An innovative blazar classification based on radio jet kinematics

Blazars are usually classified following their synchrotron peak frequency ($\nu F(\nu)$ scale) as high, intermediate, low frequency peaked BL Lacs (HBLs, IBLs, LBLs), and flat spectrum radio quasars (FSRQs), or, according to their radio morphology at large scale, FR~I or FR~II. However, the diversity of blazars is such that these classes seem insufficient to chart the specific properties of each source. We propose to classify a wide sample of blazars following the kinematic features of their radio jets seen in very long baseline interferometry (VLBI). For this purpose we use public data from the MOJAVE collaboration in which we select a sample of blazars with known redshift and sufficient monitoring to constrain apparent velocities. We selected 161 blazars from a sample of 200 sources. We identify three distinct classes of VLBI jets depending on radio knot kinematics: class I with quasi-stationary knots, class II with knots in relativistic motion from the radio core, and class I/II, intermediate, showing quasi-stationary knots at the jet base and relativistic motions downstream. A notable result is the good overlap of this kinematic classification with the usual spectral classification; class I corresponds to HBLs, class II to FSRQs, and class I/II to IBLs/LBLs. We deepen this study by characterizing the physical parameters of jets from VLBI radio data. Hence we focus on the singular case of the class I/II by the study of the blazar BL Lac itself. Finally we show how the interpretation that radio knots are recollimation shocks is fully appropriate to describe the characteristics of these three classes.Comment: 12 pages, 13 figures, accepted by A&

Linking radio and gamma ray emission in Ap Librae

Ap Lib is one of the rare Low Synchrotron Peaked blazars detected so far at TeV energies. This type of source is not properly modelled by standard one-zone leptonic Synchrotron-self-Compton (SSC) emission scenarios. The aim of this paper is to study the relevance of additional components which should naturally occur in a SSC scenario for a better understanding of the emission mechanisms, especially at very high energies (VHE). Methods. We use simultaneous data from a multi-wavelength campaign of Planck, Swift-UVOT and Swift-XRT telescopes carried out in February 2010, as well as quasi-simultaneous data of WISE, Fermi and H.E.S.S. taken in 2010. The multi-lambda emission of Ap Lib is modelled by a blob-in-jet SSC scenario including the contribution of the base of the VLBI extended jet, the radiative blob-jet interaction, the accretion disk and its associated external photon field. We show that signatures of a strong parsec-scale jet and of an accretion disk emission are present in the SED. We can link the observationnal VLBI jet features from MOJAVE to parameters expected for a VHE emitting blob accelerated near the jet base. The VHE emission appears to be dominated by the inverse-Compton effect of the blob relativistic electrons interacting with the jet synchrotron radiation. In such scenario Ap Lib appears as an intermediate source between BL Lac objects and Flat Spectrum Radio Quasars. Ap Lib could be a bright representative of a specific class of blazars, in which the parsec-scale jet luminosity is no more negligible compared to the blob and contributes to the high energy emission via inverse Compton processes.Comment: 12 pages, 7 figures, Accepted for publication in A&

RISK FACTORS’ IDENTIFICATION ACCORDING TO THE DEVELOPMENT OF HEALTHCARE ASSOCIATED INFECTIONS AND MORTALITY BY USING COMPETING MODELS AT TIMONE UNIVERSITY HOSPITAL’S ICU

Whatever their specialty (surgical, medical or both), intensive care units have to take care of patients due to life-threatening conditions as the result of one or even several organ failures. They register the highest mortality rates (Sheng WH, 2005), and the highest numbers of nosocomial infections (Mathieu LM, 2001). There have been numerous studies intended to evaluate the risk factors and the consequences of these infections in ICU (Intensive Care Unit) patients. However the analyses in most of these studies disregard the fact that there are additional competing events such as discharge or death. The study is retrospective. It is based on a total of 250 patients of at least 16 years old and having spent at least 72 hours in ICU in the Timone University Hospital. Several risk factors were studied in two distinct competitive risk models. In the first model, we investigated the nosocomial infections risk factors with such a competing risk model as discharge (patients dead or living). The mortality risk factors were studied in the second model in which the patient being discharged faces the mortality competing risk. 46 patients developed at least one nosocomial episode, and 65 died. The nosocomial infection objectified risk factors are: CVC (causespecific hazard ratio = 9.08; 95% CI 1.10 to 75.20), chronic renal failure (8.99; 95% CI 1.92 to 42.12) and tracheotomy (2.69; 95% CI 1.45 to 5.01). Cancer (2.69; 95% CI 1.48 to 4.89), transplant (7.30; 95% CI 1.83 to 29.19) and the SOFA score (1.36; 95% CI 1.23 to 1.51) are the target factors for mortality risk. Of all the documented scores in the present study the SOFA is the score with the highest predictive capacity as far as death risk is concerned. On the other hand, even if the nosocomial infection alters the event discharge, its impact on mortality is not completely establishe

Shocks in relativistic transverse stratified jets, a new paradigm for radio-loud AGN

The transverse stratification of active galactic nuclei (AGN) jets is suggested by observations and theoretical arguments, as a consequence of intrinsic properties of the central engine (accretion disc + black hole) and external medium. On the other hand, the one-component jet approaches are heavily challenged by the various observed properties of plasmoids in radio jets (knots), often associated with internal shocks. Given that such a transverse stratification plays an important role on the jets acceleration, stability, and interaction with the external medium, it should also induce internal shocks with various strengths and configurations, able to describe the observed knots behaviours. By establishing a relation between the transverse stratification of the jets, the internal shock properties, and the multiple observed AGN jet morphologies and behaviours, our aim is to provide a consistent global scheme of the various AGN jet structures. Working on a large sample of AGN radio jets monitored in very long baseline interferometry (VLBI) by the MOJAVE collaboration, we determined the consistency of a systematic association of the multiple knots with successive re-collimation shocks. We then investigated the re-collimation shock formation and the influence of different transverse stratified structures by parametrically exploring the two relativistic outflow components with the specific relativistic hydrodynamic (SRHD) code AMRVAC. We were able to link the different spectral classes of AGN with specific stratified jet characteristics, in good accordance with their VLBI radio properties and their accretion regimes.Comment: 16 pages, 12 figures, accepted for publication in A&

INCIDENCE, DEPENDENT AND INDEPENDENT RISK FACTORS ASSOCIATED TO NOSOCOMIAL INFECTIONS AND TO THE MORTALITY AT THE INTENSIVE CARE UNIT OF THE TIMONE UNIVERSITY HOSPITAL

ICU (intensive care unit) patients are highly concerned by a risk of nosocomial infection. This is due to the seriousness of the treated pathologies, and more and more to invasive medical procedures, in short, a day-to-day hazard of health care. The aim of this study is to assess the risk factors of nosocomial infections and mortality in ICU, to estimate the proportion of predominant organisms, and to record the disease resistance profiles. This study was based on a total of 250 patients who were at least 16-year old and who had spent at least 72 hours in ICU.Among the 46 patients who developed at least one nosocomial episode, 42 (91.3%) had been hospitalized for a minimum of 6 days (this being the average stay for patients without any nosocomial episode). The mortality rate was 23.9%. The most frequently reported infection was pneumonia contracted through mechanical ventilation, with a percentage of 47.8%, followed by lung infections with a rate of 23.9%. Bacteremia and urinary infections represented 17.4% and 10.4%, respectively. 41.3 % of isolated bacteria were Gram-positive. All of the 46 patients received antibiotics during their stay at the intensive care unit. The results of logistic regression and multivariate analysis (P < 0.05) conclude that the nosocomial event was significantly related to the length of stay OR: 1.073 [1.009 – 1.149], neurological disease OR: 3.21 [1.28 – 8.33] and the presence of a CVC (central venous catheter) OR: 15.3 [1.68 – 507.4]. Additionally, age OR: 1.02 [1.002 – 1.054], cancer OR: 3.07 [1.32– 7.21] and SOFA score >4 OR: 7.58 [2.63 - 29.03] are related to the death risk.In light of this study, we concluded that CVC and neurological disease are high-risk factors for nosocomial infection whereas SOFA score >4 and cancer are identified as high risk factors for mortality

Brownian motion near a partial-slip boundary: A local probe of the no-slip condition

Motivated by experimental evidence of violations of the no-slip boundary condition for liquid flow in micron-scale geometries, we propose a simple, complementary experimental technique that has certain advantages over previous studies. Instead of relying on externally-induced flow or probe motion, we suggest that colloidal diffusivity near solid surfaces contains signatures of the degree of fluid slip exhibited on those surfaces. To investigate, we calculate the image system for point forces (Stokeslets) oriented perpendicular and parallel to a surface with a finite slip length, analogous to Blake's solution for a Stokeslet near a no-slip wall. Notably, the image system for the point source and perpendicular Stokeslet contain the same singularities as Blake's solution; however, each is distributed along a line with a magnitude that decays exponentially over the slip length. The image system for the parallel Stokeslet involves a larger set of fundamental singularities, whose magnitude does not decay exponentially from the surface. Using these image systems, we determine the wall-induced correction to the diffusivity of a small spherical particle located `far' from the wall. We also calculate the coupled diffusivities between multiple particles near a partially-slipping wall. Because, in general, the diffusivity depends on `local' wall conditions, patterned surfaces would allow differential measurements to be obtained within a single experimental cell, eliminating potential cell-to-cell variability encountered in previous experiments. In addition to motivating the proposed experiments, our solutions for point forces and sources near a partial-slip wall will be useful for boundary integral calculations in slip systems.Comment: 34 pages, 5 figure

Bjet_MCMC: A new tool to automatically fit the broadband SEDs of blazars

Multiwavelength observations are now the norm for studying blazars' various states of activity, classifying them, and determining possible underlying physical processes driving their emission. Broadband emission models became unavoidable tools for testing emission scenarios and setting values to physical quantities such as the magnetic field strength, Doppler factor, or shape of the particle distribution of the emission zone(s). We announce here the first public release of a new tool, Bjet_MCMC, that can automatically fit broadband spectral energy distributions (SEDs) of blazars. The complete code is available on GitHub and allows testing leptonic synchrotron self-Compton models (SSC), with or without external inverse-Compton processes from the thermal environment of supermassive black holes (accretion disk and broad line region). The code is designed to be user-friendly and computationally efficient. It contains a core written in C++ and a fully parallelized SED fitting method. The original multi-SSC zones model of Bjet is also available on GitHub but is not included in the MCMC fitting process at the moment. We present the features, performance, and results of Bjet_MCMC, as well as user advice.Comment: 14 pages, 7 figures, 3 tables, Submitted to Ap