We prove that the three art gallery problems Vertex Guard, Edge Guard and Point Guard for simple polygons with holes cannot be approximated by any polynomial time algorithm with a ratio of 1? 28 ln n, for any > 0, unless N P T IM E(n O(log log n)). We obtain our results by extending and modifying the concepts of a construction introduced in Eide98].

My primary research interest is social behavior of software agents acting in general-sum normal form games. In an environment with another agent, an agent needs to be able to identify if the opponent is hostile or cooperative by looking at the opponent’s actions, and respond appropriately. If the opponent is hostile, the agent should guard against it. Even for a self-interested agent, cooperati...

We present a tool, simplify-defun, that transforms the definition of a given function into a simplified definition of a new function, providing a proof checked by ACL2 that the old and new functions are equivalent. When appropriate it also generates termination and guard proofs for the new function. We explain how the tool is engineered so that these proofs will succeed. Examples illustrate its...

T he central roles of potassium channels in regulating membrane potential and controlling action potential repolarization are well documented (1). In plants an additional important function of potassium channels in mediating long-term potassium transport during cell movements, turgor changes, and tropisms has been proposed. Two guard cells surround each stomatal pore in leaves and control the o...

Much of the research on military families has focused on active duty service members. Little is known about informal and formal supports that National Guard service members use. Using an ecological systems perspective, this exploratory pilot study assessed awareness, access, use, satisfaction, and perceptions of effectiveness of informal and formal supports in a small group of National Guard se...

The purpose of the study was to examine the compliance of children wearing their mouthguards, and to evaluate socio-environmental factors that impact upon the usage of the device. Eighty children attending the student clinic of the Hadassah School of Dental Medicine received mouthguards free of charge. One year later, 69 participants and their parents answered a survey aimed at gaining informat...