Wavelength Tunability of Ion-bombardment Induced Ripples on Sapphire

A study of ripple formation on sapphire surfaces by 300-2000 eV Ar+ ion bombardment is presented. Surface characterization by in-situ synchrotron grazing incidence small angle x-ray scattering and ex-situ atomic force microscopy is performed in order to study the wavelength of ripples formed on sapphire (0001) surfaces. We find that the wavelength can be varied over a remarkably wide range-nearly two orders of magnitude-by changing the ion incidence angle. Within the linear theory regime, the ion induced viscous flow smoothing mechanism explains the general trends of the ripple wavelength at low temperature and incidence angles larger than 30. In this model, relaxation is confined to a few-nm thick damaged surface layer. The behavior at high temperature suggests relaxation by surface diffusion. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface diffusion or viscous flow relaxation.Comment: Revtex4, 19 pages, 10 figures with JPEG forma

Dimethyl fumarate in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Dimethyl fumarate (DMF) inhibits inflammasome-mediated inflammation and has been proposed as a treatment for patients hospitalised with COVID-19. This randomised, controlled, open-label platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing multiple treatments in patients hospitalised for COVID-19 (NCT04381936, ISRCTN50189673). In this assessment of DMF performed at 27 UK hospitals, adults were randomly allocated (1:1) to either usual standard of care alone or usual standard of care plus DMF. The primary outcome was clinical status on day 5 measured on a seven-point ordinal scale. Secondary outcomes were time to sustained improvement in clinical status, time to discharge, day 5 peripheral blood oxygenation, day 5 C-reactive protein, and improvement in day 10 clinical status. Between 2 March 2021 and 18 November 2021, 713 patients were enroled in the DMF evaluation, of whom 356 were randomly allocated to receive usual care plus DMF, and 357 to usual care alone. 95% of patients received corticosteroids as part of routine care. There was no evidence of a beneficial effect of DMF on clinical status at day 5 (common odds ratio of unfavourable outcome 1.12; 95% CI 0.86-1.47; p = 0.40). There was no significant effect of DMF on any secondary outcome

Performance of an x‐ray optical time delay line with synchrotron radiation

We describe pump‐probe experiments in the x‐ray region using synchrotron radiation to supply both the pump and probe beams. The time between pump and probe is adjustable on the nanosecond time scale by means of an optical delay line operating in the x‐ray region. With the ‘‘third generation’’ sources presently under construction around the world it should be practicable to study optical excitations using similar techniques to those described here. The initial studies we describe were carried out at the National Synchrotron Light Source. A 30‐μm‐thick silicon [110] crystal was irradiated by white light from a bending magnet. The radiation passing through this sample was monochromated by two silicon [660] reflections in such a way that the monochromatic beam was directed onto the first surface of the thin crystal sample. The surface of this thin crystal was probed by recording the symmetric (220) reflexion 2.78 ns after illumination by the white beam. Techniques for overcoming the background problem resulting from scattering of the white beam by the sample crystal are discussed

Fast X-ray microfluorescence imaging with submicrometer-resolution integrating a Maia detector at beamline P06 at PETRA III

The high brilliance of third-generation synchrotron sources increases thedemand for faster detectors to utilize the available flux. The Maia detector is anadvanced imaging scheme for energy-dispersive detection realising dwell timesper image-pixel as low as 50 ms and count rates higher than 10 106 s1. In thisarticle the integration of such a Maia detector in the Microprobe setup ofbeamline P06 at the storage ring PETRA III at the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany, is described. The analyticalperformance of the complete system in terms of rate-dependent energyresolution, scanning-speed-dependent spatial resolution and lower limits ofdetection is characterized. The potential of the Maia-based setup is demonstratedby key applications from materials science and chemistry, as well asenvironmental science with geological applications and biological questions thathave been investigated at the P06 beamline

First experimental feasibility study of VIPIC: a custom-made detector for X-ray speckle measurements

exterior, view of the north elevation, from the Loire Rive