| 1. |
- Gustavsson, Anders, et al.
(författare)
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Long-term colectomy rate after intensive intravenous corticosteroid therapy for ulcerative colitis prior to the immunosuppressive treatment era
- 2007
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Ingår i: American Journal of Gastroenterology. - New York : American College of Gastroenterology. - 0002-9270 .- 1572-0241. ; 102:11, s. 2513-2519
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Corticosteroids are a cornerstone in the treatment of a severe attack of ulcerative colitis (UC). The long-term prognosis in this patient group is not well described. We studied the long-term colectomy and relapse rates in patients given intensive intravenous corticosteroid treatment (IIVT) for acute UC. METHODS: A retrospective clinical study of 158 patients with UC treated in 1975-1982 with IIVT. Patients were followed-up to death, colectomy or last visit. RESULTS: A total of 11 patients were excluded due to change of diagnosis (N = 10) or lost to follow-up (N = 1). The indication for index IIVT in the remaining 147 patients was a severe attack (N = 61), a moderately severe attack (N = 45), a mild attack (N = 29) or chronic continuous disease (N = 12). The median (range) duration of follow-up was 173 (4-271) months in patients escaping colectomy during the first 3 months. Three months after IIVT, the colectomy rates were 28/61 (46%) in a severe attack, 4/45 (9%) in a moderately severe, and 1/29 (3%) in a mild attack. After 10 yr, the colectomy rates were 39/61 (64%), 22/45 (49%), and 8/29 (28%), respectively. During follow-up, neither colectomy incidence beyond 3 months, time to first relapse nor relapse incidence was influenced by severity of initial attack, except for a lower relapse incidence after a severe attack. CONCLUSIONS: In patients escaping colectomy during the first 3 months after IIVT, the future prognosis was similar irrespective of initial disease severity.
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| 2. |
- Shiriaev, Anton, et al.
(författare)
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Virtual-Holonomic-Constraints-Based Design of Stable Oscillations of Furuta Pendulum: Theory and Experiments
- 2007
-
Ingår i: IEEE Transactions on Robotics. - 1941-0468 .- 1552-3098. ; 23:4, s. 827-832
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Tidskriftsartikel (refereegranskat)abstract
- The Furuta pendulum consists of an arm rotating in the horizontal plane and a pendulum attached to its end. Rotation of the arm is controlled by a DC motor, while the pendulum is moving freely in the plane, orthogonal to the arm. Motivated, in particular, by possible applications for walking/running/balancing robots, we consider the Furuta pendulum as a system for which synchronized periodic motions of all the generalized coordinates are to be created and stabilized. The goal is to achieve, via appropriate feedback control action, orbitally exponentially stable oscillations of the pendulum of various shapes around its upright and downward positions, accompanied with oscillations of the arm. Our approach is based on the idea of stabilization of a particular virtual holonomic constraint imposed on the configuration coordinates, which has been theoretically developed recently. Here, we elaborate on the complete design procedure. The results are illustrated not only through numerical simulations but also through successful experimental tests.
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| 3. |
- Arnell, Anders, et al.
(författare)
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Naturvägledning i Sverige - en översikt
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Naturvägledning handlar om att förmedla kunskap om och väcka känslor för naturen och kulturlandskapet. Naturvägledare finns i många verksamheter och kallas ofta för något annat i sin vardag: naturguide, museipedagog, ekoturismföretagare, naturinformatör. Centrum för naturvägledning presenterar i rapporten Naturvägledning i Sverige en bred översikt över begrepp, historik, och pågående aktiviteter inom svensk naturvägledning, med en internationell utblick. Rapporten bygger bland annat på intervjuer och enkäter med cirka 100 personer, som ger sin bilder av mål, glädjeämnen och utmaningar med arbetet som naturvägledare.
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| 4. |
- Bergquist, Annika, et al.
(författare)
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Increased risk of primary sclerosing cholangitis and ulcerative colitis in first-degree relatives of patients with primary sclerosing cholangitis
- 2008
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Ingår i: Clinical Gastroenterology and Hepatology. - New York : Elsevier. - 1542-3565 .- 1542-7714. ; 6:8, s. 939-943
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: The importance of genetic factors for the development of primary sclerosing cholangitis (PSC) is incompletely understood. This study assessed the risk of PSC and inflammatory bowel disease (IBD) among first-degree relatives of patients with PSC, compared with the first-degree relatives of a cohort without PSC. Methods: Subjects from the national Swedish cohort of PSC patients (n = 678) were matched for date of birth, sex, and region to up to 10 subjects without a diagnosis of PSC (n = 6347). Linkage through general population registers identified first-degree relatives of subjects in both the PSC and comparison cohorts (n = 34,092). Diagnoses among first-degree relatives were identified by using the Inpatient Register. Results: The risk of cholangitis was statistically significantly increased in offspring, siblings, and parents of the PSC patient cohort, compared with relatives of the comparison cohort, with the hazard ratios and 95% confidence intervals, 11.5 (1.6–84.4), 11.1 (3.3–37.8), and 2.3 (0.9–6.1), respectively. The hazard ratios for ulcerative colitis (UC) among first-degree relatives of all PSC patients was 3.3 (2.3–4.9) and for Crohn's disease 1.4 (0.8–2.5). The risk of UC for relatives of PSC patients without IBD was also increased, 7.4 (2.9–18.9). Conclusions: First-degree relatives of patients with PSC run an increased risk of PSC, indicating the importance of genetic factors in the etiology of PSC. First-degree relatives of PSC patients without IBD are also at an increased risk of UC, which might indicate shared genetic susceptibility factors for PSC and UC.
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| 5. |
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| 6. |
- Carlsson, Jesper, 1976-, et al.
(författare)
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Symplectic Pontryagin Approximations for Optimal Design
- 2009
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Ingår i: Mathematical Modelling and Numerical Analysis. - : EDP Sciences. - 0764-583X .- 1290-3841. ; 43:1, s. 3-32
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Tidskriftsartikel (refereegranskat)abstract
- The powerful Hamilton-Jacobi theory is used for constructing regularizations and error estimates for optimal design problems. The constructed Pontryagin method is a simple and general method for optimal design and reconstruction: the first, analytical, step is to regularize the Hamiltonian; next the solution to its stationary Hamiltonian system, a nonlinear partial differential equation, is computed with the Newton method. The method is efficient for designs where the Hamiltonian function can be explicitly formulated and when the Jacobian is sparse, but becomes impractical otherwise (e.g. for non local control constraints). An error estimate for the difference between exact and approximate objective functions is derived, depending only on the difference of the Hamiltonian and its finite dimensional regularization along the solution path and its L 2 projection, i.e. not on the difference of the exact and approximate solutions to the Hamiltonian systems.
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| 7. |
- Chen, DeJiu, et al.
(författare)
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Modelling Support for Design of Safety-Critical Automotive Embedded Systems
- 2008
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Ingår i: Proceedings of the 27th International Conference on Computer Safety, Reliability and Security, 2008.. - Berlin, Heidelberg : Springer Berlin Heidelberg.
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Konferensbidrag (refereegranskat)abstract
- This paper describes and demonstrates an approach that promises to bridge the gap between model-based systems engineering and the safety process of automotive embedded systems. The basis for this is the integration of safety analysis techniques, a method for developing and managing Safety Cases, and a systematic approach to model-based engineering - the EAST-ADL2 architecture description language. Three areas are highlighted: (I) System model development on different levels of abstraction. This enables fulfilling many requirements on software development as specified by ISO-CD-26262 (2) Safety Case development in close connection to the system model (3) Analysis of mal-functional behaviour that may cause hazards, by modelling of errors and error propagation in a (complex and hierarchical) system model.
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| 8. |
- de Magalhaes, J P, et al.
(författare)
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Cognitive aging as an extension of brain development : A model linking learning, brain plasticity, and neurodegeneration
- 2005
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Ingår i: Mechanisms of Ageing and Development. - : Elsevier BV. - 0047-6374 .- 1872-6216. ; 126:10, s. 1026-1033
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Forskningsöversikt (refereegranskat)abstract
- Differences in cognitive aging rates among mammals suggest that the pace of brain aging is genetically determined. In this work, we investigate the possibility that brain aging is an extension of brain development. It is possible that a subset of developmental mechanisms are extreme cases of antagonistic pleiotropy in that they are necessary for reaching adulthood and yet later cause age-related diseases. We derive a model linking development and brain aging in which childhood events essential for brain development later result in neurodegeneration. The hypothesis presented herein involves brain plasticity in which the same mechanisms that shape the adult phenotype continue at later ages contributing to cognitive dysfunction and eventually dementia. The same genetic program that decreases brain plasticity at early ages to focus our mind to the surrounding environment may continue in adulthood resulting in cognitive aging. Experimental implications for understanding neurodegeneration in this context are also discussed. (c) 2005 Elsevier Ireland Ltd. All rights reserved.
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| 9. |
- Elmberg, Maria, et al.
(författare)
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Increased Mortality Risk in Patients With Phenotypic Hereditary Hemochromatosis But Not in Their First-Degree Relatives
- 2009
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Ingår i: Gastroenterology. - : Elsevier BV. - 0016-5085 .- 1528-0012. ; 137:4, s. 1301-1309
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND & AIMS: Hereditary hemochromatosis (HH) is an autosomal-recessive disorder characterized by iron overload. Relatives of HH patients were screened and those with HH-associated mutations and an increased iron load were identified. However, little is known about their mortality or strategies for their management. We assessed mortality among Swedish patients with HH and their first-degree relatives using health and census registers. METHODS: We performed a matched population-based cohort study of 3832 patients with HH and their 14,496 first-degree relatives using data collected from 1990 through 2007. Mortality data from these groups were compared with that of 38,969 population controls and their 143,349 first-degree relatives using Cox regression analyses. RESULTS: Patients identified on the basis of hospitalization with HH had an increased risk (relative risk [RR]) for death (RR, 2.45; 95% confidence interval [CI], 2.27-2.64; 857 deaths). Patients identified through other means had a mortality risk that was lower than those identified in the hospital but higher than controls (RR, 1.15; 95% CI, 1.00-1.33; 216 deaths). Their first-degree relatives had only a marginally increased mortality risk (RR, 1.05; 95% CI, 1.01-1.10); this RR was similar to that of patients' spouses (RR, 1.09; 95% CI, 0.86-1.38; 82 deaths). Patients with HH who also had a family history of HH did not have an increased mortality risk compared with other groups (RR, 1.05; 95% CI 0.67-1.62; 21 deaths). CONCLUSIONS: Patients with HH have a modestly increased mortality risk compared with controls. The mortality of relatives is increased marginally compared with controls, and is similar among biological and nonbiological relatives.
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| 10. |
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| 11. |
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| 12. |
- Gustafsson, Mats, et al.
(författare)
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Effekter av vinterdäck : en kunskapsöversikt
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Choice of winter tyres has, from mainly being a matter of safety and economic costs for wearing of road pavements, during later years also become a matter of inhalable particles formed during pavement wear from studded tyres and their negative effects on public health. Further, the tyres' effects on environment and noise have been illustrated in several studies. The issue is also complicated by the fact that tyre choice effects on traffic safety have several components, including such diverging parameters as friction and behaviour. Finally all aspects have to be evaluated from a socioeconomic point of view for society to be able to decide which kind of distribution of tyre types that is the most profitable. This report is a summary of current knowledge in this complex research field.
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| 13. |
- Hennig, Janosch, et al.
(författare)
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The fellowship of the RING: The RING-B-box linker region (RBL) interacts with the RING in TRIM21/Ro52, contributes to an autoantigenic epitope in Sjögren's syndrome, and is an integral and conserved region in TRIM proteins
- 2008
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 377:2, s. 431-449
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Tidskriftsartikel (refereegranskat)abstract
- Ro52 is a major autoantigen that is targeted in the autoimmune disease Sjögren syndrome and belongs to the tripartite motif (TRIM) protein family. Disease-related antigenic epitopes are mainly found in the coiled-coil domain of Ro52, but one such epitope is located in the Zn2+-binding region, which comprises an N-terminal RING followed by a B-box, separated by a ∼40-residue linker peptide. In the present study, we extend the structural, biophysical, and immunological knowledge of this RING-B-box linker (RBL) by employing an array of methods. Our bioinformatic investigations show that the RBL sequence motif is unique to TRIM proteins and can be classified into three distinct subtypes. The RBL regions of all three subtypes are as conserved as their known flanking domains, and all are predicted to comprise an amphipathic helix. This helix formation is confirmed by circular dichroism spectroscopy and is dependent on the presence of the RING. Immunological studies show that the RBL is part of a conformation-dependent epitope, and its antigenicity is likewise dependent on a structured RING domain. Recombinant Ro52 RING-RBL exists as a monomer in vitro, and binding of two Zn2+ increases its stability. Regions stabilized by Zn2+ binding are identified by limited proteolysis and matrix-assisted laser desorption/ionization mass spectrometry. Furthermore, the residues of the RING and linker that interact with each other are identified by analysis of protection patterns, which, together with bioinformatic and biophysical data, enabled us to propose a structural model of the RING-RBL based on modeling and docking experiments. Sequence similarities and evolutionary sequence patterns suggest that the results obtained from Ro52 are extendable to the entire TRIM protein family.
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| 14. |
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| 15. |
- Johansson, Denny, 1980, et al.
(författare)
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Protein autoproteolysis: conformational strain linked to the rate of peptide cleavage by the pH dependence of the N --> O acyl shift reaction.
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 131:27, s. 9475-7
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Tidskriftsartikel (refereegranskat)abstract
- Nucleophilic attack by a side chain nucleophile on the adjacent peptide bond followed by N --> O or N --> S acyl shift is the primary step in protein autoproteolysis. Precursor structures of autoproteolytic proteins reveal strained (or twisted) amides at the site of cleavage, and we previously showed that SEA domain autoproteolysis involves substrate destabilization by approximately 7 kcal/mol. However, the precise chemical mechanism by which conformational energy is converted into reaction rate acceleration has not been understood. Here we show that the pH dependence of autoproteolysis in a slow-cleaving mutant (1G) of the MUC1 SEA domain is consistent with a mechanism in which N --> O acyl shift proceeds after initial protonation of the amide nitrogen. Unstrained amides have pK(a) values of 0 with protonation on the oxygen, and autoproteolysis is therefore immeasurably slow at neutral pH. However, conformational strain forces the peptide nitrogen into a pyramidal conformation with a significantly increased pK(a) for protonation. We find that pK(a) values of approximately 4 and approximately 6, as in model compounds of twisted amides, reproduce the rate of autoproteolysis in the 1G and wild-type SEA domains, respectively. A mechanism involving strain, nitrogen protonation, and N --> O shift is also supported by quantum-chemical calculations. Such a reaction therefore constitutes an alternative to peptide cleavage that is utilized in autoproteolysis, as opposed to a classical mechanism involving a structurally conserved active site with a catalytic triad and an oxyanion hole, which are not present at the SEA domain cleavage site.
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| 16. |
- Lindkvist, Annica, et al.
(författare)
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Reduction of the HIV-1 reservoir in resting CD4+ T-lymphocytes by high dosage intravenous immunoglobulin treatment: a proof-of-concept study
- 2009
-
Ingår i: AIDS research and therapy. - : Springer Science and Business Media LLC. - 1742-6405. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The latency of HIV-1 in resting CD4+ T-lymphocytes constitutes a major obstacle for the eradication of virus in patients on antiretroviral therapy (ART). As yet, no approach to reduce this viral reservoir has proven effective. METHODS: Nine subjects on effective ART were included in the study and treated with high dosage intravenous immunoglobulin (IVIG) for five consecutive days. Seven of those had detectable levels of replication-competent virus in the latent reservoir and were thus possible to evaluate. Highly purified resting memory CD4+ T-cells were activated and cells containing replication-competent HIV-1 were quantified. HIV-1 from plasma and activated memory CD4+ T-cells were compared with single genome sequencing (SGS) of the gag region. T-lymphocyte activation markers and serum interleukins were measured. RESULTS: The latent HIV-1 pool decreased with in median 68% after IVIG was added to effective ART. The reservoir decreased in five, whereas no decrease was found in two subjects with detectable virus. Plasma HIV-1 RNA >or= 2 copies/mL was detected in five of seven subjects at baseline, but in only one at follow-up after 8-12 weeks. The decrease of the latent HIV-1 pool and the residual plasma viremia was preceded by a transitory low-level increase in plasma HIV-1 RNA and serum interleukin 7 (IL-7) levels, and followed by an expansion of T regulatory cells. The magnitude of the viral increase in plasma correlated to the size of the latent HIV-1 pool and SGS of the gag region showed that viral clones from plasma clustered together with virus from activated memory T-cells, pointing to the latent reservoir as the source of HIV-1 RNA in plasma. CONCLUSION: The findings from this uncontrolled proof-of-concept study suggest that the reservoir became accessible by IVIG treatment through activation of HIV-1 gene expression in latently-infected resting CD4+ T-cells. We propose that IVIG should be further evaluated as an adjuvant to effective ART.
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| 17. |
- Macao, Bertil, 1969, et al.
(författare)
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Recombinant amyloid beta-peptide production by coexpression with an affibody ligand.
- 2008
-
Ingår i: BMC biotechnology. - : Springer Science and Business Media LLC. - 1472-6750. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Oligomeric and fibrillar aggregates of the amyloid beta-peptide (Abeta) have been implicated in the pathogenesis of Alzheimer's disease (AD). The characterization of Abeta assemblies is essential for the elucidation of the mechanisms of Abeta neurotoxicity, but requires large quantities of pure peptide. Here we describe a novel approach to the recombinant production of Abeta. The method is based on the coexpression of the affibody protein ZAbeta3, a selected affinity ligand derived from the Z domain three-helix bundle scaffold. ZAbeta3 binds to the amyloidogenic central and C-terminal part of Abeta with nanomolar affinity and consequently inhibits aggregation. RESULTS: Coexpression of ZAbeta3 affords the overexpression of both major Abeta isoforms, Abeta(1-40) and Abeta(1-42), yielding 4 or 3 mg, respectively, of pure 15N-labeled peptide per liter of culture. The method does not rely on a protein-fusion or -tag and thus does not require a cleavage reaction. The purified peptides were characterized by NMR, circular dichroism, SDS-PAGE and size exclusion chromatography, and their aggregation propensities were assessed by thioflavin T fluorescence and electron microscopy. The data coincide with those reported previously for monomeric, largely unstructured Abeta. ZAbeta3 coexpression moreover permits the recombinant production of Abeta(1-42) carrying the Arctic (E22G) mutation, which causes early onset familial AD. Abeta(1-42)E22G is obtained in predominantly monomeric form and suitable, e.g., for NMR studies. CONCLUSION: The coexpression of an engineered aggregation-inhibiting binding protein offers a novel route to the recombinant production of amyloidogenic Abeta peptides that can be advantageously employed to study the molecular basis of AD. The presented expression system is the first for which expression and purification of the aggregation-prone Arctic variant (E22G) of Abeta(1-42) is reported.
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| 18. |
- Neuman, Magnus, et al.
(författare)
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Modelling and Control of Series HEVs Including Resistive Losses and Varying Engine Efficiency
- 2009
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Ingår i: Proceedings of SAE 2009 World Congress. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
-
Konferensbidrag (refereegranskat)abstract
- A model of a series HEV (Hybrid Electric Vehicle) including resistive losses in the energy storage and varying engine and generator efficiency is presented. The purpose is to study how system properties affect the optimal control of series HEVs. We show that there is an inherent trade-off in the control of such a system, based on the characteristics of the efficiency curve of the EGU (Engine and Generator Unit) together with the energy storage internal resistance, capacitance and energy level. The relation between these properties determines the optimal control of the EGU, and this is thus the mechanism behind all optimal control problems using a similar model setup. We illustrate our reasoning using deterministic dynamic programming where system properties are varied and the optimal control is studied.
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| 19. |
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| 20. |
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| 21. |
- Sandberg, Anders, et al.
(författare)
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An autocatalytic model of STDP timing from slow calcium-dependent signals
- 2005
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Ingår i: Neurocomputing. - : Elsevier BV. - 0925-2312 .- 1872-8286. ; 65-66, s. 603-608
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Tidskriftsartikel (refereegranskat)abstract
- Data of spike timing-dependent plasticity (STDP) show a sharp temporal transition between potentiation and depression despite a relatively slow time course of calcium concentration. We show how autocatalytic amplification of initial concentration differences can enable a high degree of temporal selectivity and produce the sharp STDP weight change curve despite having a relatively slow time constant. This simple model is robust to parameter changes, noise and details of the model. The model correctly predicts the location of the maximum and minimum for STDP at +/- 10ms from coincidence.
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| 22. |
- Sandberg, Anders, et al.
(författare)
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Deterministic target selection : setting requirements on speed and yaw rate in automotive sensor systems
- 2008
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Ingår i: Proc. of 26th International System Safety Conference.
-
Konferensbidrag (populärvet., debatt m.m.)abstract
- A major challenge in the design of active safety systems for vehicles is to approximate the reality collected by sensors into a set of reliable and useful properties. Inability to do so can cause the active safety system to perform in a way, that will put the vehicle in a situation where the driver behaves in an unpredictable way, Unpredictable behavior in these systems can cause the vehicle to enter an unsafe state for itself or others. In order to achieve highly dependable applications it is important not only to know the behavior of sensor data, it is also important to put feasible limitations of the input data to guarantee a safe and predictable function.This paper presents methods to improve and assess the decision material of active safety functions such as driver support systems with autonomous braking. The methods are introduced to increase the dependability of the function but also to set more accurate scope and also avoid so-called slightly out of specifications, SOS, fault.
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| 23. |
- Sandberg, Anders, 1975, et al.
(författare)
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SEA domain autoproteolysis accelerated by conformational strain: energetic aspects.
- 2008
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Ingår i: Journal of molecular biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 377:4, s. 1117-29
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Tidskriftsartikel (refereegranskat)abstract
- A subclass of proteins with the SEA (sea urchin sperm protein, enterokinase, and agrin) domain fold exists as heterodimers generated by autoproteolytic cleavage within a characteristic G(-1)S+1VVV sequence. Autoproteolysis occurs by a nucleophilic attack of the serine hydroxyl on the vicinal glycine carbonyl followed by an N-->O acyl shift and hydrolysis of the resulting ester. The reaction has been suggested to be accelerated by the straining of the scissile peptide bond upon protein folding. In an accompanying article, we report the mechanism; in this article, we provide further key evidence and account for the energetics of coupled protein folding and autoproteolysis. Cleavage of the GPR116 domain and that of the MUC1 SEA domain occur with half-life (t((1/2))) values of 12 and 18 min, respectively, with lowering of the free energy of the activation barrier by approximately 10 kcal mol(-1) compared with uncatalyzed hydrolysis. The free energies of unfolding of the GPR116 and MUC1 SEA domains were measured to approximately 11 and approximately 15 kcal mol(-1), respectively, but approximately 7 kcal mol(-1) of conformational energy is partitioned as strain over the scissile peptide bond in the precursor to catalyze autoproteolysis by substrate destabilization. A straining energy of approximately 7 kcal mol(-1) was measured by using both a pre-equilibrium model to analyze stability and cleavage kinetics data obtained with the GPR116 SEA domain destabilized by core mutations or urea addition, as well as the difference in thermodynamic stabilities of the MUC1 SEA precursor mutant S1098A (with a G(-1)A+1VVV motif) and the wild-type protein. The results imply that cleavage by N-->O acyl shift alone would proceed with a t((1/2)) of approximately 2.3 years, which is too slow to be biochemically effective. A subsequent review of structural data on other self-cleaving proteins suggests that conformational strain of the scissile peptide bond may be a common mechanism of autoproteolysis.
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| 24. |
- Sandberg, Jan, 1955-
(författare)
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Fouling in biomass fired boilers
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to reduce the discharge of the greenhouse gas CO2, the use of biomass is nowadays promoted as fuel in boilers. Compared to boilers fired with coal and oil the biomass-fired boilers have more complications related to both fouling and corrosion on the heat transfer surfaces. After the combustion, unburned inorganic matter in state of vapour, melts and solid particles are transported in the flue gas and may form deposits on heat transfer surfaces.Deposits on the heat transfer surfaces may result in both increasing corrosion and decreasing boiler efficiency as the heat transfer rate to the superheaters and reheaters decrease by deposits.In order to understand the process of deposit build-up, the whole combustion and transport process had to be analysed including aspects such as, boiler design, fuel properties and combustion environment, followed by particle transport phenomena and the probability for particles to get stuck on the heat transfer tubes.In this thesis numerical simulation of particle trajectories has been conducted as well as measurements of deposits on a special designed deposit probe followed by investigation of on-site measurements of deposit depth on the super-heater tubes in a circulating fluidised bed in Västerås, Sweden.Numerical simulations of particle trajectories in the vicinity of two super-heater tubes were conducted in an Eulerian-Lagrangian mode considering the flue gas and ash particles phase. Particle impingements on the tubes were investigated for different particle sizes. The results from the particle trajectory simulations show that particle larger than 10 µm will mainly impinge on the windward side of the first tube but, however also on the sides of the second tube in the flue gas flow direction. In theory as well as from observations and measurements two tubes can merge together by the deposit build-up. Smaller particles are usually more dispersed due to turbulence and thermophorectic forces, resulting in a more even impingement distribution on the whole surface of the tubes.Probe measurements reveal that the deposit layer growth rate have a significant temperature and time dependence. After the initial deposit build-up a sintering process occurs and sintering is also proven to be dependent on temperature and exposure time.Soot-blowing is the most common method to reduce the effect of deposits on the heat transfer tubes. In the present thesis the soot boiling efficiency is therefore also investigated. The soot-blowing show a strong positive effect on the heat transfer rate in a short time (hours) perspective after a soot-blowing cycle is completed. This positive effect is much weaker when considering a time period of three years. This is an effect of fact that soot-blowing mostly remove the loose part of the deposit material leaving the hard sintered part unaffected.The subject of deposit build up on superheater tubes in large scale boilers involves multi-discipline knowledge and historically, the related research is mostly conducted as measurements and experiments on operating plants. Possibly in the future, theoretical simulations will have a bigger part of research on deposit build-up where the calculations are to be calibrated through measurements on real sites plants.
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| 25. |
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| 26. |
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| 27. |
- Sandberg, Linda, et al.
(författare)
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Replication-competent Ad11p vector (RCAd11p) efficiently transduces and replicates in hormone-refractory metastatic prostate cancer cells
- 2009
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Ingår i: Human Gene Therapy. - : Mary Ann Liebert Inc. - 1043-0342 .- 1557-7422. ; 20:4, s. 361-373
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Tidskriftsartikel (refereegranskat)abstract
- Selective replication-competent adenovirus serotype 5 vectors have been used for prostate cancer therapy. Unfortunately, gene transfer is inefficient because hormone-refractory metastatic prostate cancer cells have minimal coxsackievirus-adenovirus receptor expression. Vectors based on species B adenoviruses are attractive tools for use in human gene therapy because the viruses have low seroprevalence and they have efficient transduction capacity. Most species B adenoviruses use ubiquitously expressed complement-regulatory CD46 protein as a cellular receptor. Here we report the transduction efficacy and oncolytic capacity of a replication-competent Ad11p (RCAd11p) vector in human prostate cancer cells. Green fluorescent protein was efficiently expressed in a dose-dependent manner in PC-3 and DU 145 cells derived from metastasis of prostate cancer to bone and brain, respectively. However, transduction was less effective in LNCaP cells derived from prostate cancer metastasis to lymph nodes. The oncolytic capacity of the RCAd11p vector was 100 times higher in PC-3 cells than in the two other cell lines. The oncolysis was independent of the level of expression of p53 in the cells or on the absence of E1B55k expression in the vector. In vivo experiments revealed significant growth inhibition of PC-3 tumors in the xenograft mouse group treated with RCAd11p vector or Ad11pwt in comparison with the untreated control group. Thus, we have demonstrated that RCAd11p vector intrinsically possesses oncolytic properties, which were active in targeting tumor cells. Consequently, the novel RCAd11p vector has great potential for the treatment of incurable metastatic prostate disease.
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| 28. |
- Sandberg, Mattias, 1976-
(författare)
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Approximation of Optimally Controlled Ordinary and Partial Differential Equations
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, which consists of four papers, approximation of optimal control problems is studied. In Paper I the Symplectic Pontryagin method for approximation of optimally controlled ordinary differential equations is presented. The method consists of a Symplectic Euler time stepping scheme for a Hamiltonian system with a regularized Hamiltonian. Under some assumptions it is shown that the approximate value function associated with this scheme converges to the original value function with a linear rate. In Paper II the ideas from Paper I are extended to approximation of an optimally controlled partial differential equation, a one-dimensional Ginzburg-Landau equation. The approximation is performed in two steps. In the first step a value function associated with a finite element spatial discretization is shown to converge quadratically in the mesh size to the original value function. In the second step a Symplectic Euler discretization in time is shown to converge with a linear rate. The behavior of optimal solutions is shown by numerical examples. In Paper III the same approximation method as in Paper II is applied to three other problems; the optimal design of an electric conductor, the design of an elastic domain, and the problem of reconstructing the interior of an object from measured electrical surface currents. Since these problems are time-independent the Hamilton-Jacobi theory can not be used. In order to be able to obtain error bounds the problems are therefore transferred to a setting where time plays a role. Computer experiments with the Symplectic Pontryagin method is performed for all three problems. Common to the three first papers is that the convergence proofs use that the approximate value functions solve Hamilton-Jacobi equations consistent with the original Hamilton-Jacobi equations. Paper IV concerns convergence of attainable sets for non-convex differential inclusions. When the right hand side in the differential inclusion is a bounded, Lipschitz set-valued function it is shown that the convergence in Hausdorff-distance of attainable sets for a Forward Euler discretization is linear in the time step. This implies that dynamic programming using Forward Euler discretizations of optimal control problems converge with a linear rate when all the functions involved are bounded and Lipschitz continuous.
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| 29. |
- Sandberg, Mattias, et al.
(författare)
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Convergence rates of symplectic pontryagin approximations in optimal control theory
- 2006
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Ingår i: Mathematical Modelling and Numerical Analysis. - : EDP Sciences. - 0764-583X .- 1290-3841. ; 40:1, s. 149-173
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Tidskriftsartikel (refereegranskat)abstract
- Many inverse problems for differential equations can be formulated as optimal control problems. It is well known that inverse problems often need to be regularized to obtain good approximations. This work presents a systematic method to regularize and to establish error estimates for approximations to some control problems in high dimension, based on symplectic approximation of the Hamiltonian system for the control problem. In particular the work derives error estimates and constructs regularizations for numerical approximations to optimally controlled ordinary differential equations in R-d, with non smooth control. Though optimal controls in general become non smooth, viscosity solutions to the corresponding Hamilton-Jacobi-Bellman equation provide good theoretical foundation, but poor computational efficiency in high dimensions. The computational method here uses the adjoint variable and works efficiently also for high dimensional problems with d >> 1. Controls can be discontinuous due to a lack of regularity in the Hamiltonian or due to colliding backward paths, i.e. shocks. The error analysis, for both these cases, is based on consistency with the Hamilton-Jacobi-Bellman equation, in the viscosity solution sense, and a discrete Pontryagin principle: the bi-characteristic Hamiltonian ODE system is solved with a C-2 approximate Hamiltonian. The error analysis leads to estimates useful also in high dimensions since the bounds depend on the Lipschitz norms of the Hamiltonian and the gradient of the value function but not on d explicitly. Applications to inverse implied volatility estimation, in mathematical finance, and to a topology optimization problem are presented. An advantage with the Pontryagin based method is that the Newton method can be applied to efficiently solve the discrete nonlinear Hamiltonian system, with a sparse Jacobian that can be calculated explicitly.
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| 30. |
- Shiriaev, Anton, et al.
(författare)
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Periodic motion planning for virtually constrained Euler-Lagrange systems
- 2006
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Ingår i: Systems & control letters (Print). - Amsterdam : Elsevier. - 0167-6911 .- 1872-7956. ; 55:11, s. 900-907
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Tidskriftsartikel (refereegranskat)abstract
- The paper suggests an explicit form of a general integral of motion for some classes of dynamical systems including n-degrees of freedom Euler-Lagrange systems subject to (n - 1) virtual holonomic constraints. The knowledge of this integral allows to extend the classical results due to Lyapunov for detecting a presence of periodic solutions for a family of second order systems, and allows to solve the periodic motion planning task for underactuated Euler-Lagrange systems, when there is only one not directly actuated generalized coordinate. As an illustrative example, we have shown how to create a periodic oscillation of the pendulum for a cart-pendulum system and how then to make them orbitally exponentially stable following the machinery developed in [A. Shiriaev, J. Perram, C. Canudas-de-Wit, Constructive tool for an orbital stabilization of underactuated nonlinear systems: virtual constraint approach, IEEE Trans. Automat. Control 50 (8) (2005) 1164-1176]. The extension here also considers time-varying virtual constraints.
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| 31. |
- Shiriaev, Anton S, et al.
(författare)
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Periodic motion planning for virtually constrained (hybrid) mechanical systems
- 2005
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Ingår i: 2005 44th IEEE conference on decision and control & European control conference, vols 1-8. - New York : IEEE conference proceedings. - 0780395670 - 0780395689 ; , s. 4035-4040
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Konferensbidrag (refereegranskat)abstract
- The paper presents sufficient and almost necessary conditions for the presence of periodic solutions for zero dynamics of virtually constrained under-actuated Euler-Lagrange system. This result is further extended to detect periodic solutions for a class of hybrid systems in the plane and analyze their orbital stability and instability. Illustrative examples are given.
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| 32. |
- Sikter, David, et al.
(författare)
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Economic perspectives on quality control in TMP refining processes
- 2008
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 23:3, s. 305-314
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Tidskriftsartikel (refereegranskat)abstract
- Many Studies have been carried out with the goal of improving pulp quality control in TMP refining processes. While it is intuitively clear that minimizing the deviations from the target quality is desirable, the economic value Of Such reduced quality variations is complicated to estimate. So far not much research has been done in this area related to the pulp and paper industry. This Study has been performed to address this issue and to increase the knowledge, in economic terms, of the different mechanisms involved. The focus lies in controlling the pulp quality stability of the refining stage. Several areas in which economic benefits arise from improved quality control are analyzed in more detail. A generic model for estimating the economic Value of improved quality optimization is developed. Applied to freeness variability reduction, the model indicates notable economic savings, partly in terms of energy. The connection between pulp quality variations and web-breaks in the paper machine has been Studied in a full scale trial. The results indicate that a reduction of web breaks may yield a significant contribution to the profit. Improving the quality control may also enable a production rate increase. In this case there are some energy savings due to improved refiner efficiency at higher throughput. The major economic profit contribution from production increase does however come from the additional Volume of paper.
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| 33. |
- Sivencrona, H., et al.
(författare)
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SWAP-design of an AUTOSAR open laboratory test bench
- 2008
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Ingår i: SAE International Journal of Passenger Cars - Electronic and Electrical Systems. - : SAE International. - 1946-4622.
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Konferensbidrag (refereegranskat)abstract
- This article describes an AUTOSAR testbench that will be evaluated by the SWAP (SoftWare Automotive Platform) project. It presents the functionality as well as the expected use of the platform. SWAP is a Swedish research initiative whose goal is to increase AUTOSAR competence throughout the design of an AUTOSAR compliant test bench. The test bench will be provided in an open laboratory where an AUTOSAR Version 3.0 (4.0 is planned)-compliant basic software, including applications, necessary tools and hardware, e.g. ECUs and communication bus, will be made available. The test bench will hopefully be useful for a broad range of applied research and product development projects. Also, SWAP will manage AUTOSAR seminars for increasing the know-how for interested users. SWAP will also provide a basis for establishing and increasing knowledge in the area of adapting AUTOSAR to the emerging functional safety standard ISO WD 26262.
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| 34. |
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| 35. |
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| 36. |
- Sorensen, Per Soelberg, et al.
(författare)
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NORdic trial of oral Methylprednisolone as add-on therapy to Interferon beta-1a for treatment of relapsing-remitting Multiple Sclerosis (NORMIMS study) : a randomised, placebo-controlled trial
- 2009
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Ingår i: Lancet Neurology. - 1474-4422 .- 1474-4465. ; 8:6, s. 519-529
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Treatment of relapsing-remitting multiple sclerosis with interferon beta is only partly effective, and new more effective and safe strategies are needed. Our aim was to assess the efficacy of oral methylprednisolone as an add-on therapy to subcutaneous interferon beta-1a to reduce the yearly relapse rate in patients with relapsing-remitting multiple sclerosis. METHODS: NORMIMS (NORdic trial of oral Methylprednisolone as add-on therapy to Interferon beta-1a for treatment of relapsing-remitting Multiple Sclerosis) was a randomised, placebo-controlled trial done in 29 neurology departments in Denmark, Norway, Sweden, and Finland. We enrolled outpatients with relapsing-remitting multiple sclerosis who had had at least one relapse within the previous 12 months despite subcutaneous interferon beta-1a treatment (44 microg three times per week). We randomly allocated patients by computer to add-on therapy of either 200 mg methylprednisolone or matching placebo, both given orally on 5 consecutive days every 4 weeks for at least 96 weeks. The primary outcome measure was mean yearly relapse rate. Primary analyses were by intention to treat. This trial is registered, number ISRCTN16202527. FINDINGS: 66 patients were assigned to interferon beta and oral methylprednisolone and 64 were assigned to interferon beta and placebo. A high proportion of patients withdrew from the study before week 96 (26% [17 of 66] on methylprednisolone vs 17% [11 of 64] on placebo). The mean yearly relapse rate was 0.22 for methylprednisolone compared with 0.59 for placebo (62% reduction, 95% CI 39-77%; p<0.0001). Sleep disturbance and neurological and psychiatric symptoms were the most frequent adverse events recorded in the methylprednisolone group. Bone mineral density had not changed after 96 weeks. INTERPRETATION: Oral methylprednisolone given in pulses every 4 weeks as an add-on therapy to subcutaneous interferon beta-1a in patients with relapsing-remitting multiple sclerosis leads to a significant reduction in relapse rate. However, because of the small number of patients and the high dropout rate, these findings need to be corroborated in larger cohorts.
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| 37. |
- Sundmark, Daniel, et al.
(författare)
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Finding DU-Paths for Testing of Multi-Tasking Real-Time Systems using WCET Analysis
- 2007
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Ingår i: OpenAccess Series in Informatics, Volume 6. - 9783939897057
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Memory corruption is one of the most common software failures. For sequential software and multitasking software with synchronized data accesses, it has been shown that program faults causing memory corruption can be detected by analyzing the relations between defines and uses of variables (DU-based testing). However, such methods are insufficient in preemptive systems, since they lack the ability to detect inter-task shared variable dependencies. In this paper, we propose the use of a system level shared variable DU analysis of preemptive multi-tasking real-time software. By deriving temporal attributes of each access to shared data using WCET analysis, and combining this information with the real-time schedule information, our method also detects inter-task shared variable dependencies
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| 38. |
- Walker, Martin, et al.
(författare)
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Semi-automatic FMEA supporting complex systems with combinations and sequences of failures
- 2009
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Ingår i: SAE International Journal of Passenger Cars - Mechanical Systems. - : Society of Automotive Engineers. - 1946-3995 .- 1946-4002. ; 2:1, s. 791-802
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Tidskriftsartikel (refereegranskat)abstract
- Failure Modes and Effects Analysis (FMEA) is a well established safety analysis technique used for the assessment of safety critical engineering systems in the automotive industry. Although FMEA has been shown to be useful, the analysis is typically restricted to the effects of single component failures; even partial analysis of combinations or sequences of multiple failures is in practice considered too complex, laborious and costly to perform. In this paper, we describe a new technique in which FMEAs are semi-automatically built from the topology of a system and component-level specifications of failure data. The proposed technique allows an extended form of combinatorial & sequential FMEA in which assessment of the effects of combinations and sequences of failures becomes feasible and cost effective. We show how this technique can address difficulties encountered in classical FMEA and, drawing from a simplified brake-by-wire example, we show how it can improve the assessment of safety critical automotive systems.
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| 39. |
- Weber, Thomas, et al.
(författare)
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Resistance of flight feathers to mechanical fatigue covaries with moult strategy in two warbler species
- 2005
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Ingår i: Biology letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 1:1, s. 27-30
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Tidskriftsartikel (refereegranskat)abstract
- Flight feather moult in small passerines is realized in several ways. Some species moult once after breeding or once on their wintering grounds; others even moult twice. The adaptive significance of this diversity is still largely unknown. We compared the resistance to mechanical fatigue of flight feathers from the chiffchaff Phylloscopus collybita, a migratory species moulting once on its breeding grounds, with feathers from the willow warbler Phylloscopus trochilus, a migratory species moulting in both its breeding and wintering grounds. We found that flight feathers of willow warblers, which have a shaft with a comparatively large diameter, become fatigued much faster than feathers of chiffchaffs under an artificial cyclic bending regime. We propose that willow warblers may strengthen their flight feathers by increasing the diameter of the shaft, which may lead to a more rapid accumulation of damage in willow warblers than in chiffchaffs.
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| 40. |
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