Tiny Air Bubbles Research Articles

Analysis on degassing at microgravity condition

For the future diversity and sustainability of the International Space Station, the manned flight time will be greatly increased, and the water required will be greatly increased as well. It is particularly important to deal with resources in more detail. In the process of treating drinking water, tiny air bubbles may be created. Bubbles can form in the Water Recovery and Management System (WRMS) on the ISS due to gas dissolution, microgravity environment, chemical reactions, and microbial metabolism. Water under pressure can dissolve gases. In the ISS, if water comes from a high-pressure environment to a lower one, gas may come out of solution, forming bubbles. Also, in the microgravity environment of the ISS, bubbles can remain suspended in the water, interfering with the systems sensors and pumps. Some processes in the water recovery system can produce gases as byproducts, such as electrolysis used in the Oxygen Generation System of the ISS. Finally, some microbial metabolic processes generate gases which can form bubbles in the water. According to four reasons given above, the passage will first introduce the current situation about dealing with bubbles in ISS, then providing some future directions of the development of the bubble-remove techniques.

Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

Recent strategies developed to examine the nucleation of crystal structures like tetrahydrofuran (THF) hydrates without the effects of a solid interface have included acoustic levitation, where only a liquid-gas interface initially exists. However, the ability now exists to levitate and freeze multiple droplets simultaneously, which could reveal interdroplet effects and provide further insight into interfacial nucleation phenomena. In this study, using direct digital and infrared imaging techniques, the freezing of up to three simultaneous THF hydrate droplets was investigated for the first time. Nucleation was initiated at the aqueous solution-air interface. Two pseudo-heterogeneous mechanisms created additional nucleation interfaces: one from cavitation effects entraining microbubbles and another from subvisible ice particles, also called hydrate-nucleating particles (HNPs), impacting the droplet surface. For systems containing droplets in both the second and third positions, nucleation was statistically simultaneous between all droplets. This effect may have been caused by the high liquid-solid interfacial pressures that developed at nucleation, causing some cracking in the initial hydrate shell around the droplet and releasing additional HNPs (now of hydrate) into the air. During crystallization, the THF hydrate droplets developed a completely white opacity, termed optical clarity loss (OCL). It was suggested that high hydrate growth rates within the droplet resulted in the capture of tiny air bubbles within the solid phase. In turn, light refraction through many smaller bubbles resulted in the OCL. These bubbles created structural inhomogeneities, which may explain how the volumetric expansion of the droplets upon complete solidification was 23.6% compared with 7.4% in pure, stationary THF hydrate systems. Finally, the thermal gradient that developed between the top and bottom of the droplet during melting resulted in a surface tension gradient along the air-liquid interface. In turn, convective cells developed within the droplet, causing it to spin rapidly about the horizontal axis.

Evaluation of the force balance at gas/liquid interface of a tiny bubble under pressure-oscillating field

Under pressure-oscillating field, a tiny air bubble which expands/contracts alternately shows various kinds of shape in viscoelastic fluid depending on the degree of pressure-oscillation. In this study, we evaluated effects of viscoelasticity and local flow on the tiny bubble shape under large pressure-oscillating field in the viscoelastic fluid such as CMC liquids. In the case of forming a unique shape, it is found that the elastic dominates at gas/liquid interface of a tiny bubble.

Effect of Detergent on Concrete prepared with Periwinkle shell as Coarse Aggregate

The use of the periwinkle shell in the production of lightweight concrete has been studied and accepted to be used for concrete works. Hard water containing detergent-like chemicals has been observed to be used in mixing locally produced concrete. This exploratory study is on the effect of water mixed with detergent in a concrete prepared with the periwinkle shell as a coarse aggregate. A total of 27 concrete cubes of size 150mmx150mmx150mm were prepared in the laboratory with a mix ratio of 1:2:4. A water-cement ratio of 0.4 was used with the addition of detergent at varying percentages (0%, 0.3% and 0.6). The cubes were cured in water and tested at 7days, 14days and 28days respectively. Laboratory tests, which includes bulk density, specific gravity, grain size analysis, slump and the compressive strength test was carried out on the aggregates and concrete. The periwinkle shell had a bulk density of 1440kg/m3and a specific gravity of 2.50. The workability tested revealed that the slump values increased with increase in the percentages of detergent. The compressive strength at 28days and at 0.3% and 0.6% were 12.58N/mm2 and 14.06N/mm2 respectively. It was observed that the compressive strength decreased with the addition of detergent because of the tiny air bubbles introduced into the concrete by the detergent. From the results of the study, it can safely be concluded that the use of detergent contaminated water in concrete production will reduce its compressive strength and increase its workability.

Transition of bubble motion from spiralling to zigzagging: A wake-controlled mechanism with a transverse magnetic field

We investigate the dynamics of a millimetre-sized air bubble rising in a liquid due to buoyancy under the influence of a magnetic field applied in a direction transverse to the bubble motion by conducting three-dimensional numerical simulations. The path and trajectory of the air bubble are examined by varying the strength of the transverse magnetic field. In the absence of a magnetic field, it is well known that under certain conditions a tiny air bubble undergoes spiralling motion due to its shape deformation and vortex shedding in the wake region. It is shown here that the spiralling motion of an air bubble observed without magnetic field transforms into a purely zigzagging motion under an applied transverse magnetic field. To understand the mechanism, we analyse the evolution of the wake vortices and forces experienced by the bubble in the presence of a transverse magnetic field. It is found that the twisted double-threaded vortices observed in a spiralling bubble in the absence of a magnetic field appear to rotate perpendicularly to the applied magnetic field across the vertical axis, thereby making the bubble shift its trajectory from spiralling to zigzagging. By calculating the lift and drag forces acting on the bubble, it is shown that how these forces acting on the bubble contribute to the vortex shedding patterns. Thus, the present study demonstrates the mechanism to control the trajectory of an air bubble under the application of a magnetic field.

Use of spectral domain optical coherence tomography to detect internal defects of resin composites in carious teeth after restorations

Postoperative testing plays an important role in evaluating clinical effect of treatment of caries by filling the decayed teeth with resin composites, which mainly depends on the detection of defects at the interface between resin composites and cavity to date, without considering the internal defects of resin composites. Here, we report, for the first time, the measurement of the morphologies within resin composites by using spectral domain optical coherence tomography. Experiments were performed on the ex vivo human carious teeth after restorations, and the results showed that the tiny cracks and air bubbles within resin composites can be clearly distinguished. With features of noninvasive imaging, high resolution and real-time processing, this system may have great potential to be applied for caries as a useful clinical evaluation tool, and with that, we should pay more attention to the internal defects of resin composites in the future in order to better assess and manage the treatment.

Did biology begin with tiny bubbles?

illions of years ago, a mix of organic molecules formed and started the chemical reactions that became life. In a new study, researchers in Germany propose that tiny air bubbles in water sloshing through volcanic rocks could have helped concentrate those molecules to start the process (Nat. Chem. 2019, DOI: 10.1038/s41557-019-0299-5). Over 10 years ago, Dieter Braun’s group at Ludwig Maximilian University Munich showed that polymers like DNA can move along a temperature gradient in a process called thermophoresis. As they studied the phenomenon further, the researchers wondered whether thermophoresis could help move prebiotic molecules around in the tiny channels in volcanic rocks, one of the places where scientists think life on Earth may have started. The researchers have found that bubbles in liquid-filled microchannels, like those in volcanic rock, provide an air-water interface where biomolecules can accumulate. Braun compares it to a coffee ring, with particles congregating at the

Application of low-intensity ultrasound as a rapid, cost-effective tool to wheat screening: Discrimination of Canadian varieties at 10 MHz

Our previous study on the use of low-intensity ultrasound for wheat variety discrimination showed the potential of ultrasound waves at 10 MHz for wheat screening and dough rheology evaluation. To further examine the reliability of the technique for wheat variety differentiation at 10 MHz, 23 hard red spring (HRS) wheat varieties with comparable bread making quality were studied. Wheat quality characteristics determined with farinograph, extensograph and baking test were used for comparison purposes. Highly significant effect (P ≤ 0.001) of variety on ultrasonic parameters as well as principal component analysis results confirmed the capability of the technique at 10 MHz for wheat variety discrimination. Ultrasonic parameters were also demonstrated to be significantly correlated (P ≤ 0.05) with wheat protein content, falling number and grain ash content. Subgrouping wheat varieties based on their grain and flour characteristics promoted significant correlations between ultrasound and dough strength parameters. High sensitivity of ultrasound signals to protein, starch and microscopic inhomogeneities, e.g., tiny air bubbles and particles, enabled discrimination of Canadian varieties used in this study. Accordingly, further modification of the current protocol is believed to broaden the application of our low-intensity ultrasound technique at 10 MHz to wheat screening and quality evaluation from various angles.

Local flow around a tiny bubble under a pressure-oscillation field in a viscoelastic worm-like micellar solution

The motion of a tiny air bubble in an aqueous solution of cetyl trimethyl ammonium bromide and sodium salicylate (CTAB/NaSal), which forms wormlike micelles, was observed using a high-speed polarization camera. Complex local flow is observed around the bubble surface because the bubble shape deforms repeatedly at 100 Hz. The camera can be used to measure the retardation distribution, which is related to the stress field around the bubble. Different retardation and orientation angle distributions were observed during the contraction and expansion phases. In the contraction phase, a strong retardation distribution appears at the tail of the cusped bubble. The occurrence of uniaxial elongation deformation is considered to be due to the negative wake because they are closely correlated. In contrast, a weak retardation distribution spreads at the upper side of the bubble during the expansion phase, where biaxial extensional deformation occurs due to expansion of the bubble surface. These significant changes in strong elastic stress distributions, which correspond to the orientation angle profiles, can result in increase of bubble rising velocities.

Value Added Product of Lightweight Cement from Industrial By-Products Using Geopolymer Technique

In construction and building material sector, Lightweight Cement (LWC) has been receiving much more attention due to some of its advantages compared to other lightweight materials e.g. wood, foam and plastic. The method of incorporating tiny air bubbles into cementitious matrix for lightweight cement production is widely used as it could achieve good engineering properties with efficient production process. Conventional methods, Autoclaved Aerated Cement (AAC) and Portland cement-Cellular Lightweight Cement (CLC), use Portland cement as a main material which could lead to a huge disturbance to natural sources as well as release massive amount of carbon dioxide (CO2) to the atmosphere during its calcination. To achieve green construction material scheme, an attempt to utilize industrial wastes (by-products) as raw starting materials have been developing. One among those value-added approaches is OPC-less alkaline-activated cement from by-products, called Geopolymer technique. The main aim of this paper is to develop lightweight cement by using geopolymer technique with (CLC) method, called GP-CLC system, in order to optimize both economical aspects and engineering properties. The preliminary results show that the compressive strength of GP-CLC cannot reach that level of AAC system, but the strength was higher than the conventional OPC-CLC. The main challenge is that unit CO2 emission can be significantly reduce by using GP-CLC system as OPC consumption is replaced by by-product, fly ash.

Designation of Soap Molder Machine and Procedure for Transparent Soap

Transparent soap is actually the combination of actual soap and solvent. The solvent is added into the soap solution to produce the transparent characteristic. The problem from the previous production is that tiny air bubbles were observed inside the soap resulted in less attractive appearance. Current method of producing the soap bar had taken more than 8 hours and having difficulties to take out the soap bar from the plastic mold with low production rate. It is expected that the air bubble problem can be solved using this new soup molder machine. The soap production rate is believed to increase with the invention of soap molder machine. By reducing the production time from 8 hours to 2 hours, it improve production rate significantly.

A Milestone: Approval of CEUS for Diagnostic Liver Imaging in Adults and Children in the USA.

A Milestone: Approval of CEUS for Diagnostic Liver Imaging in Adults and Children in the USA.

Initial surface deformations during impact on a liquid pool

A tiny air bubble can be entrapped at the bottom of a solid sphere that impacts onto a liquid pool. The bubble forms due to the deformation of the liquid surface by a local pressure buildup inside the surrounding gas, as also observed during the impact of a liquid drop on a solid wall. Here, we perform a perturbation analysis to quantitatively predict the initial deformations of the free surface of a liquid pool as it is approached by a solid sphere. We study the natural limits where the gas can be treated as a viscous fluid (Stokes flow) or as an inviscid fluid (potential flow). For both cases we derive the spatiotemporal evolution of the pool surface, and recover some of the recently proposed scaling laws for bubble entrapment. On inserting typical experimental values for the impact parameters, we find that the bubble volume is mainly determined by the effect of gas viscosity.

Common Blind Spots on Chest CT: Where Are They All Hiding? Part 1—Airways, Lungs, and Pleura

W533 tracheal or endobronchial lesions. Malignant lesions may present as endoluminal nodules, subtle wall thickening (Fig. 1), or irregular contour of the lumen. Tracheal tumors such as adenoid cystic carcinoma and squamous cell carcinoma can have submucosal spread, which can be difficult to detect or be underestimated on CT. The accurate detection and description of the extent of the tumor is, however, essential for surgical planning. Endobronchial metastases can be seen most frequently in patients with primary renal cell, breast, and colorectal cancers and melanoma. The most common primary bronchial tumors include squamous cell carcinoma and carcinoid tumors. Benign entities such as broncholith, endobronchial hamartoma, and aspirated foreign bodies can also cause significant complications such as recurrent atelectasis or pneumonia. Intraluminal secretion or mucus plug can mimic central airway lesions. However, secretion usually appears smoothly marginated and focal, often along the dependent aspect of the airways. Tiny air bubbles can sometimes be visualized within secretion. Comparison with prior imaging is helpful because a persistent intraluminal opacity is more suggestive of a true lesion. Repeat imaging in prone position or after coughing can also help in differentiating secretions from endoluminal lesions.

A new fabrication process for uniform SU-8 thick photoresist structures by simultaneously removing edge bead and air bubbles

This paper proposes a new SU-8 fabrication process to simultaneously remove edge bead and tiny air bubbles by spraying out edge bead removal (EBR) fluid over the entire surface of photoresist. In particular, the edge bead and air bubbles can cause an air gap between a film mask and a photoresist surface during UV exposure. The diffraction effect of UV light by the air gap leads to inaccurate and non-uniform SU-8 patterns. In this study, we demonstrate a simple method using EBR treatment to simultaneously eliminate the edge bead at the edge of wafer and tiny air bubbles inside SU-8. The profiles of thickness variation of SU-8 films with/without the EBR treatment are measured. The results show that the proposed EBR treatment can successfully remove the edge bead and air bubbles over the entire SU-8 films. The average pattern uniformity of SU-8 is improved from 50.5% to 11.3% in the case of 200 µm thickness. This method is simple and inexpensive, compared to a standard EBR process, because it does not require specialized equipment and it can be applied regardless of substrate geometry (e.g. circular wafer and rectangular slide glass).

Wetting Technologies for High-Accuracy Sink-Float Separations in Water- Based Media

The accuracy of sink-float separations in water-based media such as Magnetic Density Separation is compromised by tiny air-bubbles attached to the surface of hydrophobic materials in the feed. Separations of plastics mixtures with accuracy better than 10 kg/m 3 require a total elimination of air-bubbles by pre-wetting the surface of the feed particles with a thin film of water. Theoretical and experimental results are compared for pre-wetting processes based on condensation from the gas phase and direct liquid-solid contact for both shredded waste and virgin polymers. The tests show that the wettability of most polymers improve slightly by steaming for about 1 minute, but the best wetting results are obtained with immersion in boiling tap water. The success of wetting in boiling water can be explained by the deposition of a thin layer of calcium carbonate. Shredded plastics are easier to be wetted than virgin polymers, probably because a relatively rougher surface is caused by the shredder process. A new wetting process to eliminate air bubbles was developed on the basis of these results, which carries a minimal amount of heat and water with the feed to the MDS process liquid.

Spectrum of CT Findings after Radiofrequency Ablation of Hepatic Tumors

Image-guided radiofrequency (RF) ablation has been used to treat both resectable and nonresectable hepatic tumors. A precise imaging assessment of the therapeutic response and of any complications is mandatory after ablation. Contrast material-enhanced ultrasonography, computed tomography (CT), and magnetic resonance imaging all may be useful for this assessment. At most institutions, a three-phase contrast-enhanced CT examination is performed immediately or within 1 month after RF ablation to assess the technical success of treatment. If ablation was technically successful, three-phase CT may be repeated at 3-month intervals for evaluation of tumor recurrence. The typical CT finding in the zone subjected to RF ablation is an area of low attenuation that encompasses the tumor and an ablative margin. However, the appearance of the ablative zone may vary greatly, depending on the success of treatment and the time elapsed after the procedure. Ringlike enhancement representing benign reactive hyperemia around the ablation zone, central high-attenuation areas representing greater cellular disruption, and tiny air bubbles frequently are seen at immediate follow-up CT but usually have disappeared by the first or second follow-up examination. The successfully ablated zone gradually involutes. The appearance of the zone differs when residual tumor tissue or local tumor progression is present. Immediate or delayed complications also may be seen at follow-up CT. Radiologists must be familiar with both typical and atypical CT findings and their clinical significance. (c) RSNA, 2008.

Optical Coherence Tomography of Descemet Membrane Separation by the Big Bubble Technique

To image Descemet membrane separation by the big bubble technique in human corneas by using anterior segment optical coherence tomography (OCT). Five human corneoscleral rims were placed on an artificial anterior chamber and partially trephinated. A 23-gauge needle was inserted into the stroma under slit-lamp control and air was injected. The procedure was continuously imaged by anterior segment OCT. In all corneoscleral rims, a big bubble was created. The spread of air seemed to follow the interlamellar spaces without crossing lamellae. It involved mainly the inner layers of the stroma while sparing the outer 212 +/- 41 microm of the cornea (range, 168-271 microm). Intrastromal pressure build-up forced air above the Descemet membrane, creating tiny air bubbles of approximately 355 +/- 111 microm (range, 210-560 microm). When the pressure inside those bubbles reached a certain level, the bubbles spontaneously coalesced to form a big bubble. OCT is useful in imaging intracorneal air spread. The main obstacle to creating a big bubble is the impermeability to air of the imperforated posterior stromal lamellae.

The Mechanism of Drag Reduction around Bodies of Revolution Using Bionic Non-Smooth Surfaces

Bionic non-smooth surfaces (BNSS) can reduce drag. Much attention has been paid to the mechanism of shear stress reduction by riblets. The mechanism of pressure force reduction by bionic non-smooth surfaces on bodies of revolution has not been well investigated. In this work CFD simulation has revealed the mechanism of drag reduction by BNSS, which may work in three ways. First, BNSS on bodies of revolution may lower the surface velocity of the medium, which prevents the sudden speed up of air on the cross section. So the bottom pressure of the model would not be disturbed sharply, resulting in less energy loss and drag reduction. Second, the magnitude of vorticity induced by the bionic model becomes smaller because, due to the sculpturing, the growth of tiny air bubbles is avoided. Thus the large moment of inertia induced by large air bubble is reduced. The reduction of the vorticity could reduce the dissipation of the eddy. So the pressure force could also be reduced. Third, the thickness of the momentum layer on the model becomes less which, according to the relationship between the drag coefficient and the momentum thickness, reduces drag.

Enhancement of Sonochemical Reaction Rate by Addition of Micrometer-Sized Air Bubbles

The sonochemical reaction rate has been enhanced by the introduction of tiny air bubbles. The bubbles including micrometer-sized ones are produced by method of atomization and are introduced into aqueous luminol solution under 141-kHz sonication in order to investigate the enhancement of sonochemical reaction rate by introduction of tiny bubbles through the intensity measurement of sonochemiluminescence (SCL). It is shown that the introduction of tiny bubbles under sonication accomplishes the large SCL intensity compared to the cases of sonication only and liquid flow under sonication. It is also shown that it is important to adjust the configuration of tiny-bubble addition to the sound field. Through the investigations on the intensity and the spatial pattern of luminol-SCL, it has been clarified that tiny bubbles added into the sonicated liquid not only cause the liquid flow but also increase the number of collapsing bubbles active for sonochemical reaction. It is also shown that the tiny-bubble addition enhances the reaction rate of KI oxidation under sonication. Therefore, the present method of introduction of tiny bubbles is effective for enhancement of sonochemical reaction rate.