Long-range interactions in a quantum gas mediated by diffracted light

A BEC interacting with an optical field via a feedback mirror can be a realisation of the quantum Hamiltonian Mean Field (HMF) model, a paradigmatic model of long-range interactions in quantum systems. We demonstrate that the self-structuring instability displayed by an initially uniform BEC can evolve as predicted by the quantum HMF model, displaying quasiperiodic "chevron" dynamics for strong driving. For weakly driven self-structuring, the BEC and optical field behave as a two-state quantum system, regularly oscillating between a spatially uniform state and a spatially periodic state. It also predicts the width of stable optomechanical droplets and the dependence of droplet width on optical pump intensity. The results presented suggest that optical diffraction-mediated interactions between atoms in a BEC may be a route to experimental realisation of quantum HMF dynamics and a useful analogue for studying quantum systems involving long-range interactions

Role of Oxygen Defects on the Magnetic Properties of Ultra-Small Sn\u3csub\u3e1−x\u3c/sub\u3eFe\u3csub\u3ex\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e Nanoparticles

Although the role of oxygen defects in the magnetism of metal oxide semiconductors has been widely discussed, it is been difficult to directly measure the oxygen defect concentration of samples to verify this. This work demonstrates a direct correlation between the photocatalytic activity of Sn1−xFexO2 nanoparticles and their magnetic properties. For this, a series of ~2.6 nm sized, well characterized, single-phase Sn1−xFexO2 crystallites with x = 0−0.20 were synthesized using tin acetate, urea, and appropriate amounts of iron acetate. X-ray photoelectron spectroscopy confirmed the concentration and 3+ oxidation state of the doped Fe ions. The maximum magnetic moment/Fe ion, μ, of 1.6 × 10−4 μB observed for the 0.1% Fe doped sample is smaller than the expected spin-only contribution from either high or low spin Fe3+ ions, and μ decreases with increasing Fe concentration. This behavior cannot be explained by the existing models of magnetic exchange. Photocatalytic studies of pure and Fe-doped SnO2 were used to understand the roles of doped Fe3+ ions and of the oxygen vacancies and defects. The photocatalytic rate constant k also showed an increase when SnO2 nanoparticles were doped with low concentrations of Fe3+, reaching a maximum at 0.1% Fe, followed by a rapid decrease of k for further increase in Fe%. Fe doping presumably increases the concentration of oxygen vacancies, and both Fe3+ ions and oxygen vacancies act as electron acceptors to reduce e−-h+ recombination and promote transfer of electrons (and/or holes) to the nanoparticle surface, where they participate in redox reactions. This electron transfer from the Fe3+ ions to local defect density of states at the nanoparticle surface could develop a magnetic moment at the surface states and leads to spontaneous ferromagnetic ordering of the surface shell under favorable conditions. However, at higher doping levels, the same Fe3+ ions might act as recombination centers causing a decrease of both k and magnetic moment μ

From funding gaps to thin markets: UK Government support for early-stage venture capital

Research report'Hybrid' venture capital schemes backed by both private and public sector funding play an increasingly important role in the risk capital funding of early-stage firms with the potential for significant growth. We analysed the impact of investment from six UK government-backed venture capital schemes on 782 funded firms over the period 1995-2008. The six schemes that are the focus of this analysis are the Enterprise Capital Funds (ECFs), Early Growth Funds (EGFs), Regional Venture Capital Funds (RVCFs), Scottish Enterprise-backed Funds, University Challenge Funds (UCFs), and Welsh Hybrid Funds

A social pedagogical intervention to support children in care:Back on Track

This paper focuses on an intervention project, Back on Track (BoT), implemented as a part of the Resilience Revolution: HeadStart Blackpool (RR:HS) programme in the UK. Whilst it is a famous family holiday resort, Blackpool is also one of the most deprived towns in England. This makes life challenging for young people (YP) to maintain wellbeing and reach their potential. Blackpool also has an above average and growing proportion of children in care. They are at a higher risk of developing mental health difficulties and of being permanently excluded from school. BoT aimed to support fostered children who have been referred by schools or social workers to the project for having emotional and behavioural struggles. As a consequence of their difficulties, they were at risk of permanent exclusion from the school. The intervention was grounded in a social pedagogical approach and Resilient Therapy. Resilience Coaches (i.e., wellbeing practitioners) had the role of enhancing communication between YP, family, social care, and school, whilst working with YP to co-produce coping strategies. Between November 2016 and June 2021, 39 YP (61.5% male) aged 10 to 15 (M = 12.74, SD = 1.60) received BoT support over a period lasting between 4 months to 2.5 years (M = 14 months, SD = 6.8 months). Using a mixed-methods design, this paper explored the BoT implementation. YP completed questionnaires before and after BoT. Triangulation interviews were conducted with a randomly selected YP, foster parent and the Resilience Coach. Results showed the benefit of equipping YP with ‘resilient moves’ and joining up systems to work together and better support YP and families. YP reported reduced difficulties, improved strengths (i.e., prosocial behaviour) and educational outcomes. This helped build resilience and reduce the risk of permanent exclusions from school. Policy and practice implications for children in care are discussed

Continuous acceleration sensing using optomechanical droplets

We show that a Bose–Einstein Condensate illuminated by a far off-resonant optical pump field and its retroreflection from a feedback mirror can produce stable, localised structures known as optomechanical droplets. We show that these droplets could be used to measure the acceleration of a BEC via continuous monitoring of the position of the droplet via the optical intensity distribution

East Atlanta

Prepared by the Spring 2017 Case Studies in Historic Preservation students. Located partially in the City of Atlanta, DeKalb County and in unincorporated DeKalb County. East Atlanta is a good example of an evolving suburb. In the late 19th and early 20th century the area was an urban neighborhood that relied on the streetcar system and by World War II had evolved into an automobile-reliant suburban. Development progressed from a densely, gridded street pattern in the northern portion indicating a traditional urban neighborhood to a curvilinear street pattern in the southern section indicating an automobile-centric suburb. The area includes at least three commercial nodes, a variety of historic houses and community and commercial buildings, a cemetery, a park, a Civil War monument, and five state historic markers.https://scholarworks.gsu.edu/history_heritagepreservation/1048/thumbnail.jp