Henri Poincaré: The Status of Mechanical Explanations and the Foundations of Statistical Mechanics

The first goal of this paper is to show the evolution of Poincaré’s opinion on the mechanistic reduction of the principles of thermodynamics, placing it in the context of the science of his time. The second is to present some of his work in 1890 on the foundations of statistical mechanics. He became interested first in thermodynamics and its relation with mechanics, drawing on the work of Helm-holtz on monocyclic systems. After a period of skepticism concerning the kinetic theory, he read some of Maxwell’s memories and contributed to the foundations of statistical mechanics. I also show that Poincaré's contributions to the founda-tions of statistical mechanics are closely linked to his work in celestial mechanics and its interest in probability theory and its role in physics

Are Women Who Work in Bars, Guesthouses and Similar Facilities a Suitable Study Population for Vaginal Microbicide Trials in Africa?

BACKGROUND: A feasibility study was conducted to investigate whether an occupational at-risk cohort of women in Mwanza, Tanzania are a suitable study population for future phase III vaginal microbicide trials. METHODOLOGY/PRINCIPAL FINDINGS: 1573 women aged 16-54 y working in traditional and modern bars, restaurants, hotels, guesthouses or as local food-handlers were enrolled at community-based reproductive health clinics, provided specimens for HIV/STI and pregnancy testing, and asked to attend three-monthly clinical follow-up visits for 12-months. HIV positive and negative women were eligible to enter the feasibility study and to receive free reproductive health services at any time. HIV prevalence at baseline was 26.5% (417/1573). HIV incidence among 1156 sero-negative women attending at baseline was 2.9/100PYs. Among 1020 HIV sero-negative, non-pregnant women, HIV incidence was 2.0/100PYs, HSV-2 incidence 12.7/100PYs and pregnancy rate 17.8/100PYs. Retention at three-months was 76.3% (778/1020). Among 771 HIV sero-negative, non-pregnant women attending at three-months, subsequent follow-up at 6, 9 and 12-months was 83.7%, 79.6%, and 72.1% respectively. Older women, those who had not moved home or changed their place of work in the last year, and women working in traditional bars or as local food handlers had the highest re-attendance. CONCLUSIONS/SIGNIFICANCE: Women working in food outlets and recreational facilities in Tanzania and other parts of Africa may be a suitable study population for microbicide and other HIV prevention trials. Effective locally-appropriate strategies to address high pregnancy rates and early losses to follow-up are essential to minimise risk to clinical trials in these settings

Species : towards new, well-grounded practices

Velasco recently criticized our formal definition of the species concept, arguing for its inappropriateness both in fundamental and practical aspects [Velasco JD (2008) Biological Journal of the Linnean Society, 93, 865-869]. Here, we clarify some misunderstandings that are at the basis of Velasco's paper. First, we show why and how the definition of the species concept can be grounded in the theory of evolution and what that implies. Then, we explain why Velasco's formal criticisms are unjustified. Finally, we point out the practical and methodological consequences of a rigorous conceptual framework for species study, and we show that today's development of species delimitation methods fully agrees with our proposal

Computer simulations and empirical data

Book synopsis: Computer simulations have become a central tool for scientific practice. Their use has replaced, in many cases, standard experimental procedures. This goes without mentioning cases where the target system is empirical but there are no techniques for direct manipulation of the system, such as astronomical observation. To these cases, computer simulations have proved to be of central importance. The question about their use and implementation, therefore, is not only a technical one but represents a challenge for the humanities as well. In this volume, scientists, historians, and philosophers join to examine computer simulations in scientific practice. One central aim of the volume is to provide a multi-perspective view on the topic. Therefore, the text includes philosophical studies on computer simulations, as well as case studies from simulation practice, and historical studies of the evolution of simulations as a research method. The theoretical studies in this book discuss the epistemological relation between simulations and experiments as well as the empirical or non-empirical status of data resulting from computer simulations. The role of simulations in current scientific practice is examined in the cases of astronomy, system biology, nanoscale research, and in the pharmaceutical industry. The historical perspective is brought in by examining the rise of supercomputing as well as the exploding number of published simulation studies in some scientific fields. The book concludes with critical reflections on the potential, limitations, and failures of computer simulations

The tree, the network, and the species

To enrich the Hennigian internodal conception of species, a new formalization of the definition of the species concept is proposed. This rigorous definition allows for considerable unification of the various, and sometimes conflicting, techniques of species delimitation used in practice. First, the domain of such a definition is set out, namely, the set of all organisms on Earth, past, present, and future. Next, the focus is on the genealogical relationship among organisms, which provides the key to analysing the giant or global genealogical network (GGN) connecting all these organisms. This leads to the construction of an algorithm revealing the topological structure of the GGN, from families to lineages, ending up with a definition of species as equivalence classes of organisms corresponding to branches of the 'tree of life'. Such a theoretical definition of the species concept must be accompanied by various recognition criteria to be operational. These criteria are, for example, the ill-named 'biological species concepts', 'phylogenetic species concepts', etc., usually, but wrongly, presented as definitions of the species concept. Besides clarifying this disputed point, the definition in the present study displays the huge diversity of the scales (time-scale and population size) involved in actual species, thus explaining away the classical problems raised by previous attempts at defining the species concept (uniparental reproduction, temporal depth of species, and hybridization). (c) 2006 The Linnean Society of London

Species from Darwin onward

Controversy regarding the species problem has been going on for many decades and no consensus has ever been reached about what a "species" really is and how best to define the concept. De Queiroz (1998) introduced a distinction between two aspects of this problem: on the one hand, the definition proper, and on the other, the criteria allowing biologists to recognize species in practice. This distinction is a first step on the way toward a solution of the problem. In the present paper, we show that de Queiroz's distinction is made possible by the radical theoretical change introduced by Darwin. We emphasize that the species problem did not appear in the 20(th) century, but long before, and that Darwin addresses it indirectly in the Origin of Species. It might seem paradoxical to refer to Darwin's views about species, because they are usually considered as unclear. However, we propose that an analysis of these views in the context of Darwin's own theory of evolution might reveal how a definition of the concept of species is made possible by being anchored to the very theory of evolution. To this aim, we present a plausible reconstruction of Darwin's implicit conception of species and show how this conception fits with the debates on species that took place in the 18(th) and 19(th) centuries. We then turn to today's biology and show what changes Darwin's implicit conception of species has brought about relative to the species concept and species delimitation

The Ontology of Theoretical Modelling: Models as Make-Believe

The descriptions and theoretical laws scientists write down when they model a system are often false of any real system. And yet we commonly talk as if there were objects that satisfy the scientists’ assumptions and as if we may learn about their properties. Many attempt to make sense of this by taking the scientists’ descriptions and theoretical laws to define abstract or fictional entities. In this paper, I propose an alternative account of theoretical modelling that draws upon Kendall Walton’s ‘make-believe’ theory of representation in art. I argue that this account allows us to understand theoretical modelling without positing any object of which scientists’ modelling assumptions are true

Le changement scientifique

To present recent developments, it covers both matters under the general philosophy of scientific activity ( what is a scientific explanation ? Unity of science is it a myth or an ideal ? . .. ) than those on the epistemology of particular sciences ( what is it mathematics are they studying ? economics an empirical science like the others? ... ) . It is clear , for students of Bachelor 3 and Master in philosophy and science , a course of deepening their support but also preparedness epistemology of scientific tests CAPES . It will also help doctoral students and established researchers who wish to expand or update their knowledge in this area