| 1. |
- 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. |
- Simon, Geoff I., et al.
(författare)
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Impacts of Aging on Anemia Tolerance, Transfusion Thresholds, and Patient Blood Management
- 2019
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Ingår i: Transfusion Medicine Reviews. - : W B SAUNDERS CO-ELSEVIER INC. - 0887-7963 .- 1532-9496. ; 33:3, s. 154-161
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Forskningsöversikt (refereegranskat)abstract
- Evidence-based patient blood management guidelines commonly recommend restrictive hemoglobin thresholds of 70 to 80 g/L for asymptomatic adults. However, most transfusion trials have enrolled adults across a broad age span, with few exclusive to older adults. Our recent meta-analysis of transfusion trials that focused on older adults paradoxically found lower mortality and fewer cardiac complications when these patients were managed using higher hemoglobin thresholds. We postulate that declining cardiac output with age contributes to deteriorating oxygen delivery capacity which impacts anemia-associated outcomes in older adults and propose a model to explain this age-related difference. We reviewed evidence concerning the pathophysiology of aging to explore the disparity in transfusion trial outcomes related to hemoglobin thresholds in different age groups. The literature was searched for normative cardiac output values at different ages in healthy adults. Using normative peak cardiac output data, we modeled oxygen delivery capacity in young, middle-aged, and older adults at a range of hemoglobin levels. Cardiovascular and pulmonary systems are impacted by age-related pathophysiological changes. Diminishing peak cardiac output associated with aging reduces the maximal oxygen delivery achievable under metabolic stress. Hence, at low hemoglobin levels, older adults are more susceptible to tissue hypoxia than younger adults. Our model predicts that an older adult with a hemoglobin of 100 g/L has a similar peak oxygen delivery capacity to a young adult with a hemoglobin of 70 g/L. Age-related pathophysiological changes provide some explanation as to why older adults have a lower tolerance for anemia than younger adults. This indicates the need for patient blood management hemoglobin thresholds specific to older as distinct from younger adults. The primary application of this model is in the consideration of patients rehabilitating to life outside hospital. It is important to note that pathophysiological changes associated with critical illness and major surgery are more complex than can be described in a simple model based on cardiac output and hemoglobin concentration. However, our review of oxygen transport and delivery in health and disease states allows the model to be considered in the context of treatment decisions for anemic adults in a range of hospital and community settings. (C) 2019 Elsevier Inc. All rights reserved.
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