Lateral stiffness: A new nanomechanical measurement for the determination of shear strengths with friction force microscopy

We present a technique to measure the lateral stiffness of the nanometer-sized contact formed between a friction force microscope tip and a sample surface. Since the lateral stiffness of an elastic contact is proportional to the contact radius, this measurement can be used to study the relationship between friction, load, and contact area. As an example, we measure the lateral stiffness of the contact between a silicon nitride tip and muscovite mica in a humid atmosphere (55% relative humidity) as a function of load. Comparison with friction measurements confirms that friction is proportional to contact area and allows determination of the shear strength

Calibration of frictional forces in atomic force microscopy

The atomic force microscope can provide information on the atomic-level frictional properties of surfaces, but reproducible quantitative measurements are difficult to obtain. Parameters that are either unknown or difficult to precisely measure include the normal and lateral cantilever force constants (particularly with microfabricated cantilevers), the tip height, the deflection sensor response, and the tip structure and composition at the tip-surface contact. We present an in situ experimental procedure to determine the response of a cantilever to lateral forces in terms of its normal force response. This procedure is quite general. It will work with any type of deflection sensor and does not require the knowledge or direct measurement of the lever dimensions or the tip height. In addition, the shape of the tip apex can be determined. We also discuss a number of specific issues related to force and friction measurements using optical lever deflection sensing. We present experimental results on the lateral force response of commercially available V-shaped cantilevers. Our results are consistent with estimates of lever mechanical properties using continuum elasticity theory

Comparativa entre instrumentos de evaluación de calidad de cursos MOOC: ADECUR vs Normas UNE 66181:2012

Els cursos oberts en línia i massius (d’ara endavant, MOOC) s’han considerat en la literatura divulgativa i científica una revolució amb un gran potencial en el món educatiu i formatiu. No obstant això, al mateix temps, existeixen discrepàncies i qüestionaments sobre el valor pedagògic i l’abast que tindrà el moviment en l’educació superior. Així doncs, l’univers dels MOOC és objecte de reflexió didàctica i formativa entre diferents autors i institucions en el món globalitzat, però encara són necessàries unes dimensions i unes implicacions de la visió avaluadora d’aquests cursos que han de ser valorades i analitzades des de diferents punts de vista.En aquest article es presenta un panorama comparatiu dels indicadors de qualitat de dos instruments d’avaluació dels cursos MOOC: la Norma UNE 66181:2012 sobre la gestió de la qualitat de la formació virtual i l’instrument d’anàlisi didàctica de model i estratègies d’ensenyament de cursos universitaris en xarxa (ADECUR). Finalment, es plantejarà un disseny d’eina d’avaluació de qualitat de cursos MOOC sobre la base de les fortaleses dels dos instruments analitzats.Massive open online courses (MOOCs) have emerged in informative and scientific literature as a revolution with great potential within the educational and training world. However, at the same time, there are discrepancies and questions about the pedagogical value and scope that this movement has on higher education. Therefore, the MOOC universe is the object of educational consideration among various authors and institutions in the globalised world, but some dimensions and implications of their evaluation still need to be assessed and analysed from different perspectives.In this paper, we introduce a comparative overview of the quality indicators of two instruments for assessing MOOCs: Standard UNE 66181: 2012 on quality management for virtual teaching, and the training analysis instrument for teaching models and strategies of online university courses (ADECUR). Lastly, we will introduce the development of a tool for assessing the quality of MOOCs based on the strengths of the two instruments examined.Los cursos abiertos en línea y masivos (en adelante MOOC) se han considerado en la literatura divulgativa y científica como una revolución con un gran potencial en el mundo educativo y formativo. Sin embargo, al mismo tiempo, existen discrepancias y cuestionamientos sobre el valor pedagógico y el alcance que tendrá el movimiento en la educación superior. Así pues, el universo de los MOOC es objeto de reflexión didáctica y formativa entre diferentes autores e instituciones en el mundo globalizado, pero todavía son necesarias unas dimensiones y unas implicaciones de la visión evaluadora de los mismos que deben ser valoradas y analizadas desde diferentes puntos de vista.En este artículo se presenta un panorama comparativo de los indicadores de calidad de dos instrumentos de evaluación de los cursos MOOC: la Norma UNE 66181:2012 sobre la gestión de la calidad de la formación virtual y el instrumento de análisis didáctico de modelo y estrategias de enseñanza de cursos universitarios en red (ADECUR). Por último, se planteará un diseño de herramienta de evaluación de calidad de cursos MOOC en base a las fortalezas de los dos instrumentos analizados

Measurement of interfacial shear (friction) with an ultrahigh vacuum atomic force microscope

We have studied the variation of frictional force with externally applied load for a Pt-coated atomic force microscope tip in contact with the surface of mica cleaved in ultrahigh vacuum. At low loads, the frictional force varies with load in almost exact proportion to the area of contact as predicted by the Johnson-Kendall-Roberts (JKR) theory [K. L. Johnson, K. Kendall, and A. D. Roberts, Proc. R. Sec. London Ser. A 324, 301 (1971)] of elastic adhesive contacts. The friction-load relation for a deliberately modified tip shape was proportional to an extended JKR model that predicts the area-load relation for nonparabolic tips, The tip shape was determined experimentally with a tip imaging technique and was consistent with the predicted friction behavior. This demonstrates that the frictional force is proportional to the area of contact between the tip and sample. Using the JKR/extended JKR model, interfacial surface energies and shear strengths can be estimated

A variable temperature ultrahigh vacuum atomic force microscope

A new atomic force microscope (AFM) that operates in ultrahigh vacuum (UHV) is described. The sample is held fixed with spring clamps while the AMF cantilever and deflection sensor are scanned above it. Thus, the sample is easily coupled to a liquid nitrogen cooled thermal reservoir which allows AFM operation from ≈ 100 K to room temperature. AFM operation above room temperature is also possible. The microscope head is capable of coarse x-y positioning over millimeter distances so that AFM images can be taken virtually anywhere upon a macroscopic sample. The optical beam deflection scheme is used for detection, allowing simultaneous normal and lateral force measurements. The sample can be transferred from the AFM stage to a low energy electron diffraction/Auger electron spectrometer stage for surface analysis. Atomic lattice resolution AFM images taken in UHV are presented at 110, 296, and 430 K

EduTool®: Un instrumento para la evaluación y acreditación de la calidad de los MOOCs

Esta investigación analiza la calidad normativa de los cursos MOOCs (Massive Open Online Courses) a través del instrumento EduTool®, marca registrada en la Oficina Española de Patentes y Marcas (3.087.298, en vigor). Surge de una línea de trabajo de investigación de la Universidad Pablo de Olavide (Sevilla) y desarrollada en el Laboratorio de Inteligencia Computacional (LIC). EduTool® se desarrolla bajo los auspicios de la norma UNE 66181 y en el LIC se han analizado las ponderaciones de los subfactores de cada una de las dimensiones (reconocimiento de la formación, metodología de aprendizaje y niveles de accesibilidad) de esta norma sobre la Gestión de la Calidad de la Formación Virtual a los MOOCs mediante lógica difusa. En este sentido, la agregación de las variables lingüísticas de 10 jueces expertos se realizó mediante la función OR probabilística y se desfusificaron mediante el método del centroide de área para calcular las citadas ponderaciones. Para medir la calidad de los cursos se procedió a buscar y seleccionar relevantes plataformas MOOC: Udacity, EdX, MiríadaX y Coursera. Posteriormente, por muestreo no probabilístico intencional se seleccionaron los cursos MOOCs más relevantes relativos a las categorías de informática y ciencias de la computación. Para este procedimiento de recogida de información, se habilitaron en dichas plataformas a dos ingenieros informáticos para la codificación y valoración de la calidad de estos cursos utilizando el citado instrumento. Los resultados analíticos y gráficos muestran que, de forma general, la calidad de la media de los MOOCs analizados en cada plataforma se sitúa por encima de la puntuación que describe el mínimo exigido (50%). Así pues, se apreció una calidad media superior en las plataformas Coursera (66,34%) y EdX (62,62%), intermedia en la plataforma Udacity (54,92%) y algo inferior en la plataforma MiríadaX (50,40%)

Atomic Force Microscopy Study of an Ideally Hard Contact: The Diamond(111)/Tungsten Carbide Interface

A comprehensive nanotribological study of a hydrogen-terminated diamond(111)/tungsten carbide interface has been performed using ultrahigh vacuum atomic force microscopy. Both contact conductance, which is proportional to contact area, and friction have been measured as a function of applied load. We demonstrate for the first time that the load dependence of the contact area in UHV for this extremely hard single asperity contact is described by the Derjaguin-Müller-Toporov continuum mechanics model. Furthermore, the frictional force is found to be directly proportional to the contact area

Museums as agents of community building in the city of Almeria. Analysis of the «Culture served in ceramics» experience

©2023. The authors. This document is made available under the CC-BY-NC-SA 4.0 license http://creativecommons.org/licenses/by-nc-sa/4.0/ This document is the published version of a Published Work that appeared in final form in Diferents. To access the final edited and published work see https://dx.doi.org/10.6035/diferents.7655Este artículo presenta los principales resultados de la experiencia «Cultura servida en cerámica», desarrollada en la ciudad de Almería con la implicación de diferentes colectivos vulnerables en un entorno museístico. Con este propósito se plantea el objetivo de analizar el impacto que a nivel educativo ha tenido este proyecto de intervención comunitaria entre sus participantes. La metodología empleada fue de tipo cualitativa, por medio de entrevistas y grupos de discusión. Los informantes fueron seleccionados a través de muestreo no probabilístico, y por conveniencia. Los resultados indican que las actitudes de los destinatarios del programa tuvieron una gran influencia en su contexto cultural, posibilidades artísticas, educativas, así como en la formación de nuevas redes sociales. Se puede concluir que la iniciativa desarrollada es idónea para establecer un marco de referencia que promueva una reflexión crítica y participativa en el espacio museístico de colectivos en riesgo de exclusión.This paper presents the main results of the «Culture served in ceramics» experience, developed in the city of Almería, with the involvement of different vulnerable groups in the museum environment. With this purpose, the objective is to analyze the impact that this community intervention project has had among its participants at an educational level. The methodology used was qualitative, through interviews and discussion groups. The participants were selected through non-probabilistic sampling, and for convenience. The results show that the attitudes of the beneficiaries of the program had a great impact regarding their cultural context, artistic, educational possibilities, as well as the creation of new social networks. It should be concluded that the initiative developed becomes an ideal proposal to establish a reference framework that favors a critical and participatory reflection from the museum space from groups at risk of exclusion

Food Consumption and its Impact on Cardiovascular Disease: Importance of Solutions Focused on the Globalized Food System A Report From the Workshop Convened by the World Heart Federation

Major scholars in the field, based on a 3-day consensus, created an in-depth review of current knowledge on the role of diet in CVD, the changing global food system and global dietary patterns, and potential policy solutions. Evidence from different countries, age/race/ethnicity/socioeconomic groups suggest the health effects studies of foods, macronutrients, and dietary patterns on CVD appear to be far more consistent though regional knowledge gaps are highlighted. There are large gaps in knowledge about the association of macronutrients to CVD in low- and middle-income countries (LMIC), particularly linked with dietary patterns are reviewed. Our understanding of foods and macronutrients in relationship to CVD is broadly clear; however major gaps exist both in dietary pattern research and ways to change diets and food systems. Based on the current evidence, the traditional Mediterranean-type diet, including plant foods/emphasizing plant protein sources, provides a well-tested healthy dietary pattern to reduce CV