Testing the Production of Scintillation Arcs with the Pulsar B1133+16

Pulsars are extremely dense, highly magnetized stars that emit pulses of radio emission every millisecond or so. The arrival times of their radio signals at Earth observatories can be used as a clock precise enough to detect gravitational waves. Performing such a detection requires the mitigation of interference effects from the interstellar medium: the slightly ionized, mostly hydrogen gas that the radio waves traverse as they travel from the pulsar to Earth. We investigate radio wave delays using a powerful tool: scintillation arcs, fluctuations in frequency and time of the pulsar signal intensity that are manifested as parabolic arcs in the pulsar’s secondary spectrum. While scintillation arcs were first observed by Oberlin students almost two decades ago, the structures that cause them are still unknown. We explore the unique capabilities of the pulsar B1133+16 for testing models of scintillation arcs. Using measurements of scintillation arc curvatures over 96 days, we test a model for the annual modulation of arc curvature due to Earth’s orbit. The formalism for determining the width of a pulsar image from a scintillation arc width is used to design an empirical test of scintillation arc models based on the frequency dependence of arc widths. This formalism is then explored in the framework of a simple, one-dimensional model for the production of scintillation arcs

Macroinvertebrates as Indicators of Water Quality in Blacktail Creek

Blacktail Creek, located in Butte, Montana, has a long history of human-caused contamination. Mine waste has polluted parts of its streambed since the late 1800’s, causing extensive loss of vegetative diversity along the creek, as well as a loss of aquatic life. The Blacktail Berm is an area currently estimated to contain 35,000 cubic yards of toxic mine tailings. The future removal of remaining mine tailings in Butte is not a certainty at this point, but planning removal and restoration of these contaminated areas has been discussed extensively in recent years. In order to help provide baseline data prior to future restoration efforts, this study was conducted to survey the aquatic macroinvertebrate populations in Blacktail Creek. Macroinvertebrates are often used as part of an assessment of stream health, particularly in relation to restoration work. The presence and abundance of specific aquatic macroinvertebrates can be used to get an idea of the water quality of the stream. Macroinvertebrate samples were collected at five locations along Blacktail Creek from September 13, 2016 through September 17, 2016. Along with stream conductivity, temperature, and dissolved oxygen, an Ephemeroptera, Plecoptera, and Trichoptera (EPT) index assessment was completed. The EPT index used for this assessment provided good, fair, or poor water quality ratings for Blacktail Creek based on the ratio of EPT macroinvertebrates to total macroinvertebrates in a single sample. The results will provide data useful in long-term monitoring of these macroinvertebrate populations before, during, and after the cleanup of Blacktail Creek

Nuevos avances sobre estudios moleculares en el Género heleobia (Caenogastropoda:Rissoidea, Cochliopidae) de los Andes Centrales y Patagónicos

Estudios previos sobre caracterización molecular y revisión del estatus taxonómico de especies del género Heleobia de los Andes Centrales y Patagonia mediante Citocromo Oxidasa 1 (COI) confirmaron la sinonimia entre H. parchappii (d’Orbigny, 1835) y H. occidentalis (Doering, 1885), e identificaron a H. kuesteri (Strobel, 1874) como especie válida y diferente a H. parchappii. Las secuencias obtenidas para el gen COI de H. hatcheri y del morfotipo Heleobia sp estuvieron significativamente separadas de las demás Heleobias, sugiriendo que no pertenecerían a este género, sino a otros no incluidos en Cochliopidae. El objetivo fue contrastar estos resultados con otros marcadores mitocondriales.Trabajo presentado en el II Congreso Argentino de Malacología (2CAM), realizado entre el 10 y el 12 de agosto de 2016 en Mendoza (Argentina)

Una contribución molecular al controvertido estatus taxonómico de un grupo de caracoles dulceacuícolas (Caenogastropoda: Rissooidea, Cochliopidae) distribuídos desde el desierto de los Andes centrales hasta la Patagonia

For over 40 years malacologists have been discussing the taxonomical status of Heleobia species, an enigmatie genus from Cochliopidae family (Caenogastropoda: Rissooidea). As with other rissooidean families, the considerable character convergence and the paucity of anatomical synapomorphies has proved to be a problem in resolving cochliopid phylogenetic relations and establishing the validity of several nominal cochliopid species. Here we present a molecular contribution to solve the taxonomical status of one of the most abundant Southern South América cochliopid genera which has many endemic species. We report molecular evidence that supports three of the four Heleobia groups described for this región, the “australis”, “parchappii” and “piscium” groups. The fourth, the “hatcheri” group, belongs not to Heleobia but to a different genus which itself should not be considered as part of the family Cochliopidae but closely related to genus Potamolithus Pilsbry & Rush, 1896.Durante más de 40 años se ha discutido el estatus taxonómico de diversas especies del enigmático género Heleobia de la Familia Cochliopidae (Caenogastropoda: Rissooidea). Como sucede con otras familias de rissooideos, la abundancia de caracteres convergentes y la escasez de sinapomorfías anatómicas han representado un problema para resolver las relaciones filogenéticas de Cochliopidae y definir la validez de varias de las especies nominales de esta Familia. Presentamos aquí una contribución molecular tendiente a resolver el estatus taxonómico de uno de los más abundantes géneros de la porción meridional de Sudamérica que incluye varias especies endémicas. Nuestra evidencia molecular reconfirma tres de los cuatro grupos de Heleobia en los que se han agrupado las especies del género en esta región: “australis”, “parchappii” y “piscium”. El cuarto, el grupo “hatcheri ”, no pertenece a Heleobia sino a un género diferente que no debería ser considerado como integrante de la Familia Cochliopidae, sino estrechamente relacionado al género Potamolithus Pilsbry y Rush, 1896.Facultad de Ciencias Naturales y Muse

Offshoring and firm overlap

We set up a model of offshoring with heterogeneous producers that captures two empirical regularities of German offshoring firms. There is selection of larger, more productive firms into offshoring. However, the selection is not sharp, and offshoring and non-offshoring firms coexist over a wide range of the revenue distribution. An overlap of offshoring and nonoffshoring firms emerges in our model because, in contrast to textbook models of trade with heterogeneous producers, we allow firms to differ in two technology parameters thereby decoupling the offshoring status of a firm from its revenues. In an empirical analysis, we employ firm-level data from Germany to estimate key parameters of the model and show that ignoring the overlap lowers the estimated gains from offshoring by more than 50 percent and, at the same time, exaggerates substantially the importance of the extensive margin for explaining the evolution of German offshoring over the last 25 yearsWir haben ein Offshoring-Modell mit heterogenen Produzenten aufgestellt, welches sich mit zwei empirischen Gesetzmäßigkeiten deutscher Offshoring-Firmen befasst. Es besteht eine Selektion von größeren, produktiveren Firmen zur Standortverlagerung in das Ausland. Diese Selektion ist jedoch nicht deutlich ausgeprägt und Offshoring- und Nichtoffshoring Firmen sind gemeinsam über weite Teile der Umsatzverteilung zu beobachten. Die Überlappung entsteht, da, im Gegensatz zu Lehrbuchmodellen mit Handel und heterogenen Produzenten, unser Modell es Firmen gestattet sich in zwei Technologiekenngrößen zu unterscheiden, wodurch die Entkopplung des Offshoringzustands einer Firma von deren Umsatz erreicht wird. In einer empirischen Betrachtung verwenden wir deutsche Daten auf Betriebsebene, um die Schlüsselparameter des Modells zu schätzen und zu zeigen, dass die Nichtbeachtung der Überlappung die geschätzten Gewinne durch Offshoring um mehr als 50 Prozent reduziert. Außerdem wird dadurch wesentlich die Bedeutung der externen Anpassung für die Erklärung der Entwicklung des deutschen Offshorings über die vergangenen 25 Jahre überschätzt

Offshoring and Firm Overlap

We set up a model of offshoring with heterogeneous producers that captures two empirical regularities of German offshoring firms. There is selection of larger, more productive firms into offshoring. However, the selection is not sharp, and offshoring and non-offshoring firms coexist over a wide range of the revenue distribution. An overlap of offshoring and non-offshoring firms emerges in our model because, in contrast to textbook models of trade with heterogeneous producers, we allow firms to differ in two technology parameters thereby decoupling the offshoring status of a firm from its revenues. In an empirical analysis, we employ firm-level data from Germany to estimate key parameters of the model and show that ignoring the overlap lowers the estimated gains from offshoring by more than 50 percent and, at the same time, exaggerates substantially the importance of the extensive margin for explaining the evolution of German offshoring over the last 25 years

Offshoring and Firm Overlap

We set up a model of offshoring with heterogeneous producers that captures two empirical regularities on offshoring firms: larger, more productive firms are more likely to make use of the offshoring opportunity; the fraction of firms that engages in offshoring is positive and smaller than one in any size or revenue category. These patterns generate an overlap of offshoring and non-offshoring firms, which is non-monotonic in the costs of offshoring. In an empirical exercise, we employ firm-level data from Germany to estimate key parameters of the model. We show that ignoring the overlap leads to a severe downward bias in the estimated gains from offshoring, which amounts to almost 60 percent in our model