103 research outputs found
"A Decentralized Operations Concept for the European Payloads on the International Space Station"
The European Module Columbus of the International Space Station (ISS) is planned to be launched 2004. For its exploitation phase as well as for the early utilisation of the Space Station starting from 2003 onwards the operations procedures are now being defined in detail and the implementation of specific infrastructure has started. A decentralised operations concept will allow the investigators to perform their experiments using the telescience technique of remote experiment operations whenever feasible. User Support and Operation Centres (USOCs) will act as Facility Responsible Centres (FRC) performing the operations for multi user experiment facilities. The Columbus Control Centre (COL-CC) will perform the Columbus system operations, co-ordinate the European payload operations and provide the European Communications network. This paper gives an overview on the operations concepts and the tasks and set up of the involved sites
Quark exchange model for charmonium dissociation in hot hadronic matter
A diagrammatic approach to quark exchange processes in meson-meson scattering
is applied to the case of inelastic reactions of the type
(Q\barQ)+(q\barq)\rightarrow (Q\barq) + (q\barQ), where and refer to
heavy and light quarks, respectively. This string-flip process is discussed as
a microscopic mechanism for charmonium dissociation (absorption) in hadronic
matter. The cross section for the reaction is
calculated using a potential model, which is fitted to the meson mass spectrum.
The temperature dependence of the relaxation time for the \J/Psi distribution
in a homogeneous thermal pion gas is obtained. The use of charmonium for the
diagnostics of the state of hot hadronic matter produced in ultrarelativistic
nucleus-nucleus collisions is discussed.Comment: 24 pages, 3 tables, 7 figure
Distinct phenotypes of three-repeat and four-repeat human tau in a transgenic model of tauopathy.
Tau exists as six closely related protein isoforms in the adult human brain. These are generated from alternative splicing of a single mRNA transcript and they differ in the absence or presence of two N-terminal and three or four microtubule binding domains. Typically all six isoforms have been considered functionally similar. However, their differential involvement in particular tauopathies raises the possibility that there may be isoform-specific differences in physiological function and pathological role. To explore this, we have compared the phenotypes induced by the 0N3R and 0N4R isoforms in Drosophila. Expression of the 3R isoform causes more profound axonal transport defects and locomotor impairments, culminating in a shorter lifespan than the 4R isoform. In contrast, the 4R isoform leads to greater neurodegeneration and impairments in learning and memory. Furthermore, the phosphorylation patterns of the two isoforms are distinct, as is their ability to induce oxidative stress. These differences are not consequent to different expression levels and are suggestive of bona fide physiological differences in isoform biology and pathological potential. They may therefore explain isoform-specific mechanisms of tau-toxicity and the differential susceptibility of brain regions to different tauopathies
Cluster Monte Carlo and dynamical scaling for long-range interactions
Many spin systems affected by critical slowing down can be efficiently
simulated using cluster algorithms. Where such systems have long-range
interactions, suitable formulations can additionally bring down the
computational effort for each update from O() to O() or even
O(), thus promising an even more dramatic computational speed-up. Here, we
review the available algorithms and propose a new and particularly efficient
single-cluster variant. The efficiency and dynamical scaling of the available
algorithms are investigated for the Ising model with power-law decaying
interactions.Comment: submitted to Eur. Phys. J Spec. Topic
Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA
Deep--inelastic scattering events with a leading baryon have been detected by
the H1 experiment at HERA using a forward proton spectrometer and a forward
neutron calorimeter. Semi--inclusive cross sections have been measured in the
kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T
<= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV,
or a neutron with energy E' >= 160 GeV. The measurements are used to test
production models and factorization hypotheses. A Regge model of leading baryon
production which consists of pion, pomeron and secondary reggeon exchanges
gives an acceptable description of both semi-inclusive cross sections in the
region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading
neutron data are used to estimate for the first time the structure function of
the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.
Environmental changes in the western AmazĂŽnia: morphological framework, geochemistry, palynology and radiocarbon dating data
Densidade da madeira de ĂĄrvores em savanas do norte da AmazĂŽnia brasileira
Densidade da madeira (DM) Ă© uma variĂĄvel importante para estimativas de estoques de carbono arbĂłreo em ecossistemas terrestres. Este tema Ă© pobremente investigado em ĂĄreas de savana da AmazĂŽnia brasileira. O objetivo deste estudo foi investigar a DM das oito principais espĂ©cies arbĂłreas que ocorrem na savana aberta de Roraima, a maior ĂĄrea de savana do norte do bioma AmazĂŽnia. Foram verificadas as variaçÔes na DM em função da espĂ©cie e dos diferentes diĂąmetros observados ao longo da dimensĂŁo vertical de 75 indivĂduos amostrados em seis sĂtios de coleta. Foi utilizado o mĂ©todo direto para obtenção de peças de madeira do fuste e da copa. Os resultados indicaram discrepĂąncia significativa interespecĂfica, sendo Roupala montana Aubl. a espĂ©cie de maior DM mĂ©dia (0,674 g cm-3). Foi detectado que existe variação significativa da DM entre as peças do fuste e da copa, independente da espĂ©cie e do sĂtio de coleta. A densidade da madeira de peças da copa com diĂąmetro entre 5 e 10 cm pode ser utilizada como preditora da DM mĂ©dia do indivĂduo arbĂłreo. NĂłs concluimos que a DM das oito espĂ©cies arbĂłreas investigadas possui variabilidade interespecĂfica, com discrepĂąncias entre a DM do fuste e das partes lenhosas da copa. As distinçÔes aqui detectadas devem ser considerados como uma importante ferramenta para melhorar as estimativas de estoque de carbono em ĂĄreas de savanas na AmazĂŽnia
Charmonium Production in Deep Inelastic Scattering at HERA
The electroproduction of J/psi and psi(2S) mesons is studied in elastic, quasi-elastic and inclusive reactions for four momentum transfers 2 Q^2 80 GeV^2 and photon-proton centre of mass energies 25 W 180 GeV. The data were taken with the H1 detector at the electron proton collider HERA in the years 1995 to 1997. The total virtual photon-proton cross section for elastic J/psi production is measured as a function of Q^2 and W. The dependence of the production rates on the square of the momentum transfer from the proton (t) is extracted. Decay angular distributions are analysed and the ratio of the longitudinal and transverse cross sections is derived. The ratio of the cross sections for quasi-elastic psi(2S) and J/psi meson production is measured as a function of Q^2. The results are discussed in terms of theoretical models based upon perturbative QCD. Differential cross sections for inclusive and inelastic production of J/psi mesons are determined and predictions within two theoretical frameworks are compared with the data, the non-relativistic QCD factorization approach including colour octet and colour singlet contributions, and the model of Soft Colour Interactions
Performance of reconstruction and identification of Ï leptons decaying to hadrons and vÏ in pp collisions at âs=13 TeV
The algorithm developed by the CMS Collaboration to reconstruct and identify Ï leptons produced in proton-proton collisions at âs=7 and 8 TeV, via their decays to hadrons and a neutrino, has been significantly improved. The changes include a revised reconstruction of Ïâ° candidates, and improvements in multivariate discriminants to separate Ï leptons from jets and electrons. The algorithm is extended to reconstruct Ï leptons in highly Lorentz-boosted pair production, and in the high-level trigger. The performance of the algorithm is studied using proton-proton collisions recorded during 2016 at âs=13 TeV, corresponding to an integrated luminosity of 35.9 fbÂŻÂč. The performance is evaluated in terms of the efficiency for a genuine Ï lepton to pass the identification criteria and of the probabilities for jets, electrons, and muons to be misidentified as Ï leptons. The results are found to be very close to those expected from Monte Carlo simulation
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