Unconventional non-local relaxation dynamics in a twisted trilayer graphene moiré superlattice

The electronic and structural properties of atomically thin materials can be controllably tuned by assembling them with an interlayer twist. During this process, constituent layers spontaneously rearrange themselves in search of a lowest energy configuration. Such relaxation phenomena can lead to unexpected and novel material properties. Here, we study twisted double trilayer graphene (TDTG) using nano-optical and tunneling spectroscopy tools. We reveal a surprising optical and electronic contrast, as well as a stacking energy imbalance emerging between the moiré domains. We attribute this contrast to an unconventional form of lattice relaxation in which an entire graphene layer spontaneously shifts position during assembly, resulting in domains of ABABAB and BCBACA stacking. We analyze the energetics of this transition and demonstrate that it is the result of a non-local relaxation process, in which an energy gain in one domain of the moiré lattice is paid for by a relaxation that occurs in the other

5-aminolevulinic Acid fluorescence in high grade glioma surgery: surgical outcome, intraoperative findings, and fluorescence patterns.

Background. 5-Aminolevulinic acid (5-ALA) fluorescence is a validated technique for resection of high grade gliomas (HGG); the aim of this study was to evaluate the surgical outcome and the intraoperative findings in a consecutive series of patients. Methods. Clinical and surgical data from patients affected by HGG who underwent surgery guided by 5-ALA fluorescence at our Department between June 2011 and February 2014 were retrospectively evaluated. Surgical outcome was evaluated by assessing the resection rate as gross total resection (GTR) > 98 % and GTR > 90 %. We finally stratified data for recurrent surgery, tumor location, tumor size, and tumor grade (IV versus III grade sec. WHO). Results. 94 patients were finally enrolled. Overall GTR > 98 % and GTR > 90 % was achieved in 93% and 100% of patients. Extent of resection (GTR > 98 %) was dependent on tumor location, tumor grade (P < 0.05), and tumor size (P < 0.05). In 43% of patients the boundaries of fluorescent tissue exceeded those of tumoral tissue detected by neuronavigation, more frequently in larger (57%) (P < 0.01) and recurrent (60%) tumors. Conclusions. 5-ALA fluorescence in HGG surgery enables a GTR in 100% of cases even if selection of patients remains a main bias. Recurrent surgery, and location, size, and tumor grade can predict both the surgical outcome and the intraoperative findings

Estudio mediante espectroscopía de absorción de rayos X de vidrios de PbO-Nb2O5-GeO2 en lámina delgada producidos mediante depósito por laser pulsado: Presencia de Nb4+ y su efecto en la respuesta óptica

Gijón (España), del 8 al 10 de junio de 2016En trabajos previos hemos depositado láminas delgadas transparentes de vidrios de Nb2O5-PbO-GeO2 mediante depósito por láser pulsado (PLD) a una presión de O2 de 5 Pa. Los vidrios en lámina delgada presentaron buenas propiedades ópticas lineales con un índice de refracción lineal (n> 2 ) y un coeficiente de absorción reducido en el visible e infrarrojo cercano, mientras que su respuesta óptica no lineal, caracterizada mediante la medida del módulo de la susceptibilidad óptica no lineal de tercer orden (/¿(3)/), mostró un valor muy elevado (/¿(3)/~ 10-11 esu at 800 nm, que es 103 veces mayor que el del SiO2 vítreo) para las láminas con un mayor contenido de Nb, que se crecieron a partir de opales. Dicho comportamiento se relacionó con las modificaciones estructurales observadas en las láminas delgadas respecto a los opales de partida: aumento de la fracción de oxígenos no puente y deficiencia de oxígeno que se relacionó con una posible reducción parcial de los cationes de Nb5+ presentes en las láminas. En el presente trabajo se ha desarrollado un análisis exhaustivo mediante espectroscopia de absorción de rayos X (XAS) para determinar el entorno local del Nb y confirmar su estado de oxidación en los vidrios en lámina delgada. Para ello se han preparado vidrios en lámina delgada en un intervalo amplio de presiones de oxígeno (10-4 - 5 Pa), lo que ha permitido demostrar la presencia de una fracción significativa de iones de Nb4+, que puede alcanzar el 100% en las láminas que presentan una deficiencia de oxígeno, mientras que dicho porcentaje se reduce hasta valores cercanos al 20% para las láminas depositadas a 5 Pa.Peer Reviewe