rats, administration of compound 1 intravenously or locally in the duodenum increased duodenal mucosal alkaline secretion, effects that were sensitive to the selective AT(2) receptor antagonist PD-123,319. The data strongly suggest that 1 is an AT(2) receptor agonist in vivo. To the best of our knowledge, this substance is the first nonpeptidic low-molecular weight compound with an agonistic effect mediated through the AT(2) receptor.
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| 28. |
- Westerdahl, Christina, et al.
(författare)
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High frequency of primary hyperaldosteronism among hypertensive patients from a primary care area in Sweden
- 2006
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Ingår i: Scandinavian Journal of Primary Health Care. - : Informa UK Limited. - 0281-3432 .- 1502-7724. ; 24:3, s. 154-159
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To search for primary hyperaldosteronism (PHA) among previously known hypertensive patients in primary care, using the aldosterone/renin ratio (ARR), and to evaluate clinical and biochemical characteristics in patients with high or normal ratio. Design. Patient survey study. Setting and subjects. The study population was recruited by written invitation among hypertensive patients in two primary care areas in Sweden. A total of 200 patients met the criteria and were included in the study. Main outcome measures. The ARR was calculated from serum aldosterone and plasma renin concentrations. The cut-off level for ARR was set to 100, as confirmed in 28 healthy subjects. Patients with increased ARR were considered for a confirmatory test, using the fludrocortisone suppression test. Results. Of 200 patients, 50 patients had ARR >100; 26 patients were further evaluated by fludrocortisone suppression test. Seventeen of these patients had an incomplete aldosterone inhibition. Conclusion. In total 17 of 200 evaluated patients (8.5%) had an incomplete suppression with fludrocortisone. This confirms previous reports on a high frequency of PHA. No significant biochemical or clinical differences were found among hypertensive patients with PHA compared with the whole sample.
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| 29. |
- Westerdahl, Christina, et al.
(författare)
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Re-evaluation of the fludrocortisone test: duration, NaCl supplementation and cut-off limits for aldosterone
- 2009
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Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 69:2, s. 234-241
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Primary aldosteronism (PA) is the most common form of secondary hypertension. Thus, the aims of this study were: (1) to clarify whether the fludrocortisone suppression test (FST), which confirms autonomous aldosterone secretion, is reliable when carried out during a shorter period of time and (2) to confirm the importance of NaCl supplementation. The cut-off limits already obtained for aldosterone in healthy subjects during the FST were applied in hypertensive patients with a high aldosterone to renin ratio (ARR). Material and methods. The healthy subjects were allocated to three groups. Fludrocortisone was administered 4 times daily over 4 days and sodium chloride was supplemented in 3 different doses. The result was applied in 24 hypertensive patients, in 24 healthy subjects (10 women (23-38 years old) and 14 men (23-58 years old)) and in 24 patients with hypertension and high ARR (16 women (45-74 years old) and 8 men (56-73 years old)). Blood pressure, aldosterone, renin, potassium and sodium were measured. Results. After three days of FST, there was a significant decrease in the serum level of aldosterone in the healthy subjects, regardless of high or low sodium chloride supplementation (p0.001). The decrease in serum aldosterone was significantly less pronounced in patients with PA than in healthy subjects and hypertensive patients without PA (p0.001). The 95th percentile of plasma aldosterone at the end of the test was 225 pmol/L. Conclusions. The FST can be shortened to 3 days and a daily 500 mg NaCl supplementation is sufficient. A cut-off value for aldosterone of 225 pmol/L after 4 days with FST is appropriate.
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| 30. |
- Abdurahman, Samir, et al.
(författare)
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Mutation in the loop C-terminal to the cyclophilin A binding site of HIV-1 capsid protein disrupts proper virus assembly and infectivity
- 2007
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Ingår i: Retrovirology. - : Springer Science and Business Media LLC. - 1742-4690. ; 4, s. 19-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effects associated with two single amino acid substitution mutations in HIV-1 capsid (CA), the E98A and E187G. Both amino acids are well conserved among all major HIV-1 subtypes. HIV-1 infectivity is critically dependent on proper CA cone formation and mutations in CA are lethal when they inhibit CA assembly by destabilizing the intra and/or inter molecular CA contacts, which ultimately abrogate viral replication. Glu98, which is located on a surface of a flexible cyclophilin A binding loop is not involved in any intra-molecular contacts with other CA residues. In contrast, Glu187 has extensive intra-molecular contacts with eight other CA residues. Additionally, Glu187 has been shown to form a salt-bridge with Arg18 of another N-terminal CA monomer in a N-C dimer. However, despite proper virus release, glycoprotein incorporation and Gag processing, electron microscopy analysis revealed that, in contrast to the E187G mutant, only the E98A particles had aberrant core morphology that resulted in loss of infectivity.
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| 31. |
- Adami, Johanna, et al.
(författare)
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Smoking and the risk of leukemia, lymphoma, and multiple myeloma (Sweden)
- 1998
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Ingår i: Cancer Causes and Control. - 0957-5243 .- 1573-7225. ; 9:1, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- While several epidemiologic studies have indicated a link between smoking and the risk of developing hematolymphoproliferative cancers (chiefly leukemias, lymphomas, and multiple myelomas), in particular myeloid leukemia, the role of tobacco in the etiology of these neoplasms remains unclear. To evaluate the potential impact of tobacco use on development of leukemia, lymphoma, and multiple myeloma, we conducted a cohort study of 334,957 Swedish construction workers using prospectively collected exposure-information with complete long-term follow-up. A total of 1,322 incident neoplasms occurred during the study period, 1971-91. We found no significant association between smoking status, number of cigarettes smoked, or duration of smoking and the risk of developing leukemias, lymphomas, or multiple myeloma. There was a suggestion of a positive association between smoking and the risk of developing Hodgkin's disease, although the rate ratios were not significantly elevated, except for young current smokers. No positive dose-risk trends emerged. Our study provides no evidence that smoking bears any major relationship to the occurrence of leukemias, non-Hodgkin's lymphomas, or multiple myeloma.
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| 32. |
- Agardh, Emilie E, et al.
(författare)
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Work stress and low sense of coherence is associated with type 2 diabetes in middle-aged Swedish women.
- 2003
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Ingår i: Diabetes Care. - : American Diabetes Association. - 0149-5992 .- 1935-5548. ; 26:3, s. 719-24
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The risk of type 2 diabetes is suggested to be increased for individuals exposed to stress. We analyzed the association of work stress by high demands, low decision latitude, and job strain (combination of high demands and low decision latitude) with type 2 diabetes. We also studied low sense of coherence (SOC) (a factor for successful coping with stressors) in association with type 2 diabetes. Finally, we investigated the combination of SOC and demands or SOC and decision latitude in association with the disease. RESEARCH DESIGN AND METHODS: This cross-sectional study recruited 4821 healthy Swedish women (aged 35-56 years) residing in five municipalities in the Stockholm area. An oral glucose tolerance test identified 52 women with type 2 diabetes. Relative risks (RRs) with 95% CIs were estimated in a logistic multiple regression analysis. RESULTS: No association was found between high demands and type 2 diabetes (RR 1.1 [CI 0.5-2.2]). Low decision latitude was associated with type 2 diabetes with a RR of 2.2 (1.0-4.8). The RR of type 2 diabetes with low SOC was 3.7 (1.2-11.2). The combination of low SOC and low decision latitude was associated with type 2 diabetes with a RR of 2.6 (1.2-5.7). Homeostasis model assessment revealed an association of 4.2 (1.2-15.0) between low SOC and insulin resistance. CONCLUSIONS: This study provided new evidence that stress factors such as low decision latitude at work and low SOC were associated with type 2 diabetes in middle-aged Swedish women.
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| 33. |
- Ahlberg, Anders, et al.
(författare)
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Institutional promotion of doctoral supervision and research quality
- 2009
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Konferensbidrag (refereegranskat)abstract
- In our experience, doctoral supervision seminars and training (and associated literature) focus the supervisor-student relationship to an extent largely leaving aspects of learning, enculturation and subject discipline aside. In 2006-2008 we therefore developed and implemented a 3-week programme compulsory for new primary research supervisors (docent degree) with a wider scope, at the faculties Engineering and Natural Sciences, Lund University, Sweden. The programme include • Social and legal dimensions of the student-supervisor relationship; where participants share experienced accounts of supervisor-student situations. These were documented and analysed with respect to selected models of social theory. • Self-analysis of participants´ written accounts of their research principles and practices, and aspects of research creativity (philosophy of science) • Participant development of discipline-specific doctoral student learning activities.• Project management principles and practice, research career analysis• Research presentation and research situation feedback skills. The framework aims to develop participants´ integrated meta-perspective on their research and supervisor situation, to increase chances of successful doctoral projects and increase long-term research creativity. The programme (five participant groups of 15-20 participants each 2006-2008) has received supportive participant reactions indicating valuable conceptual change (although some were provoked during self-analysis of their academic practice). The programme will be followed up by alumni focus group interviews three years after programme completion (this fall) in order to understand long-term effects on academic behaviour.
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| 40. |
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| 41. |
- Ahlsson, Anders, 1962-
(författare)
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Atrial fibrillation in cardiac surgery
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atrial fibrillation (AF) is the most common arrhythmia seen in clinical practice. In cardiac surgery, one-third of the patients experience episodes of AF during the first postoperative days (postoperative AF), and patients with preoperative AF (concomitant AF) can be offered ablation procedures in conjunction with surgery, in order to restore ordinary sinus rhythm (SR). The aim of this work was to study the relation between postoperative AF and inflammation; the long-term consequences of postoperative AF on mortality and late arrhythmia; and atrial function after concomitant surgical ablation for AF. In 524 open-heart surgery patients, C-reactive protein (CRP) serum concentrations were measured before and on the third day after surgery. There was no correlation between levels of CRP and the development of postoperative AF. All 1,419 patients with no history of AF, undergoing primary aortocoronary bypass surgery (CABG) in the years 1997–2000 were followed up after 8.0 years. The mortality rate was 191 deaths/1,000 patients (19.1%) in patients with no AF and 140 deaths/419 patients (33.4%) in patients with postoperative AF. Postoperative AF was an age-independent risk factor for late mortality, with a hazard ratio (HR) of 1.56 (95% CI 1.23–1.98). Postoperative AF patients had a more than doubled risk of death due to cerebral ischaemia, myocardial infarction, sudden death, and heart failure compared with patients without AF. All 571 consecutive patients undergoing primary CABG during the years 1999–2000 were followed-up after 6 years. Questionnaires were obtained from 91.6% of surviving patients and an electrocardiogram (ECG) from 88.3% of all patients. In postoperative AF patients, 14.1% had AF at follow-up, compared with 2.8% of patients with no AF at surgery (p<.001). An episode of postoperative AF was found to be an independent risk factor for development of late AF, with an adjusted risk ratio (RR) of 3.11 (95% CI 1.41–6.87). Epicardial microwave ablation was performed in 20 open-heart surgery patients with concomitant AF. Transthoracic echocardiography was performed preoperatively and at 6 months postoperatively. At 12 months postoperatively 14/19 patients (74%) were in SR with no anti-arrhythmic drugs. All patients in SR had preserved left and right atrial filling waves (A-waves) and Tissue velocity echocardiography (TVE) showed preserved atrial wall velocities and atrial strain. In conclusion, postoperative AF is an independent risk factor for late mortality and later development of AF. There is no correlation between the inflammatory marker CRP and postoperative AF. Epicardial microwave ablation of concomitant AF results in SR in the majority of patients and seems to preserve atrial mechanical function.
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| 42. |
- Ahlsson, Anders, et al.
(författare)
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Atrial function after epicardial microwave ablation in patients with atrial fibrillation
- 2008
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Ingår i: Scandinavian Cardiovascular Journal. - : Taylor & Francis. - 1401-7431 .- 1651-2006. ; 42:3, s. 192-201
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To study epicardial microwave ablation of concomitant atrial fibrillation and its effects on heart rhythm and atrial function during follow-up. DESIGN: The study included 20 open-heart surgery patients with concomitant atrial fibrillation. Transthoracic echocardiography with flow and tissue Doppler recordings was performed preoperatively and at 6 months postoperatively. Blood samples were obtained preoperatively and postoperatively for analysis of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and amino terminal precursor of brain natriuretic peptide (NT-proBNP). RESULTS: Fourteen of 19 patients (74%) were in sinus rhythm with no antiarrhythmic drugs at 12 months. All patients in sinus rhythm had preserved left and right atrial-filling waves through atrioventricular valves during atrial contraction. Tissue velocity echocardiography on patients in sinus rhythm showed preserved atrial wall velocities, atrial strain, and atrial strain rate. Levels of natriuretic peptides tended to decrease in patients with stable sinus rhythm at one year compared to patients in atrial fibrillation. CONCLUSIONS: Epicardial microwave ablation results in sinus rhythm in a majority of patients and seems to preserve atrial mechanical function
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| 43. |
- Ahlsson, Anders J., et al.
(författare)
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Postoperative atrial fibrillation is not correlated to C-reactive protein
- 2007
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Ingår i: Annals of Thoracic Surgery. - : Elsevier BV. - 0003-4975 .- 1552-6259. ; 83:4, s. 1332-1337
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The peak incidence of postoperative atrial fibrillation (AF) occurs around the second postoperative day, a time at which serum inflammatory markers are elevated. The aim of this study was to investigate differences between patients with and without postoperative AF with special regard to C-reactive protein (CRP) serum levels. METHODS: The study cohort included all heart surgery patients who had sinus rhythm preoperatively, survived postoperative day 3, and were operated on between July 1, 2004, and June 30, 2005 (n = 524). Any episode of AF during the first 7 postoperative days defined the patient as belonging to the postoperative AF group. Creatine kinase-myocardial band (CK-MB) was measured at postoperative day 1, and CRP was measured preoperatively and at postoperative day 3. Risk factors for postoperative AF were determined using bivariate and multivariate regression analysis. RESULTS: Of 524 patients, 182 had at least one episode of AF (34.7%). Preoperative and postoperative CRP concentrations did not differ between the groups (postoperative CRP 175.4 +/- 64.4 versus 175.3 +/- 60.1 mg/L respectively, p = 0.99). Atrial fibrillation patients were significantly older (p < 0.001) and had higher CK-MB levels (33.6 +/- 53.1 microg/L versus 22.5 +/- 26.7 microg/L, respectively, p = 0.009). The odds ratio for postoperative AF with postoperative CK-MB greater than 70 microg/L was 3.5 (confidence interval: 1.4 to 8.6). CONCLUSIONS: Postoperative AF has no correlation to the inflammatory marker CRP in heart surgery patients. Ischemic myocardial injury might predispose for postoperative AF.
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| 44. |
- Ahlsson, Anders, 1962-, et al.
(författare)
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Patients with postoperative atrial fibrillation have a doubled cardiovascular mortality
- 2009
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Ingår i: Scandinavian cardiovascular journal : SCJ. - : Informa UK Limited. - 1651-2006 .- 1401-7431. ; 43:5, s. 330-336
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate the impact of postoperative AF on late mortality and cause of death in CABG patients.DESIGN: All CABG patients without preoperative AF surgically treated between January 1, 1997 and June 30, 2000 were included (N = 1419). Altogether, 419 patients (29.5%) developed postoperative AF. After a median follow-up of 8.0 years, survival data were obtained, causes of death were compared and Cox proportional hazard analysis was used to determine predictors of late mortality.RESULTS: The total mortality was 140 deaths/419 patients (33.4%) in postoperative AF patients and 191 deaths/1 000 patients (19.1%) in patients without AF. Death due to cerebral ischemia (2.6% vs. 0.5%), myocardial infarction (7.4% vs. 3.0%), sudden death (2.6% vs. 0.9%), and heart failure (6.7% vs. 2.7%) was more common among postoperative AF patients. Postoperative AF was an age-independent risk indicator for late mortality with a hazard ratio (HR) of 1.56 (95% confidence interval 1.23-1.98).CONCLUSIONS: Postoperative AF is an age-independent risk factor for late mortality in CABG patients, explained by an increased risk of cardiovascular death.
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| 45. |
- Ahlström, Anders, 1973-
(författare)
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Aerolastic simulation of wind turbine dynamics
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work in this thesis deals with the development of an aeroelastic simulation tool for horizontal axis wind turbine applications. Horizontal axis wind turbines can experience significant time varying aerodynamic loads, potentially causing adverse effects on structures, mechanical components, and power production. The needs for computational and experimental procedures for investigating aeroelastic stability and dynamic response have increased as wind turbines become lighter and more flexible. A finite element model for simulation of the dynamic response of horizontal axis wind turbines has been developed. The developed model uses the commercial finite element system MSC.Marc, focused on nonlinear design and analysis, to predict the structural response. The aerodynamic model, used to transform the wind flow field to loads on the blades, is a Blade-Element/Momentum model. The aerodynamic code is developed by The Swedish Defence Research Agency (FOI, previously named FFA) and is a state-of-the-art code incorporating a number of extensions to the Blade-Element/Momentum formulation. The software SOSIS-W, developed by Teknikgruppen AB was used to generate wind time series for modelling different wind conditions. The method is general, and different configurations of the structural model and various type of wind conditions can be simulated. The model is primarily intended for use as a research tool when influences of specific dynamic effects are investigated. Verification results are presented and discussed for an extensively tested Danwin 180 kW stall-controlled wind turbine. Code predictions of mechanical loads, fatigue and spectral properties, obtained at different conditions, have been compared with measurements. A comparison is also made between measured and calculated loads for the Tjæreborg 2 MW wind turbine during emergency braking of the rotor. The simulated results correspond well to measured data.
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| 46. |
- Ahnesjö, Anders, et al.
(författare)
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Application of the convolution method for calculation of output factors for therapy photon beams
- 1992
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Ingår i: Medical Physics. - : Wiley. - 0094-2405. ; 19:2, s. 295-301
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Tidskriftsartikel (refereegranskat)abstract
- The output factor for a therapy photon beam is defined as the dose per monitor unit relative to the dose per monitor unit in a reference field. Convolution models for photon dose calculations yield the dose in units normalized to the incident energy fluence with phantom scatter intrinsically modeled. Output factors calculated with the convolution method as the dose per unit energy fluence relative to the calculated dose per unit energy fluence in a reference field could deviate as much as 5% if corrections are not made for perturbations due to treatment head scatter. Significant perturbations are particles backscattered from the collimators to the monitor and photons forward scattered from the filter and collimators in the treatment head. The forward scatter adds an "unmonitored" contribution to the total energy fluence of the beam. A model is developed that describes the field size dependence of these perturbations for conversion of output factors, calculated with the convolution method, to machine output factors as an integrated part in treatment planning. The necessary machine characteristics are derived from measurements of the output in air for a limited set of field sizes. The method has been tested using five different multileaf collimated irregular fields at 6 MV and for a large set of rectangular fields at 5, 6, and 18 MV and found to predict output factors with an accuracy better than 1%.
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| 47. |
- Ahnesjö, Anders, et al.
(författare)
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Beam modeling and verification of a photon beam multisource model.
- 2005
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Ingår i: Medical Physics. - : Wiley. - 0094-2405. ; 32:6, s. 1722-37
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Tidskriftsartikel (refereegranskat)abstract
- Dose calculations for treatment planning of photon beam radiotherapy require a model of the beam to drive the dose calculation models. The beam shaping process involves scattering and filtering that yield radiation components which vary with collimator settings. The necessity to model these components has motivated the development of multisource beam models. We describe and evaluate clinical photon beam modeling based on multisource models, including lateral beam quality variations. The evaluation is based on user data for a pencil kernel algorithm and a point kernel algorithm (collapsed cone) used in the clinical treatment planning systems Helax-TMS and Nucletron-Oncentra. The pencil kernel implementations treat the beam spectrum as lateral invariant while the collapsed cone involves off axis softening of the spectrum. Both algorithms include modeling of head scatter components. The parameters of the beam model are derived from measured beam data in a semiautomatic process called RDH (radiation data handling) that, in sequential steps, minimizes the deviations in calculated dose versus the measured data. The RDH procedure is reviewed and the results of processing data from a large number of treatment units are analyzed for the two dose calculation algorithms. The results for both algorithms are similar, with slightly better results for the collapsed cone implementations. For open beams, 87% of the machines have maximum errors less than 2.5%. For wedged beams the errors were found to increase with increasing wedge angle. Internal, motorized wedges did yield slightly larger errors than external wedges. These results reflect the increased complexity, both experimentally and computationally, when wedges are used compared to open beams.
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| 48. |
- Ahnesjö, Anders, et al.
(författare)
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The IMRT information process-mastering the degrees of freedom in external beam therapy
- 2006
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Ingår i: Physics in Medicine and Biology. - 0031-9155 .- 1361-6560. ; 51:13, s. R381-402
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Tidskriftsartikel (refereegranskat)abstract
- The techniques and procedures for intensity-modulated radiation therapy (IMRT) are reviewed in the context of the information process central to treatment planning and delivery of IMRT. A presentation is given of the evolution of the information based radiotherapy workflow and dose delivery techniques, as well as the volume and planning concepts for relating the dose information to image based patient representations. The formulation of the dose shaping process as an optimization problem is described. The different steps in the calculation flow for determination of machine parameters for dose delivery are described starting from the formulation of optimization objectives over dose calculation to optimization procedures. Finally, the main elements of the quality assurance procedure necessary for implementing IMRT clinically are reviewed.
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| 49. |
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| 50. |
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