African Higher Education: Researching Absences, Equalities and Aspirations

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Phase Transition in a Stochastic Forest Fire Model and Effects of the Definition of Neighbourhood

We present results on a stochastic forest fire model, where the influence of the neighbour trees is treated in a more realistic way than usual and the definition of neighbourhood can be tuned by an additional parameter. This model exhibits a surprisingly sharp phase transition which can be shifted by redefinition of neighbourhood. The results can also be interpreted in terms of disease-spreading and are quite unsettling from the epidemologist's point of view, since variation of one crucial parameter only by a few percent can result in the change from endemic to epidemic behaviour.Comment: 23 pages, 13 figure

An L Band Spectrum of the Coldest Brown Dwarf

The coldest brown dwarf, WISE 0855, is the closest known planetary-mass, free-floating object and has a temperature nearly as cold as the solar system gas giants. Like Jupiter, it is predicted to have an atmosphere rich in methane, water, and ammonia, with clouds of volatile ices. WISE 0855 is faint at near-infrared wavelengths and emits almost all its energy in the mid-infrared. Skemer et al. 2016 presented a spectrum of WISE 0855 from 4.5-5.1 micron (M band), revealing water vapor features. Here, we present a spectrum of WISE 0855 in L band, from 3.4-4.14 micron. We present a set of atmosphere models that include a range of compositions (metallicities and C/O ratios) and water ice clouds. Methane absorption is clearly present in the spectrum. The mid-infrared color can be better matched with a methane abundance that is depleted relative to solar abundance. We find that there is evidence for water ice clouds in the M band spectrum, and we find a lack of phosphine spectral features in both the L and M band spectra. We suggest that a deep continuum opacity source may be obscuring the near-infrared flux, possibly a deep phosphorous-bearing cloud, ammonium dihyrogen phosphate. Observations of WISE 0855 provide critical constraints for cold planetary atmospheres, bridging the temperature range between the long-studied solar system planets and accessible exoplanets. JWST will soon revolutionize our understanding of cold brown dwarfs with high-precision spectroscopy across the infrared, allowing us to study their compositions and cloud properties, and to infer their atmospheric dynamics and formation processes.Comment: 19 pages, 21 figures. Accepted for publication in Ap

On the cause and extent of outer radiation belt losses during the 30 September 2012 dropout event

Abstract On 30 September 2012, a flux dropout occurred throughout Earth\u27s outer electron radiation belt during the main phase of a strong geomagnetic storm. Using eight spacecraft from NASA\u27s Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Van Allen Probes missions and NOAA\u27s Geostationary Operational Environmental Satellites constellation, we examined the full extent and timescales of the dropout based on particle energy, equatorial pitch angle, radial distance, and species. We calculated phase space densities of relativistic electrons, in adiabatic invariant coordinates, which revealed that loss processes during the dropout were \u3e 90% effective throughout the majority of the outer belt and the plasmapause played a key role in limiting the spatial extent of the dropout. THEMIS and the Van Allen Probes observed telltale signatures of loss due to magnetopause shadowing and subsequent outward radial transport, including similar loss of energetic ring current ions. However, Van Allen Probes observations suggest that another loss process played a role for multi-MeV electrons at lower L shells (L\u3c ∼4). Key Points Dropout events can encompass the entire outer radiation belt Dropouts can result in \u3e90% losses and be a hard reset on the system Loss at L \u3e ∼4 is dominated by MP shadowing and outward transport

Primary teachers’ recommendations for the development of a teacher-oriented movement assessment tool for 4-7 year children

To inform the development of a teacher-oriented movement assessment tool, this study aimed to explore primary school teachers’ perceptions of assessing fundamental movement skills (FMS) within physical education (PE) lessons. Thirty-nine primary school teachers of PE, located in the United Kingdom, participated in an individual or group semi-structured interview. Findings signify that teachers perceive a need for an appropriate and effective movement assessment tool that is simple to use, quick to administer, and that provides valuable feedback to guide future teaching and learning. This is vital as teachers indicated that a lack of appropriate resources and a shortage of curriculum time restricts their use of assessment within PE. A movement assessment tool that aligned to the curriculum would be beneficial to teachers to better support children’s learning and acquisition of FMS, as well as to enhance the teachers’ own understanding of the process of assessing FMS

Observing Spontaneous Strong Parity Violation in Heavy-Ion Collisions

We discuss the problem of observing spontaneous parity and CP violation in collision systems. We discuss and propose observables which may be used in heavy-ion collisions to observe such violations, as well as event-by-event methods to analyze the data. Finally, we discuss simple monte-carlo models of these CP violating effects which we have used to develop our techniques and from which we derive rough estimates of sensitivities to signals which may be seen at RHIC

Observed Variability at 1um and 4um in the Y0 Brown Dwarf WISEP J173835.52+273258.9

We have monitored photometrically the Y0 brown dwarf WISEP J173835.52+273258.9 (W1738) at both near- and mid-infrared wavelengths. This ~1 Gyr-old 400K dwarf is at a distance of 8pc and has a mass around 5 M_Jupiter. We observed W1738 using two near-infrared filters at lambda~1um, Y and J, on Gemini observatory, and two mid-infrared filters at lambda~4um, [3.6] and [4.5], on the Spitzer observatory. Twenty-four hours were spent on the source by Spitzer on each of June 30 and October 30 2013 UT. Between these observations, around 5 hours were spent on the source by Gemini on each of July 17 and August 23 2013 UT. The mid-infrared light curves show significant evolution between the two observations separated by four months. We find that a double sinusoid can be fit to the [4.5] data, where one sinusoid has a period of 6.0 +/- 0.1 hours and the other a period of 3.0 +/- 0.1 hours. The near-infrared observations suggest variability with a ~3.0 hour period, although only at a <~2 sigma confidence level. We interpret our results as showing that the Y dwarf has a 6.0 +/- 0.1 hour rotation period, with one or more large-scale surface features being the source of variability. The peak-to-peak amplitude of the light curve at [4.5] is 3%. The amplitude of the near-infrared variability, if real, may be as high as 5 to 30%. Intriguingly, this size of variability and the wavelength dependence can be reproduced by atmospheric models that include patchy KCl and Na_2S clouds and associated small changes in surface temperature. The small number of large features, and the timescale for evolution of the features, is very similar to what is seen in the atmospheres of the solar system gas giants.Comment: Accepted by ApJ July 26 2016. Twenty-six pages include 8 Figures and 5 Table

Witnessing eigenstates for quantum simulation of Hamiltonian spectra

The efficient calculation of Hamiltonian spectra, a problem often intractable on classical machines, can find application in many fields, from physics to chemistry. Here, we introduce the concept of an "eigenstate witness" and through it provide a new quantum approach which combines variational methods and phase estimation to approximate eigenvalues for both ground and excited states. This protocol is experimentally verified on a programmable silicon quantum photonic chip, a mass-manufacturable platform, which embeds entangled state generation, arbitrary controlled-unitary operations, and projective measurements. Both ground and excited states are experimentally found with fidelities >99%, and their eigenvalues are estimated with 32-bits of precision. We also investigate and discuss the scalability of the approach and study its performance through numerical simulations of more complex Hamiltonians. This result shows promising progress towards quantum chemistry on quantum computers.Comment: 9 pages, 4 figures, plus Supplementary Material [New version with minor typos corrected.

QED effective action at finite temperature and density

The QED effective action at finite temperature and density is calculated to all orders in an external homogeneous and time-independent magnetic field in the weak coupling limit. The free energy, obtained explicitly, exhibit the expected de\ Haas -- van\ Alphen oscillations. An effective coupling at finite temperature and density is derived in a closed form and is compared with renormalization group results.Comment: 10 pages, Latex, NORDITA-93/35 P, Goteborg ITP 92-2

Gender, foundation degrees and the knowledge economy

This article questions the concept of ‘education for employment’, which constructs a discourse of individual and societal benefit in a knowledge‐driven economy. Recent policy emphasis in the European Union promotes the expansion of higher education and short‐cycle vocational awards such as the intermediate two‐year Foundation Degree recently introduced into England and Wales. Studies of vocational education and training (VET) and the knowledge economy have focused largely on the governance of education and on the development and drift of policy. Many VET programmes have also been considered for their classed, raced and gendered take‐up and subsequent effect on employment. This article builds on both fields of study to engage with the finer cross‐analyses of gender, social class, poverty, race and citizenship. In its analysis of policy texts the article argues that in spite of a discourse of inclusivity, an expanded higher education system has generated new inequalities, deepening social stratification. Drawing on early analyses of national quantitative data sets, it identifies emerging gendered, classed and raced patterns and considers these in relation to occupationally and hierarchically stratified labour markets, both within and without the knowledge economy