On-surface chemical dynamics of monolayer, bilayer, and many-layered graphene surfaces probed with supersonic beam scattering and STM imaging.

We have developed the capability to elucidate interfacial reaction dynamics using an arguably unique combination of supersonic molecular beams combined with in situ STM visualization. These capabilities have been implemented in order to reveal the complex spatiotemporal correlations that govern the oxidation of graphitic systems spanning atomic-, nano-, and meso-length scales. In this study, the 3 nm periodic moiré pattern of monolayer and bilayer graphene on Ru(0001) provides a diverse palette of potential scattering and binding sites at the interface for ground state atomic oxygen. We resolve the site-specificity of atomic oxygen placement on the moiré lattice for both monolayer and bilayer graphene on Ru(0001) with atomic resolution. Angle- and energy-controlled scattering of O(3P) on these interfaces reveals an incisive side-by-side comparison of preferential reactivity of the monolayer surface compared to a more free-standing bilayer graphene ruthenium interface. Morphologically dependent reactivity of many layered graphene (HOPG) and monolayer graphene on Ru(0001) reveal anisotropic on-surface reactivity dependent on the presence of proximal reacted sites or local regions. The kinetics of on-surface oxidation are additionally shown to influence the morphology of surface products by varying the temperature of the interface and flux of reactant species. Such correlations are important in chemisorption, catalysis, materials oxidation and erosion, and film processing-and tunable moiré templated adsorption is a route to well-ordered self-assembled 2D materials for use in next-generation platforms for quantum devices and catalysis. Taken together, these results highlight a new direction in the examination of interfacial reaction dynamics where incident beam kinetic energy and angle of incidence can be used as reaction control parameters, with outcomes such as site-specific reactivity, changes for overall time-evolving mechanisms, and the relative importance of non-adiabatic channels in adsorption all linked to the on-surface fate of chemisorbed species.

Coverage-Dependent Site-Specific Placement and Correlated Diffusion of Atomic Oxygen on Moiré-Patterned Graphene on Ru(0001).

Nano-periodic arrays of atomic oxygen are visualized on epitaxial graphene on Ru(0001) via STM following supersonic beam exposure to non-equilibrium fluxes of atomic oxygen. Self-organization of atomic oxygen on graphene is directed by the intrinsic moiré pattern of the ruthenium-graphene interface. Atom-resolved STM imaging reveals the richness of multiparticle interactions, leading to correlated atomic diffusion and placement. Pair-distribution functions demonstrate that repulsive oxygen-oxygen interactions play an increasingly important role in the site specificity and diffusivity of atomic oxygen on the moiré lattice with increasing coverage. Atomic visualization shows the number of oxygen atoms in a local region changes overall diffusion rates and promotes the correlated motion of oxygen atoms. Understanding the site specificity of oxygen adsorption and diffusive behavior of atomic oxygen on epitaxial graphene on Ru(0001) provides insight for both the synthesis and stability of moiré-templated two-dimensional materials which show promise as platforms for next-generation quantum materials and catalysts.

STM Visualization of N2 Dissociative Chemisorption on Ru(0001) at High Impinging Kinetic Energies.

This paper examines the reactive surface dynamics of energy- and angle-selected N2 dissociation on a clean Ru(0001) surface. Presented herein are the first STM images of highly energetic N2 dissociation on terrace sites utilizing a novel UHV instrument that combines a supersonic molecular beam with an in situ STM that is in-line with the molecular beam. Atomically resolved visualization of individual N2 dissociation events elucidates the fundamental reactive dynamics of the N2/Ru(0001) system by providing a detailed understanding of the on-surface dissociation dynamics: the distance and angle between nitrogen atoms from the same dissociated N2 molecule, site specificity and coordination of binding on terrace sites, and the local evolution of surrounding nanoscopic areas. These properties are precisely measured over a range of impinging N2 kinetic energies and angles, revealing previously unattainable information about the energy dissipation channels that govern the reactivity of the system. The experimental results presented in this paper provide insight into the fundamental N2 dissociation mechanism that, in conjunction with ongoing theoretical modeling, will help determine the role of dynamical processes such as energy transfer to surface phonons and nonadiabatic excitation of electron-hole pairs (ehps). These results will not only help uncover the underlying chemistry and physics that give rise to the unique behavior of this activated dissociative chemisorption system but also represent an exciting approach to studying reaction dynamics by pairing the angstrom-level spatiotemporal resolution of an in situ STM with nonequilibrium fluxes of reactive gases generated in a supersonic molecular beam to access highly activated chemical dynamics and observe the results of individual reaction events.

Correction: A computational reproducibility study of PLOS ONE articles featuring longitudinal data analyses.

[This corrects the article DOI: 10.1371/journal.pone.0251194.].

A computational reproducibility study of PLOS ONE articles featuring longitudinal data analyses.

Computational reproducibility is a corner stone for sound and credible research. Especially in complex statistical analyses-such as the analysis of longitudinal data-reproducing results is far from simple, especially if no source code is available. In this work we aimed to reproduce analyses of longitudinal data of 11 articles published in PLOS ONE. Inclusion criteria were the availability of data and author consent. We investigated the types of methods and software used and whether we were able to reproduce the data analysis using open source software. Most articles provided overview tables and simple visualisations. Generalised Estimating Equations (GEEs) were the most popular statistical models among the selected articles. Only one article used open source software and only one published part of the analysis code. Replication was difficult in most cases and required reverse engineering of results or contacting the authors. For three articles we were not able to reproduce the results, for another two only parts of them. For all but two articles we had to contact the authors to be able to reproduce the results. Our main learning is that reproducing papers is difficult if no code is supplied and leads to a high burden for those conducting the reproductions. Open data policies in journals are good, but to truly boost reproducibility we suggest adding open code policies.

First case report of SAM(r) Junctional tourniquet use in Afghanistan to control inguinal hemorrhage on the battlefield.

Junctional hemorrhage, bleeding that occurs at the junction of the trunk and its appendages, is the most common preventable cause of death from compressible hemorrhage on the battlefield. As of January 2014, four types of junctional tourniquets have been developed and cleared by the U.S. Food and Drug Administration (FDA). Successful use of the Abdominal Aortic Tourniquet (AAT™) and Combat Ready Clamp (CRoC™) has already been reported. We report here the first known prehospital use of the SAM® Junctional Tourniquet (SJT) for a battlefield casualty with inguinal junctional hemorrhage.

Pulp responses to precise thermal stimuli in dentin-sensitive teeth.

The purpose of this study was to determine whether pulpal responses to cold temperatures applied to enamel, using a method that precisely controls the intensity of the cold stimulus or measures the response time, could distinguish dentin-sensitive teeth from nonsensitive teeth. Eighteen human subjects were stimulated with cold temperatures decreasing in 5 degree C intervals (and with tetrafluoroethane) on exposed root and enamel of a dentin-sensitive tooth and enamel of a contralateral nonsensitive tooth. Pain threshold, intensity of pain, time to pain onset, and duration of pain at baseline, 4 h, 8 h, and 1 week were measured. Responses to enamel stimulation of sensitive teeth compared with the nonsensitive teeth usually were highly correlated and not significantly different. The exception was a longer duration of pain in the dentin-sensitive teeth (4.62 +/- 0.47 s) compared with nonsensitive teeth (2.92 +/- 0.49 s; p = 0.016) after enamel stimulation with tetrafluoroethane. Longitudinal studies are necessary to determine whether these slight increases in pain duration indicate an increased probability of pulpal degeneration or need for dentin protection.