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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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| 5. |
- He, Feng, et al.
(författare)
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Chapter 6. Qualitative and quantitative assessment of the activity of the yeast nonsense-mediated mRNA decay pathway.
- 2008
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Ingår i: Methods in Enzymology. - 0076-6879 .- 1557-7988. ; 449, s. 127-47
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Tidskriftsartikel (refereegranskat)abstract
- The yeast Saccharomyces cerevisiae provides an ideal model system for elucidation of the molecular mechanisms that regulate the nonsense-mediated mRNA decay (NMD) pathway. This chapter describes an array of molecular biological, genetic, and biochemical tools that facilitate the characterization of transcripts that comprise NMD substrates and provide insights into the roles of the upf/nmd proteins in mRNA decay and translation termination. Examples illustrate the use of these methods in wild-type and NMD-deficient cells to monitor the abundance, structure, and half-lives of nonsense-containing mRNAs, the read through of premature termination codons by the ribosome, and the positioning of ribosomes at or near normal and premature termination codons.
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| 6. |
- He, Li, et al.
(författare)
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Focused ion beam fabrication of novel core-shell nanowire structures
- 2008
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:44
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Tidskriftsartikel (refereegranskat)abstract
- A novel method of indirect deposition by means of a focused ion beam (FIB) is utilized to develop metal/insulator/semiconductor nanowire core-shell structures. This method is based upon depositing an annular pattern centered on a nanowire, with secondary deposition then coating the wire. Typical cross-sectional deposition area increments as a function of ion doses are 1.3 x 10(-2) mu m(2) nC(-1) for Pt and 3.5 x 10(-2) mu m(2) nC(-1) for SiO2. The structures are examined with a transmission electron microscope (TEM) using a new nanowire TEM sample preparation method that allows direct examinations of individually selected core-shell nanowires fabricated under different indirect FIB deposition conditions. Elemental analyses by means of energy dispersive x-ray spectroscopy and electron energy filtered TEM imaging verify the deposition of SiO2 and Pt layers. Relatively uniform Pt and SiO2 coatings on individual GaP nanowires can be achieved with overall thickness deviation of about 10% for deposition up to 25-30 nm thick Pt or SiO2 shells. It should be possible to extend this approach to any nanowire/nanotube system, and to a wide range of coatings in any desired layer sequences.
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| 7. |
- Johansson, Marcus J O, et al.
(författare)
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Association of yeast Upf1p with direct substrates of the NMD pathway.
- 2007
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 104:52, s. 20872-7
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Tidskriftsartikel (refereegranskat)abstract
- Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism that detects and degrades transcripts containing premature translation termination codons. Gene expression profiling experiments have shown that inactivation of the NMD pathway leads to the accumulation of both aberrant, nonsense-containing mRNAs, and many apparently wild-type transcripts. Such increases in transcript steady-state levels could arise from direct changes in the respective mRNA half-lives, or indirectly, as a consequence of the stabilization of transcripts encoding specific regulatory proteins. Here, we distinguished direct from indirect substrates by virtue of their association with the Saccharomyces cerevisiae Upf1 protein. Analyses of this dataset, and its comparison to the sets of transcripts that respectively increase or decrease in abundance when NMD is either inactivated or reactivated, indicate that the number of direct NMD substrates is larger than previously thought and that low abundance, alternatively transcribed mRNAs, i.e., mRNAs whose 5' ends are derived from previously unannotated 5' flanking sequences, comprise a significant class of direct substrates. Using thiamine metabolism as an example, we also show that apparent NMD-regulated cellular pathways may actually reflect the detection of low-abundance alternative transcripts under conditions where a pathway is repressed.
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