Creating City Cyclists: Understanding Why People Start, and Sometimes Stop, Cycling in South London

Cycling can be framed as a means of practically re-ordering movement, connection and experience. Drawing upon readings in mobility and urban studies, the thesis addresses deficiencies in practice theory by investigating how to better conceptualise dynamic change, socio-technical multiplicity, and embodied experiences of technology. Investigating people’s experiences of using bicycles to live in a city, it asks how the take up, alteration and divestment of different practices might influence how urban times and spaces are practically ordered. The study develops disciplinary debates on place and practice by engaging with the theoretical concepts of emergence, encounter and cosmogony. It empirically investigates three sub-questions: how are cycling-journeys experienced in London; how do experiences of cycling the city alter urban practice; and how does cycling influence the practical remaking of urban place? Methodologically, 20 participants were recruited for a year’s fieldwork comprised of 3 methods; ride-along with videoelicitation, diary-interview and focus groups. This iteratively investigated three practices; civility, navigation and placemaking. Understanding the urban as a means and outcome of systematised contingent ordering - a machinic complex -the study suggests that cycling reconfigures how such ordering occurs. Rather than investigating practices of cycling it investigates how urban practices incorporate experiences of cycling and might bedisseminated, intensified, disrupted, or reconfigured. By decentring cycling and fracturing the study’s focal point, the framework facilitates a conceptualisation of urban practices as traversing an array of contingent situations, via a variety of technologically-mediated engagements. The findings explore how quotidian mobility creates durable social forms and places through transient, mounted but systematised and repeated meetings in the street. This refines our understanding of the spatial and performative. It argues that creative repairs making modest alterations to elements of skill, meaning and infrastructure might catalyse more radical systemic reconfigurations of their links, or initiate self-perpetuating trajectories of further change

Modulations in Multi-Periodic Blue Variables in the LMC

As shown by Mennickent, et al(2003), a subset of the blue variable stars in the Large Magellanic Cloud exhibit brightness variability of small amplitude in the period range 2.4 to 16 days as well as larger amplitude variability with periods of 140 to 600 days, with a remarkably tight relation between the long and the short periods. Our re-examination of these objects has led to the discovery of additional variability. The Fourier spectra of 11 of their 30 objects have 3 or 4 peaks above the noise level and a linear relation of the form f_a = 2(f_b - f_L) among three of the frequencies. An explanation of this relation requires an interplay between the binary motion and that of a third object. The two frequency relations together with the Fourier amplitude ratios pose a challenging modeling problem.Comment: 4 pages, 3 figures, Astrophysical Journal (in press

Ultra-Low Amplitude Cepheids in the Large Magellanic Cloud

The MACHO variables of LMC Field 77 that lie in the vicinity of the Cepheid instability strip are reexamined. Among the 144 variables that we identify as Cepheids we find 14 that have Fourier amplitudes <0.05 mag in the MACHO red band, of which 7 have an amplitude <0.006 mag : we dub the latter group of stars ultra-low amplitude (ULA) Cepheids. The variability of these objects is verified by a comparison of the MACHO red with the MACHO blue lightcurves and with those of the corresponding OGLE LMC stars. The occurrence of ULA Cepheids is in agreement with theory. We have also discovered 2 low amplitude variables whose periods are about a factor of 5--6 smaller than those of F Cepheids of equal apparent magnitude. We suggest that these objects are Cepheids undergoing pulsations in a surface mode and that they belong to a novel class of Strange Cepheids (or Surface Mode Cepheids) whose existence was predicted by Buchler et al. (1997).Comment: 4 pages, 5 figures, slightly revised, to appear in ApJ Letter

Ultra-low Amplitude Variables in the LMC -- Classical Cepheids, Pop. II Cepheids, RV Tau Stars and Binary Variables

A search for variable stars with ultra-low amplitudes (ULA), in the millimag range, has been made in the combined MACHO and OGLE data bases in the broad vicinity of the Cepheid instability strip in the HR diagram. A total of 25 singly periodic and 4 multiply periodic ULA objects has been uncovered. Our analysis does not allow us to distinguish between pulsational and ellipsoidal (binary) variability, nor between LMC and foreground objects. However, the objects are strongly clustered and appear to be associated with the pulsational instability strips of LMC Pop. I and II variables. When combined with the ULA variables of Buchler et al (2005) a total of 20 objects fall close to the classical Cepheid instability strip. However, they appear to fall on parallel period-magnitude relations that are shifted to slightly higher magnitude which would confer them a different evolutionary status. Low amplitude RV Tauri and Pop. II Cepheids have been uncovered that do not appear in the MACHO or OGLE catalogs. Interestingly, a set of binaries seem to lie on a PM relation that is essentially parallel to that of the RV Tauri/Pop. II Cepheids.Comment: 13 pages, 13 (color) figures. Astrophysical Journal (accepted for publlication

The Brightest Carbon Stars

It is currently accepted that Hot-Bottom-Burning (HBB) in intermediate-mass asymptotic giant branch (AGB) stars prevents the formation of C~stars. Nevertheless, we present in this paper the results of some detailed evolutionary calculations which show that even with HBB we obtain C~stars at the highest luminosities reached on the AGB. This is due to mass-loss reducing the envelope mass so that HBB ceases but dredge-up continues. The high mass-loss rate produces an optically thick wind before the star reaches C/O>1. This is consistent with the recent results of van Loon et al. (1997a,b) who find obscured C~stars in the Magellanic Clouds at luminosities up to M_{bol} = -6.8.Comment: 4 pages, 2 figures included. Note that these are quality-reduced figures for net transmission. If you want best quality figures, these are available from http://www.maths.monash.edu.au/~johnl/preprints/preprints.htm

Future Needs for Tribo-Corrosion Research and Testing

Tribo-corrosion is an emerging interdisciplinary subject that spans from basic research on the behavior of surfaces in mechanical contact in chemically active surroundings to the test methods needed to quantify its effects, and from the selection of materials for bio-implants to the minimization of surface degradation and wastage in advanced energy conversion systems. Such a diverse field brings with it many challenges in understanding, testing, standardization, and application to engineering practice. This paper summarizes a panel discussion and participant survey held at the Third International Symposium on Tribo-Corrosion in Atlanta, Georgia, USA, in April 2012. It reflects a sense of agreement on many of the key scientific challenges in the field and the fact that tribo-corrosion is still in its infancy in terms of broad industry recognition, education, and the ability of those who conduct tribo-corrosion research to connect their laboratory results and theories to applications. Some sub-fields, notably the bio-tribo-corrosion of medical implants, have witnessed active international research efforts, but the engineering community in many other important areas of technology may not yet be aware of the field despite numerous tribo-corrosion problems that may exist within their purview

Early and Late-Time Observations of SN 2008ha: Additional Constraints for the Progenitor and Explosion

We present a new maximum-light optical spectrum of the the extremely low luminosity and exceptionally low energy Type Ia supernova (SN Ia) 2008ha, obtained one week before the earliest published spectrum. Previous observations of SN 2008ha were unable to distinguish between a massive star and white dwarf origin for the SN. The new maximum-light spectrum, obtained one week before the earliest previously published spectrum, unambiguously shows features corresponding to intermediate mass elements, including silicon, sulfur, and carbon. Although strong silicon features are seen in some core-collapse SNe, sulfur features, which are a signature of carbon/oxygen burning, have always been observed to be weak in such events. It is therefore likely that SN 2008ha was the result of a thermonuclear explosion of a carbon-oxygen white dwarf. Carbon features at maximum light show that unburned material is present to significant depths in the SN ejecta, strengthening the case that SN 2008ha was a failed deflagration. We also present late-time imaging and spectroscopy that are consistent with this scenario.Comment: ApJL, accepted. 5 pages, 3 figure

On a minimal model for estimating climate sensitivity

In a recent issue of this journal, Loehle (2014) presents a "minimal model" for estimating climate sensitivity, identical to that previously published by Loehle and Scafetta (2011). The novelty in the more recent paper lies in the straightforward calculation of an estimate of transient climate response based on the model and an estimate of equilibrium climate sensitivity derived therefrom, via a flawed methodology. We demonstrate that the Loehle and Scafetta model systematically underestimates the transient climate response, due to a number of unsupportable assumptions regarding the climate system. Once the flaws in Loehle and Scafetta's model are addressed, the estimates of transient climate response and equilibrium climate sensitivity derived from the model are entirely consistent with those obtained from general circulation models, and indeed exclude the possibility of low climate sensitivity, directly contradicting the principal conclusion drawn by Loehle. Further, we present an even more parsimonious model for estimating climate sensitivity. Our model is based on observed changes in radiative forcings, and is therefore constrained by physics, unlike the Loehle model, which is little more than a curve-fitting exercise