2,223 research outputs found
A stochastic approach to the closure of accessible sets of control systems with application on homogeneous spaces
Given a control system on a compact manifold M, we study conditions for the foliation defined by the accessible sets to be dense in M. For this, we relate the control system to a stochastic differential equation and, by the support theorem, we give a characterization of the density in terms of the infinitesimal generator of the diffusion and its invariant measures.33351953
Genome sequence of Rhizobium sullae HCNT1 isolated from Hedysarum coronarium nodules and featuring peculiar denitrification phenotypes
The genome sequence of Rhizobium sullae strain HCNT1, isolated from root nodules of the legume Hedysarum coronarium growing in wild stands in Tuscany, Italy, is described here. Unlike other R. sullae strains, this isolate features a truncated denitrification pathway lacking NO/N2O reductase activity and displaying high sensitivity to nitrite under anaerobic conditions
Same-Sign Taus Signatures of Maximally Flavor-Violating Scalars at the LHC
We explore single and double flavor-violating scalars (flavons) production at
the 13 and 14 TeV LHC in an effective field theory formulation where flavons
always change the flavor of Standard Model fermions. When those scalars couple
to mass, their flavor-changing couplings to top quarks and tau leptons are
favored. Focusing on the mass region below the top quark mass, we find
couplings that fit the muon and electron discrepancies and avoid
several current experimental constraints. We determine the potential of the LHC
to exclude or discover such a new physics scenario with clean signatures
consisting of same-sign tau leptons and the simultaneous observation of
resonances in the tau plus electron or muon invariant mass. We found that in
the double production mode, effective couplings down to order
TeV can be probed for flavon masses in the 10-170 GeV range at the
HL-LHC at 14 TeV, but couplings down to 0.1 TeV can be excluded at 95\%
confidence level with data collected by the 13 TeV LHC in the same mass
interval.Comment: 32 pages, 12 figures, 2 table
Unveiling the Dynamics of the Universe
We explore the dynamics and evolution of the Universe at early and late
times, focusing on both dark energy and extended gravity models and their
astrophysical and cosmological consequences. Modified theories of gravity not
only provide an alternative explanation for the recent expansion history of the
universe, but they also offer a paradigm fundamentally distinct from the
simplest dark energy models of cosmic acceleration. In this review, we perform
a detailed theoretical and phenomenological analysis of different modified
gravity models and investigate their consistency. We also consider the
cosmological implications of well motivated physical models of the early
universe with a particular emphasis on inflation and topological defects.
Astrophysical and cosmological tests over a wide range of scales, from the
solar system to the observable horizon, severely restrict the allowed models of
the Universe. Here, we review several observational probes -- including
gravitational lensing, galaxy clusters, cosmic microwave background temperature
and polarization, supernova and baryon acoustic oscillations measurements --
and their relevance in constraining our cosmological description of the
Universe.Comment: 94 pages, 14 figures. Review paper accepted for publication in a
Special Issue of Symmetry. "Symmetry: Feature Papers 2016". V2: Matches
published version, now 79 pages (new format
Photon rings as tests for alternative spherically symmetric geometries with thin accretion disks
The imaging by the Event Horizon Telescope (EHT) of the supermassive central
objects at the heart of the M87 and Milky Way (Sgr A) galaxies, has
marked the first step into peering at the shadow and photon rings that
characterize the optical appearance of black holes surrounded by an accretion
disk. Recently, Vagnozzi et. al. [S.~Vagnozzi, \textit{et al.} arXiv:2205.07787
[gr-qc]] used the claim by the EHT that the size of the shadow of Sgr A
can be inferred by calibrated measurements of the bright ring enclosing it, to
constrain a large number of spherically symmetric space-time geometries. In
this work we use this result to study some features of the first and second
photon rings of a restricted pool of such geometries in thin accretion disk
settings. The emission profile of the latter is described by calling upon three
analytic samples belonging to the family introduced by Gralla, Lupsasca and
Marrone, in order to characterize such photon rings using the Lyapunov exponent
of nearly bound orbits and discuss its correlation with the luminosity
extinction rate between the first and second photon rings. We finally elaborate
on the chances of using such photon rings as observational discriminators of
alternative black hole geometries using very long baseline interferometry.Comment: 17 pages, 58 figures/image
Nutritional, Bioactive and Physicochemical Characteristics of Different Beetroot Formulations
Beetroot possesses high nutritional value and is considered one of the main dietary sources of nitrate. Nitrate has increasingly attracted the interest of the scientific community regarding new physiological, nutritional and therapeutic approaches with beneficial effects on the cardiovascular system. These effects can be explained by the possible effect of dietary nitrate in stimulating nitric oxide synthesis. Dietary nitrate can be reduced to nitrite in the oral cavity, which is then decomposed to nitric oxide and other bioactive nitrogen oxides in the stomach. Beetroot administration can be conducted by several types of formulations, in order to provide a convenient and alternative source of dietary beetroot, such as beetroot juice or beetroot chips and powder. The challenge in providing a product which, in addition to being rich in nitrate, is attractive and easy to administer, while also being microbiologically safe, is increased by the limited scientific information available concerning the nutritional aspects of beetroot formulations. In this chapter, a brief review on the efficiency of different beetroot formulations on health indicators is conducted, emphasizing the effects following the intake of nitrate-enriched beetroot gel. The metabolic and hemodynamic effects of beetroot formulations in healthy and non-healthy volunteers are also discussed
The Sunyaev-Zel'dovich effects from a cosmological hydrodynamical simulation: large-scale properties and correlation with the soft X-ray signal
Using the results of a cosmological hydrodynamical simulation of the
concordance LambdaCDM model, we study the global properties of the
Sunyaev-Zel'dovich (SZ) effects, both considering the thermal (tSZ) and the
kinetic (kSZ) component. The simulation follows gravitation and gas dynamics
and includes also several physical processes that affect the baryonic
component, like a simple reionization scenario, radiative cooling, star
formation and supernova feedback. Starting from the outputs of the simulation
we create mock maps of the SZ signals due to the large structures of the
Universe integrated in the range 0 < z < 6. We predict that the Compton
y-parameter has an average value of (1.19 +/- 0.32) 10^-6 and is lognormally
distributed in the sky; half of the whole signal comes from z < 1 and about 10
per cent from z > 2. The Doppler b-parameter shows approximately a normal
distribution with vanishing mean value and a standard deviation of 1.6 10^-6,
with a significant contribution from high-redshift (z > 3) gas. We find that
the tSZ effect is expected to dominate the primary CMB anisotropies for l >~
3000 in the Rayleigh-Jeans limit, while interestingly the kSZ effect dominates
at all frequencies at very high multipoles (l >~ 7 10^4). We also analyse the
cross-correlation between the two SZ effects and the soft (0.5-2 keV) X-ray
emission from the intergalactic medium and we obtain a strong correlation
between the three signals, especially between X-ray emission and tSZ effect
(r_l ~ 0.8-0.9) at all angular scales.Comment: 12 pages, 15 figures. Accepted for publication in MNRAS. Minor
changes, added reference
Semantic Web-based Software Product Line for Building Intelligent Tutoring Systems
Intelligent Tutoring Systems (ITS) have been assumed as an important learning resource to be added as a module in e-learning systems. However, the construction of such systems is still a hard and complex task that involves, for instance, representation and manipulation of different knowledge source. To alleviate these issues, this paper proposes a new approach for building ITS by integrating Software Product Line and Semantic Web technologies focusing on two software engineering aspects: large-scale production and customization for different learners, and how to allow these knowledge to be automatically shared between software and authors in both reuse and knowledge evolution points of view. This paper shows a modeling for the proposed product line, as well as how the Semantic Web technologies was used to achieve the effective shared knowledge
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