1,649 research outputs found
Bulges
We model the evolution of the galactic bulge and of the bulges of a selected
sample of external spiral galaxies, via the multiphase multizone evolution
model. We address a few questions concerning the role of the bulges within
galactic evolution schemes and the properties of bulge stellar populations. We
provide solutions to the problems of chemical abundances and spectral indices,
the two main observational constraints to bulge structure.Comment: 15 pages, 10 figures, to be published in MNRA
Filosofia e letteratura degli spazi naturali e umani: prove di dialogo interdisciplinare con Theo D\u2019haen
Studio sull\u2019interconnessione artistica tra spazio e tempo, su come ciascuno influenzi l\u2019altro nei lavori presi in esame dal Prof. D\u2019haen, e come lo spazio geografico diventi anche spazio culturale, in cui i personaggi arrivano a modificare la
propria indole
Parametric analysis on external dissipative link system for seismic protection of low rise R.C. buildings
The seismic rehabilitation of existing R.C. and masonry buildings is a topical issue in Civil Engineering. A useful technique consists in the introduction of the external bracing system. This kind of intervention can be improved through the introduction of dissipative links, investigated here with the help of some examples. The links are made of common steel profiles: length, geometry and positioning are considered as design parameters. A general procedure of link-bracing optimization is proposed by applying a set of identical external restraints. The adopted dissipative links allow a cheaper and more effective design both in terms of ULS and of DLS: the damages are addressed in a small area allowing easy replacement of the links in case of an earthquake
Characterizing stellar populations in spiral disks
It is now possible to measure detailed spectral indices for stellar
populations in spiral disks. We propose to interpret these data using
evolutionary synthesis models computed from the Star Formation Histories
obtained from chemical evolutionary models. We find that this technique is a
powerful tool to discriminate between old and young stellar populations. We
show an example of the power of Integral Field spectroscopy in unveiling the
spatial distribution of populations in a barred galaxy.Comment: 5 pages, to be published in "Science Perspectives for 3D
Spectroscopy", Eds. M. Kissler-Patig, M.M. Roth and J.R. Walsh
(Springer-Verlag, ESO astrophysics symposia series
Oxygen and nitrogen abundances in Virgo and field spirals
The oxygen and nitrogen abundances in the HII regions of the nine Virgo
spirals of the sample from Skillman et al (1996) and in nine field spiral
galaxies are re-determined with the recently suggested P - method. We confirm
that there is an abundance segregation in the sample of Virgo spirals in the
sense that the HI deficient Virgo spirals near the core of the cluster have
higher oxygen abundances in comparison to the spirals at the periphery of the
Virgo cluster. At the same time both the Virgo periphery and core spirals have
counterparts among field spirals. We conclude that if there is a difference in
the abundance properties of the Virgo and field spirals, this difference
appears to be small and masked by the observational errors.Comment: 16 pages, 10 figures, accepted for publication in Astronomy and
Astrophysic
Noise in Bose Josephson junctions: Decoherence and phase relaxation
Squeezed states and macroscopic superpositions of coherent states have been
predicted to be generated dynamically in Bose Josephson junctions. We solve
exactly the quantum dynamics of such a junction in the presence of a classical
noise coupled to the population-imbalance number operator (phase noise),
accounting for, for example, the experimentally relevant fluctuations of the
magnetic field. We calculate the correction to the decay of the visibility
induced by the noise in the non-Markovian regime. Furthermore, we predict that
such a noise induces an anomalous rate of decoherence among the components of
the macroscopic superpositions, which is independent of the total number of
atoms, leading to potential interferometric applications.Comment: Fig 2 added; version accepted for publicatio
Effect of phase noise on useful quantum correlations in Bose Josephson junctions
In a two-mode Bose Josephson junction the dynamics induced by a sudden quench
of the tunnel amplitude leads to the periodic formation of entangled states.
For instance, squeezed states are formed at short times and macroscopic
superpositions of phase states at later times. The two modes of the junction
can be viewed as the two arms of an interferometer; use of entangled states
allows to perform atom interferometry beyond the classical limit. Decoherence
due to the presence of noise degrades the quantum correlations between the
atoms, thus reducing phase sensitivity of the interferometer. We consider the
noise induced by stochastic fluctuations of the energies of the two modes of
the junction. We analyze its effect on squeezed states and macroscopic
superpositions and study quantitatively the amount of quantum correlations
which can be used to enhance the phase sensitivity with respect to the
classical limit. To this aim we compute the squeezing parameter and the quantum
Fisher information during the quenched dynamics. For moderate noise intensities
we show that these useful quantum correlations increase on time scales beyond
the squeezing regime. This suggests multicomponent superpositions as
interesting candidates for high-precision atom interferometry
Toward Regeneration of the Heart: Bioengineering Strategies for Immunomodulation.
Myocardial Infarction (MI) is the most common cardiovascular disease. An average-sized MI causes the loss of up to 1 billion cardiomyocytes and the adult heart lacks the capacity to replace them. Although post-MI treatment has dramatically improved survival rates over the last few decades, more than 20% of patients affected by MI will subsequently develop heart failure (HF), an incurable condition where the contracting myocardium is transformed into an akinetic, fibrotic scar, unable to meet the body\u27s need for blood supply. Excessive inflammation and persistent immune auto-reactivity have been suggested to contribute to post-MI tissue damage and exacerbate HF development. Two newly emerging fields of biomedical research, immunomodulatory therapies and cardiac bioengineering, provide potential options to target the causative mechanisms underlying HF development. Combining these two fields to develop biomaterials for delivery of immunomodulatory bioactive molecules holds great promise for HF therapy. Specifically, minimally invasive delivery of injectable hydrogels, loaded with bioactive factors with angiogenic, proliferative, anti-apoptotic and immunomodulatory functions, is a promising route for influencing the cascade of immune events post-MI, preventing adverse left ventricular remodeling, and offering protection from early inflammation to fibrosis. Here we provide an updated overview on the main injectable hydrogel systems and bioactive factors that have been tested in animal models with promising results and discuss the challenges to be addressed for accelerating the development of these novel therapeutic strategies
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