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Sökning: WFRF:(Gustafsson Mats) > (2010-2013)

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1.
  • Nordebo, Sven, et al. (författare)
  • Electromagnetic dispersion modeling and measurements for HVDC power cables
  • 2011
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • This paper provides a general framework for electromagnetic modeling, computation and measurements regarding the wave propagation characteristics of High-Voltage Direct Current (HVDC) power cables. The modeling is focused on very long (10 km or more) HVDC power cables and the relevant frequency range is therefore in the low-frequency regime of about 0-100 kHz. An exact dispersion relation is formulated together with a discussion on practical aspects regarding the computation of the propagation constant and the related characteristic impedance. Experimental time-domain measurement data from an 80 km long HVDC power cable is used to validate the model. It is concluded that a single-mode transmission line model is not adequate to account for the mismatch between the power cable and the instrumentation. A mismatch calibration procedure is therefore devised to account for the connection between the measurement equipment and the cable. A dispersion model is thus obtained that is accurate for early times of pulse arrival. To highlight the potential of accurate electromagnetic modeling, an example of high-resolution length-estimation is discussed and analyzed using statistical methods based on the Cramer-Rao lower bound. The analysis reveals that the estimation accuracy based on the present model (and its related model error) is in the order of 100 m for an 80 km long power cable, and that the potential accuracy using a perfect model based on the given measurement data is in the order of centimeters.
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2.
  • Nordebo, Sven, et al. (författare)
  • Low-frequency dispersion characteristics of a multilayered coaxial cable
  • 2013
  • Ingår i: Journal of Engineering Mathematics. - : Springer Netherlands. - 0022-0833 .- 1573-2703. ; 83:1, s. 169-184
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper provides an exact asymptotic analysis regarding the low-frequency dispersion characteristics of a multilayered coaxial cable. A layer-recursive description of the dispersion function is derived that is well suited for asymptotic analysis. The recursion is based on two well-behaved (meromorphic) subdeterminants defined by a perfectly electrically conducting (PEC) and a perfectly magnetically conducting termination, respectively. For an open waveguide structure, the dispersion function is a combination of two such functions, and there is only one branch point that is related to the exterior domain. It is shown that if there is one isolating layer and a PEC outer shield, then the classical Weierstrass preparation theorem can be used to prove that the low-frequency behavior of the propagation constant is governed by the square root of the complex frequency, and an exact analytical expression for the dominating term of the asymptotic expansion is derived. It is furthermore shown that the same asymptotic expansion is valid to its lowest order even if the outer shield has finite conductivity and there is an infinite exterior region with finite nonzero conductivity. As a practical application of the theory, a high-voltage direct current (HVDC) power cable is analyzed and a numerical solution to the dispersion relation is validated by comparisons with the asymptotic analysis. The comparison reveals that the low-frequency dispersion characteristics of the power cable is very complicated and a first-order asymptotic approximation is valid only at extremely low frequencies (below 1 Hz). It is noted that the only way to come to this conclusion is to actually perform the asymptotic analysis. Hence, for practical modeling purposes, such as with fault localization, an accurate numerical solution to the dispersion relation is necessary and the asymptotic analysis is useful as a validation tool.
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4.
  • Nordebo, Sven, et al. (författare)
  • Wave modeling and fault localization for underwater power cables
  • 2011
  • Ingår i: 2011 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC). - : IEEE Press. - 9781457700460 ; , s. 698-701
  • Konferensbidrag (refereegranskat)abstract
    • This paper describes some preliminary results regarding Time-Domain pulse Reflection (TDR) measurements and modeling performed on the Baltic Cable submarine HVDC link between southern Sweden and northern Germany. The measurements were conducted in collaboration between the Linnaeus University, Lund University, Baltic Cable AB and ABB High Voltage Cables AB, and is part of the research project: “Fundamental wave modeling for signal estimation on lossy transmission lines”. Preliminary results on measurements and modeling are included here, as well as a first numerical study regarding the low-frequency dispersion characteristics of power cables. The numerical study shows that the finite conductivity of the cable lead shield has a great impact on the losses at low frequencies (0-1 kHz), and that the low-frequency asymptotics of the propagation constant is consistent with common propagation models based on the skin-effect.
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5.
  • Gustafsson, Jan-Eric, 1949, et al. (författare)
  • School, Learning and Mental Health : A systematic review
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Rapporten presenterar resultaten från en systematisk översikt av forskning om skola, lärande och barns psykiska hälsa. Kungliga Vetenskapsakademiens Hälsoutskottet har givit uppdraget att genomföra en sådan översikt till en arbetsgrupp som har arbetat med uppdraget från hösten 2008 till mars 2009. Det första syftet med översikten är att genomföra en kartläggning av forskning inom det breda fält som behandlar frågor om skola, lärande och barns och ungdomars psykiska hälsa. Det andra syftet är att genomföra en narrativ syntes av forskning som undersökt orsaksförhållanden mellan psykisk hälsa å ena sidan och skolresultat och lärande å den andra sidan. Det tredje syftet är att redovisa resultat från forskning som har studerat svenska barns och ungdomars erfarenheter och upplevelser av skola och undervisningssituationer. För att uppnå de första två syftena genomfördes systematiska litteratursökningar i bibliografiska databaser av artiklar publicerade i vetenskapliga internationella tidskrifter inom olika discipliner. Det tredje syftet undersöktes med litteratursökningar av kvalitativa svenska studier i bibliografiska databaser. Slutsatser På grundval dels av kartläggningen av forskning om skola, lärande och psykisk hälsa, dels av de två fördjupade översikterna kan följande slutsatser dras: • Omfattningen av forskning som undersöker relationerna mellan olika aspekter av skola och psykisk hälsa är begränsad och i synnerhet gäller detta forskning som undersöker organisationsfaktorer och undervisnings-faktorer, aktiviteter, läroplaners utformning, resurser, specialpedagogiskt stöd, och olika former av betyg och bedömning. • Tidiga svårigheter i skolan och i synnerhet läs- och skrivsvårigheter kan orsaka internaliserande och externaliserande psykiska problem. • Svårigheter i skola och psykiska problem tenderar att vara stabila över tid. • Skolrelaterade hälsoproblem tenderar att minska när eleverna börjar på gymnasiet och får tillgång till nya områden av aktiviteter, roller och valmöjligheter. • Att genomföra stora ansträngningar utan att detta leder till resultat är relaterat till utveckling av depression. Problem i skolan med skolresultat och prestationer orsakar inter-naliserande symptom för flickor under tonåren. • Det finns samband mellan olika typer av psykiska problem och de är också relaterade till ett brett spektrum av somatiska och psykosomatiska symptom. • Internaliserande och externaliserande psykiska problem har negativa effekter på skolprestationer genom mekanismer som är delvis ålders- och genusspecifika. • Kompetenser och prestationer i skolan är relaterade till psykisk hälsa. • Goda resultat i skolan har en positiv effekt på självuppfattning. • En god självuppfattning bidrar inte direkt till bättre resultat, men andra faktorer som är relaterade till självuppfattning (motivation och upplevd inre/yttre kontroll) påverkar lärande och resultat • Relationer med klasskamrater och lärare bidrar till processer som kopplar skolmisslyckande till psykisk ohälsa. Relationer med kamrater och lärare kan också skydda mot utvecklingen av psykiska problem. • Jämförelser med klasskamrater påverkar självuppfattningen, med effekter som varierar beroende på gruppsammansättning och typ av skola.
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6.
  • Karlsson, Helen, et al. (författare)
  • Wear Particles from Studded Tires and Granite Pavement Induce Pro-inflammatory Alterations in Human Monocyte-Derived Macrophages : A Proteomic Study.
  • 2011
  • Ingår i: Chemical Research in Toxicology. - : American Chemical Society. - 0893-228X .- 1520-5010. ; 24, s. 45-53
  • Tidskriftsartikel (refereegranskat)abstract
    • Airborne particulate matter is considered to be one of the environmental contributors to the mortality in cancer, respiratory, and cardiovascular diseases. For future preventive actions, it is of major concern to investigate the toxicity of defined groups of airborne particles and to clarify their pathways in biological tissues. To expand the knowledge beyond general inflammatory markers, this study examined the toxicoproteomic effects on human monocyte derived macrophages after exposure to wear particles generated from the interface of studded tires and a granite-containing pavement. As comparison, the effect of endotoxin was also investigated. The macrophage proteome was separated using two-dimensional gel electrophoresis. Detected proteins were quantified, and selected proteins were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry. Among analyzed proteins, seven were significantly decreased and three were increased by exposure to wear particles as compared to unexposed control cells. Endotoxin exposure resulted in significant changes in the expression of six proteins: four decreased and two increased. For example, macrophage capping protein was significantly increased after wear particle exposure only, whereas calgizzarin and galectin-3 were increased by both wear particle and endotoxin exposure. Overall, proteins associated with inflammatory response were increased and proteins involved in cellular functions such as redox balance, anti-inflammatory response, and glycolysis were decreased. Investigating the effects of characterized wear particles on human macrophages with a toxicoproteomic approach has shown to be useful in the search for more detailed information about specific pathways and possible biological markers.
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7.
  • Milani, Lili, et al. (författare)
  • DNA methylation for subtype classification and prediction of treatment outcome in patients with childhood acute lymphoblastic leukemia.
  • 2010
  • Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 115:6, s. 1214-25
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite improvements in the prognosis of childhood acute lymphoblastic leukemia (ALL), subgroups of patients would benefit from alternative treatment approaches. Our aim was to identify genes with DNA methylation profiles that could identify such groups. We determined the methylation levels of 1320 CpG sites in regulatory regions of 416 genes in cells from 401 children diagnosed with ALL. Hierarchical clustering of 300 CpG sites distinguished between T-lineage ALL and B-cell precursor (BCP) ALL and between the main cytogenetic subtypes of BCP ALL. It also stratified patients with high hyperdiploidy and t(12;21) ALL into 2 subgroups with different probability of relapse. By using supervised learning, we constructed multivariate classifiers by external cross-validation procedures. We identified 40 genes that consistently contributed to accurate discrimination between the main subtypes of BCP ALL and gene sets that discriminated between subtypes of ALL and between ALL and controls in pairwise classification analyses. We also identified 20 individual genes with DNA methylation levels that predicted relapse of leukemia. Thus, methylation analysis should be explored as a method to improve stratification of ALL patients. The genes highlighted in our study are not enriched to specific pathways, but the gene expression levels are inversely correlated to the methylation levels.
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8.
  • Nordlund, Jessica, et al. (författare)
  • Genome-wide signatures of differential DNA methylation in pediatric acute lymphoblastic leukemia
  • 2013
  • Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 14:9, s. r105-
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND:Although aberrant DNA methylation has been observed previously in acute lymphoblastic leukemia (ALL), the patterns of differential methylation have not been comprehensively determined in all subtypes of ALL on a genome-wide scale. The relationship between DNA methylation, cytogenetic background, drug resistance and relapse in ALL is poorly understood.RESULTS:We surveyed the DNA methylation levels of 435,941 CpG sites in samples from 764 children at diagnosis of ALL and from 27 children at relapse. This survey uncovered four characteristic methylation signatures. First, compared with control blood cells, the methylomes of ALL cells shared 9,406 predominantly hypermethylated CpG sites, independent of cytogenetic background. Second, each cytogenetic subtype of ALL displayed a unique set of hyper- and hypomethylated CpG sites. The CpG sites that constituted these two signatures differed in their functional genomic enrichment to regions with marks of active or repressed chromatin. Third, we identified subtype-specific differential methylation in promoter and enhancer regions that were strongly correlated with gene expression. Fourth, a set of 6,612 CpG sites was predominantly hypermethylated in ALL cells at relapse, compared with matched samples at diagnosis. Analysis of relapse-free survival identified CpG sites with subtype-specific differential methylation that divided the patients into different risk groups, depending on their methylation status.CONCLUSIONS:Our results suggest an important biological role for DNA methylation in the differences between ALL subtypes and in their clinical outcome after treatment.
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9.
  • Strandberg, Gunnar, et al. (författare)
  • Analysis of intraosseous samples using point of care technology : an experimental study in the anaesthetised pig
  • 2012
  • Ingår i: Resuscitation. - : Elsevier BV. - 0300-9572 .- 1873-1570. ; 83:11, s. 1381-1385
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND:Intraosseous access is an essential method in emergency medicine when other forms of vascular access are unavailable and there is an urgent need for fluid or drug therapy. A number of publications have discussed the suitability of using intraosseous access for laboratory testing. We aimed to further evaluate this issue and to study the accuracy and precision of intraosseous measurements.METHODS:Five healthy, anaesthetised pigs were instrumented with bilateral tibial intraosseous cannulae and an arterial catheter. Samples were collected hourly for 6h and analysed for blood gases, acid base status, haemoglobin and electrolytes using an I-Stat(®) point of care analyser.RESULTS: There was no clinically relevant difference between results from left and right intraosseous sites. The variability of the intraosseous sample values, measured as the coefficient of variance (CV), was maximally 11%, and smaller than for the arterial sample values for all variables except SO(2). For most variables, there seems to be some degree of systematic difference between intraosseous and arterial results. However, the direction of this difference seems to be predictable.CONCLUSION: Based on our findings in this animal model, cartridge based point of care instruments appear suitable for the analysis of intraosseous samples. The agreement between intraosseous and arterial analysis seems to be good enough for the method to be clinically useful. The precision, quantified in terms of CV, is at least as good for intraosseous as for arterial analysis. There is no clinically important difference between samples from left and right tibia, indicating a good reproducibility.
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10.
  • Ågren, Thomas, et al. (författare)
  • Effective Connectivity of Fear Circuitry and Emotion Regulation in Specific Phobia
  • 2011
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Background: The aim of the present study was to characterize effective brain connectivity patterns in patients with specific phobia. Methods: Sixteen patients with specific phobia were exposed to phobic and fear-relevant but non-phobic stimuli while regional cerebral blood flow was measured using [15O]-labelled water and positron emission tomography. Self reported state anxiety was also evaluated using the Spielberger State Anxiety Inventory (STAI-S). Different connectivity architectures were built based on five regions of interest (ROIs): the amygdala; subgenual anterior cingulate cortex (sACC) area 25; anterior midcingulate cortex (aMCC) area 24; insular cortex and dorsolateral prefrontal cortex (DLPFC) area 8. The ROIs were chosen based on their role in generating and attenuating fear. Structural equations modelling and Bayesian inference were used to assign probabilities to all possible architectures. Results: Top ranking models reveal different connectivity patterns resulting from phobic and non-phobic exposure. When exposed to phobic stimuli sACC appear to be driving the network. In contrast, when exposed to non-phobic stimuli the DLPFC is more active and dampen amygdala activity. This could reflect successful reappraisal processes during non-phobic exposure. The DLPFC correlated negatively (r=-0.49) with STAI-S during non-phobic exposure, but not phobic exposure also suggesting that emotional regulation fails in phobia. No direct correlation between amygdala activity and STAI-S was evident during either phobic or non-phobic conditions. Conclusions: These results suggest that emotional control processes operative when exposed to fear-relevant, but non-phobic cues are impaired during exposure to phobic stimuli.
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