27 research outputs found
Structural and magnetic properties of Fe/ZnSe(001) interfaces
We have performed first principles electronic structure calculations to
investigate the structural and magnetic properties of Fe/ZnSe(001) interfaces.
Calculations involving full geometry optimizations have been carried out for a
broad range of thickness of Fe layers(0.5 monolayer to 10 monolayers) on top of
a ZnSe(001) substrate. Both Zn and Se terminated interfaces have been explored.
Total energy calculations show that Se segregates at the surface which is in
agreement with recent experiments.
For both Zn and Se terminations, the interface Fe magnetic moments are higher
than the bulk bcc Fe moment.
We have also investigated the effect of adding Fe atoms on top of a
reconstructed ZnSe surface to explore the role of reconstruction of
semiconductor surfaces in determining properties of metal-semiconductor
interfaces. Fe breaks the Se dimer bond formed for a Se-rich (2x1)
reconstructed surface. Finally, we looked at the reverse growth i.e. growth of
Zn and Se atoms on a bcc Fe(001) substrate to investigate the properties of the
second interface of a magnetotunnel junction. The results are in good agreement
with the theoretical and experimental results, wherever available.Comment: 7 pages, 8 figures, accepted for publication in PR
Moderate drinking before the unit: medicine and life assurance in Britain and the US c.1860â1930
This article describes the way in which âAnstieâs Limitâ â a particular definition of moderate drinking first defined in Britain in the 1860s by the physician Francis Edmund Anstie (1833â1874) â became established as a useful measure of moderate alcohol consumption. Becoming fairly well-established in mainstream Anglophone medicine by 1900, it was also communicated to the public in Britain, North America and New Zealand through newspaper reports. However, the limit also travelled to less familiar places, including life assurance offices, where a number of different strategies for separating moderate from excessive drinkers emerged from the dialogue between medicine and life assurance. Whilst these ideas of moderation seem to have disappeared into the background for much of the twentieth century, re-emerging as the âJ-shapedâ curve, these early developments anticipate many of the questions surrounding uses of the âunitâ to quantify moderate alcohol consumption in Britain today. The article will therefore conclude by exploring some of the lessons of this story for contemporary discussions of moderation, suggesting that we should pay more attention to whether these metrics work, where they work and why
Surface magnetism in iron, cobalt, and nickel
We have calculated magnetic moments, work functions, and surface energies for several of the most closely packed surfaces of iron, cobalt, and nickel by means of a spin-polarized Greenâs-function technique based on the linear muffin-tin orbitals method within the tight-binding and atomic sphere approximations. We find enhanced spin moments at all the surfaces considered except for Ni fcc(111), where the moment at the surface reverts to its bulk value. This is in close agreement with earlier slab calculations. In addition, we find that the calculated work functions and surface energies agree with experimental values to within 10%, which may be considered most satisfactory in view of the computational efficiency of the Greenâs function technique. Exchange and correlation have been treated wihtin the local spin-density approximation and we have considered three different parametrizations of the original many-body data. We find that the calculated work functions depend as much on the choice of this parametrization as on the effect of spin polarization
Effect of fat and CHO meals on intermittent exercise in soccer players
Pre-exercise meals containing carbohydrates (CHO) are recommended to athletes, although there is evidence to suggest that a high fat meal prior to exercise increases utilisation of fats yet may not adversely affect performance. This study investigated the effect of a high fat and high CHO pre-exercise meal prior to high intensity intermittent exercise. Ten male recreational soccer players performed a soccer specific protocol followed by a 1km time trial 3 h after ingesting one of 2 test meals, high fat meal (HFM) or a high CHO meal (HCM). Blood glucose, fatty acids (FA), glycerol, ÎČ-hydroxybutyrate, lactate and insulin were assessed prior to the meal, pre-exercise, half-time, and post-exercise, whilst rates of CHO and fat oxidation were determined at 4 time points during the exercise as well as heart rate (HR) and rating of perceived exertion (RPE). Significant increases in FA, glycerol, ĂÂČ-hydroxybutyrate and fat oxidation after the HFM were observed, while CHO oxidation was significantly higher following the HCM (P<0.05). No performance effect was found for the 1km time trial (HFM: 228.6+14.4s; HCM: 229.4+26.5s) (mean+SD). These findings suggest that the type of meal ingested prior to soccer simulated exercise has an impact on metabolism, but not on the subsequent performance as determined in the present study