Transient fluid flow in and around a fault

We present the results of simple numerical experiments in which we study the evolution with time of fluid flow around and within a permeable fault embedded in a less permeable porous medium. Fluid movement is driven by an imposed vertical pressure gradient. The results show that fluid flow is controlled by two timescales: τ_f = Sl²/κ_F and τ_F = Sl²/κ_M, where S is the specific storage of the porous material, l the length of the fault, and κ_M and κ_F are the hydraulic conductivities of the porous material and the fault, respectively. Fluid flow and the associated fluid pressure field evolve through three temporal stages: an early phase [t < τ_f] during which the initial fluid pressure gradient within the fault is relaxed; a second transient stage [τ_f < t < τ_F] when fluid is rapidly expelled at one end of the fault and extracted from the surrounding rocks at the other end leading to a reduction in the pressure gradient in the intact rock; a third phase [t < τ_F] characterized by a steady‐state flow. From the numerical experiments we derive an expression for the steady‐state maximum fluid velocity in the fault and the values of the two timescales, τ_f and τ_F. A comparison indicates excellent agreement of our results with existing asymptotic solutions. For km‐scale faults, the model results suggest that steady‐state is unlikely to be reached over geological timescales. Thus, the current use of parameters such as the focusing ratio defined under the assumption of steady‐state conditions should be reconsidered.     

Commentary: Martians and Venutians in the new world order

One of the most significant results of 9/11 has been to provoke the most serious crisis in the transatlantic relationship—the subject of Robert Kagan's influential and provocative treatise. Lauded by some as one of the more important contributions to the study of world politics in recent years and attacked by others as possibly the most misguided analysis of European—American relations ever, Kagan sets forth in stark, realist terms why the rift is serious, long-term and unlikely to be overcome by neat diplomatic footwork. However, as this commentary seeks to show, if Kagan is right there is little chance of constructing anything like a 'new world order'. Moreover, if the clash continues, far from enhancing American power in the world, it is more likely to weaken it.     

The impact of broadband and other infrastructure on the location of new business establishments

This paper analyzes the impact of broadband infrastructure, along with a range of other local characteristics such as motorways and other infrastructure, availability of human capital, and access to third‐level educational facilities, on the location of new business establishments. The sample period spans the introduction and recent history of broadband in Ireland. The results indicate that the availability of broadband infrastructure is a significant determinant, but its effects may be mediated by the presence of sufficiently high human capital in an area.     

“Half Bacchanalian,Half Devout”: White Intellectuals,Black Folk Culture,and the “Negro Problem”

In the wake of the Civil War, white Americans generated an unprecedented amount of writing about the songs, stories, and “superstitions” of black southerners. This interest was not purely esthetic. In the late nineteenth century, folk culture was commonly conceptualized as a gauge of racial character and potential; in consequence, discourse on black folklore was entangled with the debate on the social and political place of African Americans. A number of scholars have noted the ways in which white supremacy was bulwarked by the work of folklorists, ethnologists, local color writers, and other intellectuals. The variety and contingency of this discourse on race, however, has sometimes been obscured, giving the impression of a static and monolithic racial ideology. Ideas about black folk culture shifted over time, shaped by a range of racial attitudes encompassing a liberal emphasis on uplift, a conservative commitment to stasis, and a radical insistence on regression. Moreover, the racial politics of intellectuals determined not only the ways in which they represented black folk culture, but also the particular cultural forms about which they wrote. Thus, while the Christian content of the “spirituals” suited the agenda of liberal reformers, the supposedly sinister figure of the conjure doctor complemented radical discourse on dangerous racial degeneration.