442 research outputs found
Resources for situated actions
In recent years, advances in software tools have made it easier to analyze interactive system specifications, and the range of their possible behaviors. However, the effort involved in producing the specifications of the system is still substantial, and a difficulty exists regarding the specification of plausible behaviors on the part of the user. Recent trends in technology towards more mobile and distributed systems further exacerbates the issue, as contextual factors come in to play, and less structured, more opportunistic behavior on the part of the user makes purely task-based analysis difficult. In this paper we consider a resourced action approach to specification and analysis. In pursuing this approach we have two aims - firstly, to facilitate a resource-based analysis of user activity, allowing resources to be distributed across a number of artifacts, and secondly to consider within the analysis a wider range of plausible and opportunistic user behaviors without a heavy specification overhead, or requiring commitment to detailed user models.We acknowledge with thanks EPSRC grant EP/F01404X/1 and FCT/FEDER grant POSC/EIA/56646/2004. Michael Harrison is grateful to colleagues in the ReSIST NoE (www.resit-noe.org)
X ray absorption spectroscopy and X ray Raman scattering of water and ice; an experimental view
Hadronic observables from SIS to SPS energies - anything strange with strangeness ?
We calculate and (+) rapidity
distributions and compare to experimental data from SIS to SPS energies within
the UrQMD and HSD transport approaches that are both based on string, quark,
diquark () and hadronic degrees of freedom. The
two transport models do not include any explicit phase transition to a
quark-gluon plasma (QGP). It is found that both approaches agree rather well
with each other and with the experimental rapidity distributions for protons,
's, and . Inspite of this apparent agreement both
transport models fail to reproduce the maximum in the excitation function for
the ratio found experimentally between 11 and 40 AGeV. A
comparison to the various experimental data shows that this 'failure' is
dominantly due to an insufficient description of pion rapidity distributions
rather than missing 'strangeness'. The modest differences in the transport
model results -- on the other hand -- can be attributed to different
implementations of string formation and fragmentation, that are not
sufficiently controlled by experimental data for the 'elementary' reactions in
vacuum.Comment: 46 pages, including 15 eps figures, to be published in Phys. Rev.
Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope
We analyze the timing of photons observed by the MAGIC telescope during a
flare of the active galactic nucleus Mkn 501 for a possible correlation with
energy, as suggested by some models of quantum gravity (QG), which predict a
vacuum refractive index \simeq 1 + (E/M_{QGn})^n, n = 1,2. Parametrizing the
delay between gamma-rays of different energies as \Delta t =\pm\tau_l E or
\Delta t =\pm\tau_q E^2, we find \tau_l=(0.030\pm0.012) s/GeV at the 2.5-sigma
level, and \tau_q=(3.71\pm2.57)x10^{-6} s/GeV^2, respectively. We use these
results to establish lower limits M_{QG1} > 0.21x10^{18} GeV and M_{QG2} >
0.26x10^{11} GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC
sensitivity to propagation effects at these levels. Thermal plasma effects in
the source are negligible, but we cannot exclude the importance of some other
source effect.Comment: 12 pages, 3 figures, Phys. Lett. B, reflects published versio
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
The Role of Oestrogen Receptor Beta (ERÎČ) in the Aetiology and Treatment of Type 2 Diabetes Mellitus
Introduction: Challenges facing the treatment of type 2 diabetes necessitate the search for agents which act via alternative pathways to provide better therapeutic outcomes. Recently, an increasing body of evidence implicates the activation of oestrogen receptors (ERα and ERÎČ) in the development and treatment of underlying conditions in type 2 diabetes. This article summarizes available evidence for the involvement of oestrogen receptors in insulin secretion, insulin resistance as well as glucose uptake and highlights the potential of ERÎČ as a therapeutic target.
Background: Recent studies indicate an association between the activation of each of the isoforms of ER and recent findings indicate that ERÎČ shows promise as a potential target for antidiabetic drugs. In vitro and in vivo studies in receptor knockout mice indicate beneficial actions of selective agonists of ERÎČ receptor and underscore its therapeutic potential.
Conclusion: Studies are needed to further elucidate the exact mechanism underlying the role of ERÎČ activation as a therapeutic approach in the management of type 2 diabetes
The WEBT BL Lacertae Campaign 2001 and its extension : Optical light curves and colour analysis 1994â2002
BL Lacertae has been the target of four observing campaigns by the Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present UBVRI light curves obtained by theWEBT from 1994 to 2002, including the last, extended BL Lac 2001 campaign. A total of about 7500 optical observations performed by 31 telescopes from Japan to Mexico have been collected, to be added to the âŒ15 600 observations of the BL Lac Campaign 2000. All these data allow one to follow the source optical emission behaviour with unprecedented detail. The analysis of the colour indices reveals that the flux variability can be interpreted in terms of two components: longer-term variations occurring on a fewday time scale appear as mildly-chromatic events, while a strong bluer-when-brighter chromatism characterizes very fast (intraday) flares. By decoupling the two components, we quantify the degree of chromatism inferring that longer-term flux changes imply moving along a âŒ0.1 bluerwhen- brighter slope in the B â R versus R plane; a steeper slope of âŒ0.4 would distinguish the shorter-term variations. This means that, when considering the long-term trend, the B-band flux level is related to the R-band one according to a power law of index âŒ1.1. Doppler factor variations on a âconvexâ spectrum could be the mechanism accounting for both the long-term variations and their slight chromatism.Reig Torres, Pablo, [email protected]
Flavor Production in Pb(160AGeV) on Pb Collisions: Effect of Color Ropes and Hadronic Rescattering
Collective interactions in the preequilibrium quark matter and hadronic
resonance gas stage of ultrarelativistic nucleus-nucleus collisions are studied
in the framework of the the transport theoretical approach RQMD. The paper
reviews string fusion into color ropes and hadronic rescattering which serve as
models for these interactions. Hadron production in central Pb(160AGeV) on Pb
collisions has been calculated. The changes of the final flavor composition are
more pronounced than in previous RQMD studies of light ion induced reactions at
200AGeV. The ratio of created quark pairs /(+) is
enhanced by a factor of 2.4 in comparison to results. Color rope formation
increases the initially produced antibaryons to 3 times the value in the `NN
mode', but only one quarter of the produced antibaryons survives because of
subsequent strong absorption. The differences in the final particle composition
for Pb on Pb collisions compared to S induced reactions are attributed to the
hadronic resonance gas stage which is baryon-richer and lasts longer.Comment: 60 pages + 11 postscript figures (uuencoded and included
The Earth: Plasma Sources, Losses, and Transport Processes
This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed
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