Sliding piece puzzles with oriented tiles

AbstractIn this paper, we consider n identical tiles which are placed on the n + 1 vertices of a graph and which move along the edges of the graph. The tiles come with an “orientation”, an element of an arbitrary finite group H. Moving a tile along a given edge into the empty vertex changes the orientation of the tile in a prescribed way. We study the group of oriented positions of the tiles achievable from an initial position which fix the empty vertex. It may be thought of as a subgroup of the semidirect product Hn⋊Sn or the wreath product H wr Sn

Radiofrequency ablation of drug refractory ventricular tachycardia related to cocaine use: A feasibility, safety, and efficacy study

RF Ablation of VT in Chronic Cocaine Users Background Cocaine use is a known but rare cause of cardiac arrhythmias. Ventricular arrhythmias related to cocaine may not respond to antiarrhythmic drugs and may need treatment with radiofrequency ablation. Objectives We describe the clinical and electrophysiological characteristics of cocaine-related ventricular tachycardia (VT) from a multicenter registry. Methods Subjects presenting with VT related to cocaine use and being considered for radiofrequency ablation have been included in the study. Patients who were refractory to maximal medical therapy underwent radiofrequency ablation of the VT. Clinical, procedural variables, efficacy, and safety outcomes were assessed. Results A total of 14 subjects met study criteria (age 44 ± 13, range 18- to 68-year-old with 79% male, 71% Caucasian). MRI showed evidence of scar only in 43% of patients (6/14). The mechanism of VT was focal in 50% (n = 7) and scar related reentry in 50% (n = 7) based on 3D mapping. The mean VT cycle length was 429 ± 96 milliseconds. The site of origin was epicardial in 16% (3/18) of VTs. Most clinical VTs were hemodynamically stable (75%). Mean ejection fraction at the time of admission was 44 ± 14%. Duration of procedure was 289 ± 50 minutes. One subject developed pericardial tamponade requiring drainage. At 18 ± 11 months follow-up, freedom from arrhythmia was seen in 86% (1 case lost to follow-up and 2 died). Conclusion Radiofrequency ablation is not only feasible but also safe and effective in patients who have drug refractory VT related to chronic cocaine use. © 2014 Wiley Periodicals, Inc

Age-dependent impact of fluoroscopic radiation on the gender of off-spring: An international survey of cardiologists

Background: Fluoroscopic radiation has been implicated in reducing the sex ratio (M:F) by potentially damaging the Y chromosome. We examined the effects of exposure to fluoroscopic radiation on gender of offspring of cardiologists across the world. Methods: An internet based survey was e-mailed worldwide to 8000 physicians who practice invasive electrophysiology and/or interventional cardiology. Survey questions included age, race, sub-specialty, hours of exposure to radiation, number of children, gender of off-spring, miscarriages and mutations and exposure to radiation prior to conception of each child. Logistic regression analyses were performed on years of exposure and gender of offspring born post radiation exposure. Results: Responses of 377 cardiologists (84% male and 16% female) were reviewed. With a total of 398 males and 402 females born to 377 cardiologists, although reduced, the overall sex ratio (0.99) was not significantly different from that observed in the general population (1.05). Univariate logistic regression analysis identified higher male births with increasing hours of radiation exposure (OR 1.034, CI 1.003-1.067 p=0.03) and increasing paternal age (OR 1.05, CI 1.01-1.08, p=0.002). Subgroup analysis of children of male cardiologists revealed higher incidence of male births with increasing age and radiation exposure and multivariate analysis only identified paternal age as predictor of higher incidence of male births (OR 1.05, CI 1.01-1.089, p=0.0027). Conclusion: Exposure to ionizing radiation leads to a decrease in the sex ratio (M/F) in younger male cardiologists, while this effect is reversed with greater number of male births in older male cardiologists