Raising awareness of the accessibility challenges in mathematics MOOCs

MOOCs provide learning environments that make it easier for learners to study from anywhere, at their own pace and with open access to content. This has revolutionised the field of eLearning, but accessibility continues to be a problem, even more so if we include the complexity of the STEM disciplines which have their own specific characteristics. This work presents an analysis of the accessibility of several MOOC platforms which provide courses in mathematics. We attempt to visualise the main web accessibility problems and challenges that disabled learners could face in taking these types of courses, both in general and specifically in the context of the subject of mathematics

Circuital model for the spherical geodesic waveguide perfect drain

The perfect drain for the Maxwell fish eye (MFE) is a non-magnetic dissipative region placed in the focal point to absorb all the incident radiation without reflection or scattering

Performance analysis of AlGaAs/GaAs tunnel junctions for ultra-high concentration photovoltaics

An n(++)-GaAs/p(++)-AlGaAs tunnel junction with a peak current density of 10 100Acm(-2) is developed. This device is a tunnel junction for multijunction solar cells, grown lattice-matched on standard GaAs or Ge substrates, with the highest peak current density ever reported. The voltage drop for a current density equivalent to the operation of the multijunction solar cell up to 10 000 suns is below 5 mV. Trap-assisted tunnelling is proposed to be behind this performance, which cannot be justified by simple band-to-band tunnelling. The metal-organic vapour-phase epitaxy growth conditions, which are in the limits of the transport-limited regime, and the heavy tellurium doping levels are the proposed origins of the defects enabling trap-assisted tunnelling. The hypothesis of trap-assisted tunnelling is supported by the observed annealing behaviour of the tunnel junctions, which cannot be explained in terms of dopant diffusion or passivation. For the integration of these tunnel junctions into a triple-junction solar cell, AlGaAs barrier layers are introduced to suppress the formation of parasitic junctions, but this is found to significantly degrade the performance of the tunnel junctions. However, the annealed tunnel junctions with barrier layers still exhibit a peak current density higher than 2500Acm(-2) and a voltage drop at 10 000 suns of around 20 mV, which are excellent properties for tunnel junctions and mean they can serve as low-loss interconnections in multijunction solar cells working at ultra-high concentrations

Differences in cognitive, motivational and contextual variables among under-achieving, normally-achieving, and over-achieving students:a mixed-effects analysis

There are few studies in Spain which analyze the influence of individual, motivational and contextual variables, which might be different between underachieving, normally achieving and overachieving students. Method: A total of 1,398 Spanish high school students participated. Mixed-effects models were used to analyze data. Results: The results showed some evidence of: (a) Partial mediational effect of self-concept on the association between cognitive ability and academic achievement. (b) Higher levels of learning goals in the overachieving group than in the underachieving group, but no differences in achievement and reinforcement goals between groups. (c) Positive effect of learning strategies on attainment, both in the underachieving and the non-underachieving students. (d) Little effect of context variables on academic achievement, both in the underachieving and non-underachieving students. Conclusions: Underachieving students seem to employ all the learning strategies considered to a lesser extent than normally and overachieving students. They also have a lower level of learning goals. On the contrary, overachieving students score more highly than under and normally achieving students in almost all of the above factors.Antecedentes: apenas existen estudios en España que analicen la influencia de variables cognitivas, motivacionales y contextuales capaces de establecer diferencias entre los estudiantes con rendimiento menor, igual y mayor al esperado. Método: participaron 1.398 estudiantes españoles de Educación Secundaria Obligatoria. Se emplearon modelos de efectos mixtos para el análisis de datos. Resultados: los resultados mostraron evidencia de: (a) efecto mediacional parcial del auto-concepto en la asociación de la habilidad cognitiva y el rendimiento académico; (b) mayores niveles de metas de aprendizaje en el grupo de estudiantes con rendimiento mayor al esperado; (c) efecto positivo de las estrategias de aprendizaje sobre el rendimiento en todos los grupos; (d) efecto pequeño de las variables contextuales sobre el rendimiento en todos los grupos. Conclusiones: los estudiantes con rendimiento menor al esperado emplean en menor medida las estrategias de aprendizaje y las metas orientadas al aprendizaje. Por el contrario, los estudiantes con rendimiento mayor al esperado muestran niveles superiores que el resto de grupos en la mayor parte de variables.The present work was supported by the Spanish Ministry of Economy and Competitiveness (Award number: EDU2012-32156) and the Vice Chancellor for Research of the University of Alicante (Award number: GRE11-15). This work has also been developed thanks to an academic stay of the corresponding author at the University of Bristol (Reference of the grant: EEBB-I-15_09943)

Alibava : A portable readout system for silicon microstrip sensors

A portable readout system for silicon microstrip sensors is currently being developed. This system uses a front-end readout chip, which was developed for the LHC experiments. The system will be used to investigate the main properties of this type of sensors and their future applications. The system is divided in two parts: a daughter board and a mother board. The first one is a small board which contains two readout chips and has fan-ins and sensor support to interface the sensors. The last one is intended to process the analogue data that comes from the readout chips and from external trigger signals, to control the whole system and to communicate with a PC via USB. The core of this board is a FPGA that controls the readout chips, a 10 bit ADC, an integrated TDC and an USB controller. This board also contains the analogue electronics to process the data that comes from the readout chips. There is also provision for an external trigger input (e.g. scintillator trigger) and a 'synchronised' trigger output for pulsing an external excitation source (e.g. laser system)

Rinosinusitis fúngica en adulto mayor inmunocompetente

Objetivo: La rinosinusitis fúngica (FRS) es una enfermedad causada mayormente por el Aspergillus sp., el cual invade frecuentemente el seno maxilar y se manifiesta con diferentes cuadros clínicos. Se clasifica como invasivo y no invasivo; donde esta última se subdivide en bola fúngica y rinosinusitis fúngica alérgica. Reporte de caso: presentamos un caso de rinosinusitis fúngica no invasiva en una paciente inmunocompetente, donde se observan imágenes endoscópicas y radiológicas de bola fúngica en el seno maxilar. Discusión: Es resaltante debido a la dificultad que representa su diagnóstico en la consulta de atención primaria, no sólo por su baja prevalencia, sino también por la presentación atípica del mismo