Choice of routes in congested traffic networks: Experimental tests of the Braess Paradox

The Braess Paradox consists of showing that, in equilibrium, adding a new link that connects two routes running between a common origin and common destination may raise the travel cost for each network user. We report the results of two experiments designed to study whether the paradox is behaviorally realized in two simulated traffic networks that differ from each other in their topology. Both experiments include relatively large groups of participants who independently and repeatedly choose travel routes in one of two types of traffic networks, one with the added links and the other without them. Our results reject the hypothesis that the paradox is of marginal value and its force diminishes with experience. Rather, they strongly support the alternative hypothesis that with experience in traversing the networks financially motivated players converge to choosing the equilibrium routes in the network with added capacity despite sustaining a sharp decline in earnings.Braess Paradox Congested traffic networks Route choice Experiments

Yolk sac-derived murine macrophage cell line has a counterpart during ES cell differentiation

Macrophages are phagocytic hematopoietic cells involved in several immune processes, but they are also present early in mammalian development and may participate in embryonic tissue remodeling. We have isolated and characterized a cell line, Py-YSA, from the mouse yolk sac. Py-YSA cells have several functional properties of macrophages, including uptake of acetylated low density lipoprotein and phagocytic capability. They express the murine macrophage markers F4/80 and Mac-1, and they express RNA for the c-fms receptor. Their expansion in culture requires fibroblast conditioned medium or exogenous monocyte-colony stimulating factor. Murine ES (embryonic stem) cell cultures that undergo in vitro differentiation recapitulate yolk sac development, and during this process cells arise that express both Mac-1 and F4/80 and morphologically resemble the Py-YSA cells. The kinetics and distribution pattern of the Mac-1+ cells during a time course of ES cell differentiation suggest that they originate in the blood islands, and that they subsequently leave the blood islands and disperse to tissue sites. Both F4/80 and Mac-1 are first expressed in primary cultures from day 9.5 yolk sacs. The Py-YSA cultured cells thus resemble embryonic tissue macrophages by several criteria, and they share a marker profile with a cell type found in yolk sacs and differentiating ES cells. Py-YSA cells will be a useful reagent for further understanding the role of embryonic tissue macrophages in development