Cassiopeia A and its Clumpy Presupernova Wind

The observed shock wave positions and expansion in Cas A can be interpreted in a model of supernova interaction with a freely expanding stellar wind with a mass loss rate of ~3e-5 Msun/yr for a wind velocity of 10 km/s. The wind was probably still being lost at the time of the supernova, which may have been of Type IIn or IIb. The wind may play a role in the formation of very fast knots observed in Cas A. In this model, the quasi-stationary flocculi (QSFs) represent clumps in the wind, with a density contrast of several 1000 compared to the smooth wind. The outer, unshocked clumpy wind is photoionized by radiation from the supernova, and is observed as a patchy HII region around Cas A. This gas has a lower density than the QSFs and is heated by nonradiative shocks driven by the blast wave. Denser clumps have recombined and are observed as HI compact absorption features towards Cas A.Comment: 13 pages, ApJL, in pres

Graptemys barbouri

Number of Pages: 2Integrative BiologyGeological Science

Market participation and marketing performance: A case study of Bolivian potato farmers

Agribusiness, Marketing,

TAXATION: NO SIMPLE ANSWERS

Public Economics,

SUPPLY AND DEMAND FOR MARRIED FEMALE LABOR: RURAL AND URBAN DIFFERENCES IN THE SOUTHERN UNITED STATES

This study examined the supply of and demand for married female labor in the southern United States. Special attention was given to differences in labor force participation, labor supply, and quantities of labor supplied and demanded across rural and urban areas. Once state effects were accounted for, decisions to change participation were found not to vary by urban-rural designation. Differences in demand were fully captured by an intercept shifter and the variations in hours supplied by married females between urban and rural areas. Labor supply varied greatly with the effects of key determinants (number of children, work force experience, family income) being strongly different in rural areas. Different policies are needed to promote female labor supply in rural areas as opposed to urban areas.Community/Rural/Urban Development, Labor and Human Capital,

Those with blue hair please step forward: An economic theory of group formation and application to Cajas Rurales in Honduras

This paper presents an economic model of group formation with an application to data collected from an agricultural credit program in western Honduras. We formulate a simple theory of group formation using the concept of centers of gravity to explain why individuals join a group. According to our theory, prospective members join based on the potential benefits and costs of group membership, and based on their perception of social distance between themselves and other group members. Social distance is unobservable by outsiders but known by the individual: if you are in then you know who has blue hair. Thus, we argue that social distance helps explain preferences for group formation. To test our theory we analyze data collected from members and non-members of PRODERT, a program that has helped create 188 “Cajas Rurales” (CRs). Using conjoint analysis we test for differences in preferences between members and non-members for the main attributes of the CR. We find that members and non-members exhibit similar preferences for the attributes of the CR; therefore non-membership is not related to supply factors. Using information gathered by executing field experiments, we estimate a proxy for social distance. We use this proxy to run a group formation equation and find that it explains, along with individual characteristics, participation in the CR. Finally we offer suggestions on how to balance performance and coverage in programs in which beneficiaries decide who joins. Small cohesive groups may show exceptional performance at the cost of low coverage, and the opposite may be true.Agricultural Finance, Institutional and Behavioral Economics,

Terrestrial glacial eskers: Analogs for Martian sinuous ridges

A glacial model was introduced last year for the Argyre region, a concept which is now extended, and which was recently integrated with a Global Hydrologic Model incorporating many other aspects of Martian geology. Despite wide agreement that the Martian ridges strongly resemble glacial eskers, this hypothesis has been presented with great equivocation due to a perceived lack of other glacial landforms. Quite to the contrary, it is shown that the Martian ridges actually do occur in logical ordered sequences with many other types of characteristically glacial appearing landforms. Herein, the esker hypothesis is further supported in isolation from considerations of regional landform assemblages. It is concluded that Martian sinuous ridges are similar in every respect to terrestrial eskers: scale, morphology, planimetric pattern, and associations with other probable glaciogenic landforms. It is found that the esker hypothesis is well supported. Eskers are glaciofluvial structures, and owe their existence to large scale melting of stagnant temporate glaciers. Thus, eskers are indicators of an ameliorating climatic regime after a protracted episode of cold, humid conditions

Graptemys pearlensis

Number of Pages: 4Integrative BiologyGeological Science