Corner and finger formation in Hele--Shaw flow with kinetic undercooling regularisation

We examine the effect of a kinetic undercooling condition on the evolution of a free boundary in Hele--Shaw flow, in both bubble and channel geometries. We present analytical and numerical evidence that the bubble boundary is unstable and may develop one or more corners in finite time, for both expansion and contraction cases. This loss of regularity is interesting because it occurs regardless of whether the less viscous fluid is displacing the more viscous fluid, or vice versa. We show that small contracting bubbles are described to leading order by a well-studied geometric flow rule. Exact solutions to this asymptotic problem continue past the corner formation until the bubble contracts to a point as a slit in the limit. Lastly, we consider the evolving boundary with kinetic undercooling in a Saffman--Taylor channel geometry. The boundary may either form corners in finite time, or evolve to a single long finger travelling at constant speed, depending on the strength of kinetic undercooling. We demonstrate these two different behaviours numerically. For the travelling finger, we present results of a numerical solution method similar to that used to demonstrate the selection of discrete fingers by surface tension. With kinetic undercooling, a continuum of corner-free travelling fingers exists for any finger width above a critical value, which goes to zero as the kinetic undercooling vanishes. We have not been able to compute the discrete family of analytic solutions, predicted by previous asymptotic analysis, because the numerical scheme cannot distinguish between solutions characterised by analytic fingers and those which are corner-free but non-analytic

The effect of credit scoring on small business lending in low- and moderate-income areas

This paper empirically examines the effect of the use of credit scoring by large banking organizations on small business lending in low- and moderate-income (LMI) areas. Using census tract level data for the southeastern United States, the authors estimate that credit scoring increases small business lending by $16.4 million per LMI area served. Furthermore, this effect is almost 2.5 times larger than that estimated for higher income census tracts ($6.8 million). The authors also find that credit scoring increases the probability that a large banking organization will make small business loans in a given census tract. The change in this probability is 3.8 percent for LMI areas and 1.7 percent for higher income areas. These findings suggest that credit scoring reduces asymmetric information problems for borrowers and lenders and that this is particularly important for LMI areas, which lenders may have historically bypassed because of their questionable economic health.Credit scoring systems ; Bank loans ; Commercial loans ; Small business

Book review: anthropological cosmochemistry

Beyond Nature and Culture By Philippe Descol

Getting more real with wonder: an afterword

This Afterword is part apologia for an ontology-centred approach to the anthropology of wonder, part diplomatic mission to bring the articles in this special issue into dialogue to yield new insights about wonder. The latter endeavor identifies five key areas in which the articles enhance understanding about wonder. First, they help to clarify the relationship between wonder and socio-political change. Second, they present ethnographic examples of what makes wonder practices work. Elsewhere, I have suggested that wonder can be a practice through which people resist existing ontological premises and advance lived alternatives. Going beyond this observation, these articles disclose how wonder practices persist and become routinized. Third, these articles not only show how wonder confers authority, they also show that the authority wonder confers is ontological authority—authority to lay down or revise ontological premises and their ethical and political implications. Fourth, the articles attest that wonder engages our received imagery and discourses about origins and stimulates us to generate new versions that revise, replace, or compete with the old. A fifth issue raised is whether nonhumans can wonder. Pushing against anthropocentric tendencies in some of the contributions, I suggest how we might imagine a nonhuman affective cognate to wonde