Activitat 5. J.-H. Fragonard

Material didàctic del grup d'investigació Observatori sobre la Didàctica de les Arts (ODAS)

X-ray diffraction, thermal analysis, and Raman scattering study of K2BeF4 and comparation to other member of the (beta)-K2SO4 family with ferroelectric -paraelectric transition

Thermal analysis, powder diffraction, and Raman scattering as a function of the temperature were carried out on K2BeF4. Moreover, the crystal structure was determined at 293 K from powder diffraction. The compound shows a transition from Pna21 to Pnam space group at 921 K with a transition enthalpy of 5 kJ/mol. The transition is assumed to be first order because the compound shows metastability. Structurally and spectroscopically the transition is similar to those observed in (NH4)2SO4, which suggests that the low-temperature phase is ferroelectric. In order to confirm it, the spontaneous polarization has been computed using an ionic model.

Immunològic i immunitari: un esforç il·lògic? [pòster]

Pòster presentat al I Congrés Internacional de Neologia de les Llengües Romàniques (CINEO 2008).

Immunològic i immunitari: un esforç il·lògic? [edició preliminar]

Edició preliminar de l’article publicat en les actes del I Congrés Internacional de Neologia de les Llengües Romàniques (CINEO 2008).