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Träfflista för sökning "WFRF:(Muller David C.) srt2:(2006-2009)"

Sökning: WFRF:(Muller David C.) > (2006-2009)

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  • Schael, S, et al. (författare)
  • Precision electroweak measurements on the Z resonance
  • 2006
  • Ingår i: Physics Reports. - Elsevier. - 0370-1573. ; 427:5-6, s. 257-454
  • 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.
  • Laj, P., et al. (författare)
  • Measuring Atmospheric Composition Change
  • 2009
  • Ingår i: Atmospheric Environment. - 1352-2310. ; 43:33, s. 5351-5414
  • Tidskriftsartikel (refereegranskat)abstract
    • Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in-situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions.
  • Brette, Romain, et al. (författare)
  • Simulation of networks of spiking neurons : A review of tools and strategies
  • 2007
  • Ingår i: Journal of Computational Neuroscience. - 0929-5313. ; 23:3, s. 349-398
  • Forskningsöversikt (övrigt vetenskapligt)abstract
    • We review different aspects of the simulation of spiking neural networks. We start by reviewing the different types of simulation strategies and algorithms that are currently implemented. We next review the precision of those simulation strategies, in particular in cases where plasticity depends on the exact timing of the spikes. We overview different simulators and simulation environments presently available (restricted to those freely available, open source and documented). For each simulation tool, its advantages and pitfalls are reviewed, with an aim to allow the reader to identify which simulator is appropriate for a given task. Finally, we provide a series of benchmark simulations of different types of networks of spiking neurons, including Hodgkin-Huxley type, integrate-and-fire models, interacting with current-based or conductance-based synapses, using clock-driven or event-driven integration strategies. The same set of models are implemented on the different simulators, and the codes are made available. The ultimate goal of this review is to provide a resource to facilitate identifying the appropriate integration strategy and simulation tool to use for a given modeling problem related to spiking neural networks.
  • Maas, Andreas, et al. (författare)
  • The ‘Orsten’—More than a Cambrian Konservat-Lagerstätte
  • 2006
  • Ingår i: Palaeoworld. - 1871-174X. ; 15, s. 266-282
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • In several areas of southern Sweden, limestone nodules, locally called Orsten occur within bituminous alum shales. Theseshales and nodules were deposited under dysoxic conditions at the bottom of what was most likely a shallow sea during the lateMiddle to Upper Cambrian (ca. 500 million years ago). Subsequently, the name ‘Orsten’ has been referred to particular, mainlyarthropod, fossils from such nodules, and, in a wider sense, to the specific type of preservation of minute fossil through secondarilyphosphatization. This preservation is exceptional in yielding uncompacted and diagenetically undeformed three-dimensional fossils.‘Orsten’-type preservation resulted from incrustation of a thin external layer and also by impregnation by calcium phosphate and,therefore, mineralization of the surface of the former animals during early diagenesis. Primarily, this type of preservation seems tohave affected only cuticle-bearing metazoans such as cycloneuralian nemathelminths and arthropods. ‘Orsten’ preservation in thissense seems to be limited by size, in having yielded no partial or complete animals larger than 2 mm. On the other end of the scale,even larvae 100
  • Osterhaus, Albert, et al. (författare)
  • Control and eradication of classic swine fever in wild boar
  • 2009
  • Ingår i: EFSA Journal. - 1831-4732. ; :1
  • Tidskriftsartikel (refereegranskat)abstract
    • Classical swine fever (CSF) is a disease that has been causing major socio-economic damages in the EU during the last decades. Although considerable progress has been made in the eradication and prevention of the disease, the threat for an epidemic still exists. The virus is endemic in the wild boar population of several member states (MS). Wild boar cannot be managed as domestic pigs. Hunting and vaccination have been tentatively used in order to stop transmission by reducing the number of susceptibles. Oral vaccination of wild boar with modified live vaccine based on the C-strain (the only suitable) is used; this vaccine does not allow serological differentiation between vaccinated and infected animals. The aim of the control measures for CSF in wild boar is to reduce the risk of transmission to domestic pigs, to prevent an “endemic phase evolution” or to reduce the endemic phase duration. In order to support and to improve the control and eradication measures as regards CSF in wild boar, EFSA was requested by the Commission to provide scientific advice on the efficacy of the available surveillance, hunting and vaccination measures to control and eradicate CSF in feral pig populations (wild boar), considering the possible use of new diagnostic tests and vaccines. In order to reply to the mandate data were collected from MS through two questionnaires (CSF vaccines, hunting practices and CSF vaccination in wild boar). Data were also extracted from the EU CSF wild boar data base, after requesting permission from the participating MS. Considering that the data received were rather limited and not comparable, the WG decided to use a model in order to fill the gaps in the available knowledge. For the evaluation of the efficacy of CSF control in wild boar a continuous metapopulation compartmental model developed in an EU research project (FP6-5015599-CSFVACCINE&WILDBOAR) was applied. Although the disease manifests in the same manner in both domestic pig and wild boar it is more difficult to identify in wild boar because clinical monitoring of these is hardly possible. Wild boar found dead constitutes the main alert sign of CSF. Hunters and gamekeepers should be instructed to report the finding of each dead wild boar to the competent authority at all times. In case of high-risk situations, a passive surveillance should be complemented by an active serological surveillance. The active sampling of wild boar is not as efficient as in domestic pigs considering that hunting is the sole practical system to obtain samples and that the aim of hunting is quite different. Consequently, the sample size is not controlled by authorities and fits rarely the aim of the survey in terms of detecting the presence of disease at a certain level. In addition, the interpretation of serological results is confounded by maternal derived antibodies (until the 6th month of age), vaccination and the sampling quality. There is no definition at EU level of spatial and temporal units for surveillance, neither for criteria defining a disease free wild boar population. The sample size is not the only factor that dictates the overall sensitivity of surveillance systems. Indeed, wild boar habitat, hunting patterns, and disease distribution should be included when assessing surveillance system sensitivity. After a vaccination campaign, PCR positive animals can be due to modified live vaccines (MLV) but these MLV-vaccinated animals can be cross-checked for wild type CSF virus (genetic DIVA – discriminatory PCR). A positive PCR diagnosis should be considered to indicate that an animal is or has been infected with the wild type or MLV virus but it is not necessarly still infectious. According to previous field experience and to model simulations of a CSF epidemic in a wild boar population and the possible outcomes regarding vaccination: the disease will fade out without any additional control measures in small populations (between 1000 and 1500); hunting is not efficient for CSF control and should not exceed the normal 45% per year. Hunting is currently needed for sampling; vaccination: increases population immunity progressively. The maximum population immunity is only reached after three double campaigns; by one isolated campaign cannot increase population immunity adequately to control CSF and might even aggravate the persistence of CSF; mainly prevents the spread of the infection in neighbouring vaccinated patches; promotes long-term eradication through a progressive reduction of virus transmission to neighbouring areas; always reduces the epidemic peak (number of infected animals/time). Endemic evolution of infection may occur when a low rate of vaccination is achieved; in both infected and not yet infected areas, reaching a minimum target of 40 % of susceptible animals is necessary to obtain a positive control effect, below 20% - will increase probability of endemic stability, above 60% - will always eradicate the infection
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