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Search Results: 1 - 10 of 138832 matches for " K. Pilkington "
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Metallicity Gradients in Simulated Disk Galaxies
K. Pilkington,B. K. Gibson
Physics , 2012,
Abstract: The stellar metallicity and abundance ratio gradients from the fiducial late-type galaxy simulation of Stinson et al. (2010) are presented. Over 1-3 scalelengths, gradients are shown to flatten with time, consistent with empirical evidence at high- and low-redshifts. Kinematic effects, including radial migration, though, flatten these intrinsicly steep gradients such that by redshift z=0, the measured gradients of these (now) old stars are flatter than their young counterparts, in contradiction to what is observed locally. Conversely, the stellar [O/Fe] gradient is (to first order) robust against migration, remaining fairly flat for both young and old populations today.
Chemical Evolution of the Carina Dwarf Spheroidal
K. Pilkington,B. K. Gibson
Physics , 2012,
Abstract: We explore a range of chemical evolution models for the Local Group dwarf spheroidal (dSph) galaxy, Carina. A novel aspect of our work is the removal of the star formation history (SFH) as a `free parameter' in the modeling, making use, instead, of its colour-magnitude diagram (CMD)-constrained SFH. By varying the relative roles of galactic winds, re-accretion, and ram-pressure stripping within the modeling, we converge on a favoured scenario which emphasises the respective roles of winds and re-accretion. While our model is successful in recovering most elemental abundance patterns, comparable success is not found for all the neutron capture elements. Neglecting the effects of stripping results in predicted gas fractions approximately two orders of magnitude too high, relative to that observed.
The Erasure of Race and Racism  [PDF]
Andrew Pilkington
Advances in Applied Sociology (AASoci) , 2013, DOI: 10.4236/aasoci.2013.32012
Abstract: With the advent in the UK of a new Labour government in 1997 and the publication of the Macpherson report in 1999, public debate over race and racism was reactivated after a long period when such concerns had remained dormant. In this article, I shall draw upon an ethnographic study of one university in the UK over a ten year period (Pilkington, 2011a). Here I shall focus on the early part of that period, predominantly 1999-2003 when arguably issues relating to race and racism were at their height. I examine how Midshire University responded in turn to the Commission for Racial Equality’s (CRE’s) leadership challenge; the government’s strategies for higher education relating to widening participation and equal opportunities; and the race relations legislation. The story is not a happy one, with the institution constantly subsuming race under a more general agenda and in the process failing to address the specificities of race. Midshire University is unlikely to be the only university to do this. Universities in UK are typically characterised by the “sheer weight of whiteness” which blinds senior managers and academics to racial inequalities in their midst.
The Distribution of Young Stars and Metals in Simulated Cosmological Disk Galaxies
K. Pilkington,B. K. Gibson,D. H. Jones
Physics , 2012,
Abstract: We examine the distribution of young stars associated with the spiral arms of a simulated L* cosmological disk galaxy. We find age patterns orthogonal to the arms which are not inconsistent with the predictions of classical density wave theory, a view further supported by recent observations of face-on Grand Design spirals such as M51. The distribution of metals within a simulated ~0.1L* disk is presented, reinforcing the link between star formation, the age-metallicity relation, and the metallicity distribution function.
Detecting Higgs bosons in the bb decay channel using forward proton tagging at the LHC
Cox, B. E.;Loebinger, F. K.;Pilkington, A. D.
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/1126-6708/2007/10/090
Abstract: A detailed study is presented of the search for Higgs bosons in the b-decay channel in the central exclusive production process at the LHC. We present results for proton tagging detectors at both 220m and 420m around ATLAS or CMS. We consider two benchmark scenarios; a Standard Model (SM) Higgs boson and the m_h^{max} scenario of the Minimal Supersymmetric Standard Model (MSSM). Detector acceptance, smearing and event trigger strategies are considered. We find that the SM Higgs will be challenging to observe in the b-jet channel without improvements to the currently proposed experimental configuration, but a neutral scalar MSSM Higgs Boson could be observable in the b-jet channel with a significance of 3 sigma or greater within three years of data taking at all luminosities between 2 x 10^{33} cm^{-2} s^{-1} and 10^{34} cm^{-2} s^{-1}, and at 5 sigma or greater after three years in certain scenarios.
Decoding the message from meteoritic stardust silicon carbide grains
Karen M. Lewis,Maria Lugaro,Brad K. Gibson,Kate Pilkington
Physics , 2013, DOI: 10.1088/2041-8205/768/1/L19
Abstract: Micron-sized stardust grains that originated in ancient stars are recovered from meteorites and analysed using high-resolution mass spectrometry. The most widely studied type of stardust is silicon carbide (SiC). Thousands of these grains have been analysed with high precision for their Si isotopic composition. Here we show that the distribution of the Si isotopic composition of the vast majority of stardust SiC grains carry the imprints of a spread in the age-metallicity distribution of their parent stars and of a power-law increase of the relative formation efficiency of SiC dust with the metallicity. This result offers a solution for the long-standing problem of silicon in stardust SiC grains, confirms the necessity of coupling chemistry and dynamics in simulations of the chemical evolution of our Galaxy, and constrains the modelling of dust condensation in stellar winds as function of the metallicity.
News from the British Neuro-Oncology Society (BNOS): Where Have We Come Since 1980?
Pilkington G
European Association of NeuroOncology Magazine , 2012,
On The Weak Order Of Orthogonal Groups
Annette Pilkington
Mathematics , 2011,
Abstract: A structure of a complete lattice (in the sense of a poset) is defined on the underlying set of the orhtogonal group of a real Euclidean space, by a construction analogous to that of the weak order of a Coxeter system in terms of its root system. This gives rise to a complte rootoid in the sense of Dyer, with the orthogonal group as underlying group.
Highest Weight Categories For Number Rings
Annette Pilkington
Mathematics , 2011,
Abstract: This paper examines the concept of a stratified exact category in the context of number rings and corresponding Galois groups. BGG reciprocity and duality are proven for these categories making them highest weight categories. The strong connections between the structure of the category and ramification in the ring are explored.
The Chemical and Dynamical Evolution of Isolated Dwarf Galaxies
K. Pilkington,B. K. Gibson,F. Calura,G. S. Stinson,C. B. Brook,A. Brooks
Physics , 2011, DOI: 10.1007/978-3-642-22018-0_4
Abstract: Using a suite of simulations (Governato et al. 2010) which successfully produce bulgeless (dwarf) disk galaxies, we provide an analysis of their associated cold interstellar media (ISM) and stellar chemical abundance patterns. A preliminary comparison with observations is undertaken, in order to assess whether the properties of the cold gas and chemistry of the stellar components are recovered successfully. To this end, we have extracted the radial and vertical gas density profiles, neutral hydrogen velocity dispersion, and the power spectrum of structure within the ISM. We complement this analysis of the cold gas with a brief examination of the simulations' metallicity distribution functions and the distribution of alpha-elements-to-iron.
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