Forbidden Line Emission in the Eccentric Spectroscopic Binaries DQ Tauri and UZ Tauri E Monitored over an Orbital Period

We present echelle spectroscopy of the close pre-main-sequence binary star systems DQ Tau and UZ Tau-E. Over a 16 day time interval we acquired 14 nights of spectra for DQ Tau and 12 nights of spectra for UZ Tau-E. This represents the entire phase of DQ Tau, and 63 percent of the phase of UZ Tau-E. As expected, photospheric lines such as Li I 6707 clearly split into two components as the primary and secondary orbit one another, as did the permitted line He I 5876. Unlike the photospheric features, the forbidden lines of [O I] 6300 and [O I] 5577, retain the same shape throughout the orbit. Therefore these lines must originate outside of the immediate vicinity of the two stars and any circumstellar disks that participate in the orbital motion of the stars.Comment: 14 pages including 6 figures, aastex preprint, accepted to Astronomical Journa

La resolución de problemas de probabilidad con intención didáctica en la formación de maestros y profesores de matemáticas

En este trabajo se reflexiona sobre la resolución de problemas de probabilidad en la formación de maestros y profesores. Se introduce la idea de la resolución de problemas con intención didáctica y se analiza una manera de resolver problemas de probabilidad, que llamamos “por simulación”. Esta manera se introduce como un método de resolución de problemas de probabilidad con potencial heurístico; su conocimiento se revela necesario en la formación de los maestros y profesores de matemáticas como gestores del proceso de resolución de problemas de probabilidad por estudiantes de primaria y secundaria

Control of Violence, Control of Fear: The Progression of Gun Control in San Francisco, 1847-1923

This paper focuses on gun control in San Francisco between 1847 and 1923, from the control of the rowdy men of the gold rush, to the management of the Chinese, to the control of the sale and distribution of firearms. For the purpose of this study, the main sources used to understand public perceptions are newspapers, specifically the Daily Alta California, San Francisco Call, and San Francisco Chronicle. While it is impossible to completely recreate the attitudes towards guns, newspapers provide a window into public opinion, while also providing multiple opinions on the same or similar subjects. In addition, government records provide specific information on municipal and state gun laws passed in the wake of the published opinions. From the first ban on discharging weapons in San Francisco to the first concealed weapons ban, San Franciscans examined their relationship with firearms in the rapidly growing city. As the Chinese population increased, the gun control discourse shifted to include the perceived threat of the Chinese “highbinder,” generated by local newspapers. The conversation was further altered in the early twentieth century as white San Franciscans began criticizing the relationship between society and firearms, and lobbied for statewide gun control

Transit Funding; Why the Politics? A Comparative Study of Public Transportation Infrastructure Funding in New York City and Los Angeles

Suburban sprawl and automobile dependence has undermined support and funding for mass transit in Los Angeles and New York, and has instead dedicated funding from gas tax revenues to highways. Infrastructure coalition building in Los Angeles is turning public need and support into dollars. The challenge is what can New York City learn from the soon to be ex-autopolis and what can Los Angeles learn from the funding transit legacy of New York. This thesis asks the questions of why there is more transit momentum in Los Angeles than in New York City, and what is making it easier to fund projects in a relatively conservative political environment. Points of similarity and divergence in transit funding in New York City and Los Angeles are be identified through critical review of the funding strategies of the two systems. Interestingly, though these two cities have historically pursued transit in inversely opposite manners; the newfound transit religion in Los Angeles is currently juxtaposed with what seems to be stagnate growth in New York. The impetus and values driving the grassroots coalition in Los Angeles are strengthening political support and helping secure financing for transit projects, and points to the importance of champions in securing funding for transit

Origin of coherent structures in a discrete chaotic medium

Using as an example a large lattice of locally interacting Hindmarsh-Rose chaotic neurons, we disclose the origin of ordered structures in a discrete nonequilibrium medium with fast and slow chaotic oscillations. The origin of the ordering mechanism is related to the appearance of a periodic average dynamics in the group of chaotic neurons whose individual slow activity is significantly synchronized by the group mean field. Introducing the concept of a "coarse grain" as a cluster of neuron elements with periodic averaged behavior allows consideration of the dynamics of a medium composed of these clusters. A study of this medium reveals spatially ordered patterns in the periodic and slow dynamics of the coarse grains that are controlled by the average intensity of the fast chaotic pulsation

El equilibrio químico, una investigación de aula

Se presenta una metodología didáctica para promover el aprendizaje del equilibrio químico. El punto de inicio es la identificación y construcción de las características del concepto, con base en el uso de analogías, resolución de problemas y trabajos prácticos y se sugiere no introducir el Principio de LeChatelier antes de trabajar suficientemente los conceptos de equilibrio dinámico e irreversibilidad de reacciones. La propuesta se probó con alumnos del último año del bachillerato de la UNAM (18 años) y, se usó el modelo de investigación el diseño experimental de grupo control preprueba-tratamiento-posprueba. Los resultados de la inferencia estadística indican una mejoría en el manejo del concepto por parte de los alumnos que trabajaron el tema con esta secuencia de aprendizaje

A Young Planet Search in Visible and IR Light: DN Tau, V836 Tau, and V827 Tau

In searches for low-mass companions to late-type stars, correlation between radial velocity variations and line bisector slope changes indicates contamination by large starspots. Two young stars demonstrate that this test is not sufficient to rule out starspots as a cause of radial velocity variations. As part of our survey for substellar companions to T Tauri stars, we identified the ~2 Myr old planet host candidates DN Tau and V836 Tau. In both cases, visible light radial velocity modulation appears periodic and is uncorrelated with line bisector span variations, suggesting close companions of several M_Jup in these systems. However, high-resolution, infrared spectroscopy shows that starspots cause the radial velocity variations. We also report unambiguous results for V827 Tau, identified as a spotted star on the basis of both visible light and infrared spectroscopy. Our results suggest that infrared follow up observations are critical for determining the source of radial velocity modulation in young, spotted stars.Comment: Accepted for publication in the Astrophysical Journal Letter