Interpretación de indicadores discursivos en situación de aprendizaje matemático en pareja

En este informe, presentamos el análisis de datos de una pareja de estudiantes durante la resolución de un problema de generalización en una clase de matemáticas de secundaria (15-16 años). De acuerdo con las teorías interaccionistas del aprendizaje matemático, asumimos que el discurso establecido en la interacción en pareja es un factor clave de influencia en los procesos de construcción de conocimiento matemático. Hasta ahora, los resultados ponen de relieve la relación entre el uso de ciertos indicadores discursivos y los avances en la "intención argumentativa" de las estudiantes. La mayoría de intercambios con intención argumentativa vienen precedidos o acompañados por refutación y cuestionamiento, y en menor grado, validación. La refinación del análisis actual se está realizando dentro del trabajo de tesis doctoral de la primera autora

Minimal set of generators of controllability space for singular linear dynamical systems

Due to the significant role played by singular systems in the form E ¿ x ( t ) = Ax ( t ) , on mathematical modeling of science and engineering problems; in the last years recent years its interest in the descriptive analysis of its structural and dynamic properties. However, much less effort has been devoted to studying the exact con- trollability by measuring the minimum set of controls needed to direct the entire system E ¿ x ( t ) = Ax ( t ) to any desired state. In this work, we focus the study on obtaining the set of all matrices B with a minimal number of columns, by making the singular system E ¿ x ( t ) = Ax ( t ) + Bu ( t ) controllable.Postprint (author's final draft

High-valent bismuth redox catalysis

In the last years, bismuth has transitioned from being considered a mere Lewis acid catalyst to being recognised as an interesting redox catalyst for organic synthesis. A rational design of a ligand scaffold for the Bi center resulted in a robust catalytic system applicable to various bismuth redox processes

Bilinear softening parameters and equivalent LEFM R-curve in quasibrittle failure

For composites and adhesive joints, the determination of the cohesive zone parameters from Double Cantilever Beam specimens loaded with pure moments is now well established and documented. However, for quasibrittle materials used in Civil Engineering such as concrete or wood, the difficulty to apply a pure bending moment lies inappropriated the method used for composites. Nevertheless, the one-to-one correspondence which exists between the R-curve and the softening curve is here revisited and adapted for any kind of specimen geometry and for the bilinear approximation of the softening function, well-known to successfully describe the failure of a wide group of quasibrittle materials. It is shown that even though the connections between the cohesive parameters and the ‘equivalent LEFM’ R-curve are geometry and material dependent, their trends are preserved whatever the specimen geometry and the material are. The outline of a general estimation procedure of the cohesive zone parameters funded on the equivalent LEFM R-curve is proposed

Computational Study of Enantioselective Carboligation Catalyzed by Benzoylformate Decarboxylase

Benzoylformate decarboxylase (BFDC) is a thiamin-diphosphate enzyme that catalyzes the decarboxylation of benzoylformate to yield benzaldehyde and carbon dioxide. In addition to its natural reaction, BFDC is able to catalyze carboligation reactions in a highly enantioselective fashion, making the enzyme a potentially important biocatalyst. Here we use density functional theory calculations to investigate the detailed mechanism of BFDC-catalyzed carboligation and to elucidate the sources of the enantioselectivity. Benzaldehyde and acetaldehyde are studied as acceptors, for, when reacting with a benzaldehyde donor, they yield products with opposite enantiospecificity. For each of the acceptors, several possible binding modes to the active site are initially examined before the individual reaction paths leading to the two enantiomeric products are followed. The calculated energies are in good agreement with the experimental results, and the analysis of the transition states gives insight into the origins of the enantioselectivity