Kinds Of Cavities Research Articles

The characteristics of cavitation during superplastic deformation of a warm-rolled AlLiCuMgZr alloy

The process of superplastic forming has become important in numerous commercial applications. However, there may be some deleterious defects on the properties of superplastically-formed components due to the presence of minor levels of cavitation introduced during the forming process. Thus, it is important to obtain information on nucleation, growth and interlinkage of cavities in a wide range of superplastic materials. Two different thermomechanical processing routes may be employed to develop fine grain sizes conducive to superlasticity in Al-Li alloys. In one of them, a fine grain size microstructure is obtained by static recrystallization prior to superplastic deformation, and in another, a fine grain size microstructure is obtained by deformation-induced recrystallization during the initial stage of superplastic deformation. The deformation-induced recrystallization of a cold (or warm)-rolled Al-Li alloy is strongly dependent on the strain rate microstructural change during the initial stage of superplastic deformation due to deformation-induced recrystallization. There have been some studies dealing with cavitation in superplastic Al-Li alloys. However, there is no research work reported on the effect of deformation-induced recrystallization on the characteristics of cavitation during superplastic deformation of a warm-rolled Al-Li alloy. This paper deals with the relationship between deformation-induced recrystallization and cavitation characteristics during superplastic deformationmore » of a warm-rolled Al-Li-Cu-Mg-Zr alloy. The results show that there are three kinds of cavities. The first includes the fine cavities formed at the beginning stage of deformation, the second the large cavities formed around the intermetallic particles and the third the grain boundary cavities. All three kinds of cavities are closely related to deformation-induced recrystallization.« less

Contribution à l'étude des cavités karstiques du Djurdjura (Algérie). Description morpho-hydrogéologique et cadre évolutif

In North-Africa, the karst of Djurdjura Mountains is important because it shows high-alpine characters. In others papers, we have studied shallow morphology and speleological explorations. Here, we describe the caves: morphology, qualitative hydrology and fillings. These cavities are replaced in their morpho-structural context. We make distinctions between kinds of cavities. Gulfs and resurgences characterize high-alpine karst which is actual. Other caves that have their opening at the middle of slopes are dry, disconnected of actual morphological context. They belong to past karstification phases. From the synthesis of those elements, we show that it is possible to use karstic data in the reconstruction of morpho-structural evolution of a country.

Clathration by phenol and quinol. Part 1.—Equilibria

Clathration isotherms have been measured over a range of temperatures for Kr, Xe, CH4, C2H4, C2H6 and CO2 in β-phenol and for Xe, Kr and CH4 in β-quinol. Isotherms in β-phenol, which contains two kinds of cavity, do not obey Langmuir's isotherm, but those in β-quinol, with one type of cavity only, do satisfy this equation. Equilibrium constants and heats of intercalation were obtained for the three gases in β-quinol; and heats of intercalation for the six gases in β-phenol at the degrees of filling at which the β-phenol host lattice is just stabilized. For phenol, also, dissociation pressures were measured over a range of temperatures and heats of formation of the clathrate phases from α-phenol derived. The heat of transformation α-phenol →β-phenol varied according to the guest species for which heats of formation and intercalation were evaluated.

The Healing of Cavities in Pulmonary Tuberculosis: Roentgenographically Observed

ROENTGENOLOGY has a right to be proud of the part it has played in developing the modern treatment of pulmonary tuberculosis. The memory of most of us extends back to the time when clinicians scouted our timorous suggestion that we could offer valuable aid in diagnosing tuberculosis and following the progression or retrogression of its tissue changes. To-day, we have difficulty in keeping pace with the claims of this same group regarding the important place of our art in clinical medicine. It is a clinician, and not a roentgenologist, who is responsible for the assertion that activity in the tuberculous lung cannot be detected by the stethoscope so positively as it can be shown by the x-ray film. It is a clinician, and not a roentgenologist, who has stated that we must depend on the x-ray appearances, rather than on physical signs or symptoms, to indicate when a lung lesion is healed. It is a clinician who asserts that only 60 per cent of cavities are found by physical examination, while 95 per cent of them are shown by x-ray examination. We modestly agree to these statements, at the same time calling attention to the fact that they are not the claims of over-enthusiastic x-ray specialists, but the matured confessions of eminent clinicians who are experienced in the observation and treatment of tuberculosis. Graeff's statement, in 1921, that development of a lung cavity is a death sentence for the unfortunate tuberculous patient, marked off a new epoch in the treatment of the disease. Not all workers are in entire agreement with this gloomy prognosis, but, in spite of numerous exceptions, the majority of critical observers accept it as substantially correct—Pinner, Fischel, Barnes and Barnes, and Sprungman, among others. There are, of course, many kinds of cavities, of various sizes and locations in the lung-field, and such a general statement as that by Graeff naturally is subject to many exceptions. However, so universally is it now accepted that the modern phthisiologist adopts as the basis for the treatment of lung tuberculosis that “the cavity must be closed,” and persistently follows the indicated course to bring this about, whether that course be medical or surgical. Avoiding statistical data and clinical reports, this paper aims to present the subject by a series of cases of increasing complexity and difficulty, in order to illustrate how the problems of cavity formation are met and solved. Particularly does this presentation aim to illustrate the necessity for close co-operation among clinicians, surgeons, and roentgenologists in solving the problems of diagnosis and treatment of lung cavities of tuberculous origin. It must be remembered that, whatever the size and appearance of the cavity, it is the product of a single pathologic process in different stages. The structure of the cavity depends on the degree of fibrosis which indicates the stage of its developmental cycle.

On some peculiarities in the Microscopical Structure of Crystals, applicable to the determination of the Aqueous or Igneous Origin of Minerals and Rocks

ABSTRACT In this paper the author showed that when artificial crystals are examined with the microscope, it is seen that they have often caught up and inclosed within their solid substance portions of the material surrounding them at the time when they were being formed. Thus, if they are produced by sublimation, small portions of air or vapour are caught up, so as to form apparently empty cavities; or, if they are deposited from solution in water, small quantities of water are inclosed, So as to form fluid-cavities. In a similar manner, if crystals are formed from a state of igneous fusion, crystallizing out from a fused-stone solvent, portions of this fused stone become entangled, which, on cooling, remain in a glassy condition, or become stony, so as to produce what may be called glass- or stone-cavities. All these kinds of cavities can readily be seen with suitable magnifying powers, and distinguished from each other by various definite peculiarities.