Structure And Dynamics Of Modulated Traveling Waves In Cellular Flames

We describe spatial and temporal patterns in cylindrical premixed flames in the cellular regime, $Le < 1$, where the Lewis number $Le$ is the ratio of thermal to mass diffusivity of a deficient component of the combustible mixture. A transition from stationary, axisymmetric flames to stationary cellular flames is predicted analytically if $Le$ is decreased below a critical value. We present the results of numerical computations to show that as $Le$ is further decreased traveling waves (TWs) along the flame front arise via an infinite-period bifurcation which breaks the reflection symmetry of the cellular array. Upon further decreasing $Le$ different kinds of periodically modulated traveling waves (MTWs) as well as a branch of quasiperiodically modulated traveling waves (QPMTWs) arise. These transitions are accompanied by the development of different spatial and temporal symmetries including period doublings and period halvings. We also observe the apparently chaotic temporal behavior of a disordered cellular pattern involving creation and annihilation of cells. We analytically describe the stability of the TW solution near its onset+ using suitable phase-amplitude equations. Within this framework one of the MTW's can be identified as a localized wave traveling through an underlying stationary, spatially periodic structure. We study the Eckhaus instability of the TW and find that in general they are unstable at onset in infinite systems. They can, however, become stable for larger amplitudes.Comment: to appear in Physica D 28 pages (LaTeX), 11 figures (2MB postscript file

Research communication

In this paper we review briefly histories and ideologies underlying multiculturalism in Nordic countries, highlighting tensions between integrationist and inclusive approaches. We propose a cultural ecological framework through which we discuss the possibility of a transculturalism based on Fourth World engagement with the environment. Cultural ecology is about the reciprocal interactions and transactions between people and their environments. The Fourth World is a circum-global, pan-arctic region which includes the northern parts of some Nordic countries. We argue that whether or not there is a distinctively Nordic version of multiculturalism, Nordic countries have access to Fourth World ways of engaging with the environment which transcend notions of inter- and multiculturalism and the ideological tensions associated with them

Attitudes and decision making amongst Scottish organic farmers

The number of organic farmers in Scotland increased dramatically in the period between 1997 and 2000, from 120 in 1997 to approximately 600 at the end of 2000; a five fold increase. Currently the outlook for organic farming in Scotland appears positive, despite recent publicity about farmers leaving the sector. Market prospects for all organic commodities are buoyant and there are increased Scottish Executive Organic Aid Scheme (OAS) maintenance payments in the offing. But what do Scotland’s organic producers really think about the system, which has them, tied in for at least five years? In June 2004, a representative group of Scottish organic farmers in the South of Scotland was surveyed to determine how many intended to continue farming organically once they had completed the OAS and to consider the factors affecting their decisions regarding organic conversion and cessation. Results indicated that 55% of respondents intended to continue farming organically in the short term whilst 37% intended to continue for the long term (the next decade). Although half of the respondents indicated that they were greatly influenced to convert to organic farming for wider environmental benefits and 45% for perceived job satisfaction, by far the biggest influence cited was financial benefit. Sixty nine per cent of respondents cited OAS subsidies and 55% cited the perceived price premium on produce. These fi ndings were confirmed in a second survey of organic farmers in Central Scotland between November 2004 and January 2005. In this second survey almost half (49%) of respondents cited increased long term financial returns and 44% cited the short-term cash injection from OAS payments as being of great importance in the decision to convert. The Central Scotland survey also indicated that stress and pressure on farmers following conversion was remarkably high, perhaps as a result of farmers having to adopt new practices and procedures; 97% of respondents reported increased paperwork and 79% stated that they required increased management skills. However, anecdotal evidence suggests that farmers’ attitude to organic farming changes over time from initial apprehension to more confidence in production methods and the system in general. Factors impeding farmers’ efforts to farm organically were primarily issues relating to cash flow, certification bodies, standards and marketing. Marketing issues were perceived or found to be the main problem after full organic status was achieved in the SW Scotland survey. The Central Scotland survey indicates insufficient price premiums and lack of local outlets as the main factors for cessation of organic farming. Both surveys also concur on the fact that hill farmers are more likely to leave organic farming in the short term than their upland and lowland counterparts. However, respondents from both surveys who did not intend to continue farming organically stated they planned to continue farming extensively using organic farming methods and systems

Towards data grids for microarray expression profiles

The UK DTI funded Biomedical Research Informatics Delivered by Grid Enabled Services (BRIDGES) project developed a Grid infrastructure through which research into the genetic causes of hypertension could be supported by scientists within the large Wellcome Trust funded Cardiovascular Functional Genomics project. The BRIDGES project had a focus on developing a compute Grid and a data Grid infrastructure with security at its heart. Building on the work within BRIDGES, the BBSRC funded Grid enabled Microarray Expression Profile Search (GEMEPS) project plans to provide an enhanced data Grid infrastructure to support richer queries needed for the discovery and analysis of microarray data sets, also based upon a fine-grained security infrastructure. This paper outlines the experiences gained within BRIDGES and outlines the status of the GEMEPS project, the open challenges that remain and plans for the future

Can Privatisation and Commercialisation of Public Services Help Achieve The MDGs? An Assessment

Basic services are essential to reducing poverty and improving quality of life. This working paper focuses on health, education, energy and water. These services contribute to achieving the Millennium Development Goals, as well as being goals in themselves. Over the past twenty years or so, the way in which these services are provided has been subject to considerable policy debate. There has been widespread questioning of the ability of the public sector to effectively deliver such services. Largely as a result, market-oriented solutions have been promoted as a means to overcome apparent constraints posed by state-provided services. Notwithstanding the weaknesses of state provision in many countries and localities, this working paper argues that reliance on private sector provision will fail to address the central challenges of public sector delivery. Furthermore, the process of privatisation creates an incentive framework that undermines, rather than strengthens, the accountability and capacity of the State to provide accessible and affordable services. In addition, the paper argues that the adoption of full cost recovery policies can seriously threaten achievement of the MDGs. This position does not constitute a blanket statement against private sector participation in public services or against user fees. Rather, it maintains that market-led policies fail to contribute to the MDGs and often reduce the likelihood of achieving them. Strengthening the State in assuming central responsibility for providing essential public services will help correct these setbacks.Privatisation, Millennium Development Goals, Public Services, Poverty

Mappings and accuracy for Chebyshev pseudo-spectral approximations

The effect of mappings on the approximation, by Chebyshev collocation, of functions which exhibit localized regions of rapid variation is studied. A general strategy is introduced whereby mappings are adaptively constructed which map specified classes of rapidly varying functions into low order polynomials which can be accurately approximated by Chebyshev polynomial expansions. A particular family of mappings constructed in this way is tested on a variety of rapidly varying functions similar to those occurring in approximations. It is shown that the mapped function can be approximated much more accurately by Chebyshev polynomial approximations than in physical space or where mappings constructed from other strategies are employed

Serious mortality: the date of the Fussell's Lodge long barrow

Twenty-seven radiocarbon results are now available from the Fussell’s Lodge long barrow, and are presented within an interpretive Bayesian statistical framework. Three alternative archaeological interpretations of the sequence are given, each with a separate Bayesian model. It is hard to decide between these, though we prefer the third. In the first (following the excavator), the construction is a unitary one, and the human remains included are by definition already old. In the second, the primary mortuary structure is seen as having two phases, and is set within a timber enclosure; these are later closed by the construction of a long barrow. In that model of the sequence, deposition began in the 38th century cal BC and the mortuary structure was extended probably in the 3660s–3650s cal BC; the long barrow was probably built in the 3630s–3620s cal BC; ancestral remains are not in question; and the use of the primary structure may have lasted for a century or so. In the third, preferred model, a variant of the second, we envisage the inclusion of some ancestral remains in the primary mortuary structure alongside fresh remains. This provides different estimates of the date of initial construction (probably in the last quarter of the 38th century cal BC or the first half of the 37th century cal BC) and the duration of primary use, but agrees in setting the date of the long barrow probably in the 3630s–3620s cal BC. These results are discussed in relation to the development and meanings of long barrows at both national and local scales

Talking About My Generation: the Date of the West Kennet Long Barrow

Thirty-one radiocarbon results are now available from the West Kennet long barrow, and are presented within an interpretive Bayesian statistical framework. Two alternative archaeological interpretations of the sequence are given, each with a separate Bayesian model. In our preferred interpretation, the barrow is seen as a unitary construction (given the lack of dating samples from the old ground surface, ditches or constructional features themselves), with a series of deposits of human remains made in the chambers following construction. Primary deposition in the chambers is followed by further secondary deposition of some human remains, including children, and layers of earth and chalk, the latest identifiable finds in which are Beaker sherds. In the Bayesian model for this sequence, the construction of the monument at West Kennet, as dated from the primary mortuary deposits, occurred in 3670–3635 cal. BC, probably in the middle decades of the thirty-seventh century cal. BC. The last interments of this initial use of the chambers probably occurred in 3640–3610 cal. BC. The difference between these two distributions suggests that this primary mortuary activity probably continued for only 10–30 years. After a hiatus probably lasting for rather more than a century, the infilling of the chambers began in 3620–3240 cal. BC and continued into the second half of the third millennium cal. BC. In an alternative interpretation, we do not assume that all the people dated from the primary mortuary deposits were placed in the monument in a fleshed or partially articulated condition; they could therefore have died before the monument was built, although they must have died before the end of the formation of the mortuary deposit. In the Bayesian model for this interpretation, the monument appears to belong either to the thirty-seventh century cal. BC or the mid-thirty-sixth century cal. BC, and deposition again appears short-lived, but the model is unstable. Results are discussed in relation to the setting and sequence of the local region