Weak coverage of a rectangular barrier

Assume n wireless mobile sensors are initially dispersed in an ad hoc manner in a rectangular region. They are required to move to final locations so that they can detect any intruder crossing the region in a direction parallel to the sides of the rectangle, and thus provide weak bar-rier coverage of the region. We study three optimization problems related to the movement of sensors to achieve weak barrier coverage: minimizing the number of sensors moved (MinNum), minimizing the average distance moved by the sensors (MinSum), and minimizing the maximum distance moved by the sensors (

2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS.

Peer reviewe

A roadmap to improve the quality of atrial fibrillation management:proceedings from the fifth Atrial Fibrillation Network/European Heart Rhythm Association consensus conference

At least 30 million people worldwide carry a diagnosis of atrial fibrillation (AF), and many more suffer from undiagnosed, subclinical, or 'silent' AF. Atrial fibrillation-related cardiovascular mortality and morbidity, including cardiovascular deaths, heart failure, stroke, and hospitalizations, remain unacceptably high, even when evidence-based therapies such as anticoagulation and rate control are used. Furthermore, it is still necessary to define how best to prevent AF, largely due to a lack of clinical measures that would allow identification of treatable causes of AF in any given patient. Hence, there are important unmet clinical and research needs in the evaluation and management of AF patients. The ensuing needs and opportunities for improving the quality of AF care were discussed during the fifth Atrial Fibrillation Network/European Heart Rhythm Association consensus conference in Nice, France, on 22 and 23 January 2015. Here, we report the outcome of this conference, with a focus on (i) learning from our 'neighbours' to improve AF care, (ii) patient-centred approaches to AF management, (iii) structured care of AF patients, (iv) improving the quality of AF treatment, and (v) personalization of AF management. This report ends with a list of priorities for research in AF patients

Locating a black hole in an un-oriented ring using tokens: The case of scattered agents

Black hole search in a ring network has been studied in a token model. It is known that locating the black hole in an anonymous ring using tokens is feasible, if the team of agents is initially co-located. When dealing with the scattered agents, the problem was so far solved only when the orientation of the ring is known. In this paper, we prove that a black hole can be located in a ring using tokens with scattered agents, even if the ring is un-oriented. More precisely, first we prove that the black hole search problem can be solved using only three scattered agents. We then show that, with k (k ≥ 4) scattered agents, the black hole can be located fewer moves. Moreover, when k (k ≥ 4) is a constant number, the move cost can be made optimal. These results hold even if both agents and nodes are anonymous

Using scattered mobile agents to locate a black hole in an un-oriented ring with tokens

A black hole in a network is a highly harmful host that disposes of any incoming agents upon their arrival. Determining the location of a black hole in a ring network has been studied when each node is equipped with a whiteboard. Recently, the Black Hole Search problem was solved in a less demanding and less expensive token model with co-located agents. Whether the problem can be solved with scattered agents in a token model remains an open problem. In this paper, we show not only that a black hole can be located in a ring using tokens with scattered agents, but also that the problem is solvable even if the ring is un-oriented. More precisely, first we prove that the black hole search problem can be solved using only three scattered agents. We then show that, with K (K 4) scattered agents, the black hole can be located in O(kn + n log n) moves. Moreover, when K (K K) is a constant number, the move cost can be reduced to O(n log n), which is optimal. These results hold even if both agents and nodes are anonymous

Scattered black hole search in an oriented ring using tokens

A black hole is a highly harmful host that disposes of visiting agents upon their arrival without any observable trace of the destruction. The problem of locating the blackhole in a asynchronous ring network is known to be solvable by a team of mobile agents if each node is equipped with a whiteboard. A simpler and less expensive inter-communication and synchronization mechanism is provided by tokens: each agent has available a bounded number of tokens that can be carried, placed in a node or/and on a port of the node, or removed. All tokens are identical and no other form of communication or coordination is available to the agents. It is known that locating the black hole in an anonymous ring network using tokens is feasible when the team of agents is initially colocated (i.e. they all start from the same host). Recently, the more difficult case when the agents are scattered (i.e., when the agents do not start from the same host) has also been examined and solutions requiring only O(1) tokens per agent but using a total of O(n2) moves have been presented. The number of moves can be reduced to 0(kn + n log n) if the number k of agents is known. In this paper, we study the impact of orientation and knowledge of team size on the cost of black hole location by scattered agents with tokens. We prove that, in oriented rings, the number of moves can be reduced from O(n2) to the optimal ⊖(n log n) using only O(1) tokens per agent, without any knowledge of the team size. This result holds even if both agents and nodes are anonymous. Interestingly, the proposed algorithm solves, with the same cost, also the Leader Election problem and the Rendezvous problem for the scattered agents despite the presence of a BH

The power of tokens: rendezvous and symmetry detection for two mobile agents in a ring

Rendezvous with detection differs from the usual rendezvous problem in that two mobile agents not only accomplish rendezvous whenever this is possible, but can also detect the impossibility of rendezvous (e.g., due to symmetrical initial positions of the agents) in which case they are able to halt. We study the problem of rendezvous with and without detection of two anonymous mobile agents in a synchronous ring. The agents have constant memory and each of them possess one or more tokens which may be left at some nodes of the ring and noticed later. We derive sharp bounds for the case of at most two tokens per agent and also explore trade-offs between the number of tokens available to the agents and the time needed to accomplish rendezvous with detection

Robust sensor range for constructing strongly connected spanning digraphs in UDGs

We study the following problem: Given a set of points in the plane and a positive integer k > 0, construct a geometric strongly connected spanning digraph of out-degree at most k and whose longest edge length is the shortest possible. The motivation comes from the problem of replacing omnidirectional antennae in a sensor network with k directional antennae per sensor so that the resulting sensor network is strongly connected. The contribution of this is paper is twofold: 1) We introduce a notion of robustness of the radius in geometric graphs. This allows us to provide stronger lower bounds for the edge length needed to solve our problem, while nicely connecting two previously unrelated research directions (graph toughness and multiple directional antennae). 2) We present novel upper bound techniques which, in combination with stronger lower bounds, allow us to improve the previous approximation results for the edge length needed to achieve strong connectivity for k = 4 (from 2sin(π/5) to optimal) and k = 3 (from 2 sin(π/4) to 2 sin(2π/9))

Towards Practical Deterministic Write-All Algorithms

The problem of performing t tasks on n asynchronous or undependable processors is a basic problem in parallel and distributed computing. We consider an abstraction of this problem called the WriteAl l problem---using n processors write 1's into all locations of an array of size t. The most e#cient known deterministic asynchronous algorithms for this problem are due to Anderson and Woll. The first class of algorithms has work complexity of O(t ), for n t and any #>0, and they are the best known for the full range of processors (n = t). To schedule the work of the processors, the algorithms use lists of q permutations on [q](q n) that have certain combinatorial properties. Instantiating such an algorithm for a specific # either requires substantial pre-processing (exponential in 1/# )to find the requisite permutations, or imposes a prohibitive constant (exponential in 1/# ) hidden by the asymptotic analysis. The second class deals with the specific case of t = n 2, and these algorithms have work complexity of O(t log t). They also use lists of permutations with the same combinatorial properties. However instantiating these algorithms requires exponential in n preprocessing to find the permutations. To alleviate this costly instantiation Kanellakis and Shvartsman proposed a simple way of computing the permutations. They conjectured that their construction has the desired properties but they provided no analysis. In this pape

Evacuating two robots from multiple unknown exits in a circle

Distributed on a unit circle are k exits. Two autonomous mobile robots are placed on the circle. Each robot has a maximum speed of 1 and the robots can communicate wirelessly. The robots have a map of the domain, including exits, but do not have knowledge of their own initial locations on the domain, rather they only know their relative distance. The goal of the evacuation problem is to give an algorithm for the robots which minimizes the time required for both robots to reach an exit, in the worst case. We consider two variations of the problem depending on whether the two robots have control over their initial distance. When the initial distance of the robots is part of the input (i.e. no control), we show that simple algorithms exist which achieve optimal worst case evacuation times for the cases where: the robots begin colocated with an arbitrary distribution of the exits; and when the exits are either colocated or evenly spaced, with arbitrary starting positions of the robots. We also give upper and lower bounds on the problem with arbitrary exit distribution and starting positions of the robots. For the problem where robots can choose their initial distance (with knowledge of, but not control over the distribution of exits), we propose a natural family of algorithms p