Linear stability analysis of magnetized relativistic rotating jets

We carry out a linear stability analysis of a magnetized relativistic rotating cylindrical jet flow using the approximation of zero thermal pressure. We identify several modes of instability in the jet: Kelvin-Helmholtz, current driven and two kinds of centrifugal-buoyancy modes -- toroidal and poloidal. The Kelvin-Helmholtz mode is found at low magnetization and its growth rate depends very weakly on the pitch parameter of the background magnetic field and on rotation. The current driven mode is found at high magnetization, the values of its growth rate and the wavenumber, corresponding to the maximum growth, increase as we decrease the pitch parameter of the background magnetic field. This mode is stabilized by rotation, especially, at high magnetization. The centrifugal-buoyancy modes, arising due to rotation, tend also to be more stable when magnetization is increased. Overall, relativistic jet flows appear to be more stable with respect to their non-relativistic counterpart.Comment: 15 pages, 15 figures, accepted for pubblication in MNRA

A Particle Module for the PLUTO code: II - Hybrid Framework for Modeling Non-thermal emission from Relativistic Magnetized flows

We describe a new hybrid framework to model non-thermal spectral signatures from highly energetic particles embedded in a large-scale classical or relativistic MHD flow. Our method makes use of \textit{Lagrangian} particles moving through an Eulerian grid where the (relativistic) MHD equations are solved concurrently. Lagrangian particles follow fluid streamlines and represent ensembles of (real) relativistic particles with a finite energy distribution. The spectral distribution of each particle is updated in time by solving the relativistic cosmic ray transport equation based on local fluid conditions. This enables us to account for a number of physical processes, such as adiabatic expansion, synchrotron and inverse Compton emission. An accurate semi-analytically numerical scheme that combines the method of characteristics with a Lagrangian discretization in the energy coordinate is described. In presence of (relativistic) magnetized shocks, a novel approach to consistently model particle energization due to diffusive shock acceleration has been presented. Our approach relies on a refined shock-detection algorithm and updates the particle energy distribution based on the shock compression ratio, magnetic field orientation and amount of (parameterized) turbulence. The evolved distribution from each \textit{Lagrangian} particle is further used to produce observational signatures like emission maps and polarization signals accounting for proper relativistic corrections. We further demonstrate the validity of this hybrid framework using standard numerical benchmarks and evaluate the applicability of such a tool to study high energy emission from extra-galactic jets.Comment: 23 pages, 14 figures, Accepted for publication in The Astrophysical Journa

Infectious diseases in Emilia-Romagna (Italy) dairy farms: ecological modelling and network analysis

Studying the spread of infectious diseases at the humans-domestic animals-wild animals interface is fundamental in order to preserve all three named compartments health. In particular, infection in livestock produced several impacts during the last two decades, threatening the sustainability of farming in different areas all over the world. The focus of this thesis is to disentangle the potential pathogens spread through farming systems, using ecological modelling methods. I worked on the dairy cattle system in the Emilia-Romagna (ER) region and in the Province of Parma (Italy). In the first chapter I reviewed the published models for bovine tuberculosis (bTB), a very dangerous disease for both cattle and humans health worldwide. In particular, I focused on the understanding of models structure and assumptions. In the second chapter, I evaluated the performance of bTB surveillance system in the ER system, a bTB-free region since 2007. The surveillance system is composed by three detection methods: on-farm routine skin-testing, exchanged cattle skin-testing, and slaughterhouse carcass inspection. In order to evaluate their performances, I built a stochastic network model, able to represent both within-farm and between-farm bTB dynamics, and calibrated on available data on ER dairy farms. The surveillance system was assessed through the comparative analysis of a number of statistics, including the time required for epidemic detection and the total number of infected farms during the epidemic. Results showed that slaughterhouse inspection and on-farm routine surveillance mainly contributed both to the surveillance system effectiveness, while exchanged cattle testing was relatively marginal. In the third chapter of my thesis, I analysed the indirect contacts existing between farms. These contacts are due to fomites mediated infections between farms, caused by farm-visitors moving between farms. In my case of study I analysed: private and government veterinarians, and milk trucks. My results showed that all three indirect contacts networks considered was very different in respect to direct one, and that they created an higher number of between-farm connections in respect to cattle movements. This suggested that the indirect contact route of transmission should not be neglected in control and surveillance effective strategies for highly contagious diseases

Magnetocentrifugal mechanism of pair creation in AGN

In the manuscript, we study the efficiency of pair creation by means of the centrifugal mechanism. The strong magnetic field and the effects of rotation, which always take place in Kerr-type black holes, guarantee the frozen-in condition, leading to the generation of an exponentially amplifying electrostatic field. This field, when reaching the Schwinger threshold, leads to efficient pair production. The process has been studied for a wide range of AGN luminosities and black hole masses, and it was found that the mechanism is very efficient, indicating that for AGNs where centrifugal effects are significant, the annihilation lines in the MeV range will be very strong.Comment: 15 pages, 5 figure

The different flavors of extragalactic jets: Magnetized relativistic flows

We perform three-dimensional numerical simulations of magnetized relativistic jets propagating in a uniform density environment in order to study the effect of the entrainment and the consequent deceleration, extending a previous work in which magnetic effects were not present. As in previous papers, our aim is to understand the connection between the jet properties and the resulting Fanaroff-Riley classification. We consider jets with different low densities, and therefore low power, and different magnetizations. We find that lower magnetization jets effectively decelerate to sub-relativistic velocities and may then result in an FR~I morphology on larger scales. At the opposite, in the higher magnetization cases, the entrainment and consequent deceleration are substantially reduced. }Comment: 13 pages, 11 figures, accepted in A&

Synchronous primary papillary breast cancer, medullary thyroid carcinoma and neuroendocrine tumor in postmenopausal woman.

Multiple endocrine neoplasia are syndromes involving two or more endocrine tissues, often correlated to RET proto-oncogene mutations. We herein present the first reported case of a 57-years-old woman with three synchronous primary cancers of breast (papillary), thyroid (medullary) and pancreas (neuroendocrine), the latter with liver metastasis. The patient first underwent surgery for papillary breast cancer with axillary lymph nodes metastases. A staging whole body computerized tomography (CT) showed a right lateral cervical lymph node, pancreatic inhomogeneity, peri-pancreatic nodes and a single liver metastasis. The poor response to an antracycline and taxane-based chemotherapy, the good performance status of patient, and associated symptoms, suggested a different origin for pancreatic and hepatic lesions. A careful re-evaluation of clinical history, an octreotide-labeled scan and an immunohistochemical analysis, on both hepatic and pancreatic tissues and on laterocervical lymph node, determined the diagnosis of synchronous papillary breast cancer, pancreatic neuroendocrine tumor (pNET) with liver metastasis and an occult medullary thyroid carcinoma in a patient who had proto-oncogene RET wild type

Modelling farm-to-farm disease transmission through personnel movements:From visits to contacts, and back

AbstractInfectious diseases in livestock can be transmitted through fomites: objects able to convey infectious agents. Between-farm spread of infections through fomites is mostly due to indirect contacts generated by on-farm visits of personnel that can carry pathogens on their clothes, equipment, or vehicles. However, data on farm visitors are often difficult to obtain because of the heterogeneity of their nature and privacy issues. Thus, models simulating disease spread between farms usually rely on strong assumptions about the contribution of indirect contacts on infection spread. By using data on veterinarian on-farm visits in a dairy farm system, we built a simple simulation model to assess the role of indirect contacts on epidemic dynamics compared to cattle movements (i.e. direct contacts). We showed that including in the simulation model only specific subsets of the information available on indirect contacts could lead to outputs widely different from those obtained with the full-information model. Then, we provided a simple preferential attachment algorithm based on the probability to observe consecutive on-farm visits from the same operator that allows overcoming the information gaps. Our results suggest the importance of detailed data and a deeper understanding of visit dynamics for the prevention and control of livestock diseases.</jats:p

Simulating the dynamics and non-thermal emission of relativistic magnetised jets I. Dynamics

We have performed magneto-hydrodynamic simulations of relativistic jets from supermassive blackholes over a few tens of kpc for a range of jet parameters. One of the primary aims were to investigate the effect of different MHD instabilities on the jet dynamics and their dependence on the choice of jet parameters. We find that two dominant MHD instabilities affect the dynamics of the jet, small scale Kelvin- Helmholtz (KH) modes and large scale kink modes, whose evolution depend on internal jet parameters like the Lorentz factor, the ratio of the density and pressure to the external medium and the magnetisation and hence consequently on the jet power. Low power jets are susceptible to both instabilities, kink modes for jets with higher central magnetic field and KH modes for lower magnetisation. Moderate power jets do not show appreciable growth of kink modes, but KH modes develop for lower magnetisation. Higher power jets are generally stable to both instabilities. Such instabilities decelerate and decollimate the jet while inducing turbulence in the cocoon, with consequences on the magnetic field structure. We model the dynamics of the jets following a generalised treatment of the Begelman-Cioffi relations which we present here. We find that the dynamics of stable jets match well with simplified analytic models of expansion of non self-similar FRII jets, whereas jets with prominent MHD instabilities show a nearly self-similar evolution of the morphology as the energy is more evenly distributed between the jet head and the cocoon.Comment: Accepted for publication in MNRA

Multilayer and multiplex networks: an introduction to their use in veterinary epidemiology

This is the final version. Available from Frontiers Media via the DOI in this record.Contact network analysis has become a vital tool for conceptualizing the spread of pathogens in animal populations and is particularly useful for understanding the implications of heterogeneity in contact patterns for transmission. However, the transmission of most pathogens cannot be simplified to a single mode of transmission and, thus, a single definition of contact. In addition, host-pathogen interactions occur in a community context, with many pathogens infecting multiple host species and most hosts being infected by multiple pathogens. Multilayer networks provide a formal framework for researching host-pathogen systems in which multiple types of transmission-relevant interactions, defined as network layers, can be analyzed jointly. Here, we provide an overview of multilayer network analysis and review applications of this novel method to epidemiological research questions. We then demonstrate the use of this technique to analyze heterogeneity in direct and indirect contact patterns amongst swine farms in the United States. When contact among nodes can be defined in multiple ways, a multilayer approach can advance our ability to use networks in epidemiological research by providing an improved approach for defining epidemiologically relevant groups of interacting nodes and changing the way we identify epidemiologically important individuals such as superspreaders.Biotechnology and Biological Sciences Research Council (BBSRC)NIFA-NSF-NIH Ecology and Evolution of Infectious Disease awardAgriculture and Food Research InitiativeSwine Health Information Center (SHIC)University of MinnesotaUniversity of Exete