We explore the relation between vertexand edge-transitivity and arc-transitivity of various graphs. We exhibit several families of graphs whose vertexand edgetransitivity imply arctransitivity. In particular, we show that any vertexand edgetransitive graph with twice a prime number of vertices is arctransitive by simplifying the proof of a theorem by Cheng and Oxley, in which they classify all ...

design of the first digital computer, in the hands of John Von Neumann, was strongly influenced by this work of 1943. Von Neumann himself rejected logic as the key to human thinking. Something much more like thermodynamics, he speculated, is needed. And in 1947—only just under half a century ago—Pitts and McCulloch published “How We Know Universals: The Perception of Auditory and Visual Forms.”...

Let G and G' be multiplicative systems. A half-homomorphism of G into G' will mean a mapping a—>a' of G into C such that for all a, bEG, (ab)'=a'V or b'a'. An anti-homomorphism is a mapping such that always (ab)' = b'a'. The terms half-isomorphism, etc., are defined similarly. It will be shown that any half-homomorphism of a group G into a group G' is either a homomorphism or an anti-homomorphi...

In an instance G = (A∪B,E) of the stable marriage problem with strict and possibly incomplete preference lists, a matchingM is popular if there is no matchingM ′ where the vertices that prefer M ′ to M outnumber those that prefer M to M ′. All stable matchings are popular and there is a simple linear time algorithm to compute a maximum-size popular matching. More generally, what we seek is a mi...

Prior to the 2007–2008 financial crisis, banking sector profits were very high but the profitability of financial intermediation was poor. Using a novel model of banking, this article argues that the high profits were achieved through balance sheet expansion and growing default, liquidity, and term risk mismatches between assets and liabilities. As a result, large banks’ financial leverage rose...

This paper presents new evidence that immigrants have better health than natives upon arrival to their destination. It analyzes a very interesting episode in international migration, namely the exodus of Ecuadorians in the aftermath of the economic collapse in the late 1990s. More than 600,000 Ecuadorians from 1999 to 2005 left their homeland, most relocating in Spain. Using information from th...

Recent! research! in!both! the! social! and!natural! sciences!has!been!devoted! to! increasing!our! ability!to!predict!disasters,!prepare!for!them!and!mitigate!their!costs.!Curiously,!we!appear!to! know!very!little!about!the!fiscal!consequences!of!disasters.!The!likely!fiscal!impact!of!a!natural! disaster! has! not! been! examined! before! in! any! comparable! or! comparative! framework.! We! e...

The highly diffuse nature of light propagation in biological tissue is a major challenge for obtaining high-fidelity fluorescence tomographic images. In this work we investigated the use of time-gated detection of early-arriving photons for reducing the effects of light scatter in mice relative to quasi-cw photons. When analyzing sinographic representations of the measured data, it was determin...