| 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. |
- Bale, S. D., et al.
(författare)
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The FIELDS Instrument Suite for Solar Probe Plus
- 2016
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 204:1-4, s. 49-82
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Forskningsöversikt (refereegranskat)abstract
- NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.
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| 3. |
- Epstein, M., et al.
(författare)
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Using hierarchical decomposition to speed up average consensus
- 2008
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Ingår i: Proceedings of the 17th IFAC World Congress, 2008. ; , s. 612-618
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Konferensbidrag (refereegranskat)abstract
- We study the continuous-time consensus problem where nodes on a graph attempt to reach average consensus. We consider communication graphs that can be decomposed into a hierarchical structure and present a consensus scheme that exploits this hierarchical topology. The scheme consists of splitting the overall graph into layers of smaller connected subgraphs. Consensus is performed within the individual subgraphs starting with those of the lowest layer of the hierarchy and moving upwards. Certain ``leader'' nodes bridge the layers of the hierarchy. By exploiting the increased convergence speed of the smaller subgraphs, we show how this scheme can achieve faster overall convergence than the standard single-stage consensus algorithm running on the full graph topology. The result presents some fundamentals on how the communication architecture influences the global performance of a networked system. Analytical performance bounds are derived and simulations provided to illustrate the effectiveness of the scheme.
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| 4. |
- Karlsson, Tomas, et al.
(författare)
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Quiet, Discrete Auroral Arcs-Observations
- 2020
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Ingår i: Space Science Reviews. - : Springer. - 0038-6308 .- 1572-9672. ; 216:1
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Forskningsöversikt (refereegranskat)abstract
- Quiet, discrete auroral arcs are an important and fundamental consequence of solar wind-magnetosphere interaction. We summarize the current standing of observations of such auroral arcs. We review the basic characteristics of the arcs, including occurrence in time and space, lifetimes, width and length, as well as brightness, and the energy of the magnetospheric electrons responsible for the optical emission. We briefly discuss the connection between single and multiple discrete arcs. The acceleration of the magnetospheric electrons by high-altitude electric potential structure is reviewed, together with our current knowledge of these structures. Observations relating to the potential drop, altitude distribution and lifetimes are reviewed, as well as direct evidence for the parallel electric fields of the acceleration structures. The current closure in the ionosphere of the currents carried by the auroral electrons is discussed together with its impact on the ionosphere and thermosphere. The connection of auroral arcs to the magnetosphere and generator regions is briefly touched upon. Finally we discuss how to progress from the current observational status to further our understanding of auroral arcs.
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| 5. |
- Malkiewicz, Katarzyna, et al.
(författare)
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Nanomaterials in reach
- 2011
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Ingår i: Toxicology Letters. - : Elsevier BV. - 0378-4274 .- 1879-3169. ; 205, s. S45-S45
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Several critical differences between the “nano” forms of substances and their “bulk” counterparts may necessitate additional considerations in regulatory frameworks to adequately address potential risks posed by nanomaterials (NMs). The aim of this presentation is to address the problematics of assessing and managing risks of NMs by the means of EU chemicals regulation REACH (Registration, Evaluation, and Authorization of Chemicals). It is based on the results of the SKEP-ERA net project “Nanomaterials in REACH”, which during year 2010 gathered international expertise on chemicals regulation, physico-chemical properties and toxicity of NMs, and environmental and technology policy. Analysis and discussion points cover following topics: definitions concerning nanomaterials, REACH provisions for registration of NMs as substances, and in articles (including “phase-in”/“non-phase-in” status, mass based tonnage thresholds, “prioritization” criteria, classification as hazardous, percentage thresholds in articles), substance identification, scope of data requirements, standardization and methodology for human and environmental hazards identification and risk characterisation. Examples of resulting recommendations include: (1) adopt a single overarching definition of NMs for regulatory purposes; (2) treat “nano” forms as different from their “bulk” counterparts and as “non-phase in” substances; (3) differentiate “nano” forms with the same core chemistry using differences in the physicochemical parameters; (4) introduce mandatory list of physicochemical properties for substance identification; (5) introduce alternatives to the tonnage triggers; (6) develop register of comprehensive information on the presence of NMs in articles; (7) extend a scope of data requirements with nano-specific data requirements; (8) develop nano-specific criteria for inclusion in the SVHC list.
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| 6. |
- Mella, M. R., et al.
(författare)
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Sounding rocket study of two sequential auroral poleward boundary intensifications
- 2011
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116, s. A00K18-
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Tidskriftsartikel (refereegranskat)abstract
- The Cascades-2 sounding rocket was launched on 20 March 2009 at 11: 04: 00 UT from the Poker Flat Research Range in Alaska, and flew across a series of poleward boundary intensifications (PBIs). The rocket initially crosses a diffuse arc, then crosses the equatorward extent of one PBI (a streamer), and finally crosses the initiation of a separate PBI before entering the polar cap. Each of the crossings have fundamentally different in situ electron energy and pitch angle structure, and different ground optics images of visible aurora. It is found that the diffuse arc has a quasi-static acceleration mechanism, and the intensification at the poleward boundary has an Alfvenic acceleration mechanism. The streamer shows characteristics of both types of acceleration. PFISR data provide ionospheric context for the rocket observations. Three THEMIS satellites in close conjunction with the rocket foot point show earthward flows and slight dipolarizations in the magnetotail associated with the in situ observations of PBI activity. An important goal of the Cascades-2 study is to bring together the different observational communities (rocket, ground cameras, ground radar, satellite) with the same case study. The Cascades-2 experiment is the first sounding rocket observation of a PBI sequence, enabling a detailed investigation of the electron signatures and optical aurora associated with various stages of a PBI sequence as it evolves from an Alfvenic to a more quasi-static structure.
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| 7. |
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| 8. |
- Soto, Rodrigo, et al.
(författare)
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Crystal Growth Kinetics of Pharmaceutical Compounds
- 2020
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 20:12, s. 7626-7639
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Tidskriftsartikel (refereegranskat)abstract
- The crystal growth kinetics of piracetam, fenofibrate, phenylbutazone, acetaminophen, carbamazepine, and risperidone in methanol have been studied by two different methods; the isothermal seeded desupersaturation experiment (ISD) and the rotating disk technique (RD). Data has been collected in the range of temperature 288-303 K and at different supersaturations for the ISD experiments. The RD experiments were performed at constant supersaturation. In the ISD experiments, principal component analysis has been used to relate solution concentrations from IR measurements. An empirical power law equation has been fitted to the experimental desupersaturation data, and parameter values suggest surface integration control for all the APIs studied, a conclusion further supported by a separate mass transfer analysis. The order of rate of growth among the compounds and the magnitude of the growth rates determined by the two methods are in good agreement. In addition, the Burton Cabrera Frank (BCF) and Birth and Spread (B+S) surface integration models have been fitted to the ISD desupersaturation data, and average solid-liquid interfacial energies, mean diffusion distances, and surface mass transport rates have been estimated. An analysis of the experimental results and the growth rate parameters is performed to examine to what extent the difference in growth rate of different compounds can be rationalized.
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