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Current catheter designs used for radiofrequency (RF) in cardiac tissue achieve limited ablation depth as lesion size is driven heavily by resistive heating at the tissue surface. A catheter with a truncated, dome-shaped tip with a toroidal surface designed for focal RF ablation was recently described. This in vivo study compares lesion characteristics between a second-generation focused electric field (FEF) catheter vs a standard irrigated catheter using RF energy in a beating heart model. We performed in vivo ablations using RF energy with the FEF ablation catheter tip (Focused Therapeutics) and an irrigated Blazer catheter (Boston Scientific) under identical power, duration, and irrigation rates. In addition, RF dosing at high power and duration was examined using the FEF catheter. Intracardiac echocardiography was used to evaluate steam pops and catheter tip angle relative to the tissue surface. Studies were terminal and lesion size was measured following 2,3,5-triphenyltetrazolium chloride staining. Ablations were performed in 6 swine (FEF, n = 31; control, n = 8). FEF ablation lesions (n = 7) were deeper (15.6 ± 2.6 mm vs 7.5 ± 1.9 mm; P< 0.001) and wider (18.4 ± 2.9 mm vs 12.6 ± 2.4 mm; P < 0.001) than lesions delivered with the control irrigated catheter (n = 8) under the same parameters. Thirty-two percent (n = 10 of 31) of lesions delivered from the left ventricle endocardial surface using the FEF catheter were transmural. No steam pops were observed with delivery of FEF lesions (n = 31). The angle of incidence did not significantly affect FEF lesion size. In this in vivo preclinical study, the FEF catheter, which provides focused energy delivery, resulted in significantly larger lesions than the irrigated control catheter without steam pops. Approximately one-third of ablations with the FEF catheter delivered from the endocardial left ventricular surface resulted in transmural lesions.

Abstract: Some of the parameters which determine the amount of intermixing of GaAs/AIGaAs quantum wells (QWs) using SiO2 capping and rapid thermal annealing (RTA) have been studied using photoluminescence (PL) techniques. The degree of intermixing of QWs was found to be larger for thicker SiO2 capping layers and for shorter distances between the QWs and the oxide-wafer interface. A maximum PL energy difference of 90 meV was observed between the region covered by a 1.3 μm thick oxide layer and the non-oxide region in a wafer that was annealed at 1100 C for 15 s.

Measurement of mode chirping in a current-modulated semiconductor laser was performed using a Michelson interferometer. For a current step excitation, the rate of this chirping decays as a function of time, and two characteristic time constants were identified. Their interpretation is discussed, and the thermal impedance of the device is calculated. In addition, the significance of such a measurement for the analysis of chirp-induced modal noise in optical fibers is discussed, and experimental results are presented.

An N_2O laser is described which is tunable over 65 rotational lines of the 00°1–10°0 band. A simple method is used to determine the cavity losses of this laser. Absorption of a number of N_2O lines by the 00°1–10°0 band of CO_2 is demonstrated. The P (20) line of N_2O is observed after attenuation by a long path of N_2O at 125-torr pressure and the peak absorption coefficient for this line is found to be 0.0094 cm^−1 at 300 K. The N_2O laser has a certain advantage over the CO_2 laser for long-range communications through the atmosphere.

An N_2O laser is described which is tunable over 65 rotational lines of the 00°1-10°0 band. A simple method is used to determine the cavity losses of this laser. Absorption of a number of N_2O lines by the 00°1-10°0 band of CO_2 is demonstrated. The P (20) line of N_2O is observed after attenuation by a long path of N_2O at 125-torr pressure and the peak absorption coefficient for this line is found to be 0.0094 cm^-1 at 300 K. The N_2O laser has a certain advantage over the CO_2 laser for long-range communications through the atmosphere.

The scope and depth of material presented in this book is a reflection of the extensive and thorough expertise developed at the Australian National University over the past several years. It is basically a theoretical treatment of the electromagnetic wave propagation problem in fibers and is intended for the theoretically oriented audience. The numerous waveguide configurations considered, and the large number of examples worked out make this book very helpful for a person trying to explore new applications or new fiber designs. On the other hand, communications systems applications are not included here; and therefore, topics related to signal propagation such as modai and polarization noise, harmonic distortion, and the effect of coherence are not covered. This extensive book should be very useful not only to the theoretician, but also to the experimentalist in need of a particular mathematical expression for a particular fiber configuration. The goal stated by the authors at the beginning is well fulfilled and this book should be a welcome addition to the library of fiber optics literature.