Disk-Halo Interaction - I. Three-Dimensional Evolution of the Galactic Disk

The results of a three-dimensional model for disk-halo interaction are presented here. The model considers explicitly the input of energy and mass by isolated a nd correlated supernovae in the disk. Once disrupted by the explosions, the disk never returns to its initial state. Instead it approaches a state where a thin HI disk is formed in the Galactic plane overlayed by thick HI and HII gas disk w ith scale heights of 500 pc and of 1 to 1.5 kpc, respectively. The upper parts o f the thick HII disk (the diffuse ionized medium) act as a disk-halo interface a nd its formation and stability are directly correlated to the supernova rate per unit area in the simulated disk.Comment: 19 pages, 18 figures; to appear in Monthly Notices of Royal Astronomical Societ

Lisa Blas: Meet Me at the Mason Dixon

The Schmucker Art Gallery at Gettysburg College is extremely pleased to mount the remarkable series of paintings, photographs, and mixed-media installation by contemporary artist Lisa Blas entitled Meet Me at the Mason Dixon. This exhibition is an official part of Gettysburg area’s 150th Commemoration of the American Civil War as well as Gettysburg College’s Kick-Off event for this significant anniversary. Gettysburg provides an especially appropriate backdrop for the exhibition, as the artist took the history of this “hallowed ground” and its current resonances as the subject of her work. Blas traveled the Gettysburg National Military Park, as well as to the Antietam National Battlefield, the Smithsonian Institution, the National Archives and the Museum of the Confederacy in Richmond, Virginia, among many other sites, to investigate how national identity and cultural myths are shaped in response to this momentous period of American history. The title of this exhibition, Meet Me at the Mason Dixon, invokes an encounter at a historical boundary line known for centuries of conflict. The Mason-Dixon Line originally was intended to solve a British colonial dispute. Later, it divided the northern from the southern United States based on the legality of slavery, and as such, symbolizes the massive fracturing of the country during the American Civil War. To contemporary artist Lisa Blas, however, the Mason-Dixon emblematizes the tensions implicit in the concept of historical memory. How are traumas witnessed and remembered? What becomes codified as history, and what other narratives are thereby repressed? What age-old divisions haunt us in the present? Blas comprehends such questions as open-ended, visualizing the past as fundamentally, and persistently, conflicted. [excerpt]https://cupola.gettysburg.edu/artcatalogs/1006/thumbnail.jp

Traffic Sign Recognition System

The research group CAOS at the Computing Department of the Carlos III University of Madrid, Spain, offers an efficient recognition system for traffic signs using a set of classifiers. This system can be used as part of an active security system in cars. The fact that the system is based on a set of classifiers facilitates a distributed implementation, resulting in cheaper hardware and an improvement in fault-tolerance.Contrato Programa de Comercialización e Internacionalización. Sistema Regional de Investigación Científica e Innovación Tecnológica. (Comunidad de Madrid; Universidad Carlos III de Madrid

From graphs to tensegrity structures: Geometric and symbolic approaches

A form-finding problem for tensegrity structures is studied; given an abstract graph, we show an algorithm to provide a necessary condition for it to be the underlying graph of a tensegrity in $\mathbb{R}^d$ (typically $d=2,3$) with vertices in general position. Furthermore, for a certain class of graphs our algorithm allows to obtain necessary and sufficient conditions on the relative position of the vertices in order to underlie a tensegrity, for what we propose both a geometric and a symbolic approach.Comment: 17 pages, 8 figures; final versio

Non-relativistic free-free emission due to n−n-distribution of electrons - Radiative cooling and thermally averaged and total Gaunt factors

Tracking the thermal evolution of plasmas, characterized by an n-distribution, using numerical simulations, requires the determination of the emission spectra and of the radiative losses due to free-free emission from the correspond- ing temperature averaged and total Gaunt factors. Detailed calculations of the latter are presented, associated to n-distributed electrons with the parameter n ranging from 1 (corresponding to the Maxwell-Boltzmann distribu- tion) to 100. The temperature averaged and total Gaunt factors, with decreasing n tend to those obtained with the Maxwell-Boltzmann distribution. Radiative losses due to free-free emission in a plasma evolving under collisional ionization equilibrium conditions and composed by H, He, C, N, O, Ne, Mg, Si, S, and Fe ions, are presented. These losses decrease with the decrease in the parameter n reaching a minimum when n = 1, and, thus converging to the losses of a thermal plasma. Tables of the thermal averaged and total Gaunt factors calculated for n distributions and a wide range electron and photon energies are presented.Comment: Accepted for publication in ApJS. 70 pages, 7 figures and 11 table

A zero-thickness mortar/ interface formulation with application to fracture mechanics

A zero-thickness mortar/interface element formulation is briefly described and demonstrated. This element may be considered as an extension of traditional zero-thickness interface element, in order to represent material interfaces located in between subdomains with non-matching FE meshes. In the context of small strain analysis, these elements may be equipped with the same type of constitutive laws as traditional interface elements. Therefore, if friction or fracture-mechanics-based laws are adopted, mortar/interface elements may be used to represent frictional sliding or cracking following the lines (surfaces) along which they have been pre-inserted. Two basic verification examples of this type are presented, showing that the model can correctly represent uniform states of stress and deformation when connecting unmatched mesh subdomains

The dynamics of inflation and currency substitution in a small open economy

In this paper, we analyse the relationship between money and inflation in a small open economy where domestic and foreign currencies are perfect substitutes as means of payment. It is shown that, if the path of domestic money supply is such that individuals find it optimal to change the currency in which transactions are settled, there will be an adjustment period during which domestic inflation adjusts so as to equalise the foreign inflation rate. In the case of a disinflation program, it is shown that the foreign currency is not necessarily abandoned as means of payment. The results obtained are consistent with both dollarisation hysteresis and reversibility, without requiring the specification of dollarisation costs.currency substitution, dollarisation, money-demand and hysteresis