Number Of Debris Particles Research Articles

Optical properties and laser damage performance of SiO2 irradiated by high-power pulsed electron beam

A 60 kW electron beam is used to study the microstructure and optical property evolutions as well as laser induced damage threshold of fused silica after irradiation at room temperature. Optical microscopic results indicate that cracks appear at the surface of SiO2 after electron beam irradiation, owing to the thermal effect, and that the crack density and size increase with increasing radiation dose. The morphology of the surface cracks is analyzed by using atomic force microscope and the width of crack is about 1 μm. In addition, there are a large number of debris particles with sizes of 0.1-1 μm on the surface. From the optical absorption spectrum of each of all samples, a weak absorption peak at 394 nm is observed and the absorbance increases at the beginning then decreases with increasing electron-radiation dose. Before and after irradiation, three absorption bands at 460 nm, 496 nm and 520 nm are clearly observed and their intensities first increase and then decrease, which is consistent with the results of absorption spectra. The effect of electron dose on the laser induced damage threshold (LIDT) at 355 nm is investigated and the results indicate that the LIDT decreases with increasing dose. At the lower electron doses, the color centers are responsible for the decrease of LIDT. However, at the higher electron doses, the decrease of LIDT is due to the light modulation and absorption induced by microscale cracks and debris particles at the surface of irradiated fused silica.

Routine aspiration method during filter-protected carotid stenting: histological evaluation of captured debris and predictors for debris amount

A routine aspiration method in filter-protected carotid artery stenting (CAS) has been reported recently in which the proximal internal carotid artery (ICA) blood column was aspirated using an aspiration catheter after postdilatation regardless of flow state on digital subtraction angiography. We examined the debris particles captured by this method. The routine aspiration method was used in 71 CAS procedures. In two procedures, captured debris particles were examined histologically. In the remaining 69 procedures, the size and number of debris particles were measured under a stereoscopic microscope, and then relationships between the amount of debris particles and clinical variables were evaluated using multivariate regression analysis. Histologically, the captured debris contained platelet-precipitating, thrombotic, lipid-rich fibrous and calcified material. The number of debris particles ≥1 mm was 19.6 ± 12.1 (mean ± SD) in 60 procedures with normal flow and 25.9 ± 17.2 (mean ± SD) in 9 procedures with slow/stop flow. Multivariate regression analysis demonstrated that extension of a proximal ICA angulation was an independent predictor of the amount of debris particles with a maximum diameter of either ≥1 mm or <1 mm but ≥0.5 mm (p < 0.05). The captured debris appeared to originate from atheromatous plaques. If the routine aspiration method had not been used in the present series, the debris might have migrated into intracerebral arteries. Restriction of the extension of a proximal ICA angulation might reduce the amount of debris associated with CAS, especially when the proximal ICA angulation is pronounced.

Routine Use of Debris Aspiration Before Retrieval of Distal Filter Protection Devices in Carotid Arterial Stenting: Analysis of Captured Debris and Evaluation of Clinical Results

Distal filter protection allows for continuous cerebral perfusion during carotid artery stenting (CAS), although a higher risk of debris migrating into the cerebral arteries compared with other protection systems has been reported. To improve the extent of debris capture, we used routine aspiration of blood located proximal to the filter in the internal carotid artery blood column before retrieval of the filter device. Of 71 CAS procedures with distal filter protection, routine aspiration was performed in 41 procedures. The size and number of debris particles in each aspirated blood sample were measured under a stereoscopic microscope in 30 consecutive procedures with routine aspiration. Occurrence of periprocedural neurological events was compared between 41 procedures with routine aspiration and the other 30 without routine aspiration. In the aspirated blood, debris particles ≥ 500 μm and ≥ 1000 μm in the longest diameter were observed in 30 (100%) and 28 (93.3%) procedures, respectively. The number of particles ≥ 1000 μm was significantly larger in the second through fourth blood aspirates vs the first aspirate (P < .05). Occurrence of periprocedural neurological events was significantly less frequent in the routine aspiration group (0 of 41 procedures) than in the conventional method group (7 of 30 procedures) (P < .05). The use of routine aspiration during CAS with distal filter protection possibly reduced periprocedural neurological events by increasing the proportion of debris captured. To improve the capture of debris particles, at least 4 repeated aspirations are advisable during each CAS procedure.

Behind-armor debris from the impact of hypervelocity tungsten penetrators

Behind-armor debris is the main mechanism by which targets are destroyed by projectile impact. The behind-armor debris generated from the impact of tungsten heavy alloy (THA) penetrators with a length-to-diameter ratio ( L/ D) of 20 against 6061-T6 aluminum targets was characterized. Behind-armor debris characteristics described were the number of debris particles, their positions, and their size distribution. Experiments were performed against two nominal target thicknesses, 100 and 150 mm, and covered a velocity range from 1.7 to 2.6 km/s. Two methods of obtaining data were used—radiographs were taken of the behind-armor debris, and perforation patterns were generated on steel witness packs placed behind the aluminum target. Debris particles recovered from the witness packs were also studied. Results are discussed for the effect of changes in target thickness and impact velocity on behind-armor debris particle characteristics.

Predicting the abrasive wear of ball bearings by lubricant debris

Solid debris particles in a lubricant can become entrained into the contacts of ball bearings. The particles damage the bearing surfaces. This can lead to rolling contact fatigue failure or material loss by three body abrasion. This work concentrates on modelling the later process for brittle debris materials. A brittle particle is crushed in the inlet region and the fragments are entrained into the contact. Rolling bearing contacts (because of the high degree of conformity) are subject to contact microslip. When this slip takes place, the trapped particle scratches the bearing surfaces. Repeated scratching by many particles results in substantial material removal. Although this failure mechanism is usually not as rapid as debris initiated fatigue, it is frequently important in mineral handling or desert environment rolling bearing applications. A simple model has been developed which considers the wear as the sum of the individual actions of each particle. The number of debris particles is determined by considering the volume of oil entrained into the bearing contacts and an empirically derived `particle entry ratio'. The abrasive action of each particle is determined by the volume of material displaced during sliding and another empirical factor for the proportion of this removed as a wear particle. The predictions are compared with some experimental results. The correlation between bearing wear and the debris particle size is encouraging.

Isolation and quantitation of debris particles around failed silicone orthopedic implants

Silicone elastomer implants have a relatively low rate of complications, but inflammatory reactions to debris have been reported. To characterize the size and number of debris particles, we isolated and quantified the debris particles present in the periarticular tissues of 10 patients with failed silicone wrist, elbow, or finger implants. Five rheumatoid synovia without implants were used for negative controls. The number of particles ranged from 0.99 to 24.8 x 10(9) per gram (dry weight) of tissue, and nearly all particles were silicone, as determined by x-ray spectroscopy. The implantation duration ranged from 3.2 to 10.6 years, and for the five wrist implants, the number of particles correlated with duration in vivo. The particles were small (mode particle diameter was 0.59 +/- 0.057 micron). These results suggest that billions of particles, most of which are smaller than 1 micron, are present adjacent to failed silicone implants, and may be associated with inflammation and bone resorption.