Expanded horizons for generating and exploring optical angular momentum in vortex structures

Spin provides for a well-known extension to the information capacity of nanometer-scale electronic devices. Spin transfer can be effected with high fidelity between quantum dots, this type of emission being primarily associated with emission dipoles. However, in seeking to extend the more common spectroscopic connection of dipole transitions with orbital angular momentum, it has been shown impossible to securely transmit information on any other multipolar basis – partly because point detectors are confined to polarization measurement. Standard polarization methods in optics provide for only two independent degrees of freedom, such as the circular states of opposing handedness associated with photon spin. Complex light beams with structured wave-fronts or vector polarization do, however, offer a basis for additional degrees of freedom, enabling individual photons to convey far more information content. A familiar example is afforded by Laguerre-Gaussian modes, whose helically twisted wave-front and vortex fields are associated with orbital angular momentum. Each individual photon in such a beam has been shown to carry the entire spatial helical-mode information, supporting an experimental basis for sorting beams of different angular momentum content. One very recent development is a scheme for such optical vortices to be directly generated through electronic relaxation processes in structured molecular chromophore arrays. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE)

Optical vortex mode generation by nanoarrays with a tailored geometry

Light generated with orbital angular momentum, commonly known as an optical vortex, is widely achieved by modifying the phase structure of a conventional laser beam through the utilization of a suitable optical element. In recent research, a process has been introduced that can produce electromagnetic radiation with a helical wave-front directly from a source. The chirally driven optical emission originates from a hierarchy of tailored nanoscale chromophore arrays arranged with a specific propeller-like geometry and symmetry. In particular, a nanoarray composed of n particles requires each component to be held in a configuration with a rotation and associated phase shift of 2 π/n radians with respect to its neighbor. Following initial electronic excitation, each such array is capable of supporting delocalized doubly degenerate excitons, whose azimuthal phase progression is responsible for the helical wave-front. Under identified conditions, the relaxation of the electronically-excited nanoarray produces structured light in a spontaneous manner. Nanoarrays of escalating order, i.e. those containing an increasing number of components, enable access to a set of topological charges of higher order. Practical considerations for the development of this technique are discussed, and potential new applications are identified. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE)

Hate crime victimization in Wales: psychological and physical impacts across seven hate crime victim types

This paper presents findings from the All Wales Hate Crime Project. Most hate crime research has focused on discrete victim-types in isolation. For the first time internationally this paper examines the psychological and physical impacts of hate crime across seven victim-types drawing on quantitative and qualitative data. It contributes to the hate crime debate in two significant ways: i) it provides the first look at the problem in Wales; and ii) it provides the first multi-victim-type analysis of hate crime, showing that impacts are not homogenous across victim groups. The paper provides empirical credibility to the impacts felt by hate crime victims on the margins who as Walklate (2011) and Moran (2014) argue have routinely struggled to gain support

RNA interference screening reveals host CaMK4 as a regulator of cryptococcal uptake and pathogenesis

ABSTRACT Cryptococcus neoformans , the causative agent of cryptococcosis, is an opportunistic fungal pathogen that kills over 200,000 individuals annually. This yeast may grow freely in body fluids, but it also flourishes within host cells. Despite extensive research on cryptococcal pathogenesis, host genes involved in the initial engulfment of fungi and subsequent stages of infection are woefully understudied. To address this issue, we combined short interfering RNA silencing and a high-throughput imaging assay to identify host regulators that specifically influence cryptococcal uptake. Of 868 phosphatase and kinase genes assayed, we discovered 79 whose silencing significantly affected cryptococcal engulfment. For 25 of these, the effects were fungus specific, as opposed to general alterations in phagocytosis. Four members of this group significantly and specifically altered cryptococcal uptake; one of them encoded CaMK4, a calcium/calmodulin-dependent protein kinase. Pharmacological inhibition of CaMK4 recapitulated the observed defects in phagocytosis. Furthermore, mice deficient in CaMK4 showed increased survival compared to wild-type mice upon infection with C. neoformans . This increase in survival correlated with decreased expression of pattern recognition receptors on host phagocytes known to recognize C. neoformans . Altogether, we have identified a kinase that is involved in C. neoformans internalization by host cells and in host resistance to this deadly infection. </jats:p

Towards an ethical framework for publishing Twitter data in social research: taking into account users’ views, online context and algorithmic estimation

New and emerging forms of data, including posts harvested from social media sites such as Twitter, have become part of the sociologist’s data diet. In particular, some researchers see an advantage in the perceived ‘public’ nature of Twitter posts, representing them in publications without seeking informed consent. While such practice may not be at odds with Twitter’s terms of service, we argue there is a need to interpret these through the lens of social science research methods, that imply a more reflexive ethical approach than provided in ‘legal’ accounts of the permissible use of these data in research publications. To challenge some existing practice in Twitter based research, this paper brings to the fore i) views of Twitter users through analysis of online survey data, ii) the effect of context collapse and online disinhibition on the behaviors of users, and iii) the publication of identifiable sensitive classifications derived from algorithms

Sources of Geographic Variation in Health Care: Evidence From Patient Migration

We study the drivers of geographic variation in U.S. health care utilization, using an empirical strategy that exploits migration of Medicare patients to separate the role of demand and supply factors. Our approach allows us to account for demand differences driven by both observable and unobservable patient characteristics. Within our sample of over-65 Medicare beneficiaries, we find that 40–50% of geographic variation in utilization is attributable to demand-side factors, including health and preferences, with the remainder due to place-specific supply factors.National Institute on Aging (R01-AG032449)National Institute on Aging (P01-AG19783)National Science Foundation (U.S.) (Grant 1151497)National Science Foundation (U.S.) (Grant 1260411)Neubauer Family FoundationUniversity of Chicago. Booth School of Business (Initiative on Global Markets