9,695 research outputs found
Agent-based simulation framework for airport collaborative decision making
Airport Collaborative Decision Making is based on information sharing. A better use of resources can be attained when the different stakeholders at airport operations share their more accurate and updated information. One of the main difficulties when dealing with this information sharing concept is the number of stakeholders involved and their different interest and behaviour: aircraft operators, ground handling companies, airport authority, air traffic control and the Central Flow Management Unit. It is paramount to quantify the benefit of an airport collaborative decision making strategy in order to involve all these different organisations. Simulations are required to analyse the overall system and its emerging behaviour. This paper presents the development and initial testing of an agent-based framework, which allows this behavioural analysis to be done. The simulator explicitly represents the different stakeholders involved in the A-CDM and the interactions between them from milestone 1 to 7. This framework allows independent gradual development of local behaviours and optimisation, and a gradual increase on complexity and fidelity on the simulations
Production of vector resonances at the LHC via WZ-scattering: a unitarized EChL analysis
In the present work we study the production of vector resonances at the LHC
by means of the vector boson scattering and explore the
sensitivities to these resonances for the expected future LHC luminosities. We
are assuming that these vector resonances are generated dynamically from the
self interactions of the longitudinal gauge bosons, and , and work
under the framework of the electroweak chiral Lagrangian to describe in a model
independent way the supposedly strong dynamics of these modes. The properties
of the vector resonances, mass, width and couplings to the and gauge
bosons are derived from the inverse amplitude method approach. We implement all
these features into a single model, the IAM-MC, adapted for MonteCarlo, built
in a Lagrangian language in terms of the electroweak chiral Lagrangian and a
chiral Lagrangian for the vector resonances, which mimics the resonant behavior
of the IAM and provides unitary amplitudes. The model has been implemented in
MadGraph, allowing us to perform a realistic study of the signal versus
background events at the LHC. In particular, we have focused our study on the
type of events, discussing first on the potential of the hadronic
and semileptonic channels of the final , and next exploring in more detail
the clearest signals. These are provided by the leptonic decays of the gauge
bosons, leading to a final state with ,
, having a very distinctive signature, and showing clearly the
emergence of the resonances with masses in the range of 1.5-2.5 TeV, which we
have explored.Comment: Revised version accepted for publication in JHEP. Enlarged analysis.
References added. 44 pages, 23 figures, 3 table
A Cholinergic Synaptically Triggered Event Participates in the Generation of Persistent Activity Necessary for Eye Fixation
An exciting topic regarding integrative properties of the nervous system is how transient motor commands or brief sensory stimuli are able to evoke persistent neuronal changes, mainly as a sustained, tonic action potential firing. A persisting firing seems to be necessary for postural maintenance after a previous movement. We have studied in vitro and in vivo the generation of the persistent neuronal activity responsible for eye fixation after spontaneous eye movements. Rat sagittal brainstem slices were used for the intracellular recording of prepositus hypoglossi (PH) neurons and their synaptic activation from nearby paramedian pontine reticular formation (PPRF) neurons. Single electrical pulses applied to the PPRF showed a monosynaptic glutamatergic projection on PH neurons, acting on AMPA-kainate receptors. Train stimulation of the PPRF area evoked a sustained depolarization of PH neurons exceeding (by hundreds of milliseconds) stimulus duration. Both duration and amplitude of this sustained depolarization were linearly related to train frequency. The train-evoked sustained depolarization was the result of interaction between glutamatergic excitatory burst neurons and cholinergic mesopontine reticular fibers projecting onto PH neurons, because it was prevented by slice superfusion with cholinergic antagonists and mimicked by cholinergic agonists. As expected, microinjections of cholinergic antagonists in the PH nucleus of alert behaving cats evoked a gaze-holding deficit consisting of a re-centering drift of the eye after each saccade. These findings suggest that a slow, cholinergic, synaptically triggered event participates in the generation of persistent activity characteristic of PH neurons carrying eye position signals
Phenomenology of a lepton triplet
The most general phenomenological model involving a lepton triplet with
hypercharge is constructed. A distinctive feature of this model is the
prediction of a doubly charged lepton, and a new heavy Dirac neutrino. We study
the phenomenology of these exotic leptons in both low-energy experiments and at
the LHC. The model predicts FCNC processes such as rare muon decays, which are
studied in detail in order to constrain the model parameters. All the decay
channels of the exotic leptons are described for a wide range of parameters. It
is found that, if the mixing parameters between the exotic and light leptons
are not too small (), then they can be observable to a
statistical significance at the 7 TeV LHC with 10-50 fb luminosity for a
400 GeV mass, and 14 TeV with 100-300 fb luminosity for a 800 GeV mass.Comment: 28 pages, 17 figures. Version to appear in PR
Probing O-enrichment in C-rich dust planetary nebulae
The abundance of O in planetary nebulae (PNe) has been historically used as a
metallicity indicator of the interstellar medium (ISM) where they originated;
e.g., it has been widely used to study metallicity gradients in our Galaxy and
beyond. However, clear observational evidence for O self enrichment in
low-metallicity Galactic PNe with C-rich dust has been recently reported. Here
we report asymptotic giant branch (AGB) nucleosynthesis predictions for the
abundances of the CNO elements and helium in the metallicity range Zsun/4 < Z <
2Zsun. Our AGB models, with diffusive overshooting from all the convective
borders, predict that O is overproduced in low-Z low-mass (~1-3 Msun) AGB stars
and nicely reproduce the recent O overabundances observed in C-rich dust PNe.
This confirms that O is not always a good proxy of the original ISM metallicity
and another chemical elements such as Cl or Ar should be used instead. The
production of oxygen by low-mass stars should be thus considered in
galactic-evolution models.Comment: Accepted for publication in MNRAS Letters (5 pages, 1 figure, and 1
table
Galactic planetary nebulae with precise nebular abundances as a tool to understand the evolution of asymptotic giant branch stars
We present nucleosynthesis predictions (HeCNOCl) from asymptotic giant branch
(AGB) models, with diffusive overshooting from all the convective borders, in
the metallicity range Z/4 < Z < 2Zsun. They are compared to recent precise
nebular abundances in a sample of Galactic planetary nebulae (PNe) that is
divided among double-dust chemistry (DC) and oxygen-dust chemistry (OC)
according to the infrared dust features. Unlike the similar subsample of
Galactic carbon-dust chemistry PNe recently analysed by us, here the individual
abundance errors, the higher metallicity spread, and the uncertain dust
types/subtypes in some PNe do not allow a clear determination of the AGB
progenitor masses (and formation epochs) for both PNe samples; the comparison
is thus more focussed on a object-by-object basis. The lowest metallicity OC
PNe evolve from low-mass (~1 Msun) O-rich AGBs, while the higher metallicity
ones (all with uncertain dust classifications) display a chemical pattern
similar to the DC PNe. In agreement with recent literature, the DC PNe mostly
descend from high-mass (M > 3.5 Msun) solar/supersolar metallicity AGBs that
experience hot bottom burning (HBB), but other formation channels in low-mass
AGBs like extra mixing, stellar rotation, binary interaction, or He
pre-enrichment cannot be disregarded until more accurate C/O ratios would be
obtained. Two objects among the DC PNe show the imprint of advanced CNO
processing and deep second dredge-up, suggesting progenitors masses close to
the limit to evolve as core collapse supernovae (above 6 Msun). Their actual
C/O ratio, if confirmed, indicate contamination from the third dredge-up,
rejecting the hypothesis that the chemical composition of such high-metallicity
massive AGBs is modified exclusively by HBB.Comment: Accepted for publication in MNRAS (11 pages, 3 figures, and 2 tables
An atlas of Calcium triplet spectra of active galaxies
We present a spectroscopic atlas of active galactic nuclei covering the
region around the 8498, 8542, 8662 Calcium triplet (CaT) lines. The sample
comprises 78 objects, divided into 43 Seyfert 2s, 26 Seyfert 1s, 3 Starburst
and 6 normal galaxies. The spectra pertain to the inner ~300 pc in radius, and
thus sample the central kinematics and stellar populations of active galaxies.
The data are used to measure stellar velocity dispersions (sigma_star) both
with cross-correlation and direct fitting methods. These measurements are found
to be in good agreement with each-other and with those in previous studies for
objects in common. The CaT equivalent width is also measured. We find average
values and sample dispersions of W_CaT of 4.6+/-2.0, 7.0 and 7.7+/-1.0
angstrons for Seyfert 1s, Seyfert 2s and normal galaxies, respectively. We
further present an atlas of [SIII]\lambda 9069 emission line profiles for a
subset of 40 galaxies. These data are analyzed in a companion paper which
addresses the connection between stellar and Narrow Line Region kinematics, the
behaviour of the CaT equivalent width as a function of sigma_star, activity
type and stellar population properties.Comment: 18 pages, 10 figures, accepted for publication in MNRA
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