Local sublattice-symmetry breaking in rotationally faulted multilayer graphene

Interlayer coupling in rotationally faulted graphene multilayers breaks the local sublattice-symmetry of the individual layers. We present a theory of this mechanism, which reduces to an effective Dirac model with space-dependent mass in an important limit. It thus makes a wealth of existing knowledge available for the study of rotationally faulted graphene multilayers. We demonstrate quantitative agreement between our theory and a recent experiment.Comment: Valley dependence in Eqs. (2) and (7) corrected; coordinates x and y interchanged in the appendi

Telomere length as a predictor of emotional processing in the brain

Shorter telomere length (TL) has been associated with the development of mood disorders as well as abnormalities in brain morphology. However, so far, no studies have considered the role TL may have on brain function during tasks relevant to mood disorders. In this study, we examine the relationship between TL and functional brain activation and connectivity, while participants (n = 112) perform a functional magnetic resonance imaging (fMRI) facial affect recognition task. Additionally, because variation in TL has a substantial genetic component we calculated polygenic risk scores for TL to test if they predict face-related functional brain activation. First, our results showed that TL was positively associated with increased activation in the amygdala and cuneus, as well as increased connectivity from posterior regions of the face network to the ventral prefrontal cortex. Second, polygenic risk scores for TL show a positive association with medial prefrontal cortex activation. The data support the view that TL and genetic loading for shorter telomeres, influence the function of brain regions known to be involved in emotional processing

Monitoring Barren-Ground Caribou Body Condition with Denésoliné Traditional Knowledge

Information from aboriginal elders and hunters on changes in barren-ground caribou (Rangifer tarandus) body condition can assist current management systems. Interviews with Denésoliné elders and hunters from Lutsël K’é, Northwest Territories, Canada, provided information on caribou body condition and environmental conditions. Hunters were accompanied in the field and asked to give a qualitative assessment of body condition for adult female caribou they harvested. Elders and hunters reported temporal and geographic variation in caribou body condition. Adult female caribou are selected in late winter (February to April) and bulls in fall (September) and spring (May) because they are fat. Hunters reported that adult female caribou were fatter during late winter in 2000 than in 2001. This difference was consistent with body condition impressions recorded in field surveys. Reports from hunters in interviews that adult female caribou were fatter in February than in March and April 2001 were also supported by hunters’ field impressions. Hunters identified areas where adult female caribou were in better condition than in other areas in 2000 and 2001. The number of caribou harvested and years of hunting experience influenced the distribution of hunters’ impressions of body condition. Interviews with hunters offer an inexpensive, repeatable approach to monitoring caribou body condition and range limitations, although ecological implications must be carefully interpreted.Des renseignements fournis par des aînés et des chasseurs autochtones sur les changements concernant l’état corporel du caribou des toundras (Rangifer tarandus) peuvent s’avérer utiles pour les systèmes actuels de gestion. Des entrevues menées auprès d’aînés et chasseurs Denésoliné de Lutsël K’é, dans les Territoires du Nord-Ouest au Canada, ont fourni des renseignements sur l’état corporel du caribou et sur les conditions environnementales. On a accompagné les chasseurs sur le terrain et on leur a demandé de faire une évaluation qualitative de l’état corporel des caribous femelles adultes qu’ils prélevaient. Les aînés et les chasseurs ont rapporté des variations temporelles et géographiques dans l’état corporel du caribou. Les femelles adultes sont prélevées à la fin de l’hiver (de février à avril) et les mâles à l’automne (en septembre) et au printemps (en mai) alors que ces animaux ont de bonnes réserves de gras. Les chasseurs ont rapporté que les caribous femelles adultes étaient plus grasses à la fin de l’hiver de 2000 que de celui de 2001. Cette différence allait de pair avec la perception relative à l’état corporel consignée lors des études sur le terrain. Les rapports de chasseurs affirmant lors d’entrevues que les caribous femelles adultes étaient plus grasses en février qu’en mars et avril 2001 étaient aussi corroborés par la perception des chasseurs sur le terrain. Ces derniers ont identifié des zones où, en 2000 et en 2001, les caribous femelles adultes étaient en meilleure condition physique qu’à d’autres endroits. Le nombre de caribous prélevés et les années d’expérience fondée sur la chasse influençaient la distribution de la perception des chasseurs relative à l’état corporel. Bien que l’interprétation des répercussions environnementales exige une certaine prudence, les entrevues menées auprès des chasseurs offrent néanmoins une approche peu coûteuse et reproductible pour suivre l’état corporel du caribou et les limites de son territoire

Evidence for Interlayer Electronic Coupling in Multilayer Epitaxial Graphene from Polarization Dependent Coherently Controlled Photocurrent Generation

Most experimental studies to date of multilayer epitaxial graphene on C-face SiC have indicated that the electronic states of different layers are decoupled as a consequence of rotational stacking. We have measured the third order nonlinear tensor in epitaxial graphene as a novel approach to probe interlayer electronic coupling, by studying THz emission from coherently controlled photocurrents as a function of the optical pump and THz beam polarizations. We find that the polarization dependence of the coherently controlled THz emission expected from perfectly uncoupled layers, i.e. a single graphene sheet, is not observed. We hypothesize that the observed angular dependence arises from weak coupling between the layers; a model calculation of the angular dependence treating the multilayer structure as a stack of independent bilayers with variable interlayer coupling qualitatively reproduces the polarization dependence, providing evidence for coupling.Comment: submitted to Nano Letter

Denésoliné (Chipewyan) Knowledge of Barren-Ground Caribou (Rangifer tarandus groenlandicus) Movements

Semi-directed interviews relating to the traditional knowledge (TK) of barren-ground caribou (Rangifer tarandus groenlandicus) movements were conducted with elders and hunters from the Denésoliné (Chipewyan) community of Lutsël K’é, Northwest Territories, Canada. The objective was to document Denésôliné knowledge of past and present caribou migration patterns and record their explanations for perceived changes in movements. Elders recognized expected and unusual levels of variation in caribou movements. Local narratives show that Denésoliné communities have a fundamental awareness of caribou migration cycles. Most elders thought fire frequency and intensity had increased over their lifetimes and that caribou numbers and distribution had been affected. The majority of Lutsël K’é elders thought mining development was affecting caribou movements in some way. Elders believe that disturbance around traditional migration corridors and water crossings and disturbance of “vanguard” animals might be forcing caribou to use less optimal routes and influencing where they overwinter. Elders also believe that a lack of respect for caribou will cause the animals to deviate from their “traditional” migration routes and become unavailable to the people for a period of time. Wildlife management practices may need to further accommodate aboriginal perspectives in the future.Des entrevues semi-dirigées relatives au savoir traditionnel (ST) sur les déplacements du caribou des toundras (Rangifer tarandus groenlandicus) ont été faites auprès d’aînés et de chasseurs de la communauté denésoliné (chippewyan) de Lutsël K’é, dans les Territoires du Nord-Ouest au Canada. L’objectif était de documenter le savoir denésôliné concernant les habitudes migratoires passées et présentes du caribou, et de consigner les explications sur les changements perçus dans les déplacements. Les aînés ont reconnu des niveaux de variation anticipés et inusités dans la migration du caribou. Des récits locaux révèlent que les communautés denésoliné possèdent une connaissance fondamentale des cycles de migration du caribou. La plupart des aînés étaient d’avis que la fréquence et l’intensité des feux de forêt avaient augmenté au cours de leur vie et que cela avait eu un impact sur le nombre et la distribution des caribous. La majorité des aînés de Lutsël K’é pensaient que l’exploitation minière affectait les déplacements du caribou, d’une manière ou d’une autre. Ils estimaient que les perturbations près des corridors de migration et des traversées de cours d’eau traditionnelles, ainsi qu’une perturbation subie par les animaux formant «l’avantgarde » de la harde, pourraient forcer les bêtes à suivre un trajet moins optimal et avoir une incidence sur leur site d’hivernage. Les aînés croyaient en outre qu’un manque de respect envers le caribou amènerait la harde à s’écarter de ses routes de migration «traditionnelles», la rendant inaccessible aux Autochtones pour une certaine durée. À l’avenir, il faudrait sans doute que les pratiques de gestion de la faune tiennent davantage compte du point de vue des Autochtones

A longitudinal study assessing depression in hepatitis C: does gender play a role in the new onset depression during interferon-alpha treatment?

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Perceptual processing advantages for trauma-related visual cues in post-traumatic stress disorder

BACKGROUND: Intrusive re-experiencing in post-traumatic stress disorder (PTSD) comprises distressing sensory impressions from the trauma that seem to occur 'out of the blue'. A key question is how intrusions are triggered. One possibility is that PTSD is characterized by a processing advantage for stimuli that resemble those that accompanied the trauma, which would lead to increased detection of such cues in the environment. METHOD: We used a blurred picture identification task in a cross-sectional (n=99) and a prospective study (n=221) of trauma survivors. RESULTS: Participants with acute stress disorder (ASD) or PTSD, but not trauma survivors without these disorders, identified trauma-related pictures, but not general threat pictures, better than neutral pictures. There were no group differences in the rate of trauma-related answers to other picture categories. The relative processing advantage for trauma-related pictures correlated with re-experiencing and dissociation, and predicted PTSD at follow-up. CONCLUSIONS: A perceptual processing bias for trauma-related stimuli may contribute to the involuntary triggering of intrusive trauma memories in PTSD

Spectroscopic Measurement of Interlayer Screening in Multilayer Epitaxial Graphene

International audienceThe substrate-induced charge-density profile in carbon face epitaxial graphene is determined using nondegenerate ultrafast midinfrared pump-probe spectroscopy. Distinct zero crossings in the differential transmission spectra are used to identify the Fermi levels of layers within the multilayer stack. Probing within the transmission window of the SiC substrate, we find the Fermi levels of the first four heavily doped layers to be, respectively, 360, 215, 140, and 93 meV above the Dirac point. The charge screening length is determined to be one graphene layer, in good agreement with theoretical predictions

Silicon intercalation into the graphene-SiC interface

In this work we use LEEM, XPEEM and XPS to study how the excess Si at the graphene-vacuum interface reorders itself at high temperatures. We show that silicon deposited at room temperature onto multilayer graphene films grown on the SiC(000[`1]) rapidly diffuses to the graphene-SiC interface when heated to temperatures above 1020. In a sequence of depositions, we have been able to intercalate ~ 6 ML of Si into the graphene-SiC interface.Comment: 6 pages, 8 figures, submitted to PR