Tooth eruption disorder: 2 cases.

Tooth eruption disorders can have several different causes and treatment options. An 8-year-old boy's tooth 12 erupted in the position of tooth 11, and an 11-year-old girl's tooth 21 did not erupt. In both cases, an attempt was made to regulate the relevant tooth orthodontically, but ultimately it was found necessary to extract the tooth.

Attractive curves: the role of deformations in adhesion and friction on graphene.

Friction force microscopy measurements reveal a dramatic difference of a factor 3 between the friction forces experienced on single-monolayer graphene on top of oxidized and unoxidized copper substrates. We associate this difference with the strong and weak adhesion that the graphene experiences on these two substrates, respectively, but argue that it is too large to be ascribed either to a difference in contact area or to a difference in contact commensurability or even to a combination of these two effects. We use density functional theory to show a significant increase in the chemical reactivity of graphene when it is curved.

Atomistic mechanisms for frictional energy dissipation during continuous sliding.

After more than a century of detailed investigations into sliding friction, we have not arrived yet at a basic understanding of energy dissipation, even for the simple geometry of a rigid slider moving over a perfectly periodic counter surface. In this article, we use a first-principles-based analysis to establish the atomistic mechanisms of frictional energy dissipation for a rigid object that moves continuously in the periodic surface potential landscape of a solid with vibrational degrees of freedom. We identify two mechanisms that can be viewed as (i) the continuous pumping of energy into the resonant modes, if these exist, and (ii) the destructive interference of the force contributions introduced by all excited phonon modes.

The Coalescence Behavior of Two-Dimensional Materials Revealed by Multiscale Imaging during Chemical Vapor Deposition Growth.

Wafer-scale monocrystalline two-dimensional (2D) materials can theoretically be grown by seamless coalescence of individual domains into a large single crystal. Here we present a concise study of the coalescence behavior of crystalline 2D films using a combination of complementary methods. Direct observation of overlayer growth from the atomic to the millimeter scale and under model- and industrially relevant growth conditions reveals the influence of the film-substrate interaction on the crystallinity of the 2D film.