Long period variables and mass loss in the globular clusters NGC 362 and NGC 2808

The pulsation periods of long period variables (LPVs) depend on their mass and helium abundance as well as on their luminosity and metal abundance. Comparison of the observed periods of LPVs in globular clusters with models is capable of revealing the amount of mass lost on the giant branch and the helium abundance.} {We aim to determine the amount of mass loss that has occurred on the giant branches of the low metallicity globular clusters NGC 362 and NGC 2808. We also aim to see if the LPVs in NGC 2808 can tell us about helium abundance variations in this cluster.} We have used optical monitoring of NGC 362 and NGC 2808 to determine periods for the LPVs in these clusters. We have made linear pulsation models for the pulsating stars in these clusters taking into account variations in mass and helium abundance. Reliable periods have been determined for 11 LPVs in NGC 362 and 15 LPVs in NGC 2808. Comparison of the observed variables with models in the logP - K diagram shows that mass loss of ~0.15-0.2 Msun is required on the first giant branch in these clusters, in agreement with estimates from other methods. In NGC 2808, there is evidence that a high helium abundance of Y~0.4 is required to explain the periods of several of the LPVs. It would be interesting to determine periods for LPVs in other Galactic globular clusters where a helium abundance variation is suspected to see if the completely independent test for a high helium abundance provided by the LPVs can confirm the high helium abundance estimates.Comment: 13 pages, 12 figures, accepted for publication in Astronomy & Astrophysic

Coset Constructions of Logarithmic (1,p)-Models

One of the best understood families of logarithmic conformal field theories is that consisting of the (1,p) models (p = 2, 3, ...) of central charge c_{1,p} = 1 - 6 (p-1)^2 / p. This family includes the theories corresponding to the singlet algebras M(p) and the triplet algebras W(p), as well as the ubiquitous symplectic fermions theory. In this work, these algebras are realized through a coset construction. The W^(2)_n algebra of level k was introduced by Feigin and Semikhatov as a (conjectured) quantum hamiltonian reduction of affine sl(n)_k, generalising the Bershadsky-Polyakov algebra W^(2)_3. Inspired by work of Adamovic for p=3, vertex algebras B_p are constructed as subalgebras of the kernel of certain screening charges acting on a rank 2 lattice vertex algebra of indefinite signature. It is shown that for p <= 5, the algebra B_p is a homomorphic image of W^(2)_{p-1} at level -(p-1)^2 / p and that the known part of the operator product algebra of the latter algebra is consistent with this holding for p>5 as well. The triplet algebra W(p) is then realised as a coset inside the full kernel of the screening operator, while the singlet algebra M(p) is similarly realised inside B_p. As an application, and to illustrate these results, the coset character decompositions are explicitly worked out for p=2 and 3.Comment: 22 pages, v2: clarified our definition of Feigin-Semikhatov algebras and added ref

Learning computing heritage through gaming – whilst teaching digital development through history

This paper analyses the potential of computer games and interactive projects within the learning programmes for cultural heritage institutions through our experiences working in partnership between higher education and a museum. Gamification is cited as a key disruptive technology for the business and enterprise community, and developments in games technology are also driving the expansion of digital media into all different screen spaces, and various platforms. Our research aims to take these as beneficial indicators for pedagogic development, using gaming to support knowledge transfer related to a museum setting, and using the museum as a key scenario for our students to support the practice of game development. Thus gamification is applied as both a topic and a methodology for educational purposes

Emission from Very Small Grains and PAH Molecules in Monte Carlo Radiation Transfer Codes: Application to the Edge-On Disk of Gomez's Hamburger

We have modeled optical to far infrared images, photometry, and spectroscopy of the object known as Gomez's Hamburger. We reproduce the images and spectrum with an edge-on disk of mass 0.3M_sun and radius 1600AU, surrounding an A0 III star at a distance of 280pc. Our mass estimate is in excellent agreement with recent CO observations. However, our distance determination is more than an order of magnitude smaller than previous analyses which inaccurately interpreted the optical spectrum. To accurately model the infrared spectrum we have extended our Monte Carlo radiation transfer codes to include emission from polycyclic aromatic hydrocarbon (PAH) molecules and very small grains (VSG). We do this using pre-computed PAH/VSG emissivity files for a wide range of values of the mean intensity of the exciting radiation field. When Monte Carlo energy packets are absorbed by PAHs/VSGs we reprocess them to other wavelengths by sampling from the emissivity files, thus simulating the absorption and re-emission process without reproducing lengthy computations of statistical equilibrium, excitation and de-excitation in the complex many level molecules. Using emissivity lookup tables in our Monte Carlo codes gives the flexibility to use the latest grain physics calculations of PAH/VSG emissivity and opacity that are being continually updated in the light of higher resolution infrared spectra. We find our approach gives a good representation of the observed PAH spectrum from the disk of Gomez's Hamburger. Our models also indicate the PAHs/VSGs in the disk have a larger scaleheight than larger radiative equilibrium grains, providing evidence for dust coagulation and settling to the midplane.Comment: ApJ accepte

Unitary and non-unitary N=2N=2 minimal models

The unitary $N = 2$ superconformal minimal models have a long history in string theory and mathematical physics, while their non-unitary (and logarithmic) cousins have recently attracted interest from mathematicians. Here, we give an efficient and uniform analysis of all these models as an application of a type of Schur-Weyl duality, as it pertains to the well-known Kazama-Suzuki coset construction. The results include straightforward classifications of the irreducible modules, branching rules, (super)characters and (Grothendieck) fusion rules.Comment: 32 page

Industrial change in the north east region and the implications for further education departments of electrical and electronic engineering

The research study examines a number of recent developments in the electrical/electronics industry in terms of new skill requirements of the workforce and in-service training provision for both employees in industry and teaching staff in the providing colleges of further education in the North East Region. Many of the major changes which are taking place in the Region's industries are due mainly to the introduction or planned introduction of new microelectronic/computerised technology. Therefore, it is imperative that the relevant manpower planning which takes place in industry is supported by recent and relevant further education and training of its employees so that an adequate supply of sufficiently-skilled personnel is made available in order that companies can take advantage of high technology in their manufacturing processes. Data was collected, using structured interview questionnaires, from samples of managers employed in local industry and teachers in further education departments of electrical/electronic engineering. The results were later analysed using computer standard non-parametric statistics. Much of the data obtained from the survey shows that, although further training and retraining of staff was often necessary with the introduction of new computerised equipment into a company, very little reliance was actually placed on further education. Many of the in- service training needs were provided by equipment manufacturers, external agencies, and in-company programmes. Staff development in a number of the sampled colleges did no always place sufficient emphasis on regular retraining/updating of the teachers' subject area. Therefore, as a consequence, many FE teachers had not attended any recent subject-specific in-service training courses and often had to rely on text-books and other sources for information on new subject and curricular developments. Although most of the sampled managers were aware of the lack of close liaison between their industry and colleges of further education, many recognised the need to further their own involvement in local education and contribute to the content and organisation of college course curricula. In education, a disproportionately large percentage of those teachers interviewed had little or no contact with local firms, even at a superficial level of involvement e.g. an industrial visit, and many had never consulted with industry nor discussed any issues involving the courses offered by their department. The absence of any structured links between the two samples has inevitably helped to exacerbate many existing problems, and in a number of cases has, unfortunately, resulted in a complete lack of co-operation and co-ordination in terms of course planning and design