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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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| 2. |
- Ekesbo, Rickard, et al.
(författare)
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Chronic Helicobacter pylori infection in a population in southern Sweden analysed by histopathology, immunoblot and ELISA serology.
- 2006
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Ingår i: European Journal of Gastroenterology and Hepathology. - 1473-5687. ; 18:6, s. 589-593
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Tidskriftsartikel (refereegranskat)abstract
- Background. Many individuals are infected with the bacterium Helicobacter pylori. Some develop ulcers or mucosal atrophy. Aims. To correlate the histological characteristics of the H. pylori-induced gastritis to the immunoblot pattern of the H. pylori infection and to compare the presence of H. pylori bacteria in tissue specimens with ELISA serology and immunoblot analysis. Methods. One hundred and sixty-six consecutive patients were referred to gastroscopy. Forty patients were excluded for various reasons and 126 were included in the study. Results. Twenty-three patients had ulcerations and 25 erosions. Ninety-two (73%) had a chronic gastritis and in 90 (71%) it involved both the antrum and corpus. Ninety-one (72%), of whom 96% had a chronic gastritis, had visible bacteria in the tissue specimens, used as the 'gold standard' for the detection of infection. In patients with chronic gastritis 65 (70%) had positive H. pylori ELISA serology, 27 (30%) had negative H. pylori ELISA, while 76 (83%) had a positive immunoblot pattern. The ELISA positive patients had more advanced chronic gastritis but a lower frequency of metaplasia and atrophy. Acute inflammatory activity in the chronic gastritis had a high immunoreactivity to 120 kDa (CagA) protein and was significantly correlated to antibody reactivity to proteins in the 53-65 kDa range (heat shock proteins) and to a 43 kDa subunit. Metaplasia and atrophy in antrum was associated with a 62 kDa protein band. Conclusion. Almost all H. pylori-infected patients had a pangastritis, visible in both antrum and corpus. Acute inflammatory activity in the chronic gastritis and the presence of metaplasia and atrophy in antrum were associated with a specific immunoblot pattern, indicating infection with more virulent strains. Immunoblot analysis had a better sensitivity than ELISA H. pylori serology.
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| 3. |
- Liggett, Thomas, et al.
(författare)
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Statistical mechanical systems on complete graphs, infinite exchangeability, finite extensions and a discrete finite moment problem
- 2007
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Ingår i: Annals of Probability. - : Institute of Mathematical Statistics. - 0091-1798 .- 2168-894X. ; 35:3, s. 867-914
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Tidskriftsartikel (refereegranskat)abstract
- We show that a large collection of statistical mechanical systems with quadratically represented Hamiltonians on the complete graph can be extended to infinite exchangeable processes. This includes all ferromagnetic Ising, Potts and Heisenberg models. By de Finetti's theorem, this is equivalent to showing that these probability measures can be expressed as averages of product measures. We provide examples showing that ``ferromagnetism'' is not however in itself sufficient and also study in some detail the Ising model with an additional 3-body interaction. Finally, we study the question of how much the antiferromagnetic Ising model can be extended. In this direction, we obtain sharp asymptotic results via a solution to a new moment problem. We also obtain a ``formula'' for the extension which is valid in many cases.
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| 4. |
- Ma, Ying-Juan, et al.
(författare)
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3D global multi-species Hall-MHD simulation of the Cassini T9 flyby
- 2007
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 34:24, s. L24S10-
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Tidskriftsartikel (refereegranskat)abstract
- The wake region of Titan is an important component of Titan's interaction with its surrounding plasma and therefore a thorough understanding of its formation and structure is of primary interest. The Cassini spacecraft passed through the distant downstream region of Titan on 18: 59: 30 UT Dec. 26, 2005, which is referred to as the T9 flyby and provided a great opportunity to test our understanding of the highly dynamic wake region. In this paper we compare the observational data (from the magnetometer, plasma analyzer and Langmuir probe) with numerical results using a 7-species Hall MHD Titan model. There is a good agreement between the observed and modeled parameters, given the uncertainties in plasma measurements and the approximations inherent in the Hall MHD model. Our simulation results also show that Hall MHD model results fit the observations better than the non-Hall MHD model for the flyby, consistent with the importance of kinetic effects in the Titan interaction. Based on the model results, we also identify various regions near Titan where Hall MHD models are applicable.
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