Vertically extended and asymmetric CN emission in the Elias 2-27 protoplanetary disk

Elias 2-27 is a young star that hosts an extended, bright and inclined disk of dust and gas. The inclination and extreme flaring of the disk make Elias 2-27 an ideal target to study the vertical distribution of molecules, particularly CN. We directly trace the emission of CN in Elias 2-27 and compare it to previously published CO isotopologue data. CN $N = 3-2$ emission is analyzed in two different transitions $J = 7/2 - 5/2$ and $J = 5/2 - 3/2$, for which we detect two hyperfine group transitions. The vertical location of CN emission is traced directly from the channel maps, following geometrical methods that have been previously used to analyze the CO emission of Elias 2-27. Analytical models are used to parametrize the vertical profile of each molecule and study the extent of each tracer, additionally we compute radial profiles of column density and optical depth. We show that the vertical location of CN and CO isotopologues in Elias 2-27 is layered and consistent with predictions from thermochemical models. A north/south asymmetry in the radial extent of CN is detected and we find that the CN emission is mostly optically thin and constrained vertically to a thin slab at $z/r \sim$0.5. A column density of 10$^{14}$\,cm$^{-2}$ is measured in the inner disk which for the north side decreases to 10$^{12}$\,cm$^{-2}$ and for the south side to 10$^{13}$\,cm$^{-2}$ in the outer regions. In Elias 2-27, CN traces a vertically elevated region above the midplane, very similar to that traced by $^{12}$CO. The inferred CN properties are consistent with thermo-chemical disk models, in which CN formation is initiated by the reaction of N with UV-pumped H$_2$. The observed north/south asymmetry may be caused by either ongoing infall or by a warped inner disk. This study highlights the importance of tracing the vertical location of various molecules to constrain the disk physical conditions.Comment: Accepted for publication in A&A, 19 pages, 14 figure

Using Process Mining to Analyze Time-Distribution of Self-Assessment and Formative Assessment Exercises on an Online Learning Tool

The study of the relationships between self-regulated learning and formative assessment is an active line of research in the educational community. A recent review of the literature highlights that the study of these connections has been mainly unidirectional, focusing on how formative assessment helps students to self-regulate their learning, being much less explored the effect of self-regulated learning strategies on formative assessment. In this context, analyzing automatically captured students’ activities within online learning tools can provide us further insights on the interactions between these two topics. More specifically, this article examines the activity traces of 382 students who used an online tool to learn a programming language. The tool incorporates review exercises for promoting self-assessment (an important self-regulated learning strategy). Furthermore, the tool is used in supervised laboratories where students receive formative assessment. This study uses process mining techniques to analyze the temporal component of student behavior in both types of activities, their interaction, and how self-assessment relates to formative assessment. Some key lessons are learned: activities promoting self-assessment significantly improved students’ involvement in formative assessment activities; increasing selfassessment cannot compensate for a lack of effort in formative assessment. We also underline that, to the best of our knowledge, to date no research has used process mining to consider the time component in the analysis of the relationships between formative assessment and self-assessment

Raman microprobe characterization of electrodeposited S-rich CuIn(S,Se)2 for photovoltaic applications: Microstructural analysis

This article reports a detailed Raman scattering and microstructural characterization of S-rich CuIn(S,Se)2 absorbers produced by electrodeposition of nanocrystalline CuInSe2 precursors and subsequent reactive annealing under sulfurizing conditions. Surface and in-depth resolved Raman microprobe measurements have been correlated with the analysis of the layers by optical and scanning electron microscopy, x-ray diffraction, and in-depth Auger electron spectroscopy. This has allowed corroboration of the high crystalline quality of the sulfurized layers. The sulfurizing conditions used also lead to the formation of a relatively thick MoS2 intermediate layer between the absorber and the Mo back contact. The analysis of the absorbers has also allowed identification of the presence of In-rich secondary phases, which are likely related to the coexistence in the electrodeposited precursors of ordered vacancy compound domains with the main chalcopyrite phase, in spite of the Cu-rich conditions used in the growth. This points out the higher complexity of the electrodeposition and sulfurization processes in relation to those based in vacuum deposition techniques

Los materiales en el diseño español

El presente trabajo muestra los resultados de un proyecto llevado a cabo este curso 2011/2012 en el primer curso del grado en Ingeniería en Diseño Industrial y Desarrollo de Producto de la Universitat Jaume I de Castelló. Se trata de un proyecto coordinado entre las asignaturas Materiales I y Expresión Artística I en el que se ha planteado un estudio por grupos de los materiales empleados por diseñadores españoles de reconocido prestigio en un diseño de su elección. Finalmente se les ha pedido a cada grupo que realice un Google Site con el producto seleccionado donde se recoja la información del producto, el tipo de material empleado para cada parte y el efecto que esta selección ha tenido en la novedad del diseño. Así pues, este proyecto ha perseguido un triple objetivo: a) Concienciar al alumnado de primer curso de la interdisciplinaridad de su perfil mediante la coordinación en una actividad de dos de las asignaturas que, aparentemente, son más distantes en su currículum y contenido. b) Concienciar al alumno de la importancia de la ciencia de los materiales en su formación como Ingenieros de Diseño y Productos, cosa de la que la mayoría de los alumnos no son conscientes hasta que se encuentran frente a un proyecto real de diseño de producto. c) Familiarizar a los alumnos con los materiales más comunes en el mundo del diseño de producto, así como con las oportunidades que estos materiales ofrecen desde un punto no solo técnico, sino estético, e incluso artístico.Peer Reviewe

La metodología de aprendizaje basado en proyectos (ABP) aplicada a asignaturas de ciencia de los materiales en ingeniería en la red IdM@ti

En este trabajo se va a presentar una experiencia docente llevada a cabo de forma coordinada entre profesorado de la red de innovación docente en ciencia de materiales IdM@ti. Se trata por tanto de una experiencia interuniversitaria que se ha desarrollado entre cuatro universidades públicas españolas de manera simultánea. Concretamente, el presente trabajo muestra la implementación y el desarrollo de la aplicación de la metodología de aprendizaje basado en proyectos en asignaturas de grados de ingeniería en el ámbito de ciencia de los materiales e ingeniería metalúrgica. Se presentan las experiencias llevadas a cabo durante los últimos cuatro años, mostrando los puntos fuertes y débiles de esta metodología, así como la problemática asociada a la implementación de la misma en asignaturas de curso general de grado. Se presentarán también los resultados obtenidos, así como las principales conclusiones a las que ha llegado el equipo de trabajo de la red IdM@ti

Task Failure during Exercise to Exhaustion in Normoxia and Hypoxia Is Due to Reduced Muscle Activation Caused by Central Mechanisms While Muscle Metaboreflex Does Not Limit Performance

To determine whether task failure during incremental exercise to exhaustion (IE) is principally due to reduced neural drive and increased metaboreflex activation eleven men (22±2 years) performed a 10s control isokinetic sprint (IS; 80 rpm) after a short warm-up. This was immediately followed by an IE in normoxia (Nx, PIO2:143 mmHg) and hypoxia (Hyp, PIO2:73 mmHg) in random order, separated by a 120 min resting period. At exhaustion, the circulation of both legs was occluded instantaneously (300 mmHg) during 10 or 60s to impede recovery and increase metaboreflex activation. This was immediately followed by an IS with open circulation. Electromyographic recordings were obtained from the vastus medialis and lateralis. Muscle biopsies and blood gases were obtained in separate experiments. During the last 10s of the IE, pulmonary ventilation, VO2, power output and muscle activation were lower in hypoxia than in normoxia, while pedaling rate was similar. Compared to the control sprint, performance (IS-Wpeak) was reduced to a greater extent after the IE-Nx (11% lower P<0.05) than IE-Hyp. The root mean square (EMGRMS) was reduced by 38 and 27% during IS performed after IE-Nx and IE-Hyp, respectively (Nx vs. Hyp: P<0.05). Post-ischemia IS-EMGRMS values were higher than during the last 10s of IE. Sprint exercise mean (IS-MPF) and median (IS-MdPF) power frequencies, and burst duration, were more reduced after IE-Nx than IE-Hyp (P<0.05). Despite increased muscle lactate accumulation, acidification, and metaboreflex activation from 10 to 60s of ischemia, IS-Wmean (+23%) and burst duration (+10%) increased, while IS-EMGRMS decreased (-24%, P<0.05), with IS-MPF and IS-MdPF remaining unchanged. In conclusion, close to task failure, muscle activation is lower in hypoxia than in normoxia. Task failure is predominantly caused by central mechanisms, which recover to great extent within one minute even when the legs remain ischemic. There is dissociation between the recovery of EMGRMS and performance. The reduction of surface electromyogram MPF, MdPF and burst duration due to fatigue is associated but not caused by muscle acidification and lactate accumulation. Despite metaboreflex stimulation, muscle activation and power output recovers partly in ischemia indicating metaboreflex activation has a minor impact on sprint performance

Structural and vibrational properties of α- and π-SnS polymorphs for photovoltaic applications

Tin sulphide (SnS) has attracted the attention of the photovoltaic (PV) community due to the combination of desirable optical properties, and its binary and earth abundant elemental composition, which should lead to relatively simple synthesis. However, currently the best SnS based PV device efficiency remains at 4.36%. Limited performance of this material is attributed to band gap alignment issues, deviations in doping concentration and poor film morphology. In this context Raman spectroscopy (RS) analysis can be useful as it facilitates the accurate evaluation of material properties. In this study we present a RS study, supported by X-ray diffraction and wavelength dispersive X-ray measurements, of α- and π-SnS thin films. In particular a complete description of SnS vibrational properties is made using six excitation wavelengths, including excitation energies coupled with certain optical band to band transitions, which leads to close to resonance measurement conditions. This study describes an in-depth analysis of the Raman spectra of both SnS structural polymorphs, including the differences in the number of observed peaks, with their relative intensities and Raman shift. Additionally, we evaluate the impact of low temperature heat treatment on SnS. These results explicitly present how the variation of the [S]/[Sn] ratio in samples deposited by different methods can lead to significant and correlated shifts in the relative positions of Raman peaks, which is only observed in the α-SnS phase. Furthermore, we discuss the suitability of using Raman spectroscopy based methodologies to extract fine stoichiometric variations in different α-SnS samples.</p

Scanning microelectrochemical characterization of the effect of polarization on the localized corrosion of 304 stainless steel in chloride solution

Corrosion processes occurring on stainless steel 304 surfaces under anodic polarization have been characterized using scanning electrochemical microscopy (SECM) and the scanning vibrating electrode technique (SVET), complemented with conventional potentiodynamic polarization curves. Stable pit formation has been detected by SVET on the samples as result of surface modification under electrochemical control, which may include the previous electrochemical reduction of passive oxide layer if the media is not aggressive enough to induce pitting at small overpotentials. Additionally, the sample generation – tip collection operation mode of the SECM has enabled the detection of local release of iron (II) ions, as well as their conversion to iron (III), both processes being greatly affected by the potential applied to the substrat

Imaging local surface reactivity on stainless steels 304 and 316 in acid chloride solution using scanning electrochemical microscopy and the scanning vibrating electrode technique

Passive film breakdown and pit nucleation on 304 and 316 stainless steels in chloride-containing media were investigated using scanning microelectrochemical microscopy (SECM) and the scanning vibrating electrode technique (SVET). Experiments were performed for the alloys either at their corresponding open circuit potential, or under applied polarization, as to image domains of similar topography but different resistance against breakdown of the passive layers formed on these steels. Identification of the iron released species was accomplished, showing that pitting occurs with the formation of iron (II) species only. Detection of iron (III) species occurred when the steel sample was polarized at high positive overpotentials because it served as the reaction site to oxidize the iron (II) ions released from a propagating pit. The obtained results have revealed some difference of the reactivity of both specimens. Moreover the effect of the galvanic coupling has been investigate