Cusps of lattices in rank 1 Lie groups over local fields

Let G be the group of rational points of a semisimple algebraic group of rank 1 over a nonarchimedean local field. We improve upon Lubotzky's analysis of graphs of groups describing the action of lattices in G on its Bruhat-Tits tree assuming a condition on unipotents in G. The condition holds for all but a few types of rank 1 groups. A fairly straightforward simplification of Lubotzky's definition of a cusp of a lattice is the key step to our results. We take the opportunity to reprove Lubotzky's part in the analysis from this foundation.Comment: to appear in Geometriae Dedicat

An Ontological Basis for Design Methods

This paper presents a view of design methods as process artefacts that can be represented using the function-behaviour-structure (FBS) ontology. This view allows identifying five fundamental approaches to methods: black-box, procedural, artefact-centric, formal and managerial approaches. They all describe method structure but emphasise different aspects of it. Capturing these differences addresses common terminological confusions relating to methods. The paper provides an overview of the use of the fundamental method approaches for different purposes in designing. In addition, the FBS ontology is used for developing a notion of prescriptiveness of design methods as an aggregate construct defined along four dimensions: certainty, granularity, flexibility and authority. The work presented in this paper provides an ontological basis for describing, understanding and managing design methods throughout their life cycle. Keywords: Design Methods; Function-Behaviour-Structure (FBS) Ontology; Prescriptive Design Knowledge</p

Stochastic thermodynamics of single enzymes and molecular motors

For a single enzyme or molecular motor operating in an aqueous solution of non-equilibrated solute concentrations, a thermodynamic description is developed on the level of an individual trajectory of transitions between states. The concept of internal energy, intrinsic entropy and free energy for states follows from a microscopic description using one assumption on time-scale separation. A first law energy balance then allows the unique identification of the heat dissipated in one transition. Consistency with the second law on the ensemble level enforces both stochastic entropy as third contribution to the entropy change involved in one transition and the local detailed balance condition for the ratio between forward and backward rates for any transition. These results follow without assuming weak coupling between the enzyme and the solutes, ideal solution behavior or mass action law kinetics. The present approach highlights both the crucial role of the intrinsic entropy of each state and the physically questionable role of chemiostats for deriving the first law for molecular motors subject to an external force under realistic conditions.Comment: 11 page

Landuse and enviromental change in the Lake Chad Basin of Nigeria

The Lake Chad Basin is a major geographical region in the central part of the Sudan zone of Africa. The northern parts, however, extend into the Sahel and the southern parts of the Sahara desert. It consists of an extensive shallow depression of about 1.536.000 km2 (600.000 miles2) of which about 10% lies in Nigeria. The greater part is shared between the three countries of Cameroon, Chad and Niger. Climatically and agriculturally, the Chad Basin lies within the dry or semi-arid zone of Nigeria. It is a marginal area which has experienced severe droughts and considerable environmental changes in recent years. The natural environment, its use and misuse, and the threat of life posed by environmental pollution dominate discussions on environmental change. But in addition to the natural or physical environment, there are other equally important 'environments' which deserve some attention in view of the role that they play in generating economic growth and in ensuring sustainable development which is the central issue in our concern about the environment. These other environments are the cultural environment, the political environment and the economic environment, both internal and external. In the Chad Basin, all these other environments, along with the natural environment have been greatly influenced by its land locked location in the heart of Africa

The Vitality of Yoruba Culture in the Americas

How did Africans create homes for themselves and maintain ancestral practices after being forcefully taken across the Middle Passage as enslaved people into various regions of the New and Old Worlds? In the Americas, they found themselves in a place clearly distinct from African cultural and geographical landscapes and were forced to adapt to strange climates and contend with alien cultures unfamiliar to those of their homeland. Rather than being completely steamrolled by colonial pressure, however, Africans of various ethnicities actively contended with the diverse influences of the colonial context. Such practices have, in turn, shaped the continued cultural diversity of the Americas to this day. This paper explores the diffusion and vitality of Yoruba culture, in particular throughout the nineteenth century in Brazil, Haiti, Cuba, and Trinidad and Tobago, where Yoruba forms of religion, Roman Catholic sensibilities, and indigenous cosmographies formed hybridized spiritualties and worldviews. This paper interprets historical evidence alongside secondary sources and contemporary cases in order to evaluate how the conjunctural forces brought about by slavery, colonialism, and inter-culturation occasioned the formation of Yoruba Atlantic and Afro-Latinx religions such as Candomble, Santeria, and Voodoo, as well as Orisha practices. This paper also examines how such spiritualties and worldviews have contributed to the complex social and cultural composition of the Americas in the modern world. It pays special attention to the conflictual and creative energies surrounding cultural diffusion and cross-cultural migration. Although various African ethnicities were brought across the Atlantic, Yoruba cultural practices have survived with a sustained intensity