Algebraic construction of quantum integrable models including inhomogeneous models

Exploiting the quantum integrability condition we construct an ancestor model associated with a new underlying quadratic algebra. This ancestor model represents an exactly integrable quantum lattice inhomogeneous anisotropic model and at its various realizations and limits can generate a wide range of integrable models. They cover quantum lattice as well as field models associated with the quantum $R$-matrix of trigonometric type or at the undeformed $q \to 1$ limit similar models belonging to the rational class. The classical limit likewise yields the corresponding classical discrete and field models. Thus along with the generation of known integrable models in a unifying way a new class of inhomogeneous models including variable mass sine-Gordon model, inhomogeneous Toda chain, impure spin chains etc. are constructed.Comment: Latex, 14pages, To be published in the Rev. Math. Phys annual conf.ROMP99 Proceedings (Tarun, Poland, 1999

Ganglionic Plexus Ablation During Pulmonary Vein Isolation - Predisposing to Ventricular Arrhythmias?

Catheter ablation is increasingly used to treat patients with atrial fibrillation (AF). Ablation of ganglionic plexi is often performed to reduce vagal innervation and has been shown to confer a better long-term outcome in terms of AF recurrence. We report a case of a patient having AF ablation with a profound vagal response, suggesting ganglionic plexus ablation, who subsequently developed ventricular fibrillation after programmed ventricular stimulation. Reduced vagal modulation is known to predispose to ventricular arrhythmias and vagal denervation following AF ablation may predispose to ventricular arrhythmias and requires further study

Pulmonary Vein Isolation using a High Density Mesh Ablator Catheter: Incorporation of three-Dimensional Navigation and Mappin

Background: We evaluated the use of a novel High Density Mesh Ablator (HDMA) catheter in combination with three-dimensional navigation for the treatment of paroxysmal atrial fibrillation. Methods: The HDMA catheter was used to carry out pulmonary vein isolation in a consecutive series of patients. Three-dimensional geometry of the left atrial-pulmonary vein (LA-PV) junctions were first created with the HDMA catheter. Ostial, proximal and distal sites within the pulmonary veins were tagged with catheter shadows on the created geometry to allow for re-interrogation of these exact sites after ablation. Results: The HDMA catheter was successfully used to create three dimensional geometry of the LA-PV junction in a total of 20 pulmonary veins which involved 5 patients. In all cases, ostial ablation alone was sufficient to achieve electrical isolation. No significant pulmonary vein stenosis was seen acutely after ablation. Conclusion: We describe the successful use of the novel HDMA catheter to create three-dimensional geometry of the LA-PV junction to assist with pulmonary vein isolation

Increase in organization index predicts atrial fibrillation termination with flecainide post-ablation: spectral analysis of intracardiac electrograms

Aims: The mechanism of the action of flecainide in the termination of human atrial fibrillation (AF) is not fully understood. We studied the acute effects of flecainide on AF electrograms in the time and frequency domain to identify factors associated with AF termination. Methods and results: Patients who were still in AF at the end of catheter ablation for AF were given intravenous flecainide. Dominant frequency (DF) and organization index (OI) were obtained by fast Fourier transform of electrograms from the coronary sinus catheter over 10 s in AF, before and after flecainide infusion. Mean AF cycle length (CL) was also calculated. Twenty-six patients were studied (16 paroxysmal AF and 10 persistent AF). Seven converted to sinus rhythm (SR) with flecainide. In all patients, mean CL increased from 211 ± 44 to 321 ± 85 ms ( P \u3c 0.001). Mean DF decreased from 5.2 ± 1.03 to 3.6 ± 1.04 Hz ( P \u3c 0.001). Mean OI was 0.33 ± 0.13 before and 0.32 ± 0.11 after flecainide ( P = 0.90). Comparing patients who converted to SR with those who did not, OI post-flecainide was 0.41 ± 0.12 vs. 0.29 ± 0.10 ( P = 0.013), and the relative change in OI was 29 ± 33 vs. −3.9 ± 27% ( P = 0.016), respectively. No significant difference was noted in the change in CL and DF in the two groups. Conclusion: Increase in OI, independent of changes to CL and DF, appears critical to AF termination with flecainide. Increase in OI holds promise as a sensitive predictor of AF termination

Algebraic approach in unifying quantum integrable models

A novel algebra underlying integrable systems is shown to generate and unify a large class of quantum integrable models with given $R$-matrix, through reductions of an ancestor Lax operator and its different realizations. Along with known discrete and field models a new class of inhomogeneous and impurity models are obtained.Comment: Revtex, 6 pages, no figure, revised version to be published in Phys. Rev. Lett., 199

Testing hypotheses in the Birnbaum-Saunders distribution under type-II censored samples

The two-parameter Birnbaum-Saunders distribution has been used succesfully to model fatigue failure times. Although censoring is typical in reliability and survival studies, little work has been published on the analysis of censored data for this distribution. In this paper, we address the issue of performing testing inference on the two parameters of the Birnbaum-Saunders distribution under type-II right censored samples. The likelihood ratio statistic and a recently proposed statistic, the gradient statistic, provide a convenient framework for statistical inference in such a case, since they do not require to obtain, estimate or invert an information matrix, which is an advantage in problems involving censored data. An extensive Monte Carlo simulation study is carried out in order to investigate and compare the finite sample performance of the likelihood ratio and the gradient tests. Our numerical results show evidence that the gradient test should be preferred. Three empirical applications are presented.Comment: Submitted for publicatio

Multidimensional Isotropic and Anisotropic Q-Oscillator Models

q-oscillator models are considered in two and higher dimensions and their symmetries are explored. New symmetries are found for both isotropic and anisotropic cases. Applications to the spectra of triatomic molecules and superdeformed nuclei are discussed.Comment: 12 Pages, LATEX, no figures, (Submitted to J. PHYS. A

Radio spectral properties and the magnetic field of the SNR S147

(Abridged) S147 is a large faint shell-type supernova remnant (SNR). Its remarkable spectral break at cm-wavelengths is an important physical property to characterize the SNR evolution. However, the spectral break is based on radio observations with limited precision. We made new radio continuum and polarization observations of S147 at 11cm and at 6cm with the Effelsberg 100-m telescope and the Urumqi 25-m telescope, respectively. These new data were combined with published lower frequency data from the Effelsberg 100-m telescope and very high frequency data from WMAP to investigate the spectral turnover and polarization properties of S147. S147 consists of numerous filaments embedded in diffuse emission. We found that the integrated flux densities of S147 are 34.8+/-4.0 Jy at 11cm and 15.4+/-3.0Jy at 6cm. These new measurements confirm the known spectral turnover at ~1.5GHz, which can be entirely attributed to the diffuse emission component. The spectral index above the turnover is -1.35+/-0.20. The filamentary emission component has a constant spectral index over the entire wavelength range up to 40.7GHz of -0.35+/-0.15. The weak polarized emission of S147 is at the same level as the ambient diffuse Galactic polarization. The rotation measure of the eastern filamentary shell is about -70 rad/m2. The filamentary and diffuse emission components of S147 have different physical properties, which make S147 outstanding among shell type SNRs.The weak polarization of S147 at 11cm and at 6cm can be attributed to a section of the S147 shell showing a tangential magnetic field direction.Comment: 11 pages, 17 figures, accepted for publication in Astronomy & Astrophysics, the resolution of some figures have been reduced. For high resolution version, see ftp://ftp.mpifr-bonn.mpg.de/outgoing/p098wre/xiao-etal.pdf,revised following the language edito