Undergraduate mathematics diversified for non-standard entrants - whatever next! A case of teaching assistants and the curriculum

This paper draws upon data from a longitudinal study of the first cohort of five students making the transition from teaching assistant in secondary school to specialist teacher of secondary mathematics via a new full-time honours degree in Mathematics Education Studies beginning in September 2002. Data from a second cohort of four women and one man starting in 2003 is less complete, but used as appropriate. To complete the degree each student must necessarily continue to work as a teaching assistant, and must complete some assessed work in their school setting. The study is thus located within theorised literature of widening participation, student choice, and learning mathematics. It is timely in view of government policy of a �remodelled school workforce� (DfES, 2004) whereby the stated intention is to complement a reduced cadre of qualified teachers with an enhanced number of staff supporting teaching and learning. I argue, using Bernstein�s work (1996) on subject classification, this student group represents a different type of learner, navigating simultaneously two mathematics discourses: �hard� university mathematics, and �everyday mathematics� as experienced by the lower ability school pupils that the students support when at work. Widening participation rhetoric focuses on enticing people into learning who would not otherwise be there (Hillage and Aston, 2001). This account relates to people who, despite being unqualified are already in educational institutions, i.e. schools, through their work. These are people who are �pre-disposed� favourably towards higher education (see for example Billet, 2001), and for whom progression is what is desired. The students have undergone a long, and autodidactical preparation for university study, illustrated in a variety of ways through previous personal and professional engagement with learning. The first group were aged between 35 - 49 on entry to the university, and all working as teaching assistants in three schools, two in each of two schools, and one in a third. None had higher than Grade B Intermediate GCSE in mathematics, but all had qualifications gained through continuing education as adults: in counselling, embroidery, art, design, numeracy, literacy and computer qualifications between them. In comparison with �traditional� mathematics undergraduates1, i.e. higher than average A-level points scores on entry, and mainly following on straight from school, the first group of students have extremely limited mathematics qualifications. None has any parents, brothers or sisters that had attended university, and only one has graduates in her immediate family: her husband and daughter. In terms of national data on student populations as a whole (UCAS, Labour Force Survey, Office for National Statistics, 2004) this group is older than almost three-quarters of the undergraduate population and in a lower social class than half of them. The second group show some differences from the first, not in so far as their mathematics qualifications, but in the fact that two of them are already graduates of other subjects. Nevertheless, students are progressing through the programme, between them achieving the full range of marks, and, unlike traditional mathematics students, so far there has been no drop-out. These students exemplify a different type of mathematics learner, those for who mathematics has never been easy, have never been recognised as talented, and who have developed as a consequence successful strategies for dealing with the practically inevitable difficulties. They are people with specific graduate professional ambitions entering the academy with low level formal mathematics qualifications. These distinctions are forcing a rethink of what success in mathematics means, what may be useful pre-requisites in terms of pre-qualification, and the potential relationship between university learning of mathematics alongside work-place learning, in this case in a secondary school mathematics department

Bare quark stars or naked neutron stars? The case of RX J1856.5-3754

In a cool neutron star (T less than or similar to 10(6) K) endowed with a rather highmagnetic field (B greater than or similar to 10(13) G), a phase transition may occur in the outermost layers. As a consequence, the neutron star becomes "bare,'' i.e., no gaseous atmosphere sits on the top of the crust. The surface of a cooling, bare neutron star does not necessarily emit a blackbody spectrum because the emissivity is strongly suppressed at energies below the electron plasma frequency, omega(p). Since omega(p) approximate to 1 keV under the conditions typical of the dense electron gas in the condensate, the emission from a T similar to 100 eV bare neutron star will be substantially depressed with respect to that of a perfect Planckian radiator atmost energies. Here we present a detailed analysis of the emission properties of a bare neutron star. In particular, we derive the surface emissivity for an Fe composition in a range of magnetic fields and temperatures representative of cooling isolated neutron stars, like RX J1856.5 - 3754. We find that the emitted spectrum is strongly dependent on the electron conductivity in the solid surface layers. In the cold electron gas approximation ( no electron-lattice interactions), the spectrum turns out to be a featureless depressed blackbody in the 0.1 - 2 keV band with a steeper low-energy distribution. When damping effects due to collisions between electrons and the ion lattice ( mainly due to electron-phonon interactions) are accounted for, the spectrum is more depressed at low energies and spectral features may be present, depending on the magnetic field strength. Details of the emitted spectrum are found, however, to be strongly dependent on the assumed treatment of the transition from the external vacuum to the metallic surface. The implications of our results for RX J1856.5 - 3754 and other isolated neutron stars are discussed

Origin of asymmetries in X-ray emission lines from the blast wave of the 2014 outburst of nova V745 Sco

The symbiotic nova V745 Sco was observed in outburst on 2014 February 6. Its observations by the Chandra X-ray Observatory at days 16 and 17 have revealed a spectrum characterized by asymmetric and blue-shifted emission lines. Here we investigate the origin of these asymmetries through three-dimensional hydrodynamic simulations describing the outburst during the first 20 days of evolution. The model takes into account thermal conduction and radiative cooling and assumes a blast wave propagates through an equatorial density enhancement. From the simulations, we synthesize the X-ray emission and derive the spectra as they would be observed with Chandra. We find that both the blast wave and the ejecta distribution are efficiently collimated in polar directions due to the presence of the equatorial density enhancement. The majority of the X-ray emission originates from the interaction of the blast with the equatorial density enhancement and is concentrated on the equatorial plane as a ring-like structure. Our "best-fit" model requires a mass of ejecta in the outburst $M_{ej} \approx 3\times 10^{-7}\,M_{\odot}$ and an explosion energy $E_b \approx 3 \times 10^{43}$ erg and reproduces the distribution of emission measure vs temperature and the evolution of shock velocity and temperature inferred from the observations. The model predicts asymmetric and blue-shifted line profiles similar to those observed and explains their origin as due to substantial X-ray absorption of red-shifted emission by ejecta material. The comparison of predicted and observed Ne and O spectral line ratios reveals no signs of strong Ne enhancement and suggests the progenitor is a CO white dwarf.Comment: 16 pages, 17 Figures; accepted for publication on MNRA

X-raying the coronae of HD~155555

We present an analysis of the high-resolution Chandra observation of the multiple system, HD 155555 (an RS CVn type binary system, HD 155555 AB, and its spatially resolved low-mass companion HD 155555 C). This is an intriguing system which shows properties of both an active pre-main sequence star and a synchronised (main sequence) binary. We obtain the emission measure distribution, temperature structures, plasma densities, and abundances of this system and compare them with the coronal properties of other young/active stars. HD 155555 AB and HD 155555 C produce copious X-ray emission with log Lx of 30.54 and 29.30, respectively, in the 0.3-6.0 keV energy band. The light curves of individual stars show variability on timescales of few minutes to hours. We analyse the dispersed spectra and reconstruct the emission measure distribution using spectral line analysis. The resulting elemental abundances exhibit inverse first ionisation potential effect in both cases. An analysis of He-like triplets yields a range of coronal electron densities ~10^10-10^13 cm-3. Since HD 155555 AB is classified both as an RS CVn and a PMS star, we compare our results with those of other slightly older active main-sequence stars and T Tauri stars, which indicates that the coronal properties of HD 155555 AB closely resemble that of an older RS CVn binary rather than a younger PMS star. Our results also suggests that the properties of HD 155555 C is very similar to those of other active M dwarfs.Comment: 17 pages, 23 figues, Accepted in Ap

X-ray Development of the Classical Nova V2672 Ophiuchi with Suzaku

We report the Suzaku detection of a rapid flare-like X-ray flux amplification early in the development of the classical nova V2672 Ophiuchi. Two target-of-opportunity ~25 ks X-ray observations were made 12 and 22 days after the outburst. The flux amplification was found in the latter half of day 12. Time-sliced spectra are characterized by a growing supersoft excess with edge-like structures and a relatively stable optically-thin thermal component with Ka emission lines from highly ionized Si. The observed spectral evolution is consistent with a model that has a time development of circumstellar absorption, for which we obtain the decline rate of ~10-40 % in a time scale of 0.2 d on day 12. Such a rapid drop of absorption and short-term flux variability on day 12 suggest inhomogeneous ejecta with dense blobs/holes in the line of sight. Then on day 22 the fluxes of both supersoft and thin-thermal plasma components become significantly fainter. Based on the serendipitous results we discuss the nature of this source in the context of both short- and long-term X-ray behavior.Comment: To appear in PASJ; 9 pages, 5 figures, 2 table

Vibration/vacuum screening of space lubricants Final report

Evaluation of solid film lubricants for ball bearings in space environment

Test evaluation of fuel cell catalysts Quarterly report, 15 Feb. - 15 May 1967

Catalytic activity of iron compounds for fuel cell catalyst

Updated Spitzer Emission Spectroscopy of Bright Transiting Hot Jupiter HD189733b

We analyze all existing secondary eclipse time series spectroscopy of hot Jupiter HD189733b acquired with the now defunct Spitzer/IRS instrument. We describe the novel approaches we develop to remove the systematic effects and extract accurate secondary eclipse depths as a function of wavelength in order to construct the emission spectrum of the exoplanet. We compare our results to a previous study by Grillmair et al. that did not examine all data sets available to us. We are able to confirm the detection of a water feature near 6{\mu}m claimed by Grillmair et al. We compare the planetary emission spectrum to three model families -- based on isothermal atmosphere, gray atmosphere, and two realizations of the complex radiative transfer model by Burrows et al., adopted in Grillmair et al.'s study. While we are able to reject the simple isothermal and gray models based on the data at the 97% level just from the IRS data, these rejections hinge on eclipses measured within relatively narrow wavelength range, between 5.5 and 7{\mu}m. This underscores the need for observational studies with broad wavelength coverage and high spectral resolution, in order to obtain robust information on exoplanet atmospheres.Comment: 16 pages, 13 figures and 3 tables. Accepted for publication in Ap