The X-ray binary population in M33: II. X-ray spectra and variability

In this paper we investigate the X-ray spectra and X-ray spectral variability of compact X-ray sources for 3 Chandra observations of the Local Group galaxy M33. The observations are centered on the nucleus and the star forming region NGC 604. In the observations 261 sources have been detected. For a total of 43 sources the number of net counts is above 100, sufficient for a more detailed spectral fitting. Of these sources, 25 have been observed in more than one observation, allowing the study of spectral variability on ~months timescales. A quarter of the sources are found to be variable between observations. However, except for two foreground sources, no source is variable within any observation above the 99% confidence level. Only six sources show significant spectral variability between observations. A comparison of N_H values with HI observations shows that X-ray absorption values are consistent with Galactic X-ray binaries and most sources in M33 are intrinsically absorbed. The pattern of variability and the spectral parameters of these sources are consistent with the M33 X-ray source population being dominated by X-ray binaries: Two thirds of the 43 bright sources have spectral and timing properties consistent with X-ray binaries; we also find two candidates for super-soft sources and two candidates for quasi-soft sources.Comment: 25 pages, ApJ accepte

Thematic Report Three - Asylum, Security and Extremism

This is the final of three Thematic Reports published as part of a CREST-funded project carried out by a team of researchers at City, University of London, and Cranfield University at the Defence Academy of the United Kingdom. With the objective of better understanding Tamil diaspora communities’ attitudes and engagement in the Sri Lankan civil conflict (1983-2009) and its aftermath, the project explores diaspora and refugee communities’ relationship with the changing socio-political environment in the homeland, exploring what shapes and influences processes of radicalisation or moderation among these communities. It recognises that the socio-political circumstances in which these processes develop are often crucial to understanding why a community or individuals within that community abroad act in a certain way; this includes analysis of different scales and levels of engagement, both in home and host countries, as well as different ‘areas’ of engagement, which can include social, economic and political interactions. The three thematic reports produced as part of this project cumulatively build a comprehensive picture of the state of knowledge on political action among diaspora, refugee and asylum populations. The theoretically-informed, literature- and evidence-grounded conclusions arising from these three thematic reports are therefore of relevance beyond the case of Sri Lanka. Thematic Report One discussed how four analytical concepts, diaspora, transnationalism, cosmopolitanism, and translocalism, have come to frame the academic discussion of overseas politics and the potential of these concepts to shed light on the relationship between mobility and political action. Thematic Report Two complements the previous report’s broad conceptual discussion by specifically focusing on an analysis of the context and drivers of political action among diaspora and refugee populations, and engaging with the term ‘refugee politics’. The current paper – the final Thematic Report – analyses the growing ‘securitisation’ of refugees and other forcibly displaced populations and calls for greater consideration of structural vulnerabilities in the forced migration and displacement cycle that increase the risk of radicalisation, extremism and related political behaviours

Who is the new sheriff in town regulating boreal forest growth?

Climate change appears to be altering boreal forests. One recently observed symptom of these changes has been an apparent weakening of the positive relationship between high-latitude boreal tree growth and temperature at some sites (D'Arrigo et al 2008). This phenomenon is referred to as the 'divergence problem' or 'divergence effect' and is thought to reflect a non-linear relationship between temperature and tree growth, where recent warming has allowed other factors besides growing-season temperature to emerge as dominant regulators of annual growth rates

Increasing impacts of extreme droughts on vegetation productivity under climate change

Terrestrial gross primary production (GPP) is the basis of vegetation growth and food production globally1 and plays a critical role in regulating atmospheric CO2 through its impact on ecosystem carbon balance. Even though higher CO2 concentrations in future decades can increase GPP2, low soil water availability, heat stress and disturbances associated with droughts could reduce the benefits of such CO2 fertilization. Here we analysed outputs of 13 Earth system models to show an increasingly stronger impact on GPP by extreme droughts than by mild and moderate droughts over the twenty-first century. Due to a dramatic increase in the frequency of extreme droughts, the magnitude of globally averaged reductions in GPP associated with extreme droughts was projected to be nearly tripled by the last quarter of this century (2075–2099) relative to that of the historical period (1850–1999) under both high and intermediate GHG emission scenarios. By contrast, the magnitude of GPP reductions associated with mild and moderate droughts was not projected to increase substantially. Our analysis indicates a high risk of extreme droughts to the global carbon cycle with atmospheric warming; however, this risk can be potentially mitigated by positive anomalies of GPP associated with favourable environmental conditions

How Reasoning Aims at Truth

Many hold that theoretical reasoning aims at truth. In this paper, I ask what it is for reasoning to be thus aim-directed. Standard answers to this question explain reasoning’s aim-directedness in terms of intentions, dispositions, or rule-following. I argue that, while these views contain important insights, they are not satisfactory. As an alternative, I introduce and defend a novel account: reasoning aims at truth in virtue of being the exercise of a distinctive kind of cognitive power, one that, unlike ordinary dispositions, is capable of fully explaining its own exercises. I argue that this account is able to avoid the difficulties plaguing standard accounts of the relevant sort of mental teleology

Investigating the effects of particle shape on normal compression and overconsolidation using DEM

Discrete element modelling of normal compression has been simulated on a sample of breakable two-ball clumps and compared to that of spheres. In both cases the size effect on strength is assumed to be that of real silica sand. The slopes of the normal compression lines are compared and found to be consistent with the proposed equation of the normal compression line. The values of the coefficient of earth pressure at rest K0,nc are also compared and related to the critical state fiction angles for the two materials. The breakable samples have then been unloaded to establish the stress ratios on unloading. At low overconsolidation ratios the values of K0 follow a well-established empirical relationship and realistic Poisson ratios are observed. On progressive unloading both samples head towards passive failure, and the values of the critical state lines in extension in q–p' space are found to be consistent with the critical state angles deduced from the values of K0 during normal compression. The paper highlights the important role of particle shape in governing the stress ratio during both normal compression and subsequent overconsolidation

Thematic Report One - Understanding Transnational Diaspora Politics: A Conceptual Discussion

This is the first of three CREST-funded Thematic Reports published by a team of researchers at City, University of London, and Cranfield University at the Defence Academy of the United Kingdom examining political action among diaspora populations. The purpose of the report is to explore the theoretical and conceptual basis underpinning academic debates on engagement in the politics of conflict and post-conflict by communities living overseas. The research team is interested specifically in the Sri Lankan civil conflict between 1983 and 2009 and its aftermath, and understanding the attitudes towards and involvement in that conflict on the part of Tamil diaspora communities. The CREST project is exploring diaspora communities’ relationship with the changing socio-political environment in the homeland and how this influences processes of radicalisation or moderation. It recognises that the socio-political circumstances in which these processes develop are often crucial towards understanding why a community or individuals within that community abroad act in a certain way; this includes analysis of different scales and levels of engagement, both in home countries and in host countries, as well as different ‘areas’ of engagement, which can range from social to economic to political interactions. The following review is not specific to the Sri Lankan situation; it is rather concerned with how four concepts, diaspora, transnationalism, cosmopolitanism, and translocalism, have come to frame the academic discussion of diaspora or more broadly overseas politics and the potential of the concepts to shed light on the relationship between mobility and political action. It considers the extent to which these concepts are helpful in identifying the rationale behind specific methods of political participation offering critical reflections on the analytical and normative usefulness of these terms

Thematic Report Two - The Engagement of Refugees in Transnational Politics: Lessons from the Migration, Diaspora and Refugee Studies Literature

This is the second of three CREST-funded Thematic Reports published by a team of researchers at City, University of London, and Cranfield University at the Defence Academy of the United Kingdom, that cumulatively build a comprehensive picture of the state of knowledge on political action among diaspora and refugee populations. The research team is specifically interested in applying the theoretically-informed, literature and evidence grounded conclusions arising from these reports to understand the attitudes towards and involvement in the Sri Lankan civil conflict (1983-2009) and its aftermath by Tamil diaspora communities, but with a broader application. The CREST project is exploring diaspora and refugee communities’ relationship with the changing socio-political environment in the homeland and how this influences processes of radicalisation or moderation. It recognises that the socio-political circumstances in which these processes develop are often crucial to understanding why a community or individuals within that community abroad act in a certain way; this includes analysis of different scales and levels of engagement, both in home countries and in host countries, as well as different ‘areas’ of engagement, which can include social, economic and political interactions. Thematic Report One discussed how four analytical concepts, diaspora, transnationalism, cosmopolitanism, and translocalism, have come to frame the academic discussion of overseas politics and the potential of the concepts to shed light on the relationship between mobility and political action. The current paper – Thematic Report Two – complements the previous report’s broad conceptual discussion by specifically focusing on an analysis of the context and drivers of political action among diaspora and refugee populations, and engaging with the term ‘refugee politics’. It considers if the available diaspora and migration literature sheds light on whether the processes and dynamics of forced migration are likely to generate identifiable forms of political engagement