Destruction of dimethyl ether and methyl formate by collisions with He+^+

To correctly model the abundances of interstellar complex organic molecules (iCOMS) in different environments, both formation and destruction routes should be appropriately accounted for. While several scenarios have been explored for the formation of iCOMs via grain and gas-phase processes, much less work has been devoted to understanding the relevant destruction pathways, with special reference to (dissociative) charge exchange or proton transfer reactions with abundant atomic and molecular ions such as He$^+$, H$_3^+$ and HCO$^+$. By using a combined experimental and theoretical methodology we provide new values for the rate coefficients and branching ratios (BRs) of the reactions of He$^+$ ions with two important iCOMs, namely dimethyl ether (DME) and methyl formate (MF). We also review the destruction routes of DME and MF by other two abundant ions, namely H$_3^+$ and HCO$^+$. Based on our recent laboratory measurements of cross sections and BRs for the DME/MF + He$^+$ reactions over a wide collision energy range, we extend our theoretical insights on the selectivity of the microscopic dynamics to calculate the rate coefficients $k(T)$ in the temperature range from 10 to 298 K. We implement these new and revised kinetic data in a general model of cold and warm gas, simulating environments where DME and MF have been detected. Due to stereodynamical effects present at low collision energies, the rate coefficients, BRs and temperature dependences here proposed differ substantially from those reported in KIDA and UDfA, two of the most widely used astrochemical databases. These revised rates impact the predicted abundances of DME and MF, with variations up to 40% in cold gases and physical conditions similar to those present in prestellar coresComment: accepted for publication in Astronomy and Astrophysics (manuscript no. AA/2018/34585), 10 pages, 3 figure

E-learning: nuevas estrategias y tendencias

The aim of this paper is to present a personal point of view on the possible future trends in distance learning. The starting point of this study is represented by a review of the main innovations in digital and information technologies. This step is necessary since the evolution of distance learning is strictly correlated to the evolution of the technology that can be exploited to increase learning quality. The main arguments discussed in this paper are: massive open on-line courses (MOOCs), flipped classrooms and the evolution of the learning objects based on web and on internet technology. Concerning MOOCs, a critical analysis of the status of this type of learning is necessary to understand their possible evolution and/or their substitution. A huge number of case studies demonstrated the validity of the flipped classroom and the possibility to adopt this approach into e-learning is surely interesting. The last part of the paper is instead dedicated to future technologies like: mobile learning, 3D virtual laboratories and internet of things. As discussed, this latest innovations can push the evolution of distance learning offering real student-centered solutions.El objetivo de este trabajo es presen­tar un punto de vista personal sobre las posibles futuras tendencias en la ense­ñanza a distancia. El punto de partida de este estudio está representado por una revisión de las principales innovaciones en las tecnologías digitales y de infor­mación. Este paso es necesario, ya que la evolución de la enseñanza a distancia está estrictamente correlacionada con la evolución de la tecnología que puede ser explotada para aumentar la calidad de aprendizaje. Los principales argumentos abordados en este documento son massive open on-line courses (MOOC), flipped class­rooms y la evolución de los objetos de aprendizaje basados en la web y en la tecnología de internet. En cuanto a los MOOC, realizar un análisis crítico de la situación de este tipo de aprendizaje es necesario para entender su posible evolución y/o su sustitución. Un gran número de estudios de caso demostra­ron la validez del flipped classroom, y la posibilidad de adoptar este enfoque en el aprendizaje electrónico es sin duda interesante. La última parte del artículo se dedica a las futuras tecnologías, tales como el aprendizaje móvil, los laborato­rios virtuales en 3D y el internet de las cosas. Como se ha expuesto, estas últi­mas innovaciones pueden impulsar la evolución de la educación a distancia, que ofrece soluciones reales centradas en el estudiante

Density measurement of OH radicals in non-thermal plasmas by laser induced fluorescence and time-resolved absorption spectroscopy

In the present thesis work, we have developed two different experimental setups for the optical detection of the OH radical in discharges at atmospheric pressure. The first one allows us to improve the time-resolved broad-band absorption spectroscopy. The main advances of the new set up are a better collimation of the UV light and a novel gating scheme. They both significantly reduce the interference of the plasma-induced emission on the absorption measurement. The second setup is dedicated to an improved laser induced fluorescence experiment, which takes advantage of a novel multi-transition excitation scheme. This permits the simultaneous measurements of both the OH density and its ground state rotational temperature. In addition, we have developed a new rate-equation model to rationalize LIF spectra, by taking into account the electronic quenching, the vibrational and rotational energy transfers, and the spatial profile of the laser beam. Finally, the electrical power dissipated in the discharge was accurately measured

What Color is My Arm? Changes in Skin Color of an Embodied Virtual Arm Modulates Pain Threshold

It has been demonstrated that visual inputs can modulate pain. However, the influence of skin color on pain perception is unknown. Red skin is associated to inflamed, hot and more sensitive skin, while blue is associated to cyanotic, cold skin. We aimed to test whether the color of the skin would alter the heat pain threshold. To this end, we used an immersive virtual environment where we induced embodiment of a virtual arm that was co-located with the real one and seen from a first-person perspective. Virtual reality allowed us to dynamically modify the color of the skin of the virtual arm. In order to test pain threshold, increasing ramps of heat stimulation applied on the participants' arm were delivered concomitantly with the gradual intensification of different colors on the embodied avatar's arm. We found that a reddened arm significantly decreased the pain threshold compared with normal and bluish skin. This effect was specific when red was seen on the arm, while seeing red in a spot outside the arm did not decrease pain threshold. These results demonstrate an influence of skin color on pain perception. This top-down modulation of pain through visual input suggests a potential use of embodied virtual bodies for pain therapy

Riesz transform for a flow Laplacian on homogeneous trees

We obtain weak type $(1,1)$ and $L^p$ boundedness, for $p \in (1,\infty)$, of the first order Riesz transform and its adjoint operator on a homogeneous tree endowed with the canonical flow measure. This is a model case of measure metric space which is nondoubling, of exponential growth, does not satisfy the Cheeger isoperimetric inequality, and where the Laplacian does not have spectral gap. This complements a previous work by W. Hebisch and T. Steger.Comment: The proof of Theorem 1.1 builds upon Theorem 4.1 and Theorem 4.2, whose proofs are not correct. We remark that the heat kernel estimates of section 3, as well as Theorem 4.4, are correct and may have an independent interes

Cognitive Neuroscience of Pain

Non peer reviewe