ECG dilemma

"A 48-year-old white male presented to the emergency room (ER) with 5-day history of fever and chills. He also reported chest pain, which he described as heaviness and radiating to the left arm. He reports generalized weakness. He has no significant past medical history. He was told to have a murmur since childhood. He does not have orthopnea nor paroxysmal nocturnal dyspnea. Vitals on examination were: Heart rate 30 bpm, blood pressure 100/60 mm Hg. Physical examination: Ejection systolic murmur grade 3/6 heard at the right upper sternal border and radiating to both carotids, lungs were clear to auscultation, skin and extremity examination was normal. Laboratory studies obtained in the ER: WBC 26, 900 /[mu]l, hemoglobin 12.2 g/dl, BUN 23 mg/dl creatinine 0.97 mg/dl, troponin I 0.3 ng/ml, hemoglobin A1c 9.2[percent]. Blood culture results obtained the next day showed 4 of 4 cultures positive for Gram positive cocci in chains. Electrocardiogram obtained is shown below. Transthoracic echocardiogram was performed – valves were not adequately visualized due to poor imaging windows but showed mild mitral and tricuspid regurgitation, aortic valve was calcified with moderate stenosis."Sudarshan Balla (1), Archana Vasudevan (2) ; 1. Division of Cardiology, West Virginia University School of Medicine. 2. Department of Medicine – Division of Infectious Diseases, University of MissouriIncludes bibliographical reference

Neighbor Discovery in Wireless Networks and the Coupon Collector's Problem

Neighbor discovery is one of the first steps in the initialization of a wireless ad hoc network. In this paper, we design and analyze practical algorithms for neighbor discovery in wireless networks. We first consider an ALOHA-like neighbor discovery algorithm in a synchronous system, proposed in an earlier work. When nodes do not have a collision detection mechanism, we show that this algorithm reduces to the classical Coupon Collector’s Problem. Consequently, we show that each node discovers all its n neighbors in an expected time equal to ne(ln n+c), for some constant c. When nodes have a collision detection mechanism, we propose an algorithm based on receiver status feedback which yields a ln n improvement over the ALOHA-like algorithm. Our algorithms do not require nodes to have any estimate of the number of neighbors. In particular, we show that not knowing n results in no more than a factor of two slowdown in the algorithm performance. In the absence of node synchronization, we develop asynchronous neighbor discovery algorithms that are only a factor of two slower than their synchronous counterparts. We show that our algorithms can achieve neighbor discovery despite allowing nodes to begin execution at different time instants. Furthermore, our algorithms allow each node to detect when to terminate the neighbor discovery phase

On Optimal Neighbor Discovery

Mobile devices apply neighbor discovery (ND) protocols to wirelessly initiate a first contact within the shortest possible amount of time and with minimal energy consumption. For this purpose, over the last decade, a vast number of ND protocols have been proposed, which have progressively reduced the relation between the time within which discovery is guaranteed and the energy consumption. In spite of the simplicity of the problem statement, even after more than 10 years of research on this specific topic, new solutions are still proposed even today. Despite the large number of known ND protocols, given an energy budget, what is the best achievable latency still remains unclear. This paper addresses this question and for the first time presents safe and tight, duty-cycle-dependent bounds on the worst-case discovery latency that no ND protocol can beat. Surprisingly, several existing protocols are indeed optimal, which has not been known until now. We conclude that there is no further potential to improve the relation between latency and duty-cycle, but future ND protocols can improve their robustness against beacon collisions.Comment: Conference of the ACM Special Interest Group on Data Communication (ACM SIGCOMM), 201

On Neighbor Discovery in Wireless Networks With Directional Antennas. UMass Comp.

Abstract We consider the problem of neighbor discovery in static wireless ad hoc networks with directional antennas. We propose several probabilistic algorithms in which nodes perform random, independent transmissions to discover their one-hop neighbors. Our neighbor discovery algorithms are classified into two groups, viz. DirectDiscovery Algorithms in which nodes discover their neighbors only upon receiving a transmission from their neighbors and Gossip-Based Algorithms in which nodes gossip about their neighbors' location information to enable faster discovery. We first consider the operation of these algorithms in a slotted, synchronous system and mathematically derive their optimal parameter settings. We show how to extend these algorithms for an asynchronous system and describe their optimal design. Analysis and simulation of the algorithms show that nodes discover their neighbors much faster using gossip-based algorithms than using direct-discovery algorithms. Furthermore, the performance of gossip-based algorithms is insensitive to an increase in node density. The efficiency of a neighbor discovery algorithm also depends on the choice of antenna beamwidth. We discuss in detail how the choice of beamwidth impacts the performance of the discovery process and provide insights into how nodes can configure their beamwidths

Court Trial based Detection of Forwarding Misbehaviors in Wireless Networks

We consider the problem of identifying the source of forwarding misbehavior in ad hoc networks. Unlike existing proposals [1,2], we consider an approach that works locally, within k-hops of the node under investigation, and require