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Recently external memory graph problems have received considerable attention because massive graphs arise naturally in many applications involving massive data sets. Even though a large number of I/O-efficient graph algorithms have been developed, a number of fundamental problems still remain open. The results in this paper fall in two main classes. First(More)
As detailed terrain data becomes available, GIS terrain applications target larger geographic areas at finer resolutions. Processing the massive data involved in such applications presents significant challenges to GIS systems and demands algorithms that are optimized both for data movement and computation. In this paper we develop efficient algorithms for(More)
The potential and use of Geographic Information Systems is rapidly increasing due to the increasing availability of massive amounts of geospatial data from projects like NASA's Mission to Planet Earth. However, the use of these massive datasets also exposes scalability problems with existing GIS algorithms. These scalability problems are mainly due to the(More)
This paper describes the design and engineering of algorithms for computing visibility maps on massive grid terrains. Given a terrain <i>T</i>, specified by the elevations of points in a regular grid, and given a <i>viewpoint v</i>, the <i>visibility map</i> or <i>viewshed</i> of <i>v</i> is the set of grid points of <i>T</i> that are visible from <i>v</i>.(More)
We provide I/O-efficient algorithms for diameter and allpairs shortest-paths (APSP) on undirected graphs G(V,E). For general non-negative edge weights and E/V = o(B/ log V ) our approaches are the first to achieve o(V ) I/Os. We also show that unweighted APSP can be solved with just O(V · sort(E)) I/Os; these approaches require O(V ) space. For diameter(More)
As detailed terrain data becomes available, GIS terrain applications target larger geographic areas at finer resolutions. Processing the massive datasets involved in such applications presents significant challenges to GIS systems and demands algorithms that are optimized for both data movement and computation. In this paper we present efficient algorithms(More)
Even though a large number of I/O-efficient graph algorithms have been developed, a number of fundamental problems still remain open. For example, no spaceand I/O-efficient algorithms are known for depth-first search or breath-first search in sparse graphs. In this paper, we present two new results on I/O-efficient depth-first search in an important class(More)
Given an arbitrary viewpoint <i>v</i> and a terrain, the visibility map or viewshed of <i>v</i> is the set of points in the terrain that are visible from <i>v</i>. In this article we consider the problem of computing the viewshed of a point on a very large grid terrain in external memory. We describe algorithms for this problem in the cache-aware and(More)
In diabetes, hyperglycemia and the associated formation of advanced glycation end-products (AGE) and AGE-modified low density lipoproteins (AGE-LDL) can directly affect the cells of the vascular wall. We hypothesize that AGE-LDL may act directly and induce oxidant and inflammatory alterations in human endothelial cells (HEC), this effect being amplified by(More)
Amlodipine, alone or in combination with other drugs, was successfully used to treat hypertension. Our aim was to evaluate the potential of amlodipine (Am) to restore endothelial dysfunction induced by irreversibly glycated low density lipoproteins (AGE-LDL), an in vitro model mimicking the diabetic condition. Human endothelial cells (HEC) from EA.hy926(More)