Atomic-Scale Variations of the Mechanical Response of 2D Materials Detected by Noncontact Atomic Force Microscopy.

We show that noncontact atomic force microscopy (AFM) is sensitive to the local stiffness in the atomic-scale limit on weakly coupled 2D materials, as graphene on metals. Our large amplitude AFM topography and dissipation images under ultrahigh vacuum and low temperature resolve the atomic and moiré patterns in graphene on Pt(111), despite its extremely low geometric corrugation. The imaging mechanisms are identified with a multiscale model based on density-functional theory calculations, where the energy cost of global and local deformations of graphene competes with short-range chemical and long-range van der Waals interactions. Atomic contrast is related with short-range tip-sample interactions, while the dissipation can be understood in terms of global deformations in the weakly coupled graphene layer. Remarkably, the observed moiré modulation is linked with the subtle variations of the local interplanar graphene-substrate interaction, opening a new route to explore the local mechanical properties of 2D materials at the atomic scale.

Research of international suicide.

Twenty two variables of social, economic, geographic and psychological significance, including suicide rate, were factor analysed for forty world nations. Five factors achieved eigenvalues of 1.00 or more, which were the Modern Technological State (France, Germany, Sweden), the Affluent State (the U.S.A.), the City-State (Israel, Singapore), the Horizontal Society (Chile, Guatamala), and the Developing Nation (Guyana, Costa Rica). A high national suicide rate was found to be significantly related to the Modern Technological State (P less than .001), and a low national suicide rate was found to be significantly associated with the Horizontal Nation (P less than .05). Results were interpreted in view of frustration theory and Durkheim's theory of suicide.