Galactic conformity measured in semi-analytic models

We study the correlation between the specific star formation rate of central galaxies and neighbour galaxies, also known as 'galactic conformity', out to 20 Mpc/h using three semi-analytic models (SAMs, one from L-GALAXIES and other two from GALFORM). The aim is to establish whether SAMs are able to show galactic conformity using different models and selection criteria. In all the models, when the selection of primary galaxies is based on an isolation criterion in real space, the mean fraction of quenched galaxies around quenched primary galaxies is higher than that around star-forming primary galaxies of the same stellar mass. The overall signal of conformity decreases when we remove satellites selected as primary galaxies, but the effect is much stronger in GALFORM models compared with the L-GALAXIES model. We find this difference is partially explained by the fact that in GALFORM once a galaxy becomes a satellite remains as such, whereas satellites can become centrals at a later time in L-GALAXIES. The signal of conformity decreases down to 60% in the L-GALAXIES model after removing central galaxies that were ejected from their host halo in the past. Galactic conformity is also influenced by primary galaxies at fixed stellar mass that reside in dark matter haloes of different masses. Finally, we explore a proxy of conformity between distinct haloes. In this case the conformity is weak beyond ~ 3 Mpc/h (<3% in L-GALAXIES, <1-2% in GALFORM models). Therefore, it seems difficult that conformity is directly related with a long-range effect.Comment: 15 pages, 7 figures. Accepted for publication in MNRA

Applying PII fingerprints in security incident analysis

Regulations in many countries govern the use of personally identifiable information (PII) in IT systems. A key aspect of these regulations is to retain PII only as long as necessary and delete it immediately afterwards. Organizations should also consider retaining PII only for the minimum period as business requirements demand it for liability reasons. A difficult sit-uation arises for an organization if the possibility of a compromise of PII is detected after the PII has been deleted. Today, in such a situation, the scope of the potential compromise cannot easily be ascertained. Furthermore, the owner of the PII cannot easily be informed. We propose a novel algorithm to generate PII fingerprints which allows the determination of the scope of the affected PII in case a compromise is confirmed. The benefit is the ability to determine the exact scope of a potential compromise

Numerical implementation of a mixed finite element formulation for convection-diffusion problems

This document aims to the numerical solution of convection-diffusion problems in a fluid dynamics context by means of the Finite Element Method (FEM). It describes the classical finite element solution of convection-diffusion problems and presents the implementation and validation of a new formulation for improving the accuracy of the standard approach. On first place, the importance and need of numerical convection-diffusion models for Computational Fluid Dynamics (CFD) is emphasized, highlighting the similarities between the convection-diffusion equation and the governing equations of fluid dynamics for incompressible flow. The basic aspects of the finite element method needed for the standard solution of general convection-diffusion problems are then explained and applied to the steady state case. These include the weak formulation of the initial boundary value problem for the convection-diffusion equation and the posterior finite element spatial discretization of the weak form based on the Galerkin method. After their application to the steady transport equation a simple numerical test is performed to show that the standard Galerkin formulation is not stable in convection-dominated situations, and the need for stabilization is justified. Attention is then focused on the analysis of the truncation error provided by the Galerkin formulation, leading to the derivation of a classical stabilization technique based on the addition of artificial diffusion along the flow direction, the so-called streamline-upwind (SU) schemes. Next, a more general and modern stabilization approach known as the Sub-Grid-Scale (SGS) method is described, showing that SU schemes are a particular case of it. Taking into account all the concepts explained, a new mixed finite element formulation for convection-diffusion problems is presented. It has been proposed by Dr. Riccardo Rossi, a researcher from the International Center for Numerical Methods in Engineering (CIMNE), and consists on extending the original convection-diffusion equation to a system in mixed form in which both the unknown variable and its gradient are computed simultaneously, leading to an increase in the convergence rate of the solution. The formulation, which had not been tested before, is then implemented and validated by means of a multiphysics finite element software called \texttt{Kratos}. Eventually, the obtained results are analyzed, showing the improved performance of the mixed formulation in pure diffusion problems

Study of unstructured finite volume methods for the solution of the Euler equations

Development of an unstructured finite volume solver for the numerical solution of high-speed flows using the Euler equation set.This work deals with the numerical solution of inviscid compressible flows by means of the Euler equations. It focuses on the description of an unstructured finite volume method for these equations and its numerical application to solve external, two-dimensional steady problems. On first place, the standard formulation of the Euler equations is presented, reviewing the most important properties that characterize their mathematical behavior. The hyperbolic nature of the system is discussed, emphasizing the fundamental importance of taking into account the propagation of information in the flow field in order to obtain physically meaningful solutions, which also leads to a description of how the boundary conditions should be treated to avoid undesirable behaviors. To complete this presentation, a dimensionless form of the equations is derived, which provides substantial advantages to the numerical solution. The attention is then focused on the unstructured finite volume formulation, which is based on a central approximation of the fluxes at the volume interfaces. According to the need of properly accounting for the propagation of characteristic variables, the requirement to add artificial dissipation terms to the central discretization is justified. Then, two classical forms of artificial dissipation are defined, namely, the first-order upwind scheme and the Jameson-Schmidt-Turkel high-order model, detailing how to adapt the formulation of the dissipation terms to an unstructured mesh. Eventually, the time integration of the spatially discretized equations is assessed. With the objective of performing a practical implementation of the theoretical concepts studied, the development of a numerical solver is presented next, briefly describing the program structure and characteristics. After that, five different test cases are solved with the purpose of validating the code, consisting on two transonic flows around a NACA0012 airfoil and three supersonic examples, respectively around a NACA0012 airfoil, a double wedge airfoil and circular cylinder. The results obtained for each case are then analyzed and compared against reference solutions, showing an overall satisfactory performance of the solver developed

Improving CAS Capabilities: New Rules for Computing Improper Integrals

There are diferent applications in Engineering that require to compute improper integrals of the first kind (integrals defined on an unbounded domain) such as: the work required to move an object from the surface of the earth to in nity (Kynetic Energy), the electric potential created by a charged sphere, the probability density function or the cumulative distribution function in Probability Theory, the values of the Gamma Functions(wich useful to compute the Beta Function used to compute trigonometrical integrals), Laplace and Fourier Transforms (very useful, for example in Differential Equations).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Using extensions of the residue theorem for improper integrals computations with CAS

The computation of improper integrals of the rst kind (integrals on unbounded domain) are used in di erent applications in Engineering (for example in Kynetic Energy, electric potential, probability density functions, Gamma and Beta functions, Laplace and Fourier Transforms, Di erential Equations, . . . ). Nowadays, Computer Algebra Systems (CAS) are being used for developing such computations. But in many cases, some CAS lack of the appropriate rules for computing some of these improper integrals. In a previous talk in ESCO 2016 and a later extension, we introduced new rules for computing improper integrals of the rst kind using some results from Advanced Calculus Theories (Residue Theorem, Laplace and Fourier Transforms) aimed to improve CAS capabilities on this topic. In this talk, we develop new rules for computing other types of improper integrals using different applications from extended versions of the Residue Theorem. We will show some examples of such improper integrals that current CAS can not compute. Using extensions of the Residue Theorem in Complex Analysis, we will be able to develop new rules schemes for these improper integrals. These new rules will improve the capabilities of CAS, making them able to compute more improper integrals.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Flexible comparative genomics of prokaryotic transcriptional regulatory networks

Comparative genomics methods enable the reconstruction of bacterial regulatory networks using available experimental data. In spite of their potential for accelerating research into the composition and evolution of bacterial regulons, few comparative genomics suites have been developed for the automated analysis of these regulatory systems. Available solutions typically rely on precomputed databases for operon and ortholog predictions, limiting the scope of analyses to processed complete genomes, and several key issues such as the transfer of experimental information or the integration of regulatory information in a probabilistic setting remain largely unaddressed. Here we introduce CGB, a flexible platform for comparative genomics of prokaryotic regulons. CGB has few external dependencies and enables fully customized analyses of newly available genome data. The platform automates the merging of experimental information and uses a gene-centered, Bayesian framework to generate and integrate easily interpretable results. We demonstrate its flexibility and power by analyzing the evolution of type III secretion system regulation in pathogenic Proteobacteria and by characterizing the SOS regulon of a new bacterial phylum, the Balneolaeota. Our results demonstrate the applicability of the CGB pipeline in multiple settings. CGB's ability to automatically integrate experimental information from multiple sources and use complete and draft genomic data, coupled with its non-reliance on precomputed databases and its easily interpretable display of gene-centered posterior probabilities of regulation provide users with an unprecedented level of flexibility in launching comparative genomics analyses of prokaryotic transcriptional regulatory networks. The analyses of type III secretion and SOS response regulatory networks illustrate instances of convergent and divergent evolution of these regulatory systems, showcasing the power of formal ancestral state reconstruction at inferring the evolutionary history of regulatory networks

Teaching Partial Differential Equations With a CAS

It is very common that Engineering students nd difficulties when studying advanced Mathematics subjects. To help in the teaching and learning process of such subjects, the teacher can use an adequate mathematical software. But not always the used given to these specific pieces of software is the right one. The use of a Computer Algebra System (CAS) to achieve this goal is a good idea mainly because programming with a CAS, the solution to a problem can be obtained step by step. This way, the student can check all the intermediate steps to get the solution and can nd the step or steps where the student made a mistake. In this talk, we introduce SPDES, a Stepwise Partial Differential Equation Solver (an extension of SFOPDES). SPDES deals with some second order PDE in addition to the first order PDE considered in SFOPDES. SPDES can be used as a self tutorial for PDE since it solves, step by step, the typical exercises within the topic. The type of PDE that SPDES can solve are: Pfaff Differential Equations, Quasi-linear PDE, Lagrange-Charpit Method for first order PDE, Heat equation, Wave equation and Laplace's equation. SPDES has been developed using the programming capabilities of the CAS Derive, providing not only the final result but also, optionally, the display of all the steps needed to solve typical exercises on PDE.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech