Achieving the Theoretical Depairing Current Limit in Superconducting Nanomesh Films

We show the theoretical depairing current limit can be achieved in a robust fashion in highly ordered superconductor nanomesh films having spatial periodicities smaller than both the superconducting coherence length and the magnetic penetration depth. For a niobium nanomesh film with 34 nm spatial periodicity, the experimental critical current density is enhanced by more than 17 times over the continuous film and is in good agreement with the depairing limit over the entire measured temperature range. The nanomesh superconductors are also less susceptible to thermal fluctuations when compared to nanowire superconductors. T_c values similar to the bulk film are achieved, and the nanomeshes are capable of retaining superconductivity to higher fields relative to the bulk. In addition, periodic oscillations in T_c are observed as a function of field, reflecting the highly ordered nanomesh structure

Scanning Tunneling Microscopy Characterization of the Electrical Properties of Wrinkles in Exfoliated Graphene Monolayers

We report on the scanning tunneling microscopy study of a new class of corrugations in exfoliated monolayer graphene sheets, that is, wrinkles ~10 nm in width and ~3 nm in height. We found such corrugations to be ubiquitous in graphene and have distinctly different properties when compared to other regions of graphene. In particular, a “three-for-six” triangular pattern of atoms is exclusively and consistently observed on wrinkles, suggesting the local curvature of the wrinkle provides a sufficient perturbation to break the 6-fold symmetry of the graphene lattice. Through scanning tunneling spectroscopy, we further demonstrate that the wrinkles have lower electrical conductance and are characterized by the presence of midgap states, which is in agreement with recent theoretical predictions. The observed wrinkles are likely important for understanding the electrical properties of graphene

The Microscopic Structure of Adsorbed Water on Hydrophobic Surfaces under Ambient Conditions

The interaction of water vapor with hydrophobic surfaces is poorly understood. We utilize graphene templating to preserve and visualize the microscopic structures of adsorbed water on hydrophobic surfaces. Three well-defined surfaces [H–Si(111), graphite, and functionalized mica] were investigated, and water was found to adsorb as nanodroplets (~10–100 nm in size) on all three surfaces under ambient conditions. The adsorbed nanodroplets were closely associated with atomic-scale surface defects and step-edges and wetted all the hydrophobic substrates with contact angles < ~10°, resulting in total water adsorption that was similar to what is found for hydrophilic surfaces. These results point to the significant differences between surface processes at the atomic/nanometer scales and in the macroscopic world

Time and time again: unisexual salamanders (genus Ambystoma) are the oldest unisexual vertebrates

<p>Abstract</p> <p>Background</p> <p>The age of unisexual salamanders of the genus <it>Ambystoma </it>is contentious. Recent and ancient evolutionary histories of unisexual <it>Ambystoma </it>were proposed by a few separate studies that constructed phylogenies using mitochondrial DNA markers (cytochrome b gene vs. non-coding region). In contrast to other studies showing that unisexual <it>Ambystoma </it>represent the most ancient unisexual vertebrates, a recent study by Robertson et al. suggests that this lineage has a very recent origin of less than 25,000 years ago.</p> <p>Results</p> <p>We re-examined the phylogenetic relationship of the unisexuals to <it>A. barbouri </it>from various populations using both mitochondrial markers as well as the complete mitochondrial genomes of <it>A. barbouri </it>and a unisexual individual from Kentucky. Lineage dating was conducted using BEAST and MultiDivTime on a complete mitochondrial genome phylogeny. Our results support a monophyletic lineage for unisexual <it>Ambystoma </it>that shares its most recent common ancestor with an <it>A. barbouri </it>lineage from western Kentucky. In contrast to the Robertson et al.'s study, no <it>A. barbouri </it>individual shared an identical or almost identical cytochrome b haplotype with any unisexual. Molecular dating supports an early Pliocene origin for the unisexual linage (~5 million years ago). We propose that a unisexual-like cytochrome b <it>numt </it>(or pseudogene) exists in the controversial <it>A. barbouri </it>individuals from Kentucky, which was likely the cause of an erroneous phylogeny and time estimate in Robertson et al.'s study.</p> <p>Conclusion</p> <p>We reject a recent origin of unisexual <it>Ambystoma </it>and provide strong evidence that unisexual <it>Ambystoma </it>are the most ancient unisexual vertebrates known to exist. The likely presence of an ancient cytochrome b <it>numt </it>in some Kentucky <it>A. barbouri </it>represents a molecular "fossil" reinforcing the hypothesis that these individuals are some of the closest extant relatives to unisexual <it>Ambystoma</it>.</p

Comparing leadership internationally: challenges and reflections

This paper is a co-written paper by five MA Education students at the University of Northampton and James Underwood, Principal Lecturer at the University of Northampton and a PhD student at the University of Cambridge. We are all currently engaged in research that involves comparing aspects of education in the UK with another nation. The research that we are each personally undertaking addresses a range of topics. These all relate to an aspect of education leadership ranging from student leadership to school and university management. There is one common underlying research question which underpins all the studies which is: in what ways has comparison between nations been a valid approach to understanding education and leadership? This question is addressed successively via our individual stories in this paper. This paper is linked to a paper presented in May 2015 at the University of Cambridge entitled: “Breaking boundaries as writers, researchers and me-searchers, the challenges and rewards of completing an MA as a community of practice.” In which we discussed in depth our experience as a research community. This paper has therefore also been informed by a distinct perspective on the nature of Masters’ level study

Graphene Visualizes the First Water Adlayers on Mica at Ambient Conditions

The dynamic nature of the first water adlayers on solid surfaces at room temperature has made the direct detection of their microscopic structure challenging. We used graphene as an atomically flat coating for atomic force microscopy to determine the structure of the water adlayers on mica at room temperature as a function of relative humidity. Water adlayers grew epitaxially on the mica substrate in a layer-by-layer fashion. Submonolayers form atomically flat, faceted islands of height 0.37 ± 0.02 nanometers, in agreement with the height of a monolayer of ice. The second adlayers, observed at higher relative humidity, also appear icelike, and thicker layers appear liquidlike. Our results also indicate nanometer-scale surface defects serve as nucleation centers for the formation of both the first and the second adlayers