Optical mode solving for complex waveguides using a finite cloud method.

A meshless method for the solution of full vectorial optical mode fields has been applied to micro-structured optical waveguides. The Finite Cloud Method is used to approximate the solution using a point distribution and material definitions. Presented are two methods of defining material interfaces, one which implements a step index and a second which uses a graded index. Coupled field equations are used to solve for both transverse components of the magnetic field as well as the guided wavelength and effective index of refraction. Comparing results for a ridge waveguide, solid core, micro-structured and air core structures with commercial FEM solvers highlight the methods versatility, accuracy and efficiency.

An upgraded x-ray spectroscopy diagnostic on MST.

An upgraded x-ray spectroscopy diagnostic is used to measure the distribution of fast electrons in MST and to determine Z(eff) and the particle diffusion coefficient D(r). A radial array of 12 CdZnTe hard-x-ray detectors measures 10-150 keV Bremsstrahlung from fast electrons, a signature of reduced stochasticity and improved confinement in the plasma. A new Si soft-x-ray detector measures 2-10 keV Bremsstrahlung from thermal and fast electrons. The shaped output pulses from both detector types are digitized and the resulting waveforms are fit with Gaussians to resolve pileup and provide good time and energy resolution. Lead apertures prevent detector saturation and provide a well-known etendue, while lead shielding prevents pickup from stray x-rays. New Be vacuum windows transmit >2 keV x-rays, and additional Al and Be filters are sometimes used to reduce low energy flux for better resolution at higher energies. Measured spectra are compared to those predicted by the Fokker-Planck code CQL3D to deduce Z(eff) and D(r).

Biliary and other gastrointestinal interventions.

Over the past several years, renewed interest in biliary endoprostheses has developed among interventional radiologists. The experimental, technical, and clinical progress that produced this enthusiasm is reviewed, with emphasis on recently published reports. The application of percutaneous enterostomy for gastric decompression or feeding has become widely practiced, and recent reports of percutaneous and endoscopic gastrostomy are compared, with emphasis on controversial points. The technique of percutaneous enterostomy has been adapted for jejunal and colonic application, and these technical modifications, as well as miscellaneous biliary and gastrointestinal interventions, comprise the remainder of the review.

Assessment of heparin anticoagulation during peripheral angioplasty.

The amount of heparin administered during peripheral angioplasty procedures is controversial and varies greatly among angiographers. Complications may result from both excessive and insufficient anticoagulation. The authors characterized the anticoagulant response to heparin in patients undergoing angioplasty by means of the activated clotting time (ACT). The ACT was measured in 64 patients who underwent lower extremity angioplasty. There was a linear relationship between heparin dose and ACT (P = .0001), but the slope of this relationship varied from patient to patient (R2 = .232). The response to heparin was blunted in one patient with thrombosis, but it was not exaggerated in patients with hematomas. Heparin anticoagulant response is highly variable, and heparin administration should be individualized according to ACT to produce a desired level of anticoagulation. Use of the ACT is a convenient and reproducible means of monitoring heparin administration and may increase safety and efficacy during peripheral angioplasty.