aTen samples of crystalline aluminum nitride (AlN) film were deposited on sapphire and silicon substrates by a plasma source molecular beam method. The samples were analyzed using X-ray photoelectron spectroscopy (XPS) depth profiling and high-resolution X-ray diffraction. Oxygen levels were observed to decrease exponentially from the surface into the bulk film. Aluminum, nitrogen and oxygen peaks were fitted with subpeaks in a consistent manner and the subpeaks were assigned to chemical states. AlN subpeaks were observed at 73.5 eV for Al2p and 396.4 eV for N1s. An N1s subpeak at 395.0 eV was assigned to N-N defects. No direct N-O bonds are assigned; rather it is proposed that an N-Al-O bond sequence is the source of higher binding energy N1s subpeaks. The observations in this study support a model in which oxygen is bound only to aluminum in the form of Al-O octahedral complexes dispersed or clustered throughout the main AlN matrix or as Al-O bonds on the crystal grain boundaries. The data also suggest that the AlN lattice parameters are related to oxygen content, since the c-axis is observed to increase with increasing oxygen content.

This paper presents the results of a prospective study of percutaneous transluminal angioplasty (PTA) for the treatment of patients with peripheral arterial occlusive disease and identifies the variables that are predictive of long-term success. The variables believed to be important prognostically were recorded for 984 consecutive PTAs performed between July 1978 and July 1986. Success or failure was defined using a combination of clinical and objective vascular laboratory criteria. The overall long-term success was estimated by the Kaplan-Meier method and differences between curves of success rate versus time for each variable were determined by the Wilcoxon and log-rank statistics. The combination of variables associated with success were determined by the Cox proportional hazards regression model. For all cases, the initial success rate was 88.6 +/- 1.0% and at 5 years was 48.2 +/- 2.3%. The following variables, when considered individually, were associated with success (p less than 0.05): indication for PTA, site of PTA, severity of lesion, runoff, number of sites dilated, diabetes, and the occurrence of a complication. From the Cox model, by using a stepwise multiple regression procedure, the following combination of variables were found to be predictive of success (p less than 0.05): (1) indication (claudication vs. salvage), (2) site (common iliac vs. other), (3) severity of lesion (stenosis vs. occlusion), and (4) runoff (good vs. poor). For all combinations of these four significant variables, curves of the success rate versus time were calculated. In conclusion, this study has identified the combination of four variables that together predict if PTA is likely to be successful in the management of a patient with peripheral arterial occlusive disease.

The use of NO x traps is one strategy being pursed to enable the implementation of more fuel-efficient leanburn gasoline engines. Materials development to enhance NO x storage capacity and sulfur tolerance will be necessary for performance improvement. Progress in these areas will benefit from a more detailed understanding of the base metal oxide-precious metal surface chemistry involved in the trapping, release, and reduction of NO x . In this work, we have focused on the adsorption of NO and NO 2 on in-situ evaporated thin films of barium oxide, the primary storage material in lean NO x traps, to accentuate the details of the trapping stage of NO x conversion using these systems. X-ray photoelectron spectroscopy has been used to identify the species formed and their relative abundance following room-temperature adsorption. Annealing experiments were performed to follow changes in adsorbed species with temperature. For NO, our results are consistent with nitrites forming as a result of molecular adsorption. In the case of NO 2 , nitrates are favored at high exposure and appear to form via a nitrite intermediate. We propose that as coverage increases nitrates form via trimer formation involving two surface nitrites and an additional molecularly adsorbed NO 2 resulting in a complex in which all nitrogen centers are nitratelike. In light of results presented, an alternative and more detailed interpretation of the mechanism of NO x trapping is offered, that accounts for the NO x storage capacity benefits resulting from NO oxidation over noble-metal sites.

Retrospective review of 5,942 patients who underwent open-heart surgery for acquired heart disease revealed that 123 patients (2.1%) required permanent cardiac pacing postoperatively; 4.6% of these underwent predominantly valvular surgery and 0.6% had coronary bypass. The most important factors appeared to be: 1) preoperative evidence of a conduction disorder; 2) advanced patient age; 3) dense calcium in the aortic annulus; 4) valvular surgery and, especially, tricuspid valve surgery; and 5) poor myocardial protection. Postoperative permanent pacing had a considerable impact on patient morbidity from maintenance operations; most complications were lead-related problems.

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We have found conditions for the reproducible, direct laser fabrication of sharp conical tips with heights of about 1 m and apical radii of curvature of several tens of nanometers. An individual cone is formed when single-crystalline silicon on a silica substrate is irradiated with a single pulse from a KrF excimer laser, homogenized and shaped to a circular spot several microns in diameter. Atomic force microscopy and field-emission scanning electron microscopy were used to characterize these structures. A simple mechanism of formation based on movement of melted material is proposed. Our results suggest that this technique could produce even smaller structures by optimizing the laser processing geometry.

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