Rosa Giménez Moreno

Powder diffraction analysis of gemstone inclusions

Gemstones are pieces of materials that once cut and polished are used as jewels or adornments. Gemstones may be single crystal such as diamonds , polycrystalline such as lapis lazuli , or amorphous such as amber . In any case, gems may have inclusions that may yield a variety of optic effects. It is also important to unravel the crystal structure of the inclusion s in order to determine the origin of the gem and to help to understand their formation mechanism. Here, we expand the use of powder diffraction to identify crystalline inclusions in bulk gemstones highlighting Mo K radiation to penetrate within compact gems. Initially, rock crystal quartz with rutile needles was investigated and rutile diffraction peaks were more conspicuous in the Mo pattern than in the Cu pattern. Next, rock crystal quartz with beetle legs was characterized and the red iron oxide inclusion was identified as hematite. The study of a fake gem, glass showing aventurine effect, gave the diffraction peaks of metallic copper. Later, polycrystalline gems, moss agate, and aventurine quartz were also studied. The powder patterns of these compact gemstones could be successfully fitted using the Rietveld method. Finally, we discuss opportunities for further improvements in laboratory powder diffraction to characterize inclusions in compact gems.

ROLES Y REGISTROS EN LA INTERACCIÓN EN LOS FOROS DIGITALES: DESARROLLO DE UN ENFOQUE BASADO EN INDENTIDADES COMUNICATIVAS PARA EL ESTUDIO DE LA VARIACIÓN DE REGISTRO

espanolEl presente articulo estudia como los roles y registros comunicativos se expresan de forma interdependiente, influenciandose mutuamente en los actuales foros digitales. En la primera parte, y a partir de la combinacion de estudios previos sobre variacion de registros comunicativos, la teoria de la identidad social y la linguistica cognitiva, se proponen tres nuevos conceptos para el analisis discursivo: ‘Rol Modulador de Registro’ (RMR), ‘brujula del registro’ y ‘registro-pivote’. La forma en la que funcionan en el discurso digital se ilustra en la segunda parte, con el analisis de un corpus de foros de discusion. Los resultados demuestran que cada perfil de foro despliega una gama diferente de RMR, junto con sus registros asociados, y que todos ellos tienden a emerger y alternar alrededor de un registropivote prominente. En nuestro corpus se identifican tres claros registros-pivote con sus rasgos linguisticos distintivos. El estudio sustenta la estrecha relacion entre identidades relacionales o roles comunicativos y registros linguisticos en el discurso digital y facilita herramientas discursivas para el analisis, la comprension y el uso de la variacion del registro en la interaccion actual a traves de internet. EnglishThe paper studies how communicative roles and registers are expressed in an interdependent way, influencing each other in current forums. In the first part, by combining previous insights in register variation analysis, social identity theory and cognitive linguistics, three new concepts for linguistic analysis are proposed: ‘Register-Modulating Role’ (RMR), ‘Register compass’ (R-compass) and ‘pivotal register’. The way they function in digital discourse is illustrated in the second part by analysing an open discussion forum sample corpus. The results show that each forum’s profile displays a different array of RMR, together with their associated registers, which tend to spin around a prominent pivotal register. In our corpus three salient pivotal registers are identified, together with their associated registers and distinctive language features. The study substantiates the close connection between relational identities or roles and registers in digital discourse, and facilitates linguistic devices for a better use and understanding of register variation and forum discourse.