Geometrical statistics of the vorticity vector and the strain rate tensor in rotating turbulence

We report results on the geometrical statistics of the vorticity vector obtained from experiments in electromagnetically forced rotating turbulence. A range of rotation rates $\Omega$ is considered, from non-rotating to rapidly rotating turbulence with a maximum background rotation rate of $\Omega=5$ rad/s (with Rossby number much smaller than unity). Typically, in our experiments ${\rm{Re}}_{\lambda}\approx 100$. The measurement volume is located in the centre of the fluid container above the bottom boundary layer, where the turbulent flow can be considered locally statistically isotropic and horizontally homogeneous for the non-rotating case, see van Bokhoven et al., Phys. Fluids 21, 096601 (2009). Based on the full set of velocity derivatives, measured in a Lagrangian way by 3D Particle Tracking Velocimetry, we have been able to quantify statistically the effect of system rotation on several flow properties. The experimental results show how the turbulence evolves from almost isotropic 3D turbulence ($\Omega\lesssim 0.2$ rad/s) to quasi-2D turbulence ($\Omega\approx 5.0$ rad/s) and how this is reflected by several statistical quantities. In particular, we have studied the orientation of the vorticity vector with respect to the three eigenvectors of the local strain rate tensor and with respect to the vortex stretching vector. Additionally, we have quantified the role of system rotation on the self-amplification terms of the enstrophy and strain rate equations and the direct contribution of the background rotation on these evolution equations. The main effect is the strong reduction of extreme events and related (strong) reduction of the skewness of PDFs of several quantities such as, for example, the intermediate eigenvalue of the strain rate tensor and the enstrophy self-amplification term.Comment: 17 pages, 6 figures, 3 table

Task 3- Deliverable 5

Il data-base dei dati accelerometrici italiani (Italian Strong Motion Data Base) copre un periodo di tempo di oltre 20 anni durante i quali non solo le reti sismiche italiane hanno subito una evoluzione notevolissima, ma l’intera sismologia mondiale e la tecnologia ad essa applicata è stata completamente rivoluzionata. La rete Sismica Nazionale gestita dall’INGV (ING fino al 1999), è cresciuta da 12 strumenti riportati nei bollettini del 1972 a oltre 180 nel 2004. Il Bollettino Sismico Italiano dell’anno 1972 include le fasi di 6 sismometri per un terremoto di magnitudo 5 avvenuto al largo di Ancona il 14 giugno 1972. Un terremoto di magnitudo analoga avvenuto il 25 novembre 2004 nell’Adriatico centrale, ben più lontano del precedente dalle coste italiane, è stato registrato da oltre 70 stazioni della Rete Sismica Nazionale. Occorre tenere presente questi dati nell’utilizzo del data-base accelerometrico perché la precisione con cui sono stati valutati i parametri ipocentrali dei terremoti è variata nell’arco di tempo coperto dal data-base di un ordine di grandezza

Finite-size scaling as a way to probe near-criticality in natural swarms

Collective behaviour in biological systems is often accompanied by strong correlations. The question has therefore arisen of whether correlation is amplified by the vicinity to some critical point in the parameters space. Biological systems, though, are typically quite far from the thermodynamic limit, so that the value of the control parameter at which correlation and susceptibility peak depend on size. Hence, a system would need to readjust its control parameter according to its size in order to be maximally correlated. This readjustment, though, has never been observed experimentally. By gathering three-dimensional data on swarms of midges in the field we find that swarms tune their control parameter and size so as to maintain a scaling behaviour of the correlation function. As a consequence, correlation length and susceptibility scale with the system's size and swarms exhibit a near-maximal degree of correlation at all sizes.Comment: Selected for Viewpoint in Physics; PRL Editor's Suggestio

Collective behaviour without collective order in wild swarms of midges

Collective behaviour is a widespread phenomenon in biology, cutting through a huge span of scales, from cell colonies up to bird flocks and fish schools. The most prominent trait of collective behaviour is the emergence of global order: individuals synchronize their states, giving the stunning impression that the group behaves as one. In many biological systems, though, it is unclear whether global order is present. A paradigmatic case is that of insect swarms, whose erratic movements seem to suggest that group formation is a mere epiphenomenon of the independent interaction of each individual with an external landmark. In these cases, whether or not the group behaves truly collectively is debated. Here, we experimentally study swarms of midges in the field and measure how much the change of direction of one midge affects that of other individuals. We discover that, despite the lack of collective order, swarms display very strong correlations, totally incompatible with models of noninteracting particles. We find that correlation increases sharply with the swarm's density, indicating that the interaction between midges is based on a metric perception mechanism. By means of numerical simulations we demonstrate that such growing correlation is typical of a system close to an ordering transition. Our findings suggest that correlation, rather than order, is the true hallmark of collective behaviour in biological systems.Comment: The original version has been split into two parts. This first part focuses on order vs. correlation. The second part, about finite-size scaling, will be included in a separate paper. 15 pages, 6 figures, 1 table, 5 video

Edge Selection in Bilinear Dynamical Networks

In large-scale networks, agents (e.g., sensors and actuators) and links (e.g., couplings and communication links) can fail or be (cyber-)attacked. In this paper, we focus on continuous-time bilinear networks, where additive disturbances model attack/uncertainty on agents/states (a.k.a. node disturbances) and multiplicative disturbances model attack/uncertainty on couplings between agents/states (a.k.a. link disturbances). We then investigate a network robustness notion in terms of the underlying digraph of the network, and structure of exogenous uncertainties/attacks. Specifically, we define the robustness measure using the H2-norm of the network and calculate it in terms of the reachability Gramian of the bilinear system. The main result shows that under certain conditions, the measure is supermodular over the set of all possible attacked links. The supermodular property facilitates the efficient solution finding of the optimization problem. We conclude the paper with a few examples illustrating how different structures can make the system more or less vulnerable to malicious attacks on links and present our concluding remarks.Comment: 6 pages, 2 figure

A Bridge between CP violation at Low Energies and Leptogenesis

We discuss the possibility of relating the size and sign of the observed baryon asymmetry of the universe to CP violation observable at low energies, in a framework where the observed baryon asymmetry is produced by leptogenesis through the out of the equilibrium decay of heavy Majorana neutrinos. We identify the CP violating phases entering in leptogenesis as well as those relevant for CP violation at low energies in the minimal seesaw model. We show that although in general there is no relation between these two sets of phases, there are specific frameworks in which such a connection may be established and we give a specific grand unification inspired example where such a connection does exist. We construct weak-basis invariants related to CP violation responsible for leptogenesis, as well as those relevant for CP violation at low energies

Desarrollo y validación de un modelo numérico para el análisis de uniones abulonadas en materiales compuestos

La combinación de bajo peso y alta resistencia que brindan los materiales compuestos, los posiciona conveniente en aplicaciones estructurales exigentes, sin embargo es conocido que la vinculación o unión entre elementos estructurales fabricados en compuestos es un punto crítico. En este trabajo se desarrolla un modelo numérico para estudiar una unión abulonada de solape simple de dos placas de material compuesto. El análisis del problema se hace empleando un código de elementos finitos, y el modelo desarrollado contempla el múltiple contacto entre las placas de compuesto, el cuerpo del bulón y las arandelas. Las placas se consideran fabricadas en fibra de carbono unidireccional en una matriz de epoxi, las arandelas son de acero, mientras que el bulón y la tuerca se consideran construidas en titanio. Los resultados de este análisis computacional concuerdan muy bien con los obtenidos a nivel experimental por otros autores, no solo en cuanto a nivel tensional sino también en las deformaciones y distorsiones mostradas por las placas. A partir de los resultados satisfactorios obtenidos en este trabajo, es posible proseguir con el estudio del comportamiento de otras configuraciones de abulonado.Fil: Rodriguez, Cristhian. Universidad de las Fuerzas Armadas. Departamento de Seguridad y Defensa. Área de Ciencias Aeronáuticas; Argentina.Fil: Castello, Walter B. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Estructuras; Argentina.Ingeniería Aeroespacia

Modulation of Hydrogen Peroxide Production in Cellular Systems by Low Level Magnetic Fields

Increased generation of reactive oxygen species (ROS) and an altered redox status have long been observed in cancer cells, suggesting that ROS might be involved in the development of these cells. However, recent studies suggest that inducing an excess of ROS in cancer cells can be exploited for therapeutic benefits. Cancer cells in advanced stage tumors frequently exhibit multiple genetic alterations and high oxidative stress, suggesting that it might be possible to preferentially modulate the development of these cells by controlling their ROS production. Low levels of ROS are also important for the development and survival of normal cells. In this manuscript, we present data on the influence of the suppression of the Earth's magnetic field (low level magnetic fields or LLF) which magnitudes range from 0.2 µT to 2 µT on the modulation of hydrogen peroxide (H2O2) in human fibrosarcoma cancer cell line HT1080, pancreatic AsPC-1 cancer cell line, and bovine pulmonary artery endothelial cells (PAEC) exposed to geomagnetic field (control; 45 µT–60 µT). Reduction of the Earth's magnetic field suppressed H2O2 production in cancer cells and PAEC. The addition of catalase and superoxide dismutase (SOD) mimetic MnTBAP inhibited the magnetic field effect. Modulating ROS production by magnetic fields may open new venues of biomedical research and therapeutic strategies

Modulation of humoral immune response to oral BCG vaccination by Mycobacterium bovis BCG Moreau Rio de Janeiro (RDJ) in healthy adults

BACKGROUND: Oral administration of BCG was the route initially used by Calmette and Guérin, but was replaced by intradermal administration in virtually all countries after the Lubeck accident. However, Brazil continued to administer oral BCG Moreau RDJ, which was maintained until the mid-1970s when it was substituted by the intradermal route. Although BCG vaccination has been used in humans since 1921, little is known of the induced immune response. The aim of this study was to analyse immunological responses after oral vaccination with M. bovis BCG Moreau RDJ. METHODS: This study in healthy volunteers has measured cellular and humoral aspects of the immunological response to oral M. bovis BCG Moreau RDJ in Rio de Janeiro, Brazil. T-cell trafficking and Th(1 )and Th(2 )cytokine responses are described, as well as isotype-specific antibody production using novel techniques. RESULTS: Oral immunisation has no adverse effects. We have shown that there are cellular and humoral immunological responses after oral immunisation. Oral revaccination does not induce a positive skin test in responsive individuals and multiple booster orally was able to induce modulation in humoral immunological responses (switch from IgG to IgA) in previously immunised subjects and incapable of inducing tolerance. In contrast, the cellular immune response does not differ between vaccinated individuals with positive and negative skin test reactions. CONCLUSION: All subjects, including those who did not respond to the skin test at study commencement, were capable of mounting humoral and cellular immune response to the antigens tested