Erosion appearance

Typical of the vermilion of the lower lip. Diffuse scaling, with a blotchy and atrophic appearance. When erosions appear, the occurrence of a squamous cell carcinoma must be considered. 

Prominent changes in the cells have been revealed after 30 min of irradiation. Besides the oedema of the cytoplasm and nuclei swelUng, crater-like erosions appeared on the luminal surface of the endotheUocytes (Fig. 30.1b). Intercellular spaces became wider, and fibrin thread and single erythrocytes were found in these spaces. In some zones the longitudinal folds of the intima were smoothed, but the endothelial layer remained intact. Such zones may correspond to the sub-endothelial oedema. These changes remained for 6 h after kradiation. One day later the microrelief of the aorta s intima returned to normal. 

The primary feature of the main asteroid belt is its great depletion in mass relative to other regions of the planetary system. The present mass of the main belt is 5 X 10 m , which represents 0.1 -0.01 % of the solid mass that existed at the time planetesimals were forming. There are several ways the main asteroid belt could have lost most of its primordial mass. Substantial loss by collisional erosion appears to be mled out by the preservation of asteroid Vesta s basaltic cmst, which formed in the first few million years of the solar system (Davis et al., 1994). More plausible models are based on the existence of orbital resonances associated with the giant planets. 

A 28-year-old bone marrow transplant recipient with chronic renal insufficiency developed genital condylo-mata resistant to standard therapy. After application of topical cidofovir (1% daily for 5 days, then 4% for 12 days) the lesions improved but local erosions appeared. He developed acute renal insufficiency with features of tubular acidosis on day 19. He recovered after cidofovir withdrawal. 

Usually, holding a foil (for example, from Ti) in an aluminum melt without ultrasonic action for up to 1 h does not result in its wetting and subsequent metallization. Under ultrasonic treatment, a strong diffusive layer forms at the foil surface after 1-3 min of exposure, and typical punctures—traces of cavitation erosion—appear on the foil after 5—15 min (Figure 10). 

C. Erosion Due to Dissolved H2 and O2. One easily calculates that, even in the central rod, the formed H2 is 1/3, the formed O2 is 1/6, of the amount necessary to saturate the water at 100 and 1 atm pressure. Actually, the pressure is higher than this. Nevertheless, tests would be desirable concerning the erosion by such a liquid and the pressure would have to be increased if erosion appears to occur. 

Gastric erosions are aphthous ulcers that do not penetrate the muscularis mucosa. They are most often related to H. pylori infection (Levine and Rubesin 1995). Other causative agents include alcohol, salicylates, and nonsteroidal anti-inflammatory drugs (NSAIDs). They are also seen in critically ill patients due to multiple trauma, sepsis, shock, etc. At double-contrast barium studies, gastric erosions appear as shallow small, 1-2-mm-diameter collections of barium surrounded by a radiolucent rim of oedema an appearance mirrored at endoscopy with a haemorrhagic centre and oedematous rim (Fig. 5.2a,b) (Levine and Rubesin 1995 Sohn et al. 1995 Dheer et al. 2002). H. pylori infection is also related to the presence of lymphoid follicular hyperplasia, which is commonly present in patients with peptic ulcer disease (Fig. 5.3a,b) (Torigian et al. 2001). 

Fracture and/or erosion appears in specimens heated by the electron beam from the thermal shock testing apparatus. When the specimen is thin (SI mm), fracture often occurs within 1 s of heating. When the specimen is thick ( 10 mm), erosion occurs. The extent of erosion and the thickness of the specimen at which fracture occurs, say just after 1 s of heating, depend on the heat flux and the material properties. 

Economic Aspects. Isophorone was available at 1.87/kg ia October 1994. The sole domestic producer of isophorone is Union Carbide however, Hbls is by far the largest isophorone producer ia the world. Other significant producers are Hsted ia Table 9. Despite the erosion of some of the historical solvent uses of isophorone, the expanding derivatives market for this product appear to sustain its production ia the short term. 

It is often localized at areas where water changes direction. Cavitation (damage due to the formation and coUapse of bubbles in high velocity turbines, propellers, etc) is a form of erosion corrosion. Its appearance is similar to closely spaced pits, although the surface is usually rough. 

Figure 11.35 A small forest of erosion cones typical of the appearance of each site. (Magnification 7.5x.)...

A combination of pitting and uniform thinning has the appearance of a corrosion-erosion (Figure 3). The tube wall is thinned, the surface is rippled, and some scattered pits may be visible. Reaction products are essentially the same as those formed in pitting and uniform thinning. 

Very rapid and highly localised pitting is sometimes observed on components exposed to very turbulent flow conditions leading to cavitation in the stream. In general, these conditions appear to induce corrosion rather than erosion on cast iron surfaces, in contradistinction to what usually happens with other metals, apparently because the erosive component of the liquid flow scours away corrosion-stifling films and allows the development of very active electrochemical cells on the exposed metal surfaces . 

The final estimation of the value of ay may appear tedious and several assumptions are made in its derivation, but experimental evidence suggests that it may be used with reasonable accuracy to assess the levels of potentially damaging cavitation erosion. In small valves with nominal bores up to 65 mm cavitation inception occurs in intermittent bursts when the value oy is approximately unity. The cavitation becomes continuous and audible as Oy is reduced to about 0.6, but the risk of damage does not become significant until the value falls below 0.4. As a design criterion the condition of light, steady noise has been described by Tullis as the critical level and is sug-... 

There has been renewed interest over the last few years in erosion-corrosion, i.e. essentially velocity-assisted corrosion since it appeared in the feed systems of certain nuclear plant. This prompted extensive experimental investigations . Erosion-corrosion is influenced by many factors-chemistry, flow, temperature, heat flux, and whether one or two phases exist. It also varies with the material, resistance increasing from mild steel, through 1% Cr-Mo to 2% Cr-Mo. 

Since the publication of these articles no major breakthroughs in erosion, or rather erosion prevention, have been made. However, several patents claiming methods and means of minimizing gun barrel erosion have appeared recently. These are abstracted below ... 

Generally speaking, these studies of erosive burning have been able to correlate the observed effects. Until the structure of the combustion zone is defined and quantitatively characterized in detail, it would appear that the currently available bases for correlating erosive-burning data are adequate. 

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