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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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- Abe, O, et al.
(författare)
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Effects of chemotherapy and hormonal therapy for early breast cancer on recurrence and 15-year survival: an overview of the randomised trials
- 2005
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Ingår i: The Lancet. - 1474-547X. ; 365:9472, s. 1687-1717
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Tidskriftsartikel (refereegranskat)abstract
- Background Quinquennial overviews (1985-2000) of the randomised trials in early breast cancer have assessed the 5-year and 10-year effects of various systemic adjuvant therapies on breast cancer recurrence and survival. Here, we report the 10-year and 15-year effects. Methods Collaborative meta-analyses were undertaken of 194 unconfounded randomised trials of adjuvant chemotherapy or hormonal therapy that began by 1995. Many trials involved CMF (cyclophosphamide, methotrexate, fluorouracil), anthracycline-based combinations such as FAC (fluorouracil, doxombicin, cyclophosphamide) or FEC (fluorouracil, epirubicin, cyclophosphamide), tamoxifen, or ovarian suppression: none involved taxanes, trastuzumab, raloxifene, or modem aromatase inhibitors. Findings Allocation to about 6 months of anthracycline-based polychemotherapy (eg, with FAC or FEC) reduces the annual breast cancer death rate by about 38% (SE 5) for women younger than 50 years of age when diagnosed and by about 20% (SE 4) for those of age 50-69 years when diagnosed, largely irrespective of the use of tamoxifen and of oestrogen receptor (ER) status, nodal status, or other tumour characteristics. Such regimens are significantly (2p=0 . 0001 for recurrence, 2p<0 . 00001 for breast cancer mortality) more effective than CMF chemotherapy. Few women of age 70 years or older entered these chemotherapy trials. For ER-positive disease only, allocation to about 5 years of adjuvant tamoxifen reduces the annual breast cancer death rate by 31% (SE 3), largely irrespective of the use of chemotherapy and of age (<50, 50-69, &GE; 70 years), progesterone receptor status, or other tumour characteristics. 5 years is significantly (2p<0 . 00001 for recurrence, 2p=0 . 01 for breast cancer mortality) more effective than just 1-2 years of tamoxifen. For ER-positive tumours, the annual breast cancer mortality rates are similar during years 0-4 and 5-14, as are the proportional reductions in them by 5 years of tamoxifen, so the cumulative reduction in mortality is more than twice as big at 15 years as at 5 years after diagnosis. These results combine six meta-analyses: anthracycline-based versus no chemotherapy (8000 women); CMF-based versus no chemotherapy (14 000); anthracycline-based versus CMF-based chemotherapy (14 000); about 5 years of tamoxifen versus none (15 000); about 1-2 years of tamoxifen versus none (33 000); and about 5 years versus 1-2 years of tamoxifen (18 000). Finally, allocation to ovarian ablation or suppression (8000 women) also significantly reduces breast cancer mortality, but appears to do so only in the absence of other systemic treatments. For middle-aged women with ER-positive disease (the commonest type of breast cancer), the breast cancer mortality rate throughout the next 15 years would be approximately halved by 6 months of anthracycline-based chemotherapy (with a combination such as FAC or FEC) followed by 5 years of adjuvant tamoxifen. For, if mortality reductions of 38% (age <50 years) and 20% (age 50-69 years) from such chemotherapy were followed by a further reduction of 31% from tamoxifen in the risks that remain, the final mortality reductions would be 57% and 45%, respectively (and, the trial results could well have been somewhat stronger if there had been full compliance with the allocated treatments). Overall survival would be comparably improved, since these treatments have relatively small effects on mortality from the aggregate of all other causes. Interpretation Some of the widely practicable adjuvant drug treatments that were being tested in the 1980s, which substantially reduced 5-year recurrence rates (but had somewhat less effect on 5-year mortality rates), also substantially reduce 15-year mortality rates. Further improvements in long-term survival could well be available from newer drugs, or better use of older drugs.
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- Chen, Weimin, 1959-, et al.
(författare)
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Spin relaxation in InGaN/Ga(Mn)N quantum wells
- 2005
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Ingår i: Bulletin of the American physical society. - 0003-0503. ; 50, s. 609-609
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Tidskriftsartikel (refereegranskat)abstract
- Proc. 2005 APS March Meeting, March 21-25, 2005; Los Angeles, CA, USA
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- Kessler, Richard, et al.
(författare)
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First-Year Sloan Digital Sky Survey-II Supernova Results : Hubble Diagram and Cosmological Parameters
- 2009
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 185:1, s. 32-84
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low- and high-redshift SN Ia surveys. Within the framework of the MLCS2K2 light-curve fitting method, we use the SDSS-II SN sample to infer the mean reddening parameter for host galaxies, RV = 2.18 ± 0.14stat ± 0.48syst, and find that the intrinsic distribution of host-galaxy extinction is well fitted by an exponential function, P(AV ) = exp(-AV /τV), with τV = 0.334 ± 0.088 mag. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey (SNLS), the Hubble Space Telescope (HST), and a compilation of Nearby SN Ia measurements. A new feature in our analysis is the use of detailed Monte Carlo simulations of all surveys to account for selection biases, including those from spectroscopic targeting. Combining the SN Hubble diagram with measurements of baryon acoustic oscillations from the SDSS Luminous Red Galaxy sample and with cosmic microwave background temperature anisotropy measurements from the Wilkinson Microwave Anisotropy Probe, we estimate the cosmological parameters w and ΩM, assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. We also consider constraints upon ΩM and ΩΛ for a cosmological constant model (ΛCDM) with w = -1 and non-zero spatial curvature. For the FwCDM model and the combined sample of 288 SNe Ia, we find w = -0.76 ± 0.07(stat) ± 0.11(syst), ΩM = 0.307 ± 0.019(stat) ± 0.023(syst) using MLCS2K2 and w = -0.96 ± 0.06(stat) ± 0.12(syst), ΩM = 0.265 ± 0.016(stat) ± 0.025(syst) using the SALT-II fitter. We trace the discrepancy between these results to a difference in the rest-frame UV model combined with a different luminosity correction from color variations; these differences mostly affect the distance estimates for the SNLS and HST SNe. We present detailed discussions of systematic errors for both light-curve methods and find that they both show data-model discrepancies in rest-frame U band. For the SALT-II approach, we also see strong evidence for redshift-dependence of the color-luminosity parameter (β). Restricting the analysis to the 136 SNe Ia in the Nearby+SDSS-II samples, we find much better agreement between the two analysis methods but with larger uncertainties: w = -0.92 ± 0.13(stat)+0.10 -0.33(syst) for MLCS2K2 and w = -0.92 ± 0.11(stat)+0.07 -0.15 (syst) for SALT-II.
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- Nascimento, V. B., et al.
(författare)
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Surface-Stabilized Nonferromagnetic Ordering of a Layered Ferromagnetic Manganite
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:22, s. 227201-
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Tidskriftsartikel (refereegranskat)abstract
- An outstanding question regarding the probing or possible device applications of correlated electronic materials (CEMs) with layered structure is the extent to which their bulk and surface properties differ or not. The broken translational symmetry at the surface can lead to distinct functionality due to the charge, lattice, orbital, and spin coupling. Here we report on the case of bilayered manganites with hole doping levels corresponding to bulk ferromagnetic order. We find that, although the hole doping level is measured to be the same as in the bulk, the surface layer is not ferromagnetic. Further, our low-energy electron diffraction and x-ray measurements show that there is a c-axis collapse in the outermost layer. Bulk theoretical calculations reveal that, even at fixed doping level, the relaxation of the Jahn-Teller distortion at the surface is consistent with the stabilization of an A-type antiferromagnetic state.
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- Chen, Weimin, 1959-, et al.
(författare)
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Efficient spin relaxation in InGaN/GaN and InGaN/GaMnN quantum wells : An obstacle to spin detection
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:19, s. 192107-
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Tidskriftsartikel (refereegranskat)abstract
- Transient magneto-optical spectroscopy of InGaNGaN and InGaNGaMnN quantum wells reveals a spin relaxation process with a characteristic time of 50 ps. We show that the observed spin relaxation is mediated by spin flips of individual carriers rather than by direct exciton spin flips, and is proposed to occur near the bottom of the exciton band (K=0). Nearly complete thermalization between spin sublevels of the excitons, observed immediately after the pulsed photoexcitation, is attributed to even faster spin relaxation of photogenerated hot carriers/excitons accompanying momentum and energy relaxation at high K vectors. © 2005 American Institute of Physics.
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- Liu, X. E., et al.
(författare)
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A novel ruthenium(II) tris(bipyridine)-zinc porphyrin-rhenium carbonyl triad : synthesis and optical properties
- 2006
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Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020 .- 1464-5416. ; 62:15, s. 3674-3680
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Tidskriftsartikel (refereegranskat)abstract
- A novel ruthenium(II) tris(bipyridine)-zinc porphyrin-rhenium carbonyl triads and its free base porphyrin derivative were synthesized and characterized by H-1, C-13 NMR, UV-vis, mass-spectrometry and elemental analysis. The redox potentials of the two Compounds were measured and compared to their corresponding reference complexes. The fluorescence and transient absorption spectra of the two complexes revealed the features of two different pathways for possible photoinduced intramolectular electron transfer or energy transfer in the triads.
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- Cui, Daqing, et al.
(författare)
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Immobilization of radionuclides on iron canister material at simulated near-field conditions
- 2009
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Ingår i: Scientific Basis for Nuclear Waste Management XXXII. - Warrendale, Pa : Materials Research Society. - 9781605110967 ; 1124
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Konferensbidrag (refereegranskat)abstract
- This work is a continuation of a long-term spent fuel leaching and radionuclides immobilization (by iron canister) experiment under simulated near-field conditions, in deoxygenated 2 mM NaHCO3 solution with 1 Gy/h γ irradiation. The corrosion of iron canister material was investigated by electrochemical and microanalytical methods. Significant amounts of radionuclides (U, Np, Tc, Sr) were found to be immobilized on the corrosion layer of iron canister material by using SEM-WDS and SIMS methods. The observation is useful for bettering our understanding of near-field chemical processes at earlier canister failure conditions.
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- Cui, D., et al.
(författare)
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On the behaviour of spent fuel under simulated early canister-failure conditions
- 2006
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Ingår i: Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM. - 0894486918 - 9780894486913 ; , s. 925-932
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Konferensbidrag (refereegranskat)abstract
- This paper reports on the results of a long term experiment on spent fuel leaching, canister corrosion and radionuclide immobilization under repository conditions corresponding to early canister failure. A γ-dose of 850 mGy per hour, and Ar-flushed synthetic groundwater were used. During the first 287 days, the fractions of inventory in aqueous phase per day (f/d) increased nearly constantly for each radionuclide (except for 100Mo), with higher fractions for fission products than for actinides. After this initial stage, iron, cast iron and copper coupons (of̃30 mm2 size) were inserted into the leaching vessel: the concentrations of 238U, 237Np and 99Tc decreased by 80%, 97% and 88% to relatively stable levels (500ppb, 0.2ppb and 0.6ppb respectively). 239Pu concentrations slightly increased to the level of PuO2 solubility (0.5ppb). The leaching process for Cs, Mo and 90Sr was not influenced by the added metals. The pH and Eh values and corrosion potential were measured. The polarization resistance (Rp) was obtained from fitting of electrochemical impedance spectra, and then corrected by the surface area of the sample. The corrosion current density Icorr was calculated according to the Stern-Gary relationship, and using the same Tafel constants (26 mV)for all samples, i.e., Icorr = 0.026/Rp. The momentary corrosion rates of iron, cast iron and copper (Cu/Cu+) calculated based on the Faraday's law are in reasonable agreement with the values estimated from observation of thickness of corrosion layers using SEM microscope. The copper coupon appeared much more stable against corrosion than the other coupons. The corrosion layer and radionuclides deposited on corrosion products on iron coupons were analyzed by SEM-EDS and SIMS. Si was found to be coordinated with all iron corrosion products; however, redox sensitive elements U and Pu were mainly coordinated with the inner layer of iron corrosion products even though some 1-2 μm sized uranium-silica rich particles were found on the outer side of the iron corrosion layer. The findings of this work contribute to an improved understanding of the behaviour of spent fuel under near field repository conditions.
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- De Toledo, Paulo Fischer, et al.
(författare)
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Case study of a Multi-Infeed HVDC system
- 2008
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Konferensbidrag (refereegranskat)abstract
- There are serious concerns relating to a Multi- Infeed HIVDC system when feeding a weak AC network. Typical issues concerning multi-infeed configurations are: need for coordination of the recovery control, need for different DC modulation strategies to stabilize the system, possibility of voltage instability of the area receiving large amount of power from multiple HVDC links and the risk of mutual commutation failures. In contrast, if the area receiving electrical power from multiple HVDC transmission links is relatively strong due to the presence of large amount of generation units nearby there are still some questions that need to be investigated such as the issues underlining the operation of such a multi-infeed system, the proper design of the controls of the HVDC systems and the system dynamic performance under extreme contingencies. This paper investigates into an example of such a multi-infeed HVDC system. The authors have performed small signal analysis of the system to assess instability associated with the control modes. Electromechanical and voltage stability analysis were performed for harmful contingencies. Dynamic performance analysis was also carried out to analyze the interaction amongst various HVDC inverters during disturbances.
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- Hudson, John A., et al.
(författare)
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Characterising and modelling the excavation damaged zone in crystalline rock in the context of radioactive waste disposal
- 2009
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Ingår i: Environmental Geology. - : Springer Science and Business Media LLC. - 0943-0105 .- 1432-0495. ; 57:6, s. 1275-1297
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes current knowledge about the nature of and potential for thermo-hydro-mechanical-chemical modelling of the excavation damaged zone (EDZ) around the excavations for an underground radioactive waste repository. In the first part of the paper, the disturbances associated with excavation are explained, together with reviews of Workshops that have been held on the subject. In the second part of the paper, the results of a DECOVALEX [DEmonstration of COupled models and their VALidation against EXperiment: research funded by an international consortium of radioactive waste regulators and implementers (http://www.decovalex.com)] research programme on modelling the EDZ are presented. Four research teams used four different models to simulate the complete stress-strain curve for Avro granite from the Swedish A"spo Hard Rock Laboratory. Subsequent research extended the work to computer simulation of the evolution of the repository using a 'wall-block model' and a 'near-field model'. This included assessing the evolution of stress, failure and permeability and time-dependent effects during repository evolution. As discussed, all the computer models are well suited to sensitivity studies for evaluating the influence of their respective supporting parameters on the complete stress-strain curve for rock and for modelling the EDZ.
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- Miller, Casey W., et al.
(författare)
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Dynamic spin-polarized resonant tunneling in magnetic tunnel junctions
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:4
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Tidskriftsartikel (refereegranskat)abstract
- Precisely engineered tunnel junctions exhibit a long sought effect that occurs when the energy of the electron is comparable to the potential energy of the tunneling barrier. The resistance of metal-insulator-metal tunnel junctions oscillates with an applied voltage when electrons that tunnel directly into the barrier's conduction band interfere upon reflection at the classical turning points: the insulator-metal interface and the dynamic point where the incident electron energy equals the potential barrier inside the insulator. A model of tunneling between free electron bands using the exact solution of the Schrodinger equation for a trapezoidal tunnel barrier qualitatively agrees with experiment.
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- Miller, Casey W., et al.
(författare)
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Origin of the breakdown of Wentzel-Kramers-Brillouin-based tunneling models
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:21
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Tidskriftsartikel (refereegranskat)abstract
- The tunneling conductance of three varieties of CoFeB/MgO/CoFeB magnetic tunnel junctions depends quadratically on the applied voltage to anomalously high biases. Within the framework traditional of WKB models, this implies unphysical tunnel barrier parameters: heights near 20 eV, or widths corresponding to fewer than two MgO lattice constants. We demonstrate that the failure of such models to yield physically reasonable parameters originates from an experimentally unavoidable distribution of barrier thicknesses, possibly acting synergistically with the band structure of the barrier material. This implies that existing WKB models may lead to physically incorrect barrier parameters for contemporary tunnel junctions, magnetic or otherwise.
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