Resolving G-torsors by abelian base extensions

Let G be a linear algebraic group defined over a field k. We prove that, under mild assumptions on k and G, there exists a finite k-subgroup S of G such that the natural map H^1(K, S) -> H^1(K, G) is surjective for every field extension K/k. We give several applications of this result in the case where k an algebraically closed field of characteristic zero and K/k is finitely generated. In particular, we prove that for every z in H^1(K, G) there exists an abelian field extension L/K such that z_L \in H^1(L, G) is represented by a G-torsor over a projective variety. From this we deduce that z_L has trivial point obstruction. We also show that a (strong) variant of the algebraic form of Hilbert's 13th problem implies that the maximal abelian extension of K has cohomological dimension =< 1. The last assertion, if true, would prove conjectures of Bogomolov and Koenigsmann, answer a question of Tits and establish an important case of Serre's Conjecture II for the group E_8.Comment: New material added on the no-name lemma in Section 4 and on Hilbert's 13th problem in Section 9. A mistake in the proof of Proposition 2.3 is correcte

The precautions of clinical waste: disposable medical sharps in the United Kingdom

This article deals with recent changes in UK guidance on clinical waste, in particular a shift to disposable, single-use instruments and sharps. I use interviews conducted with nurses from a GP practice and two clinical waste managers at alternative treatment and incineration sites as a springboard for reflection on the relationship between the legislation on clinical waste management and its implementation. Scrutinizing the UK guidance, European legislation and World Health Organization principles, I draw out interviewees’ concerns that the changed practices lead to an expansion of the hazardous waste category, with an increased volume going to incineration. This raises questions regarding the regulations’ environmental and health effects, and regarding the precautionary approach embedded in the regulations. Tracing the diverse reverberations of the term ‘waste’ in different points along the journeys made by sharps in particular, and locating these questions in relation to existing literature on waste, I emphasize that public health rationales for the new practices are not made clear in the guidance. I suggest that this relative silence on the subject conceals both the uncertainties regarding the necessity for these means of managing the risks of infectious waste, and the tensions between policies of precautionary public health and environmental sustainability

A crack in the facade? Situating Singapore in global flows of electronic waste

Singapore is alleged to be a key node in global flows of e‐waste prohibited under the Basel Convention. We combine a close reading of the Convention and related documents with findings from nonparticipant observation of and interviews with Singapore‐based traders of discarded electronics. The case offers both important conceptual and empirical findings for future studies of territory in market‐making activity. Conceptually, our research suggests that it may be analytically useful in such studies to conceptualize territory without presupposing that it is generated as a result of separate domains or logics such as ‘the political’ or ‘the economic’. Empirically, we find that the regulatory framework of the Convention, combined with the action of traders based in Singapore, generates a territorialization of the city‐state such that it operates as a crack in the regulatory edifice of the Convention, even as Singapore lawfully fulfils its obligations to it. Moreover, allegations premised on the role of Singapore as a facilitator of global e‐waste dumping misrepresent its crucial role as a conduit of electronic equipment for the significant reuse markets elsewhere in Southeast Asia and beyond. The case indicates that the allegations against Singapore hinge on the city‐state being territorialized as a ‘developing country’

Open Problems on Central Simple Algebras

We provide a survey of past research and a list of open problems regarding central simple algebras and the Brauer group over a field, intended both for experts and for beginners.Comment: v2 has some small revisions to the text. Some items are re-numbered, compared to v

Economies of Recycling, ‘Consumption Work’ and Divisions of Labour in Sweden and England

The recycling of domestic waste has become increasingly significant over recent years with governments across the world pledging increases in their recycling rates. But success in reaching targets relies on the input and effort of the household and consumer. This article argues that the work consumers regularly perform in sorting their recyclable waste into different fractions and, in some cases, transporting this to communal sites, plays an integral role in the overall division of labour within waste management processes. We develop the concept of ‘consumption work’ drawing on comparative research in Sweden and England to show how the consumer is both at the end and starting point of a circular global economy of materials re-use. The work that consumers do has not been systematically explored as a distinctive form of labour, and we argue that treating it seriously requires revision of the conventional approach to the division of labour

Burying the 'refuse revolution': the rise of controlled tipping in Britain 1920-1960

The definitive, peer-reviewed and edited version of this article is published in Environment and Planning A, 42, 5, 1033-1048, 2010, 10.1068/a42120.This paper investigates the emergence of ‘controlled tipping’ as the dominant method of municipal waste disposal in Britain between 1920 and 1960. The triumph of controlled tipping, despite the availability of alternative disposal technologies, needs to be understood in the context of the contested meanings of ‘waste’ and ‘wasteland’, which helped to determine attitudes and approaches to disposal. Following the conclusion of the First World War there was an urgent requirement for a cheap means of disposing of increasing amounts of urban municipal waste. The obvious choice was tipping. Before the war, however, refuse tipping had been rejected as insanitary by the emerging waste disposal profession. Public cleansing professionals therefore had to recuperate tipping as a medically and environmentally benign mode of disposal that was reconcilable with the needs of sanitary science and landscape preservation. Controlled tipping, with its combined claims to scientific progress and the revalorization of refuse, enabled dumping to be successfully re-produced as the dominant mode of municipal refuse disposal in Britain. However, tipping faced further challenges after 1945 from changing popular understandings of the value of ‘derelict’ landscapes and from the politics of amenity. The ‘refuse revolution’ was a work in progress

Identification of a Bacterial-Like HslVU Protease in the Mitochondria of Trypanosoma brucei and Its Role in Mitochondrial DNA Replication

ATP-dependent protease complexes are present in all living organisms, including the 26S proteasome in eukaryotes, Archaea, and Actinomycetales, and the HslVU protease in eubacteria. The structure of HslVU protease resembles that of the 26S proteasome, and the simultaneous presence of both proteases in one organism was deemed unlikely. However, HslVU homologs have been identified recently in some primordial eukaryotes, though their potential function remains elusive. We characterized the HslVU homolog from Trypanosoma brucei, a eukaryotic protozoan parasite and the causative agent of human sleeping sickness. TbHslVU has ATP-dependent peptidase activity and, like its bacterial counterpart, has essential lysine and N-terminal threonines in the catalytic subunit. By epitope tagging, TbHslVU localizes to mitochondria and is associated with the mitochondrial genome, kinetoplast DNA (kDNA). RNAi of TbHslVU dramatically affects the kDNA by causing over-replication of the minicircle DNA. This leads to defects in kDNA segregation and, subsequently, to continuous network growth to an enormous size. Multiple discrete foci of nicked/gapped minicircles are formed on the periphery of kDNA disc, suggesting a failure in repairing the gaps in the minicircles for kDNA segregation. TbHslVU is a eubacterial protease identified in the mitochondria of a eukaryote. It has a novel function in regulating mitochondrial DNA replication that has never been observed in other organisms