Electric field-controlled rippling of graphene

International audienceMetal-graphene interfaces generated by electrode deposition induce barriers or potential modulations influencing the electronic transport properties of graphene based devices. However, their impact on the local mechanical properties of graphene is much less studied. Here we show that graphene near a metallic interface can exhibit a set of ripples self-organized into domains whose topographic roughness is controlled by the tip bias of a scanning tunneling microscope. The reconstruction from topographic images of graphene bending energy maps sheds light on the local electro-mechanical response of graphene under STM imaging and unveils the role of the stress induced by the vicinity of the graphene-metal interface in the formation and the manipulation of these ripples. Since microscopic rippling is one of the important factors that limit charge carrier mobility in graphene, the control of rippling with a gate voltage may have important consequences in the conductance of graphene devices where transverse electric fields are created by contactless suspended gate electrodes. This opens up also the possibility to dynamically control the local morphology of graphene nanomembranes

WORD USE AND CONTENT ANALYSIS OF THE FIRST VERSES OF SIX NATIONAL ANTHEMS: A TRANSCULTURAL ASPECT OF SUICIDAL BEHAVIOUR

Background: Suicide is a major health concern worldwide, although suicide rates widely differ among different countries and cultures. Transcultural studies suggest that national anthems reflect national attitudes towards self-harming behaviour as well. Our aim was to analyse the linguistic characteristics of six national anthems, and compare these results with national suicide rates. Methods: Word use assessment and content analysis of six national anthems were performed. Results: In the anthems of countries with similar historical or cultural background, similar linguistic patterns were found in word use and in content. Anthems of countries with lower suicide rates tend to contain relatively more positive contents, emotions and intentions, while in the anthems of countries with higher suicide rates more ambivalence, denial, loss or even aggressive and self-destructive implications were found. Conclusion: This transcultural analysis strengthens previous data that anthems could be indicators for national attitudes toward self-harm

Risk factors for suicide in Hungary: a case-control study

<p>Abstract</p> <p>Background</p> <p>Hungary previously had one of the highest suicide rates in the world, but experienced major social and economic changes from 1990 onwards. We aimed to investigate the antecedents of suicide in Hungary. We hypothesised that suicide in Hungary would be associated with both risk factors for suicide as identified in Western studies, and experiences related to social and economic restructuring.</p> <p>Methods</p> <p>We carried out a controlled psychological autopsy study. Informants for 194 cases (suicide deaths in Budapest and Pest County 2002–2004) and 194 controls were interviewed by clinicians using a detailed schedule.</p> <p>Results</p> <p>Many of the demographic and clinical risk factors associated with suicide in other settings were also associated with suicide in Hungary; for example, being unmarried or having no current relationship, lack of other social contacts, low educational attainment, history of self-harm, current diagnosis of affective disorder (including bipolar disorder) or personality disorder, and experiencing a recent major adverse life event. A number of variables reflecting experiences since economic restructuring were also associated with suicide; for example, unemployment, concern over work propects, changes in living standards, practising religion. Just 20% of cases with evidence of depression at the time of death had received antidepressants.</p> <p>Conclusion</p> <p>Suicide rates in Hungary are falling. Our study identified a number of risk factors related to individual-level demographic and clinical characteristics, and possibly recent societal change. Improved management of psychiatric disorder and self-harm may result in further reductions in suicide rates.</p

STM and STS investigation of few wall carbon nanotubes containing non-hexagonal carbon rings

International audienceWe performed scanning tunneling microscopy (STM) measurements on few wall carbon nanotubes that exhibited changing diameter. Such change in the diameter may occur if non-hexagonal carbon ring configurations are introduced in the nanotube walls. A few-walled nanotube knee of 4 degrees, with different diameter values on the two sides of the knee was imaged by STM. Theoretical model structures [J. Han et al., Phys. Rev. B 57 (1998) 14983] of single wall carbon nanotubes show that a bend of 4° may occur when a pentagonal and a heptagonal carbon ring is incorporated side by side in the hexagonal nanotube structure (i.e. "fused defect"). Scanning tunneling spectroscopic (STS) measurements show that additional electronic states are present in the energy gap in the region where the bend occurs. We also performed STS measurements on a single-wall nanotube with a conical tip. In agreement with theory, the results show that the energy gap in the tapered end is larger than in the nanotub