From conjecture generation by maintaining dragging to proof

In this paper we propose a hypothesis about how different uses of maintaining dragging, either as a physical tool in a dynamic geometry environment or as a psychological tool for generating conjectures can influence subsequent processes of proving. Through two examples we support the hypothesis that using maintaining dragging as a physical tool may foster cognitive rupture between the conjecturing phase and the proof, while using it as a psychological tool may foster cognitive unity between them.Comment: Research report at the 40th PME conference, Hungar

Widespread abiotic methane in chromitites

Recurring discoveries of abiotic methane in gas seeps and springs in ophiolites and peridotite massifs worldwide raised the question of where, in which rocks, methane was generated. Answers will impact the theories on life origin related to serpentinization of ultramafic rocks, and the origin of methane on rocky planets. Here we document, through molecular and isotopic analyses of gas liberated by rock crushing, that among the several mafic and ultramafic rocks composing classic ophiolites in Greece, i.e., serpentinite, peridotite, chromitite, gabbro, rodingite and basalt, only chromitites, characterized by high concentrations of chromium and ruthenium, host considerable amounts of 13C-enriched methane, hydrogen and heavier hydrocarbons with inverse isotopic trend, which is typical of abiotic gas origin. Raman analyses are consistent with methane being occluded in widespread microfractures and porous serpentine- or chlorite-filled veins. Chromium and ruthenium may be key metal catalysts for methane production via Sabatier reaction. Chromitites may represent source rocks of abiotic methane on Earth and, potentially, on Mars

Learning from errors: effects of teachers training on studentsâ attitudes towards and their individual use of errors

Constructive error handling is considered an important factor for individual learning processes. In a quasi-experimental study with Grades 6 to 9 students, we investigate effects on students’ attitudes towards errors as learning opportunities in two conditions: an error-tolerant classroom culture, and the first condition along with additional teaching of strategies for analyzing errors. Our findings show positive effects of the error-tolerant classroom culture on the affective level, whereas students are not influenced by the cognitive support. There is no evidence for differential effects for student groups with different attitudes towards errors

Fluid inclusion study of the Boccassuolo VMS-related stockwork deposit (Northern-Apennine ophiolites, Italy)

Several Cyprus-type volcanogenic massive sulphide (VMS) deposits are found in the Jurassic ophiolitic series of the Northern Apennines. Stratabound, stratiform and stockwork deposits were formed in the western limb of the Neotethys (Ligurian Ocean) and are found today in basalt, gabbro and serpentinised peridotite host rocks. The studied stockwork deposit at Boccassuolo is found in basalt and basalt breccia. Detailed petrography, fluid inclusion study, Raman spectroscopy analyses and chlorite thermometry calculations were used to determine the P, T, X conditions of the fluid circulation system. The veins contain three quartz generations, calcite, chlorite, epidote and sericite as gangue minerals and pyrite, chalcopyrite, sphalerite, pyrrhotite and galena as ore minerals. Based on the fluid inclusion study, the earlier defined three vein types (1., 2. and 3.) precipitated from the same type of evolving fluid, though at slightly different stratigraphical positions. The determined ranges of temperature (370 60°C), salinity (6.2 11.4 NaCl equiv. wt%), pressure (30-44 MPa) ranges and methane content (average 0.28 mol/kg) suggest an evolved seawater origin for the hydrothermal fluid, modified by fluid-rock interaction and possibly by mixing of magmatic volatile. The fluid characteristics and the mineralogical observations have proven a slightly distal position in relation to the centre of the fluid flow for all studied locations, but less and more distal blocks were also recognised. The temporal evolution of the system developed into a low temperature event, occurring after the main mineral stage, but still participating to the same process as a whole.</p

The Fundamental Group Scheme of a non Reduced Scheme

We extend the definition of fundamental group scheme to non reduced schemes over any connected Dedekind scheme. Then we compare the fundamental group scheme of an affine scheme with that of its reduced part.Comment: Final version, 11 pages, minor change

La Capella di Santa Caterina di Alessandria nella Chiesa di Santa Maria in Castello. Carpi, Modena, Italia.

El presente estudio se ha centrado en analizar la capilla de Santa Catalina de Alejandría situada en la iglesia de Santa María in Castello de Carpi, Módena. En primer lugar, hemos querido fijar nuestra atención en los trabajos realizados y publicados con anterioridad al nuestro, situando a continuación el marco espacio temporal en el que se realizaron las pinturas y su contexto local, pasamos después al análisis de los temas iconográficos que encontramos en paredes y techo de la estancia. Los argumentos que se disponen en forma de fresco al intonaco, versan sobre la hagiografía de Santa Catalina de Alejandría y la imagen de la Anunciación, todo ello coronado por un discurso angélico de Dios Padre y el tetramorfos. Es en este análisis iconográfico donde hemos centrado nuestro trabajo y una de las razones de que el estudio biográfico del artista al que algunos atribuyen las pinturas se encuentre al final de este ensayo como ya hemos mencionado en la introducción. Podemos adelantar que el posible pintor es Giovanni da Módena, activo entre el 1398 y 1454 en esta zona de la Emilia Romagna entre Módena y Bolonia. Finalmente cabe destacar la presencia de otros frescos con estos mismos temas iconográficos en Italia en el siglo XIV y XV que nos sirven de justificación para la identificación de los temas, así como de ejemplos predecesores de los modelos iconográficos que aquí encontramos