| 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. |
|
|
| 3. |
- Raiteri, C. M., et al.
(författare)
-
WEBT and XMM-Newton observations of 3C 454.3 during the post-outburst phase - Detection of the little and big blue bumps
- 2007
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 473:3, s. 819-827
-
Tidskriftsartikel (refereegranskat)abstract
- Context. The quasar-type blazar 3C 454.3 was observed to undergo an unprecedented optical outburst in spring 2005, affecting the source brightness from the near-IR to the X-ray frequencies. This was first followed by a millimetric and then by a radio outburst, which peaked in February 2006. Aims. In this paper we report on follow-up observations to study the multiwavelength emission in the post-outburst phase. Methods. Radio, near-infrared, and optical monitoring was performed by the Whole Earth Blazar Telescope (WEBT) collaboration in the 2006-2007 observing season. XMM-Newton observations on July 2-3 and December 18-19, 2006 added information on the X-ray and UV states of the source. Results. The source was in a faint state. The radio flux at the higher frequencies showed a fast decreasing trend, which represents the tail of the big radio outburst. It was followed by a quiescent state, common at all radio frequencies. In contrast, moderate activity characterized the near-IR and optical light curves, with a progressive increase of the variability amplitude with increasing wavelength. We ascribe this redder-when-brighter behaviour to the presence of a ""little blue bump"" due to line emission from the broad line region, which is clearly visible in the source spectral energy distribution (SED) during faint states. Moreover, the data from the XMM- Newton Optical Monitor reveal a rise of the SED in the ultraviolet, suggesting the existence of a "" big blue bump"" due to thermal emission from the accretion disc. The X-ray spectra are well fitted with a power- law model with photoelectric absorption, possibly larger than the Galactic one. However, the comparison with previous X-ray observations would imply that the amount of absorbing matter is variable. Alternatively, the intrinsic X-ray spectrum presents a curvature, which may depend on the X-ray brightness. In this case, two scenarios are possible. i) There is no extra absorption, and the X-ray spectrum hardens at low energies, the hardening being more evident in bright states; ii) there is a constant amount of extra absorption, likely in the quasar environment, and the X-ray spectrum softens at low energies, at least in faint X-ray states. This softening might be the result of a flux contribution by the high-frequency tail of the big blue bump.
|
|
| 4. |
- Abramsson-Zetterberg, Lilianne, et al.
(författare)
-
The impact of folate status and folic acid supplementation on the micronucleus frequency in human erythrocytes
- 2006
-
Ingår i: Mutation Research. - : Elsevier BV. - 1383-5742 .- 1388-2139. ; 603:1, s. 33-40
-
Tidskriftsartikel (refereegranskat)abstract
- Folic acid has a well-documented stabilising effect on chromosomes. A correlation between folate status and chromosome stability in humans has been reported in studies that were restricted to certain subpopulations, e.g., folate-deficient persons. The goal of the present investigation was to clarify if there also is a correlation between folate status and chromosome stability among individuals without any folate deficiency. The method used here is the recently developed flow cytometry-based micronucleus assay in human transferrin-positive reticulocytes (MN-Trf-Ret). In a blood sample, separation of the very young reticulocytes from the mature erythrocytes makes this micronucleus assay possible. This investigation comprises three studies (cross-sectional, giving baseline data), two of which are connected to an intervention study. In the three cross-sectional studies (total number of subjects, 99) the frequency of MN-Trf-Ret (fMN-Trf-Ret) was measured and compared with the serum folate status. In two of the studies also serum homocysteine and Vitamin B12 were measured and compared with the baseline fMN-Trf-Ret. Combining the results from the three cross-sectional studies, a negative correlation between folate status and fMN-Trf-Ret was obtained (p < 0.05). The goal of the intervention studies was to clarify if different nutritional supplementations had any effect on the fMN-Trf-Ret and the cell proliferation (percentage polychromatic erythrocytes, PCE). Each of the two studies involved two groups, one placebo and one supplemented group. In one of the studies the supplementation was folic acid, 1000 μg/day during 1 week (n = 30, both sexes); in the other intervention study, folic acid (800 μg/day), B12 (20 μg/day) and B6 (4 mg/day) were taken during 1 week (n = 29, both sexes). No significant difference in %PCE or fMN-Trf-Ret between the two groups was found in either of the two intervention studies.
|
|
| 5. |
- Brocki, Karin, et al.
(författare)
-
Assessing the molecular genetics of the development of executive attention in children : focus on genetic pathways related to the anterior cingulate cortex and dopamine
- 2009
-
Ingår i: Neuroscience. - : Elsevier BV. - 0306-4522 .- 1873-7544. ; 164:1, s. 241-246
-
Forskningsöversikt (refereegranskat)abstract
- It is well known that children show gradual and protracted improvement in an array of behaviors involved in the conscious control of thought and emotion. Non-invasive neuroimaging in developing populations has revealed many neural correlates of behavior, particularly in the developing cingulate cortex and frontostriatal circuits. These brain regions, themselves, undergo protracted molecular and cellular change in the first two decades of human development and, as such, are ideal regions of interest for cognitive- and imaging-genetic studies that seek to link processes at the biochemical and synaptic levels to brain activity and behavior. We review our research to date that employs both adult and child-friendly versions of the attention network task (ANT) in an effort to begin to describe the role of specific genes in the assembly of a functional attention system. Presently, we constrain our predictions for genetic association studies by focusing on the role of the anterior cingulate cortex (ACC) and of dopamine in the development of executive attention.
|
|
| 6. |
- Chow, T Y, et al.
(författare)
-
Chess tableaux
- 2005
-
Ingår i: The Electronic Journal of Combinatorics. - : The Electronic Journal of Combinatorics. - 1097-1440 .- 1077-8926. ; 11:2, s. A3-
-
Tidskriftsartikel (refereegranskat)abstract
- A chess tableau is a standard Young tableau in which, for all i and j, the parity of the entry in cell ( i; j) equals the parity of i + j + 1. Chess tableaux were first defined by Jonas Sjostrand in his study of the sign-imbalance of certain posets, and were independently rediscovered by the authors less than a year later in the completely different context of composing chess problems with interesting enumerative properties. We prove that the number of 3 x n chess tableaux equals the number of Baxter permutations of n - 1, as a corollary of a more general correspondence between certain three-rowed chess tableaux and certain three-rowed Dulucq-Guibert nonconsecutive tableaux. The correspondence itself is proved by means of an explicit bijection. We also outline how lattice paths, or rat races, can be used to obtain generating functions for chess tableaux. We conclude by explaining the connection to chess problems, and raising some unanswered questions, e. g., there are striking numerical coincidences between chess tableaux and the Charney-Davis statistic; is there a combinatorial explanation?
|
|
| 7. |
- Sasse, Philipp, et al.
(författare)
-
Perlecan is critical for heart stability
- 2008
-
Ingår i: Cardiovascular Research. - : Oxford University Press (OUP). - 1755-3245 .- 0008-6363. ; 80:3, s. 435-444
-
Tidskriftsartikel (refereegranskat)abstract
- Perlecan is a heparansulfate proteoglycan found in basement membranes, cartilage, and several mesenchymal tissues that form during development, tumour growth, and tissue repair. Loss-of-function mutations in the perlecan gene in mice are associated with embryonic lethality caused primarily by cardiac abnormalities probably due to hemopericards. The aim of the present study was to investigate the mechanism underlying the early embryonic lethality and the pathophysiological relevance of perlecan for heart function. Perlecan-deficient murine embryonic stem cells were used to investigate the myofibrillar network and the electrophysiological properties of single cardiomyocytes. The mechanical stability of the developing perlecan-deficient mouse hearts was analysed by microinjecting fluorescent-labelled dextran. Maturation and formation of basement membranes and cell-cell contacts were investigated by electron microscopy, immunohistochemistry, and western blotting. Sarcomere formation and cellular functional properties were unaffected in perlecan-deficient cardiomyocytes. However, the intraventricular dye injection experiments revealed mechanical instability of the early embryonic mouse heart muscle wall before embryonic day 10.5 (E10.5). Accordingly, perlecan-null embryonic hearts contained lower amounts of the critical basement membrane components, collagen IV and laminins. Furthermore, basement membranes were absent in perlecan-null cardiomoycytes whereas adherens junctions formed and matured around E9.5. Infarcted hearts from perlecan heterozygous mice displayed reduced heart function when compared with wild-type hearts. We propose that perlecan plays an important role in maintaining the integrity during cardiac development and is important for heart function in the adult heart after injury.
|
|
