Journal articles on the topic 'H-bubbles'
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1
Occhionero, Franco, Luca Amendola, and Pier Stefano Corasaniti. "Primordial Bubbles within Primordial Bubbles." Symposium - International Astronomical Union 201 (2005): 497–98. http://dx.doi.org/10.1017/s0074180900216847.
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Two consecutive, distinct episodes of phase transition occurring during inflation may nucleate two generations of bubbles, one inside the other. We design a model of inflation that realizes this sequence and yields bubble spectra that are bimodal and tunable functions of phenomelogical parameters in turn combinations of microphysical parameters. We argue in favor of a tuning of the parameters such that the outer and earlier generation of bubbles becomes hundreds of Mpc/h in diameter (like the local Hubble bubbles of the literature) whereas the inner and later generation becomes tens of Mpc/h in diameter (like the observed large scale voids).
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Li, G., B. Ning, L. Liu, W. Wan, and J. Y. Liu. "Effect of magnetic activity on plasma bubbles over equatorial and low-latitude regions in East Asia." Annales Geophysicae 27, no. 1 (January 19, 2009): 303–12. http://dx.doi.org/10.5194/angeo-27-303-2009.
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Abstract. The dependence of plasma bubble occurrence in the eveningside ionosphere, with magnetic activity during the period years 2001–2004, is studied here based on the TEC observations gathered by ground-based GPS receivers which are located in the equatorial and low-latitude regions in East Asia. The observed plasma bubbles consist of the plasma-bubble events in the equatorial (stations GUAM, PIMO and KAYT), and low-latitude regions (stations WUHN, DAEJ and SHAO). It is shown that most equatorial plasma-bubble events commence at 20:00 LT, and may last for >60 min. The magnetic activity appears to suppress the generation of equatorial plasma bubbles with a time delay of more than 3 h (4–9 h). While in the low-latitude regions, most plasma-bubble events commence at about 23:00 LT and last for <45 min. The best correlation between Kp and low-latitude plasma-bubble occurrence is found with an 8–9 h delay, a weak correlation exists for time delays of 6–7 h. This probably indicates that over 3 h delayed disturbance dynamo electric fields obviously inhibit the development of plasma bubbles in the pre-midnight sector.
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Randsoe, Thomas, and Ole Hyldegaard. "Effect of oxygen breathing on micro oxygen bubbles in nitrogen-depleted rat adipose tissue at sea level and 25 kPa altitude exposures." Journal of Applied Physiology 113, no. 3 (August 1, 2012): 426–33. http://dx.doi.org/10.1152/japplphysiol.00193.2012.
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The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing and the tissue nitrogen pressure. To quantify the contribution of oxygen to bubble growth at altitude, micro oxygen bubbles (containing 0% nitrogen) were injected into the adipose tissue of rats depleted from nitrogen by means of preoxygenation (fraction of inspired oxygen = 1.0; 100%) and the bubbles studied at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen prebreathing at 101.3 kPa (sea level). Micro oxygen bubbles of 500-800 nl were then injected into the exposed abdominal adipose tissue. The oxygen bubbles were studied for up to 3.5 h during continued oxygen breathing at either 101.3 or 25 kPa ambient pressures. At 101.3 kPa, all bubbles shrank consistently until they disappeared from view at a net disappearance rate (0.02 mm2 × min−1) significantly faster than for similar bubbles at 25 kPa altitude (0.01 mm2 × min−1). At 25 kPa, most bubbles initially grew for 2–40 min, after which they shrank and disappeared. Four bubbles did not disappear while at 25 kPa. The results support bubble kinetic models based on Fick's first law of diffusion, Boyles law, and the oxygen window effect, predicting that oxygen contributes more to bubble volume and growth during hypobaric conditions. As the effect of oxygen increases, the lower the ambient pressure. The results indicate that recompression is instrumental in the treatment of aDCS.
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Palmeirim, P., A. Zavagno, D. Elia, T. J. T. Moore, A. Whitworth, P. Tremblin, A. Traficante, et al. "Spatial distribution of star formation related to ionized regions throughout the inner Galactic plane." Astronomy & Astrophysics 605 (September 2017): A35. http://dx.doi.org/10.1051/0004-6361/201629963.
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We present a comprehensive statistical analysis of star-forming objects located in the vicinities of 1360 bubble structures throughout the Galactic plane and their local environments. The compilation of ~70 000 star-forming sources, found in the proximity of the ionized (Hii) regions and detected in both Hi-GAL and GLIMPSE surveys, provided a broad overview of the different evolutionary stages of star-formation in bubbles, from prestellar objects to more evolved young stellar objects (YSOs). Surface density maps of star-forming objects clearly reveal an evolutionary trend where more evolved star-forming objects (Class II YSO candidates) are found spatially located near the center, while younger star-forming objects are found at the edge of the bubbles. We derived dynamic ages for a subsample of 182 H ii regions for which kinematic distances and radio continuum flux measurements were available. We detect approximately 80% more star-forming sources per unit area in the direction of bubbles than in the surrounding fields. We estimate the clump formation efficiency (CFE) of Hi-GAL clumps in the direction of the shell of the bubbles to be ~15%, around twice the value of the CFE in fields that are not affected by feedback effects. We find that the higher values of CFE are mostly due to the higher CFE of protostellar clumps, in particular in younger bubbles, whose density of the bubble shells is higher. We argue that the formation rate from prestellar to protostellar phase is probably higher during the early stages of the (H ii ) bubble expansion. Furthermore, we also find a higher fraction of massive YSOs (MYSOs) in bubbles at the early stages of expansion (<2 Myr) than older bubbles. Evaluation of the fragmentation time inside the shell of bubbles advocates the preexistence of clumps in the medium before the bubble expansion in order to explain the formation of MYSOs in the youngest H ii regions (<1 Myr), as supported by numerical simulations. Approximately 23% of the Hi-GAL clumps are found located in the direction of a bubble, with 15% for prestellar clumps and 41% for protostellar clumps. We argue that the high fraction of protostellar clumps may be due to the acceleration of the star-formation process cause by the feedback of the (Hii) bubbles.
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Hou, L. G., and X. Y. Gao. "Radio recombination line observations towards Spitzer infrared bubbles with the TianMa radio telescope." Monthly Notices of the Royal Astronomical Society 489, no. 4 (September 5, 2019): 4862–74. http://dx.doi.org/10.1093/mnras/stz2466.
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ABSTRACT Many of the Spitzer infrared bubbles identified by the Milky Way Project (MWP) are suggested to be $\rm{H \small {II}} $ regions in nature. More than 70 per cent of the ∼5000 known bubbles do not have radio recombination line (RRL) observations, hence have not been confirmed as $\rm{H \small {II}} $ regions. A systematic RRL survey should be helpful to identify the nature of the bubbles. With the Shanghai TianMa 65-m radio telescope, we searched for RRLs towards 216 selected Spitzer bubbles by simultaneously observing 19 RRLs in the C band (4–8 GHz). RRLs are detected in the directions of 75 of the 216 targets. 31 of the 75 RRL sources are classified as new detections, which are possibly from new $\rm{H \small {II}} $ regions or diffuse warm ionized medium; 36 of them are probably from the outskirts of nearby bright $\rm{H \small {II}} $ regions, rather than bubble-encircled ionized gas; and the detected RRLs towards 8 bubbles are identified from known $\rm{H \small {II}} $ regions. For 58 of the 75 RRL sources, we obtained their distances after resolving the kinematic distance ambiguity by combining the results of the H2CO absorption method, the $\rm{H \small {I}} $ emission/absorption method, and the $\rm{H \small {I}} $ self-absorption method. The low detection rate of new $\rm{H \small {II}} $ regions implies that a number of MWP bubbles in the DR1 catalogue are too faint if they are $\rm{H \small {II}} $ regions.
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Song, Yan Yan, Guo Qi Liu, Hong Xia Li, and Wen Gang Yang. "Influence of Ladle Purging Plug Airway on Flow Properties of Liquid Steel." Advanced Materials Research 472-475 (February 2012): 2581–87. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.2581.
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The influence of the different airway structure on mixing time of molten steel are studied through using water model experiments. The bubble volume and velocity have been investigated through the PIV for different airway structure in the flow of 1m3/h. Results showed that with the slit distribution same, the smaller the slit width, the greater the volume percentage of the large bubbles and the average velocity of the bubbles in rising, but the shorter the mixing time. Reduce the number of the slit can lead to the volume percentage of the large bubbles and the average velocity of the bubbles in rising decreases, the mixing time extended, and it is more obvious to the mixing time to reduce the number of the inner slit. Inflatable volume<1.1m3/h, with the slit in the outer ring only and the number of slit same, the volume percentage and the average velocity of the large bubbles in rising is larger, the mixing time is reduced. Inflatable volume≥1.1m3/h, the slit evenly distribution is better for mixing.
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Randsøe, T., T. M. Kvist, and O. Hyldegaard. "Effect of oxygen and heliox breathing on air bubbles in adipose tissue during 25-kPa altitude exposures." Journal of Applied Physiology 105, no. 5 (November 2008): 1492–97. http://dx.doi.org/10.1152/japplphysiol.90840.2008.
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At altitude, bubbles are known to form and grow in blood and tissues causing altitude decompression sickness. Previous reports indicate that treatment of decompression sickness by means of oxygen breathing at altitude may cause unwanted bubble growth. In this report we visually followed the in vivo changes of micro air bubbles injected into adipose tissue of anesthetized rats at 101.3 kPa (sea level) after which they were decompressed from 101.3 kPa to and held at 25 kPa (10,350 m), during breathing of oxygen or a heliox(34:66) mixture (34% helium and 66% oxygen). Furthermore, bubbles were studied during oxygen breathing preceded by a 3-h period of preoxygenation to eliminate tissue nitrogen before decompression. During oxygen breathing, bubbles grew from 11 to 198 min (mean: 121 min, ±SD 53.4) after which they remained stable or began to shrink slowly. During heliox breathing bubbles grew from 30 to 130 min (mean: 67 min, ±SD 31.0) from which point they stabilized or shrank slowly. No bubbles disappeared during either oxygen or heliox breathing. Preoxygenation followed by continuous oxygen breathing at altitude caused most bubbles to grow from 19 to 179 min (mean: 51 min, ±SD 47.7) after which they started shrinking or remained stable throughout the observation period. Bubble growth time was significantly longer during oxygen breathing compared with heliox breathing and preoxygenated animals. Significantly more bubbles disappeared in preoxygenated animals compared with oxygen and heliox breathing. Preoxygenation enhanced bubble disappearance compared with oxygen and heliox breathing but did not prevent bubble growth. The results indicate that oxygen breathing at 25 kPa promotes air bubble growth in adipose tissue regardless of the tissue nitrogen pressure.
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Wang, Ziyue, Liansheng Liu, Runze Duan, and Liang Tian. "The aerobreakup of bubbles in continuous airflow." Physics of Fluids 34, no. 4 (April 2022): 043317. http://dx.doi.org/10.1063/5.0086604.
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Floating soap bubbles usually break up owing to gravitational drainage, surface evaporation, environmental disturbances, and collisions with objects. If a gust of wind blows into a bubble, does the bubble break, and, if so, how does it do so? This study reports experiments that use a high-speed camera to examine the dynamic behaviors of a suspended bubble that is suddenly exposed to continuous airflow. Specifically, the behaviors and mechanisms of the aerobreakup of bubbles are explored. The suspended bubble undergoes shedding and deformation under aerodynamic force and flows with airflow. As the Weber number ( We) increases, the parameter of Taylor deformation ( DT) first increases and then decreases. At a higher Reynolds number, K–H waves appear on the surface of the film owing to the strong shear of airflow on the liquid film. Most such bubbles break due to the shear of the wake vortices on the leeward surface or surface waves on the windward surface, both of which are shearing. The aerobreakup of the bubbles becomes more severe with an increase in We, and they successively exhibit modes of wind-flowing, leeward breakup, windward breakup, and multihole breakup.
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CALDIROLI, PAOLO, and ROBERTA MUSINA. "EXISTENCE OF MINIMAL H-BUBBLES." Communications in Contemporary Mathematics 04, no. 02 (May 2002): 177–209. http://dx.doi.org/10.1142/s021919970200066x.
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Given a function H ∈ C1 (ℝ3) asymptotic to a constant at infinity, we investigate the existence of H-bubbles, i.e., nontrivial, conformal surfaces parametrized by the sphere, with mean curvature H. Under some global hypotheses we prove the existence of H-bubbles with minimal energy.
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Ohiomoba, Emmanuel, Ayokunle Omosebi, Gao Xin, and Kunlei Liu. "(Invited) Elucidating the Hydrodynamic Behavior of Multi-Species Gas Bubbles in an Electrochemical Solvent Regenerator for Direct Air Capture." ECS Meeting Abstracts MA2022-02, no. 27 (October 9, 2022): 1036. http://dx.doi.org/10.1149/ma2022-02271036mtgabs.
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Direct Air Capture (DAC) is very significant to bolstering the global drive towards net negative emissions. DAC technologies/plants have emerged in recent years, with the regeneration of the capture solvent used in the process being the major bottleneck of most aqueous technologies. [1] Leveraging electrochemical principles has offered a potential opportunity to simplify the entire solvent regeneration process and potentially reduce its overall capture cost, compared to traditional approaches. The electrochemical approach also offers the benefit of direct integrating clean energy, and also eliminating the high thermal energy requirements of typical methods.[2] Despite these potentials, the complex three-phase (solid-liquid-gas) interaction on the electrode surface pose a significant impediment to this electrochemical approach for DAC. The evolution of gas bubbles in electrochemical cells are well-known to contribute to energy losses in such reactors, from previous studies. [3],[4],[5] Gas bubbles have been shown to influence ohmic overpotentials in electrochemical reactors and studies have shown that the energy demand for water electrolysis can be reduced by 10-25 percent if the formation of gas bubbles is suppressed. [6],[7] However, the evolution of gas bubbles in electrochemical systems remains a complicated issue requiring further investigation. This study advances previous work by investigating the simultaneous evolution of CO2 gas bubbles along with O2/H2 gas bubbles in an electrochemical reactor for DAC. Gas bubbles are infamous for their ability to cover the active area of electrodes, limiting the transport of reactive species to the electrode surface, thus, increasing cell resistance. In this work, we explore changes in the polarization and hydrodynamics behavior of gas bubbles in the electrolyzer used for DAC solvent regeneration owing to the evolution of CO2 bubbles from pH swing, and the implications of the additional CO2 bubble formation to electrode surface coverage. By using a high-speed camera, we observe that bubbles coverage appears to be larger at the edges of the electrodes, and that the orientation of the electrodes influence bubble coalescence and detachment rate. We also employ different cell designs to mitigate the impact of bubble surface coverage towards reducing cell resistance. References Sabatino, A. Grimm, F. Gallucci, M. Van Sint Annaland, G. J. Kramer, M. Gazzani, Joule, 5(8), 2047-2076 (2021). Gao, A. Omosebi, R. Perrone, K. Liu, Journal of The Electrochemical Society (2022). H. Li, Y. J. Chen, Scientific Reports, 11(1), 1-12 (2021). F. Swiegers, R. N. L.Terrett, G. Tsekouras, T. Tsuzuki, R. J. Pace, R. Stranger, Sustainable Energy & Fuels, 5(11), 3004–3004 (2021). Zhao, H. Ren, L. Luo, Langmuir, 35(16), 5392-5408 (2019). Mazloomi, N. B. Sulaiman, H. Moayedi, International Journal of Electrochemical Science, 7(4), 3314-3326 (2012). C. Wang, C. Y. Chen, Electrochimica Acta, 54(15), 3877-3883 (2009).
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Di, Pengfei, Dong Feng, Jun Tao, and Duofu Chen. "Using Time-Series Videos to Quantify Methane Bubbles Flux from Natural Cold Seeps in the South China Sea." Minerals 10, no. 3 (February 27, 2020): 216. http://dx.doi.org/10.3390/min10030216.
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Natural cold seeps are an important source of methane and other greenhouse gases to the ocean and atmosphere in the marine environment. Accurate quantification of methane bubble fluxes from cold seeps is vital for evaluating their influence on the global methane budget and climate change. We quantified the flux of gas bubbles released from two natural cold seep sites in the South China Sea: one seep vent in the Haima cold seeps (1400 m depth) and three seep vents at Site F (1200 m depth). We determined bubble diameter, size distribution, and bubble release rate using image processing techniques and a semiautomatic bubble-counting algorithm. The bubble size distributions fit well to log-normal distribution, with median bubble diameters between 2.54 mm and 6.17 mm. The average bubble diameters and release rates (4.8–26.1 bubbles s−1) in Site F was lower than that in Haima cold seeps (22.6 bubbles s−1), which may be attributed to a variety of factors such as the nature of the gas reservoir, hydrostatic pressure, migration pathways in the sediments, and pore size. The methane fluxes emitted at Haima cold seeps (12.6 L h−1) and at Site F (4.9 L h−1) indicate that the Haima and Site F cold seeps in the South China Sea may be a source of methane to the ocean. However, temporal variations in the bubble release rate and the geochemical characteristics of the seeps were not constrained in this study due to the short observational time interval.
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Ostadrahimi, Mahdi, Khodakaram Gharibi, Ali Dehghani, and Saeed Farrokhpay. "Estimating Bubble Loading in Industrial Flotation Cells." Minerals 9, no. 4 (April 8, 2019): 222. http://dx.doi.org/10.3390/min9040222.
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Bubble loading is the ratio of the weight of the solid particles to the bubble’s surface, and it has an effective role in the flotation efficiency. This paper investigates bubble loading an industrial processing circuit through considering the important role of the bubble diameter in calculating bubble loading, and the effect of the aeration rate and frother dosage on the bubble diameter. The ratio of the weight of solid particles to the bubble volume was estimated to be in the range of 8 to 24 g/L. Although increasing the aeration could result in increasing the weight of the particles attached to the bubbles, the bubble loading was reduced by increasing the aeration rate due to its impact on the bubble diameter and the percentage of bubble surface coverage. For example, when the aeration rate was increased from 45 to 146 m3/h, the bubble loading decreased from 23 to 12 g/L. By increasing the frother dosage from 70 to 150 mL/min, the bubble loading increased from 16 to 19 g/L.
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Gvozdić, Biljana, Elise Alméras, Varghese Mathai, Xiaojue Zhu, Dennis P. M. van Gils, Roberto Verzicco, Sander G. Huisman, Chao Sun, and Detlef Lohse. "Experimental investigation of heat transport in homogeneous bubbly flow." Journal of Fluid Mechanics 845 (April 20, 2018): 226–44. http://dx.doi.org/10.1017/jfm.2018.213.
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We present results on the global and local characterisation of heat transport in homogeneous bubbly flow. Experimental measurements were performed with and without the injection of ${\sim}2.5~\text{mm}$ diameter bubbles (corresponding to bubble Reynolds number $Re_{b}\approx 600$) in a rectangular water column heated from one side and cooled from the other. The gas volume fraction $\unicode[STIX]{x1D6FC}$ was varied in the range 0 %–5 %, and the Rayleigh number $Ra_{H}$ in the range $4.0\times 10^{9}{-}1.2\times 10^{11}$. We find that the global heat transfer is enhanced up to 20 times due to bubble injection. Interestingly, for bubbly flow, for our lowest concentration $\unicode[STIX]{x1D6FC}=0.5\,\%$ onwards, the Nusselt number $\overline{Nu}$ is nearly independent of $Ra_{H}$, and depends solely on the gas volume fraction $\unicode[STIX]{x1D6FC}$. We observe the scaling $\overline{Nu}\,\propto \,\unicode[STIX]{x1D6FC}^{0.45}$, which is suggestive of a diffusive transport mechanism, as found by Alméras et al. (J. Fluid Mech., vol. 776, 2015, pp. 458–474). Through local temperature measurements, we show that the bubbles induce a huge increase in the strength of liquid temperature fluctuations, e.g. by a factor of 200 for $\unicode[STIX]{x1D6FC}=0.9\,\%$. Further, we compare the power spectra of the temperature fluctuations for the single- and two-phase cases. In the single-phase cases, most of the spectral power of the temperature fluctuations is concentrated in the large-scale rolls/motions. However, with the injection of bubbles, we observe intense fluctuations over a wide range of scales, extending up to very high frequencies. Thus, while in the single-phase flow the thermal boundary layers control the heat transport, once the bubbles are injected, the bubble-induced liquid agitation governs the process from a very small bubble concentration onwards. Our findings demonstrate that the mixing induced by high Reynolds number bubbles ($Re_{b}\approx 600$) offers a powerful mechanism for heat transport enhancement in natural convection systems.
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Kerboua, Kaouther, Oualid Hamdaoui, and Abdulaziz Alghyamah. "Numerical Characterization of Acoustic Cavitation Bubbles with Respect to the Bubble Size Distribution at Equilibrium." Processes 9, no. 9 (August 30, 2021): 1546. http://dx.doi.org/10.3390/pr9091546.
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In addition to bubble number density, bubble size distribution is an important population parameter governing the activity of acoustic cavitation bubbles. In the present paper, an iterative numerical method for equilibrium size distribution is proposed and combined to a model for bubble counting, in order to approach the number density within a population of acoustic cavitation bubbles of inhomogeneous sizing, hence the sonochemical activity of the inhomogeneous population based on discretization into homogenous groups. The composition of the inhomogeneous population is analyzed based on cavitation dynamics and shape stability at 300 kHz and 0.761 W/cm2 within the ambient radii interval ranging from 1 to 5 µm. Unstable oscillation is observed starting from a radius of 2.5 µm. Results are presented in terms of number probability, number density, and volume probability within the population of acoustic cavitation bubbles. The most probable group having an equilibrium radius of 3 µm demonstrated a probability in terms of number density of 27%. In terms of contribution to the void, the sub-population of 4 µm plays a major role with a fraction of 24%. Comparisons are also performed with the homogenous population case both in terms of number density of bubbles and sonochemical production of HO•,HO2•, and H• under an oxygen atmosphere.
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Skogland, Steffen, Kåre Segadal, Harald Sundland, and Arvid Hope. "Gas bubbles in rats after heliox saturation and different decompression steps and rates." Journal of Applied Physiology 92, no. 6 (June 1, 2002): 2633–39. http://dx.doi.org/10.1152/japplphysiol.00795.2001.
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Effects of pressure reduction, decompression rate, and repeated exposure on venous gas bubble formation were determined in five groups (GI, GII, GIII, GIV, and GV) of conscious and freely moving rats in a heliox atmosphere. Bubbles were recorded with a Doppler ultrasound probe implanted around the inferior caval vein. Rats were held for 16 h at 0.4 MPa (GI), 0.5 MPa (GII and GIII), 1.7 MPa (GIVa), or 1.9 MPa (GIV and GV), followed by decompression to 0.1 MPa in GI to GIII and to 1.1 MPa in GIV and GV. A greater decompression step, but at the same rate (GII vs. GI and GIVb vs. GIVa), resulted in significantly more bubbles ( P< 0.01). A twofold decompression step resulted in equal amount of bubbles when decompressing to 1.1 MPa compared with 0.1 MPa. The faster decompression in GII and GVa (10.0 kPa/s) resulted in significantly more bubbles ( P < 0.01) compared with GIII and GVb (2.2 kPa/s). No significant difference was observed in cumulative bubble score when comparing first and second exposure. With the present animal model, different decompression regimes may be evaluated.
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Myers, S. M., T. J. Headley, C. R. Hills, J. Han, G. A. Petersen, C. H. Seager, and W. R. Wampler. "The Behavior of Ion-Implanted Hydrogen in Gallium Nitride." MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 532–41. http://dx.doi.org/10.1557/s1092578300003008.
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Hydrogen was ion-implanted into wurtzite-phase GaN, and its transport, bound states, and microstructural effects during annealing up to 980°C were investigated by nuclear-reaction profiling, ion-channeling analysis, transmission electron microscopy, and infrared (IR) vibrational spectroscopy. At implanted concentrations ∧1 at.%, faceted H2 bubbles formed, enabling identification of energetically preferred surfaces, examination of passivating N-H states on these surfaces, and determination of the diffusivity-solubility product of the H. Additionally, the formation and evolution of point and extended defects arising from implantation and bubble formation were characterized. At implanted H concentrations ∧0.1 at.%, bubble formation was not observed, and ion-channeling analysis indicated a defect-related H site located within the [0001] channel.
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Ghara, Raghunath, and T. Roy Choudhury. "Bayesian approach to constraining the properties of ionized bubbles during reionization." Monthly Notices of the Royal Astronomical Society 496, no. 1 (June 8, 2020): 739–53. http://dx.doi.org/10.1093/mnras/staa1599.
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ABSTRACT A possible way to study the reionization of cosmic hydrogen is by observing the large ionized regions (bubbles) around bright individual sources, e.g. quasars, using the redshifted 21 cm signal. It has already been shown that matched filter-based methods are not only able to detect the weak 21 cm signal from these bubbles but also aid in constraining their properties. In this work, we extend the previous studies to develop a rigorous Bayesian framework to explore the possibility of constraining the parameters that characterize the bubbles. To check the accuracy with which we can recover the bubble parameters, we apply our method on mock observations appropriate for the upcoming SKA1-low. For a region of size ≳50 cMpc around a typical quasar at redshift 7, we find that ≈20 h of integration with SKA1-low will be able to constrain the size and location of the bubbles, as well as the difference in the neutral hydrogen fraction inside and outside the bubble, with $\lesssim 10$ per cent precision. The recovery of the parameters are more precise and the signal-to-noise ratio of the detected signal is higher when the bubble sizes are larger and their shapes are close to spherical. Our method can be useful in identifying regions in the observed field that contain large ionized regions and hence are interesting for following up with deeper integration times.
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Heiles, Carl. "Clustered Supernovae vs. The Gaseous Disk and Halo: A Rematch." International Astronomical Union Colloquium 120 (1989): 484–93. http://dx.doi.org/10.1017/s0252921100024295.
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ABSTRACT.Recent developments, both observational and theoretical, require a reevaluation of the effects of clustered supernovae on the two-dimensional porosity parameter Q2D and the rates of mass injection into the halo Ṁ of both cold and hot gas. Clustered supernovae produce two types of bubble. Most clusters produce breakthrough bubbles, which do no more than break through the dense gas disk. But large clusters produce enough energy to make blowout bubbles, which blow gas up into the halo. We calculate area filling factors and mass injection rates into the halo for different types of galaxy. We relate our calculations to two observables, the area covered by H I ‘holes’ and the area covered by giant H II regions. We also reiterate the difficulty of producing the very largest supershells by clusered supernovae.
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Ham, Phaly, Saret Bun, Pisut Painmanakul, and Kritchart Wongwailikhit. "Effective Analysis of Different Gas Diffusers on Bubble Hydrodynamics in Bubble Column and Airlift Reactors towards Mass Transfer Enhancement." Processes 9, no. 10 (October 1, 2021): 1765. http://dx.doi.org/10.3390/pr9101765.
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Even bubble column reactors (BCR) and airlift reactors (ALR) have been developed in terms of various related aspects towards mass transfer enhancement, the effective analysis of gas diffuser types on mass transfer and gas–liquid hydrodynamic characteristics is still limited. Therefore, the present study aims to analyze the relative effect of different types of air diffusers on bubble hydrodynamics and mass transfer performance to understand their behaviors and define the best type. The experiments were conducted by varying different diffuser types, reactor types (BCR and ALR), and superficial gas velocity (Vg) (0.12 to 1.00 cm/s). Five air diffusers including commercial fine sand (F-sand) and coarse sand (C-sand) diffusers, and acrylic perforated diffusers with orifice sizes of 0.3 mm (H-0.3), 0.6 mm (H-0.6), and 1.2 mm (H-1.2), were used in this study. For every condition, it was analyzed in terms of bubble hydrodynamics and oxygen mass transfer coefficient (KLa). Lastly, the selected diffusers that provided the highest KLa coefficient were evaluated with a solid media addition case. The results of both reactor classes showed that F-sand, the smallest orifice diffuser, showed the smallest air bubbles (3.14–4.90 mm) compared to other diffusers, followed by C-sand, which larger about 22–28% on average than F-sand. ALR exhibited a better ability to maintain smaller bubbles than BCR. Moreover, F-sand and C-sand diffusers showed a slower rising velocity through their smaller bubbles and the tiny bubble recirculation in ALR. Using F-sand in ALR, the rising velocity is about 1.60–2.58 dm/s, which is slower than that in BCR about 39–54%. F-sand and C-sand were also found as the significant diffusers in terms of interfacial area and gas hold-up. Then, the KLa coefficient was estimated in every diffuser and reactor under the varying of Vg. Up to 270% higher KLa value was achieved from the use of F-sand and C-sand compared to other types due to their smaller bubbles generated/maintained and longer bubble retention time through slower rising velocity. After adding 10% ring shape plastic media into the reactors with F-sand and C-sand diffusers, a better performance was achieved in terms of KLa coefficient (up to 39%) as well as gas hold-up and liquid mixing. Lastly, ALR also had a larger portion of mixed flow pattern than BCR. This eventually promoted mass transfer by enhancing the mixed flow regime.
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Shimabukuro, Hayato, Yi Mao, and Jianrong Tan. "Estimation of H ii Bubble Size Distribution from 21 cm Power Spectrum with Artificial Neural Networks." Research in Astronomy and Astrophysics 22, no. 3 (February 28, 2022): 035027. http://dx.doi.org/10.1088/1674-4527/ac4ca3.
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Abstract The bubble size distribution of ionized hydrogen regions probes information about the morphology of H II bubbles during reionization. Conventionally, the H II bubble size distribution can be derived from the tomographic imaging data of the redshifted 21 cm signal from the epoch of reionization, which, however, is observationally challenging even for upcoming large radio interferometer arrays. Given that these interferometers promise to measure the 21 cm power spectrum accurately, we propose a new method, which is based on artificial neural networks, to reconstruct the H II bubble size distribution from the 21 cm power spectrum. We demonstrate that reconstruction from the 21 cm power spectrum can be almost as accurate as being directly measured from the imaging data with fractional error ≲10%, even with thermal noise at the sensitivity level of the Square Kilometre Array. Nevertheless, the reconstruction implicitly exploits the modeling in reionization simulations, and hence the recovered H II bubble size distribution is not an independent summary statistic from the power spectrum, and should be used only as an indicator for understanding H II bubble morphology and its evolution.
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Zhang, Jingjing, Tengfei Zheng, Lin Tang, Hui Qi, Xiaoyu Wu, and Linlong Zhu. "Bubble-Enhanced Mixing Induced by Standing Surface Acoustic Waves (SSAWs) in Microchannel." Micromachines 13, no. 8 (August 18, 2022): 1337. http://dx.doi.org/10.3390/mi13081337.
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BAW-based micromixers usually achieve mixing enhancement with acoustic-induced bubbles, while SAW-based micromixers usually enhance mixing efficiency by varying the configuration of IDTs and microchannels. In this paper, bubble-enhanced acoustic mixing induced by standing surface acoustic waves (SSAWs) in a microchannel is proposed and experimentally demonstrated. Significant enhancement in the mixing efficiency was achieved after the bubbles were stimulated in our acoustofluidic microdevice. With an applied voltage of 5 V, 50 times amplified, the proposed mixing microdevice could achieve 90.8% mixing efficiency within 60 s at a flow rate of 240 μL/h. The bubbles were generated from acoustic cavitation assisted by the temperature increase resulting from the viscous absorption of acoustic energy. Our results also suggest that a temperature increase is harmful to microfluidic devices and temperature monitoring. Regulation is essential, especially in chemical and biological applications.
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Zhang, Zhenming, Peng Ma, Jianhong Dong, Min Liu, Yonggang Liu, and Chaobin Lai. "Effects of Different RH Degasser Nozzle Layouts on the Circulating Flow Rate." Materials 15, no. 23 (November 28, 2022): 8476. http://dx.doi.org/10.3390/ma15238476.
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The effects of gas flow rate and 22 kinds of nozzle layouts on the circulation flow rate were researched during the RH refining process using a water model and a mathematical model. Numerical simulations agreed with the water model experiment well. The results showed that the circulating flow rate increased with an increase of the gas flow rate. The critical value of the gas flow rate was 2.4 m3/h. Out of the 22 kinds of layouts, the 127-87 symmetrical layout was the optimal layout, for which the circulating flow rate reached 29.8 m3/h, the area of blind zone was the smallest and the mixing effect of the molten steel was the best. The working stroke and carrying capacity of the bubbles were important factors that affected the circulating flow rate. Among the four types of layouts, when the nozzles were in the one-side layout and the one-row layout, the main factor for improving the circulating flow rate was the working stroke of the bubbles. When nozzles were in the staggered layout and the symmetrical layout, the carrying capacity of the bubbles was the main factor for improving the circulating flow rate. For the same conditions, the carrying capacity of the bubbles had a greater effect on improving the circulating flow rate than the bubble stroke.
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Liu, Xiao, Huaican Chen, Jianfei Tong, Wenhao He, Xujing Li, Tianjiao Liang, Yuhong Li, and Wen Yin. "The Kinetic Behaviors of H Impurities in the Li/Ta Bilayer: Application for the Accelerator-Based BNCT." Nanomaterials 9, no. 8 (August 2, 2019): 1107. http://dx.doi.org/10.3390/nano9081107.
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Hydrogen bubble phenomenon is one of the key issues to be solved in the development of a long-life target system for boron neutron capture therapy (BNCT). In this study, we assessed the kinetic behaviors of H impurities in the nano-composite target from the atomic level. Firstly, two kinds of Li/Ta nanolayer models were constructed, based on the calculated lattice parameters and surface energies. The H solution energy, diffusion mechanism, and hydrogen bubbles formation in the Li/Ta nanostructured bilayer were studied, through theoretical modeling and simulation. Our results show that the Li/Ta interfaces are effective sinks of H atoms because the H solution energies in the interface are lower. Meanwhile, due to the relatively low diffusion barriers, the large-scale H transport through the interface is possible. In addition, although it is more likely to form hydrogen bubbles in the Ta layer, compared with the Li layer, the anti-blistering ability of Ta is more impressive compared with most of other candidate materials. Therefore, the Ta layer is able to act as the hydrogen absorber in the Li/Ta bilayer, and relieve the hydrogen damage of the Li layer in the large-scale proton radiations.
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Barnes, Ashley T., Elizabeth J. Watkins, Sharon E. Meidt, Kathryn Kreckel, Mattia C. Sormani, Robin G. Treß, Simon C. O. Glover, et al. "PHANGS–JWST First Results: Multiwavelength View of Feedback-driven Bubbles (the Phantom Voids) across NGC 628." Astrophysical Journal Letters 944, no. 2 (February 1, 2023): L22. http://dx.doi.org/10.3847/2041-8213/aca7b9.
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Abstract We present a high-resolution view of bubbles within the Phantom Galaxy (NGC 628), a nearby (∼10 Mpc), star-forming (∼2 M ⊙ yr−1), face-on (i ∼ 9°) grand-design spiral galaxy. With new data obtained as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS)-JWST treasury program, we perform a detailed case study of two regions of interest, one of which contains the largest and most prominent bubble in the galaxy (the Phantom Void, over 1 kpc in diameter), and the other being a smaller region that may be the precursor to such a large bubble (the Precursor Phantom Void). When comparing to matched-resolution Hα observations from the Hubble Space Telescope, we see that the ionized gas is brightest in the shells of both bubbles, and is coincident with the youngest (∼1 Myr) and most massive (∼105 M ⊙) stellar associations. We also find an older generation (∼20 Myr) of stellar associations is present within the bubble of the Phantom Void. From our kinematic analysis of the H I, H2 (CO), and H ii gas across the Phantom Void, we infer a high expansion speed of around 15 to 50 km s−1. The large size and high expansion speed of the Phantom Void suggest that the driving mechanism is sustained stellar feedback due to multiple mechanisms, where early feedback first cleared a bubble (as we observe now in the Precursor Phantom Void), and since then supernovae have been exploding within the cavity and have accelerated the shell. Finally, comparison to simulations shows a striking resemblance to our JWST observations, and suggests that such large-scale, stellar-feedback-driven bubbles should be common within other galaxies.
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Yusefi, Hossein, and Brandon Helfield. "Investigating the resonance response of a system of two ultrasound-driven lipid encapsulated microbubbles." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A110. http://dx.doi.org/10.1121/10.0010813.
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Ultrasound-stimulated microbubbles are clinical imaging agents and being developed for therapeutic applications. Here, we aim to understand the behaviour of two individual phospholipid-encapsulated microbubbles in close proximity to each other, typically the case given clinical doses. We developed a finite element model to study the radial resonance response of each microbubble within a two-microbubble system from 1–8 MHz with bubble diameters ranging from 2 to 4 μm, bubble center-to-center distances h = 8–24 μm, and peak-negative pressures of 30–45 kPa. For two identical microbubbles, our results show the frequency of maximum response (fMR) decreases (7%–10%) and the amplitude of maximum response (AMR) increases (9%–11%) as the microbubbles approach one another. For a two-bubble system of different microbubble sizes, the larger microbubble shows no change in fMR and a slight shift of AMR (2–3%). However, the smaller microbubble exhibits an increase in fMR (7–11%) and a significant decrease of AMR (38–52%). Furthermore, when in very close proximity (h = 8 μm), smaller bubbles exhibit a secondary resonance peak corresponding to the fMR of the larger bubble with amplitudes comparable to its primary resonance peak. Our work suggests that microbubble resonance behaviour is greatly affected by the presence of nearby bubbles, which has implications in imaging and therapy.
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Caldiroli, Paolo. "H-bubbles with prescribed large mean curvature." manuscripta mathematica 113, no. 1 (January 1, 2004): 125–42. http://dx.doi.org/10.1007/s00229-003-0427-8.
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Nazari, Sabereh, Sied Ziaedin Shafaei, Mahdi Gharabaghi, Rahman Ahmadi, Behzad Shahbazi, and Arash Tehranchi. "New Approach to Quartz Coarse Particles Flotation Using Nanobubbles, with Emphasis on the Bubble Size Distribution." International Journal of Nanoscience 19, no. 01 (January 29, 2019): 1850048. http://dx.doi.org/10.1142/s0219581x18500485.
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This study investigates the influence of bubble size distribution and operational parameters on the flotation behavior of quartz coarse particles. The parameters evaluated during this study include the different bubble size distribution, air flow rate and impeller speed. Experiments were conducted at three different bubble sizes: 110, 171 and 293[Formula: see text]nm as db(32). Then, the results were compared with common air bubbles of the conventional flotation process. The bubble size distribution was measured using a laser particle size analyzer (LPSA). Results showed that the recovery of [Formula: see text]m particles increased in presence of nano bubbles (NBs) up to 25% compared to the conventional flotation. The maximum recovery of 95.59% was obtained using NBs size of 171[Formula: see text]nm at the impeller speed of 900[Formula: see text]rpm and air flow rate of 30[Formula: see text]l/h. It was also indicated that NBs caused an increasing in flotation recovery for all the samples in any size ranges in comparison with the conventional method.
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Paskevicius, M., and C. E. Buckley. "Analysis of polydisperse bubbles in the aluminium–hydrogen system using a size-dependent contrast." Journal of Applied Crystallography 39, no. 5 (September 12, 2006): 676–82. http://dx.doi.org/10.1107/s0021889806032407.
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The characterization of hydrogen defects in an aluminium–hydrogen system was performed previously [Buckleyet al.(2001).J. Appl. Cryst.34, 119–129] using small-angle scattering, inelastic neutron scattering and electron microscopy techniques. This analysis resulted in the determination of the relative change in lattice parameter as a result of hydrogen introduction into the Al matrix. However, this method relied on the average volume of the bubbles of hydrogen and also the pressure in a bubble of average volume. The characterization of the Al–H system has been improved by considering the size polydispersity of the hydrogen bubbles. The determination of a volume-fraction size distribution of the bubbles from small-angle scattering data has allowed a polydispersity analysis to be undertaken. A size-dependent contrast has been utilized in the modification of the volume-fraction size distribution into a more accurate form that accounts for varying concentrations of hydrogen within bubbles of different sizes. The determination of the size-dependent contrast is based upon an equation of state for molecular hydrogen which incorporates the compressibility of hydrogen under high pressures. The formation of alane (AlH3) is also investigated, as it can be formed by the chemisorption of hydrogen in aluminium under high pressures. The polydispersity analysis has allowed a more accurate description of the Al–H system and can be applied to similar scattering systems where the scattering length density is not constant over the whole scattering size regime.
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Duplat, Jérôme. "Dynamics of expansion and collapse of explosive two-dimensional bubbles." Journal of Fluid Mechanics 859 (November 22, 2018): 677–90. http://dx.doi.org/10.1017/jfm.2018.804.
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An explosive gas mixture of hydrogen and oxygen is introduced in liquid water between two horizontal walls, forming a flat cylindrical bubble. Ignition and explosion of the bubble lead to a large depressurized cavity that finally implodes. We investigate the dynamics of the bubble collapse, which is qualitatively similar to the collapse of a spherical bubble. It exhibits a slightly weaker singularity than for spherical bubbles. We also analyse the explosion process. Starting with an initial radius $R_{0}$, the bubble reaches a maximal radius $R_{max}$ that depends on the gap thickness $h$ between the two walls: for a thinner gap, the condensation of water vapour is more efficient, the overpressure consecutive to the combustion is weaker, and its duration is shorter. This leads to a smaller maximal radius $R_{max}$. An indirect measurement of the transport coefficient of hot water vapour can be inferred from this observation.
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Zhou, Chang Chun. "Study of Strengthen Flotation Separation for Middle-Low Grade Bauxite." Advanced Materials Research 361-363 (October 2011): 844–47. http://dx.doi.org/10.4028/www.scientific.net/amr.361-363.844.
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The ore properties and strengthen separation of bauxite were studied in this paper. The parameters in strengthen separation, such as dosage of collectors, flotation turbulence and inflation etc., were also discussed. With the increase of collector dosage, the recovery of Al2O3increased.,When the collector dosage was 900 g/t, A/S of foam was 7.06 and the recovery was 86.39%. The recovery also increased with the increase of stirring speed. When the speed of agitation mixing impeller reached 1700 r/min, the recovery was 84.56% and A/S of concentrate was 6.71. With the increase of inflation, the number of bubbles increased, the contact opportunities between bubbles and mineral particles increased, and the recovery increased. When the inflation was 0.35 m3/h, the recovery was 85.21% and A/S of foam was 6.71,. With the increase of inflation over 0.35 m3/h, the enhancement of recovery was not limited and the bubble inclusions led to the decrease of recovery of Al2O3.
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Hennig, D., J. F. R. Archilla, and J. M. Romero. "Modelling the thermal evolution of enzyme-created bubbles in DNA." Journal of The Royal Society Interface 2, no. 2 (February 2005): 89–95. http://dx.doi.org/10.1098/rsif.2004.0024.
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The formation of bubbles in nucleic acids (NAs) is fundamental in many biological processes such as DNA replication, recombination, telomere formation and nucleotide excision repair, as well as RNA transcription and splicing. These processes are carried out by assembled complexes with enzymes that separate selected regions of NAs. Within the frame of a nonlinear dynamics approach, we model the structure of the DNA duplex by a nonlinear network of coupled oscillators. We show that, in fact, from certain local structural distortions, there originate oscillating localized patterns, that is, radial and torsional breathers, which are associated with localized H-bond deformations, reminiscent of the replication bubble. We further study the temperature dependence of these oscillating bubbles. To this aim, the underlying nonlinear oscillator network of the DNA duplex is brought into contact with a heat bath using the Nosé–Hoover method. Special attention is paid to the stability of the oscillating bubbles under the imposed thermal perturbations. It is demonstrated that the radial and torsional breathers sustain the impact of thermal perturbations even at temperatures as high as room temperature. Generally, for non-zero temperature, the H-bond breathers move coherently along the double chain, whereas at T =0 standing radial and torsional breathers result.
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Yeom, Geum-Su. "Correlations and Asymptotic Behaviors of the Shape Parameters of Floating Bubbles Using an Improved Numerical Procedure." Applied Sciences 12, no. 4 (February 9, 2022): 1804. http://dx.doi.org/10.3390/app12041804.
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An improved numerical procedure is used to present the correlations between the shape parameters and Bond numbers of floating bubbles for a wider range of Bond numbers (5×10−5<Bo<5000) than the previously reported range of Bond numbers (0.003<Bo<241), and their asymptotic relations as Bo → 0 and Bo → ∞. The proposed method is proven to be more precise and robust than the conventional methods in comparison with previous numerical and experimental results. In addition, the profile of floating bubbles and the related parameters are presented for a wide range of bubble sizes. The shape parameters are divided into three distinct Bond number regions, and are fitted with a fifth-order polynomial as a function of Bond number on a log-log scale for each region. The parameters show two asymptotes, which can be expressed in a simple power law. In addition, the dimensionless maximum depth of the floating bubble is obtained as H=0.7291015 when Bo=4.755563. These correlations and asymptotic relations are expected to assist in the development of scale models of dynamic bubble-related phenomena such as bubble bursting.
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Filella, Audrey, Patricia Ern, and Véronique Roig. "Oscillatory motion and wake of a bubble rising in a thin-gap cell." Journal of Fluid Mechanics 778 (July 30, 2015): 60–88. http://dx.doi.org/10.1017/jfm.2015.355.
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We investigate the characteristics of the oscillatory motion and wake of confined bubbles freely rising in a thin-gap cell ($h=3.1~\text{mm}$ width). Once the diameter $d$ of the bubble in the plane of the cell is known, the mean vertical velocity of the bubble $V_{b}$ is proportional to the gravitational velocity $(h/d)^{1/6}\sqrt{gd}$, where $g$ is the gravitational acceleration. This velocity is used to build the Reynolds number $Re=V_{b}d/{\it\nu}$ that characterizes the flow induced by the bubble in the surrounding liquid (of kinematic viscosity ${\it\nu}$), and which determines at leading order the mean deformation of the bubble given by the aspect ratio ${\it\chi}$ of the ellipse equivalent to the bubble contour. We then show that in the reference frame associated with the bubble (having a fixed origin and axes corresponding to the minor and major axes of the equivalent ellipse) the characteristics of its oscillatory motion in the plane of the cell display remarkable properties in the range $1200<Re<3000$ and $h/d<0.4$. In particular, the velocity of the bubble presents along its path an almost constant component along its minor axis (fluctuations in time of approximately 5 %), given by $V_{a}/V_{b}\simeq 0.92$ for all $Re$. The dimensionless amplitude of oscillation of the angular velocity is also constant for all $Re$, $\tilde{r}d/V_{b}\simeq 0.75$, while that of the transverse velocity of the bubble (along its major axis) is given by $\tilde{V}_{t}/V_{b}\simeq 0.32{\it\chi}$, reaching values comparable to those of the axial velocity $V_{a}$ for the most deformed bubbles (${\it\chi}\approx 3$). Furthermore, the frequency $f$ of oscillation scales with the inertial time scale based on the transverse velocity of the bubble $\tilde{V}_{t}$, corresponding to a constant Strouhal number $St^{\ast }=fd/\tilde{V}_{t}\simeq 0.27$. Using high-frequency particle image velocimetry, we investigate in detail the properties of the wake associated with the oscillatory motion of sufficiently confined bubbles. We observe that vortex shedding occurs for a maximal transverse velocity $V_{t}$ of the bubble, corresponding to a maximal drift angle of the bubble. Furthermore, the measured vorticity of the vortex at detachment corresponds to the estimation $V_{b}{\it\chi}^{3/2}/d$ of the vorticity produced at the bubble surface. Three stages then emerge concerning the evolution in time of the wake generated by the bubble. For one to two periods of oscillation $T_{x}$ following the release of a vortex, a rapid decay of the vorticity of the released vortex is observed. Meanwhile, the released vortex located initially at a distance of approximately one diameter from the bubble centre moves outwards from the bubble path and expands. At intermediate times, the vortex street undergoes vortex pairing. When viscous effects become predominant at a time of the order of the viscous time scale ${\it\tau}_{{\it\nu}}=h^{2}/(4{\it\nu})$, the vortex street becomes frozen and decays exponentially in place.
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Liu, Gang, Qiang Fu, and Junjun Kang. "Cavitation and Negative Pressure: A Flexible Water Model Molecular Dynamics Simulation." International Journal of Statistics and Probability 8, no. 2 (February 22, 2019): 172. http://dx.doi.org/10.5539/ijsp.v8n2p172.
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The critical negative pressure for cavitation in water has been theoretically predicted to be in the range of -100 to -200 MPa at room temperature, whereas values around -30 MPa have been obtained by many experiments. The discrepancy has yet to be resolved. Molecular dynamics (MD) is an effective method of observing bubble nucleation, however, most MD simulations use a rigid water model and do not take the effects of intermolecular vibrations into account. In this manuscript we perform MD simulations to study cavitation in water by using a TIP4P/2005f model under volumecontrolled stretching. It is found that the critical negative pressure of water was -168 MPa in the simulation and the critical negative pressure of water containing 50 oxygen molecules was -150 MPa. Hydrogen bonds played a major role in the cavitation process: the breaking of hydrogen bonds promoted bubble generation and growth. The O-H bond could release energy to increase the amount of potential energy in the system, so that cavitation was more likely to occur. When cavitation occurred, the O-H bond could absorb energy to reduce the amount of potential energy in the system, which will promote the growth of bubbles, and stabilise the cavitation bubbles.
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Trott, C. M., C. H. Jordan, J. L. B. Line, C. R. Lynch, S. Yoshiura, B. McKinley, P. Dayal, et al. "Constraining the 21 cm brightness temperature of the IGM at z = 6.6 around LAEs with the murchison widefield array." Monthly Notices of the Royal Astronomical Society 507, no. 1 (August 3, 2021): 772–80. http://dx.doi.org/10.1093/mnras/stab2235.
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ABSTRACT The locations of Ly α-emitting galaxies (LAEs) at the end of the Epoch of Reionization (EoR) are expected to correlate with regions of ionized hydrogen, traced by the redshifted 21 cm hyperfine line. Mapping the neutral hydrogen around regions with detected and localized LAEs offers an avenue to constrain the brightness temperature of the Universe within the EoR by providing an expectation for the spatial distribution of the gas, thereby providing prior information unavailable to power spectrum measurements. We use a test set of 12 h of observations from the Murchison Widefield Array (MWA) in extended array configuration, to constrain the neutral hydrogen signature of 58 LAEs, detected with the Subaru Hypersuprime Cam in the Silverrush survey, centred on z = 6.58. We assume that detectable emitters reside in the centre of ionized H ii bubbles during the end of reionization, and predict the redshifted neutral hydrogen signal corresponding to the remaining neutral regions using a set of different ionized bubble radii. A pre-whitening matched filter detector is introduced to assess detectability. We demonstrate the ability to detect, or place limits upon, the amplitude of brightness temperature fluctuations, and the characteristic H ii bubble size. With our limited data, we constrain the brightness temperature of neutral hydrogen to ΔTB <30 mK (<200 mK) at 95 per cent (99 per cent) confidence for lognormally distributed bubbles of radii, RB = 15 ± 2h−1 cMpc.
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Sandin, Christer, Matthias Steffen, Ralf Jacob, Detlef Schönberner, Ute Rühling, Wolf-Rainer Hamann, and Helge Todt. "The role of heat conduction to the formation of [WC]-type planetary nebulae." Proceedings of the International Astronomical Union 7, S283 (July 2011): 494–95. http://dx.doi.org/10.1017/s1743921312012094.
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AbstractX-ray observations of young Planetary Nebulæ (PNe) have revealed diffuse emission in extended regions around both H-rich and H-deficient central stars. In order to also reproduce physical properties of H-deficient objects, we have, at first, extended our time-dependent radiation-hydrodynamic models with heat conduction for such conditions. Here we present some of the important physical concepts, which determine how and when a hot wind-blown bubble forms. In this study we have had to consider the, largely unknown, evolution of the CSPN, the slow (AGB) wind, the fast hot-CSPN wind, and the chemical composition. The main conclusion of our work is that heat conduction is needed to explain X-ray properties of wind-blown bubbles also in H-deficient objects.
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Thom, Stephen R., Tatyana N. Milovanova, Marina Bogush, Ming Yang, Veena M. Bhopale, Neal W. Pollock, Marko Ljubkovic, et al. "Bubbles, microparticles, and neutrophil activation: changes with exercise level and breathing gas during open-water SCUBA diving." Journal of Applied Physiology 114, no. 10 (May 15, 2013): 1396–405. http://dx.doi.org/10.1152/japplphysiol.00106.2013.
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The study goal was to evaluate responses in humans following decompression from open-water SCUBA diving with the hypothesis that exertion underwater and use of a breathing mixture containing more oxygen and less nitrogen (enriched air nitrox) would alter annexin V-positive microparticle (MP) production and size changes and neutrophil activation, as well as their relationships to intravascular bubble formation. Twenty-four divers followed a uniform dive profile to 18 m of sea water breathing air or 22.5 m breathing 32% oxygen/68% nitrogen for 47 min, either swimming with moderately heavy exertion underwater or remaining stationary at depth. Blood was obtained pre- and at 15 and 120 min postdive. Intravascular bubbles were quantified by transthoracic echocardiography postdive at 20-min intervals for 2 h. There were no significant differences in maximum bubble scores among the dives. MP number increased 2.7-fold, on average, within 15 min after each dive; only the air-exertion dive resulted in a significant further increase to 5-fold over baseline at 2 h postdive. Neutrophil activation occurred after all dives. For the enriched air nitrox stationary at depth dive, but not for other conditions, the numbers of postdive annexin V-positive particles above 1 μm in diameter were correlated with intravascular bubble scores (correlation coefficients ∼0.9, P < 0.05). We conclude that postdecompression relationships among bubbles, MPs, platelet-neutrophil interactions, and neutrophil activation appear to exist, but more study is required to improve confidence in the associations.
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Jinno, Ryusuke, Thomas Konstandin, Henrique Rubira, and Jorinde van de Vis. "Effect of density fluctuations on gravitational wave production in first-order phase transitions." Journal of Cosmology and Astroparticle Physics 2021, no. 12 (December 1, 2021): 019. http://dx.doi.org/10.1088/1475-7516/2021/12/019.
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Abstract We study the effect of density perturbations on the process of first-order phase transitions and gravitational wave production in the early Universe. We are mainly interested in how the distribution of nucleated bubbles is affected by fluctuations in the local temperature. We find that large-scale density fluctuations (H * < k * < β) result in a larger effective bubble size at the time of collision, enhancing the produced amplitude of gravitational waves. The amplitude of the density fluctuations necessary for this enhancement is 𝒫ζ (k *) ≳ (β/H *)-2, and therefore the gravitational wave signal from first-order phase transitions with relatively large β/H * can be significantly enhanced by this mechanism even for fluctuations with moderate amplitudes.
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Wang, Ao, Yuxue Zhong, Guanghang Wang, Jian Huang, Jingzhu Wang, and Yiwei Wang. "Experimental study on the formation of two axial jets of cavitation bubbles near soft membranes with different thicknesses." AIP Advances 12, no. 9 (September 1, 2022): 095023. http://dx.doi.org/10.1063/5.0107339.
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A cavitation bubble collapses non-spherically, splits into two smaller bubbles, and induces two axial jets flowing in opposite directions near a soft membrane. The soft membrane is deformed and even pierced after the impact of the downward jet. In this paper, we experimentally studied the formation of two axial jets of a spark-induced bubble near Ecoflex membranes with different thicknesses. Assuming that the millimeter-sized bubble is filled with an ideal gas and collapses adiabatically in water, the dominant dimensionless parameters, the stiffness ( d′) and stand-off distance ( h*), determining the formation of the two axial jets, are obtained, and the value of d′ is varied by changing the membrane thickness. Two parameter plots for the regimes of bubble jetting and no jetting were obtained. The critical h* of the bubble jetting increased exponentially with increasing d′, reaching a maximum of 1.1 at d′ = 0.045 56 (the thickness d = 10 mm). This was because the counteracting force induced by the rebounding of the deformed membrane grew in strength. After that, the h* remained constant since the counteracting force was unchanged due to the feature changes of the membrane deformation. Consequently, we obtain a function of the boundary line between the regimes. The sub-regime of the membrane piercing was obtained in the regime of bubble jetting. It was found that the velocity of membrane deformation induced by the jet impact was an important factor in membrane piercing.
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Kang, Shu Mei, Ming Gang Shen, and Cheng Wei Li. "Cold Model Experiments and Mechanism on Inclusion Removal by Ultrasonic Horn." Advanced Materials Research 750-752 (August 2013): 404–7. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.404.
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The effect of power and tool rod position on inclusion removal was studied in the ladle refining cold model when the organic particles were used to imitate the inclusion. The mechanism of removing inclusion by cavitation bubbles was investigated. Both the transient bubbles and stable bubbles can promote the removal of inclusion; as the power increase, cavitation intensity increases, the number of cavitation bubbles increases, the collision probability of the cavitation bubbles increases with the inclusion, the efficiency of removing inclusion increases; as the wave source into the liquid is 1/2 H, the effect of removing inclusion is the best.
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Frigeri, Cesare, L. Nasi, M. Serényi, A. Csik, Z. Erdélyi, and Dezső L. Beke. "Influence of Hydrogen on the Structural Stability of Annealed Ultrathin Si/Ge Amorphous Layers." Solid State Phenomena 156-158 (October 2009): 325–30. http://dx.doi.org/10.4028/www.scientific.net/ssp.156-158.325.
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The influence of hydrogen on the structural stability of multilayers made of ultrathin (3 nm) Si and Ge amorphous layers submitted to annealing to activate Si and Ge intermixing has been studied by TEM and AFM. By energy dispersive microanalysis the interdiffusion of Si and Ge has been observed. The Si/Ge multilayers, however, underwent remarkable structural degradation because of the formation of hydrogen bubbles which give rise to surface bumps and eventually craters when the bubbles blow up because of too high internal pressure in samples with high H content and annealed at high temperatures. The hydrogen forming the bubbles comes from the rupture of the Si-H and Ge-H bonds activated by the thermal energy of the annealing and by the energy released by the recombination of thermally generated electron hole pairs.
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Borisova, Anastassia Y., Stefano Salvi, German Velasquez, Guillaume Estrade, Aurelia Colin, and Sophie Gouy. "Quantification of major and trace elements in fluid inclusions and gas bubbles by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with no internal standard: a new method." European Journal of Mineralogy 33, no. 3 (June 2, 2021): 305–14. http://dx.doi.org/10.5194/ejm-33-305-2021.
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Abstract. Recent advances in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) open new perspectives for quantification of trace metals and metalloids in mineral-hosted fluid inclusions and glass-hosted gas bubbles. This work is devoted to a new method applied to quantify element concentrations (at parts-per-million and weight percent levels) in natural and synthetic fluid inclusions and gas bubbles by using only an external calibrator in cases where internal standardization is unavailable. For example, this method can be applied to calculate element (metal and metalloid) concentrations in carbonic (C–O–H) fluid inclusions and bubbles. The method is devoted to measuring incompatible (with the host mineral and glass) trace elements originally dissolved into the trapped fluid. The method requires precise estimation of the fluid density, the inclusion/bubble volume or average radius, and measurement of the laser ablation crater radius by independent microanalytical techniques as well as accurate data on the concentration of major/minor elements compatible with the host mineral (or host glass). This method, applicable for analyses of hydrous carbonic fluid inclusions and gas bubbles hosted in silicate minerals and glasses, relies on the absence of a matrix effect between fluid, host mineral and daughter phases (silicate, oxide or sulfide) and the external calibrator (e.g., reference silicate glasses) during the LA-ICP-MS analysis, an assumption validated by the use of femtosecond lasers.
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Wilbur, J. C., S. D. Phillips, T. G. Donoghue, D. L. Alvarenga, D. A. Knaus, P. J. Magari, and J. C. Buckey. "Signals consistent with microbubbles detected in legs of normal human subjects after exercise." Journal of Applied Physiology 108, no. 2 (February 2010): 240–44. http://dx.doi.org/10.1152/japplphysiol.00615.2009.
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Exercise may produce micronuclei (presumably gas-filled bubbles) in tissue, which could serve as nucleation sites for bubbles during subsequent decompression stress. These micronuclei have never been directly detected in humans. Dual-frequency ultrasound (DFU) is a resonance-based, ultrasound technique capable of detecting and sizing small stationary bubbles. We surveyed for bubbles in the legs of six normal human subjects (ages 28–52 yr) after exercise using DFU. Eleven marked sites on the left thigh and calf were imaged using standard imaging ultrasound. Subjects then rested in a reclining chair for 2 h before exercise. For the hour before exercise, a series of baseline measurements was taken at each site using DFU. At least six baseline measurements were taken at each site. Subjects exercised at 80% of their age-adjusted maximal heart rate for 30 min on an upright bicycle ergometer. After exercise, the subjects returned to the chair, and multiple postexercise measurements were taken at the marked sites. Measurements continued until no further signals consistent with bubbles were returned or 1 h had elapsed. All subjects showed signals consistent with bubbles after exercise at at least one site. The percentage of sites in a given subject showing signals significantly greater than baseline ( P < 0.01) at first measurement ranged from 9.1 to 100%. Overall, 58% of sites showed signals consistent with bubbles at the first postexercise measurement. Signals decreased over time after exercise. These data strongly suggest that exercise produces bubbles detectable using DFU.
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Kabanovic, S., N. Schneider, V. Ossenkopf-Okada, F. Falasca, R. Güsten, J. Stutzki, R. Simon, et al. "Self-absorption in [C II], 12CO, and H I in RCW120." Astronomy & Astrophysics 659 (March 2022): A36. http://dx.doi.org/10.1051/0004-6361/202142575.
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Aims. Revealing the 3D dynamics of H II region bubbles and their associated molecular clouds and H I envelopes is important for developing an understanding of the longstanding problem as to how stellar feedback affects the density structure and kinematics of the different phases of the interstellar medium. Methods. We employed observations of the H II region RCW 120 in the [C II] 158 μm line, observed within the Stratospheric Observatory for Infrared Astronomy (SOFIA) legacy program FEEDBACK, and in the 12CO and 13CO (3 →2) lines, obtained with the Atacama Pathfinder Experiment (APEX) to derive the physical properties of the gas in the photodissociation region (PDR) and in the molecular cloud. We used high angular resolution H I data from the Southern Galactic Plane Survey to quantify the physical properties of the cold atomic gas through H I self-absorption. The high spectral resolution of the heterodyne observations turns out to be essential in order to analyze the physical conditions, geometry, and overall structure of the sources. Two types of radiative transfer models were used to fit the observed [C II] and CO spectra. A line profile analysis with the 1D non-LTE radiative transfer code SimLine proves that the CO emission cannot stem from a spherically symmetric molecular cloud configuration. With a two-layer multicomponent model, we then quantified the amount of warm background and cold foreground gas. To fully exploit the spectral-spatial information in the CO spectra, a Gaussian mixture model was introduced that allows for grouping spectra into clusters with similar properties. Results. The CO emission arises mostly from a limb-brightened, warm molecular ring, or more specifically a torus when extrapolated in 3D. There is a deficit of CO emission along the line-of-sight toward the center of the H II region which indicates that the H II region is associated with a flattened molecular cloud. Self-absorption in the CO line may hide signatures of infalling and expanding molecular gas. The [C II] emission arises from an expanding [C II] bubble and from the PDRs in the ring/torus. A significant part of [C II] emission is absorbed in a cool (~60–100 K), low-density (<500 cm−3) atomic foreground layer with a thickness of a few parsec. Conclusions. We propose that the RCW 120 H II region formed in a flattened, filamentary, or sheet-like, molecular cloud and is now bursting out of its parental cloud. The compressed surrounding molecular layer formed a torus around the spherically expanding H II bubble. This scenario can possibly be generalized for other H II bubbles and would explain the observed “flat” structure of molecular clouds associated with H II bubbles. We suggest that the [C II] absorption observed in many star-forming regions is at least partly caused by low-density, cool, H I -envelopes surrounding the molecular clouds.
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Lhuissier, H., and E. Villermaux. "Bursting bubble aerosols." Journal of Fluid Mechanics 696 (November 18, 2011): 5–44. http://dx.doi.org/10.1017/jfm.2011.418.
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AbstractWe depict and analyse the complete evolution of an air bubble formed in a water bulk, from the time it emerges at the liquid surface, up to its fragmentation into dispersed drops. To this end, experiments describing the drainage of the bubble cap film, its puncture and the resulting bursting dynamics determining the aerosol formation are conducted on tapwater bubbles. We discover that the mechanism of marginal pinching at the bubble foot and associated convection motions in the bubble cap, known as marginal regeneration, both drive the bubble cap drainage rate, and are responsible for its puncture. The resulting original film thickness $h$ evolution law in time, supplemented with considerations about the nucleation of holes piercing the film together culminate in a determination of the cap film thickness at bursting ${h}_{b} \propto {R}^{2} / \mathscr{L}$, where $R$ is the bubble cap radius of curvature, and $\mathscr{L}$ a length which we determine. Subsequent to a hole nucleation event, the cap bursting dynamics conditions the resulting spray. The latter depends both on the bubble shape prescribed by $R/ a$, where $a$ is the capillary length based on gravity, and on ${h}_{b} $. The mean drop size $\langle d\rangle \ensuremath{\sim} {R}^{3/ 8} \hspace{0.167em} { h}_{b}^{5/ 8} $, the number of drops generated per bubble $N\ensuremath{\sim} \mathop{ (R/ a)}\nolimits ^{2} \mathop{ (R/ {h}_{b} )}\nolimits ^{7/ 8} $ and the drop size distribution $P(d)$ are derived, comparing well with measurements. Combined with known bubble production rates over the ocean, our findings offer an adjustable parameter-free prediction for the aerosol flux and spray structure caused by bubble bursting in this precise context.
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Jayasinghe, Tharindu, Don Dixon, Matthew S. Povich, Breanna Binder, Jose Velasco, Denise M. Lepore, Duo Xu, et al. "The Milky Way Project second data release: bubbles and bow shocks." Monthly Notices of the Royal Astronomical Society 488, no. 1 (June 25, 2019): 1141–65. http://dx.doi.org/10.1093/mnras/stz1738.
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ABSTRACT Citizen science has helped astronomers comb through large data sets to identify patterns and objects that are not easily found through automated processes. The Milky Way Project (MWP), a citizen science initiative on the Zooniverse platform, presents internet users with infrared (IR) images from Spitzer Space Telescope Galactic plane surveys. MWP volunteers make classification drawings on the images to identify targeted classes of astronomical objects. We present the MWP second data release (DR2) and an updated data reduction pipeline written in python. We aggregate ∼3 million classifications made by MWP volunteers during the years 2012–2017 to produce the DR2 catalogue, which contains 2600 IR bubbles and 599 candidate bow shock driving stars. The reliability of bubble identifications, as assessed by comparison to visual identifications by trained experts and scoring by a machine-learning algorithm, is found to be a significant improvement over DR1. We assess the reliability of IR bow shocks via comparison to expert identifications and the colours of candidate bow shock driving stars in the 2MASS point-source catalogue. We hence identify highly reliable subsets of 1394 DR2 bubbles and 453 bow shock driving stars. Uncertainties on object coordinates and bubble size/shape parameters are included in the DR2 catalogue. Compared with DR1, the DR2 bubbles catalogue provides more accurate shapes and sizes. The DR2 catalogue identifies 311 new bow shock driving star candidates, including three associated with the giant H ii regions NGC 3603 and RCW 49.
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Wang, Zhonghao, Wei Lin, Wei Wang, Zhangwei Wang, Jimin Li, Jianmin Xu, and Jiuyang Yu. "Research on performance optimization and mechanism of electrochemical water softening applied by pulse power supply." Water Science and Technology 84, no. 9 (October 4, 2021): 2432–45. http://dx.doi.org/10.2166/wst.2021.436.
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Abstract In order to promote the application of electrochemical water softening technology in industrial circulating cooling water systems, electric field type, cathode structure and solution residence time are selected for optimization analysis of an electrochemical water softening device. The experimental results show that the water softening performance per unit area of mesh cathode is better than that of a plate cathode. In addition, the softening amount per unit area of the mesh cathode can be further increased when the high-frequency (HF) power supply is applied. When the HF power supply is applied, the softening amount per unit area is 158.58 g/m2·h−1 more than when the direct current power supply is applied. In order to explore the growth mechanism of calcium carbonate, micro-analysis technology and high-speed bubble photography technology are used. The results show that the bubbles escape along the longitudinal direction of the electrode plate, and the main growth direction of calcium carbonate growth is consistent with the escape direction of the bubble; that is, the bubbles grow along the longitudinal direction of the electrode plate. The special structure of the diamond-shaped mesh cathode facilitates the growth of calcium carbonate crystals.
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Foster, Philip P., Alan H. Feiveson, and Aladin M. Boriek. "Predicting time to decompression illness during exercise at altitude, based on formation and growth of bubbles." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 279, no. 6 (December 1, 2000): R2317—R2328. http://dx.doi.org/10.1152/ajpregu.2000.279.6.r2317.
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For altitude decompressions, we hypothesized that reported onset times of limb decompression illness (DCI) pain symptoms follow a probability distribution related to total bubble volume [Vb·( t)] as a function of time. Furthermore, we hypothesized that the probability of ever experiencing DCI during a decompression is associated with the cumulative volume of bubbles formed. To test these hypotheses, we first used our previously developed formation-and-growth model ( Am J Physiol Regulatory Integrative Comp Physiol 279: R2304–R2316, 2000) to simulate Vb·(t) for 20 decompression profiles in which 334 human subjects performed moderate repetitive skeletal muscle exercise (827 kJ/h) in an altitude chamber. Using survival analysis, we determined that, for a controlled condition of exercise, the fraction of the subject population susceptible to DCI can be approximately expressed as a power function of the formation-and-growth model-predicted cumulative volume of bubbles throughout the altitude exposure. Furthermore, for this fraction, the probability density distribution of DCI onset times is approximately equal to the ratio of the time course of formation-and growth-modeled total bubble volume to the predicted cumulative volume.
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Karimov, Umed, and Dušan Repovš. "On $\check{H}^n$-bubbles in n-dimensional compacta." Colloquium Mathematicum 75, no. 1 (1998): 39–51. http://dx.doi.org/10.4064/cm-75-1-39-51.
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Arieli, Ran, Soliman Khatib, and Jacob Vaya. "Presence of dipalmitoylphosphatidylcholine from the lungs at the active hydrophobic spots in the vasculature where bubbles are formed on decompression." Journal of Applied Physiology 121, no. 3 (September 1, 2016): 811–15. http://dx.doi.org/10.1152/japplphysiol.00649.2016.
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Most severe cases of decompression illness are caused by vascular bubbles. We showed that there are active hydrophobic spots (AHS) on the luminal aspect of ovine blood vessels where bubbles are produced after decompression. It has been suggested that AHS may be composed of lung surfactant. Dipalmitoylphosphatidylcholine (DPPC) is the main component of lung surfactants. Blood samples and four blood vessels, the aorta, superior vena cava, pulmonary vein, and pulmonary artery, were obtained from 11 slaughtered sheep. Following exposure to 1,013 kPa for 20.4 h, we started photographing the blood vessels 15 min after the end of decompression for a period of 30 min to determine AHS by observing bubble formation. Phospholipids were extracted from AHS and from control tissue and plasma for determination of DPPC. DPPC was found in all blood vessel samples and all samples of plasma. The concentration of DPPC in the plasma samples ( n = 8) was 2.04 ± 0.90 μg/ml. The amount of DPPC in the AHS which produced four or more bubbles ( n = 16) was 1.59 ± 0.92 μg. This was significantly higher than the value obtained for AHS producing less than four bubbles and for control samples ( n = 19) (0.97 ± 0.61 μg, P = 0.027). DPPC leaks from the lungs into the blood, settling on the luminal aspect of the vasculature to create AHS. Determining the constituents of the AHS might pave the way for their removal, resulting in a dramatic improvement in diver safety.