| 1. |
- Schael, S, et al.
(författare)
-
Precision electroweak measurements on the Z resonance
- 2006
-
Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
-
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.
|
|
| 2. |
- Meyer, H., et al.
(författare)
-
Overview of physics results from MAST
- 2009
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 49:10, s. 104017-
-
Tidskriftsartikel (refereegranskat)abstract
- Several improvements to the MAST plant and diagnostics have facilitated new studies advancing the physics basis for ITER and DEMO, as well as for future spherical tokamaks (STs). Using the increased heating capabilities P-NBI <= 3.8 MW H-mode at I-P = 1.2 MA was accessed showing that the energy confinement on MAST scales more weakly with I-P and more strongly with B-t than in the ITER IPB98(y, 2) scaling. Measurements of the fuel retention of shallow pellets extrapolate to an ITER particle throughput of 70% of its original designed total throughput capacity. The anomalous momentum diffusion, chi(phi), is linked to the ion diffusion, chi(i), with a Prandtl number close to P-phi approximate to chi(phi)/chi(i) approximate to 1, although chi(i) approaches neoclassical values. New high spatial resolution measurements of the edge radial electric field, E-r, show that the position of steepest gradients in electron pressure and E-r (i.e. shearing rate) are coincident, but their magnitudes are not linked. The T-e pedestal width on MAST scales with root beta(ped)(pol) rather than rho(pol). The edge localized mode (ELM) frequency for type-IV ELMs, new in MAST, was almost doubled using n = 2 resonant magnetic perturbations from a set of four external coils (n = 1, 2). A new internal 12 coil set (n <= 3) has been commissioned. The filaments in the inter-ELM and L-mode phase are different from ELM filaments, and the characteristics in L-mode agree well with turbulence calculations. A variety of fast particle driven instabilities were studied from 10 kHz saturated fishbone like activity up to 3.8 MHz compressional Alfven eigenmodes. Fast particle instabilities also affect the off-axis NBI current drive, leading to fast ion diffusion of the order of 0.5 m(2) s(-1) and a reduction in the driven current fraction from 40% to 30%. EBW current drive start-up is demonstrated for the first time in a ST generating plasma currents up to 55 kA. Many of these studies contributed to the physics basis of a planned upgrade to MAST.
|
|
| 3. |
- Lloyd, B., et al.
(författare)
-
Overview of physics results from MAST
- 2007
-
Ingår i: Nuclear Fusion. - 0029-5515 .- 1741-4326. ; 47:10, s. S658-S667
-
Tidskriftsartikel (refereegranskat)abstract
- Substantial advances have been made on the Mega AmpÚre Spherical Tokamak (MAST). The parameter range of the MAST confinement database has been extended and it now also includes pellet-fuelled discharges. Good pellet retention has been observed in H-mode discharges without triggering an ELM or an H/L transition during peripheral ablation of low speed pellets. Co-ordinated studies on MAST and DIII-D demonstrate a strong link between the aspect ratio and the beta scaling of H-mode energy confinement, consistent with that obtained when MAST data were merged with a subset of the ITPA database. Electron and ion ITBs are readily formed and their evolution has been investigated. Electron and ion thermal diffusivities have been reduced to values close to the ion neoclassical level. Error field correction coils have been used to determine the locked mode threshold scaling which is comparable to that in conventional aspect ratio tokamaks. The impact of plasma rotation on sawteeth has been investigated and the results have been well-modelled using the MISHKA-F code. Alfvén cascades have been observed in discharges with reversed magnetic shear. Measurements during off-axis NBCD and heating are consistent with classical fast ion modelling and indicate efficient heating and significant driven current. Central electron Bernstein wave heating has been observed via the O-X-B mode conversion process in special magnetically compressed plasmas. Plasmas with low pedestal collisionality have been established and further insight has been gained into the characteristics of filamentary structures at the plasma edge. Complex behaviour of the divertor power loading during plasma disruptions has been revealed by high resolution infra-red measurements.
|
|
| 4. |
- Abbondanno, U, et al.
(författare)
-
The data acquisition system of the neutron time-of-flight facility n_TOF at CERN
- 2005
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 538:1-3, s. 692-702
-
Tidskriftsartikel (refereegranskat)abstract
- The n_TOF facility at CERN has been designed for the measurement of neutron capture, fission and (n, xn) cross-sections with high accuracy. This requires a flexible and-due to the high instantaneous neutron flux-almost dead time free data acquisition system. A scalable and versatile data solution has been designed based on 8-bit flash-ADCs with sampling rates up to 2 GHz and 8 Mbyte memory buffer. The software is written in C and C++ and is running on PCs equipped with RedHat Linux.
|
|
| 5. |
- Koopman, G, et al.
(författare)
-
Acute-phase CD4+ T-cell proliferation and CD152 upregulation predict set-point virus replication in vaccinated simian-human immunodeficiency virus strain 89.6p-infected macaques
- 2009
-
Ingår i: The Journal of general virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 90:Pt 4, s. 915-926
-
Tidskriftsartikel (refereegranskat)abstract
- Human immunodeficiency virus (HIV) infection in humans and simian immunodeficiency virus (SIV) infection in macaques are accompanied by a combined early loss of CCR5 (CD195)-expressing CD4+ memory T cells, loss of T-helper function and T-cell hyperactivation, which have all been associated with development of high virus load and disease progression. Here, a cohort of vaccinated simian–human immunodeficiency virus strain 89.6p (SHIV89.6p)-infected rhesus macaques, where preferential depletion of these memory T-cell subsets does not take place and CD4+ T cells are relatively well maintained, was used to study the role of hyperactivation as an independent factor in the establishment of set-point virus load. In the acute phase of the infection, a transient loss of CD4+ T cells, as well as strong increases in expression of proliferation and activation markers on CD4+ and CD8+ T cells, together with CD152 expression on CD4+ T cells, were observed. Peak expression levels of these markers on CD4+ T cells, but not on CD8+ T cells, were correlated with high virus replication in the chronic phase of the infection. In addition, the peak expression level of these markers was correlated inversely with acute-phase, but not chronic-phase, HIV/SIV-specific gamma interferon responses. These data highlight a central role for an acute but transient CD4 decrease, as well as CD4+ T-cell activation, as independent factors for prediction of set-point levels of virus replication.
|
|
| 6. |
- Koopman, G, et al.
(författare)
-
Immune-response profiles induced by human immunodeficiency virus type 1 vaccine DNA, protein or mixed-modality immunization: increased protection from pathogenic simian-human immunodeficiency virus viraemia with protein/DNA combination
- 2008
-
Ingår i: The Journal of general virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 89:Pt 2, s. 540-553
-
Tidskriftsartikel (refereegranskat)abstract
- Current data suggest that prophylactic human immunodeficiency virus type 1 (HIV) vaccines will be most efficacious if they elicit a combination of adaptive humoral and T-cell responses. Here, we explored the use of different vaccine strategies in heterologous prime–boost regimes and evaluated the breadth and nature of immune responses in rhesus monkeys induced by epidermally delivered plasmid DNA or recombinant HIV proteins formulated in the AS02A adjuvant system. These immunogens were administered alone or as either prime or boost in mixed-modality regimes. DNA immunization alone induced cell-mediated immune (CMI) responses, with a strong bias towards Th1-type cytokines, and no detectable antibodies to the vaccine antigens. Whenever adjuvanted protein was used as a vaccine, either alone or in a regime combined with DNA, high-titre antibody responses to all vaccine antigens were detected in addition to strong Th1- and Th2-type CMI responses. As the vaccine antigens included HIV-1 Env, Nef and Tat, as well as simian immunodeficiency virus (SIV)mac239 Nef, the animals were subsequently exposed to a heterologous, pathogenic simian–human immunodeficiency virus (SHIV)89.6p challenge. Protection against sustained high virus load was observed to some degree in all vaccinated groups. Suppression of virus replication to levels below detection was observed most frequently in the group immunized with protein followed by DNA immunization, and similarly in the group immunized with DNA alone. Interestingly, control of virus replication was associated with increased SIV Nef- and Gag-specific gamma interferon responses observed immediately following challenge.
|
|
| 7. |
- Lagerstedt, Jens O., 1975, et al.
(författare)
-
Mapping the structural transition in an amyloidogenic apolipoprotein A-I
- 2007
-
Ingår i: Biochemistry. - 0006-2960. ; 46:34, s. 9693-9
-
Tidskriftsartikel (refereegranskat)abstract
- The single amino acid mutation G26R in human apolipoprotein A-I (apoA-IIOWA) leads to the formation of beta-secondary structure rich amyloid fibrils in vivo. Here we show that full-length apoA-IIOWA has a decreased lipid-binding capability, an increased amino-terminal sensitivity to protease, and a propensity to form annular protofibrils visible by electron microscopy. The molecular basis for the conversion of apolipoprotein A-I to a proamyloidogenic form was examined by electron paramagnetic resonance spectroscopy. Our recent findings [Lagerstedt, J. O., Budamagunta, M. S., Oda, M. N., and Voss, J. C. (2007) J. Biol. Chem. 282, 9143-9149] indicate that Gly26 in the native apoprotein separates a preceding beta-strand structure (residues 20-25) from a downstream largely alpha-helical region. The current study demonstrates that the G26R variant promotes a structural transition of positions 27-56 to a mixture of coil and beta-strand secondary structure. Microscopy and staining by amyloidophilic dyes suggest that this alteration extends throughout the protein within 1 week of incubation in vitro, leading to insoluble aggregates of distinct morphology. The severe consequences of the Iowa mutation likely arise from the combination of losing the contribution of the native Gly residue in terminating beta-strand propagation and the promotion of beta-structure when an Arg is introduced adjacent to the succeeding residue of identical charge and size, Arg27.
|
|
| 8. |
- Conley, Daniel, et al.
(författare)
-
Hypoxia-Related Processes in the Baltic Sea
- 2009
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:10, s. 3412-3420
-
Tidskriftsartikel (refereegranskat)abstract
- Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP. However, both the spatial extent and intensity of hypoxia have increased with anthropogenic eutrophication due to nutrient inputs. Physical processes, which control stratification and the renewal of oxygen in bottom waters, are important constraints on the formation and maintenance of hypoxia. Climate controlled inflows of saline water from the North Sea through the Danish Straits is a critical controlling factor governing the spatial extent and duration of hypoxia. Hypoxia regulates the biogeochemical cycles of both phosphorus (P) and nitrogen (N) in the water column and sediments. Significant amounts of P are currently released from sediments, an order of magnitude larger than anthropogenic inputs. The Baltic Sea is unique for coastal marine ecosystems experiencing N losses in hypoxic waters below the halocline. Although benthic communities in the Baltic Sea are naturally constrained by salinity gradients, hypoxia has resulted in habitat loss over vast areas and the elimination of benthic fauna, and has severely disrupted benthic food webs. Nutrient load reductions are needed to reduce the extent, severity, and effects of hypoxia.
|
|
| 9. |
|
|
| 10. |
|
|
