Radio jets from stellar tidal disruptions

A star that passes too close to a massive black hole will be torn apart by tidal forces. The flare of photons emitted during the accretion of the stellar debris is predicted to be observable and candidates of such events have been observed at optical to X-ray frequencies. If a fraction of the accreted material is fed into a jet, tidal flares should be detectable at radio frequencies too, thus comprising a new class of rare radio transients. Using the well-established scaling between accretion power and jet luminosity and basic synchrotron theory, we construct an empirically-rooted model to predict the jet luminosity for a time-dependent accretion rate. We apply this model to stellar tidal disruptions and predict the snapshot rate of these events. For a small angle between the observer and the jet, our model reproduces the observed radio flux of the tidal flare candidate GRB 110328A. We find that future radio surveys will be able to test whether the majority of tidal disruptions are accompanied by a jet.Comment: Accepted for publication in MNRAS letter

Tweeting Behaviour during Train Disruptions within a City

In a smart city environment, citizens use social media for communicating and reporting events. Existing work has shown that social media tools, such as Twitter and Facebook, can be used as social sensors to monitor events in real-time as they happen (e.g. riots, natural disasters and sport events). In this paper, we study the reactions of citizens in social media towards train disruptions within a city. Our study using 30 days of tweets in a large city shows that citizens react differently to train disruptions by, for instance, displaying unique behaviours in tweeting depending on the time of the disruption. Specifically, for working days, tweets related to train disruptions are typically generated during rush hour periods. In contrast, during weekends, urban citizens tended to tweet about train disruptions during late evenings. Using these insights, we develop a supervised approach to predict whether a train disruption tweet will be retweeted and propagated on the social network, by using features, such as time, user, and the content of tweets. Our experimental results show that we can effectively predict when a train disruption tweet is retweeted by using such features

Feminist Disruptions in Mexican Art, 1975 - 1987

Between 1975 and 1987 feminism in the arts in Mexico delineated a unique situation, one without parallel in the panorama of Latin American art. In a group of exhibitions, works and texts, women's place in Mexican art was critically analyzed, unfolding a broad map of positions. Although a chronology and list of names of the artists who shaped this scenario have been established, the intervention that each work proposed in the debate on women's place and the feminine that gained visibility during those years has not yet been examined. Based on a situated analysis of these works, this article proposes to discuss these works' intervention in configuring how the debate on artistic feminism took shape during this period in Mexico.Fil: Giunta, Andrea Graciela. University of Texas at Austin; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Multiple Tidal Disruptions as an Indicator of Binary Super-Massive Black Hole Systems

We find that the majority of systems hosting multiple tidal disruptions are likely to contain hard binary SMBH systems, and also show that the rates of these repeated events are high enough to be detected by LSST over its lifetime. Therefore, these multiple tidal disruption events provide a novel method to identify super-massive black hole (SMBH) binary systems with parsec to sub-parsec separations. The rates of tidal disruptions are investigated using simulations of non-interacting stars initially orbiting a primary SMBH and the potential of the model stellar cusp. The stars are then evolved forward in time and perturbed by a secondary SMBH inspiraling from the edge of the cusp to its stalling radius. We find with conservative magnitude estimates that the next generation transient survey LSST should detect multiple tidal disruptions in approximately 3 galaxies over 5 years of observation, though less conservative estimates could increase this rate by an order of magnitude.Comment: 5 pages, 3 figure

Helical Disruptions in Small Loops of DNA

The thermodynamical stability of DNA minicircles is investigated by means of path integral techniques. Hydrogen bonds between base pairs on complementary strands can be broken by thermal fluctuations and temporary fluctuational openings along the double helix are essential to biological functions such as transcription and replication of the genetic information. Helix unwinding and bubble formation patterns are computed in circular sequences with variable radius in order to analyze the interplay between molecule size and appearance of helical disruptions. The latter are found in minicircles with $< 100$ base pairs and appear as a strategy to soften the stress due to the bending and torsion of the helix.Comment: International Conference on Mathematical Modeling in Physical Sciences, August 28-31, 2014, Madrid, Spai

RWU Cybersecurity Expert Works on State Initiative to Combat Cyber Threats

As a founding member of the state\u27s Joint Cyber Task Force, RWU Cybersecurity Program Director Douglas White battles cyber disruptions in R.I.