| 1. |
- Johansson, Fredrik, 1974-
(författare)
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Essays on Measurement Error and Nonresponse
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Essay 1 deals with measurement errors. Matching survey data with administrative records provides unique opportunities to evaluate the statistical properties of respondents' answers. This paper focuses primarily on home ownership and wealth variables. For all analyzed variables we find that the classical assumption of no correlation between measurement error and true value is violated. In an empirical application explaining the housing tenure choice, LPM and Probit models are estimated using both survey and register data on gross financial wealth.Essay 2 (with N. Anders Klevmarken) also analyzes measurement errors. Survey measures of wealth are error prone with a relatively large error variance. The errors are not uncorrelated with the true values but tend to have a negative correlation, which implies that wealthy people tend to under-report and less wealthy to over-report their responses. There is no general tendency of survey data to under-estimate mean wealth with the exception of the last percentile. The under-estimate of the wealth of the very rich is however not due to under-reporting but rather to selective nonresponse. Using simple models this paper discusses consequences of error prone wealth data.Essay 3 (with N. Anders Klevmarken) studies the problem of nonresponse in survey data. Using rich register data to analyze response behavior in a survey on health and economic standard, a model to explain contact and participation probabilities is estimated. Previous attempts to build such models have been constrained by the very limited information available in the sampling frames. One main result is that both probabilities are lower among respondents out of the labor market, who are immigrants and on benefits.Essay 4 analyzes different approaches to adjust for nonresponse bias. When a survey response mechanism depends on the variable of interest measured within the same survey and observed for only part of the sample, the situation is one of nonignorable nonresponse. If the nonresponse is ignored it will most likely generate significant bias in the estimates of the model parameters of interest. To solve this, one option is the joint modelling of the response mechanism and the variable of interest. Another option is to calibrate each observation with weights constructed from auxiliary data. In an application where earnings equations are estimated these approaches are all applied and compared with reference estimates. These reference estimates are based on a large data set without any nonresponse.
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| 2. |
- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Alm, Rikard, et al.
(författare)
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Detection and identification of protein isoforms using cluster analysis of MALDI-MS mass spectra
- 2006
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Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 5:4, s. 785-792
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Tidskriftsartikel (refereegranskat)abstract
- We describe an approach to screen large sets of MALDI-MS mass spectra for protein isoforms separated on two-dimensional electrophoresis gels. Mass spectra are matched against each other by utilizing extracted peak mass lists and hierarchical clustering. The output is presented as dendrograms in which protein isoforms cluster together. Clustering could be applied to mass spectra from different sample sets, dates, and instruments, revealed similarities between mass spectra, and was a useful tool to highlight peptide peaks of interest for further investigation. Shared peak masses in a cluster could be identified and were used to create novel peak mass lists suitable for protein identification using peptide mass fingerprinting. Complex mass spectra consisting of more than one protein were deconvoluted using information from other mass spectra in the same cluster. The number of peptide peaks shared between mass spectra in a cluster was typically found to be larger than the number of peaks that matched to calculated peak masses in databases, thus modified peaks are probably among the shared peptides. Clustering increased the number of peaks associated with a given protein.
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| 4. |
- Aulchenko, Yurii S, et al.
(författare)
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Loci influencing lipid levels and coronary heart disease risk in 16 European population cohorts
- 2009
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 41:1, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- Recent genome-wide association (GWA) studies of lipids have been conducted in samples ascertained for other phenotypes, particularly diabetes. Here we report the first GWA analysis of loci affecting total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol and triglycerides sampled randomly from 16 population-based cohorts and genotyped using mainly the Illumina HumanHap300-Duo platform. Our study included a total of 17,797-22,562 persons, aged 18-104 years and from geographic regions spanning from the Nordic countries to Southern Europe. We established 22 loci associated with serum lipid levels at a genome-wide significance level (P < 5 x 10(-8)), including 16 loci that were identified by previous GWA studies. The six newly identified loci in our cohort samples are ABCG5 (TC, P = 1.5 x 10(-11); LDL, P = 2.6 x 10(-10)), TMEM57 (TC, P = 5.4 x 10(-10)), CTCF-PRMT8 region (HDL, P = 8.3 x 10(-16)), DNAH11 (LDL, P = 6.1 x 10(-9)), FADS3-FADS2 (TC, P = 1.5 x 10(-10); LDL, P = 4.4 x 10(-13)) and MADD-FOLH1 region (HDL, P = 6 x 10(-11)). For three loci, effect sizes differed significantly by sex. Genetic risk scores based on lipid loci explain up to 4.8% of variation in lipids and were also associated with increased intima media thickness (P = 0.001) and coronary heart disease incidence (P = 0.04). The genetic risk score improves the screening of high-risk groups of dyslipidemia over classical risk factors.
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| 5. |
- Bishop, Kevin, et al.
(författare)
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The Effects of Forestry on Hg Bioaccumulation in Nemoral/Boreal Waters and Recommendations for Good Silvicultural Practice
- 2009
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:7, s. 373-380
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Tidskriftsartikel (refereegranskat)abstract
- Mercury (Hg) levels are alarmingly high in fish from lakes across Fennoscandia and northern North America. The few published studies on the ways in which silviculture practices influence this problem indicate that forest operations increase Hg in downstream aquatic ecosystems. From these studies, we estimate that between one-tenth and one-quarter of the Hg in the fish of high-latitude, managed forest landscapes can be attributed to harvesting. Forestry, however, did not create the elevated Hg levels in the soils, and waterborne Hg/MeHg concentrations downstream from harvested areas are similar to those from wetlands. Given the current understanding of the way in which silviculture impacts Hg cycling, most of the recommendations for good forest practice in Sweden appear to be appropriate for high-latitude regions, e.g., leaving riparian buffer zones, as well as reducing disturbance at stream crossings and in moist areas. The recommendation to restore wetlands and reduce drainage, however, will likely increase Hg/MeHg loadings to aquatic ecosystems
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| 6. |
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| 7. |
- Davidsson, Josef, et al.
(författare)
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Tiling resolution array comparative genomic hybridization, expression and methylation analyses of dup(1q) in Burkitt lymphomas and pediatric high hyperdiploid acute lymphoblastic leukemias reveal clustered near-centromeric breakpoints and overexpression of genes in 1q22-32.3
- 2007
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 16:18, s. 2215-2225
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Tidskriftsartikel (refereegranskat)abstract
- Although gain of 1q occurs in 25% of Burkitt lymphomas (BLs) and 10% of pediatric high hyperdiploid acute lymphoblastic leukemias (ALLs), little is known about the origin, molecular genetic characteristics and functional outcome of dup(1q) in these disorders. Ten dup(1q)-positive BLs/ALLs were investigated by tiling resolution (32k) array CGH analysis, which revealed that the proximal breakpoints in all cases were near-centromeric, in eight of them clustering within a 1.4 Mb segment in 1q12-21.1. The 1q distal breakpoints were heterogeneous, being more distal in the ALLs than in the BLs. The minimally gained segments in the ALLs and BLs were 57.4 Mb [dup(1)(q22q32.3)] and 35 Mb [dup(1)(q12q25.2)], respectively. Satellite 11 DNA on 1q was not hypomethylated, as ascertained by Southern blot analyses of 15 BLs/ALLs with and without gain of 1q, indicating that aberrant methylation was not involved in the origin of dup(1q), as previously suggested for other neoplasms with 1q rearrangements. Global gene expression analyses revealed that five genes in the minimally 57.4 Mb gained region-B4GALT3, DAP3, RGS16, TMEM183A and UCK2-were significantly overexpressed in dup(1q)-positive ALLs compared with high hyperdiploid ALLs without dup(1q). The DAP3 and UCK2 genes were among the most overexpressed genes in the BL case with gain of 1q investigated. The DAP3 protein has been reported to be highly expressed in invasive glioblastoma multiforme cells, whereas expression of the UCK2 protein has been correlated with sensitivity to anticancer drugs. However, involvement of these genes in dup(1q)-positive ALLs and BLs has previously not been reported.
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| 8. |
- Hylander, Lars Daniel, 1954-, et al.
(författare)
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Zero mercury emission strategy in Sweden.
- 2008
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Ingår i: NIMD Forum 2008. Mercury Recycling and Environmental Monitoring for a Sustainable Society. - Minamata City, Kumamoto, Japan. : Ministry of the Environment, Japan, National Institute for Minamata Disease. ; , s. 16-27
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mercury (Hg) is of world-wide concern because of its toxicity not only to humans but also to other higher forms of life as well as microorganisms in natural environments. Methyl-Hg is the species of particular concern for birds, fish and mammals, where biomagnification in long food chains results in hazardous exposure of top predators including humans. Elemental Hg is transformed to methyl-Hg in nature by processes difficult to control, and any emission of inorganic Hg will ultimately result in increased levels of methyl-Hg in our environment. Restricting anthropogenic emissions of Hg is thus a priority for counteracting an increase of methyl-Hg levels in biota. To eliminate the sources is a cost-effective way of eliminating related emissions. There are three primary sources of anthropogenic Hg emissions: 1.) combustion of fossil fuels; 2.) dedicated mining of Hg; and 3.) refining processes and mining of minerals for recovering of other elements than Hg. Mercury produced by mining and refining is used in a wide variety of products such as thermometers, dental amalgam, lamps, and batteries, resulting in Hg emissions at production, usage, and disposal. Swedish authorities were first to act by enforcing nationwide legislation against the use of Hg, to avoid tragedies such as those in Minamata, Japan. Consequently, seed dressing with methyl-Hg was prohibited in 1966, and fenyl-Hg in slimicides was prohibited in 1967. Total emissions of Hg from Swedish chlor-alkali plants to air and waters were reduced from more than 30 t per year in the 1950’s and 1960’s to less than 0.1 t nowadays. Sale of clinical thermometers containing Hg is prohibited since 1992, and Hg exports are banned since 1997. A general ban on the use of Hg in processes and products is presently considered by the government. From the ban there will be exceptions only where Hg free alternatives still have a limited market share, such as energyefficient lamps. Recycling of Hg is discouraged in Sweden, since continued use of Hg-containing products inevitably results in losses of Hg to air, soil and water, thus adding to the risks of human exposure. Mercury-containing equipments, products, and waste are instead collected for permanent disposal in a safe deep-bedrock repository with minimal losses. This has by Swedish authorities been considered as the only feasible solution to obtain zero Hg emissions from the Swedish technosphere. Further information may be obtained from the Swedish Chemicals Agency (www.kemi.se) and the Swedish Environmental Protection Agency (www.naturvardsverket.se).
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| 9. |
- Johansson, Markus, 1978
(författare)
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Complex source modeling for electromagnetic dosimetry
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electromagnetic modeling of complex sources is useful in dosimetry applications as well as for near-field to far-field transformations and antennadiagnostics. In order to determine whether exposure safety guidelines, such as the EU directive 2004/40/EC, are complied with, it is important to be able tomodel the field distribution from electromagnetic sources.Two methods of determining the total field, including phase information, when only field amplitudes have been measured on a set of planes in front of an electromagnetic source have been developed. The first method, the adjoint field method, is a gradient based optimization algorithm based on the adjoint fields. The second method, the phase angle gradient method, employs an optimization algorithm based on the phase angle gradients of a functional.The methods have been tested with numerical test cases. The adjoint field method is functioning well in 2D and the phase angle gradient method gives good results for 3D test cases. The phase angle gradient method was also tested for measured magnetic flux density with low frequency from a transformer and for electric field with high frequency from a mobile phone. For the cases with measured field the obtained phase angles on the measurement plane closest to the source gave calculated field on other measurement planes that agrees well with measured field.The developed methods are useful for coupling of measured field amplitudes in front of a source, to numerical calculations of the fields inside humans.
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| 10. |
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