Ramsey’s theorem says that for every clique H1 and for every graph H2 with no edges, all graphs containing neither of H1, H2 as induced subgraphs have bounded size. What if, instead, we exclude a graph H1 with a vertex whose deletion gives a clique, and the complement H2 of another such graph? This no longer implies bounded size, but it implies tightly restricted structure that we describe. The...

Many intelligent tutoring systems (ITSs) offer feedback and guidance through structured dialogs with their students, which often take the form of a sequence of hints. However, it is often difficult to replicate the complexity and responsiveness of human conversation with current natural language understanding and production technologies. Although ITSs reveal enough information to continue solvi...

Constructing structurally complex reservoir models at the appraisal stage is a complex task, with a high-degree of uncertainty. The lack of an intuitive set of modeling and visualization tools that support expert visual interpretation from geophysicists and geologists significantly increases the challenge. We present a set of interactive software tools to reservoir modeling in the appraisal sta...

It was a hot humid morning as always in the small village of Amokwasuaso in Ghana’s western region. We sat in the small, dilapidated community meeting hall awaiting the arrival of a World Bank fact-finding mission. The Amokwasuaso community has achieved some celebrity in Ghana as the first community to have the rights to manage wildlife devolved to its residents by the State. The fact-finding m...

We study the Gilbert-Shannon-Reeds model for riffle shuffles and ask ’How many times must a deck of cards be shuffled for the deck to be in close to random order?’. In 1992, Bayer and Diaconis gave a solution which gives exact and asymptotic results for all decks of practical interest, e.g. a deck of 52 cards. But what if one only cares about the colors of the cards or disregards the suits focu...

n the current debates around evaluation, quasi-experimental methods are considered by some to be the best way to know what works. They view narrative-based evaluation with some disdain. Stories are, they say, only perceptions. They can’t give you the ‘hard facts and figures’ that are needed to know what works and what to do next. And a handful of stories, no matter how in-depth, cannot lead to ...

introduction: the term glaucoma refers to a group of diseases that have a characteristic optic neuropathy with associated visual field loss in common. intraocular pressure has been considered to be the only causal factor for glaucoma and the only factor that can be manipulated to alter the course of the disease. but considering high intraocular pressure as the only factor responsible for glauco...

Software measurement has the potential to play an important role in risk management during product development. Metrics incorporated into predictive models can give advanced warning of potential risks. However, the common approach of using simple regression models, notably to predict software defects, can lead to inappropriate risk management decisions. These naïve models should be replaced wit...

What are the limits of physics’ explanatory power? Can physics explain everything? In this paper I discuss a somewhat broader question: can physics explain existence itself? I argue that genuinely ultimate explanations—those that really explain everything—involve the most basic and most general elements of logic. Such explanations cannot be done within physics unless physics undergoes a methodo...

In this work the authors develop a mathematical model for the dynamics of a major helminth parasite of man, schistosomiasis. The model is a system of coupled non-linear equations. Numerical experimentations with the model reveal the remarkable stability of the dynamics of schistosomiasis. The steady state is invariably reached within 10-15 years of the start of the infection. A numerical soluti...