| 1. |
- Ludvigsson, Johnny, et al.
(författare)
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GAD65 antigen therapy in recently diagnosed type 1 diabetes mellitus
- 2012
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Ingår i: New England Journal of Medicine. - : Massachusetts Medical Society. - 0028-4793 .- 1533-4406. ; 366:5, s. 433-442
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The 65-kD isoform of glutamic acid decarboxylase (GAD65) is a major autoantigen in type 1 diabetes. We hypothesized that alum-formulated GAD65 (GAD-alum) can preserve beta-cell function in patients with recent-onset type 1 diabetes.METHODS: We studied 334 patients, 10 to 20 years of age, with type 1 diabetes, fasting C-peptide levels of more than 0.3 ng per milliliter (0.1 nmol per liter), and detectable serum GAD65 autoantibodies. Within 3 months after diagnosis, patients were randomly assigned to receive one of three study treatments: four doses of GAD-alum, two doses of GAD-alum followed by two doses of placebo, or four doses of placebo. The primary outcome was the change in the stimulated serum C-peptide level (after a mixed-meal tolerance test) between the baseline visit and the 15-month visit. Secondary outcomes included the glycated hemoglobin level, mean daily insulin dose, rate of hypoglycemia, and fasting and maximum stimulated C-peptide levels.RESULTS: The stimulated C-peptide level declined to a similar degree in all study groups, and the primary outcome at 15 months did not differ significantly between the combined active-drug groups and the placebo group (P=0.10). The use of GAD-alum as compared with placebo did not affect the insulin dose, glycated hemoglobin level, or hypoglycemia rate. Adverse events were infrequent and mild in the three groups, with no significant differences.CONCLUSIONS: Treatment with GAD-alum did not significantly reduce the loss of stimulated C peptide or improve clinical outcomes over a 15-month period.
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| 2. |
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| 3. |
- Choi, H., et al.
(författare)
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Residential culturable fungi, (1-3,1-6)-beta-d-glucan, and ergosterol concentrations in dust are not associated with asthma, rhinitis, or eczema diagnoses in children
- 2014
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Ingår i: Indoor Air. - : Wiley-Blackwell. - 0905-6947 .- 1600-0668. ; 24:2, s. 158-170
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Tidskriftsartikel (refereegranskat)abstract
- Qualitative reporting of home indoor moisture problems predicts respiratory diseases. However, causal agents underlying such qualitative markers remain unknown. In the homes of 198 multiple allergic case children and 202 controls in Sweden, we cultivated culturable fungi by directly plating dust, and quantified (1-3, 1-6)-beta-d-glucan and ergosterol in dust samples from the child's bedroom. We examined the relationship between these fungal agents and degree of parent or inspector-reported home indoor dampness, and microbiological laboratory's mold index. We also compared the concentrations of these agents between multiple allergic cases and healthy controls, as well as IgE-sensitization among cases. The concentrations of culturable fungal agents were comparable between houses with parent and inspector-reported mold issues and those without. There were no differences in concentrations of the individual or the total summed culturable fungi, (1-3, 1-6)-beta-d-glucan, and ergosterol between the controls and the multiple allergic case children, or individual diagnosis of asthma, rhinitis, or eczema. Culturable fungi, (1-3, 1-6)-beta-d-glucan, and ergosterol in dust were not associated with qualitative markers of indoor dampness or mold or indoor humidity. Furthermore, these agents in dust samples were not associated with any health outcomes in the children.
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| 4. |
- Flach, Carl-Fredrik, 1977, et al.
(författare)
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Does antifouling paint select for antibiotic resistance?
- 2017
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 590, s. 461-468
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Tidskriftsartikel (refereegranskat)abstract
- There is concern that heavy metals and biocides contribute to the development of antibiotic resistance via co-selection. Most antifouling paints contain high amounts of such substances, which risks turning painted ship hulls into highly mobile refuges and breeding grounds for antibiotic-resistant bacteria. The objectives of this study were to start investigate if heavy-metal based antifouling paints can pose a risk for co-selection of antibiotic-resistant bacteria and, if so, identify the underlying genetic basis. Plastic panels with one side painted with copper and zinc-containing antifouling paint were submerged in a Swedish marina and biofilms from both sides of the panels were harvested after 2.5-4 weeks. DNA was isolated from the biofilms and subjected to metagenomic sequencing. Biofilm bacteria were cultured on marine agar supplemented with tetracycline, gentamicin, copper sulfate or zinc sulfate. Biofilm communities from painted surfaces displayed lower taxonomic diversity and enrichment of Gammaproteobacteria. Bacteria from these communities showed increased resistance to both heavy metals and tetracycline but not to gentamicin. Significantly higher abundance of metal and biocide resistance genes was observed, whereas mobile antibiotic resistance genes were not enriched in these communities. In contrast, we found an enrichment of chromosomal RND efflux system genes, including such with documented ability to confer decreased susceptibility to both antibiotics and biocides/heavy metals. This was paralleled by increased abundances of integron-associated integrase and ISCR transposase genes. The results show that the heavy metal-based antifouling paint exerts a strong selection pressure on marine bacterial communities and can co-select for certain antibiotic-resistant bacteria, likely by favoring species and strains carrying genes that provide cross-resistance. Although this does not indicate an immediate risk for promotion of mobile antibiotic resistance, the clear increase of genes involved in mobilizing DNA provides a foundation for increased opportunities for gene transfer in such communities, which might also involve yet unknown resistance mechanisms.
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| 5. |
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| 6. |
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| 7. |
- Isgren, Anniella, et al.
(författare)
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Markers of neuroinflammation and neuronal injury in bipolar disorder: Relation to prospective clinical outcomes.
- 2017
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Ingår i: Brain, behavior, and immunity. - : Elsevier BV. - 1090-2139 .- 0889-1591. ; 65, s. 195-201
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Tidskriftsartikel (refereegranskat)abstract
- Neuroimmune mechanisms have been linked to the pathophysiology of bipolar disorder based on studies of biomarkers in plasma, cerebrospinal fluid (CSF), and postmortem brain tissue. There are, however, no longitudinal studies investigating if CSF markers of neuroinflammation and neuronal injury predict clinical outcomes in patients with bipolar disorder. We have in previous studies found higher CSF concentrations of interleukin-8 (IL-8), monocyte chemoattractant protein 1 (MCP-1/CCL-2), chitinase-3-like protein 1 (CHI3L1/YKL-40), and neurofilament light chain (NF-L) in euthymic patients with bipolar disorder compared with controls. Here, we investigated the relationship of these CSF markers of neuroinflammation and neuronal injury with clinical outcomes in a prospective study. 77 patients with CSF analyzed at baseline were followed for 6-7years. Associations of baseline biomarkers with clinical outcomes (manic/hypomanic and depressive episodes, suicide attempts, psychotic symptoms, inpatient care, GAF score change) were investigated. Baseline MCP-1 concentrations were positively associated with manic/hypomanic episodes and inpatient care during follow-up. YKL-40 concentrations were negatively associated with manic/hypomanic episodes and with occurrence of psychotic symptoms. The prospective negative association between YKL-40 and manic/hypomanic episodes survived multiple testing correction. Concentrations of IL-8 and NF-L were not associated with clinical outcomes. High concentrations of these selected CSF markers of neuroinflammation and neuronal injury at baseline were not consistently associated with poor clinical outcomes in this prospective study. The assessed proteins may be involved in adaptive immune processes or reflect a state of vulnerability for bipolar disorder rather than being of predictive value for disease progression.
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| 8. |
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| 9. |
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| 10. |
- Larsson, Carl, 1997, et al.
(författare)
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Effects of lithium insertion induced swelling of a structural battery negative electrode
- 2023
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Ingår i: Composites Science and Technology. - 0266-3538. ; 244
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Tidskriftsartikel (refereegranskat)abstract
- Structural battery composites fall under the category multifunctional materials with the ability to simultaneously store electrical energy and carry mechanical load. While functioning as the negative electrode, the carbon fibres also act as mechanical reinforcement. Lithium ion insertion in the carbon fibres is accompanied by a large radial expansion of 6.6 % and an axial expansion of 0.85 % of the fibres. Furthermore, the elastic moduli of the carbon fibres are significantly affected by the insertion of lithium. Current structural battery modelling approaches do not consider these features. In this paper, we investigate the effect of lithium insertion in carbon fibres on the structural electrode mechanical properties by developing a computational model considering finite strains and lithium concentration dependent fibre moduli. The computational model enables representation of morphological change, whereby, features such as internal stress state, homogenized tangent stiffness and effective expansion of the electrode caused by carbon fibre lithiation can be predicted. The adopted finite strain formulation allows for consistent consideration of measurement data at varying state of lithiation. The significance of adopting the finite strain formulation is also shown numerically. Finally, by implementing a novel approach to homogenized stress-free expansion, it is shown that the computed expansion of the structural electrode follows a similar trend to what is observed from experiments.
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| 11. |
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| 12. |
- Larsson, Glenn, et al.
(författare)
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Pediatric trauma patients in Swedish ambulance services : a retrospective observational study of assessments, interventions, and clinical outcomes
- 2024
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Ingår i: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. - 1757-7241. ; 32:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPediatric trauma patients constitute a significant portion of the trauma population treated by Swedish Emergency Medical Services (EMS), and trauma remains a notable cause of death among Swedish children. Previous research has identified potential challenges in prehospital assessments and interventions for pediatric patients. In Sweden, there is limited information available regarding pediatric trauma patients in the EMS. The aim of this study was to investigate the prevalence of pediatric trauma patients within the Swedish EMS and describe the prehospital assessments, interventions, and clinical outcomes.MethodsThis retrospective observational study was conducted in a region of Southwestern Sweden. A random sample from ambulance and hospital records from the year 2019 was selected. Inclusion criteria were children aged 0–16 years who were involved in trauma and assessed by EMS clinicians.ResultsA total of 440 children were included in the study, representing 8.4% of the overall trauma cases. The median age was 9 years (IQR 3–12), and 60.5% were male. The leading causes of injury were low (34.8%) and high energy falls (21%), followed by traffic accidents. The children were assessed as severely injured in 4.5% of cases. A quarter of the children remained at the scene after assessment. Complete vital signs were assessed in 29.3% of children, and 81.8% of children were assessed according to the ABCDE structure. The most common intervention performed by prehospital professionals was the administration of medication. The mortality rate was 0.2%.ConclusionsPediatric trauma cases accounted for 8.4% of the overall trauma population with a variations in injury mechanisms and types. Vital sign assessments were incomplete for a significant proportion of children. The adherence to the ABCDE structure, however, was higher. The children remained at the scene after assessment requires further investigation for patient safety.
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| 13. |
- Larsson, Marcus, 1979-, et al.
(författare)
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Curvature based Antenna Selection Method Evaluated Using the Data Age Metric and V2V Measurements
- 2015
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Ingår i: 2015 IEEE International Conference on Communication Workshop (ICCW). - Piscataway, NJ : IEEE Press. - 9781467363051 ; , s. 2356-2362
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Konferensbidrag (refereegranskat)abstract
- In this paper, we compare a method for selecting transmission antenna based on road curvature to a method based on periodically alternating between left and right hand side transmission antennas. Both methods aim to improve the success rate for communication between participants in a platoon of vehicles. Moreover, we propose the data age metric for online use as input to the algorithm controlling the inter-vehicle distance in platooning, e.g. to decide appropriate gap between the vehicles depending on the V2V communication quality. The methods have been evaluated through V2V communication measurements performed using heavy duty vehicles on public highway. We show that, when using the curvature-based method, a 150 ms data age deadline is only missed approximately half as often compared to when periodically alternating between left and right hand side transmission antennas. The methods have also been compared for different antenna combinations. © 2015 IEEE
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| 14. |
- Larsson, Mats, et al.
(författare)
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Magnetic field effects on optical and transport properties in InAs/GaAs quantum dots
- 2006
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Ingår i: Physical Review B. - 1098-0121. ; 74:24
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Tidskriftsartikel (refereegranskat)abstract
- A photoluminescence study of self-assembled InAs/GaAs quantum dots under the influence of magnetic fields perpendicular and parallel to the dot layer is presented. At low temperatures, the magnetic field perpendicular to the dot layer alters the in-plane transport properties due to localization of carriers in wetting layer (WL) potential fluctuations. Decreased transport in the WL results in a reduced capture into the quantum dots and consequently a weakened dot-related emission. The effect of the magnetic field exhibits a considerable dot density dependence, which confirms the correlation to the in-plane transport properties. An interesting effect is observed at temperatures above approximately 100 K, for which magnetic fields, both perpendicular and parallel to the dot layer, induced an increment of the quantum dot photoluminescence. This effect is ascribed to the magnetic confinement of the exciton wave function, which increases the probability for carrier capture and localization in the dot, but affects also the radiative recombination with a reduced radiative lifetime in the dots under magnetic compression.
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| 15. |
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| 16. |
- Lozano, Rafael, et al.
(författare)
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Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
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Tidskriftsartikel (refereegranskat)abstract
- Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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| 17. |
- Nilsen, Per, 1960-, et al.
(författare)
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Realizing the potential of artificial intelligence in healthcare : Learning from intervention, innovation, implementation and improvement sciences
- 2022
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Ingår i: Frontiers in Health Services. - Lausanne : Frontiers Media S.A.. - 2813-0146. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Artificial intelligence (AI) is widely seen as critical for tackling fundamental challenges faced by health systems. However, research is scant on the factors that influence the implementation and routine use of AI in healthcare, how AI may interact with the context in which it is implemented, and how it can contribute to wider health system goals. We propose that AI development can benefit from knowledge generated in four scientific fields: intervention, innovation, implementation and improvement sciences.Aim: The aim of this paper is to briefly describe the four fields and to identify potentially relevant knowledge from these fields that can be utilized for understanding and/or facilitating the use of AI in healthcare. The paper is based on the authors' experience and expertise in intervention, innovation, implementation, and improvement sciences, and a selective literature review.Utilizing knowledge from the four fields: The four fields have generated a wealth of often-overlapping knowledge, some of which we propose has considerable relevance for understanding and/or facilitating the use of AI in healthcare.Conclusion: Knowledge derived from intervention, innovation, implementation, and improvement sciences provides a head start for research on the use of AI in healthcare, yet the extent to which this knowledge can be repurposed in AI studies cannot be taken for granted. Thus, when taking advantage of insights in the four fields, it is important to also be explorative and use inductive research approaches to generate knowledge that can contribute toward realizing the potential of AI in healthcare. © 2022 Nilsen, Reed, Nair, Savage, Macrae, Barlow, Svedberg, Larsson, Lundgren and Nygren.
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| 18. |
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| 19. |
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| 20. |
- Sarlin, Paul-Edouard, et al.
(författare)
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Back to the Feature: Learning Robust Camera Localization from Pixels to Pose
- 2021
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Ingår i: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 1063-6919. ; , s. 3246-3256
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Konferensbidrag (refereegranskat)abstract
- Camera pose estimation in known scenes is a 3D geometry task recently tackled by multiple learning algorithms. Many regress precise geometric quantities, like poses or 3D points, from an input image. This either fails to generalize to new viewpoints or ties the model parameters to a specific scene. In this paper, we go Back to the Feature: we argue that deep networks should focus on learning robust and invariant visual features, while the geometric estimation should be left to principled algorithms. We introduce PixLoc, a scene-agnostic neural network that estimates an accurate 6-DoF pose from an image and a 3D model. Our approach is based on the direct alignment of multiscale deep features, casting camera localization as metric learning. PixLoc learns strong data priors by end-to-end training from pixels to pose and exhibits exceptional generalization to new scenes by separating model parameters and scene geometry. The system can localize in large environments given coarse pose priors but also improve the accuracy of sparse feature matching by jointly refining keypoints and poses with little overhead. The code will be publicly available at github.com/cvg/pixloc.
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| 21. |
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| 22. |
- Abramian, David, 1992-, et al.
(författare)
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Diffusion-Informed Spatial Smoothing of fMRI Data in White Matter Using Spectral Graph Filters
- 2021
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Ingår i: NeuroImage. - : Elsevier. - 1053-8119 .- 1095-9572. ; 237
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Tidskriftsartikel (refereegranskat)abstract
- Brain activation mapping using functional magnetic resonance imaging (fMRI) has been extensively studied in brain gray matter (GM), whereas in large disregarded for probing white matter (WM). This unbalanced treatment has been in part due to controversies in relation to the nature of the blood oxygenation level-dependent (BOLD) contrast in WM and its detachability. However, an accumulating body of studies has provided solid evidence of the functional significance of the BOLD signal in WM and has revealed that it exhibits anisotropic spatio-temporal correlations and structure-specific fluctuations concomitant with those of the cortical BOLD signal. In this work, we present an anisotropic spatial filtering scheme for smoothing fMRI data in WM that accounts for known spatial constraints on the BOLD signal in WM. In particular, the spatial correlation structure of the BOLD signal in WM is highly anisotropic and closely linked to local axonal structure in terms of shape and orientation, suggesting that isotropic Gaussian filters conventionally used for smoothing fMRI data are inadequate for denoising the BOLD signal in WM. The fundamental element in the proposed method is a graph-based description of WM that encodes the underlying anisotropy observed across WM, derived from diffusion-weighted MRI data. Based on this representation, and leveraging graph signal processing principles, we design subject-specific spatial filters that adapt to a subject’s unique WM structure at each position in the WM that they are applied at. We use the proposed filters to spatially smooth fMRI data in WM, as an alternative to the conventional practice of using isotropic Gaussian filters. We test the proposed filtering approach on two sets of simulated phantoms, showcasing its greater sensitivity and specificity for the detection of slender anisotropic activations, compared to that achieved with isotropic Gaussian filters. We also present WM activation mapping results on the Human Connectome Project’s 100-unrelated subject dataset, across seven functional tasks, showing that the proposed method enables the detection of streamline-like activations within axonal bundles.
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| 23. |
- Ahmad, Alireza, et al.
(författare)
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Impact of particle arrangement and model dimensions on DEM modeling of high-speed railway ballasted tracks in 2D and 3D
- 2024
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Ingår i: Transportation Geotechnics. - : Elsevier BV. - 2214-3912. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Modelling railway projects has a main challenge in the discrete element method (DEM). The granular material of the embankment consists of millions of fine angular particles which are difficult to model due to the long computational time. The long computational time also prevents the modeling of the higher number of loading cycles. As a result, researchers prefer to simulate the project in 2D to accelerate the simulation. While 2D simulations present a seemingly simple option for modeling railways, they tend to oversimplify the intricacies of particle interactions and the distribution of stress. Nonetheless, the extent to which these simplifications affect the authenticity of the simulations has remained ambiguous. In this study, the periodic cell replication method is used to build extensive long railway tracks significantly faster than conventional methods. Then, this DEM model is calibrated against the measurement results of a physical full-scale ballasted track. The model is then used to simulate several railway projects with different initial particle arrangements and model dimensions in both 2D and 3D. The results show that the 2D models are more dependant on the initial particle arrangement which shows different behavior for the same model. In addition, 2D simulations are incapable of reproducing the principal stress rotation in granular layers due to the moving load of the train wheel. As a result, 3D DEM simulations using the periodic cell replication method is suggested for studying the railway tracks.
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| 24. |
- Ahmad, Alireza, et al.
(författare)
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Scaling granular material with polygonal particles in discrete element modeling
- 2023
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Ingår i: Particuology. - : Elsevier BV. - 1674-2001 .- 2210-4291. ; 75, s. 151-164
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Tidskriftsartikel (refereegranskat)abstract
- Despite advancements in computational resources, the discrete element method (DEM) still requires considerable computational time to solve detailed problems, especially when it comes to the large-scale models. In addition to the geometry scale of the problem, the particle shape has a dramatic effect on the computational cost of DEM. Therefore, many studies have been performed with simplified spherical particles or clumps. Particle scaling is an approach to increase the particle size to reduce the number of particles in the DEM. Although several particle scaling methods have been introduced, there are still some disagreements regarding their applicability to certain aspects of problems. In this study, the effect of particle scalping on the shear behavior of granular material is explored. Real granular particles were scanned and imported as polygonal particles in the direct shear test. The effect of particle size distribution, particle angularity, and the amount of scalping were investigated. The results show that particle scalping can simulate the correct shear behavior of the model with significant improvement in computational time. Also, the accuracy of the scalping method depends on the particle angularity and particle size range.
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| 25. |
- Ahmad, Alireza, et al.
(författare)
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The influence of the rail beam on the settlement ofhigh-speed railway tracks : A discrete element study
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Modelling railway embankments have two main challenges in the discrete ele-ment method (DEM). First, the granular material of the embankment consistof millions of fine angular particles which are difficult to model due to thelong computational time. As a result, researchers prefer to use spherical orscale-up particles as granular material. Also, it prevents the modeling of thehigher number of loading cycles. Second, the DEM is incapable of includingcontinuous rail beams due to its discrete nature. Therefore, most of the re-search is limited to ignoring the rail beam and other structural elements ofthe track. In this study, a DEM model is calibrated against the measure-ment results of a physical full-scale ballasted track. The model is then used toinvestigate the effect of including the rail beam for high-speed railways sub-jected to 2000 axle passages. The results show that although ignoring therail beam does not substantially affect the results for initial loading cycles,its influence is significant after a couple of hundred axle passages. The modelwithout a rail beam shows more principal stress rotation, more settlement,non-realistic vertical displacement of the sleepers, more particle rearrange-ment and more sleepers’ vibration. Therefore, it is necessary to include therail beam in the long-term analysis of the track to conclude realistic results.
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| 26. |
- Ahmadi, Alireza
(författare)
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Discrete element technique for modeling high-speed railway tracks
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Discrete element method (DEM) is a methodology to investigatethe interactions among granular materials. It analyzes the behavior of par-ticulate environments by solving force-displacement equations that adhereto Newton’s second law of motion. Despite its usefulness, the DEM is notwithout limitations, and researchers are still facing certain challenges thatrestrict them from performing detailed analyses of granular materials. Thisstudy addresses two issues in DEM modeling of granular materials in rail-way embankments. Firstly, the long computational time required by theDEM for modeling fine angular particles in granular materials is addressedby exploring the effects of particle scaling on the shear behavior of granularmaterial. This study investigates the impact of particle size distribution,particle angularity, and the amount of scaling on the accuracy and compu-tational efficiency of DEM. Secondly, the limitations of DEM in includingthe continuous rail beam structure in the track are addressed by verifyinga DEM model against physical measurements of a full-scale ballasted trackand investigating the influence of including the rail beam structure on high-speed railway ballasted tracks. The results show that the use of particlescaling in the first study significantly improves the computational efficiencyof the DEM while maintaining accuracy, and this method is used in thesecond study to investigate the influence of the rail beam structure on thebehavior of railway tracks.
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| 27. |
- Aho, Nikolas, 1970-
(författare)
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Victimization, Prevalence, Health and Peritraumatic Reactions in Swedish Adolescents
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis was to expand the knowledge of victimization in children and youth in Sweden. Victimization, prevalence, health and peritraumatic reactions were explored in a cross sectional, representative sample of 5,960 second grade high school students in Sweden. A computerized survey was developed and administered in class room setting.Lifetime victimization was found in 84.1% of the sample (m=83.0%, f=85.2%), and, in relation to the five domains, 66.4% had experienced conventional crime, 24% child maltreatment, 54.4% peer and sibling victimization, 21.8% sexual victimization, and 54% had experienced witness victimization. Females experienced significantly more child maltreatment, peer and sibling victimization, sexual victimization, and witnessed victimization, males more conventional crime (p<0.001). Using logistic regression risk factors for victimization were confirmed by a significant increase OR regarding gender, environment and lack of both parents.Symptoms (TSCC), were clearly associated with both victimizations per se and the number of victimizations. The results indicated a relatively linear increase in symptoms with an increase in number of events experienced. Mental health of the polyvictimized group was significantly worse than that of the non-polyvictimized group, with significantly elevated TSCC scores (t<0.001). Hierarchical regression analysis resulted in beta value reduction when polyvictimization was introduced supporting the independent effect on symptoms. Social anxiety was found in 10.2 % (n = 605) of the total group (n = 5,960). A significant gender difference emerged, with more females than males reporting social anxiety. Elevated PTSS was found in 14.8 % (n=883). Binary logistic regression revealed the highest OR for having had contact with child and adolescent psychiatry was found for the combined group with social anxiety and elevated PTSS (OR = 4.88, 95 % CI = 3.53–6.73, p<001). Significant associations were also found between use of child and adolescent psychiatry and female gender (OR = 2.05, 95 % CI = 1.70–2.45), Swedish birth origin (OR = 1.68, 95 % CI = 1.16–2.42) and living in a small municipality (OR = 1.33, 95 % CI = 1.02–1.73).Mediation models used peritraumatic reactions (PT): total, physiological arousal (PA), peritraumatic dissociation (PD), and intervention thoughts (IT) and JVQ and TSCC. Of the n=5,332 cases, a total of n=4,483 (84.1%) reported at least one victimizing event (m = 83.0%, f = 85.2%). Of these, 74.9% (n=3,360) also experienced a PT reaction of some kind. The effect mediated by PT tot was b= 0.479, BCa CI [0.342 – 0.640], representing a relatively small effect of 7.6%, κ2=0.076, 95% BCa CI [0.054- 0.101]. The mediating effect of JVQ on TSCC was mediated by PD more for males (b=0.394 BCa CI [0.170-0.636]) than for females (b=0.247, BCa CI [0.021-0.469]). The indirect effect of the JVQ on the TSCC tot mediated by the different PT reactions was significant for PD (b=0.355, BCa CI [0.199- 0.523]. In males a mediating effect of PD could be seen in the different models, while females had a more mixed result. IT did not show any indirect effect in males, but had a mixed effect for females.The empirical findings in this thesis lead to the conclusion that victimization is highly prevalent in children and youth and is related to health issues. The association of victimization on symptoms was mediated by peritraumatic reactions. Using a comprehensive instrument such as the JVQ provides the researcher or clinician the opportunity to acquire more complete measurement and also makes it possible to identify polyvictimization, a high-level category of events with severe impact on health.
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| 28. |
- Albers, Eva, 1966, et al.
(författare)
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Selective suppression of bacterial contaminants by process conditions during lignocellulose based yeast fermentations
- 2011
-
Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundContamination of bacteria in large-scale yeast fermentations is a serious problem and a threat to the development of successful biofuel production plants. Huge research efforts have been spent in order to solve this problem, but additional ways must still be found to keep bacterial contaminants from thriving in these environments. The aim of this project was to develop process conditions that would inhibit bacterial growth while giving yeast a competitive advantage.ResultsLactic acid bacteria are usually considered to be the most common contaminants in industrial yeast fermentations. Our observations support this view but also suggest that acetic acid bacteria, although not so numerous, could be a much more problematic obstacle to overcome. Acetic acid bacteria showed a capacity to drastically reduce the viability of yeast. In addition, they consumed the previously formed ethanol. Lactic acid bacteria did not show this detrimental effect on yeast viability. It was possible to combat both types of bacteria by a combined addition of NaCl and ethanol to the wood hydrolysate medium used. As a result of NaCl + ethanol additions the amount of viable bacteria decreased and yeast viability was enhanced concomitantly with an increase in ethanol concentration. The successful result obtained via addition of NaCl and ethanol was also confirmed in a real industrial ethanol production plant with its natural inherent yeast/bacterial community.ConclusionsIt is possible to reduce the number of bacteria and offer a selective advantage to yeast by a combined addition of NaCl and ethanol when cultivated in lignocellulosic medium such as wood hydrolysate. However, for optimal results, the concentrations of NaCl + ethanol must be adjusted to suit the challenges offered by each hydrolysate.
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| 29. |
- Allander, Susanne Vilhelmsdotter, et al.
(författare)
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Kreatinin fortfarande den vanligaste njurfunktionsanalysen : Undersökning av praxis i Sverige
- 2012
-
Ingår i: Läkartidningen. - 0023-7205 .- 1652-7518. ; 109:19, s. 960-962
-
Tidskriftsartikel (refereegranskat)abstract
- Markers of renal function (glomerular filtration rate; GFR) are frequently used. In most cases GFR is estimated based on plasma creatinine, but cystatin C, creatinine clearance (with urine collection), iohexol clearance and 51Cr-EDTA clearance are also used. A questionnaire was sent to representatives for clinical chemistry laboratories in Sweden to collect information regarding the use of these markers during the years 2006 2009. The aim was to compare the use in different parts of Sweden and how it has changed over time. The overall use of markers of renal function, including creatinine, continues to increase on a national level, with the exception for endogenous creatinine clearance and 51Cr-EDTA clearance. Creatinine, the most frequently used marker, continues to grow in numbers. 5,6 million creatinine analyses and about two hundred thousand cystatin C analyses were performed during year 2009. There were considerable variations between counties in the use of the studied markers.
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| 30. |
-
Allvarlig personlig övertygelse : Om mätningar av samvetet
- 2020
-
Konstnärligt arbete (film/video) (refereegranskat)abstract
- In Serious Personal Conviction – on measurements of conscience, we encounter two groups of people interviewed on different occasions discussing consciousness and ethics in relation to the military system. One of the groups are men that during the 1970s and ‘80s chose to perform non-combatant service and now reflect on the choices they made as 18-year olds. The other group consists of young people of today trying to answer several questions regarding the right to take another person's life. The exposition is part of the artistic research project Refuse to Kill – stories of the conscientious objectors. Our methodology involves a montage of a large number of voices collectively collected through statistical surveys, open-call procedure via advertising in newspapers and the internet, interviews and searches in archives.
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| 31. |
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| 32. |
- Anderson, Johan, 1973, et al.
(författare)
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Fire Spread due to Thermal Runaway in a Lithium-ion Battery Cell
- 2014
-
Ingår i: Fires in vehicles (FIVE) 2014 Conference proceedings. ; 2014, s. 267-270
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The risk of spreading of fire between Lithium-ion battery cells is assessed using Finite-Element (FE) modelling of the heat transfer initiated by a thermal runaway. The results are contrasted to experimental data where the heat release rate (HRR) is utilized as an input to the simulation. It is found that the temperature increase in a neighbouring cell can be quantitatively estimated during theearly stages of the fire taking into account the anisotropic thermal conductivity of the cells.
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| 33. |
- Anderson, Johan, 1973, et al.
(författare)
-
Thermal modeling of fire propagation in lithium-ion batteries
- 2015
-
Ingår i: The 24th International Technical Conference on the Enhanced Safety of Vehicles (ESV). Gothenburg, Sweden on June 8-11, 2015.
-
Konferensbidrag (refereegranskat)abstract
- The objective of the present work is to assess the risk of spreading of fire between Lithium-ion battery cellsinitiated by a thermal runaway. In particular it aims at developing means to predict the temperature of cells inthe vicinity of an overheated cell during the first 5-7 minutes after the thermal event in a Li-ion cell that has anorganic based electrolyte which is flammable. Finite-Element (FE) modelling is used to compute the heattransfer between cells. The spreading model is assessed modeling a scenario where the cells are exposed to a15 kW propane burner. Two different models where utilized, one that considers the conjugate heat transferbetween the surrounding hot gases and the battery cells while the second is a thermal model where theboundary conditions are measured in a mock-up test. The results from the two models are contrasted toexperimental data where the heat release rate (HRR) is utilized as an input to the simulation. It is found thatthe temperature increase in a neighboring cell can be quantitatively estimated in certain cases during the earlystages of the fire taking into account the anisotropic thermal conductivity of the cells using the conjugate heattransfer model. Moreover, the thermal model captures the qualitative behavior of the test results, however, thetemperature increase is slower in the computational model.
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| 34. |
- Andersson, Jenny Marie, et al.
(författare)
-
Effect of cholesterol on the molecular structure and transitions in a clinical-grade lung surfactant extract
- 2017
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 114:18, s. 3592-3601
-
Tidskriftsartikel (refereegranskat)abstract
- The lipid-protein film covering the interface of the lung alveolar in mammals is vital for proper lung function and its deficiency is related to a range of diseases. Here we present a molecular-level characterization of a clinical-grade porcine lung surfactant extract using a multitechnique approach consisting of 1H-13C solid-state nuclear magnetic spectroscopy, small-And wide-Angle X-ray scattering, and mass spectrometry. The detailed characterization presented for reconstituted membranes of a lung extract demonstrates that the molecular structure of lung surfactant strongly depends on the concentration of cholesterol. If cholesterol makes up about 11% of the total dry weight of lung surfactant, the surfactant extract adopts a single liquid-ordered lamellar phase, Lα(o), at physiological temperatures. This Lα(o) phase gradually changes into a liquid-disordered lamellar phase, Lα(d), when the temperature is increased by a few degrees. In the absence of cholesterol the system segregates into one lamellar gel phase and one Lα(d) phase. Remarkably, it was possible to measure a large set of order parameter magnitudes /SCH/ from the liquiddisordered and -ordered lamellar phases and assign them to specific C-H bonds of the phospholipids in the biological extract with no use of isotopic labeling. These findings with molecular details on lung surfactant mixtures together with the presented NMR methodology may guide further development of pulmonary surfactant pharmaceuticals that better mimic the physiological selfassembly compositions for treatment of pathological states such as respiratory distress syndrome.
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| 35. |
- Andersson, J., et al.
(författare)
-
Worse survival for TP53 (p53)-mutated breast cancer patients receiving adjuvant CMF
- 2005
-
Ingår i: Ann Oncol. - : Elsevier BV. - 0923-7534 .- 1569-8041. ; 16:5, s. 743-8
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: TP53 has been described as a prognostic factor in many malignancies, including breast cancer. Whether it also might be a predictive factor with reference to chemo- and endocrine therapy is more controversial. PATIENTS AND METHODS: We investigated relapse-free (RFS), breast cancer-corrected (BCCS) and overall survival (OS) related to TP53 status in node-positive breast cancer patients that had received polychemotherapy [cyclophosphamide, methotrexate, 5-fluorouracil (CMF)] and/or endocrine therapy (tamoxifen). Sequence analyses of the whole TP53 coding region was performed in 376 patients operated on for primary breast cancer with axillary lymph node metastases between 1984 and 1989 (median follow-up time 84 months). RESULTS: TP53 mutations were found in 105 patients (28%). We found 90 (82%) of the 110 mutations in the more frequently analysed exons 5-8, while the other 20 (18%) were located in exons 3-4 and 9-10, respectively. Univariate analyses showed TP53 to be a significant prognostic factor with regard to RFS, BCCS and OS in patients who received adjuvant CMF. CONCLUSIONS: TP53 mutations might induce resistance to certain modalities of breast cancer therapy. Sequence-determined TP53 mutation was of negative prognostic value in the total patient population and in the CMF treated patients.
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| 36. |
- Andersson, Petra, et al.
(författare)
-
Investigation of fire emissions from Li-ion batteries
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents an investigation on gases emitted during Lithium-ion battery fires. Details of the calibration of an FTIR instrument to measure HF, POF3 and PF5 gases are provided as background to the minimum detection limits for each species. The use of FTIR in tests has been verified by repeating experiments reported in the literature. The study reports on gases emitted both after evaporation and after ignition of the electrolyte fumes. Tests were conducted where electrolyte is injected into a propane flame and the influence of the addition of water is studied. Finally three types of battery cells were burnt and emission of fluorine and/or phosphorous containing species quantified.
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| 37. |
- Andersson, Petra, et al.
(författare)
-
Lion Fire: Extinguishment and mitigation of fires in Li-ion batteries at sea
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The shipping industry is facing increasing pressure to cut emissions. Diesel-electric hybrid or fully electrical propulsion systems can offer significant savings in fuel consumption and reduce emissions. However, the use of energy storage battery systems on board vessels is introducing new fire hazards and advice on suitable fire extinguishing systems and agents is desired. In a series of tests, both total compartment application water spray and water mist systems and direct injection (using several different agents) into the module were evaluated in fire tests conducted to compare different fire extinguishing approaches for a fire in a battery cell. A test compartment was constructed to simulate a battery room and a commercially available lithium-ion (Li-ion) battery cell was positioned inside a cubic box that mimicked a battery module. By heating the battery cell, combustible gases were generated, and these gases were ignited by a pilot flame inside the simulated battery module. The tests indicated that fire extinguishment of a battery cell fire inside a battery module is unlikely when using total compartment water spray or water mist fire protection systems. The water droplets are simply not able to penetrate the battery module and reach to the seat of the fire. Direct injection of the fire extinguishing agent inside the battery module is necessary. The tests also showed that agents such as water and low-expansion foam, with a high heat capacity, provide rapid cooling and fire extinguishment. The reduced water surface tension associated with low-expansion foam may improve the possibilities for water penetration whilst agents with a high viscosity may not be able to spread to the seat of the fire. Agents with less heat capacity, such as high-expansion foam and nitrogen gas, provide less cooling but fire extinguishment can still be achieved if designed correctly.
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| 38. |
- Andersson, Petra, et al.
(författare)
-
Modelling of thermal events in Lithium-ion batteries
- 2015
-
Ingår i: ESFSS 2015 2nd European Symposium on Fire Safety Science. 16 - 18 June 2015 European University Cyprus, Cyprus..
-
Konferensbidrag (refereegranskat)abstract
- Lithium-ion batteries are seen as part of the solution to meet the environmental concerns for many areas including the automotive sector. The Li-ion technology has many good properties such as a high energy-density but also drawbacks such as its narrow window of stable operation. If the cell is e.g. heated up it might go into a thermal runaway in which the cell rapidly heats itself up, a process that might spread also to adjacent cells. In order to investigate whether a thermal event will progress to adjacent cells, it is important to be able to model the heat transport within a battery module properly. A first attempt to model the spreading has been made using Comsol Multiphysics for a test case where one cell is exposed to a heating source and then the heating spreads to other cells.
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| 39. |
- Andersson, Petra, et al.
(författare)
-
Using Fourier transform infrared spectroscopy to determine toxic gases in fires with lithium-ion batteries
- 2016
-
Ingår i: Fire and Materials. - : Wiley. - 0308-0501 .- 1099-1018. ; 40:8, s. 999-1015
-
Tidskriftsartikel (refereegranskat)abstract
- Batteries, in particular lithium-ion (Li-ion) batteries, are seen as an alternative to fossil fuels in the automotive sector. Li-ion batteries, however, have some safety issues including possible emissions of toxic fluorine-containing compounds during fire and other abuse situations. This paper demonstrates the possibilities to use the Fourier transform infrared technique to assess some of the most important compounds, including hydrogen fluoride and the far less often measured POF3 and PF5. The study is conducted in the cone calorimeter with different solvents used in Li-ion batteries. The measurements show that, in addition to hydrogen fluoride, with a known high toxicity, POF3 is emitted and can be quantified using Fourier transform infrared.
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| 40. |
- Andersson, Ronny, et al.
(författare)
-
ICT och BIM i japanska byggindustrin
- 2010
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Ingår i: Samhällsbyggaren. - 2000-2408. ; :6, s. 46-51
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Den japanska byggsektorn är ofta ett föredöme för vår egen industris omvandling, t.ex. inom industrialisering och lean. Även när det gäller tillämpning och utveckling av Informations- och Kommunikations- Teknologi, ICT, t.ex. för BIM, ByggnadsInformationsModellering, har man mångårig avancerad erfarenhet som är intressant för oss att ta del av. Samtidig visar det sig att användningen och erfarenheterna av ICT och BIM delvis skiljer sig från motsvarande i Sverige. Detta kunde vi konstatera vid en nyligen genomförd studieresa till Japan som arrangerades av Centrum för Informationsteknik i Samhällsbyggnad, CITS, vid LTH, se även tidigare artikel i nr 3/2010 av Samhällsbyggaren.
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| 41. |
- André, Carl, 1958, et al.
(författare)
-
Detecting population structure in a high gene-flow species, Atlantic herring (Clupea harengus) : direct, simultaneous evaluation of neutral vs putatively selected loci
- 2011
-
Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 106:2, s. 270-280
-
Tidskriftsartikel (refereegranskat)abstract
- In many marine fish species, genetic population structure is typically weak because populations are large, evolutionarily young and have a high potential for gene flow. We tested whether genetic markers influenced by natural selection are more efficient than the presumed neutral genetic markers to detect population structure in Atlantic herring (Clupea harengus), a migratory pelagic species with large effective population sizes. We compared the spatial and temporal patterns of divergence and statistical power of three traditional genetic marker types, microsatellites, allozymes and mitochondrial DNA, with one microsatellite locus, Cpa112, previously shown to be influenced by divergent selection associated with salinity, and one locus located in the major histocompatibility complex class IIA (MHC-IIA) gene, using the same individuals across analyses. Samples were collected in 2002 and 2003 at two locations in the North Sea, one location in the Skagerrak and one location in the low-saline Baltic Sea. Levels of divergence for putatively neutral markers were generally low, with the exception of single outlier locus/sample combinations; microsatellites were the most statistically powerful markers under neutral expectations. We found no evidence of selection acting on the MHC locus. Cpa112, however, was highly divergent in the Baltic samples. Simulations addressing the statistical power for detecting population divergence showed that when using Cpa112 alone, compared with using eight presumed neutral microsatellite loci, sample sizes could be reduced by up to a tenth while still retaining high statistical power. Our results show that the loci influenced by selection can serve as powerful markers for detecting population structure in high gene-flow marine fish species.
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| 42. |
- Anton, Nicholas, et al.
(författare)
-
AXIAL TURBINE DESIGN FOR A TWIN-TURBINE HEAVY-DUTY TURBOCHARGER CONCEPT
- 2018
-
Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : ASME Press. - 9780791851005
-
Konferensbidrag (refereegranskat)abstract
- In the process of evaluating a parallel twin-turbine pulse-turbocharged concept, the results considering the turbine operation clearly pointed towards an axial type of turbine. The radial turbine design first analyzed was seen to suffer from sub-optimum values of flow coefficient, stage loading and blade speed-ratio. Modifying the radial turbine by both assessing the influence of "trim" and inlet tip diameter all concluded that this type of turbine is limited for the concept. Mainly, the turbine stage was experiencing high values of flow coefficient, requiring a more high flowing type of turbine. Therefore, an axial turbine stage could be feasible as this type of turbine can handle significantly higher flow rates very efficiently. Also, the design spectrum is broader as the shape of the turbine blades is not restricted by a radially fibred geometry as in the radial turbine case. In this paper, a single stage axial turbine design is presented. As most turbocharger concepts for automotive and heavy-duty applications are dominated by radial turbines, the axial turbine is an interesting option to be evaluated for pulse charged concepts. Values of crank-angle-resolved turbine and flow parameters from engine simulations are used as input to the design and subsequent analysis. The data provides a valuable insight into the fluctuating turbine operating conditions and is a necessity for matching a pulse-turbocharged system. Starting on a 1D-basis, the design process is followed through, resulting in a fully defined 3D-geometry. The 3D-design is evaluated both with respect to FEA and CFD as to confirm high performance and durability. Turbine maps were used as input to the engine simulation in order to assess this design with respect to "on-engine" conditions and to engine performance. The axial design shows clear advantages with regards to turbine parameters, efficiency and tip speed levels compared to a reference radial design. Improvement in turbine efficiency enhanced the engine performance significantly. The study concludes that the proposed single stage axial turbine stage design is viable for a pulse-turbocharged six cylinder heavy-duty engine. Taking into account both turbine performance and durability aspects, validation in engine simulations, a highly efficient engine with a practical and realizable turbocharger concept resulted.
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| 43. |
- Anton, Nicholas, et al.
(författare)
-
ON THE CHOICE OF TURBINE TYPE FOR A TWIN-TURBINE HEAVY-DUTY TURBOCHARGER CONCEPT
- 2018
-
Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : AMER SOC MECHANICAL ENGINEERS. ; 8
-
Konferensbidrag (refereegranskat)abstract
- In this study, a fundamental approach to the choice of turbocharger turbine for a pulse-charged heavy-duty diesel engine is presented. A standard six-cylinder engine build with a production exhaust manifold and a Twin-scroll turbocharger is used as a baseline case. The engine exhaust configuration is redesigned and evaluated in engine simulations for a pulse-charged concept consisting of a parallel twin-turbine layout. This concept will allow for pulse separation with minimized exhaust pulse interference and low exhaust manifold volume. This turbocharger concept is uncommon, as most previous studies have considered two stage systems, various multiple entry turbine stages etc. Even more rare is the fundamental aspect regarding the choice of turbine type as most manufacturers tend to focus on radial turbines, which by far dominate the turbochargers of automotive and heavy-duty applications. By characterizing the turbine operation with regards to turbine parameters for optimum performance found in literature a better understanding of the limitations of turbine types can be achieved. A compact and low volume exhaust manifold design is constructed for the turbocharger concept and the reference radial turbine map is scaled in engine simulations to a pre-set AFR-target at a low engine RPM. By obtaining crank-angle-resolved data from engine simulations, key turbine parameters are studied with regard to the engine exhaust pulse-train. At the energetic exhaust pressure pulse peak, the reference radial turbine is seen to operate with suboptimum values of Blade-Speed-Ratio, Stage Loading and Flow Coefficient. The study concludes that in order to achieve high turbine efficiency for this pulse-charged turbocharger concept, a turbine with efficiency optimum towards low Blade-Speed Ratios, high Stage Loading and high Flow Coefficient is required. An axial turbine of low degree of reaction-design could be viable in this respect.
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| 44. |
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| 45. |
|
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| 46. |
- Anton, Nicholas, et al.
(författare)
-
Twin-Scroll turbocharger turbine stage evaluation of experimental data and simulations
- 2018
-
Ingår i: Institution of Mechanical Engineers - 13th International Conference on Turbochargers and. - : Institution of Mechanical Engineers. - 9781510873872 ; , s. 487-502
-
Konferensbidrag (refereegranskat)abstract
- In this study a novel comparison of CFD, measured data and a ID-model is presented for a Twin-scroll turbocharger turbine stage. Both full and single admission flow divisions were taken into consideration and shown to represent "on-engine" conditions in the high and low engine rpm range respectively for a heavy-duty 6-cylinder diesel engine. With this in mind, the turbine stage was evaluated for each flow division at several rotational speeds. Both high and low pressure ratios were run. Emphasis is made on high pressure ratios as it is the most relevant case with regards to the energy levels of the exhaust flow. The purpose of the study was to gain insight into the differences and similarities between gas stand measurements, a ID-model and CFD considering performance and turbine stage parameters. The study concludes that the results from the measurements in the gas stand and ID-model, obtained best correlation with the CFD results at low turbine pressure ratios. At high pressure ratios significant deviations were observed. In order to check for discrepancies, both frozen rotor and stage interfaces were considered in the CFD-model, with an additional variant taking the rotor-volute tongue clocking into account. All interfaces resulted in the same trends, although the frozen rotor approach provided the best correlation with measured data. The clocking effect was seen not to affect the results to a great extent in this case. The main difference between the CFD and measurements in combination with the ID model-prediction primarily occur at the rotor inlet. The pressures were predicted to be substantially higher by the CFD calculations due to reduced pressure losses in the volute. Especially taking effect at high turbine pressure ratios which is most relevant for turbocharger applications and therefor the mapping process in the gas stand. This can be one of the reasons for significant deviations in efficiency, turbine parameters etc. at high pressure ratios as effectively more energy will be available to the rotor for a given turbine stage pressure ratio. In general best coherence was achieved for the full admission case. Even so, trends of main parameters such as efficiency, flow capacity and turbine parameters point in the same direction comparing CFD with calculations and measured results for both full and single admission.
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| 47. |
- Apelqvist, Jan, et al.
(författare)
-
Long-term prognosis for diabetic patients with foot ulcers
- 1993
-
Ingår i: Journal of Internal Medicine. - 1365-2796. ; 233:6, s. 485-491
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE. To evaluate the recurrence of foot ulcers as well as the cumulative amputation and mortality rates in diabetic patients with previous foot ulcers. DESIGN. A prospective study of consecutively presenting diabetic patients admitted to the Department of Internal Medicine because of foot ulcer with a median follow-up of 4 years. SETTING. A multidisciplinary foot-care team. POPULATION. Five-hundred-and-fifty-eight consecutive diabetic patients with foot ulcers treated between 1 July 1983 and 31 December 1990 were followed to final outcome. Out of these patients, 468 healed either primarily (n = 345) or after minor or major amputations (n = 123) and 90 died before healing had occurred. Those 468 patients who healed were included in this prospective study from the time of healing. MAIN OUTCOME MEASURES. Patients were followed according to a standardized protocol with registration of foot lesions, amputation, morbidity and mortality. Clinical examination was performed twice yearly. RESULTS. After 1, 3 and 5 years of observation 34%, 61% and 70% of the patients, respectively, had developed a new foot ulcer. The recurrence rate of foot lesions was slightly higher among patients who previously had had an amputation (P < 0.05, P < 0.01 and non-significant, respectively). Among patients with previous primary healing the cumulative amputation rates were 3%, 10% and 12% after 1, 3 and 5 years of follow-up compared with 13%, 35% and 48% among those who previously healed after amputation, irrespective of previous amputation level (P < 0.001 at all time-points). All amputations except three were initiated by a foot ulcer deteriorating to deep infection or progressive gangrene. The long-term survival ratio was lower among patients healed after previous amputation (80%, 59%, 27%) compared with patients with previously primary healing (92%, 73%, 58%) after 1, 3 and 5 years of observation, respectively (P < 0.001, P < 0.01 and P < 0.001 respectively). The mortality rate was twice as high among primarily healed and four times as high among patients with amputation compared to an age- and sex-matched Swedish population. CONCLUSION. These findings stress the need for life-long surveillance of the diabetic foot at risk and the necessity of preventive foot care among diabetic patients with previous foot lesions, and particularly among those who had had a previous amputation.
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| 48. |
- Apelqvist, Jan, et al.
(författare)
-
Medical risk factors in diabetic patients with foot ulcers and severe peripheral vascular disease and their influence on outcome
- 1992
-
Ingår i: Journal of Diabetes and its Complications. - 1873-460X. ; 6:3, s. 167-174
-
Tidskriftsartikel (refereegranskat)abstract
- The association between medical risk factors and the outcome of foot ulcers was evaluated in 208 consecutive diabetic patients with severe peripheral vascular disease (systolic toe blood pressure < or = 45 mm Hg). All patients were treated and followed by the same foot care team. Eighty patients healed primarily, 83 healed after a minor or major amputation, and 45 died. The systolic toe blood pressure was higher among primary healed (30 +/- 13 mm Hg) compared with amputated (22 +/- 15 mm Hg; p < 0.001) and deceased patients (20 +/- 14 mm Hg; p < 0.001). The patients were comparable regarding age, sex, and diabetes and wound duration. Only 41 (19%) patients had intermitten claudication, whereas 153 (77%) lacked palapble pedal pulses, 36% of whom healed primarily. Rest pain occurred in 72 (33%) patients, 38 (47%) of whom had an amputation and 18 (25%) who healed primarily (p < 0.01). Peripheral edema and proteinuria were more common among patients who healed after amputation compared with those who healed primarily (p < 0.001 and p < 0.01, respectively). Signs of sensory neuropathy were found in 158 (77%) patients. There were no differences concerning cardiovascular disease, smoking habits, or short-term metabolic control between patients who healed primarily or after an amputation. In conclusion, diabetic patients with foot ulcers and severe peripheral vascular disease with low systolic toe blood pressure were not excluded from the possibility of primary healing. The most important risk factors for amputation were a systolic toe pressure of less than 30 mm Hg, peripheral edema, rest pain, and proteinuria.
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| 49. |
- Apelqvist, Jan, et al.
(författare)
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Prognostic value of systolic ankle and toe blood pressure levels in outcome of diabetic foot ulcer
- 1989
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Ingår i: Diabetes Care. - : American Diabetes Association. - 1935-5548 .- 0149-5992. ; 12:6, s. 373-378
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Tidskriftsartikel (refereegranskat)abstract
- The prognostic value of distal blood pressure measurements has been studied in 314 consecutive diabetic patients with foot ulcers. Systolic toe blood pressure was measured with a strain-gauge technique, and ankle pressure was measured with strain-gauge or Doppler techniques. Wound healing was defined as intact skin for at least 6 mo. One hundred ninety-seven patients healed primarily, 77 had amputations, and 40 died before healing had occurred. In 294 of 300 patients, it was possible to measure either ankle or toe pressure. Fourteen patients were not available for pressure measurements. Of these, 10 patients healed primarily, and 4 died before healing occurred. Both ankle and toe pressures were higher (P less than .001) among patients who healed without amputation compared with those who underwent amputation or died before healing. No differences were seen in ankle or toe pressure levels among those who had amputations or died. No patient healed primarily with an ankle pressure less than 40 mmHg. An upper limit above which amputation was not required could not be defined. Primary healing was achieved in 139 of 164 patients (85%) with a toe pressure level greater than 45 mmHg, whereas 43 of 117 patients (36%; P less than .001) healed without amputation when toe pressure was less than or equal to 45 mmHg. In conclusion, a combination of ankle and toe pressure measurements is a useful tool to predict primary healing in diabetic foot ulcers.
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- Apelqvist, Jan, et al.
(författare)
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The importance of peripheral pulses, peripheral oedema and local pain for the outcome of diabetic foot ulcers
- 1990
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Ingår i: Diabetic Medicine. - 1464-5491. ; 7:7, s. 590-594
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Tidskriftsartikel (refereegranskat)abstract
- In a prospective study, peripheral pulses, claudication, peripheral oedema, and rest pain were evaluated in 314 sequentially presenting diabetic patients with foot ulcers. In the ulcerated limb pedal pulses were found to be present in 44% of the patients, peripheral oedema in 38%, and rest pain in 19%. Twelve per cent had claudication. Presence of pedal pulses was more common in patients whose ulcers underwent primary healing (56%) than in those who healed after amputation (23%) or died (25%, p less than 0.001). Eighty per cent of the patients with pedal pulses present underwent primary healing. However, 49% of patients with absence of pedal pulses also underwent primary healing and 12 patients developed gangrene despite presence of pedal pulses. Peripheral oedema was more common in patients who required amputation (58%) or died (55%) than in patients with primary healing (26%, p less than 0.001). A tentative predisposing factor was identified in 95% of the patients, the most common factors being neuropathy, congestive heart failure, and previous deep venous thrombosis. Rest pain was more common in patients who required amputation (48%) or died (23%) than in those with primary healing (7%; p less than 0.001). Only 50% of patients with gangrene had rest pain and of these patients, only one underwent primary healing. The presence of pedal pulses, oedema, and rest pain give valuable but imperfect information on the possible primary healing of foot ulcers in diabetic patients.
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