A hybrid kinetic Monte Carlo method for simulating silicon films grown by plasma-enhanced chemical vapor deposition.

We present a powerful kinetic Monte Carlo (KMC) algorithm that allows one to simulate the growth of nanocrystalline silicon by plasma enhanced chemical vapor deposition (PECVD) for film thicknesses as large as several hundreds of monolayers. Our method combines a standard n-fold KMC algorithm with an efficient Markovian random walk scheme accounting for the surface diffusive processes of the species involved in PECVD. These processes are extremely fast compared to chemical reactions, thus in a brute application of the KMC method more than 99% of the computational time is spent in monitoring them. Our method decouples the treatment of these events from the rest of the reactions in a systematic way, thereby dramatically increasing the efficiency of the corresponding KMC algorithm. It is also making use of a very rich kinetic model which includes 5 species (H, SiH3, SiH2, SiH, and Si2H5) that participate in 29 reactions. We have applied the new method in simulations of silicon growth under several conditions (in particular, silane fraction in the gas mixture), including those usually realized in actual PECVD technologies. This has allowed us to directly compare against available experimental data for the growth rate, the mesoscale morphology, and the chemical composition of the deposited film as a function of dilution ratio.

[Ureteropelvic stenosis, agenesia of the contralateral kidney and sinistral inferior vena cava]. / Nierenbeckenabgangsenge, Agenesie der kontralateralen Niere und V. cava inferior sinistra.

INTRODUCTION: Ureteropelvic stenosis occurs as a result of intraluminal or extraluminal alterations at the ureteropelvic junction. It is the most common cause of upper urinary tract obstruction. CASE REPORT: We report about a rare case of a man with ureteropelvic junction obstruction and a renal pelvic stone accompanied by other congenital anomalies, including a sinistral inferior vena cava and agenesis of the opposite kidney. Multiple vessels were present in front of the renal pelvis, while the renal vein itself was situated dorsal to the left renal pelvis, resulting in compression and obstruction of the ureteropelvic junction. Dismembered pyeloplasty using the Anderson-Hynes technique was performed placing the ureter dorsal to the renal vein. CONCLUSION: Various vascular anomalies, especially in the region of the vena cava, can result in renal vasculature abnormalities and development of secondary ureteropelvic stenosis. Ureteropelvic stenosis may coexist with other congenital defects.

The role of ultrasonographically guided puncture of the human rete testis in the therapeutic management of nonobstructive azoospermia.

We attempted to characterize the cells collected from the rete testis via ultrasonographically guided puncture. Unilateral puncture of the rete testis was performed in nine men with obstructive azoospermia and 51 men with nonobstructive azoospermia. All the aspirated samples from the rete testis were observed via confocal scanning laser microscope and some of them after fluorescent in situ hybridization techniques. Then therapeutic testicular biopsy was performed in the punctured testis of each man. Spermatozoa were found in all rete testis samples and all biopsy samples from obstructed men. Twenty-two nonobstructed men demonstrated absence of spermatozoa in biopsy samples. Twenty-nine nonobstructed men showed spermatozoa in biopsy material and 24 of these men (82%) had demonstrated spermatozoa in rete testis samples. There were no significant differences in fertilization and cleavage rate between intracytoplasmic sperm injection trials using biopsy spermatozoa and rete testis spermatozoa both in obstructed and nonobstructed men. Considering that puncture of the rete testis does not reduce the volume of testicular parenchyma, is less invasive and apparently causes less detrimental effect on testicular vasculature than biopsy, puncture of rete testis is recommended as first line approach for the treatment of azoospermic men. If puncture is negative for spermatozoa in nonobstructed men, biopsy is indicated.

Nonsurgical implantation of Tenckhoff peritoneal catheters in patients on continuous ambulatory peritoneal dialysis.

From 1994 to 1998, 54 Tenckhoff peritoneal catheters were implanted in 49 patients undergoing continuous ambulatory peritoneal dialysis. The implantation technique included bedside insertion of peritoneal catheters via trocar under local anesthesia. Early and late complications of this technique were comparable with surgical techniques. Cumulative survival of all catheters was 91% after one year, 78% after two years, 71% after three years, and 68% after four years. Our results suggest that the percutaneous technique for insertion of peritoneal catheters remains an easy, safe, and useful technique in the management of end-stage renal disease patients.