Stream Of Gas Bubbles Research Articles

Strategies to improve the challenges of classic dispersive liquid-liquid microextraction for determination of the parabens in personal care products-One step closer to green analytical chemistry

Gas flow-assisted dispersive liquid-phase microextraction based on deep eutectic solvent was used to determine parabens in personal care products such as mouthwash, lidocaine gel, aloe vera gel, and skin tonic. A homemade extraction device was innovated, in which by passing the stream of gas bubbles through the deep eutectic solvent a thin layer of the extraction phase is coated on the surface of the bubbles. The extraction is finally achieved when the bubbles are going up through the sample. The single-factor experiments and response surface methodology were applied to optimize the independent variables. The linear range of the method was 0.5 to 1000 µg L−1, the coefficient of determination for the goal analytes was higher than 0.9989, the instrumental limit of detections were in the range 0.2–0.3 μg L−1, and the instrumental limit of quantifications were in the range 0.5–1.1 μg L−1, the relative standard deviations were <5.2% for repeatability and <11.2% for intermediate precision, and the enrichment factors were 66 to 87 obtained under the optimized conditions. A spiking approach by means of standard material was used to estimate accuracy. The relative recoveries were in the range 95.8–105.2%. By using mentioned strategies, the organic waste and energy consumption reduced, toxic reagents replaced with safer ones, and operator safety enhanced. Accordingly, these benefits have been simultaneously attained and, the proposed method was one step closer to automation and sustainable analytical chemistry.

AC Pulsed Field Ablation Is Feasible and Safe in Atrial and Ventricular Settings: A Proof-of-Concept Chronic Animal Study.

IntroductionPulsed field ablation (PFA) exploits the delivery of short high-voltage shocks to induce cells death via irreversible electroporation. The therapy offers a potential paradigm shift for catheter ablation of cardiac arrhythmia. We designed an AC-burst generator and therapeutic strategy, based on the existing knowledge between efficacy and safety among different pulses. We performed a proof-of-concept chronic animal trial to test the feasibility and safety of our method and technology.MethodsWe employed 6 female swine – weight 53.75 ± 4.77 kg – in this study. With fluoroscopic and electroanatomical mapping assistance, we performed ECG-gated AC-PFA in the following settings: in the left atrium with a decapolar loop catheter with electrodes connected in bipolar fashion; across the interventricular septum applying energy between the distal electrodes of two tip catheters. After procedure and 4-week follow-up, the animals were euthanized, and the hearts were inspected for tissue changes and characterized. We perform finite element method simulation of our AC-PFA scenarios to corroborate our method and better interpret our findings.ResultsWe applied square, 50% duty cycle, AC bursts of 100 μs duration, 100 kHz internal frequency, 900 V for 60 pulses in the atrium and 1500 V for 120 pulses in the septum. The inter-burst interval was determined by the native heart rhythm – 69 ± 9 bpm. Acute changes in the atrial and ventricular electrograms were immediately visible at the sites of AC-PFA – signals were elongated and reduced in amplitude (p < 0.0001) and tissue impedance dropped (p = 0.011). No adverse event (e.g., esophageal temperature rises or gas bubble streams) was observed – while twitching was avoided by addition of electrosurgical return electrodes. The implemented numerical simulations confirmed the non-thermal nature of our AC-PFA and provided specific information on the estimated treated area and need of pulse trains. The postmortem chest inspection showed no peripheral damage, but epicardial and endocardial discolorations at sites of ablation. T1-weighted scans revealed specific tissue changes in atria and ventricles, confirmed to be fibrotic scars via trichrome staining. We found isolated, transmural and continuous scars. A surviving cardiomyocyte core was visible in basal ventricular lesions.ConclusionWe proved that our method and technology of AC-PFA is feasible and safe for atrial and ventricular myocardial ablation, supporting their systematic investigation into effectiveness evaluation for the treatment of cardiac arrhythmia. Further optimization, with energy titration or longer follow-up, is required for a robust atrial and ventricular AC-PFA.

Перенос свободного метана струйными газовыделениями из анаэробных в аэробные воды Чёрного моря

«Дыхание недр» в форме метановых струйных газовыделений из морского дна (метановые сипы, или пузырьковые эманации) — явление планетарного масштаба, на которое обратили внимание лишь в конце XX столетия. Изучение этого явления как важного звена процессов взаимодействия литосферы, гидросферы, атмосферы и биосферы не потеряло своей актуальности до настоящего времени. В данной работе определены потоки метана в известном районе интенсивных метанопроявлений биогенной природы, географически привязанных к палеоруслу р. Днепр в северо-западной части Чёрного моря. Впервые оценено, что поток струйного (свободного) метана из анаэробных в аэробные воды на участке активных метановых газовыделений в районе палеорусла р. Днепр в диапазоне глубин 140–725 м составляет (в среднем по участку) 1,2·10³ м³·км−2·год−1 (STP), или 2,8 % от выделившегося из дна струйного метана. Величина исследованного потока — 4,2 % от удельного потока струйного метана в водный столб на шельфовом участке (глуби́ны менее 140 м) в этом же районе. Полученная в работе оценка потока метана — значимый экологический фактор в условиях стратификации вод Чёрного моря, где перенос метана струйными газовыделениями является основным механизмом внесения глубоководного метана в биогеохимические циклы и процессы трансформации углерода аэробной зоны Чёрного моря.

Influx of streaming methane into anoxic waters of the Black Sea basin

Based on data on the spatial distribution and fluxes of streaming (bubbling) methane within the Black Sea, the rate of dissolved methane inflow to Black Sea deep waters was assessed. Calculations showed that gas bubble streams annually replenish the methane budget in the Black Sea by 1.2 109 m3, or 0.9 Tg, which is considerably less than determined by known biogeochemical estimates of components of methane balance in the Black Sea.

Influx of Streaming Methane into Anoxic Waters of the Black Sea Basin

Based on data on the spatial distribution and fluxes of streaming (bubbling) methane within the Black Sea, the rate of dissolved methane inflow to Black Sea deep waters was assessed. Calculations showed that gas bubble streams annually replenish the methane budget in the Black Sea by 1.2 10 9 m 3 , or 0.9 Tg, which is considerably less than determined by known biogeochemical estimates of components of methane balance in the Black Sea.

Seafloor sealing, doming, and collapse associated with gas seeps and authigenic carbonate structures at Venere mud volcano, Central Mediterranean

Methane release from the seafloor is commonly associated with chemosynthesis-based cold seep ecosystems that facilitate the precipitation of authigenic carbonates. It has been proposed that carbonate growth results in self-sealing, but little is known regarding the evolution of cold seep structures in relation to fluid migration pathways. This study investigates structures resulting from gas seepage along ring faults peripheral to Venere mud volcano (1600 m water depth), based on multibeam bathymetry and seafloor backscatter data collected by an autonomous underwater vehicle, together with photomosaics, video observations, and samples obtained by a remotely operated vehicle. Sites of focused fluid flow are identified by gas bubble streams rising from the seafloor while anaerobic oxidation of methane (AOM) over wider areas is indicated by the occurrence of chemosynthesis-based organisms (microbial mats, vesicomyid clams, vestimentiferan tube worms). At some sites, flakes of gas hydrate were observed in the water column during sampling. A range of carbonate structures exists at these sites: 1) flat and extensive pavements; 2) mounds with disseminated nodules or centimeter-thick crusts; 3) fractured mounds with exposed, decimeter-thick crusts; and 4) seafloor depressions lined by decimeter-thick crusts. The mineralogy and stable carbon isotopic compositions of the carbonates are consistent with anaerobic oxidation of methane from thermogenic sources, and possible near-seabed influence of gas hydrate formation and dissolution. The seafloor expressions of seepage are inferred to be controlled by the interaction of fluid flow due to carbonate precipitation and gas hydrate formation. A conceptual model for mound development is proposed in the context of the known timescales of seep-colonization and rates of carbonate precipitation: (A) the onset of hydrocarbon-rich fluid seepage through hemipelagic sediments leads to (B) the establishment of microbial mats on flat seafloor over decadal timescales and is followed by (C) the growth of pavements cemented by carbonates that seal the seafloor; over longer timescales (centuries to millennia), carbonate growth and subsurface gas hydrate formation/dissolution lead to (D) upward doming and fracturing of carbonate mounds, re-sealing and stacking of carbonates and in some cases to (E) their collapse to form seafloor depressions. Gas migration through fractures in the carbonates allows re-sealing and fuels AOM to provide habitats for chemosynthesis-based fauna. This evolutionary scenario is argued to be broadly applicable to the development of ruptured mounds and collapse features described at other seepage sites in the Mediterranean Sea and elsewhere.

Deep‐sourced gas seepage and methane‐derived carbonates in the Northern Adriatic Sea

AbstractIn the Northern Adriatic Sea, the occurrence of gas seepage and of unique rock outcrops has been widely documented. The genesis of these deposits has recently been ascribed to gas venting, leading to their classification as methane‐derived carbonates. However, the origin of seeping gas was not clearly constrained. Geophysical data collected in 2009 reveal that the gas‐enriched fluid vents are deeply rooted. In fact, the entire Plio‐Quaternary succession is characterized by widespread seismic anomalies represented by wipe‐out zones, and interpreted as gas chimneys. They commonly root at the base of the Pliocene sequence but also within the Palaeogene succession, where they appear to be associated to deep‐seated faults. We suggest that there is a structural control on chimney distribution. Chimneys originate and terminate at different stratigraphic levels; commonly they reach the seafloor, where authigenic carbonate deposits form locally. Gas analyses of some gas bubble streams just above the rock outcrops reveal that gas is composed mainly of methane. Geochemical analyses performed at four selected outcrop sites show that these deposits formed as a consequence of active gas venting. In particular, geochemical analyses indicate carbonate precipitation from microbial oxidation of methane‐rich fluids, although a straightforward correlation with the source depth of gas feeding the authigenic carbonates cannot yet be clearly defined.

Methane fluxes and carbonate deposits at a cold seep area of the Central Nile Deep Sea Fan, Eastern Mediterranean Sea

Abstract High acoustic seafloor-backscatter signals characterize hundreds of patches of methane-derived authigenic carbonates and chemosynthetic communities associated with hydrocarbon seepage on the Nile Deep Sea Fan (NDSF) in the Eastern Mediterranean Sea. During a high-resolution ship-based multibeam survey covering a ~ 225 km2 large seafloor area in the Central Province of the NDSF we identified 163 high-backscatter patches at water depths between 1500 and 1800 m, and investigated the source, composition, turnover, flux and fate of emitted hydrocarbons. Systematic Parasound single beam echosounder surveys of the water column showed hydroacoustic anomalies (flares), indicative of gas bubble streams, above 8% of the high-backscatter patches. In echosounder records flares disappeared in the water column close to the upper limit of the gas hydrate stability zone located at about 1350 m water depth due to decomposition of gas hydrate skins and subsequent gas dissolution. Visual inspection of three high-backscatter patches demonstrated that sediment cementation has led to the formation of continuous flat pavements of authigenic carbonates typically 100 to 300 m in diameter. Volume estimates, considering results from high-resolution autonomous underwater vehicle (AUV)-based multibeam mapping, were used to calculate the amount of carbonate-bound carbon stored in these slabs. Additionally, the flux of methane bubbles emitted at one high-backscatter patch was estimated (0.23 to 2.3 × 106 mol a− 1) by combined AUV flare mapping with visual observations by remotely operated vehicle (ROV). Another high-backscatter patch characterized by single carbonate pieces, which were widely distributed and interspaced with sediments inhabited by thiotrophic, chemosynthetic organisms, was investigated using in situ measurements with a benthic chamber and ex situ sediment core incubation and allowed for estimates of the methane consumption (0.1 to 1 × 106 mol a− 1) and dissolved methane flux (2 to 48 × 106 mol a− 1). Our comparison of dissolved and gaseous methane fluxes as well as methane-derived carbonate reservoirs demonstrates the need for quantitative assessment of these different methane escape routes and their interaction with the geo-, bio-, and hydrosphere at cold seeps.

Gas seeps in Lake Baikal—detection, distribution, and implications for water column mixing

Echo sounders served to locate a large number of shallow- and deepwater gas seeps at the bottom of all three basins of Lake Baikal during the years 2005 to 2008. A substantial proportion of the shallow gas seeps was located near the delta of the Selenga River, and at the Posolskii uplift. Deepwater gas seeps were recorded at the lake bed both inside and outside of areas where a bottom-simulating reflector was identified in seismic profiles. By monitoring the activity of gas emissions at the gas seeps, times of episodic gas ebullition could be distinguished from times of persistent gas bubble streams. A maximum gas flare height of more than 950 m above the bottom was recorded at the St. Petersburg mud volcano located in the central basin of Lake Baikal. Based on calculations from echo sounder data, the ascent velocity of gas bubbles reached 40 cm/s. In the area of gas seepage, there was a thick near-bottom layer, in which the gradient of water temperature was equal to the adiabatic gradient. This implies complete mixing of the water close to the lake bed, resulting from ascending gas bubbles released at seep sites. Analyses of vertical temperature profiles indicate possibly localized upwelling up to the lake surface when gas emissions are intensive.

Vodyanitskii mud volcano, Sorokin trough, Black Sea: Geological characterization and quantification of gas bubble streams

Vodyanitskii mud volcano is located at a depth of about 2070 m in the Sorokin Trough, Black sea. It is a 500-m wide and 20-m high cone surrounded by a depression, which is typical of many mud volcanoes in the Black Sea. 75 kHz sidescan sonar show different generations of mud flows that include mud breccia, authigenic carbonates, and gas hydrates that were sampled by gravity coring. The fluids that flow through or erupt with the mud are enriched in chloride (up to ∼650 mmol L −1 at ∼150-cm sediment depth) suggesting a deep source, which is similar to the fluids of the close-by Dvurechenskii mud volcano. Direct observation with the remotely operated vehicle Quest revealed gas bubbles emanating at two distinct sites at the crest of the mud volcano, which confirms earlier observations of bubble-induced hydroacoustic anomalies in echosounder records. The sediments at the main bubble emission site show a thermal anomaly with temperatures at ∼60 cm sediment depth that were 0.9 °C warmer than the bottom water. Chemical and isotopic analyses of the emanated gas revealed that it consisted primarily of methane (99.8%) and was of microbial origin ( δD-CH 4 = −170.8‰ (SMOW), δ 13C-CH 4 = −61.0‰ (V-PDB), δ 13C-C 2H 6 = −44.0‰ (V-PDB)). The gas flux was estimated using the video observations of the ROV. Assuming that the flux is constant with time, about 0.9 ± 0.5 × 10 6 mol of methane is released every year. This value is of the same order-of-magnitude as reported fluxes of dissolved methane released with pore water at other mud volcanoes. This suggests that bubble emanation is a significant pathway transporting methane from the sediments into the water column.

Heat transfer in a reciprocating plate column

AbstractA pilot‐scale (5.08 cm internal diameter) reciprocating plate column has been modified by the insertion of a brass test section for heat transfer measurements. Heat is supplied to liquid (water or a glucose solution) in the column from an electrical heating tape wound round the brass section, the walls of which contain thermocouples. Reciprocation of the plates in the column results in up to a seven‐fold improvement In heat transfer coefficient, to single phase liquids. Conditions are turbulent with oscillatory Reynolds numbers up to 20000. The effect of plate reciprocation is much less pronounced when the liquids are agitated by a stream of gas bubbles. The single‐phase heat transfer coefficients have been correlated for 5 different types of plates using approaches already available in the literature for turbulent systems in steady flow. The best‐fit oscillatory flow correlation differs slightly from the existing correlations for steady flow.

Apparatus for uniform cleaning of wafers using megasonic energy

Apparatus and method for cleaning/etching the surface of an article with sonic energy in the megahertz range which employ an anti-reflection mechanism within a recirculation tank. A tank having at least one side wall and a bottom structure holds a cleaning/etching liquid and a megasonic transducer is associated with the tank for projecting megasonic energy into the liquid. The anti-reflection mechanism is disposed within the tank in close association with the at least one sidewall or bottom structure of the tank to thereby minimize reflection of megasonic energy from the associated surface. Preferably, the megasonic transducer is associated with a first tank sidewall which opposes a second tank sidewall, and the anti-reflection mechanism is disposed adjacent the second tank sidewall. By way of example, the anti-reflection mechanism can comprise a stream of gas bubbles, a plurality of anechoic structures, or a combination of both gas bubbles and anechoic structures.

Mass‐transfer effects of bubble streams rising near vertical electrodes

AbstractMass‐transfer enhancement by a stream of bubbles rising near a planar, vertical surface is resolved spatially and temporally using a micromosaic electrode. A stream of gas bubbles is generated electrolytically, either at a segment directly below and in the plane of the monitoring electrodes, or at a wire tip that can be positioned inside or outside the mass‐transfer boundary layer. The mass‐transfer enhancement resulting from bubbles rising within the mass‐transfer boundary layer is found to be strong and localized, in agreement with trends predicted by a surface‐renewal model. Mass transfer resulting from bubbles rising outside the boundary layer is found to receive a steady, laminar enhancement, correlating well with predictions from an idealization of the bubble stream entraining a cylinder of liquid.

Trace elements in the geogas and their relation to bedrock composition

The paper describes an investigation of a transport mechanism in the ground which has the capacity of lifting trace amounts of different elements from the bedrock to the ground surface. The transported matter is guided by a funnel system towards a thin membrane on which it is collected. The matter on the membranes is analysed with the PIXE method. The transport may be brought about by a very weak stream of gas bubbles which passes upwards through cracks and fissures in the bedrock. Remarkable similarities are found between the occurrence of elements on the membranes and the composition of a mineralization straight below the points of collection. The mechanism seems to have the power of revealing the existence of important base metal occurrences in the bedrock and may therefore be the basis for a new method of prospecting for concealed mineralizations.

Bubble induced heat transfer in gas fluidized beds

The influence of gas bubbles on heat transfer in gas fluidized beds has been investigated. A platinum wire has been used as a heat-transfer probe and the aggregative gas fluidized bed has been simplified by generating a single continuous stream of gas bubbles into an incipiently fluidized bed. It has been found that in the case of aggregative gas fluidized beds of small particles operating below the radiative temperature level, transient conduction into the emulsion phase is responsible for at least 90% of heat transfer and that the remainder is contributed by the superimposed gas convection. A theoretical model of the bubble induced heat transfer has been developed. Finally, experimental justification for the concept of the property boundary layer introduced in [2] is presented.

Liquid Jet Pumped by Rising Gas Bubbles

From observations of a stream of gas bubbles rising through a liquid, a two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. The bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped upward consists of the bubble wakes and the liquid brought into the jet region by turbulent entrainment. The expansion of the gas bubbles as they rise through the liquid is taken into account. The continuity and momentum equations are solved numerically for an axisymmetric air jet submerged in water. Water pumping rates are obtained as a function of air flow rate and depth of submergence. Comparisons are made with limited experimental information in the literature.

Reduction Potentials of Organic Substances by the Lead Peroxide Electrode.

It has been pointed out frequently that the potentials measured in a solution of pure oxidant or pure reductant have a questionable meaning. Moreover such potentials are difficult to measure because they fall in a region of a curve approaching the potential axis asymptotically, and thus a slight change of conditions in the solution causes a wide fluctuation of potential. In such a solution an “inert” electrode, being unpoised, is subject to further fluctuation due to its own surface activity. The same considerations obviously apply to solutions of those reductants which tend to transform irreversibly into products not active at an electrode, such as most organic compounds. Various schemes have been proposed for the measurement of such potentials, which depend in general upon the addition of some other component which poises the system. It occurred to us that an oxidizing electrode might in itself have a poising action on an otherwise irreversible system. We have tried manganese dioxide and lead peroxide electrodes. In the following we report preliminary determinations with lead peroxide electrode on solutions of certain organic reductants. The electrodes were prepared by plating out lead peroxide on platinum electrodes, made anodal in a solution of lead nitrate acidified with eight per cent nitric acid, under voltage sufficient to cause evolution of a fine stream of gas bubbles. These electrodes read in buffer solutions far in the the oxygen overvoltage region. On long standing they approach the oxygen electrode potential, but still read sluggishly in a reducing solution. If placed in a solution of a reducer until equilibrated, then washed in buffer until they again approach the oxygen electrode potential, when next placed in a reducing solution, equilibrium is attained very promptly.