| 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. |
- Duan, Ming-Rui, et al.
(författare)
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DNA binding mechanism revealed by high resolution crystal structure of Arabidopsis thaliana WRKY1 protein
- 2007
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 1362-4962 .- 0305-1048. ; 35:4, s. 54-1145
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Tidskriftsartikel (refereegranskat)abstract
- WRKY proteins, defined by the conserved WRKYGQK sequence, are comprised of a large superfamily of transcription factors identified specifically from the plant kingdom. This superfamily plays important roles in plant disease resistance, abiotic stress, senescence as well as in some developmental processes. In this study, the Arabidopsis WRKY1 was shown to be involved in the salicylic acid signaling pathway and partially dependent on NPR1; a C-terminal domain of WRKY1, AtWRKY1-C, was constructed for structural studies. Previous investigations showed that DNA binding of the WRKY proteins was localized at the WRKY domains and these domains may define novel zinc-binding motifs. The crystal structure of the AtWRKY1-C determined at 1.6 A resolution has revealed that this domain is composed of a globular structure with five beta strands, forming an antiparallel beta-sheet. A novel zinc-binding site is situated at one end of the beta-sheet, between strands beta4 and beta5. Based on this high-resolution crystal structure and site-directed mutagenesis, we have defined and confirmed that the DNA-binding residues of AtWRKY1-C are located at beta2 and beta3 strands. These results provided us with structural information to understand the mechanism of transcriptional control and signal transduction events of the WRKY proteins.
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| 3. |
- Sodergren, Erica, et al.
(författare)
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The genome of the sea urchin Strongylocentrotus purpuratus.
- 2006
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 314:5801, s. 941-52
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Tidskriftsartikel (refereegranskat)abstract
- We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.
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| 4. |
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| 5. |
- Su, Wenyong, et al.
(författare)
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First-principles study of electrochemical gate-controlled conductance in molecular junctions
- 2006
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 6:9, s. 2091-2094
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Tidskriftsartikel (refereegranskat)abstract
- A first-principles computational method is developed to study the electrochemical gate-controlled conductance in molecular junctions. It has been applied to a single molecular field-effect transistor made by a perylene tetracaboxylic diimide molecule connected to gold electrodes and has successfully reproduced the experimentally observed huge gate voltage effect on the current. It is found that such a significant gain is a result of the large polarization of the molecule induced by the huge local electrical field generated by the electrochemical gate. The resonant electron tunneling through unoccupied molecular orbitals is shown to be the dominant transport process.
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| 6. |
- Su, Wenyong, 1969-
(författare)
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First Principles Study of Molecular Electronic Devices
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Molecular electronics is an active research area for the future information technology. The fabrication of basic electronic elements with molecules as the core-operators has been made experimentally in the laboratory in recent years. However, the underlying electron or charge transport mechanisms for most devices are still under debate, Theoretical modelling based on the first-principles methods are expected to play an important role in this field. A generalized quantum chemical approach based on Green's function scattering theory has been developed and applied to two- and three-terminal molecular devices. It allows to study both elastic and inelastic electron scattering at hybrid density functional theory levels. It can treat molecular devices where the metal electrodes and the molecule are either chemically or physically bonded on equal footing. As one of the applications, we have studied the length dependence of electron transport in gold-oligophenylene-gold junctions. We have shown that the experimental results for molecular junctions of oligophenylene with di erent lengths can be well reproduced by hybrid density functional theory calculations. It is also found that the current-voltage characteristics of the junctions depend strongly on the metal-molecule bonding distances. With the help of the calculations, the possible gold-molecule bonding distances in the experimental devices are identi ed. The central focus of this thesis is to study the three-terminal molecular devices, namely the eld e ect transistor (FET). An extension of our quantum chemical approach to FET devices has been made and successfully applied to different FET devices constructed with polymer, small and middle sized conjugated molecules. The experimentally observed conductance oscillation in polymer FET and three orders of magnitude enhancement of the current in electrochemical gated molecular FET have been verified by the calculations. The electron transport mechanisms of these devices are revealed.
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| 7. |
- Su, Wenyong, et al.
(författare)
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Quantum chemical study of coherent electron transport in oligophenylene molecular junctions of different lengths
- 2005
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 412:4-6, s. 406-410
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Tidskriftsartikel (refereegranskat)abstract
- The coherent electron transportation properties of the gold-oligophenylene-gold junctions of different lengths have been studied by means of a generalized quantum chemical approach. The experimentally measured length dependence of current flow in the junctions has been well reproduced by the hybrid density functional theory calculations. It is found that the current-voltage characteristics of the junctions depend strongly on the metal-molecule bonding distances. With the help of the calculations, the possible gold-molecule bonding distances in the experimental devices are identified.
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| 8. |
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