Advances in Modeling of Scanning Charged-Particle-Microscopy Images

Modeling artificial scanning electron microscope (SEM) and scanning ion microscope images has recently become important. This is because of the need to provide repeatable images with a priori determined parameters. Modeled artificial images are highly useful in the evaluation of new imaging and metrological techniques, like image-sharpness calculation, or drift-corrected image composition (DCIC). Originally, the NIST-developed artificial image generator was designed only to produce the SEM images of gold-on-carbon resolution sample for image-sharpness evaluation. Since then, the new improved version of the software was written in C++ programming language and is in the Public Domain. The current version of the software can generate arbitrary samples, any drift function, and many other features. This work describes scanning in charged-particle microscopes, which is applied both in the artificial image generator and the DCIC technique. As an example, the performance of the DCIC technique is demonstrated.Comment: 9 pages, 6 figure

Speckle-scale focusing in the diffusive regime with time reversal of variance-encoded light (TROVE)

Focusing of light in the diffusive regime inside scattering media has long been considered impossible. Recently, this limitation has been overcome with time reversal of ultrasound-encoded light (TRUE), but the resolution of this approach is fundamentally limited by the large number of optical modes within the ultrasound focus. Here, we introduce a new approach, time reversal of variance-encoded light (TROVE), which demixes these spatial modes by variance encoding to break the resolution barrier imposed by the ultrasound. By encoding individual spatial modes inside the scattering sample with unique variances, we effectively uncouple the system resolution from the size of the ultrasound focus. This enables us to demonstrate optical focusing and imaging with diffuse light at an unprecedented, speckle-scale lateral resolution of ~5 µm

R2P from Below: Does the British Public View Humanitarian Interventions as Ethical and Effective?

One of the major barriers to the implementation of the Responsibility to Protect principle is the lack of a political will. Public attitudes towards intervention will have a crucial impact on elite willingness to prevent mass atrocities, yet we have little understanding of the factors that influence those attitudes. This article provides the first examination of UK public perceptions about the moral justifiability and effectiveness of humanitarian interventions. The article shows that decisions about justifiability and effectiveness are very different. Attitudes towards justification were more easily explained suggesting that judgements about effectiveness are more contextual and less easily accounted for by individuals’ background characteristics and attitudes. Experiences with both Iraq and Afghanistan have contaminated public perceptions of both the ethics and effectiveness of humanitarian interventions. Although the public is broadly supportive about the justifiability of humanitarian interventions they are extremely sceptical about the likelihood that those interventions will be successful

GPU accelerated toolbox for real-time beam-shaping in multimode fibres

TC and MP acknowledge support from the University of St Andrews, the University of Dundee and the Scottish Universities Physics Alliance (SUPA). We also thank the UK Engineering and Physical Sciences Research Council for funding. KD is a Royal Society-Wolfson Merit Award Holder. BS contributed to this work within Erasmus Student Mobility for Placement programme funded by European Commission.We present a GPU accelerated toolbox for shaping the light propagation through multimode fibre using a spatial light modulator (SLM). The light is modulated before being coupled to the proximal end of the fibre in order to achieve arbitrary light patterns at the distal end of the fibre. First, the toolbox optimises the acquisition time of the transformation matrix of the fibre by synchronous operation of CCD and SLM. Second, it uses the acquired transformation matrix retained within the GPU memory to design, in real-time, the desired holographic mask for on-the-fly modulation of the output light field. We demonstrate the functionality of the toolbox by acquiring the transformation matrix at the maximum refresh rate of the SLM -204Hz, and using it to display an on-demand oriented cube, at the distal end of the fibre. The user-controlled orientation of the cube and the corresponding holographic mask are obtained in 20ms intervals. Deleterious interference effects between the neighbouring points are eliminated by incorporating an acousto-optic deflector (AOD) into the system. We remark that the usage of the toolbox is not limited to multimode fibres and can be readily used to acquire transformation matrix and implement beam-shaping in any other linear optical system. (C)2014 Optical Society of AmericaPublisher PDFPeer reviewe

An optical nanotrap array movable over a milimetre range

We present the theoretical and experimental study of nondiffracting Bessel beams as a device for optical manipulation and confinement of nanoparticles. We express analytically the optical forces acting on a nanoparticle placed into a single and two counter-propagating non-paraxial nondiffracting beams created behind the axicon. Nanoparticle behavior in these configurations is predicted by computer simulations. Finally we demonstrate experimentally how standing waves created from two independent counter-propagating nondiffraction beams confines polystyrene beads of radii 100 nm, and organizes them into a one-dimensional chain 1 mm long. Phase shift in one beam causes the motion of the whole structure of the standing wave together with any confined objects over its extent.</p