Gas Bubbles Research Articles

Evaluation of early and systematic ultrasound examination to determine postoperative dehiscence after small intestinal surgery (114 cases in dogs and cats).

To evaluate the feasibility and reliability of early ultrasound diagnosis for postsurgical bowel dehiscence and find the most reliable ultrasound criteria for dehiscence identification. Additionally, to determine the impact of early ultrasound detection of leakage in terms of survival and duration of hospitalization. Finally, to assess the need for systematized screening or checkup of the population at risk of dehiscence only. 31 cats and 83 dogs. A retrospective, records-based study was performed on 83 dogs and 31 cats (114 total) undergoing small intestinal surgery. Epidemiologic data, clinical signs, surgical procedures, pre- and postoperative ultrasound findings at 48 to 96 hours, hospitalization duration, complications, and general outcomes were recorded. Univariate and multivariate analyses were used to identify ultrasound findings associated with dehiscence. Dehiscence was suspected by ultrasound for 0 of 31 cats and 7 of 83 dogs (2 of 49 for enterotomy and 5 of 34 for enterectomy). Every suspected dehiscence was confirmed during revision surgery except one enterectomy revision, which was declined by the owner. Neither this case nor those without ultrasound evidence of dehiscence developed clinical signs of intestinal leakage. Direct visibility of wall discontinuity, presence of gas bubbles, and liquid in vicinity of the intestinal surgical site were statistically associated with early dehiscence. Survival rate after the second surgery was 83%. Median hospitalization time after the second surgery for dehiscence was 2 days (minimum, 2 days; maximum, 4 days). Postoperative ultrasound examination between 48 and 96 hours after intestinal surgery allows early and sensitive detection of intestinal dehiscence. Survival rate after revision surgery was significantly higher than that associated with septic peritonitis.

Impact of short-term total dissolved gas supersaturation on cognitive function and swimming performance in medaka (Oryzias latipes)

During the flood season, high dam discharge rates result in total dissolved gas (TDG) supersaturation. This condition causes gas bubble trauma and can lead to fish mortality, which poses a significant threat to downstream river ecosystems. Assessing the ecological risks of TDG supersaturation is a challenge in waterpower-intensive river basins worldwide. Few studies have explored the impact of TDG supersaturation on fish behaviours, such as aggression and memory, which are crucial for feeding, reproduction, and predator avoidance. In this study, behavioural tests were conducted in a T-maze to investigate the effects of acute TDG supersaturation on swimming behaviour, aggression, and memory in medaka (Oryzias latipes). The results demonstrated that medaka exposed to TDG levels of 115% and 130% for 2 h had significantly reduced swimming performance.At TDG levels of 100%, 115% and 130%, medaka activity rates in the mirror arm of the maze in the mirror test were 44.34 ± 12.88%, 40.27 ± 15.44% and 35.35 ± 16.07%, respectively. Similarly, the activity rates of medaka in the active stimulus arm of the maze in the memory test were 50.35 ± 14.75%, 40.76 ± 12.51% and 35.35 ± 18.47%, respectively. The behaviour of medaka changed with increasing TDG supersaturation. These findings contribute to the development of an ecological risk assessment model for TDG supersaturation based on memory and aggression in fish and provide data for developing management strategies to mitigate the adverse effects of TDG supersaturation.

Enhanced bubble growth near an advancing solidification front

Frozen water might appear opaque since gas bubbles can get trapped in the ice during the freezing process. They nucleate and then grow near the advancing solidification front, due to the formation of a gas supersaturation region in its vicinity. A delicate interplay between the rate of mass transfer and the rate of freezing dictates the final shapes and sizes of the entrapped gas bubbles. In this work, we experimentally and numerically investigate the initial growth of such gas bubbles that nucleate and grow near the advancing ice front. We show that the initial growth of these bubbles is governed by diffusion and is enhanced due to a combination of the presence of the background gas concentration gradient and the motion of the approaching front. Additionally, we recast the problem into that of mass transfer to a moving spherical object in a homogeneous concentration field, finding good agreement between our experimental data and the existing scaling relations for that latter problem. Lastly, we address how fluid flow around the bubble might further affect this growth and qualitatively explore this through numerical simulations.

Two-group interfacial area concentration model for dispersed gas-liquid flows in large-diameter pipes

Interfacial area concentration (IAC) plays a critical role in heat and mass transfers between gas and liquid phases through the interfaces. As interfacial area increases, mass and heat transfers between phases increase. Hence, a reliable IAC estimation is important for two-phase flow numerical simulations to conduct engineering designs and safety analyses. Gas bubbles show different behavior according to their shapes and sizes. Based on the size, gas bubbles can be classified into two groups that show different characteristics, such as IAC. Hence, two-group modeling helps to achieve a general approach for estimating the IAC in bubbly to beyond-bubbly flow regimes. Available models in the literature use empirical correlations to obtain group one and group two void fractions. These empirical approaches are not reliable for different flow conditions. In addition, these models are usually complex with several empirical constants. This study aims to develop a two-group area-averaged IAC model for upward vertical dispersed flows through large-diameter pipes. In addition, this study proposes using a general approach based on the two-group drift-flux model to calculate two-group void fractions rather than applying empirical correlations. The models are evaluated using 156 two-group measured data points in dispersed flow conditions through large-diameter pipes. The resulting prediction errors for group one and group two IAC models are 24.1 % and 34.2 %, and the errors for group one and group two void fraction predictions are 22.8 % and 25.6 %, respectively.

Trapping of Bubbles in Oil Sands Tailing Ponds

Oil sands tailings ponds are significant emitters of greenhouse gases (GHGs) in Canada. To move beyond making surface or atmospheric measurements of GHG release, it is necessary to understand the physical mechanisms by which gas is generated, bubbles form and then are either released or remain trapped in the pond. We present a review of the physical description of tailings ponds, relevant to gas release models. In particular, we target rheological variations within a pond and how these directly affect the distribution of trapped gas bubbles with depth. Within the limits of the available data, we show how gas content may vary significantly across ponds, and develop data-driven one-dimensional models of gas distribution and rheology.

Non-negligible buoyancy effect on bubbles travelling in horizontal microchannels of comparable size at small Bond numbers

When a gas bubble is transported by a liquid flow confined within a horizontal channel of comparable size, buoyancy effects are usually assumed to be negligible if the Bond number of the flow is less than unity. However, recent experimental studies showed that buoyancy may still significantly impact the bubble dynamics even when Bo≪1, provided that the flow speed is sufficiently small, such that the viscous and inertial forces are weak. To derive a new criterion to assess the significance of buoyancy on the flow of small bubbles in horizontal microchannels, we have performed systematic numerical simulations using the free software Basilisk, covering a wide range of Bond, capillary and Reynolds numbers, Bo=0.004−0.4, Ca=10−4−0.5 and Re=0−100, and exploring the bubble-to-channel diameter ratios db/D=0.2−0.9. We demonstrate that the nondimensional group Bo(db/D)2/Ca is effective in assessing the importance of buoyancy in flows with negligible inertial effects. When Bo(db/D)2/Ca<0.1, buoyancy effects are negligible and the bubble travels along the channel axis. When Bo(db/D)2/Ca>10, buoyancy effects dominate and the bubble travels in the vicinity of the upper wall. For intermediate values, bubbles take equilibrium positions between the channel centre and the wall, and the threshold Bo(db/D)2/Ca=1 is effective in predicting whether bubbles will travel closer to the channel centre or to the wall. The capillary number at the denominator describes the lift force generated by the deformation of the bubble due to viscous shear, which acts towards the channel centre thus opposing buoyancy. Inertial forces significantly alter the shape and equilibrium position of the bubble when the Weber number of the flow exceeds unity and Bo/We<1. Under the action of inertia, bubbles of size comparable to the channel diameter become elongated but remain centred. Smaller bubbles migrate towards the channel wall and do not exhibit a preferential near-wall circumferential position.

Physics of bacterial chemotaxis

Chemotaxis is the ability of some organisms to direct their motion in response to chemical signals. This behavior is important across biological scales, from olfactory navigation in animals, to cell migration in development. Chemotaxis is particularly important for bacteria, many of which are capable of directing their motion towards nutrients and away from toxins. The history of bacterial chemotaxis as a field stretches as far back as the late 19th century when scientists observed various species' ability to localize around gas bubbles and pipettes filled with nutrients. After these initial observations, however, it would take over 60 years for the mechanisms of this behavior to come into focus.

High temperature environmental scanning electron microscopy characterization of transient phase formation during conversion of simulated nuclear waste feed to glass

In-situ High-Temperature Environmental Scanning Electron Microscopy (HT-ESEM) is used to characterize the transient phases formed during the melting of complex glass batch mixtures representing simulated nuclear waste feeds. The first phenomenon that occurs is the formation of oxyanionic salt melt, followed by the reaction of oxyanionic salts with refractory grains containing Si, Al, or Mg through surface reactions to form a molten alkali-alumino-boro-silicate phase. The onset temperatures of gas bubble formation and primary foaming are directly determined from the HT-ESEM measurements. The formation of sulfate lakes as well as the formation of high-temperature transient phases floating at the sample surface are also directly observed and identified. Convection currents are observed and their consequences on glass homogenization are discussed.

On the evolution of magnetohydrodynamic flow instability in shock-accelerated light bubble

The study investigates the evolution of flow instabilities in a magnetohydrodynamic (MHD) environment involving a shock-accelerated light cylindrical bubble. Numerical simulations were conducted using a cylindrical helium (He) bubble accelerated by a shock wave in nitrogen (N2) gas at various magnetic field strengths. The results highlight the impact of magnetic fields on flow morphology, vorticity generation, and enstrophy. The interaction between incident shock waves and the gas bubble revealed significant differences in flow patterns and interface features when magnetic fields were applied. Key findings include the quantification of shock trajectories and detailed visualizations of the evolving flow structure. The study provides insights into the dynamics of shock–bubble interactions under MHD conditions, contributing to the broader understanding of flow instability mechanisms in such complex environments.

Deep Learning Based Method for Dynamic Tracking of Bubbles in Microfluidic Gas-Driven Water Experiments

Using microfluidic chips for gas displacement experiments is an important approach for studying CO2 displacement mechanisms and gas-liquid exchange processes. Analyzing the micro-scale distribution of gas and water during gas displacement enables the optimization of injection strategies, offering valuable guidance for enhancing oil and gas recovery rates. Traditional image processing techniques often face challenges in effectively handle the complex gas-liquid flow dynamics and irregular bubble shapes encountered in gas displacement experiments. To address this challenge, this paper proposes a gas bubble detection and tracking method for gas-driven water microfluidic experiments based on domain adaptation in deep learning and improved YOLOv8. Using the CycleGAN style transfer network to generate numerous simulated bubble training samples significantly reduces the manual labeling workload for bubbles. Additionally, the SE attention mechanism is integrated into the YOLOv8 backbone network to enhance the feature extraction capability of bubbles, and the Fast-PConv Head structure is incorporated into the detection head to enhance detection efficiency. Experimental results demonstrate that using just 20 annotated experimental images, the bubble detection accuracy of the proposed method can reach 94%. Lastly, DeepSORT is employed to track bubbles and visualize the dynamic trends of bubble changes in the form of visual charts. The deep learning approach proposed in this paper provides a new perspective for intelligent analysis of bubbles in microfluidic chip experiments, and future work aiming to its application to the complex multiphase flow field in porous media.

In-depth analysis on the mechanism and reaction efficiency of hydrogen deoxidation in ultra-low carbon steel

The reaction mechanism and efficiency of hydrogen deoxidation used in ultra-low carbon steel are explored in this work. A combination of first-principle simulations and thermodynamic calculations were performed on the reaction mechanisms of hydrogen with dissolved oxygen. Laboratory thermal state experiments were used to analyze the effects of different initial oxygen contents of steel and different hydrogen injection flow rates on the deoxidation ability. The results show that the hydrogen deoxidation mainly happens with the gas state of H2 since there are more reactive sites of H atoms in the gas bubble compared to the dissolved H. Higher initial oxygen content and larger hydrogen blowing flow rate are beneficial to the deoxidation reaction efficiency. With hydrogen deoxidation, the inclusion number can be reduced by half compared to Al deoxidation, and the finally total oxygen content can reach 6.8 × 10-6. The actual reaction hydrogen utilization efficiency fluctuates between 0.13%-1.17% in this study, which can be improved by extending the resistance time of H2 bubbles in the molten steel. This paper provides in-depth theoretical support and atomic-scale insights into the reaction between hydrogen and oxygen in steel, building a foundation for the hydrogen application in the production of ultra-low-carbon steel.

The propagation of negative pulsed discharges facilitated by artificially injected gas bubble in water

Abstract The artificial injection of bubbles into the electrode gap can effectively enhance the performance of underwater pulsed spark discharge (UPSD). It is crucial to investigate the morphology and propagation characteristics of discharges for a comprehensive understanding of bubble-stimulated UPSD. This paper presented an extensive study of negative discharges facilitated by the injected large bubble (with a diameter of 3 mm) in UPSD. The bridging effect of the bubble and the morphology and propagation of discharges were observed through the shadowgraph images captured by a high-speed camera. A numerical model was built to analyse the influence of the bubble on the initial electric field distribution between the electrodes. The characteristics of discharges were notably influenced by bubble parameters and energization conditions. Not in all cases could the bubble play the bridging effect role. The effective range of the bubble was roughly confined to a small region near the HV electrode tip. The experimental results obtained in this paper have certain guiding significance for the practical application of UPSD.

Linear pressure waves in mono- and poly-disperse bubbly liquids: Attenuation and propagation speed in slow and fast and evanescent modes

Using volumetric averaged equations from a two-fluid model, this study theoretically investigates linear pressure wave propagation in a quiescent liquid with many spherical gas bubbles. The speed and attenuation of sound are evaluated using the derived linear dispersion. Mono- and poly-disperse bubbly liquids are treated. To precisely describe the attenuation effect, some forms of bubble dynamics equations and temperature gradient models are employed. Focusing on the dissipative effect, we analyze the stop band that occurs in the linear dispersion relation. In the two-fluid model, even if the dissipation effect is considered, the inconvenience that the wavenumber diverges to infinity in the resonance frequency cannot be resolved. Additionally, the validity of terminating that wavenumber value in the middle of the frequency is demonstrated. To determine a linear dispersion relation that can exactly predict thermal conduction and acoustic radiation, wave propagation velocities and attenuation coefficients are compared with some experimental data and existing models. The results show that thermal conduction and acoustic radiation should be set appropriately to accurately predict the propagation velocity and attenuation except in the high frequency range, the phase velocity in the resonance frequency range, or the attenuation in the high frequency range.

Undrained shear mechanical behaviors of dense gassy sand

Shallow gas can cause many disasters, and it is reported in many marine engineering constructions. For this, it is imperative to understand the impact of gas on the mechanical behaviors of soil. This study investigated the influence of undrained triaxial compression tests on dense gassy sand commonly encountered in coastal areas. Triaxial tests were performed on specimens with saturations of 100%, 99.8%, 95.9%, and 92.7% under confining pressures of 50 kPa and 200 kPa by a self-developed multi-purpose integrated triaxial apparatus (MITA) for gassy soil. The results are presented in terms of monotonic stress‒strain behavior, volumetric behavior, shear strength, and excess pore water pressure (EPWP). The occurrence of gas bubbles has different effects on loose and dense sands, augmenting the undrained shear strength of loose sand while concurrently diminishing that of dense sand. The deviatoric stress of dense sand increases during shear shrinkage, which is similar to the characteristics of loose sand under the influence of gas bubbles. However, following sand dilation, the effect of gas bubbles on deviatoric stress manifests in an antithetical manner. With elevated gas content, the shear strength of dense sand decreases, accompanied by a deceleration in the development of EPWP and a notable increase in volumetric changes. To this end, a microscopic explanation concerning the deformation and evolution of gas bubbles within sand during the shear process was presented to reveal the macroscopic laws governing the undrained shear attributes of dense gassy sand.

Microballistics in fungi and plants

Ballistic movements in biology are powered by muscle contraction, explosive chemical reactions, the formation and collapse of gas bubbles, merger of fluid droplets, and release of hydrostatic pressure. At the macroscopic end of this kinetic carnival we find jumping fleas, violent spider jaws, shrimp claw hammers, and squirting beetles and cucumbers. The speeds are startling, but the mechanisms seem familiar because they occur on a spatial scale that overlaps with our physical experiences. We jump, albeit more slowly than fleas, for example, and it does not seem strange that seeds will spurt from a swollen cucumber when it hits the ground. Ballistics in microscopic dimensions are very different, operating in a seemingly alien world of fluid mechanics where thin air becomes soup and gravity vanishes.

On the focusing effect and interfacial evolution of incident shock waves impinging on double-layer nested heavy gas bubbles

A detailed numerical study about the planar incident shock wave impinging on heavy bubbles with different components and nested structures was conducted. Results show that the shock wave convergence occurs when the incident shock wave impinging on the pure SF6 bubble or CO2-SF6 nested bubbles, which triggers the shock wave focusing and obtains a high transient pressure. Changing the nested position and radius of the SF6 bubble in CO2-SF6 nested bubbles will change the interactional time and relative position of waves to affect the shock wave focusing time and peak pressure. Specifically, the shock wave focusing effect is enhanced, and the peak pressure is increased when the inner bubble is drifted downstream, high density, and larger sized. Thus, the later the shock wave focusing occurs, the higher the transient maximum pressure. The shock wave focusing process of double-layer nested bubbles is presented as follows: the new small shock wave (SS) formed by the intersection between the incident transmitted shock wave and the transmitted shock wave and another new shock wave formed by the collision of diffracted transmitted shock waves move in opposite directions to squeeze the undisturbed region and finally produce a high instantaneous pressure, where SS plays a major role in shock wave focusing. Further, the greater the intensity and velocity of focusing shock waves, the stronger the focusing effect and the higher the transient pressure.

Molecular simulation of gas entrapment near a nanoscale cavity: The interplay of surface wettability, cavity shape, and gas type

Surface cavities play a crucial role in trapping and stabilizing gases, a phenomenon that can be used to facilitate applications in separation and drying processes. Understanding surface characteristics in relation to fluid-surface interactions is essential for designing interfacial properties that enable effective processes. In this work, we adopt a molecular simulation approach to investigate gas adsorption and entrapment in surface defects (cavities), focusing on the influence of surface wettability, cavity shape, and gas type. For this purpose, two types of silica-based surfaces with different levels of wettability (methylated and hydroxylated, with the former having lower water wettability), two cavity shapes with identical opening width and depth (V-shaped and square-shaped), and two types of gas (carbon dioxide and nitrogen) are considered. Our observations indicate that a stable gas nanobubble forms when a methylated surface combines with a square-shaped cavity, regardless of the gas type. In contrast, for hydroxylated surface, gas type becomes important; in a square-shaped cavity, nitrogen forms a stable nanobubble while CO2 is trapped in a monolayer fashion. The interfacial forces between the gas and surface which affects gas configuration near the surface, along with the gas molecules’ self-interaction manifested by solubility, are key to the different entrapment modes for N2 and CO2. Moreover, the square-shaped cavity exhibits better capability in trapping gas compared to the V-shaped cavity due to its higher surface area and smaller opening-to-interior ratio. The results of our molecular simulations can guide the design of surface features and processing systems to modify gas entrapment modes and stabilize nanoscale gas bubbles without altering thermodynamic conditions or fluid properties.

The role of irradiation-enhanced interstitial diffusion in over-pressurizing fission gas bubbles in UO2

Fission gas bubbles in UO2 nuclear fuel have been observed to exhibit pressures in excess of the equilibrium bubble pressure; however, the cause of bubble over-pressurization has not yet been demonstrated. The mechanical interaction between a bubble and the surrounding matrix or grain boundary depends on the internal pressure of the bubble and local stress state, such that over-pressurized bubbles are thought to be responsible for fragmentation and pulverization, when exposed to a temperature ramp. Here, we investigate the role of U interstitials, produced through irradiation, in over-pressurizing bubbles by using a combined molecular dynamics (MD) and cluster dynamics approach. Firstly, the energies for the capture of interstitials and vacancies by bubbles have been determined from MD as a function of the ratio of gas atoms to vacancies that make up the bubble. Secondly, these reaction energies have been implemented in the cluster dynamics code Centipede to predict bubble over-pressurization as a function of temperature for typical fission rates. It was found that there is a transition from low pressure bubbles (at high temperatures) to high pressure bubbles (at lower temperatures). The cause of this behavior was shown to be the creation of irradiation-induced interstitials that are highly mobile relative to vacancies at low temperature; whereas, vacancies are sufficiently mobile at high temperatures to limit bubble pressures. This result supports the hypothesis that over-pressurized bubbles form during steady-state operation and that this behavior is highly sensitive to the local pellet temperature.

Rogue-wave structures for a generalized (3+1)-dimensional nonlinear wave equation in liquid with gas bubbles

This study explores the behavior of higher-order rogue waves within a (3+1)-dimensional generalized nonlinear wave equation in liquid-containing gas bubbles. It creates the investigated equation’s Hirota D-operator bilinear form. We employ a generalized formula with real parameters to obtain the rogue waves up to the third order using the direct symbolic technique. The analysis reveals that the second and third-order rogue solutions produce two and three-waves, respectively. To gain deeper insights, we use the Cole-Hopf transformation on the transformed variables ξ and η to produce a bilinear equation. Using the system software Mathematica, the dynamic analysis presents the graphics for the obtained solutions in transformed ξ, η, and original spatial-temporal coordinates x, y, z, t. These visualizations reveal rogue waves’ intricate structure and evolution, capturing their localized interactions and significant presence within nonlinear systems. We demonstrate that rogue waves, characterized by their substantial height and sudden appearance, are prevalent in various nonlinear events. The equation examined in this study offers valuable insights into the evolution of longer waves with smaller amplitudes, which is particularly relevant in fields such as fluid dynamics, dispersive media, and plasmas. The implications of this research extend across multiple scientific domains, including fiber optics, oceanography, dusty plasma, and nonlinear systems, where understanding the behavior of rogue waves is crucial for both theoretical and practical applications.

Morphological Characterization of Tissue Destruction According to the Distance Between Holmium:YAG Laser Tip and Tissue Surface.

Little is known about the soft tissue destruction by holmium laser clinically used for holmium laser enucleation of the prostate (HoLEP), subject to the distance between the laser fiber tip and the tissue surface. We aimed to investigate the impact of the distance between the laser fiber tip and the phantom surface (DLP) on a soft tissue phantom (STP) in relation to the surgical modes of HoLEP. STP responses to the laser pulses produced by a commercial holmium:yttrium aluminum garnet (Holmium:YAG) laser at an output setting 2 J were observed at different values of the DLP (0, 1, 2, 3, and 4 mm) to look at (1) the single laser pulse-induced cavitation bubble and its penetration into the STP, (2) the STP destruction by a single pulse, (3) the STP destruction by 60 pulses repeated at 12 Hz, and (4) the thermal effect by the multiple pulses visualized on a thermosensitive bovine serum albumin (BSA) STP. We observed that the laser pulse produced a heated gas bubble in water centered at the laser fiber tip. The bubble shape depended on the DLP. The bubble completely penetrated into the STP at the DLP of 0 mm and the penetration decreased with the DLP. The size of the destruction of the STP by the laser pulses was shown to decrease as the DLP increased. Test with the BSA STP showed that, at the DLP of 3 mm, the destruction became insignificant while the thermal effects were still effective. We illustrated that soft tissue destruction by the Holmium:YAG laser is associated with cavitation effects. We provide for the first time experimental evidence for various surgical modes in HoLEP such as incision and hemostasis in relation to the DLP.