Evidence Of Cavitation Research Articles

Physics of ultrasonic surgery using tissue fragmentation: Part II

Ultrasonic surgical aspirators typically operate at a frequency between 20 and 60 kHz. A vibrating hollow horn moves against the tissue and suction is applied. The interaction causes tissue to fragment; the fragmented material is then aspirated. However, the mechanism of interaction is poorly understood: the most common view relates it to cavitation, probably active in concert with other mechanisms, including the direct jack-hammer effect, shock-induced stress, acoustic microstreaming and shearing stress. It has also been attributed to chopping, which will produce emulsification. This article reports a study that collected and analyzed ultrasonic, high-speed photographic, visual/optical and electrical data for a 23-kHz unit operating in water and a range of fresh pig tissues. The primary mechanism for tissue fragmentation is shown to be horn-tip impact and other mechanical forces, operating in combination with hydrodynamic forces applied to the tissue on the forward stroke in each cycle. No evidence of cavitation in tissue was observed.

Evidence for cavitation during superplastic deformation of an AlCu eutectic alloy

Evidence for cavitation during superplastic deformation of an AlCu eutectic alloy

Ductility at high temperature and creep behaviour of directionally solidified Ni-Cr-base alloys

Tests have been carried out at several constant plastic strain rates in the temperature range 500°–900° C on directionally solidified Nimonic 80A and on MAR M 246 in the directionally solidified, single-crystal, and conventionally cast forms. Creep tests have also been completed on these alloys at 750°C for Nimonic 80A and at 850°C for MAR M 246 at stresses between 185 and 309 N mm−2 and 300 and 500 N mm−2, respectively. The results show that the ductility of Nimonic 80A was substantially improved by directional solidification compared with the values expected from the wrought material under the same conditions of test. In the case of MARM 246, the directionally solidified material was, in general, more ductile than the conventionally cast, the margin being greatest for the higher temperatures and the slowest rate of strain. The single-crystal material showed only a slight further improvement in ductility at the lowest temperature of test. The creep properties of all three forms of MARM 246 were similar, but the stress dependence of the minimum creep rate was unusually high for all the cast alloys including the Nimonic 80A. In the absence of transverse grain bounderies, fracture in the Nimonic 80A appeared to originate from irregularities in the cast structure, i.e. kinked grain boundaries and micro pores. In the MARM 246, on the other hand, there was little evidence of cavitation, and cracking was often associated with carbide particles. Cracks tended to propagate through the matrix in directionally solidified material or through carbide particles in the interdendritic regions in the conventionally cast form.

Evidence for cavitation in superplastic Zn-22 pct Ai of very high purity

The cavity formation of very high purity Zn--22% Al was studied. Results confirm that cavities are nucleated in the Zn--22% Al eutectoid during superplastic deformation, and the extent of cavitation is essentially identical to an alloy of commercial purity (190 ppm impurities). (FS)

Hemophilus influenzae pneumonia in adults

Hemophilus influenzae pneumonia was diagnosed in 41 adult patients based on cultures of blood, pleural fluid or transtracheal aspirate. Bacteremia occurred in all age groups, but was most frequent in patients over the age of 50 years with severe underlying pulmonary disease. Chest films usually demonstrated multisegmental or multilobar infiltrates without evidence of cavitation. Pleural involvement was evident in half of the patients, although empyema occurred infrequently. Mortality was almost always associated with serious underlying diseases and bacteremia. Encapsulated strains of H. influenzae (usually type B) were identified in 18 of 22 (82 per cent) patients. The use of transtracheal aspirations and the adoption of routine subculturing of blood cultures on chocolate agar appear to be important factors in our increased recognition of this disease.

Scanning Electron Microscopy of Rubber Tear

Abstract A relatively simple technique has been described which allows observation of the deformation zone at tear tips in rubber specimens. Investigation of various rubbers revealed qualitative information about the type of yielding that occurs in the deformation zone under different conditions. The initial appearance of the tear tip in nitrile, polybutadiene (both with and without carbon filler), and natural rubber suggests a process of stretching followed by rupture and then relaxation onto the tear walls. Only in the case of a fluoro-elastomer was there evidence of cavitation, although microcavitation (of sizes ≪1 µm) may be occurring in the other rubbers at much higher magnification. On the other hand, aging in laboratory air had the dramatic effect of producing fibrous and nodular networks in the tear tip material of all the rubbers except the fluoroelastomer. In the first few hours, the network structure developed as cavities (Figure 9), but after 24 h the network was fully developed across the tear. The aging process is very likely an ozone attack not only on the rubber under stress at the tear tip, but also on the rubber on the tear wall. It is quite possible that there were residual stresses in the material on the wall which facilitated attack. Chain scission appeared to be allowing the rubber to relax by viscous flow under the action of surface forces. These results point up the need to distinguish between failure controlled by pure stress and failure assisted by oxidation/ozonolysis in studies of slow tear growth in rubbers. The SEM technique also provides information about fillers. Their elemental composition can be determined by XES, and some qualitative information can be gained about their adhesion to the matrix and their effect on tear tip yielding.

Sclerosing haemangioma of the lung

Vascular tumours of the lung are classified according to their cell of origin as haemangiopericytomas, haemangioendotheliomas, or sclerosing haemangiomas (Feldman and Seaman, 1964; Mori, 1968; Tralka and Katz, 1963). Of these three types, sclerosing haemangioma is the most common (Feldman and Seaman, 1964; Mori, 1968; Tralka and Katz, 1963), yet only 18 have been well documented in the English literature (Arean and Wheat, 1962; Edwards and Taylor, 1938; Goorwitch and Madoff, 1955; Haas et al., 1972; Hill and Eggleston, 1972; Liebow and Hubbell, 1956; Magri et al., 1957; Mori, 1968; Rubin et al., 1958; Solomon and Wessely, 1959; Turunen et al., 1957). We are reporting an additional case of pulmonary sclerosing haemangioma, to our knowledge the first in the radiologic literature. An asymptomatic, 40-year-old woman had a routine chest X ray film in March 1975, and a solitary, right lung mass was detected. Sputum culture and cytologic findings were negative. Results of needle biopsy of the mass suggested alveolar cell carcinoma but were not diagnostic. In April 1975, the patient was admitted to our institution for thoracotomy. She had no history of cough, haemoptysis, dyspnoea, or recurrent respiratory infections. Physical examination was unremarkable. Haematocrit was 35%; white blood cell count was 5,900 mm3 with a normal differential. Chest X ray films demonstrated a well-defined, oval, somewhat lobulated, 2-cm mass in the right lower lobe (Fig. 1). On the tomogram, the mass appeared homogeneous, without evidence of cavitation or calcification; no other lesions were seen (Fig. 2).

Evidence for cavitation in fluorocarbon liquids subjected to alternating electric fields

The use of alternating voltages in the study of pre-breakdown processes in fluorocarbon liquids has enabled frequency-dependent effects to be identified with the cavitation process. Acoustic and optical techniques have shown that the events leading to breakdown are intimately connected with stress-induced cavitation in these liquids. The necessary nucleation has been discussed in terms of particle contamination and shock wave propagation in the liquid and suggestions are made concerning the nature of the pre-breakdown light emission.

Pulmonary Rheumatoid Nodule With Cavitation and Chronic Lipid Effusion

Unusual findings were noted in a case of nodular rheumatoid pulmonary disease with roentgenographic evidence of cavitation. Biopsy specimen of the cavitated nodule was identical microscopically to the patient's typical subcutaneous rheumatoid nodule. Of further interest was the associated pleural effusion with low glucose concentration, high total lipid content, and extremely high lactic acid dehydrogenase level. To the best of the author's knowledge, chronic lipid effusion and elevated lactic acid dehydrogenase have not been previously reported in association with rheumatoid disease of the lung. The diagnostician must consider rheumatoid disease in the differential diagnosis of cavitary pulmonary lesions in the patient with associated rheumatoid disease. Adequate biopsy and microscopic confirmation of the process are still required for definite diagnosis.

Silico-Tuberculosis as Seen in a Large Industrial Center

IT has been said that the problem of silicosis in industry has been pretty well eliminated as far as present-day hazards are concerned, and further, that in those States in which compensation laws dealing with this condition have been established, most of those cases suffering from silicosis have been brought to light and very few new ones are now appearing. This is to a large extent true in the experience here reported as far as preventive practices in the larger industries are concerned, but there is still an appreciably significant number of men who were exposed to silica dust years ago and who are coming to light now with silicosis and superimposed tuberculosis. It is, therefore, the purpose of this discussion to report the experience with silico-tuberculosis of the Herman Kiefer Hospital Tuberculosis Division over a period of five years from 1933 to 1938. This hospital serves the industrial community of Detroit, which would suggest that there are or have been many possible silica dust hazards in the various industries represented in such an area. In addition, the migration of many workers from other parts of the country to Detroit in recent years has resulted in many men who have worked in hazardous dusty trades for longer or shorter periods coming to this community and later being found to have silico-tuberculosis. In these cases the silicosis was undoubtedly the result of exposure elsewhere as, in many instances, no dust hazard existed in the new work in which they engaged. The diagnosis of silico-tuberculosis is not always easily made and must rest on making a diagnosis of two co-existing conditions. In making the diagnosis, then, the following points for tuberculosis must be considered: the appearance of the roentgenogram, the presence or absence of tubercle bacilli in the sputum, evidence of cavitation, and symptoms. For silicosis a typical roentgenographic appearance, history of prolonged exposure to silica dust, and symptoms are important. Autopsy findings, of course, are final in confirming the diagnosis of silico-tuberculosis, though it is well known that it requires careful observation on the part of the pathologist to recognize both the conditions as being present. From Oct. 1, 1933, to Sept. 30, 1938, a five-year period, there were admitted 171 men in whom a tentative diagnosis of silico-tuberculosis was made on admission. More careful study revealed, however, that only 132 of these were definitely confirmed as having silico-tuberculosis, as shown in Table 1.