Search

The ability to extract spatial features from 3D objects is essential for applications such as shape matching and object classification. However, designing an effective feature vector which is invariant with respect to rotation, translation and scaling is a challenging task and is often solved by normalization techniques such as PCA, which can give rise to poor object alignment. In this paper, we introduce a novel method to extract robust and invariant 3D features based on rotational symmetry. By applying a rotation-variant similarity function on two instances of the same 3D object, we can define an autocorrelation on the object in the space of rotations. We use a special representation of the SO(3) and determine significant rotation axes for an object by means of optimization techniques. By sampling the similarity function via rotations around these axes, we obtain robust and invariant features, which are descriptive for the underlying geometry. The resulting feature vector cannot only be used to characterize an object with respect to rotational symmetry but also to define a distance between 3D models. Because the features are compact and pre-computable, our method is suitable to perform similarity searches in large 3D databases. [ABSTRACT FROM AUTHOR]

Introduction: Atrioesophageal fistula is an uncommon but often lethal complication of atrial fibrillation (AF) ablation. The purpose of our study was to prospectively investigate the incidence of esophageal ulcerations (ESUL) as well as the impact of energy settings, radiofrequency lesion sets, and direct visualization of the esophagus on esophageal wall injury. Methods and Results: One hundred seventy-five patients, 57.1% paroxysmal AF, 78.5% male, underwent AF ablation and esophagoscopy 24 hours thereafter. We performed a 2:1:1-randomization as follows: Control group: Ablation without visualization of the esophagus using 25 Watt (W) power limit on the posterior wall, n = 70. Visualization and 15 W maximum: Ablation guided by barium visualization of the esophageal course using a limit of 15 W, n = 35. Visualization and 25 W “short burns”: Ablation guided by barium visualization using 25 W and “short burns” (max. 5 sec), n = 35. Patients performed under general anesthesia (n = 35) were separated as a nasogastric tube for visualization of the esophagus was used. In total, we found 2.9% of patients (5/175) presenting ESUL. Parameters discriminating the development of ESUL in a specific patient were type of AF, maximum energy delivered, usage of a nasogastric tube, and additional left atrial lines. Visualization of the esophageal course by barium contrast was not able to prevent ESUL. Conclusion: ESUL is a rare finding when using a reasonable energy maximum of 25 W with open-irrigated tip catheters at the posterior wall. Lower energy settings may increase safety without losing efficacy. Additional linear radiofrequency lesions increase the risk of ESUL development. [ABSTRACT FROM AUTHOR]

Abstract: The performance of micromorph silicon tandem solar cells deposited by plasma enhanced chemical vapor deposition (PECVD) at 40MHz was investigated in a large area industrially employed reactor as a function of the crystalline fraction of the microcrystalline bottom cell. The relevant plasma parameters frequency, pressure, hydrogen and silane mixture, temperature were kept constant. The RF-power for the deposition of the bottom cell was varied in order to scan its Raman crystalline fraction over the transition region from amorphous into highly crystalline. Assuming constant amorphous or microcrystalline material quality (in terms of stability and defect density) the optimum value of the Raman crystalline fraction and especially the width of the optimum range was thus determined quantitatively. It is shown that the optimum Raman crystalline fraction of the bottom cell on substrates with front contact and amorphous top cell is . A clear decrease of short circuit current density is observed for too high crystalline fraction. [Copyright &y& Elsevier]

Atrial fibrillation (AF) is the most common heart rhythm disorder, with increasing prevalence in the aging population. The clinical presentation and evolution of AF can be highly variable. Therefore, treatment of AF can be challenging in some patients. This review summarizes recent developments in both prevention of thromboembolic events and rate/rhythm control highlighting the possibilities of behavioral, pharmacological, and catheter-based perspectives. [ABSTRACT FROM AUTHOR]