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

Lead-related quantum emitters in diamond

We report on quantum emission from Pb-related color centers in diamond following ion implantation and high-temperature vacuum annealing. First-principles calculations predict a negatively charged Pb-vacancy (PbV) center in a split-vacancy configuration, with a zero-phonon transition around 2.4 eV. Cryogenic photoluminescence measurements performed on emitters in nanofabricated pillars reveal several transitions, including a prominent doublet near 520 nm. The splitting of this doublet, 5.7 THz, exceeds that reported for other group-IV centers. These observations are consistent with the PbV center, which is expected to have a combination of narrow optical transitions and stable spin states, making it a promising system for quantum network nodes.U.S. Army Research Laboratory. Center for Distributed Quantum InformationNational Science Foundation (U.S.). Graduate Research Fellowship ProgramNational Science Foundation (U.S.) (Grant DMR-1231319)United States. National Aeronautics and Space Administration (Space Technology Research Fellowship)MIT-Harvard Center for Ultracold Atoms MIT International Science and Technology Initiativ

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

Low penetrance susceptibility to glioma is caused by the TP53 variant rs78378222.

Background: Most of the heritable risk of glioma is presently unaccounted for by mutations in known genes. In addition to rare inactivating germline mutations in TP53 causing glioma in the context of the Li-Fraumeni syndrome, polymorphic variation in TP53 may also contribute to the risk of developing glioma. Methods: To comprehensively evaluate the impact of variation in TP53 on risk, we analysed 23 tagSNPs and imputed 2377 unobserved genotypes in four series totaling 4147 glioma cases and 7435 controls. Results: The strongest validated association signal was shown by the imputed single-nucleotide polymorphism (SNP) rs78378222 (P = 6.86 x 10(-24), minor allele frequency similar to 0.013). Confirmatory genotyping confirmed the high quality of the imputation. The association between rs78378222 and risk was seen for both glioblastoma multiforme (GBM) and non- GBM tumours. We comprehensively examined the relationship between rs78378222 and overall survival in two of the case series totaling 1699 individuals. Despite employing statistical tests sensitive to the detection of differences in early survival, no association was shown. Conclusion: Our data provided strong validation of rs78378222 as a risk factor for glioma but do not support the tenet that the polymorphism being a clinically useful prognostic marker. Acquired TP53 inactivation is a common feature of glioma. As rs78378222 changes the polyadenylation signal of TP53 leading to impaired 3'-end processing of TP53 mRNA, the SNP has strong plausibility for being directly functional contributing to the aetiological basis of glioma

Deciphering the 8q24.21 association for glioma.

We have previously identified tagSNPs at 8q24.21 influencing glioma risk. We have sought to fine-map the location of the functional basis of this association using data from four genome-wide association studies, comprising a total of 4147 glioma cases and 7435 controls. To improve marker density across the 700 kb region, we imputed genotypes using 1000 Genomes Project data and high-coverage sequencing data generated on 253 individuals. Analysis revealed an imputed low-frequency SNP rs55705857 (P = 2.24 × 10(-38)) which was sufficient to fully capture the 8q24.21 association. Analysis by glioma subtype showed the association with rs55705857 confined to non-glioblastoma multiforme (non-GBM) tumours (P = 1.07 × 10(-67)). Validation of the non-GBM association was shown in three additional datasets (625 non-GBM cases, 2412 controls; P = 1.41 × 10(-28)). In the pooled analysis, the odds ratio for low-grade glioma associated with rs55705857 was 4.3 (P = 2.31 × 10(-94)). rs55705857 maps to a highly evolutionarily conserved sequence within the long non-coding RNA CCDC26 raising the possibility of direct functionality. These data provide additional insights into the aetiological basis of glioma development