Bubble Displacement Research Articles

Effect of root‐end resection and root‐end filling on apical leakage in the presence of core‐carrier root canal obturation

To evaluate the apical seal of canals filled with a core-carrier obturator following root-end resection with and without a root-end filling. Thirty single-rooted human teeth with single canals were used. Root canal treatment was performed and canals filled with a core-carrier obturation technique. The teeth were then randomly assigned to three groups (n = 10). In the first group root canal filling only was performed. After orthograde filling, the teeth of the second group were resected apically, perpendicular to the major axis of the root. In the third group after apical resection, a root-end cavity was prepared using ultrasonic diamond retrotips and the cavities filled with Super-EBA cement. During a period of 3 h and with a headspace pressure of 0.12 atm, methylene-blue solution was forced through a tube that was connected to the apical end of each tooth specimen. The coronal end of the tooth was connected to a capillary tube containing an air bubble. Leakage was evaluated by observing the distal displacement of the air bubble. The roots were then sectioned along their long axis. Using a stereomicroscope, linear dye infiltration at the dentine-cement interface was determined. Kruskal-Wallis and Mann-Whitney tests were used to compare the three groups. Linear dye infiltration was significantly greater in root canals filled with the core-carrier obturators and resected apically (0.9 +/- 0.9 mm) when compared with those that had root-end fillings (0.2 +/- 0.4 mm). Air bubble displacement was not observed. Root-end filling improves the sealing of roots with core-carrier obturation following root-end resection.

Microvascular gas embolization clearance following perfluorocarbon administration

Effective treatment of vascular gas embolism may be possible with emulsified fluorocarbon compounds. We tested the hypothesis that a fluorocarbon emulsion delivered before gas embolization would enhance bubble motion through the vasculature, favoring more rapid clearance. Air microbubbles were injected into the rat cremaster microcirculation in six groups of rats receiving Perftoran, an emulsified fluorocarbon, or saline immediately before, 2 h before, or after bubble injection. Embolism dimensions and dynamics were observed by using intravital microscopy. Surface area at lodging was equal between groups. Bubbles having smaller volume embolized smaller diameter vessels in the Perftoran pretreatment groups. A higher incidence of bubble dislodgement and larger distal displacement occurred in these two groups, with a 36% decrease in the time to bubble clearance and restoration of blood flow. Intravascular emulsified fluorocarbon administration before gas embolization affected initial bubble conformation, increased bubble dislodgement, and resulted in bubble displacement further into the periphery of the microcirculation. These dynamic events did not occur if embolization preceded fluorocarbon administration.

Effects of physical environment on induction time of air–bitumen attachment

Induction time is a key parameter in flotation. It is defined as the time needed for attachment of an air bubble with particles or a layer of bitumen when they are in contact. It has been reported that induction time is a function of many physical parameters. However, no systematic experimental study of these parameters has been reported. A refined induction timer was built to investigate the effects of physical parameters on induction time. The induction time, measured by moving an air bubble toward and then away from a silica particle bed, was found to be affected by the initial gap between the air bubble and the particle bed, the displacement and size of the air bubble, and the velocities of the air bubble approach to and retraction from the particle bed. Air bubble–bitumen attachment in different solutions (de-ionized water, clear process water and process water containing 0.5% fine solids) with or without calcium ion addition was studied at different temperatures. The results showed that induction time decreased with increasing temperature. The induction time was lowest in de-ionized water and highest in process water containing 0.5% fine solids with 50 ppm calcium ions.

Electrokinetic displacement of air bubbles in microchannels

Displacement of air bubbles in a circular capillary by electrokinetic flow is shown to be possible when the film flow around the bubble is less than the bulk flow behind it. In our experiments, film flow reduction is achieved by a surfactant-endowed interfacial double layer with an opposite charge from the wall double layer. Increase in the film conductivity relative to the bulk due to expansion of the double layers at low electrolyte concentrations decreases the field strength in the film and further reduces film flow. Within a large window in the total ionic concentration Ct, these mechanisms conspire to induce fast bubble motion. The speed of short bubbles (about the same length as the capillary diameter) can exceed the electro-osmotic velocity of liquid without bubble and can be achieved with a low voltage drop. Both mechanisms disappear at high Ct with thin double layers and very low values of zeta potentials. Since the capillary and interfacial zeta potentials at low concentrations scale as log Ct−1 and log Ct−1/3, respectively, film flow resumes and bubble velocity vanishes in that limit despite a higher relative film conductivity. The bubble velocity within the above concentration window is captured with a matched asymptotic Bretherton analysis which yields the proper scaling with respect to a large number of experimental parameters.

Bubble collapse and liquid jet formation in non-Newtonian liquids : Brown, S.W.J., Williams, P.R., University of Wales Swansea, Swansea, UK in AIChE journal, vol 45, issue 12, 1999

Air guns can be used for seabed resource exploration, shock testing of naval vessels, polar ice breaking, etc. The study of air-gun bubble pulsation and near-field pressure is of great significance. In order to analyze the dynamic behavior and pressure characteristics of air gun bubble in detail and quantitatively, this study used the finite volume and volume of fluid methods to establish a compressible, three-dimensional air-gun bubble model in OpenFOAM (Open Field Operation and Manipulation). The characteristics of air-gun bubble pulsation and the surrounding flow-field pressures produced using various opening areas and forms were investigated. The maximum horizontal bubble displacement, main primary pulse, and bubble pulse were analyzed quantitatively. When the air-gun opening area was small, the bubble expansion time was short and the collapse time was long. The bubble surface was mostly smooth during the first bubble pulsation cycle. The bubble was nearly spherical when at its maximum volume. When collapse was nearly complete, an annular jet formed in the annular-opening air gun bubble, and four jets were formed from the four-opening air-gun bubble. The system with the largest air-gun opening area had the largest pressure wave primary pulse.

Shell correction energy for bubble nuclei

The positioning of a bubble inside a many fermion system does not affect the volume, surface, or curvature terms in the liquid drop expansion of the total energy. Besides possible Coulomb effects, the only other contribution to the ground state energy of such a system arises from shell effects. We show that the potential energy surface is a rather shallow function of the displacement of the bubble from the center and in most cases the preferential position of a bubble is off-center. Systems with bubbles are expected to have bands of extremely low lying collective states, corresponding to various bubble displacements.

Experimental Investigation of Taylor bubble acceleration mechanism in slug flow

Measurements of the total drag force on a stationary, solid model of a Taylor bubble placed in a downward flowing liquid stream in a vertical tube have been performed and analyzed using a one-dimensional flow model, in order to study the mechanisms responsible for acceleration of a Taylor bubble in the wake region of a preceding Taylor bubble in gas–liquid slug flow. Variations in the drag force with the solid Taylor bubble’s lateral displacement from the tube axis were determined in single and dual bubble systems. The single bubble experiments with 7.5- and 15-cm long, bullet shaped solid bubbles with axi-symmetric and deformed nose shapes showed a significant decrease in the drag force with Taylor bubble displacement from the tube axis for all bubbles. For the deformed nose bubbles, the measured drag force was significantly smaller than for the normal nose bubbles at all lateral bubble positions. In the dual bubble system, the drag force measured on a trailing bubble at the center of the pipe increased gradually with the increasing separation distance up to about two pipe diameters, while beyond this region the drag force remained essentially constant. A one-dimensional flow model was developed and used to determine the factors responsible for drag force reduction. Based on these results, acceleration of a trailing Taylor bubble in a gas–liquid slug flow has been attributed to the reduction in drag force caused by changes in the nose shape and lateral displacement of the bubble from the vertical pipe axis.

Forces interfaciales et turbulence dans les écoulements à bulles

The Eulerian-Eulerian model presented here insists on two aspects of the interaction between phases: first the turbulent correlations associated with the added mass force are taken into account in the expression of the force exerted by the liquid on the bubbles and second the Reynolds stress tensor of the continuous phase is separated into two parts, a turbulent part produced by the gradient of mean velocity and a pseudo-turbulent part induced by bubble displacements, each part is predetermined by a transport equation. The application of the model in three basic bubbly flows (grid, uniform shear and mixing layer) confirms the pertinence of the improvements proposed to ameliorate the prediction of the phase distribution in bubbly flows.

Periodic Nonlinear Bubble Motion in Aqueous Foam under Oscillating Shear Strain

The elastic response of aqueous foam to oscillating shear strain is probed by diffusing-wave spectroscopy. At low strains, the local bubble displacements are shown to be compatible with linear elastic behavior. At higher strains, a crossover to nonlinear but still fully periodic displacements is observed. To explain these results, we present a phenomenological model based on unstable bubble configurations.

Simulation d'écoulements induits par des bulles dans un liquide initialement au repos

With the aim of performing large-scale simulations of dispersed two-phase flows, we show the need to include source terms in the momentum equations of the continuous phase in order to reproduce the fluid motions induced by the presence and the displacement of bubbles or particles. We study the influence of these terms on the flow generated by a single bubble in a stagnant liquid. Then we simulate a low-void fraction flow in a liquid initially at rest and we show that cellular structures with properties close to those of buoyancy-driven flows are created.

A MONTE-CARLO SIMULATION OF GAS PHASE HYDRODYNAMICS IN BUBBLE COLUMNS

Abstract A Monte-Carlo simulation of gas hydrodynamics in bubble columns is propossd. A large number of bubbles, having a volume equal to the actual gas hold-up existing in the column, are considered. Assuming a given radial profile ofliquid velocity, simple rules of bubble displacement are then suggested. Specific rules are also considered for the entrance and exit zones of the column. The model which tracks the position ofall bubbles, enables simulations of tracer response curves along with the gas hold-up. The model has been assessed with experimental tracer responses obtained using a radioactive tracer technique. Acceptable agreement with experimental data has been found at moderate gas flow rate but deviations were observed at low gas flow rate.

Breakup of Liquid Bubbles due to Air Streams. 1st Report, Displacement and Acceleration.

This paper describes the deformation, breakup, displacement, and acceleration of liquid bubbles due to air streams. Experiments are conducted using a horizontal air-suction wind tunnel. The shattering processes of liquid bubbles are observed using a stroboscope. The breakup pattern of a liquid bubble varies with air stream velocity. In this experiment several breakup patterns are observed. Dimensionless time variations of dimensionless displacement, and dimensionless accelerations of liquid bubbles are investigated in detail. The dimensionless displacements are approximately proportional to the square of dimensionless time. At the initial stage, liquid bubbles have unsteady acceleration which is greater than steady acceleration.

Statistical mechanics of magnetic bubble arrays. II. Observations of two-dimensional melting.

We report observations of a continuous hexatic-to-liquid melting transition as a function of density in two-dimensional magnetic bubble arrays in garnet films. Bubble arrays can be directly viewed and their motion recorded. The hexatic with orientational order undergoes a phase transition to form an isotropic liquid when dislocations unbind into disclinations. Melting occurs via the formation of progressively larger transient defect clusters that gradually percolate into one another, and eventually span the system destroying orientational order. Observations made in a linear magnetic-field gradient indicate that the transition is continuous. Defect dynamics, concentrations, and mobilities characterize the melting process. At the transition bubble motion goes from constrained in the hexatic to diffusive in the liquid. The transition is described well by a phenomenological criterion: melting occurs when the root mean square of the difference between displacements of adjacent bubbles is \ensuremath{\sim}10% of the average lattice spacing. At higher bubble densities, away from the transition, we observe a hexatic glass characterized by extended orientational order, very few immobile dislocations, and short-range translational order limited by substrate roughness.

Formation of open and elongating transcription complexes by RNA polymerase III

The Saccharomyces cerevisiae transcription factors (TF) IIIB and IIIC assemble onto their respective DNA-binding sites on the SUP4 tRNA Tyr gene at 0 °C. RNA polymerase III specifically associates at 0 °C with this TFIIIC-TFIIIB-DNA complex to form a stable “closed” promoter complex in which the DNA surrounding the transcriptional start retains its duplex form. Promoter “opening” is a temperature-dependent and readily reversible process that involves up to 22 unwound base-pairs of DNA, and can be followed by analyzing the hyperreactivity of thymine to KMnO 4 oxidation. This promoter opening increases progressively from 10 °C to 40 °C, with at least two regions within the transcription bubble appearing to melt independently. In contrast, the temperature dependence of forming an initiated transcription complex containing a 17 nucleotide nascent RNA chain displays a sharp transition between 10 °C and 15 °C. When RNA polymerase initiates transcription under conditions that limit the nascent RNA chain to less than six nucleotides, there is no displacement of the transcription bubble. These transcription complexes are distinguishable from “open” promoter complexes in their maintenance of the transcription bubble at 0 °C, and from transcription complexes with more extended (17 nucleotide) RNA chains in their sensitivity to disruption by heparin. In light of recent results by others that demonstrate a requirement for an RNA transcription factor in a Bombyx mori-based in vitro RNA polymerase III transcription system, we have searched for a comparable component in the S. cerevisiae-derived system. We show that if an RNA component is required in the yeast-derived system, it is not susceptible to inactivation by massive amounts of micrococcal nuclease, RNase A, or RNase T 1.

Microscopic mapping of subnanometric motion

The sensitivity of a microscope-based holographic system designed for mapping the motion of components of a living cell is calibrated by means of a simple procedure. Bubbles of air are allowed to drift with known velocity in a nearly horizontal, glycerine-filled capillary observed through the microscope. The ultrafine motion of the bubbles is captured interferometrically by subtractive superposition of a pair of holograms recorded a few milliseconds apart. Stationary portions of the field of view are rendered dimly in images reconstructed from the interferogram, while the brightness of moving portions varies monotonically with their displacement. Displacements as small as 1.1 nm were betrayed in the images. Analysis of the experimental conditions suggests that bubble displacements as small as 0.7 nm will become detectable once minor improvements are made in the apparatus.

The gastric bubble: roentgen observations.

The appearance of the stomach bubble provides many clues to underlying thoracoabdominal disorders. Illustrated in this article are (1) the major complications of large hiatal hernias: intrathoracic gastric volvulus and ulceration; (2) diaphragmatic abnormalities including inversion of the hemidiaphragm and intrathoracic displacement of abdominal contents because of diaphragmatic laceration or congenital herniation; (3) extrinsic displacement of the stomach bubble by splenomegaly (the occurrence of which in association with radiographic abnormalities in the chest--cardiomegaly, interstitial lung disease, mediastinal or hilar adenopathy--helps form a differential diagnosis); and (4) situs abnormalities for the analysis of which a simplified schema is presented.

Mass transfer in a single‐hole tray column

AbstractA theoretical model for deuterium exchange in the H2S/H2O system was derived to describe mass transfer in the bubble formation, bubble displacement and bubble breakup regions above a single‐hole tray in an 8 cm diameter transparent column. The model was applied to data measured at 31°C in the pressure range of 790 to 2000 kPa and in a wide range of gas and liquid flows. High speed cinematography was used to measure bubble diameters, bubble formation times and bubble contact times in the liquid, all of which are parameters in the mass transfer models.Results show that for single‐hole trays and the major part of mass transfer occurs in the upper surface of the froth where bubbles disengage from the liquid. However, when the same model is applied to pilot plant sieve trays, it is shown that the bulk of mass transfer takes place in the region where bubbles are ascending in the froth. The tray efficiencies predicted by the model agree well with measured values.

DETECTION OF GAS BUBBLE BOUNDARY MOVEMENT*

ABSTRACTHigh‐resolution seismic surveys were performed on an underground gas storage of Gaz de France at Gournay‐sur‐Aronde (Oise) in order to obtain information about gas bubble boundaries within the reservoir. For that purpose, a light seismic source Soursile and spreads with small spacing between geophone groups (10 m) and small geophone group extension (10 m or 20 m) were used. In December 1982, a line recorded on the top of the anticline structure of the gas reservoir provided an estimation of the lateral extension of the bubble based on an amplitude anomaly (dim spot) associated with reservoir seismic horizons. In order to estimate the displacement of the gas bubble within the reservoir, three lines were recorded on the southeastern part of the anticline at different time periods (April 1981 and January 1982) with different volumes of gas in the reservoir. It is assumed that a variation of gas volume introduces a seismic velocity variation and as a result a travel‐time variation for the seismic waves that pass through the reservoir. A method based on the residual time shifts observed on reflectors below the reservoir from one survey to the other was developed and implemented. This method permitted a detection of a movement gas bubble boundary between April 1981 and January 1982 which agrees with drill hole data (water level measurements).

Amorphous networks of magnetic bubbles: Statics and dynamics=an approach of 2d melting (abstract)

Direct observations and Fourier transforms of amorphous networks of magnetic bubbles in ion-implanted garnets and in pure films are shown with evidence for a short coherence size. This is interpretated on the basis of a model of interaction of bubbles via dipolar interactions where only short-range effects are considered because long-range effects are totally screened by the numerous domains included in this range. Moreover these dipolar forces which are proportional to both the magnetizations stabilize the occurrence of different radii of bubbles. These two considerations enable us to understand these amorphous networks as due to short-range interactions and random fields and thence to predict a coherence size of typically 50–300 bubbles in a hexagonal arrangement. Small rotating fields in the phase of the film do not strongly perturb the size distribution of bubbles, i.e., the transverse magnetic field distribution, but induce many local displacements of bubbles. These displacements can be coherent and thus collective if the excitation frequency is associated with a soft mode of this amorphous structure. Thus local cascades of hopping motion as well as collective modes are observed as a function of the excitation frequency. The practical soft modes are localized on the grain boundaries and lead either to a decrease of the coherence size, i.e., melting or to an increase, i.e., recrystallization. Theoretical investigations of the soft mode frequency and localization are given. Experimentally direct and Fourier transform observations as a function of frequency are recorded in a video tape.

New high sensitive micromanometer

An instrument is described where the downwards or upwards displacement of menisci under the action of a pressure differential in a U-tube arrangement is magnified by a factor of 104 or more. This is accomplished by determining the volume of manometer fluid displaced via the very precise observation of motion of an air bubble inside a horizontal capillary tube connecting the large and equal diameter vertical legs of the manometer. Means of introducing and initially placing the air bubble are described as well as the use of a long capillary spirally coiled in one plane. This plane does not need to be placed horizontally because buoyancy forces cannot influence the bubble displacement. An instrument has been built and checked for surface tension effects which proved to be negligibly small. The instrument was used to measure velocity distribution of air flowing laminarly through a tube. The agreement between data and theory is excellent.