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- 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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- Meyer-Jacob, Carsten, 1984-
(författare)
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Infrared spectroscopy as a tool to reconstruct past lake-ecosystem changes : Method development and application in lake-sediment studies
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Natural archives such as lake sediments allow us to assess contemporary ecosystem responses to climate and environmental changes in a long-term context beyond the few decades to at most few centuries covered by monitoring or historical data. To achieve a comprehensive view of the changes preserved in sediment records, multi-proxy studies – ideally in high resolution – are necessary. However, this combination of including a range of analyses and high resolution constrains the amount of material available for analyses and increases the analytical costs. Infrared spectroscopic methods are a cost-efficient alternative to conventional methods because they offer a) a simple sample pre-treatment, b) a rapid measurement time, c) the non- or minimal consumption of sample material, and d) the potential to extract quantitative and qualitative information about organic and inorganic sediment components from a single measurement.The main objective of this doctoral thesis was twofold. The first part was to further explore the potential of Fourier transform infrared (FTIR) and visible-near infrared (VNIR) spectroscopy in paleolimnological studies as a) an alternative tool to conventional methods for quantifying biogenic silica (bSi) – a common proxy of paleoproductivity in lakes – in sediments and b) as a tool to infer past lake-water total organic carbon (TOC) levels from sediments. In a methodological study, I developed an independent application of FTIR spectroscopy and PLS modeling for determining bSi in sediments by using synthetic sediment mixtures with known bSi content. In contrast to previous models, this model is independent from conventional wet-chemical techniques, which had thus far been used as the calibration reference, and their inherent measurement uncertainties. The second part of the research was to apply these techniques as part of three multi-proxy studies aiming to a) improve our understanding of long-term element cycling in boreal and arctic landscapes in response to climatic and environmental changes, and b) to assess ongoing changes, particularly in lake-water TOC, on a centennial to millennial time scale.In the first applied study, high-resolution FTIR measurements of the 318-m long sediment record of Lake El’gygytgyn provided a detailed insight into long-term climate variability in the Siberian Arctic over the past 3.6 million years. Highest bSi accumulation occurred during the warm middle Pliocene (3.6-3.3 Ma), followed by a gradual but variable decline, which reflects the first onset of glacial periods and then the finally full establishment of glacial–interglacial cycles during the Quaternary. The second applied study investigated the sediment record of Torneträsk in subarctic northern Sweden also in relation to climate change, but only over the recent post-glacial period (~10 ka). By comparing responses to past climatic and environmental forcings that were recorded in this large-lake system with those recorded in small lakes from its catchment, I determined the significance and magnitude of larger-scale changes across the study region. Three different types of response were identified over the Holocene: i) a gradual response to the early landscape development following deglaciation (~10000-5300 cal yr BP); ii) an abrupt but delayed response following climate cooling during the late Holocene, which occurred c. 1300 cal yr BP – about 1000-2000 years later than in smaller lakes from the area; and iii) an immediate response to the ongoing climate change during the past century. The rapid, recent response in a previously rather insensitive lake-ecosystem emphasizes the unprecedented scale of ongoing climate change in northern Fennoscandia. In the third applied study, VNIR-inferred lake-water TOC concentrations from lakes across central Sweden showed that the ongoing, observed increase in surface water TOC in this region was in fact preceded by a long-term decline beginning already AD 1450-1600. These dynamics coincided with early human land use activities in the form of widespread summer forest grazing and farming that ceased over the past century. The results of this study show the strong impact of past human activities on past as well as ongoing TOC levels in surface waters, which has thus far been underestimated. The research in this thesis demonstrates that infrared spectroscopic methods can be an essential component in high-resolution, multi-proxy studies of past environmental and climate changes.
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- Anderson, Pia
(författare)
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Textuell makt : Fem gymnasieelever läser och skriver i svenska och samhällskunskap
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis was to study how five students linguistically express textual power in conversation and writing about reading, as well as to investigate their possibilities to linguistically express textual power. The study was performed within some of the literacy practices in the subjects of Swedish and Social Studies at the social sciences programme in upper secondary school. “Textual power” is here defined as both ability and possibility: to position oneself in relation to the text, to read/interpret critically and to show mobility in the actual literacy sphere. Two analytical tools were used: Langer’s theories about envisionment building and Martin & White’s appraisal framework for attitude and engagement. The linguistic expressions are contextualised in a model inspired by Linell. I base my discussion of the students’ mobility in the actual literacy sphere on the New Literacy theories of Barton and Street, while Anward gives the means to understand text-reproducing practices. The results indicate that the students used a limited range of positions in relation to texts, rarely expressed critical literacy and showed limited mobility in the actual literacy spheres. The students’ possibilities to linguistically express textual power were determined by the design of the teaching contexts. The students were given few possibilities to develop their ability to linguistically express textual power. To compensate for this, the students used a strategy of task solving. This caused a gap between ideally desired and actually produced text. The acceptance of the gap can be explained if the practice is considered text-reproducing. The literacy sphere where the students found themselves seems to consist of an ecological system based on a consensus-driven text-reproducing practice where critical and comparative reading and writing do not take root and thrive.
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- Andersson Vogel, Maria, 1980-
(författare)
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Särskilda ungdomshem och vårdkedjor : Om ungdomar, kön, klass och etnicitet
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis follows a group of youths placed in secure unit care who have participated in a chain-of-care project aiming to better plan their discharge and aftercare. The overall aim of the thesis is to link a detailed description of these young people with an analysis of the project they participated in, and to undertake one- and two-year follow-up studies. Analytic focus is on the significance of gender, class and ethnicity. The study is mainly based on structured interviews performed at the secure units upon entry into care, discharge and at a one-year follow up. Data have also been used from criminal records and interviews with project staff.When entering care, these youths exhibited extensive problems in both family conditions and own behaviour. The major problem in boys was criminality while girls reported poor mental health. Professionals judge youth of foreign background as more criminal than youth of Swedish background despite a lack of difference in self-reported data. Some difference is also noticeable regarding class.Analysis of the project shows that out-of-home care was the most frequent intervention after leaving secure unit care, while other interventions were difficult to uphold over time. Few girls received help with their mental health problems. At the one-year follow up, the youths reported an overall better situation, although extensive problems still remained. Above all, girls’ mental health problems remained as before. At the 2-year follow up the study group was compared with a control group in order to investigate effects of the project regarding criminality and recommitment to secure unit care. The comparison shows that the project had no effect. This is discussed in relation to poor organization and the difficulty of adjusting a project like this to the target group, along with the substantial part played by gender, class and ethnicity in how the youth are construed and treated.
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