Effusion definition

An effusion formula for the crystal diffusivity (Dc) is obtained from the expression for in Equation 12. The average absolute flux of molecules across the face Sc is NPj /ht, with an equal flux in the opposite direction at equilibrium. For self-diffusion the equilibrium is not disturbed, and if the difference in number-fraction of labelled molecules between adjacent cells is Ax, the definition of diffusivity yields ... 

The possibility that talc can cause respiratory failure was explored further in 1997 (24). ARDS occurred in four of 338 patients treated with talc poudrage (2 g) via thoracoscopy. All four had mahgnant effusions and aU developed bilateral pulmonary infiltrates, hjrpoxia, and hypotension within 24—48 hours of talc insufflation. All four required mechanical ventilation and three died. Bronchoalveolar lavage was performed in all four and talc crystals were recovered from lavage fluid in each case. Furthermore, at autopsy in one patient, talc crystals were found in almost every organ, showing that systemic distribution of talc did occur after pleurodesis. However, as the authors acknowledged, it was not possible to definitely attribute the symptoms in these patients to the talc pleurodesis. Studies in animals have shown systemic distribution of talc after pleurodesis (25). However, systemic dissemination may occur in all patients treated with pleurodesis and does not confirm that this is the cause of respiratory failure documented in a small number of patients. 

Definition The vaporization coefficient, is usually defined as the ratio of the actual flow of gaseous decomposition product J to the flow Jmax coming from an effusion cell, in which, it is assumed, decomposition products are in an ideal equilibrium with the reactant. For many substances, as found from comparative Knudsen-Langmuir TG measurements, -C 1, i.e., their free-surface decomposition proceeds much more slowly than would be expected from effusion observations. It is a common practice to explain this discrepancy by a multistage character of the evaporation process, by surface relief peculiarities or by impurities and defects (imperfections) in the reactant lattice. 

The American Society for Testing and Materials (ASTM) definition An inorganic product effusion that has cooled to a rigid condition without crystallizing. 

The method uses speeial effusion cameras with holes of a definite form, maintaining high vacuum in the system. The method is widely applied to the measurements of a vapor pressure of low volatile substances. 

The central KEMS equation can be derived now that the Knudsen cell vapor source and mass spectrometer have been described. This follows directly from the vapor flux in the molecular beam selected from the distribution of material effusing from the Knudsen cell (molecular beam flux equation) and the definition of the ionization cross section (Equation 48.18). However, in accordance with the aim of identifying factors that affect the measured ion intensity and that are unrelated to sample temperature and composition, it useful to rewrite Equation 48.18 in terms of the number of ions produced per second in the elementary volume dv in the region defined by the intersection of the molecular and electron beams, ni(E) [71,80] (this is prior to the formation of the ion beam) ... 

Recently, Sameshima(24) has measured the rates of flow of various simple gases through a compact unglazed earthenware plate. The rates of flow definitely did not obey the Knudsen formula t = k JM, where t denotes the time required for the effusion at constant pressure of a volume F of a gas of molecular weight M, and where fc is a constant. On the other hand, the law t = k M was accurately obeyed when the gases effused through a platinum plate with a single orifice. For the earthenware plate Sameshima found a formula t = to apply. If the wall was very thin n approached zero, and the simple behaviour of the perforated platinum plate was found. If the wall was thick n approached unity and the equation became t = kij (ij denotes viscosity). 

First, some definitions. You have probably heard of diffusion, which is the spreading out of a substance (perfume, for example) into a container. Effusion is a less familiar term. Effusion refers to the situation of dividing a container into two compartments separated by a wall. A pinhole is made in the wall. One compartment is filled with a gas. The other compartment is evacuated. Remember that gas particles are moving in continuous, random, chaotic motion. Once in a while, a gas particle passes through the pinhole into the evacuated side. 

In infectious tenosynovitis, the effusion tends to be more echogenic and the overlying subcutaneous tissue may appear thickened and hyperechoic due to cellulitis (Brooke Jeffrey et al. 1987 Schechter et al. 1989). However, it must be emphasized that these characteristics are too subtle to allow a definitive diagnosis based on US findings alone. Needle aspiration of fluid, possibly obtained under US guid-... 

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