| 1. |
- Schael, S, et al.
(author)
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Precision electroweak measurements on the Z resonance
- 2006
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In: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Research review (peer-reviewed)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. |
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| 3. |
- Counsell, G., et al.
(author)
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Tritium retention in next step devices and the requirements for mitigation and removal techniques
- 2006
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In: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 48:12B, s. B189-B199
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Journal article (peer-reviewed)abstract
- Mechanisms underlying the retention of fuel species in tokamaks with carbon plasma-facing components are presented, together with estimates for the corresponding retention of tritium in ITER. The consequential requirement for new and improved schemes to reduce the tritium inventory is highlighted and the results of ongoing studies into a range of techniques are presented, together with estimates of the tritium removal rate in ITER in each case. Finally, an approach involving the integration of many tritium removal techniques into the ITER operational schedule is proposed as a means to extend the period of operations before major intervention is required.
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| 4. |
- Larsson, Jobs Karl, et al.
(author)
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Genetic impoverishment of the last Black grouse (Tetrao tetrix) population in the Netherlands
- 2008
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In: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 17:8, s. 1897-1904
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Journal article (peer-reviewed)abstract
- We have studied a small isolated population of black grouse (Tetrao tetrix) in the Netherlands to examine the impact of isolation and reduction in numbers on genetic diversity. We compared the genetic diversity in the last extant Dutch population with Dutch museum samples and three other black grouse populations (from England, Austria and Norway, respectively) representing isolated and continuous populations. We found significantly lower allelic richness, observed and expected heterozygosities in the present Dutch population compared to the continuous populations (Austria and Norway) and also to the historical Dutch population. However, using a bottleneck test on each population, signs of heterozygosity excess were only found in the likewise isolated English population despite that strong genetic drift was evident in the present Dutch population in comparison to the reference populations, as assessed both in pairwise F-ST and STRUCTURE analyses. Simulating the effect of a population reduction on the Dutch population from 1948 onwards, using census data and with the Dutch museum samples as a model for the genetic diversity in the initial population, revealed that the loss in number of alleles and observed heterozygosity was according to genetic drift expectations and within the standard error range of the present Dutch population. Thus, the effect of the strong decline in the number of grouse on genetic diversity was only detectable when using a reference from the past. The lack of evidence for a population reduction in the present Dutch population by using the program BOTTLENECK was attributed to a rapidly found new equilibrium as a consequence of a very small effective population size.
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| 5. |
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| 6. |
- Konrad-Schmolke, Matthias, 1970, et al.
(author)
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Combined thermodynamic and rare earth element modelling of garnet growth during subduction: Examples from ultrahigh-pressure eclogite of the Western Gneiss Region, Norway
- 2008
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In: Earth and Planetary Science Letters. - 0012-821X. ; 272:1-2, s. 488-498
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Journal article (peer-reviewed)abstract
- Major and trace element zonation patterns were determined in ultrahigh-pressure eclogite garnets from the Western Gneiss Region (Norway). All investigated garnets show Multiple growth zones and preserve complex growth zonation patterns with respect to both major and rare earth elements (REE). Due to chemical differences of the host rocks two types of major element compositional zonation patterns occur: (1) abrupt, step-like compositional changes corresponding with the growth zones and (2) compositionally homogeneous interiors, independent of growth zones, followed by abrupt chemical changes towards the rims. Despite differences in major element zonation, the REE patterns are almost identical in all garnets and can be divided into four distinct zones with characteristic patterns. In order to interpret the major and trace element distribution and zoning patterns in terms of the subduction history of the rocks, we combined thermodynamic forward models for appropriate bulk rock compositions to yield molar proportions and major element compositions of stable phases along the inferred pressure-temperature path with a mass balance distribution of REEs among the calculated stable phases during high pressure metamorphism. Our thermodynamic forward models reproduce the complex major element zonation patterns and growth zones in the natural garnets, with garnet growth predicted during four different reaction stages: (1) chlorite breakdown, (2) epidote breakdown, (3) amphibole breakdown and (4) reduction in molar clinopyroxene at ultrahigh-pressure conditions. Mass-balance of the rare earth element distribution among the modelled stable phases yielded characteristic zonation patterns in garnet that closely resemble those in the natural samples. Garnet growth and trace element incorporation Occurred in near thermodynamic equilibrium with matrix phases during subduction. The rare earth element patterns in garnet exhibit distinct enrichment zones that fingerprint the minerals involved in the garnet-forming reactions as well as local peaks that can be explained by fractionation effects and changes in the mineral assemblage. (C) 2008 Elsevier B.V. All rights reserved.
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| 7. |
- van Leeuwen, Stefan P. J., et al.
(author)
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Struggle for quality in determination of perfluorinated contaminants in environmental and human samples
- 2006
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 40:24, s. 7854-7860
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Journal article (peer-reviewed)abstract
- The first worldwide interlaboratory study on the analyses of 13 perfluorinated compounds (PFCs) in three environmental and two human samples indicates a varying degree of accuracy in relation to the matrix or analyte determined. The ability of 38 participating laboratories from 13 countries to determine the analytes in the various matrices was evaluated by calculation of z-scores according to the Cofino model. The PFCs which were reported most frequently by the laboratories, and assessed with the most satisfactory agreement, were perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). In general, the level of agreement between the participating laboratories decreased in the following order: PFC standard solution (76% satisfactory z-scores of <[2]1 for PFOS) < human blood (67%) < human plasma (63%) < fish liver extract (55%) < water (31%) < fish tissue (17%). This shows that relative good agreement between laboratories was obtained for the study of standard and human matrices. For the fish extract, most laboratories underestimated the actual PFOS concentration due to matrix effects. The results for the fish tissue and water are also poor, indicating that the extraction and cleanup steps require further improvement. It was concluded that the PFC determinations in various matrices are not yet fully mastered.
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| 8. |
- Blaudez, D., et al.
(author)
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Differential responses of ectomycorrhizal fungi to heavy metals in vitro
- 2000
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In: Mycological Research. - : Elsevier. - 0953-7562 .- 1469-8102. ; 104:11, s. 1366-1371
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Journal article (peer-reviewed)abstract
- Thirty-nine ectomycorrhizal isolates of Paxillus involutus, Pisolithus tinctorius, Suillus bovinus, S. luteus and S. variegatus were tested on cadmium, copper, nickel and zinc amended media to determine their in vitro tolerance, measured as inhibition of biomass production. Twenty-one isolates were from heavy metal polluted sites, whereas the others were from non-contaminated soils. There was a strong interspecific variation in metal tolerance. S. luteus, S. variegatus and P. tinctorius were more tolerant of Cu, Cd and Zn when compared with P. involutus, whereas the reverse was true for Ni. A high intraspecific heterogeneity in metal tolerance was also found. EC50 values for isolates originating from polluted sites were not statistically different from EC50 values for isolates originating from non-contaminated sites. The findings are discussed in relation to the potential benefits of ectomycorrhizal fungi in protecting their host plants from metal contamination.
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| 9. |
- Fu, Ying, et al.
(author)
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Radiative and nonradiative recombination of photoexcited excitons in multi-shell-coated CdSe/CdS/ZnS quantum dots
- 2009
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In: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 86:3, s. 37003-
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Journal article (peer-reviewed)abstract
- Colloidal quantum dots (QDs) have been widely studied for nanophotonics and bioimaging applications for which the lifetime of their fluorescence is of critical importance. We report experimental and theoretical characterizations of dynamic optical properties of multi-shell-coated CdSe/CdS/ZnS QDs. Quantum-mechanical studies of fundamental optical excitations and Monte Carlo simulations of energy relaxation mechanisms indicate that the excitonic states are densely compacted in the QDs and are easily photoexcited by the laser pulse in the presence of nonradiative electron-phonon interactions. For spherical QDs, the decay time of spontaneous radiative emission of individual photoexcited excitonic states with zero angular momenta is found to be only tens of picoseconds. In our multi-shell QDs, high-energy excitonic states of nonzero angular momenta have to go through a number of nonradiative electron-phonon interaction steps in order to relax to zero-angular-momentum excitonic states for radiative emission, resulting in an effective fluorescence peak at about 2 ns in the photoncount-time relationship. This explains the measured long average fluorescence lifetime of 3.6 ns. Such a long lifetime facilitates the applications of colloidal QDs in areas such as QD-based solar cells, bioimaging and metamaterials.
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