For a polygon P with n vertices, the vertex guarding problem asks for the minimum subset G of P ’s vertices such that every point in P is seen by at least one point in G. This problem is NP-complete and APX-hard. The first approximation algorithm (Ghosh, 1987) involves decomposing P into O ( n ) cells that are equivalence classes for visibility from the vertices of P . This discretized problem ...

We propose a new model of realistic input: k-guardable objects. An object is k-guardable if its boundary can be seen by k guards in the interior of the object. In this abstract, we describe a simple algorithm for triangulating k-guardable polygons. Our algorithm, which is easily implementable, takes linear time assuming that k is constant.

—This paper analyzes the current status of power production safety, introduces the realization principle of intelligent working guarding system in substations, and delves into the technologies of positioning and intelligent video analysis based on ultra wideband (UWB) technology and high resolution digital spatial data of the substations. Based on the acquired data, an intelligent working moni...

Abstract Salmonine fishes are generally thought not to exhibit male parental care, although brief post-spawning mate-guarding by males is known for a number of species, often populations where eggs subjected intense predation (egg cannibalism). Here, detailed in situ data on the spawning behaviour brook charr, Salvelinus fontinalis , from naturally reproducing lake population used test whether ...

Background: Clinical information about stroke in the vertebrobasilar territory has lagged behind that for anterior circulation syndrome. This is the first report from posterior circulation syndrome registry in Iran. Methods: Consecutive patients with brain infarction in vertebrobasilar territory admitted to Ghaem hospital, Mashhad were enrolled in a prospective study during 2006-2007. Diagnosis...

It has been believed that XIST RNA requires a discrete window in early development to initiate the series of chromatin-remodeling events that form the heterochromatic inactive X chromosome. Here we investigate four adult male HT-1080 fibrosarcoma cell lines expressing ectopic human XIST and demonstrate that these postdifferentiation cells can undergo chromosomal inactivation outside of any norm...

Rapid interphase chromosome territory repositioning appears to function through the action of nuclear myosin and actin, in a nuclear motor complex. We have found that chromosome repositioning when cells leave the cell cycle is not apparent in cells that have mutant lamin A or that are lacking emerin. We discuss the possibility that there is a functional intranuclear complex comprising four prot...

A number of genera of Histiostomatidae inhabit phytotelmata, being found fully submerged and filtering organic matter from the fluid. One such phytotelm habitat is the fluid-filled pitchers of species of Nepenthes, a carnivorous plant genus widely distributed in the Old World tropics. As in most histiostomatid species, males of Nepenthes-inhabiting mites seek out tritonymphal females and guard ...

Males of many species guard their mates to prevent rivals from usurping paternity of the potential offspring. Environmental conditions, such as temperature, may affect a maleÕs ability to guard a female effectively and consequently the amount of sperm competition that occurs. We tested whether temperature and light affected mating behavior in laboratory experiments on the Japanese beetle, Popil...