370 research outputs found
Using Self-Organizing Maps for the Behavioral Analysis of Virtualized Network Functions
Detecting anomalous behaviors in a network function virtualization infrastructure is of the utmost importance for network operators. In this paper, we propose a technique, based on Self-Organizing Maps, to address such problem by leveraging on the massive amount of historical system data that is typically available in these infrastructures. Indeed, our method consists of a joint analysis of system-level metrics, provided by the virtualized infrastructure monitoring system and referring to resource consumption patterns of the physical hosts and the virtual machines (or containers) that run on top of them, and application-level metrics, provided by the individual virtualized network functions monitoring subsystems and related to the performance levels of the individual applications. The implementation of our approach has been validated on real data coming from a subset of the Vodafone infrastructure for network function virtualization, where it is currently employed to support the decisions of data center operators. Experimental results show that our technique is capable of identifying specific points in space (i.e., components of the infrastructure) and time of the recent evolution of the monitored infrastructure that are worth to be investigated by human operators in order to keep the system running under expected conditions
Behavioral analysis for virtualized network functions: A som-based approach
In this paper, we tackle the problem of detecting anomalous behaviors in a virtualized infrastructure for network function virtualization, proposing to use self-organizing maps for analyzing historical data available through a data center. We propose a joint analysis of system-level metrics, mostly related to resource consumption patterns of the hosted virtual machines, as available through the virtualized infrastructure monitoring system, and the application-level metrics published by individual virtualized network functions through their own monitoring subsystems. Experimental results, obtained by processing real data from one of the NFV data centers of the Vodafone network operator, show that our technique is able to identify specific points in space and time of the recent evolution of the monitored infrastructure that are worth to be investigated by a human operator in order to keep the system running under expected conditions
Differences in the robustness of clusters involving the Mycobacterium tuberculosis strains most frequently isolated from immigrant cases in Madrid
AbstractTuberculosis cases infected by the same Mycobacterium tuberculosis (MTB) strain are considered to be clustered and involved in a transmission chain. Large clusters are assumed to represent active transmission chains in a population. In the present study, we focused on the analysis of large clusters defined by IS6110-restriction fragment length polymorphism (RFLP) typing in the immigrant population in Madrid. We identified 12 large clusters (involving 43% of the isolates) comprising 4â23 representatives. We proposed a gradient of epidemiological certainty for these large clusters. For a cluster to be considered robust and a good indicator of recent transmission, the MTB strain involved should not have been identified in a geographically and epidemiologically unrelated population and the cluster had to be re-confirmed by another highly discriminative molecular marker (MIRU-VNTR). The clusters that we discovered were classified into three categories: high, intermediate and low expected epidemiological value. In the largest cluster in the study (cluster M6; 23 representatives), failures by both criteria were identified: the representative seven-band RFLP pattern was also the most prevalent in the unrelated population (25 cases) and the cluster was fully split by MIRU-15, suggesting a lack of epidemiological value. The RFLP pattern representative of this cluster was also identified in 64 isolates from five countries in the Latin American genotype database, and again proved to be heterogeneous according to the MIRU-15 analysis. Specific analysis of large clusters, combined with the application of criteria for evaluating their robustness, could help identify uninformative clusters and target epidemiological resources towards those clusters with higher expected epidemiological value
Three-Dimensional Printing and Navigation in Bone Tumor Resection
One of the most promising advances raised by the current computer age is performing research âin silico,â which means computer-assisted. The objective of this chapter is firstly to evaluate if a 3D in-silico model of an oncological patient could be used to make a 3D-printed prototype in real scale, discriminating precisely healthy tissues, tumoral tissues and oncological margins. Secondly, the objective is to evaluate if this prototype could be representative enough to allow testing osteotomies under navigated guidance based on images. A tumor resection for a patient with diagnosed metaphyseal osteosarcoma of the proximal tibia was transferred into a rapid prototyping model, fabricated using 3D printing and representing different structures in different colors. The planned osteotomy was executed using Stryker Navigator to guide the cutting saw and the prototype was opened to verify the precision of the performed osteotomy. Both osteotomy planes showed successful correspondence with the safe margin, with a maximum error of 1 mm. The application of these techniques in general orthopedics would help to reduce the incidence of unforeseen intraoperative failures, contributing to obtain predictable surgical procedures. This would implement a new way of performing development, research and training in orthopedics and traumatology by in-silico technology
Non-parametric deprojection of NIKA SZ observations: Pressure distribution in the Planck-discovered cluster PSZ1 G045.85+57.71
The determination of the thermodynamic properties of clusters of galaxies at
intermediate and high redshift can bring new insights into the formation of
large-scale structures. It is essential for a robust calibration of the
mass-observable scaling relations and their scatter, which are key ingredients
for precise cosmology using cluster statistics. Here we illustrate an
application of high resolution arcsec) thermal Sunyaev-Zel'dovich (tSZ)
observations by probing the intracluster medium (ICM) of the \planck-discovered
galaxy cluster \psz\ at redshift , using tSZ data obtained with the
NIKA camera, which is a dual-band (150 and 260~GHz) instrument operated at the
IRAM 30-meter telescope. We deproject jointly NIKA and \planck\ data to extract
the electronic pressure distribution from the cluster core () to its outskirts () non-parametrically for the
first time at intermediate redshift. The constraints on the resulting pressure
profile allow us to reduce the relative uncertainty on the integrated Compton
parameter by a factor of two compared to the \planck\ value. Combining the tSZ
data and the deprojected electronic density profile from \xmm\ allows us to
undertake a hydrostatic mass analysis, for which we study the impact of a
spherical model assumption on the total mass estimate. We also investigate the
radial temperature and entropy distributions. These data indicate that \psz\ is
a massive ( M) cool-core cluster.
This work is part of a pilot study aiming at optimizing the treatment of the
NIKA2 tSZ large program dedicated to the follow-up of SZ-discovered clusters at
intermediate and high redshifts. (abridged)Comment: 16 pages, 10 figure
NIKA2: a mm camera for cluster cosmology
Galaxy clusters constitute a major cosmological probe. However, Planck 2015
results have shown a weak tension between CMB-derived and cluster-derived
cosmological parameters. This tension might be due to poor knowledge of the
cluster mass and observable relationship.
As for now, arcmin resolution Sunyaev-Zeldovich (SZ) observations ({\it e.g.}
SPT, ACT and Planck) only allowed detailed studies of the intra cluster medium
for low redshift clusters () high
resolution and high sensitivity SZ observations are needed. With both a wide
field of view (6.5 arcmin) and a high angular resolution (17.7 and 11.2 arcsec
at 150 and 260 GHz), the NIKA2 camera installed at the IRAM 30-m telescope
(Pico Veleta, Spain) is particularly well adapted for these observations. The
NIKA2 SZ observation program will map a large sample of clusters (50) at
redshifts between 0.5 and 0.9. As a pilot study for NIKA2, several clusters of
galaxies have been observed with the pathfinder, NIKA, at the IRAM 30-m
telescope to cover the various configurations and observation conditions
expected for NIKA2.
High angular resolution Sunyaev-Zel'dovich observations of MACS J1423.8+2404 with NIKA: Multiwavelength analysis
The prototype of the NIKA2 camera, NIKA, is an instrument operating at the
IRAM 30-m telescope, which can observe simultaneously at 150 and 260GHz. One of
the main goals of NIKA2 is to measure the pressure distribution in galaxy
clusters at high resolution using the thermal SZ (tSZ) effect. Such
observations have already proved to be an excellent probe of cluster pressure
distributions even at high redshifts. However, an important fraction of
clusters host submm and/or radio point sources, which can significantly affect
the reconstructed signal. Here we report on <20" resolution observations at 150
and 260GHz of the cluster MACSJ1424, which hosts both radio and submm point
sources. We examine the morphology of the tSZ signal and compare it to other
datasets. The NIKA data are combined with Herschel satellite data to study the
SED of the submm point source contaminants. We then perform a joint
reconstruction of the intracluster medium (ICM) electronic pressure and density
by combining NIKA, Planck, XMM-Newton, and Chandra data, focusing on the impact
of the radio and submm sources on the reconstructed pressure profile. We find
that large-scale pressure distribution is unaffected by the point sources
because of the resolved nature of the NIKA observations. The reconstructed
pressure in the inner region is slightly higher when the contribution of point
sources are removed. We show that it is not possible to set strong constraints
on the central pressure distribution without accurately removing these
contaminants. The comparison with X-ray only data shows good agreement for the
pressure, temperature, and entropy profiles, which all indicate that MACSJ1424
is a dynamically relaxed cool core system. The present observations illustrate
the possibility of measuring these quantities with a relatively small
integration time, even at high redshift and without X-ray spectroscopy.Comment: 15 pages, 17 figures, submitted to A&
Nika2: A mm camera for cluster cosmology
Galaxy clusters constitute a major cosmological probe. However, Planck 2015 results have shown a weak tension between CMB-derived and cluster-derived cosmological parameters. This tension might be due to poor knowledge of the cluster mass and observable relationship. As for now, arcmin resolution Sunyaev-Zeldovich (SZ) observations (e.g. SPT, ACT and Planck) only allowed detailed studies of the intra cluster medium for low redshift clusters (z 0:5) high resolution and high sensitivity SZ observations are needed. With both a wide field of view (6.5 arcmin) and a high angular resolution (17.7 and 11.2 arcsec at 150 and 260 GHz), the NIKA2 camera installed at the IRAM 30-m telescope (Pico Veleta, Spain) is particularly well adapted for these observations. The NIKA2 SZ observation program will map a large sample of clusters (50) at redshifts between 0.5 and 0.9. As a pilot study for NIKA2, several clusters of galaxies have been observed with the pathfinder, NIKA, at the IRAM 30-m telescope to cover the various configurations and observation conditions expected for NIKA2
The NIKA2 large-field-of-view millimetre continuum camera for the 30 m IRAM telescope
Context. Millimetre-wave continuum astronomy is today an indispensable tool for both general astrophysics studies (e.g. star formation, nearby galaxies) and cosmology (e.g. cosmic microwave background and high-redshift galaxies). General purpose, large-field-of-view instruments are needed to map the sky at intermediate angular scales not accessible by the high-resolution interferometers (e.g. ALMA in Chile, NOEMA in the French Alps) and by the coarse angular resolution space-borne or ground-based surveys (e.g. Planck, ACT, SPT). These instruments have to be installed at the focal plane of the largest single-dish telescopes, which are placed at high altitude on selected dry observing sites. In this context, we have constructed and deployed a three-thousand-pixel dual-band (150âGHz andâ260 GHz, respectively 2âmm and 1.15âmm wavelengths) camera to image an instantaneous circular field-of-view of 6.5âarcmin in diameter, and configurable to map the linear polarisation at 260âGHz.
Aims. First, we are providing a detailed description of this instrument, named NIKA2 (New IRAM KID Arrays 2), in particular focussing on the cryogenics, optics, focal plane arrays based on Kinetic Inductance Detectors, and the readout electronics. The focal planes and part of the optics are cooled down to the nominal 150âmK operating temperature by means of an adhoc dilution refrigerator. Secondly, we are presenting the performance measured on the sky during the commissioning runs that took place between October 2015 and April 2017 at the 30-m IRAM telescope at Pico Veleta, near Granada (Spain).
Methods. We have targeted a number of astronomical sources. Starting from beam-maps on primary and secondary calibrators we have then gone to extended sources and faint objects. Both internal (electronic) and on-the-sky calibrations are applied. The general methods are described in the present paper.
Results. NIKA2 has been successfully deployed and commissioned, performing in-line with expectations. In particular, NIKA2 exhibits full width at half maximum angular resolutions of around 11 and 17.5 arcsec at respectively 260 and 150âGHz. The noise equivalent flux densities are, at these two respective frequencies, 33±2 and 8±1 mJy s1/2. A first successful science verification run was achieved in April 2017. The instrument is currently offered to the astronomy community and will remain available for at least the following ten years
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