C60 adsorption on an aperiodically modulated Cu surface

Copper deposited on the ve-fold surface of icosahedral Al-Pd-Mn forms domains of a structure whose surface has a one-dimensional aperiodic modulation. It is shown that C60 deposited on this aperiodic film has highly reduced mobility as compared to C60 deposited on periodic Cu surfaces. This fnding is explained in terms of the recently proposed structural model of this system

Analysis of a novel non-contacting waveguide backshort

A new non-contacting waveguide backshort has been developed for millimeter and submillimeter wave frequencies. The design consists of a metal bar with rectangular or circular holes cut into it, which is covered with a dielectric (mylar) layer to form a snug fit with the walls of a waveguide. Hole geometries are adjusted to obtain a periodic variation of the guide impedance on the correct length scale, in order to produce efficient reflection of RF power. It is a mechanically rugged design which can be easily fabricated for frequencies from 1 to 1000 GHz and is thus a sound alternative to the miniaturization of conventional non-contacting shorts. To aid in high-frequency design, a rigorous full-wave analysis has been completed, which will allow variations of the size, number and spacing of the holes to be easily analyzed. This paper will review the backshort design and the method developed for theoretical characterization, followed by a comparison of the experimental and numerical results. Low frequency models operating from 4-6 GHz are shown to demonstrate return loss of greater than -0.2 dB over a 33 percent bandwidth. The theory is in good agreement with measured data

Nucleation and growth of a quasicrystalline monolayer: Bi adsorption on the five-fold surface of i-Al70Pd21Mn9

Scanning tunnelling microscopy has been used to study the formation of a Bi monolayer deposited on the five-fold surface of i-Al70Pd21Mn9. Upon deposition of low sub-monolayer coverages, the nucleation of pentagonal clusters of Bi adatoms of edge length 4.9 A is observed. The clusters have a common orientation leading to a film with five-fold symmetry. By inspection of images where both the underlying surface and the Bi atoms are resolved, the pentagonal clusters are found to nucleate on pseudo-Mackay clusters truncated such that a Mn atom lies centrally in the surface plane. The density of these sites is sufficient to form a quasiperiodic framework, and subsequent adsorption of Bi atoms ultimately leads to the formation of a quasicrystalline monolayer. The initial nucleation site is different to that proposed on the basis of recent density functional theory calculations.Comment: 6 pages, 5 figure

Data Resource: The National Pupil Database (NPD)

Introduction: The National Pupil Database (NPD) is a record-level administrative data resource curated by the UK government's Department for Education that is used for funding purposes, school performance tables, policy making, and research. Processes Data are sourced from schools, exam awarding bodies, and local authorities who collect data on an on-going basis and submit to the Department for Education either termly or yearly. Data contents NPD contains child-level and school-level data on all pupils in state schools in England (6.6 million in the 2016/17 academic year). The primary module is the census, which has information on characteristics and school enrolment. Other modules include alternative provision, exam attainment, absence and exclusions. Data from children's social care are also available on children referred for support and those who become looked after. Children's records are linkable across different modules and across time using a nationally unique, anonymised child-level identifier. Linkage to external datasets has also been accomplished using child-level identifiers. Conclusions The NPD is an especially valuable data resource for researchers interested in the educational experience and outcomes of children and young people in England. Although limited by the fact that children in private schools or who are home schooled are not included, it provides a near-complete picture of school trajectories and outcomes for the majority of children. Linkage to other datasets can enhance analyses and provide answers to questions that would otherwise be costly, time consuming and difficult to find

Formation of a quasicrystalline Pb monolayer on the ten-fold surface of the decagonal Al-Ni-Co quasicrystal

Lead has been deposited on the ten-fold surface of decagonal Al72Ni11Co17 to form an epitaxial quasicrystalline single-element monolayer. The overlayer grows through nucleation of nanometer-sized irregular islands and the coverage saturates at 1 ML. The overlayer is well-ordered quasiperiodically as evidenced by LEED and Fourier transforms of STM images. Annealing the film to 600 K improves the structural quality, but causes the evaporation of some material such that the film develops pores. Electronic structure measurements using X-ray photoemission spectroscopy indicate that the chemical interaction of the Pb atoms with the substrate is weak.Comment: 12 pages, 5 figure

Extended performance solar electric propulsion thrust system study. Volume 4: Thruster technology evaluation

Several thrust system design concepts were evaluated and compared using the specifications of the most advanced 30 cm engineering model thruster as the technology base. Emphasis was placed on relatively high power missions (60 to 100 kW) such as a Halley's comet rendezvous. The extensions in thruster performance required for the Halley's comet mission were defined and alternative thrust system concepts were designed in sufficient detail for comparing mass, efficiency, reliability, structure, and thermal characteristics. Confirmation testing and analysis of thruster and power processing components were performed, and the feasibility of satisfying extended performance requirements was verified. A baseline design was selected from the alternatives considered, and the design analysis and documentation were refined. The baseline thrust system design features modular construction, conventional power processing, and a concentrator solar array concept and is designed to interface with the Space Shuttle

The surface science of quasicrystals

The surfaces of quasicrystals have been extensively studied since about 1990. In this paper we review work on the structure and morphology of clean surfaces, and their electronic and phonon structure. We also describe progress in adsorption and epitaxy studies. The paper is illustrated throughout with examples from the literature. We offer some reflections on the wider impact of this body of work and anticipate areas for future development. (Some figures in this article are in colour only in the electronic version

Rethinking the employability of international graduate migrants: reflections on the experiences of Zimbabweans with degrees from England

The last decade has seen the rise of literatures that have focused on the rapid expansion of the numbers of international students in higher education globally and the growing policy discourse around improving graduate employability. However, both, inevitably, have limitations. Together, they tend to homogenise international learners and see them narrowly as simply economic actors. More recently, however, there have been signs of important new developments in both literatures, drawing on interactive employability and capability accounts that stress both agency and structure in more satisfactory ways. We seek to further the development of an account that bridges the new wave of student mobility research and the capability-employability account. In doing so, we offer two further elements to the literature. First, we aim to bridge the gap between international higher education accounts and those of migration and diasporic studies. Second, we deliberately focus on a group that is marginal to the mainstream discourse but who are migrants that have engaged in international higher education in order to improve their labour market prospects, amongst other motivations. We do this through examining the stories of five Zimbabweans who embarked on additional higher educational studies in England after migrating to the country. Through this unique approach, we offer an important new perspective on how the debates on international higher education, employability and migration can be taken forward through closer articulation between these accounts

The Assembly of the Red Sequence at z ~ 1: The Color and Spectral Properties of Galaxies in the Cl1604 Supercluster

We investigate the properties of the 525 spectroscopically confirmed members of the Cl1604 supercluster at z ~ 0.9 as part of the Observations of Redshift Evolution in Large Scale Environments survey. In particular, we focus on the photometric, stellar mass, morphological, and spectral properties of the 305 member galaxies of the eight clusters and groups that comprise the Cl1604 supercluster. Using an extensive Keck Low-Resolution Imaging Spectrometer (LRIS)/DEep Imaging Multi-Object Spectrograph (DEIMOS) spectroscopic database in conjunction with ten-band ground-based, Spitzer, and Hubble Space Telescope imaging, we investigate the buildup of the red sequence in groups and clusters at high redshift. Nearly all of the brightest and most massive red-sequence galaxies present in the supercluster environment are found to lie within the bounds of the cluster and group systems, with a surprisingly large number of such galaxies present in low-mass group systems. Despite the prevalence of these red-sequence galaxies, we find that the average cluster galaxy has a spectrum indicative of a star-forming galaxy, with a star formation rate between those of z ~ 1 field galaxies and moderate-redshift cluster galaxies. The average group galaxy is even more active, exhibiting spectral properties indicative of a starburst. The presence of massive, red galaxies and the high fraction of starbursting galaxies present in the group environment suggest that significant processing is occurring in group environments at z ~ 1 and earlier. There is a deficit of low-luminosity red-sequence galaxies in all Cl1604 clusters and groups, suggesting that such galaxies transition to the red sequence at later times. Extremely massive (~10^(12)M_☉) red-sequence galaxies routinely observed in rich clusters at z ~ 0 are also absent from the Cl1604 clusters and groups. We suggest that such galaxies form at later times through merging processes. There are significant populations of transition galaxies at intermediate stellar masses (log(M_*)=10.25-10.75) present in the group and cluster environments, suggesting that this range is important for the buildup of the red-sequence mass function at z ~ 1. Through a comparison of the transitional populations present in the Cl1604 cluster and group systems, we find evidence that massive blue-cloud galaxies are quenched earliest in the most dynamically relaxed systems and at progressively later times in dynamically unrelaxed systems