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We worked out the growth and dissolution rates of an arterial gas embolism (AGE), to illustrate the evolution over time of its size and composition, and the time required for its total dissolution. We did this for a variety of bre...
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We worked out the growth and dissolution rates of an arterial gas embolism (AGE), to illustrate the evolution over time of its size and composition, and the time required for its total dissolution. We did this for a variety of breathing gases including air, pure oxygen, Nitrox and Heliox (each over a range of oxygen mole fractions), in order to assess how the breathing gas influenced the evolution of the AGE. The calculations were done by numerically integrating the underlying rate equations for explicitly multi-component AGEs, that contained a minimum of three (water, carbon dioxide and oxygen) and a maximum of five components (water, carbon dioxide, oxygen, nitrogen and helium). The rate equations were straight-forward extensions of those for a one-component gas bubble. They were derived by using the Young-Laplace equation and Dalton's law for the pressure in the AGE, the Laplace equation for the dissolved solute concentration gradients in solution, Henry's law for gas solubilities, and Fick's law for diffusion rates across the AGE/arterial blood interface. We found that the 1-component approximation, under which the contents of the AGE are approximated by its dominant component, greatly overestimates the dissolution rate and underestimates the total dissolution time of an AGE. This is because the 1-component approximation manifestly precludes equilibration between the AGE and arterial blood of the inspired volatile solutes (O-2, N-2, He) in arterial blood. Our calculations uncovered an important practical result, namely that the administration of Heliox, as an adjunct to recompression therapy for treating a suspected N-2-rich AGE must be done with care. While Helium is useful for preventing nitrogen narcosis which can arise in aggressive recompression therapy wherein the N-2 partial pressure can be quite high (e.g.similar to 5 atm), it also temporarily expands the AGE, beyond the expansion arising from the use of Oxygen- rich Nitrox. For less aggressive recompression therapy wherein nitrogen narcosis is not a significant concern, Oxygen-rich Nitrox is to be preferred, both because it does not temporarily expand the AGE as much as Heliox, and because it is much cheaper and more conservation-minded.
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Electrochemical gas evolution reactions are common but essential in many electrochemical processes including water electrolysis. During these processes, gas bubbles are constantly nucleating on reaction interfaces in electrolyte a...
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Electrochemical gas evolution reactions are common but essential in many electrochemical processes including water electrolysis. During these processes, gas bubbles are constantly nucleating on reaction interfaces in electrolyte and consequently exert an impact on catalysts and the performance. In the past few decades, extensive studies have been conducted to characterize bubbles with emerging advanced technologies, manage behaviors of bubbles, and apply bubbles to various domains. In this review, we summarize representative discoveries as well as recent advancements in electrochemical gas evolution reactions from the perspective of gas bubbles. Finally, we end up this review with a profound outlook on future research topics from the combination of experiments and theoretical techniques, non-negligible bubble effects, gravity-free situation, and reactions under practical industrial conditions.
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A simple equation is derived for the time dependence of the bubble radius for the diffusion-induced slow growth or dissolution of a spherical gas bubble in a viscoelastic fluid of infinite extent. The constitutive equation for a f...
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A simple equation is derived for the time dependence of the bubble radius for the diffusion-induced slow growth or dissolution of a spherical gas bubble in a viscoelastic fluid of infinite extent. The constitutive equation for a first-order fluid and a surface-volume perturbation scheme are used to develop the solution, and the effect of viscosity level and elasticity on the bubble dynamics is considered. (C) 1998 John Wiley & Sons, Inc. [References: 13]
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Gas dispersion from an orifice located in the non-separated flow region of a cylindrical impeller blade was investigated, with four regimes ranging from discrete, orderly bubbling to stable jetting being identified. A prediction o...
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Gas dispersion from an orifice located in the non-separated flow region of a cylindrical impeller blade was investigated, with four regimes ranging from discrete, orderly bubbling to stable jetting being identified. A prediction of the upper limit for the discrete bubbling regime corresponded well with that of previous authors. An algorithm which balances the pressure loss as gas flows through the system with the driving pressure gradient derived from potential flow theory was developed to model the gas flow rate for a given liquid flow past the orifice. Model predictions are compared with experimental measurements. [References: 14]
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A recent paper [Wang et al., Giant and explosive plasmonic bubbles by delayed nucleation, Proc. Nat. Acad. Sci. 115, 7676, 2018] reported on the behavior of a micro-bubble generated in water by the plasmonic resonance of gold nano...
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A recent paper [Wang et al., Giant and explosive plasmonic bubbles by delayed nucleation, Proc. Nat. Acad. Sci. 115, 7676, 2018] reported on the behavior of a micro-bubble generated in water by the plasmonic resonance of gold nanoparticles covering a fused silica substrate. The use of a very-high-speed camera permitted the authors to record several features of the phenomenon: After an induction time, a large bubble impulsively grew, collapsed and then executed nearly periodic oscillations around a very slowly growing mean radius. In this paper we make use of a suitably adapted spherical bubble model to account for these observations. The model considers a spherical bubble and accounts for phase change, heat transfer and gas diffusion both in the bubble and in the liquid. After calibration with some of the reported experimental results, the modified spherical model is able to reproduce many other experimental observations. These results build confidence in the model and enable us to use it to describe several aspects of the phenomenon that are not accessible to experiment: temperature and dissolved gas concentration fields, time dependence and spatial distribution of the vapor and gas content of the bubble and others.
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We have previously hypothesised that the number of bubbles evolving during decompression from a dive, and therefore the incidence of decompression sickness (DCS), might be reduced by pretreatment with hyperbaric oxygen (HBO). The ...
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We have previously hypothesised that the number of bubbles evolving during decompression from a dive, and therefore the incidence of decompression sickness (DCS), might be reduced by pretreatment with hyperbaric oxygen (HBO). The inert gas in the gas micronuclei would be replaced by oxygen, which would subsequently be consumed by the mitochondria. This has been demonstrated in the transparent prawn. To investigate whether our hypothesis holds for mammals, we pretreated rats with HBO at 304, 405, or 507 kPa for 20 min, after which they were exposed to air at 1,013 kPa for 33 min and decompressed at 202 kPa/min. Twenty control rats were exposed to air at 1,013 kPa for 32 min, without HBO pretreatment. On reaching the surface, the rat was immediately placed in a rotating cage for 30 min. The animal’s behaviour enabled us to make an early diagnosis of DCS according to accepted symptoms. Rats were examined again after 2 and 24 h. After 2 h, 65% of the control rats had suffered DCS (45% were dead), whereas 35% had no DCS. HBO pretreatment at 304, 405 and 507 kPa significantly reduced the incidence of DCS at 2 h to 40, 40 and 35%, respectively. Compared with the 45% mortality rate in the control group after 24 h, in all of the pretreated groups this was 15%. HBO pretreatment is equally effective at 304, 405 or 507 kPa, bringing about a significant reduction in the incidence of DCS in rats decompressed from 1,013 kPa.
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The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiatio...
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The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiation. It is clarified that the shape of the spectrum is determined by the temperature inside the bubble and the intensity is determined by the rates of the microscopic processes of the light emission. For a noble-gas bubble, radiative recombination of electrons and ions and electron-atom bremsstrahlung are the dominant microscopic processes of the light emission, and the intensity is mainly determined by the degree of ionization of the gas inside the bubble. It is also clarified that for a noble-gas bubble the pulse width of the light is nearly independent of wavelength. [S1063-651X(99)10708-6]. [References: 27]
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Ocular abnormalities occurring in farmed halibut at the Sea Fish Industry Authority Marine Farming Unit, Ardtoe, Argyll were investigated clinically and post mortem, A significant number of fish were found to have posterior polar ...
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Ocular abnormalities occurring in farmed halibut at the Sea Fish Industry Authority Marine Farming Unit, Ardtoe, Argyll were investigated clinically and post mortem, A significant number of fish were found to have posterior polar cystic changes either causing scleral ectasia or gross degenerative posterior segment abnormalities with chorioretinal atrophy, Other ocular abnormalities included cataract formation and intraocular inflammation, In a small number of fish gas bubble formation in the anterior chamber was observed during capture and examination, It is possible that the lesions seen in these fish are a form of gas bubble disease although super-saturation, the cause of gas bubble disease previously reported in farmed fish, does not occur in the tanks in which these fish are housed, While this paper provides no answers with regard to the aetiopathogenesis of the lesions, it is hoped that it will stimulate discussion, leading to resolution of these questions through a multidisciplinary approach to the problem.
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The transition of shock waves from a bubble medium into a liquid or into another bubble medium with different properties is considered experimentally.Data on the structure,velocity,and pressure in the shock wave incident onto the ...
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The transition of shock waves from a bubble medium into a liquid or into another bubble medium with different properties is considered experimentally.Data on the structure,velocity,and pressure in the shock wave incident onto the interface,transmitted wave,and reflected wave are obtained.Experimental results are compared with numerical data.
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This work aims at understanding the viscous effects of the outer potential flow on Prandtl's boundary layer. For a body moving with a constant velocity in an otherwise quiescent liquid, the non-zero viscous dissipation of the oute...
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This work aims at understanding the viscous effects of the outer potential flow on Prandtl's boundary layer. For a body moving with a constant velocity in an otherwise quiescent liquid, the non-zero viscous dissipation of the outer potential flow gives rise to an additional drag, increasing the drag calculated from the boundary layer alone. The drag is considered in three cases here, on a two-dimensional circular gas bubble in a streaming flow, at the edge of the boundary layer around a rapidly rotating cylinder in a uniform flow, and on an airfoil in a streaming flow. The drag may be computed using the dissipation method or the viscous pressure correction of the irrotational pressure. Such a pressure correction can be induced by the discrepancy between the irrotatinal shear stress and the zero shear stress at a fluid-gas interface, or by the discrepancy between the shear stress evaluated from the boundary-layer solution and that evaluated from the outer potential flow solution at the edge of the boundary layer.
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