Permeability changes in simulated granite faults during and after frictional sliding

Thermal–hydrological–mechanical coupling processes suggest that fault permeability should undergo dynamic change as a result of seismic slip. In igneous rocks, a fault's slip surface may have much higher permeability than the surrounding rock matrix and therefore operate as a conduit for fluids. We conducted laboratory experiments to investigate changes in fracture permeability (or transmissivity) of a fault in granite due to shear slip and cyclic heating and cooling. Our experiments showed that high initial fracture transmissivity (>10^?18 m³) was associated with a high friction coefficient and that transmissivity decreased during slip. We propose that this reduction in transmissivity reflects the presence of gouge in fracture voids, increasing the area of contact in the fault plane and reducing the hydraulic aperture. In contrast, when initial fracture transmissivity was low (<10^?18 m³), we observed that friction was lower and transmissivity increased during slip. The high transmissivity and high friction may be explained by large areas of bare rock being in contact on the slip surface. Slip velocity had little influence on the evolution of permeability, probably because gouge produced at different slip velocities had similar grain size distributions, or because gouge leaked from the slip surface. Transmissivity decreased with increasing temperature in heating tests, probably due to thermal expansion increasing normal stress on the fracture. Frictional heating did not influence transmissivity during the shearing tests.     

Intellectual History and the History of Philosophy

Summary

The issue which I wish to address in this paper is the widespread tendency in Anglophone philosophy to insist on a separation between the history of philosophy and the history of ideas or intellectual history. This separation reflects an anxiety on the part of philosophers lest the special character of philosophy will be dissolved into something else in the hands of historians. And it is borne of a fundamental tension between those who think of philosophy's past as a source of ideas and arguments of interest to the present, and those who hold that the philosophy of the past should be studied on its own terms, in relation to its immediate context, without reference to the present. The challenge, then, is to re-historicise the history of philosophy, and to keep the philosophers onside.     

Stahl, Leibniz, Hoffmann et la respiration

At the beginning of the XVIII th century, Wilhelm Gottfried Leibniz and Friedrich Hoffmann criticize Georg Ernst Stahl's medical theory. They differenciate between unsound and true reasonings. Namely, they validate Stahl's definition of breath but extracting it from its animist basis and placing it in an epistemology obeying to the principle of sufficient reason and to the mechanical model. The stahlian discovery consists in understanding breath as a calorific ventilation against the ancient conception; the iatromechanists recognize its accuracy, but they try then to transpose it to a mechanical model of ventilation. Using it in a different epistemological context implies that they analyze the idea of discovery "true" in its contents, but "wrong" in its hypothesis. It impels to examine the epistemology of medical knowledge, as science and therapeutics, and in its links with the other scientific theories. Thus, if Leibniz as philosopher and Hoffmann as doctor consider Stahl's animism so important, it is because its discoveries question the fundamental principles of medicine.     

The "Mouse That Roared": Agenda Setting in Canadian Pesticides Politics

Issue redefinition and venue shopping have been identified as key strategies for enacting agenda and policy change, but much work remains to be done in elaborating these processes. I argue that an important aspect of issue redefinition involves shifting not only the image of an issue but also the bases for considering those issues—what I call policy principles. Policy principles are the core values, beliefs, or guidelines attached to policies that help direct decision making. The emergence and acceptance of new principles by the public and policymakers can be a vital source of policy change, at times having far greater consequences for policy than redefining an issue. Venue shopping is also a multifaceted undertaking involving efforts by policy entrepreneurs and advocacy groups to keep issues out of venues they would rather not participate in as well as move decision making to new arenas. Moreover, while the literature suggests that shifting venues is usually a sensible strategy, sometimes venue shopping can backfire. A case study of the municipal movement to restrict the nonessential use of lawn and garden pesticides in Canada illustrates these theoretical points and shows the applicability of agenda setting models to contexts outside the United States.     

British speleologies: geographies of science, personality and practice, 1935–1953

This paper examines historical geographies of speleology in Britain between 1935 and 1953. As the study of caves, speleology was constructed as a sporting-science. The paper traces the formation and activities of the British Speleological Association, the influence of the speleologist Eli Simpson, arguments relating to the practice of speleology, and the formation of the Cave Research Group in 1947, to examine the geographies of science that emerge through speleology. By tracing some of the spatial, social and practical issues within the histories of speleology, distinct social and regional geographies are uncovered. Debates about practising science, definitions of speleology as sporting-science and ‘the right kind of speleologist’ complicate the geographical histories of speleology within Britain. As well as emphasising the spatial outcomes of these issues, I suggest that personality can also impact upon geographies of science in profound ways.     

Behavioral Ecology and Archaeology

Behavioral ecology is the study of adaptive behavior in relation to social and environmental circumstances. Analysts working from this perspective hold that the reproductive strategies and decision-making capacities of all living organisms—including humans—are shaped by natural selection. Archaeologists have been using this proposition in the study of past human behavior for more than 30 years. Significant insights on variation in prehistoric human subsistence, life history, social organization, and their respective fossil and archaeological consequences have been among the more important results.