375 research outputs found
Mass signature of supernova and neutrinos in SuperKamiokande
The and neutrinos (and their antiparticles) from a
Galactic core-collapse supernova can be observed in a water-\v{C}erenkov
detector by the neutral-current excitation of O. The number of events
expected is several times greater than from neutral-current scattering on
electrons. The observation of this signal would be a strong test that these
neutrinos are produced in core-collapse supernovae, and with the right
characteristics. In this paper, this signal is used as the basis for a
technique of neutrino mass determination from a future Galactic supernova. The
masses of the and neutrinos can either be measured or
limited by their delay relative to the neutrinos. By comparing to
the high-statistics data instead of the theoretical expectation,
much of the model dependence is canceled. Numerical results are presented for a
future supernova at 10 kpc as seen in the SuperKamiokande detector. Under
reasonable assumptions, and in the presence of the expected counting
statistics, and masses down to about 50 eV can be simply
and robustly determined. The signal used here is more sensitive to small
neutrino masses than the signal based on neutrino-electron scattering.Comment: 13 pages including 5 figures, to appear in Phys. Rev. D; second
version has minor corrections and is in two-column for
Mass signature of supernova and neutrinos in the Sudbury Neutrino Observatory
Core-collapse supernovae emit of order neutrinos and antineutrinos
of all flavors over several seconds, with average energies of 10--25 MeV. In
the Sudbury Neutrino Observatory (SNO), which begins operations this year,
neutrinos and antineutrinos of all flavors can be detected by reactions which
break up the deuteron. For a future Galactic supernova at a distance of 10 kpc,
several hundred events will be observed in SNO. The and
neutrinos and antineutrinos are of particular interest, as a test of the
supernova mechanism. In addition, it is possible to measure or limit their
masses by their delay (determined from neutral-current events) relative to the
neutrinos (determined from charged-current events). Numerical
results are presented for such a future supernova as seen in SNO. Under
reasonable assumptions, and in the presence of the expected counting
statistics, a or mass down to about 30 eV can be simply
and robustly determined. If zero delay is measured, then the mass limit is
independent of the distance . At present, this seems to be the best
possibility for direct determination of a or mass within
the cosmologically interesting range. We also show how to separately study the
supernova and neutrino physics, and how changes in the assumed supernova
parameters would affect the mass sensitivity.Comment: 12 pages including 4 figures, submitted to Phys. Rev.
FEBUKO and MODMEP: Field measurements and modelling of aerosol and cloud multiphase processes
An overview of the two FEBUKO aerosol–cloud interaction field experiments in the Thüringer Wald (Germany) in October 2001 and 2002 and the corresponding modelling project MODMEP is given. Experimentally, a variety of measurement methods were deployed to probe the gas phase, particles and cloud droplets at three sites upwind, downwind and within an orographic cloud with special emphasis on the budgets and interconversions of organic gas and particle phase constituents. Out of a total of 14 sampling periods within 30 cloud events three events (EI, EII and EIII) are selected for detailed analysis. At various occasions an impact of the cloud process on particle chemical composition such as on the organic compounds content, sulphate and nitrate and also on particle size distributions and particle mass is observed. Moreover, direct phase transfer of polar organic compound from the gas phase is found to be very important for the understanding of cloudwater composition. For the modelling side, a main result of the MODMEP project is the development of a cloud model, which combines a complex multiphase chemistry with detailed microphysics. Both components are described in a fine-resolved particle/drop spectrum. New numerical methods are developed for an efficient solution of the entire complex model. A further development of the CAPRAM mechanism has lead to a more detailed description of tropospheric aqueous phase organic chemistry. In parallel, effective tools for the reduction of highly complex reaction schemes are provided. Techniques are provided and tested which allow the description of complex multiphase chemistry and of detailed microphysics in multidimensional chemistry-transport models
A Possible Violation of the Equivalence Principle by Neutrinos
We consider the effect of a long range, flavor changing tensor interaction of
possible gravitational origin. Neutrino mixing experiments provide the most
sensitive probe to date for such forces---testing the equivalence principle at
levels below . Here we justify and generalize a formalism for
describing such effects. The constraints from neutrino mixing experiments on
gravitationally induced mixing are calculated. Our detailed analysis of the
atmospheric neutrino data confirms a remarkable result: the atmospheric
neutrino data implies the same size force as does the solar neutrino data.
Additional tests of this suggestive result are discussed.Comment: 45 pages of text, 5 figures available upon request to
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Resveratrol Targeting of Carcinogen-Induced Brain Endothelial Cell Inflammation Biomarkers MMP-9 and COX-2 is Sirt1-Independent
The occurrence of a functional relationship between the release of metalloproteinases (MMPs) and the expression of cyclooxygenase (COX)-2, two inducible pro-inflammatory biomarkers with important pro-angiogenic effects, has recently been inferred. While brain endothelial cells play an essential role as structural and functional components of the blood-brain barrier (BBB), increased BBB breakdown is thought to be linked to neuroinflammation. Chemopreventive mechanisms targeting both MMPs and COX-2 however remain poorly investigated. In this study, we evaluated the pharmacological targeting of Sirt1 by the diet-derived and antiinflammatory polyphenol resveratrol. Total RNA, cell lysates, and conditioned culture media from human brain microvascular endothelial cells (HBMEC) were analyzed using qRT-PCR, immunoblotting, and zymography respectively. Tissue scan microarray analysis of grade I–IV brain tumours cDNA revealed increased gene expression of Sirt-1 from grade I–III but surprisingly not in grade IV brain tumours. HBMEC were treated with a combination of resveratrol and phorbol 12-myristate 13-acetate (PMA), a carcinogen known to increase MMP-9 and COX-2 through NF-κB. We found that resveratrol efficiently reversed the PMA-induced MMP-9 secretion and COX-2 expression. Gene silencing of Sirt1, a critical modulator of angiogenesis and putative target of resveratrol, did not lead to significant reversal of MMP-9 and COX-2 inhibition. Decreased resveratrol inhibitory potential of carcinogen-induced IκB phosphorylation in siSirt1-transfected HBMEC was however observed. Our results suggest that resveratrol may prevent BBB disruption during neuroinflammation by inhibiting MMP-9 and COX-2 and act as a pharmacological NF-κB signal transduction inhibitor independent of Sirt1
Understanding the interplay between social and spatial behaviour
According to personality psychology, personality traits determine many aspects of human behaviour. However, validating this insight in large groups has been challenging so far, due to the scarcity of multi-channel data. Here, we focus on the relationship between mobility and social behaviour by analysing trajectories and mobile phone interactions of ∼1000 individuals from two high-resolution longitudinal datasets. We identify a connection between the way in which individuals explore new resources and exploit known assets in the social and spatial spheres. We show that different individuals balance the exploration-exploitation trade-off in different ways and we explain part of the variability in the data by the big five personality traits. We point out that, in both realms, extraversion correlates with the attitude towards exploration and routine diversity, while neuroticism and openness account for the tendency to evolve routine over long time-scales. We find no evidence for the existence of classes of individuals across the spatio-social domains. Our results bridge the fields of human geography, sociology and personality psychology and can help improve current models of mobility and tie formation
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