Stretching dependence of the vibration modes of a single-molecule Pt-H2-Pt bridge

A conducting bridge of a single hydrogen molecule between Pt electrodes is formed in a break junction experiment. It has a conductance near the quantum unit, G0=2e2∕h, carried by a single channel. Using point-contact spectroscopy three vibration modes are observed and their variation upon isotope substitution is obtained. The stretching dependence for each of the modes allows uniquely classifying them as longitudinal or transversal modes. The interpretation of the experiment in terms of a Pt-H2-Pt bridge is verified by density-functional theory calculations for the stability, vibrational modes, and conductance of the structure.

Independencia y fórmulas rutinarias: Reestructuración de la Esfera III

Este trabajo aborda el análisis de las unidades fraseológicas, en concreto, las fórmulas rutinarias conversacionales, según su grado de independencia, con el fin de reestructurar la Esfera III (Corpas, 1996), en la que se encuentran los enunciados fraseológicos, paremias y fórmulas rutinarias. Para ello, atenderemos al sistema de unidades que propone Briz y el Grupo Val.Es.Co. (Briz & Grupo Val.Es.Co., 2003, 2014) para la segmentación de la conversación. Con este sistema comprobaremos que los enunciados fraseológicos mostrarán diferentes grados y tipos de independencia que permitirán reestructurar la Esfera III. La metodología empleada se corresponde con el enfoque fraseológico y pragmático, y los ejemplos se han extraído del Corpus de conversaciones coloquiales (Briz & Grupo Val.Es.Co., 2002).

An updated evolutionary classification of CRISPR–Cas systems

The evolution of CRISPR–cas loci, which encode adaptive immune systems in archaea and bacteria, involves rapid changes, in particular numerous rearrangements of the locus architecture and horizontal transfer of complete loci or individual modules. These dynamics complicate straightforward phylogenetic classification, but here we present an approach combining the analysis of signature protein families and features of the architecture of cas loci that unambiguously partitions most CRISPR–cas loci into distinct classes, types and subtypes. The new classification retains the overall structure of the previous version but is expanded to now encompass two classes, five types and 16 subtypes. The relative stability of the classification suggests that the most prevalent variants of CRISPR–Cas systems are already known. However, the existence of rare, currently unclassifiable variants implies that additional types and subtypes remain to be characterized.