Appearance Of Bubbles Research Articles

Evaluation of the maximum size of through pores in MFAS-type membranes found by different methods

Experiments to determine the maximum size of through pores in MFAS-type membranes (Vladipor Company) were carried out in two ways: by the “bubble-point” method according to GOST (State Standard) 50516-93 and the “crystallization-onset” method. The experimental values of the pressure difference upon the appearance of bubbles in a liquid and the temperature of the crystallization onset were obtained for membranes of different brands. It was shown that the membrane thickness influences these parameters. Repeated measurements of the maximum size of through pores were performed and showed good reproducibility of the experimental data.

Experimental study of bubbling regimes on submerged micro-orifices

The dynamic bubble behaviors on submerged micro-orifices are investigated experimentally. The orifice diameters are within the range of 0.11–0.24mm, and the range of gas flow rate is between 0.167 and 25ml/min. The experimental data were recorded using a high-speed camera, and images were analyzed with the help of MATLAB. The bubble formation processes on the submerged micro-orifices show some new and different dynamic behaviors, such as multi-bubble coalescence, and the alternate appearance of paring and single bubbles. At low Bond numbers (variation in the orifice radii), with an increase in Weber number (variation in the gas flow rate), a bubble first emerges during a single period stage followed by a multi-bubble coalescence stage. The bubble coalescence processes can be divided into five cases according to the number of coalescing bubbles. With an increase in the gas flow rate, it was found that the complete bubble detachment time and the detachment volume increase. Meanwhile, based on an analysis of the bubble aspect ratio and rising velocity, departing bubbles were shown to suffer stronger oscillations. At a higher Bond number, a bubble first appears in a single form, followed by a period of double bubble behaviors, and back to a period of single form. Finally, a bubbling regime map was constructed to describe the dynamic behaviors of bubbles under the conditions of different Weber and Bond numbers.

A biophysical vascular bubble model for devising decompression procedures.

Vascular bubble models, which present a realistic biophysical approach, hold great promise for devising suitable diver decompression procedures. Nanobubbles were found to nucleate on a flat hydrophobic surface, expanding to form bubbles after decompression. Such active hydrophobic spots (AHS) were formed from lung surfactants on the luminal aspect of ovine blood vessels. Many of the phenomena observed in these bubbling vessels correlated with those known to occur in diving. On the basis of our previous studies, which proposed a new model for the formation of arterial bubbles, we now suggest the biophysical model presented herein. There are two phases of bubble expansion after decompression. The first is an extended initiation phase, during which nanobubbles are transformed into gas micronuclei and begin to expand. The second, shorter phase is one of simple diffusion‐driven growth, the inert gas tension in the blood remaining almost constant during bubble expansion. Detachment of the bubble occurs when its buoyancy exceeds the intermembrane force. Three mechanisms underlying the appearance of arterial bubbles should be considered: patent foramen ovale, intrapulmonary arteriovenous anastomoses, and the evolution of bubbles in the distal arteries with preference for the spinal cord. Other parameters that may be quantified include age, acclimation, distribution of bubble volume, AHS, individual sensitivity, and frequency of bubble formation. We believe that the vascular bubble model we propose adheres more closely to proven physiological processes. Its predictability may therefore be higher than other models, with appropriate adjustments for decompression illness (DCI) data.

Periodicity in the occurrence of equatorial plasma bubbles derived from the C/NOFS observations in 2008–2012

AbstractThe quasi‐periodic occurrence of equatorial plasma bubbles is understood in terms of seeding mechanisms in the bottomside F region. However, no quantitative investigation has been conducted to identify how often quasi‐periodic bubbles occur. This study investigates the wave property in the bubble occurrence (or spacing between bubbles) using the measurements of the plasma density in 2008–2012 by the Planar Langmuir Probe on board the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. The wave property is investigated using the Lomb‐Scargle periodograms derived from 664 segments of series of bubbles. In the majority of segments, the spacing between bubbles is represented by the combination of several wave components. Periodic bubbles whose property is represented by a few pronounced wave components are rare events. These results indicate that the spacing between bubbles is generally irregular. The manner of bubble occurrence does not show any notable variation with longitude and season. Because a consistent wave property does not exist in the occurrence of bubbles and the appearance of bubbles in the topside is affected by many factors, the manner of bubble occurrence in satellite observations does not provide a precise diagnostic of seeding mechanisms.

Evaluación del efecto del envejecimiento del cemento asfáltico 80-100 modificado con lignina Daniella Rodríguez U, Cristian Rodríguez, Sindy R

Esta investigación presenta un análisis de los resultados obtenidos de un asfalto modificado con lignina, un polímero abundante y de fácil acceso debido a su origen natural y su bajo costo de obtención el cual se crea mediante el proceso de fotosíntesis, compone el 30% de carbono orgánico no fósil y de un cuarto a una tercera parte de la masa seca de la madera, cumple con una función fundamental que se caracteriza por dar soporte estructural, impermeabilidad y resistencia contra agentes microbiológicos y estrés oxidativo. Esto hace que se convierta en un polímero muy resistente a la degradación. Para la mezcla modificada se utilizó un asfalto 80-100, y lignina producto de un desecho industrial papelero. El método empleado para esta investigación fue a partir de los ensayos de penetración y punto de ablandamiento (anillo y bola), consideradas como pruebas funda-mentales cuando se busca producir mezclas que presenten mayor temperatura de ablandamiento y menor temperatura de fractura. Con la lignina se utilizaron 6 porcentajes distintos; 5%, 10%, 15% y 20% en 400 gramos de asfalto 80-100. La lignina fue tamizada en el tamiz de 75 µm con el fin de obtener una mezcla homogénea y evitar grumos; el tiempo de mezcla fue de 30 minutos por cada porcentaje y la temperatura se manejó en un rango de 125°C a 135°C para prevenir la aparición de burbujas de aire.

Irrational exuberance in the Chinese iron ore market?

ABSTRACTThe rapid run-ups in the Chinese iron ore market in the first half of 2016 have sparked much concern about the appearance of speculative bubbles in this market among many market analysts. Using a recently developed bubble testing procedure, we confirm that there indeed existed periods of irrational exuberance in the Chinese iron ore market. However, most of the bubble periods are short-lived, reflecting the market’s ability to quickly respond to price deviations unjustified by fundamentals. The longest bubble period occurred in mid-2014, corresponding to a period of relatively low trading volume. Using a fractional probit model, we find evidence consistent with the hypothesis that market liquidity may play a role in bubble occurrences.

Residential property prices’ modeling: evidence from selected European countries

PurposeThe purpose of this study is to contribute to the relatively narrow existing residential real estate literature by developing and validating several univariate forecasting models, to reliably anticipate future house price dynamics across several European Union (EU) countries.Design/methodology/approachThe research approach relies on the time series analysis, by using the Box–Jenkins autoregressive integrated moving average (ARIMA) methodology to explore the trends of residential property prices in selected EU countries and to obtain a snapshot of the potential signs of change to be witnessed by domestic residential markets on a short time-period. The analysis has been performed distinctly for each country in the sample, to account for country-specific past and future trends as well as similarities in their house price growth rate evolutions. The models were estimated for a broad sample of quarterly observations during 1990-2015, while the forecast horizon ranged between the third quarter of 2015 and the fourth quarter of 2016.FindingsThe findings suggested that residential property prices’ real growth rate can be modeled through the Box–Jenkins method for France, The Netherlands, Sweden and UK. The pattern of Italy’s residential property prices’ real growth rate cannot be explained by means of univariate ARIMA models, being more suited for multivariate models.Originality/valueThe article subscribes to the need for timely, high-frequency and quality data about house price trends in Europe, to increase the accuracy of forecasts and prevent the appearance of bubbles on real estate market. It compares residential property prices’ dynamics across European countries to identify housing markets with similar patterns of their prices.

Acoustic-Emission-Analysis of Dissimilar Laser-welds of Aluminium and Polyamide 6.6

A novel laser joining process for hybrid polymer-metal structures has proven a strong bond between polyamide and aluminium. This welding technique is strongly requested by the automobile producing industry for numerous applications within structure components. However, the joining quality exhibits a strong dependency on process-related variables, which highlights the need for an online inspection technique. The requirements for a chosen inspection technique are [1], [2]: 1. Showing the results on-line during the joining process; 2. Working non-destructive; 3. Working as an integral method; Being able to determine weld defects. In that case only the Acoustic Emission Analysis (AEA) as a Non-Destructive-Technique (NDT) can be used to guarantee reasonable results. During the first tests at the welding laboratory at the Laser Technology Competence Centre (LTCC) at the University of Luxembourg, AEA sensors are applied onto the surface of the test specimen which has to be welded. In this principle acoustic events, caused by welding defects, are recorded during the laser joining. The most important laser process parameters, like velocity, power and horizontal focal position of the laser spot, have been verified and evaluated by the AEA. It was observed that insufficient laser power can lead to the break of the melting bath, which is often not recognizable by non-destructive optical methods [2]. The AEA however was able to detect this lack of fusion. Using high laser power, the appearance of gas bubbles arising from the Polyamide 6.6 could be detected afterwards in a microscopic micrograph. The AEA signals related to this effect can be correlated clearly. Due to the high pressure of the gas bubbles, the aluminium weld is often interrupted, which can be traced back to the solidification of the aluminium molten mass. Due to the actual situation, the AEA is a well-working NDT online monitoring method and can be used for the correlation of acoustic events and welding defects within the mentioned joining method. Future tasks will develop some algorithms to separate the different defects by pattern recognition of the AEA signals and parameter

Patent foramen ovale in adults with sickle cell disease and stroke

Patent foramen ovale in adults with sickle cell disease and stroke

Microfluidic PVT--Saturation Pressure and Phase-Volume Measurement of Black Oils

Summary In this work, we present a small-scale pressure/volume/temperature (PVT) cell that allows for the measurement of saturation pressure and phase-volume ratio by use of only a few microliters of black-oil samples. This novel PVT measurement technique has been successfully tested on live samples at elevated pressure (86 MPa) and temperature (150°C). In the microfluidic PVT platform, the small microfluidic device performs the same function as the laboratory-scale pressurized visual PVT cell. At the heart of the microfluidic device, is a long and narrow capillary, densely packed in a serpentine shape, embedded on the device. The capillary is nearly 1 m long and has a total volume of 5 µL. The microfluidic device is fabricated with glass and silicon, which allow visual monitoring of a fluid sample at various pressures and temperatures. To acquire PVT data, the pressure in the capillary is systematically reduced to accurately detect the appearance of micron-sized gas bubbles in a sample at saturation pressure. Because of the small thermal mass of the device, the temperature of the sample can be changed rapidly, which enables the measurement of multiple saturation pressures in quick succession. Below the saturation pressure, the growing gas bubbles form a segmented gas/liquid distribution in the capillary. The lengths of the liquid and gas segments are measured in real-time with an automated image-capturing and analysis tool to determine the gas/liquid phase-volume ratio at a given pressure. Validation tests have proved this technique to be repeatable and feasible for rapid PVT measurements of black oils [gas/oil ratio (GOR) ranging from 102 to 143 m3/m3]. The results presented in this study demonstrate that the microfluidic PVT system can measure saturation pressure and phase-volume with data quality comparable to that of the conventional PVT method, however, with significantly smaller sample volume and faster turnaround. The microfluidic PVT system is demonstrated to have the potential to become a reliable and portable measurement platform.

Formation and stability of a hollow electron beam in the presence of a plasma wake field driven by an ultra-short electron bunch

A numerical investigation on the spatiotemporal evolution of an electron beam, externally injected in a plasma in the presence of a plasma wake field, is carried out. The latter is driven by an ultra-short relativistic axially-symmetric femtosecond electron bunch. We first derive a novel Poisson-like equation for the wake potential where the driving term is the ultra-short bunch density, taking suitably into account the interplay between the sharpness and high energy of the bunch. Then, we show that a channel is formed longitudinally, through the externally injected beam while experiencing the effects of the bunch-driven plasma wake field, within the context of thermal wave model. The formation of the channel seems to be a final stage of the 3D evolution of the beam. This involves the appearance of small filaments and bubbles around the longitudinal axis. The bubbles coalesce forming a relatively stable axially-symmetric hollow beam structure.

Direct observation of bubble-assisted electroluminescence in liquid xenon

Bubble formation in liquid xenon underneath a Thick Gaseous Electron Multiplier (THGEM) electrode immersed in liquid xenon was observed with a CCD camera. With voltage across the THGEM, the appearance of bubbles was correlated with that of electroluminescence signals induced by ionization electrons from alpha-particle tracks. This confirms recent indirect evidence that the observed photons are due to electroluminescence within a xenon vapor layer trapped under the electrode. The bubbles seem to emerge spontaneously due to heat flow from 300 K into the liquid, or in a controlled manner by locally boiling the liquid with resistive wires. Controlled bubble formation resulted in energy resolution of σ/E ≈ 7.5% for ∼ 6000 ionization electrons. The phenomenon could pave ways towards the conception of large-volume `local dual-phase' noble-liquid TPCs.

Optical measurements of gas bubbles in oil behind a cavitating micro-orifice flow

In hydraulic systems, it is common for air release to occur behind valves or throttles in the form of bubbles. These air bubbles can affect the behavior and the performance of these systems to a substantial extent. In the paper, gas release in a liquid flow behind an orifice is analyzed by optical methods for various operation points. The bubbles are observed with a digital camera, and a detection algorithm based on the Hough transformation is used to determine their number and size. The appearance of gas bubbles is very sensitive to the inlet and outlet pressure of the orifice. Gas bubbles are only observed if choking cavitation occurs. An empirical relationship between an adjusted cavitation number and the appearance of gas release is presented. It is assumed that the observed bubbles contain mostly air. With the applied pressure differences, up to 30 % of the dissolved air was degassed in the form of bubbles.

Dynamic cavitation and relaxation in incompressible nonlinear viscoelastic solids

Closed form analytical solutions for the dynamic expansion of a spherical void in a finite, spherically symmetric, nonlinearly viscoelastic medium are presented. We account for finite strains and application of load, both internally, at the cavity wall, and at the external surface. Hence, the present solution may apply to a wide range of known physical phenomena with examples from biomechanics, as in the appearance of cavitation bubbles due to traumatic brain injury or expansion of soft tissue due to an internal growth, to fracture initiation in soft materials and softening of seismic bearings in large scale structures. Specifically it is suggested that the present closed form analytical relations can be facilitated to measure the local viscoelastic properties of the material through controlled relaxation experiments.

Dominant flow structures in gas–liquid–solid fluidized beds

Effective time series analysis techniques in time and frequency domains were applied to characterize three‐phase fluidization under a wide range of gas and liquid velocities. The experiments were carried out in a laboratory scale fluidized bed, operated under ambient conditions. Standard deviation of pressure fluctuations successfully detected four distinct regimes, namely compacted bed, agitated bed, coalesced and discrete bubble regimes (or discrete and dispersed bubble regimes at extremely low gas velocities). A minimum in skewness and average cycle frequency and a maximum in flatness indicated a minimum deviation from larger structures of the bed. A transition between macro and finer structures occurred during agitated bed regime and accordingly, minimum liquid fluidization velocity was perceived by skewness, flatness, and average cycle frequency analyses. The results showed that at very low liquid velocities in the compacted bed regime, the power spectrum at lower frequencies slightly increased with increasing liquid velocity. This results in the consecutive appearance of single bubbles of low frequencies. With further increase in the liquid velocity at agitated bed regime the power spectrum at lower frequencies gradually decreased. At higher liquid velocities near ULmf, the peak dominant frequency is transmitted from low frequency ranges of 2 Hz to the higher frequency of about 10 Hz.

Rare Case of Triatrial Heart with Unroofed Coronary Sinus

Triatrial heart is a rare congenital abnormality, reported in 0.4% of patients with congenital heart disease [1], and in less than 0.1% of clinically diagnosed cardiopathies [2]. First described by Church in 1868, the name “cor triatriatum” was given by Borst in 1905 [3]. It involves usually the left atrium (cor triatriatum sinister) and rarely the right atrium (cor triatriatum dexter). In the pediatric population may be associated with major congenital cardiac lesions such as tetralogy of Fallot, double outlet right ventricle, coarctation of the aorta, partial anomalous pulmonary venous connection, persistent left superior vena cava with unroofed coronary sinus, ventricular septal defect, atrioventricular septal defect, and common atrioventricular canal [4]. Clinical manifestations depend upon the size of the opening in the septum and the presence of associated congenital cardiac defects. We report a case of 5 years old girl who presented with history of exertional dyspnea ,fatigue and cyanosis. Echocardiogram done showed membrane attached laterally to the junction of the left upper pulmonic vein and left atrial appendage, dividing the left atrium into 2 chambers (Figure 1). The proximal chamber receives blood from the pulmonary veins and the distal chamber contains the left atrial appendage and mitral valve with single fenestration communicating both chambers (Figure 2). Contrast echo was done in view of cyanosis with agitated saline showed early appearance of bubbles in left atrium before right atrium suggestive of unroofed coronary sinus. Left sided superior venacava (SVC) was also seen. Diagnosis of cor-triatrium sinistrum with unroofed coronary sinus and left SVC was made and surgery was advised. Diagnosis of cor triatriatum is frequently made with considerable delay due to rarity of the condition and presenting signs and symptoms that mimic other more common cardiac or pulmonary disorders. A high index of suspicion can prevent delayed diagnosis and unfavorable outcomes.

Wear Characterization of Carbon Nanotubes Reinforced Acetal Spur, Helical, Bevel and Worm Gears Using a TS Universal Test Rig

Although the applications of nanotechnologies are increasing, there remains a significant barrier between nanotechnology and machine element applications. This work aims to remove this barrier by blending carbon nanotubes (CNT) with common types of acetal polymer gears (spur, helical, bevel and worm). This was done by using adhesive oil (paraffin) during injection molding to synthesize a flange and short bars containing 0.02% CNT by weight. The flanges and short bars were machined using hobbing and milling machines to produce nanocomposite polymer gears. Some defects that surfaced in previous work, such as the appearance of bubbles and unmelted pellets during the injection process, were avoided to produce an excellent dispersion of CNT in the acetal. The wear resistances of the gears were measured by using a TS universal test rig using constant parameters for all of the gears that were fabricated. The tests were run at a speed of 1420 rpm and a torque of 4 Nm. The results showed that the wear resistances of the CNT/acetal gears were increased due to the addition of CNT, especially the helical, bevel and worm gears.

Patent Foramen Ovale in Adult Patients with Sickle Cell Disease and Stroke

Introduction: Stroke is a leading cause of death in adults with sickle cell disease (SCD), although little is known about the underlying pathophysiology or associated risk factors. A patent foramen ovale (PFO) or other intracardiac shunts are associated with ischemic stroke in children with SCD and young adults without SCD. PFOs are relatively common, with a prevalence of about 24% in the general population. Importantly, PFOs can be closed using a minimally invasive procedure, which could potentially prevent embolic strokes in individuals with SCD at risk for stroke. We therefore designed an epidemiological study to determine the prevalence of PFOs in adults with SCD and stroke.Methods: To identify SCD patients with stroke who had evidence for a PFO by echocardiagraph, we retrospectively reviewed charts from the Johns Hopkins Hospital. All adult patients (>18 years old) with the diagnosis of stroke followed in our Sickle Cell Program were included. PFO was diagnosed by conventional echocardiogram, color Doppler studies, and contrast studies with agitated saline (10 mls) through a peripheral IV or central venous catheter with and without a Valsalva maneuver (2 times each) to increase the sensitivity of detecting intracardiac shunting. The presence of bubbles in the left atrium, either spontaneously or after Valsalva, within five cardiac cycles was noted. PFOs or other intracardiac shunts were graded by the appearance of bubbles in the left atrium, including: Grade 1 (mild shunt with 1-10 bubbles), Grade 2 (moderate shunt with 10-25 bubbles and a distinct portion filling the left atrium), and Grade 3 (substantial shunt with >25 bubbles and complete filling of the left atrium). Brain MRI/MRAs were classified by stroke subtype and severity of cerebral vasculopathy. Age at the time of the study and stroke, gender, hemoglobinopathy, presence of a peripheral deep venous thrombosis (DVT), and evidence for other stroke risk factors (moyamoya or cerebral aneurysms) were ascertained by chart review. The study was approved by the IRB at our institution.Results: From this group of 65 adult patients with a sickling hemoglobinopathy (hemoglobin SS, SC, or S beta thalassemia) and stroke, we identified 15 patients who underwent an evaluation for a PFO or other intracardiac shunt (Table 1). The prevalence of PFO or other intracardiac shunt in these adults with SCD and a history of stroke was 40% (6/15). Of these 6 patients with SCD, PFO and stroke, 1 had hemoglobin SC and 5 had hemoglobin SS. Three of the PFOs were Grade 1 and 3 were Grade 3. Three patients with PFO and stroke also had a DVT at the time of the stroke; 3 patients with PFO and stroke also had Moyamoya.Conclusions: The high prevalence of PFOs in adults with SCD and stroke compared to the prevalence of PFOs in the general population suggest that PFOs could be a risk factor for stroke in this population. These findings also underscore the urgent need for further research to establish the role of PFOs in stroke in adults with SCD because PFOs can be closed with a minimally invasive procedure. DisclosuresNaik:NHLBI: Research Funding.

INTERACTIONS BY EXCHANGE OF VOLUME BETWEEN TWO SPHERICAL BUBBLES

In this paper, by using the system potential of two bubbles and with a special interest in the interaction by exchange of volume and without exchange of mass, a system of equations governing the evolution of two bubbles is proposed. This two-bubble model shows terms that do not appear in the models of interaction between bubbles. The two-bubble model is compared with the modified Rayleigh–Plesset equation and a validation with the experimental study of Ohl [2002] is presented. The numerical results show that, on one hand, the development of small nearby bubbles can slow down the evolution of the biggest local one, while their disappearance can favor its growing. Furthermore, in the case of two bubbles in particular, the small bubble exchanges volume with the big one during their evolutions. On the other hand, contrary to the modified Rayleigh–Plesset model, the two-bubble model predicts appearance and disappearance of small bubbles in the neighborhood of the big bubble as it is observed in the experimental study of Ohl [2002]. The present findings show in particular that the interaction by exchange of volume can be very important in the cavitation born phase and it is necessary to take into account the interaction between bubbles as well as the disappearance of small ones on the evolution of the biggest local bubble. Also, this two-bubble model predicts an exchange of volume between both bubbles equal to zero when they are perfectly identical.

Biochemical characterization and role of the proteasome in the oxidative stress response of adult Schistosoma mansoni worms.

The trematode Schistosoma mansoni, an important parasite of humans, is the principle agent of the disease schistosomiasis. In the human host, one of the most important stress factors of this parasite is the oxidative stress generated by both the metabolism of the worm and the immune system of the host. The proteasomal system is responsible for protein homeostasis during oxidative stress. The 26S proteasome is a multicatalytic protease formed by two compartments, a 20S core and regulatory particle 19S, and controls the degradation of intracellular proteins, hence regulating many cellular processes. In the present report, we describe the biochemical characterization and role of the 20S proteasome in the response of adult S. mansoni worms exposed to hydrogen peroxide. Characterization of the response to the oxidative stress included the evaluation of viability, egg production, mortality, tegument integrity, and both expression and activity of proteasome. We observed decreases in viability, egg production as well as 100% mortality at the higher concentrations of hydrogen peroxide tested. The main changes observed in the tegument of adult worms were peeling as well as the appearance of bubbles and a decrease of spines on the tubercles. Furthermore, there were increases in 26S activity to the same extent as 20S proteasome activity, although there was increase of 20S proteasome content, suggesting that degradation of protein oxidized in adult worms is due to the 20S proteasome. It was demonstrated that adult S. mansoni worms are sensitive to oxidative stress, and that a variety of processes in this parasite are altered under this condition. The work contributes to a better understanding of the mechanisms employed by S. mansoni to survive under oxidative stress.