Surfaces with triple points

In this paper we compute upper bounds for the number of ordinary triple points on a hypersurface in $P^3$ and give a complete classification for degree six (degree four or less is trivial, and five is elementary). But the real purpose is to point out the intricate geometry of examples with many triple points, and how it fits with the general classification of surfaces

The impact of altered management on long-term agricultural soil carbon stocks

Land use in general and particularly agricultural practices can significantly influence soil carbon storage. In this paper, we investigate the long-term effects of management changes on soil carbon stock dynamics on a Swedish farm where C concentrations were measured in 1956 at 124 points in a regular grid. The soil was re-sampled at 65 points in 1984 and at all grid points in 2001. Before 1956 most of the fodder for dairy cattle was produced on the farm and crop rotations were dominated by perennial grass leys and spring cereals with manure addition. In 1956 all animals were sold, crop rotations were thereafter dominated by wheat, barley and rapeseed. Spatial variation in topsoil C concentration decreased significantly between 1956 and 2001. C stocks declined in fields with initially large C stocks but did not change significantly in fields with moderate C stocks. In the latter fields, soil C concentrations declined from 1956 to 1984, but increased slightly thereafter according to both measurements and simulations. Thus, the decline in C input due to the altered management in 1956 was partly compensated for by increasing crop yields and management changes, resulting in increased C input during the last 20 years. A soil carbon balance model (ICBM) was used to describe carbon dynamics during 45 years. Yield records were transformed to soil carbon input using allometric functions. Topsoil C concentrations ranging between 1.8 and 2.4% (depending on individual field properties) seemed to be in dynamic equilibrium with C input under recent farming and climatic conditions. Subsoil C concentrations seemed to be unaffected by the management changes

Quantum hypermultiplet moduli spaces in N=2 string vacua: a review

The hypermultiplet moduli space M_H in type II string theories compactified on a Calabi-Yau threefold X is largely constrained by supersymmetry (which demands quaternion-K\"ahlerity), S-duality (which requires an isometric action of SL(2, Z)) and regularity. Mathematically, M_H ought to encode all generalized Donaldson-Thomas invariants on X consistently with wall-crossing, modularity and homological mirror symmetry. We review recent progress towards computing the exact metric on M_H, or rather the exact complex contact structure on its twistor space.Comment: 31 pages; Contribution to the Proceedings of String Math 2012; v2: references added, misprints corrected, published versio

Regions as Security Providers: The Evolution of the West African Regional Security Complex

The purpose of this thesis is to explore the region in its role as a regional security provider through a within-case study of West Africa. The point of departure is on one hand that contemporary threats to international peace and security are increasingly regional, arising within states rather than from a global or out-of-region origin, and on the other hand that the regions among the world has become salient security providers. The theoretical and epistemological basis rests on social constructivist concepts and theories on the evolution of the West African Regional Security Complex. I have found that the processes of securitisation and desecuritisation among the states in West Africa are so interlinked that their security problems cannot reasonably be analysed or resolved apart from one another. The security interdependence between the states has been highly dependent on de jure changes in distribution of power, shifts in the pattern of amity and enmity, and alternations in penetration of external actors. Three characteristics have continued to hamper the evolution of the security complex: (i) the weak state capacity of its members resulting in a gap between agreed norms and rules of conduct, and institutional capacity and resources; (ii) the principles of state sovereignty and search for consensus in regional decision-making blocking collective conflict prevention and management; (iii) the phenomenon of presidentialism and prevailing pattern of executive dominance in member states and its repercussions on regional decision-making

The Pursuit of the Source, or The Inevitability of Death

The purpose of this article is to apply the method of the genre of studying chains of references to an instance of a secondary source of the contested concept of ‘resistance to change’ back to the primary source and thereby exercise criticism of the sources. This includes discussing whether the theory itself is empirically sustainable or sufficiently scientifically grounded. In the article, we adopt a theoretical lens of Critical Realist Discourse Analysis, mainly because it is sensitive to the importance of the influence of nondiscursive social positions on discourses. The primary source of the chain of theories of resistance to change turns out to be Kübler-Ross’s model of stages of dying patients’ reactions to their immanent death. We find that the model is systematically mis-interpreted to fit the empirically false idea of resistance to change of the ideological discourses of management research.publishedVersio

The British Free Jazz Movement

Photocopied article from the English newspaper The Post about Chris McGregor's Brotherhood of Breath and its free jazz style. There is a picture of Dudu Pukwana and 3 other saxophonists playing on stage