APEX Millimeter Observations of Methanol Emission Toward High-Mass Star-Forming Cores

We present 247-GHz molecular line observations of methanol (CH$_3$OH) toward sixteen massive star-forming regions, using the APEX telescope with an angular resolution of $25''$. The sample covers a range of evolutionary states, including warm molecular cores, hot molecular cores, and ultracompact HII regions. The hot cores, all of which include UC HII regions, show rich molecular line spectra, although the strength of different species and transitions varies from source to source. In contrast, the warm cores do not show significant molecular line emission. Multiple methanol transitions are detected toward nine of the hot cores; eight of these had enough transitions to use the rotation diagram method to estimate rotational temperatures and column densities. The temperatures lie in the range 104$-$168 K and column densities from $3\times10^{16}$ to $7\times10^{18}$ cm$^{-2}$. Using the average methanol line parameters, we estimate virial masses, which fall in the range from 145 to 720 M$_\odot$ and proved to be significantly higher than the measured gas masses. We discuss possible scenarios to explain the chemical differences between hot cores and warm molecular cores. One of the observed methanol lines, $4_{2}-5_{1}A^{+}$ at 247.228 GHz, is predicted to show class II maser emission, similar in intensity to previously reported $J_0-J_{-1}E$ masers at 157 GHz. We did not find any clear evidence for maser emission among the observed sources; however, a weak maser in this line may exist in G345.01+1.79.Comment: Accepted for publication in The Astronomical Journa

Utilización del programa de CAD SolidWorks como herramienta para la explicación de contenidos y conceptos teóricos en ingeniería gráfica

En muchas ocasiones las explicaciones conceptuales relativas a la materia de Expresión Gráfica basadas en la comprensión del espacio, resultan difíciles de entender para el alumno, posiblemente debido a que aún no ha desarrollado suficientemente la capacidad para la interpretación del espacio, algo que si bien en parte es innato, también se ejercita y se aprende. Es por ello que los profesores que imparten dicha materia suelen apoyar sus explicaciones en representaciones gráficas del espacio más comprensibles como por ejemplo las perspectivas, también frecuentemente utilizadas en enunciados de exámenes o prácticas. Por otra parte, a día de hoy, disponemos de potentes herramientas de trabajo gráfico basados en el uso del ordenador como son los programes informáticos de CAD, entre ellos Solidworks, que incorporan espacios virtuales para el trabajo tridimensional y además tienen un funcionamiento basado en parámetros dimensionales y condiciones geométricas que se pueden interrelacionar. De la combinación de los conceptos expuestos surge la idea de utilizar los espacios virtuales tridimensionales y la capacidad paramétrica del programa Solidworks, como herramienta para generar módulos didácticos de apoyo para la explicación de contenidos fundamentados en la comprensión del espacio, con la intención de mejorar la eficacia en la comprensión de las explicacione

New determination of the NN-Δ(1232)\Delta(1232) axial form factors from weak pion production and coherent pion production off nuclei at T2K and MiniBooNE energies revisited

We re-evaluate our model predictions in Phys. Rev. D 79, 013002 (2009) for different observables in neutrino induced coherent pion production. This comes as a result of the new improved fit to old bubble chamber data of the dominant axial C_5^A nucleon-to-Delta form factor. We find an increase of 20%-30% in the values for the total cross sections. Uncertainties induced by the errors in the determination of C_5^A are computed. Our new results turn out to be compatible within about $1\sigma$ with the former ones. We also stress the existing tension between the recent experimental determination of the \sigma(CC coh \pi^+)}/\sigma(NC coh \pi^0)} $ ratio by the SciBooNE Collaboration and the theoretical predictions.Comment: 3 latex pages, 1 figure. Talk given at the NuFact10 Conferenc

Neutrino induced coherent pion production

We discuss different parameterizations of the $C_5^A(q^2)$ $N\Delta$ axial form factor, fitted to the old Argonne bubble chamber data for pion production by neutrinos, and we use coherent pion production to test their low $q^2$ behavior. We find moderate effects that will be difficult to observe with the accuracy of present experiments. We also discuss the use of the Rein-Sehgal model for low energy coherent pion production. By comparison to a microscopic calculation, we show the weaknesses of some of the approximations in that model that lead to very large cross sections as well as to the wrong shapes for differential ones. Finally we show that models based on the partial conservation of the axial current hypothesis are not fully reliable for differential cross sections that depend on the angle formed by the pion and the incident neutrino.Comment: Talk given at NUFACT09. 6 latex pages, 7 figures, 1 tabl

Life Cycle of a Concept in the Ad Hoc Cognition Framework

Recently, Casasanto and Lupyan (2015) have asserted that there are no context-independent concepts: all concepts are constructed ad hoc when they are instantiated. My aim is to show that the ad hoc cognition framework can be characterized by a similarity-based theory of concepts, and that two different notions of concept should be distinguished —which may be identified with two distinct stages of their life cycle (storage and instantiation). This approach brings together virtues from opposing views: (a) invariantist: stored concepts are stable enough to collect new information; (b) contextualist: instantiated concepts are context-dependent, what explains our adaptive ability to changing environments