QKD in Standard Optical Telecommunications Networks

To perform Quantum Key Distribution, the mastering of the extremely weak signals carried by the quantum channel is required. Transporting these signals without disturbance is customarily done by isolating the quantum channel from any noise sources using a dedicated physical channel. However, to really profit from this technology, a full integration with conventional network technologies would be highly desirable. Trying to use single photon signals with others that carry an average power many orders of magnitude bigger while sharing as much infrastructure with a conventional network as possible brings obvious problems. The purpose of the present paper is to report our efforts in researching the limits of the integration of QKD in modern optical networks scenarios. We have built a full metropolitan area network testbed comprising a backbone and an access network. The emphasis is put in using as much as possible the same industrial grade technology that is actually used in already installed networks, in order to understand the throughput, limits and cost of deploying QKD in a real network

Theory and simulation of the nematic zenithal anchoring coefficient

Combining molecular simulation, Onsager theory and the elastic description of nematic liquid crystals, we study the dependence of the nematic liquid crystal elastic constants and the zenithal surface anchoring coefficient on the value of the bulk order parameter

Effect of body characteristics on thoracic attenuation of intra-cardiac electrical activity recorded on the surface electrocardiogram

The objective of this study was to determine the effect of body characteristics on the electrical transfer function of the human thorax. Twenty patients undergoing electrophysiologic study were enrolled. Unipolar stimuli were applied in the right ventricular apical and posterioseptal areas. XYZ surface ECGs and unipolar intra-cardiac electrograms of the pacing impulses were recorded and signal-averaged. The intracardiac-to-surface transfer functions were modeled and compared with body characteristics. Physical dimensions, respiratory measures obtained by spirometry, and age correlated with magnitude intercepts and slopes of the modeled transfer functions in all three directions. The phase transfer functions were correlated with physical dimensions in the Y and Z directions. The effect of body characteristics on the frequency dependency of attenuation and phase has implications on the use of surface ECG and body surface mappin

Sudden Cardiac Death Risk Stratification in Patients With Nonischemic Dilated Cardiomyopathy

ObjectivesThe purpose of this study was to provide a meta-analysis to estimate the performance of 12 commonly reported risk stratification tests as predictors of arrhythmic events in patients with nonischemic dilated cardiomyopathy.BackgroundMultiple techniques have been assessed as predictors of death due to ventricular tachyarrhythmias/sudden death in patients with nonischemic dilated cardiomyopathy.MethodsForty-five studies enrolling 6,088 patients evaluating the association between arrhythmic events and predictive tests (baroreflex sensitivity, heart rate turbulence, heart rate variability, left ventricular end-diastolic dimension, left ventricular ejection fraction, electrophysiology study, nonsustained ventricular tachycardia, left bundle branch block, signal-averaged electrocardiogram, fragmented QRS, QRS-T angle, and T-wave alternans) were included. Raw event rates were extracted, and meta-analysis was performed using mixed effects methodology. We also used the trim-and-fill method to estimate the influence of missing studies on the results.ResultsPatients were 52.8 ± 14.5 years of age, and 77% were male. Left ventricular ejection fraction was 30.6 ± 11.4%. Test sensitivities ranged from 28.8% to 91.0%, specificities from 36.2% to 87.1%, and odds ratios from 1.5 to 6.7. Odds ratio was highest for fragmented QRS and TWA (odds ratios: 6.73 and 4.66, 95% confidence intervals: 3.85 to 11.76 and 2.55 to 8.53, respectively) and lowest for QRS duration (odds ratio: 1.51, 95% confidence interval: 1.13 to 2.01). None of the autonomic tests (heart rate variability, heart rate turbulence, baroreflex sensitivity) were significant predictors of arrhythmic outcomes. Accounting for publication bias reduced the odds ratios for the various predictors but did not eliminate the predictive association.ConclusionsTechniques incorporating functional parameters, depolarization abnormalities, repolarization abnormalities, and arrhythmic markers provide only modest risk stratification for sudden cardiac death in patients with nonischemic dilated cardiomyopathy. It is likely that combinations of tests will be required to optimize risk stratification in this population

A new method to determine the electrical transfer function of the human thorax

Traditional analyses have assumed that cardiac electrical activity is reflected on the surface ECG without distortion as the signal passes through the body tissues. This study aims to explore the frequency dependence of thoracic attenuation of surface-recorded intracardiac electrical activity. Twenty patients (14 men, 55 +/- 15 yr of age) undergoing electrophysiological study were enrolled. Rectangular unipolar stimuli were applied from a catheter positioned in the right ventricular apical area and another in the posteroseptal area without contact with the myocardium. An orthogonal Frank-lead surface ECG and a unipolar intracardiac electrogram near the pacing site were recorded. Frequency domain characteristics of the signal-averaged pacing impulses were analyzed. Linear regression analysis showed significant frequency-dependent attenuation in the magnitude transfer functions (R(2) = 0.84-0.89, P < 0.0001) and good linear fit for the phase transfer characteristics (R(2) = 0.98-1.0, P < 0.0001). Age, physical dimension, and respiratory characteristics had significant effects on the magnitude and phase characteristics of the transfer functions. Application of models of the low- and high-slope transfer functions to signal-averaged ECGs from 33 subjects showed differences in the attenuation of P and T waves relative to the QRS