2,515 research outputs found
Actions and Events in Concurrent Systems Design
In this work, having in mind the construction of concurrent systems from
components, we discuss the difference between actions and events. For this
discussion, we propose an(other) architecture description language in which
actions and events are made explicit in the description of a component and a
system. Our work builds from the ideas set forth by the categorical approach to
the construction of software based systems from components advocated by Goguen
and Burstall, in the context of institutions, and by Fiadeiro and Maibaum, in
the context of temporal logic. In this context, we formalize a notion of a
component as an element of an indexed category and we elicit a notion of a
morphism between components as morphisms of this category. Moreover, we
elaborate on how this formalization captures, in a convenient manner, the
underlying structure of a component and the basic interaction mechanisms for
putting components together. Further, we advance some ideas on how certain
matters related to the openness and the compositionality of a component/system
may be described in terms of classes of morphisms, thus potentially supporting
a compositional rely/guarantee reasoning.Comment: In Proceedings LAFM 2013, arXiv:1401.056
Occurrence of radio minihalos in a mass-limited sample of galaxy clusters
We investigate the occurrence of radio minihalos --- diffuse radio sources of
unknown origin observed in the cores of some galaxy clusters --- in a
statistical sample of 58 clusters drawn from the Planck Sunyaev-Zel'dovich
cluster catalog using a mass cut (). We
supplement our statistical sample with a similarly-sized non-statistical sample
mostly consisting of clusters in the ACCEPT X-ray catalog with suitable X-ray
and radio data, which includes lower-mass clusters. Where necessary (for 9
clusters), we reanalyzed the Very Large Array archival radio data to determine
if a mihinalo is present. Our total sample includes all 28 currently known and
recently discovered radio minihalos, including 6 candidates. We classify
clusters as cool-core or non-cool core according to the value of the specific
entropy floor in the cluster center, rederived or newly derived from the
Chandra X-ray density and temperature profiles where necessary (for 27
clusters). Contrary to the common wisdom that minihalos are rare, we find that
almost all cool cores - at least 12 out of 15 (80%) - in our complete sample of
massive clusters exhibit minihalos. The supplementary sample shows that the
occurrence of minihalos may be lower in lower-mass cool-core clusters. No
minihalos are found in non-cool-cores or "warm cores". These findings will help
test theories of the origin of minihalos and provide information on the
physical processes and energetics of the cluster cores.Comment: 34 pages, accepted for publication in ApJ. Added a section
"Definition of a minihalo" and an appendix "Radio size and average surface
brigthtness of minihalos and halos
Structure and Turbulence in Simulated Galaxy Clusters and the Implications for the Formation of Radio Halos
We track the histories of massive clusters of galaxies formed within a
cosmological hydrodynamic simulation. Specifically, we track the time evolution
of the energy in random bulk motions of the intracluster medium and X-ray
measures of cluster structure and their relationship to cluster mergers. We aim
to assess the viability of the turbulent re-acceleration model for the
generation of giant radio halos by comparing the level of turbulent kinetic
energy in simulated clusters with the observed properties of radio halo
clusters, giving particular attention to the association of radio halos to
clusters with disturbedX-ray structures. The evolution of X-ray cluster
structure and turbulence kinetic energy, k, in simulations can then inform us
about the expected lifetime of radio halos and the fraction of clusters as a
function of redshift expected to host them. We find strong statistical
correlation of disturbed structure measures and the presence of enhancements in
k. Specifically, quantitatively "disturbed", radio halo-like X-ray morphology
in our sample indicates a 92% chance of the cluster in question having k
elevated to more than twice its minimum value over the cluster's life. The
typical lifetime of episodes of elevated turbulence is on the order of 1 Gyr,
though these periods can last 5 Gyrs or more. This variation reflects the wide
range of cluster histories; while some clusters undergo complex and repeated
mergers spending a majority of their time in elevated k states, other clusters
are relaxed over nearly their entire history. We do not find a bimodal
relationship between cluster X-ray luminosity and the total energy in
turbulence that might account directly for a bimodal L_X-P_{1.4 GHz} relation.
However, our result may be consistent with the observed bimodality, as here we
are not including a full treatment of cosmic rays sources and magnetic fields.Comment: 15 pages, 12 figures, MNRAS Submitte
Deep 1.4 GHZ Follow Up of the Steep Spectrum Radio Halo in Abell 521
In a recent paper we reported on the discovery of a radio halo with very
steep spectrum in the merging galaxy cluster Abell 521 through observations
with the Giant Metrewave Radio Telescope (GMRT). We showed that the steep
spectrum of the halo is inconsistent with a secondary origin of the
relativistic electrons and supports a turbulent acceleration scenario. At that
time, due to the steep spectrum, the available observations at 1.4 GHz
(archival NRAO - Very Large Array - VLA CnB-configuration data) were not
adequate to accurately determine the flux density associated with the radio
halo. In this paper we report the detection at 1.4 GHz of the radio halo in
Abell 521 using deep VLA observations in the D-configuration. We use these new
data to confirm the steep-spectrum of the object. We consider Abell 521 the
prototype of a population of very-steep spectrum halos. This population is
predicted assuming that turbulence plays an important role in the acceleration
of relativistic particles in galaxy clusters, and we expect it will be unveiled
by future surveys at low frequencies with the LOFAR and LWA radio telescopes.Comment: 11 pages, 3 figures (figure 1 available in gif format only). Requires
aastex.cls - Accepted by Ap.
Testing the radio halo-cluster merger scenario. The case of RXCJ2003.5-2323
We present a combined radio, X-ray and optical study of the galaxy cluster
RXCJ2003.5-2323. The cluster hosts one of the largest, most powerful and
distant giant radio halos known to date, suggesting that it may be undergoing a
strong merger process. The aim of our multiwavelength study is to investigate
the radio-halo cluster merger scenario. We studied the radio properties of the
giant radio halo in RXCJ2003.5-2323 by means of new radio data obtained at 1.4
GHz with the Very Large Array, and at 240 MHz with the Giant Metrewave Radio
Telescope, in combination with previously published GMRT data at 610 MHz. The
dynamical state of the cluster was investigated by means of X-ray Chandra
observations and optical ESO--NTT observations. Our study confirms that
RXCJ2003.5-2323 is an unrelaxed cluster. The unusual filamentary and clumpy
morphology of the radio halo could be due to a combination of the filamentary
structure of the magnetic field and turbulence in the inital stage of a cluster
merger.Comment: 10 page, 10 figures, accepted for publication on A&
Carfilzomib plus dexamethasone in patients with relapsed and refractory multiple myeloma: A retro-prospective observational study
Objective: We investigate safety and efficacy in common clinical practice of the combination of carfilzomib and dexamethasone (Kd56) approved for the ENDEAVOR trial for the treatment of relapsed or refractory multiple myeloma. Methods: We retro-prospective analyzed 75 patients in three centers in Tuscany, 48 of whom had a clinically relevant comorbidity and 50 of whom were older than 65 years, treated with a median use in the fourth line of therapy. We assessed the efficacy based on the International Myeloma Working Group criteria. Results: The overall response rate was 60%. Median PFS was 10 months in the general cohort; in patients treated for more than 1 cycle of therapy PFS was 12 months. Quality of response to Kd56 treatment was found to positively impact PFS. Refractory status to previous line of therapy or to lenalidomide or an history of exposure to pomalidomide, seemed to have no impact on survival. We also showed a low adverse events rate, with no neuropathy events, and a relatively small number of cardiovascular events above grade 3 (10%). Conclusion: Kd56 is an effective and well tolerated regimen in highly pretreated and elderly patients with a good safety profile
Hacia la prueba de corrección de clases
La actividad de desarrollar programas orientados a objetos, los cuales involucran referencias a memoria, pueden introducir errores difÃciles de identificar con el uso de un razonamiento operacional. Esto da lugar a la necesidad de contar con un marco teórico para la prueba de corrección de clases.
A partir de esta motivación y basándonos en la idea propuesta por B. Meyer en [Meyer 03a], trabajamos en el desarrollo de una semántica formal para probar, matemáticamente, que clases equipadas con contratos satisfacen los mismos.The activity of object oriented program development, which may involve references variables, is prone to errors which are hard to find by operational reasoning. Hence the need for a theoretical framework for proving class correctness.
Given this motivation and based on ideas proposed by B. Meyer in [Meyer 03a] we develop a formal semantics for mathematically proving that contract equipped classes satisfy their specifications.Red de Universidades con Carreras en Informática (RedUNCI
Hacia la prueba de corrección de clases
La actividad de desarrollar programas orientados a objetos, los cuales involucran referencias a memoria, pueden introducir errores difÃciles de identificar con el uso de un razonamiento operacional. Esto da lugar a la necesidad de contar con un marco teórico para la prueba de corrección de clases.
A partir de esta motivación y basándonos en la idea propuesta por B. Meyer en [Meyer 03a], trabajamos en el desarrollo de una semántica formal para probar, matemáticamente, que clases equipadas con contratos satisfacen los mismos.The activity of object oriented program development, which may involve references variables, is prone to errors which are hard to find by operational reasoning. Hence the need for a theoretical framework for proving class correctness.
Given this motivation and based on ideas proposed by B. Meyer in [Meyer 03a] we develop a formal semantics for mathematically proving that contract equipped classes satisfy their specifications.Red de Universidades con Carreras en Informática (RedUNCI
New Detections of Radio Minihalos in Cool Cores of Galaxy Clusters
Cool cores of some galaxy clusters exhibit faint radio minihalos. Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146,RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations.The radio luminosities of our minihalos and candidates are in the range of 102325 W Hz1 at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck.We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos
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