Non-linear optomechanical measurement of mechanical motion

Precision measurement of non-linear observables is an important goal in all facets of quantum optics. This allows measurement-based non-classical state preparation, which has been applied to great success in various physical systems, and provides a route for quantum information processing with otherwise linear interactions. In cavity optomechanics much progress has been made using linear interactions and measurement, but observation of non-linear mechanical degrees-of-freedom remains outstanding. Here we report the observation of displacement-squared thermal motion of a micro-mechanical resonator by exploiting the intrinsic non-linearity of the radiation pressure interaction. Using this measurement we generate bimodal mechanical states of motion with separations and feature sizes well below 100~pm. Future improvements to this approach will allow the preparation of quantum superposition states, which can be used to experimentally explore collapse models of the wavefunction and the potential for mechanical-resonator-based quantum information and metrology applications.Comment: 8 pages, 4 figures, extensive supplementary material available with published versio

Absolute differential positronium-formation cross sections

The first absolute experimental determinations of the differential cross-sections for the formation of ground-state positronium are presented for He, Ar, H2 and CO2 near 0○. Results are compared with available theories. The ratio of the differential and integrated cross-sections for the targets exposes the higher propensity for forward-emission of positronium formed from He and H2

History on trial: evaluating learning outcomes through audit and accreditation in a national standards environment

This paper uses a trial audit of history programs undertaken in 2011-2012 to explore issues surrounding the attainment of Threshold Learning Outcomes (TLOs) in an emerging Australian national standards environment for the discipline of history. The audit sought to ascertain whether an accreditation process managed by the discipline under the auspices of the Australian Historical Association (AHA) could be based on a limited-intervention, “light-touch” approach to assessing attainment of the TLOs. The results of the audit show that successful proof of TLO attainment would only be possible with more active intervention into existing history majors and courses. Assessments across all levels of history teaching would have to be designed, undertaken, and marked using a rubric matched to the TLOs. It proved unrealistic to expect students to demonstrate acquisition of the TLOs from existing teaching and assessment practices. The failure of the “light-touch” audit process indicates that demonstrating student attainment under a national standards regime would require fundamental redevelopment of the curriculum. With standards-based approaches to teaching and learning emerging as international phenomena, this case study resonates beyond Australia and the discipline under investigation.Sean Brawley, Jennifer Clark, Chris Dixon, Lisa Ford, Erik Nielsen, Shawn Ross, Stuart Upto

Mechanical squeezing via fast continuous measurement

We revisit quantum state preparation of an oscillator by continuous linear position measurement. Quite general analytical expressions are derived for the conditioned state of the oscillator. Remarkably, we predict that quantum squeezing is possible outside of both the backaction dominated and quantum coherent oscillation regimes, relaxing experimental requirements even compared to ground-state cooling. This provides a new way to generate non-classical states of macroscopic mechanical oscillators, and opens the door to quantum sensing and tests of quantum macroscopicity at room temperature

Resonant scattering of positronium as a quasifree electron

In order to clarify the physics underlying the observations of the electronlike behavior of positronium (Ps) and its resonant scattering from CO2, we have measured the Ps+N2 total cross section and found it also to exhibit significant structure. Analysis of the resonances reveals that Ps is distorted in the collisions and classical trajectory Monte Carlo calculations indicate that the electron is on average closer to the target than the positron, which may in turn bind resonantly to the ensuing temporary negative ion. This description of the nature of Ps resonances agrees with long-standing theoretical predictions

Complete Break Up of Ortho Positronium (Ps)- Hydrogenic ion System

The dynamics of the complete breakup process in an Ortho Ps - He+ system including electron loss to the continuum (ELC) is studied where both the projectile and the target get ionized. The process is essentially a four body problem and the present model takes account of the two centre effect on the electron ejected from the Ps atom which is crucial for a proper description of the ELC phenomena. The calculations are performed in the framework of Coulomb Distorted Eikonal Approximation. The exchange effect between the target and the projectile electron is taken into account in a consistent manner. The proper asymptotic 3-body boundary condition for this ionization process is also satisfied in the present model. A distinct broad ELC peak is noted in the fully differential cross sections (5DCS) for the Ps electron corroborating qualitatively the experiment for the Ps - He system. Both the dynamics of the ELC from the Ps and the ejected electron from the target He+ in the FDCS are studied using coplanar geometry. Interesting features are noted in the FDCS for both the electrons belonging to the target and the projectile.Comment: 14 pages,7 figure

The Effects of Ketone Supplementation on Recovery in Collegiate Male Soccer Players: Pilot Trial

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Algae as nutritional and functional food sources: revisiting our understanding.

Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.AGS & KEH thank the Biotechnology and Biological Sciences Research Council (BBSRC BB/1013164/1) of the UK for funding. The University of Dundee is a registered Scottish charity, No. SC015096. PP is supported by IDEALG in the frame of the stimuli program entitled “Investissements d’avenir, Biotechnologies-Bioressources” (ANR-10-BTBR-04-02). The open access fee was supported by NSF-OCE-1435021 (MLW), DIC project 1823-06 (MEC), Maine Sea Grant (NOAA) 5405971 (SHB), NSF #11A-1355457 to Maine EPSCoR at the University of Maine (SHB), and the listed funding to AGS and PP