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- Angelsmark, Ola, 1972-
(författare)
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Constructing Algorithms for Constraint Satisfaction and Related Problems : Methods and Applications
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we will discuss the construction of algorithms for solving Constraint Satisfaction Problems (CSPs), and describe two new ways of approaching them. Both approaches are based on the idea that it is sometimes faster to solve a large number of restricted problems than a single, large, problem. One of the strong points of these methods is that the intuition behind them is fairly simple, which is a definite advantage over many techniques currently in use.The first method, the covering method, can be described as follows: We want to solve a CSP with n variables, each having a domain with d elements. We have access to an algorithm which solves problems where the domain has size e < d, and we want to cover the original problem using a number of restricted instances, in such a way that the solution set is preserved. There are two ways of doing this, depending on the amount of work we are willing to invest; either we construct an explicit covering and end up with a deterministic algorithm for the problem, or we use a probabilistic reasoning and end up with a probabilistic algorithm.The second method, called the partitioning method, relaxes the demand on the underlying algorithm. Instead of having a single algorithm for solving problems with domain less than d, we allow an arbitrary number of them, each solving the problem for a different domain size. Thus by splitting, or partitioning, the domain of the large problem, we again solve a large number of smaller problems before arriving at a solution.Armed with these new techniques, we study a number of different problems; the decision problems (d, l)-CSP and k-Colourability, together with their counting counterparts, as well as the optimisation problems Max Ind CSP, Max Value CSP, Max CSP, and Max Hamming CSP. Among the results, we find a very fast, polynomial space algorithm for determining k-colourability of graphs.
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| 2. |
- Fernebro, Josefin, et al.
(författare)
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Focus on the tumor periphery in MRI evaluation of soft tissue sarcoma: infiltrative growth signifies poor prognosis
- 2006
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Ingår i: Sarcoma. - 1357-714X. ; 2006, s. 21251-21251
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. Infiltrative microscopical peripheral growth of soft tissue sarcomas (STS) has been shown to be of prognostic importance and preoperative risk stratification could individualize neoadjuvant treatment. Patients and methods. We assessed peripheral tumour growth pattern on preoperative MRI from 78 STS. The findings were correlated to histopathology and to outcome. Results. The MRI-based peripheral tumour growth pattern was classified as pushing in 34 tumours, focally infiltrative in 25, and diffusely infiltrative in 19. All tumours with diffuse infiltration on MRI also showed microscopical infiltration, whereas MRI failed to identify infiltration in two-thirds of the microscopically infiltrative tumours. Diffusely infiltrative growth on MRI gave a 2.5 times increased risk of metastases (P = .01) and a 3.7 times higher risk of local recurrence (P = .02). Discussion. Based on this observation we suggest that MRI evaluation of STS should focus on the peripheral tumour growth pattern since it adds prognostic information of value for decisions on neoadjuvant therapies.
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| 3. |
- Guenard, Guillaume, et al.
(författare)
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Comparison between activity estimates obtained using bioenergetic and behavioural analyses
- 2008
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X .- 1205-7533. ; 65:8, s. 1705-1720
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Tidskriftsartikel (refereegranskat)abstract
- Activity rate of Arctic char (Salvelinus alpinus) held in 90 m2 littoral enclosures were estimated using bioenergetic (with consumption estimated using stable caesium, 133Cs) and behavioural approaches (with fish movements quantified using video cameras). We found no statistically significant difference between values of activity rate obtained using the two approaches for three of the six experiments we performed. However, there was no relationship between estimates of activity rate obtained using the two approaches. Discrepancies may arise from the difficulty to meet assumptions regarding the temporal stability of the concentration of 133Cs in fish diet and of the assimilation coefficient of this tracer. When fish remain in an area where their behaviour can be well described (e.g., enclosure, habitat patches of littoral zones, coral reefs), the behavioural approach appears more robust to estimate activity rate because it depends most on a variable that is easiest to estimate (the number of movements performed). When these conditions are not met (low fish densities or major fish migrations), a reliable assessment of the concentration and assimilation of 133Cs in stomach contents appears critical to implement the bioenergetic approach based on this tracer.
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| 4. |
- Johansson, Torsten, et al.
(författare)
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The total costs of a displaced femoral neck fracture: comparison of internal fixation and total hip replacement. A randomised study of 146 hips
- 2006
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Ingår i: International Orthopaedics. - : Springer Science and Business Media LLC. - 0341-2695 .- 1432-5195. ; 30:1, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- We randomised 143 patients –age 75 years or older–with displaced femoral neck fracture to either internal fixation or total hip replacement (THR) and compared the socio-economic consequences. In the internal fixation group, 34 of 78 hips underwent secondary surgery. In the THR group, 12 of 68 hips dislocated, the majority in mentally impaired patients. We calculated the total hospital costs for two years after operation. When secondary surgery was included, there was no difference in costs between the internal fixation and THR groups, or between the mentally impaired and lucid subgroups. The costs to the community were calculated comparing the baseline cost before surgery with the average cost per month during the first postoperative year. No difference was found between the treatment groups. The Harris hip scores were higher in the THR group, and pain was more common in the internal fixation group. In lucid patients, THR gives a better clinical result at the same cost.
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| 6. |
- Jonsson, Asa C, et al.
(författare)
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Tinted contact lenses in Bothnia dystrophy.
- 2007
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Ingår i: Acta Ophthalmologica Scandinavica. - : Wiley. - 1395-3907 .- 1600-0420. ; 85:5, s. 534-539
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To determine whether tinted contact lenses can improve visual function in patients with Bothnia dystrophy (BD), a genetically defined retinal dystrophy with prolonged dark adaptation. METHODS: Twelve patients with BD were fitted with the same type of soft contact lenses tinted dark brown. Visual acuity (VA), contrast vision, near vision and visual fields were tested before and 1 month after contact lens fitting. The patients completed a visual function questionnaire. The physical properties of the contact lenses were tested using spectrophotometry. RESULTS: The patients with the lowest VA described the most obvious improvement in visual function. This group of patients preferred darker contact lenses and continued wearing their contact lenses after the study ended. The patients with the best VA preferred lighter contact lenses and a few patients in this group discontinued contact lens wear upon completion of the study. CONCLUSIONS: Visual function in BD patients was improved by dark tinted contact lenses. The optimal colour for lenses varies, depending on the season and the individual. Other patient groups with retinal dystrophies associated with prolonged dark adaptation or dysfunction of the cone system, such as cone dystrophies or achromatopsia, may also benefit from this type of contact lens.
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| 7. |
- Jonsson, Cecilia, 1974-
(författare)
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Frivilligorganisationer i en organisatorisk glesbygd : En studie av socialt inriktade frivilligorganisationers uppkomst och etablering i en kommunal kontext
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The landscape of socially oriented NGOs – a study of how they are created and established in a local Swedish context. This thesis is an inquiry into local, socially oriented non-governmental organizations (NGOs) in Swedish municipalities. Previous research has indicated that changes in the monitoring and steering of financial support during the 1990s altered the conditions for and practices of NGOs. The inquiry – based on archival material and interviews with organization representatives from the twelve NGOs receiving financial support from the social welfare board in Växjö municipality – showed instead that the organizations were unaffected by the hanges, and that the set of recipient organizations had been stable over time. A comparison with four other communities reveals that the same pattern is repeated in other municipalities of similar size. The purpose of the thesis is to develop a theoretical framework to account for stability in sets of recipient organizations. It is argued that set stability is explained by affiliations with well-known national organizations, in conjunction with the boundary-work of the local organizations.
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