Thomae's formulae for non-hyperelliptic curves and spinorial square roots of theta-constants on the moduli space of curves

Determinantal formulae for Jacobian theta functions that go back to Klein are elaborated, via an idea due to Matone and Volpato. Also, the natural square roots of theta constants on the moduli space of curves whose existence was shown by Tsuyumine are proved to have a spinorial structure.Comment: 38 pages, section ``Preliminaries'' expanded into ``Principal symmetric abelian torsors'' and ``Level structures and moduli'

Singularities of surfaces and threefolds

This thesis has two parts, summarized below. The links between them are discussed at the end of this introduction. Part 1 is concerned with the problem of giving necessary and sufficient conditions for a family of surfaces to have a simultaneous resolution; this property can be regarded as a very weak form of equissingularity (cf. [Te]). I conjecture that, roughly speaking, the plurigenera Pn of a family of singular surfaces of general type are upper semi-continuous and that simultaneous resolution is possible if and only if Pn is locally constant for some n>=2 (equivalently, fo all n>=2). Two cases of this conjecture are proved, under different hypotheses on the special fibre. The techniques used are the use of adjunction ideals, suggested to me by Reid, and the results of Brieskorn, Tyurina and others on deformations of Du Val singularities (also known as rational double points, ...). A very similar approach was used by Lipman [Li] for the study of deformations of arbitrary rational singularities. Part 2 is concerned with canonical singularities, as defined by Reid [R3]. We first prove that in dimensions <=4 they are Cohen-Macaulay, and then deduce a corollary on the invariance of plurigenera in some special circumstances; this answers, in part, questions asked me by Reid. Since these results were proved, Elkik and Gabber have shown that canonical singularities are Cohen-Macaulay in all dimensions. We then consider some specific classes of singularities, and prove that they are canonical. The idea of using the techniques and results of Kulikov in this situation was suggested to me by Dave Morrison, and I subsequently learnt that Theorem 5 was already known to him and others, including Pinkham and Wahl. The point of this sections is twofold; firstly it gives an analysis of what are the simplest canonical singularities, and secondly it shows quite explicitly that the contractibility of a given configuration of surfaces in a 3-fold is a much more delicate question than in the case of curves lying on a surface. The problem of contractibility underlies Chapter 1 as well; a sufficiently strong result would kill certain cohomology groups that are the obstruction to proving the conjecture

Forests and poverty : how has our understanding of the relationship been changed by experience?

Understanding of the relationship between forests and the poor has grown enormously, especially in the last twenty years. Aid donors worked on poverty reduction in the forest sector in the 1990s and into the early 2000s, but thereafter broadened their attention to address climate change mitigation, better forest governance and timber legality, and payments for environmental services. There has so far been an incomplete integration of new insights into the nature of poor people's reliance on forests, of their own efforts to use that reliance to escape from poverty, and of current forestry aid concerns. Future projects need to choose interventions which make better use of the results now available about forestpoverty relationships, both for the better conservation of forests, and for better focus on the livelihoods of the forest-reliant poor as they continue to try to move out of poverty.Peer reviewe

Archaeology in the shadow of apartheid : race, science and prehistory

What was the relationship between archaeology and apartheid in South Africa? How did South African archaeologists navigate the relationship between science and state under apartheid? This paper makes two arguments: the first is that the nature of this relationship was less about the goals, beliefs and attitudes of individual archaeologists, than it was about the structural relationship between the discipline of archaeology and the apartheid state, evidenced in matters of political economy, the availability of funding, the influence of theory from the disciplinary metropoles in the global north, and the local social and political contexts in which archaeologists practised. The second is that describing this relationship is less a matter of choosing between binary terms of resistance and collusion, than it is about assaying a more complex and ambiguous middle ground, made up of compromises, accommodations, strategic silences, and minor failures of will and vision. In the case of South African archaeology, the edges of this relationship were sharpened by three factors: first, the discipline was largely state funded through the apartheid museum and university system; second, the subject matter of archaeology is so centrally concerned with black history and experience; and third, the need by archaeologists to access material cultures, human remains, and sites on the landscape. South African archaeology was a material beneficiary of apartheid, in the sense that the years of greatest political repression were arguably its years of greatest achievement. However, more marked than this was the manner in which the totalitarian politics of apartheid freed archaeologists from public accountability. Apartheid delivered up archaeological sites, sacred places, and human and cultural remains, for collection, representation, and display, with little possibility of popular dissent. The legacies of this history of unaccountable practice may prove to be among the most lasting legacies of the decades of archaeology in the shadow of apartheid.https://www.archaeology.org.za/saabpm2020Historical and Heritage Studie

THE EFFECTS OF CASTOR CANADENSIS (NORTH AMERICAN BEAVER) COLONIZATION ON A MINE DRAINAGE IMPACTED STREAM

This study investigated four aspects of North American Beaver (Castor canadensis) colonization: (1) retention of metals in-stream due to the presence of dams, (2) metals contamination and leachability of sediments (3) potential for metal mobilization during dam destruction and (4) hydrologic and habitat alterations due to the presence of dams. The study was conducted on an Unnamed Tributary impacted by net alkaline mine drainage since 1979 and was colonized by beaver in late 2013. By the end of 2014, most of the tributary was transformed into a series of impoundments due to beaver dams. By August 2016, the stream had eleven dams impounding water along the one-mile long study reach. The tributary flows into Tar Creek, located within the Tar Creek Superfund Site, which is the Oklahoma portion of the abandoned Tri-State Lead Zinc Mining District. The study found: (1) The presence of beaver dams showed a decrease in Fe and Cd concentrations, with minimal effect on Pb concentrations. The beaver dam with the greatest initial concentrations had mean Fe and Cd removal efficiencies of 57% and 63%, respectively. (2) Stream sediments contained elevated Cd, Pb, and Zn concentrations, with many of the metals concentrations more than five times the EPA site specific guidelines for probable effects concentrations (PEC) of 11.1 mg Cd/kg, 150 mg Pb/kg, and 2,083 mg Zn/kg. Fe concentrations in five of 13 sediment samples exceeded 200,000 mg/kg. The metals had greater concentrations in sediments at the dam outflow compared to the dam inflow. The leachate from a single sediment sample exceeded the Resource Conservation and Recovery Act (RCRA) Cd standard for Toxicity Characteristic Leaching Procedure (TCLP) with 1.08 mg/L compared to the threshold of 1.0 mg/L. (3) Beaver dam removal caused Fe and Cd concentrations to increase over time and remain elevated for the six-hour sampling period. (4) The EPA rapid habitat assessment in presence of beaver dams had a higher habitat score compared to the absence of dams, however the difference between each category was not statistically significant (p=0.26). The presence of beaver dams resulted in a 23% longer mean retention time using a conservative tracer and increased the storage capacity of the stream by 250% (2,500 m3). The study highlights the potentially important role beaver can play in the treatment of mine drainage. As ecosystem engineers, their dam building activities impound water which contributes to decreased metals concentrations

Walking as embodied research : coloniality, climate change, and the 'arts of noticing'

‘Walking is the speed for noticing….’ In 2014, I began convening walking seminars together with the researcher Christian Ernsten and the documentary photographer Dirk-Jan Visser. Each seminar involves a mix of scholars, artists, curators and activists and results in various work: journal articles, musical scores, photographic essays, and creative non-fiction. This chapter sets out the thinking behind the walking seminars, drawing on a variety of sources: recent interventions in the environmental humanities, decolonial thinking and practice, arts-based research methods and ideas around embodied research and the senses. Not least, it draws on the long history of writing about walking as a way through which to engage the world and intervene in social scenarios. As we enter the ambiguous new epoch of the Anthropocene, and as familiar landscapes change and degrade, we need—more than ever—to pay attention, to notice, to take care. For scholars, this arguably involves leaving the ‘white cube’ of the seminar room for more materially involved and implicated forms of engagement with our research subjects. The humble, everyday act of walking offers one route towards such modes of engagement.The Aarhus University Research Foundation.https://journals.sagepub.com/home/STShj2024Anthropology and ArchaeologySDG-11:Sustainable cities and communitie

Impact of parametrized nonorographic gravity wave drag on stratosphere-troposphere coupling in the northern and southern hemispheres

The impact of parametrized nonorographic gravity wave drag (NOGWD) on the stratosphere-troposphere dynamical coupling in atmospheric models is relatively unexplored. Using the European Centre for Medium-Range Weather Forecasts Integrated Forecast System, we find that changes in NOGWD strength have a substantial impact on the tropospheric eddy-driven jet (EDJ) in both hemispheres, but the sense of the impact is opposite in the two hemispheres. In the Northern Hemisphere the impact occurs via changes in the amplitude and persistence of stratospheric anomalies. In the Southern Hemisphere (SH) it occurs instead via differences in the sensitivity of the EDJ to a given stratospheric anomaly, arising from changes in the seasonal cycle leading up to the polar vortex breakdown. Increasing NOGWD eliminates the springtime phase of the SH tropospheric semiannual oscillation (SAO), resulting in a more equatorward annual-mean EDJ, and showing that the SAO cannot be explained entirely from tropospheric mechanisms

An experimental dynamic RAM video cache

As technological advances continue to be made, the demand for more efficient distributed multimedia systems is also affirmed. Current support for end-to-end QoS is still limited; consequently mechanisms are required to provide flexibility in resource loading. One such mechanism, caching, may be introduced both in the end-system and network to facilitate intelligent load balancing and resource management. We introduce new work at Lancaster University investigating the use of transparent network caches for MPEG-2. A novel architecture is proposed, based on router-oriented caching and the employment of large scale dynamic RAM as the sole caching medium. The architecture also proposes the use of the ISO/IEC standardised DSM-CC protocol as a basic control infrastructure and the caching of pre-built transport packets (UDP/IP) in the data plane. Finally, the work discussed is in its infancy and consequently focuses upon the design and implementation of the caching architecture rather than an investigation into performance gains, which we intend to make in a continuation of the work