| 1. |
- Andersson, Alexander, et al.
(författare)
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Presence of Calcium Cations Stimulate Alkaline Hydrolysis of Cellulose During Kraft Pulping Conditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Simulated kraft pulping has been performed on cotton linters fibers consisting of almost pure cellulose with varying content of calcium ions. These concentrations were obtained by soaking and drying cotton linters in calcium sulfate solutions. The viscosities of the pulped fibers were generally lower with higher calcium ion concentration and, therefore, in line with earlier suggested ideas that calcium ions could catalyze alkaline hydrolysis. The technical importance of these results is discussed.
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| 2. |
- Andersson, Malin, et al.
(författare)
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Electrochemical model-based aging-adaptive fast charging of automotive lithium-ion cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Fast charging of electric vehicles remains a compromise between charging time and degradation penalty. Conventional battery management systems use experience-based charging protocols that are expected to meet vehicle lifetime goals. Novel electrochemical model-based battery fast charging uses a model to observe internal battery states. This enables control of charging rates based on states such as the lithium-plating potential but relies on an accurate model as well as accurate model parameters. However, the impact of battery degradation on the model’s accuracy and therefore the fitness of the estimated optimal charging procedure is often not considered. In this work, we therefore investigate electrochemical model-based aging-adaptive fast charging of automotive lithium-ion cells. First, an electrochemical model is identified at the beginning of life for 6 automotive prototype cells and the electrochemically constrained fast-charge is designed. The model parameters are then periodically re-evaluated during a cycling study and the charging procedure is updated to account for cell degradation. The proposed method is compared with two reference protocols to investigate both the effectiveness of selected electrochemical constraints as well as the benefit of aging-adaptive usage. Finally, post-mortem characterization is presented to highlight the benefit of aging-adaptive battery utilization.
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| 3. |
- Andersson, Michael K., et al.
(författare)
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Bootstrap testing for fractional integration
- 1998
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Asymptotic tests for fractional integration, such as the Geweke-Porter-Hudak test, the modified rescaled range test and Lagrange multiplier type tests, exhibit size distortions in small samples. This paper investigates a parametric bootstrap testing procedure, for size correction, by means of a computer simulation study. The bootstrap provides a practical method to eliminate size distortions in the case of an asymptotic pivotal statistic while the power, in general, is close to the corresponding size adjusted asymptotic test. The results are very encouraging and suggest that a bootstrap testing procedure does correct for size distortions.
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| 4. |
- Andersson, Michael K., et al.
(författare)
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Robust testing for fractional integration using the bootstrap
- 1998
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Asymptotic tests for fractional integration are usually badly sized in small samples, even for normally distributed processes. Furthermore, tests that are well-sized (under normality) may be seriously distorted by non-normalities and ARCH errors. This paper demonstrates how the bootstrap can be implemented to correct for such size distortions. It is shown that a well-designed bootstrap test based on the MRR and GPH tests is exact, and that a procedure based on the REG test is nearly exact. Ort, förlag, år, upplaga, sidor
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| 5. |
- Andersson, Mikael, et al.
(författare)
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Physical activity and fatigue in chronic obstructive pulmonary disease : A population based study
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- IntroductionDyspnea with exertion and fatigue are the cardinal symptoms of chronic obstructive pulmonary disease (COPD); impaired muscle function and reduced exercise capacity are also frequently associated with COPD. We aimed to assess the physical activity levels, in a population based sample study, of subjects with and without COPD. We also aimed to investigate the factors associated with low physical activity in these groups.MethodsIn this study, 470 subjects with COPD (FEV1/FVC< 0.70) and 569 subjects without COPD (Non-COPD) were analyzed. Physical activity was assessed with the International Physical Activity Questionnaire (IPAQ). Fatigue was investigated with the Functional Assessment of Chronic Illness Therapy - Fatigue scale (FACIT-F). An interview questionnaire was used to record the sample characteristics and history of heart disease. Binary logistic regression was used to investigate the factors associated with low physical activity.ResultsLow physical activity was significantly more prevalent in GOLD grade ≥II COPD subjects, and this prevalence was higher than that for Non-COPD subjects (22.4 vs. 14.6%, p = 0.016). The strongest factors associated with low physical activity in COPD subjects were a history of heart disease, OR (CI 95%) 2.11 (1.10 - 4.08), and clinically significant fatigue, OR 2.33 (1.31 - 4.13); obesity was the only significant factor in Non-COPD subjects, OR 2.26 (1.17 – 4.35).ConclusionPhysical activity levels are reduced for COPD grade II and higher, and the factors associated with lower levels of physical activity are different for the COPD group compared to the Non-COPD group. We propose that measurements of fatigue and a history of heart disease are useful tools to include when screening subjects for pulmonary rehabilitation.
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| 6. |
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| 7. |
- Brindefalk, Björn, 1977-, et al.
(författare)
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Lost and Found at Sea: a Phylomentagenomic Exploration of Mitochondrial Affiliations with Oceanic Bacteria.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background According to the endosymbiont hypothesis, the mitochondrial system for aerobic respiration was derived from a free-living bacterium related to present-day alpha-proteobacteria. Recent studies have identified two lineages as the closest mitochondrial relatives among bacteria with sequenced genomes; the Rickettsiales, a lineage comprising obligate intracellular pathogens, and Pelagibacter ubique, a member of the SAR11 clade that is highly abundant in the upper surface waters of the global oceans. Principal Findings Here, we present a phylogenetic study incorporating metagenomic data of mitochondrial genes for aerobic respiration that includes sequence data from the Global Ocean Sampling (GOS) Expedition, thereby increasing the sampling of alpha-proteobacterial sequences available for analysis greatly. Phylogenetic analysis of these expanded datasets including oceanic sequences that had been pruned down in numbers but still maintained the full genetic diversity present failed to show an increased support for a specific mitochondrial affiliation to any alpha-proteobacterial group, although concatenated datasets of different genes gave good support for conflicting mitochondrial placement. We utilized a jack-knifing method to randomly sample sequences from the GOS dataset and examined how the inclusion of such sequences influenced the support for mitochondrial affiliation in trees inferred from proteins in aerobic respiration. No evidence of an increased support for a specific mitochondrial placement in the alpha-proteobacterial tree in the jack-knifing analysis was obtained. A systematic search for sequences affiliated with mitochondria in the GOS dataset suggests the existence of previously unidentified clades of deeply diverging alpha-proteobacteria, with an unclear affiliation. Conclusions/Significance Our findings have several important implications. First, they support an early divergence of the mitochondrial ancestor from the alpha-proteobacterial lineage, possibly pre-dating the radiation of alpha-proteobacterial species with sequenced genomes. Second, they reject the hypothesis that the system for aerobic respiration in mitochondria is affiliated with the SAR11 clade. Third, they indicate horizontal transfer of genes for respiratory chain proteins in bacteria adapted to the upper surface waters of the oceans. Fourth, they show the presence of oceanic sequences for respiratory chain proteins that diverge as deeply as mitochondria in the alpha-proteobacterial phylogeny, possibly indicating a previously unidentified alpha-proteobacterial group at a basal position of the alpha-proteobacterial tree, underscoring the importance of expanding studies on mitochondrial origins beyond those of cultivated and intracellular bacteria. Finally, our study outlines a new methodology, phylometagenomics, which provides guidance on how to incorporate metagenome data into a phylogenetic framework for inferences of early evolutionary events.
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| 8. |
- Brindefalk, Björn, 1977-, et al.
(författare)
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Mitochondrial and alpha-proteobacterial time of divergence - a question of antecedence
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Mitochondria are believed to have originated by the incorporation of an alpha-proteobacterium into an un-defined "proto-eukaryote", although the exact nature of the two participants in this endo-symbiotic event is not known. Attempts to place the endo-symbiont with a specific group of extant alpha-proteobacteria has in most cases identified the Rickettsiales as the sister-group to mitochondria, although recent work has shown that this could be due to methodological artefacts and that the mitochondria should instead be considered a sister-clade to alphaproteobacteria. Equally uncertain is the time at which this endo-symbiotic event took place, and if it coincides with the event that gave rise to the eukaryotes themselves. In this work we attempt to use molecular dating methods to compare the time-point of mitochondrial divergence to the time-point of divergence of the alpha-proteobacteria, under the two hypothetical topologies mentioned. We show that if mitochondria are considered as a sister-clade to the alpha-proteobacteria, mitochondria likely diverged prior to the radiation of extant alpha-proteobacteria, and that the alpha-proteobacterial clade itself might be significantly younger than shown in previous analyses.
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