Presence Of Air Bubbles Research Articles

Chronoamperometric flow-cell designed to be unaffected by air bubbles

In this paper, we present a new design for a chronoamperometric flow cell in which air bubbles do not interfere with the control of potential between the working and reference electrodes. The flow-through dual-detection cell consists of two independent parts: an upper compartment containing a quiescent supporting electrolyte solution and a channel that operates under hydrodynamically controlled conditions. In this system, the working and counter electrodes can be placed directly in contact with both compartments, whereas the reference electrode can be assembled to be either isolated or in contact with the flowing stream channel. The design ensures that the potential applied to the working electrode (controlled in the upper compartment) is similar to the potential applied in the flowing channel. The performance of the proposed flow cell in generating accurate results, even in the presence of air bubbles, was evaluated through successive air-analyte-air injections. In both series where the analyte was introduced, suitable reproducibility was achieved. The robustness of the design was definitively proven by performing a series of measurements in analytical applications for the determination of hydrogen peroxide in antiseptic samples, yielding very satisfactory results.

Impact of Air Bubbles on the Saltiness Perception of NaCl-Loaded Oleogel-Stabilized Water-in-Oil Emulsions.

Reducing salt intake without affecting the saltiness perception remains a great challenge for the food industry. Herein, the demulsification of water droplets and air bubbles was controlled to modulate the release of sodium from oleogel-stabilized water-in-oil emulsions (OGEs) stabilized by monoglyceride crystals. The effect of monoglycerides with carbon chain length (glycerol monolaurate-GML, glyceryl monostearate-GMS, and glycerol monopalmitate-GMP) and homogenization methods (hand-shaking or high-speed blender) on sodium release and saltiness was investigated by in vitro and in vivo oral processing tests. Milky-white stable emulsions were formed with both water droplets and air bubbles dispersing in the oil phase, regardless of the selected homogenization methods. Air bubbles were more unstable than water droplets during oral digestion. GML OGEs with more and larger air bubbles and the lowest hardness exhibited the highest sodium release rate and the strongest saltiness, independent of homogenization methods. The balance between air bubbles and water droplets in the GMS and GMP OGEs caused slower sodium release and lower saltiness. Overall, the presence of air bubbles in NaCl-loaded W/O oleogel-based emulsions was shown to have important implications for tailoring their sodium release and saltiness.

The effect of freeze-thaw cycles and sulfuric acid attack separately on the compressive strength and microstructure of 3D-printed air-entrained concrete

3D-printed concrete (3DPC) is a promising technique for constructing structures and intricate designs. To ensure the successful performance of these structures throughout their service life, it is essential to understand their long-term properties and durability. While the use of air-entraining additives can enhance the durability of concrete against freeze-thaw cycles, investigating their impact on other properties is crucial. This study examines the effect of freeze-thaw cycles and sulfuric acid attack on the durability of 3D-printed concrete containing air-entraining additives. The results indicate that, in addition to improving resistance to freeze-thaw cycles, air-entraining additives also increases resistance to sulfuric acid attack. The drop in compressive strength of the samples containing air-entrained additive (0.08–0.12 % AEA) is 1.4–5.3 % less than the control samples against the freezing and thawing cycles. Examining the mechanisms of action of these invasive agents also shows this. Creating intentional voids to reduce the internal pressure of water expansion during freezing and reducing the number and width of possible microcracks are the dominant mechanisms of air-entraining additives against freeze-thaw cycles. Besides, their performance mechanisms during acid attacks are somewhat similar. Analysis of elements created in the matrix of the samples after acid attack indicates a decrease in calcium concentration and an increase in silica concentration. Among the observed reactions, the second reaction prevails, leading to the breakdown of the C-S-H structure into gypsum and silica hydroxide. This phenomenon is associated with changes in acid concentration. However, the presence of air bubbles causes surplus plate-like Calcium hydroxide crystals resulting from the elevated cement content in printed mixes to form within these bubbles, making them susceptible to damage and fracture during freeze-thaw and acid attacks.

A rare case of hepatic portal venous gas (HPVG) diagnosed as emphysematous cystitis in an elderly diabetic dialysis patient.

Hepatic portal venous gas (HPVG) is the presence of air bubbles in the portal vein and its branches. Traditionally it was considered a lethal condition because the main etiology was bowel ischemia. However, with the extensive use of diagnostic tools, it became clear that the causes of this condition are diverse and may include, but are not limited to, bowel necrosis. Here, we present a rare case of HPVG in an elderly dialysis patient with diabetes mellitus, initially diagnosed by ultrasound and CT scan. Our patient experienced abdominal pain, dysuria, oliguria, and other urinary symptoms starting three weeks prior. After considering all diagnostic tools and correlating them with the patient's history, clinical findings, and follow-up, the underlying cause of the HPVG was determined to be emphysematous cystitis. We concluded that the presence of HPVG in the initial screening test should prompt a comprehensive investigation to determine the cause, as a rare condition like emphysematous cystitis can result in HPVG.

Magnetic treatment as a suppressive method for CaCO3 scale deposition in hard waters in the presence of air bubbles

Calcium carbonate (CaCO3) scale deposition in hard water is a common problem affecting the performance and efficiency of various industrial applications such as water heating systems and pipelines. The aim of this study was to investigate the effectiveness of magnetic treatment as a suppressive method for CaCO3 scale deposition in hard water in the presence of air bubbles. A series of experiments were carried out using a laboratory-scale setup. The different CaCO3 concentrations (100 mg/L, 500 mg/L and 1000 mg/L) were considered. The hard water samples according to the various water circulation times (10, 20 and 30 min) were pumped with the flow rate of 50 L/h and passed through the region of the magnetic lines and air bubbles. A neodymium magnet (NdFeB-NB12) with a non-uniform magnetic flux density of 0.2 T on the inner walls and 0.05 T at the center was used. The CaCO3 particles deposition rate was measured using turbidity amount. The results demonstrated that the magnetic treatment significantly reduced CaCO3 deposition in hard waters in the presence in air bubbles. Turbidity changed from 0.3 NTU to 0.65 NTU at the CaCO3 concentration of 100 mg/L. It changed from 0.5 NTU to 2.25 NTU at the CaCO3 concentration 500 mg/L. Moreover, in CaCO3 concentration 1000 mg/L turbidity altered from 0.8 NTU to 3 NTU over circulation time 30 min. The simultaneous presence of magnetic fields and air bubbles reduced the amount of CaCO3 scale deposition and increased the nucleation in the bulk of the water. Aeration-based magnetic treatment is a promising alternative to chemical-based methods and an eco-friendly approach for hard waters treatment.

Fluid and Bubble Flow Detach Adherent Cancer Cells to Form Spheroids on a Random Positioning Machine.

In preparing space and microgravity experiments, the utilization of ground-based facilities is common for initial experiments and feasibility studies. One approach to simulating microgravity conditions on Earth is to employ a random positioning machine (RPM) as a rotary bioreactor. Combined with a suitable low-mass model system, such as cell cultures, these devices simulating microgravity have been shown to produce results similar to those obtained in a space experiment under real microgravity conditions. One of these effects observed under real and simulated microgravity is the formation of spheroids from 2D adherent cancer cell cultures. Since real microgravity cannot be generated in a laboratory on Earth, we aimed to determine which forces lead to the detachment of individual FTC-133 thyroid cancer cells and the formation of tumor spheroids during culture with exposure to random positioning modes. To this end, we subdivided the RPM motion into different static and dynamic orientations of cell culture flasks. We focused on the molecular activation of the mechanosignaling pathways previously associated with spheroid formation in microgravity. Our results suggest that RPM-induced spheroid formation is a two-step process. First, the cells need to be detached, induced by the cell culture flask's rotation and the subsequent fluid flow, as well as the presence of air bubbles. Once the cells are detached and in suspension, random positioning prevents sedimentation, allowing 3D aggregates to form. In a comparative shear stress experiment using defined fluid flow paradigms, transcriptional responses were triggered comparable to exposure of FTC-133 cells to the RPM. In summary, the RPM serves as a simulator of microgravity by randomizing the impact of Earth's gravity vector especially for suspension (i.e., detached) cells. Simultaneously, it simulates physiological shear forces on the adherent cell layer. The RPM thus offers a unique combination of environmental conditions for in vitro cancer research.

Polarization Multiplexing Based UOWC Systems Under Bubble Turbulence

High-speed and turbulence-tolerant transmission links are required to meet the growing demand for underwater optical wireless communication (UOWC). However, most previous works were implemented in statically simulated underwater channels with uniform temperature and salinity gradients irrespective of bubble motion. This paper presents an experimental demonstration of a polarization multiplexing (PolMux) based UOWC system considering bubble-induced turbulence. A theoretical transmission model is built and experiments are carried out to investigate the impact of bubble turbulence on PolMux transmission. The general rules of bubble impairments are summarized by manipulating different bubble flow rates, positions and bubble-effected region thicknesses. Moreover, to mitigate these effects, subchannel pairwise coding is implemented to address the subchannel signal-to-noise-ratio (SNR) imbalance issue, and subcarrier pairwise coding is utilized to overcome the subcarrier SNR imbalance, reaching a sum data rate of 8.58 Gbps. This work evaluates the performance of PolMux-UOWC links in the presence of air bubbles and demonstrates the feasibility of pairwise coding to achieve high-speed transmission in UOWC systems with bubble turbulence.

Effect of air bubbles on the membrane filtration of rhodamine B.

Effect of air bubbles on the membrane filtration of a basic dye, rhodamine B (RB), using a hydrophilic PTFE membrane filter (pore size: 0.20μm) was studied. The air bubbles were generated by vigorously mixing the aqueous solution containing 0.05% (v/v) of 1-butanol with a shaft generator of a homogenizer. RB being far smaller than the pore size of the membrane filter could not be rejected without air bubbles, but it was rejected by the membrane filter in the presence of air bubbles. The rejection ratio increased with increasing the rotation speed of the shaft generator because of the increase in the amount of air bubbles and therefore the increase in the surface area of air bubbles for the adsorption of RB. On the other hand, another basic dye, methylene blue (MB), was negligibly rejected in the same condition. Dynamic surface tension measurement of aqueous solutions containing different amounts of dye indicated that RB strongly adsorbed to the air-water interface, while MB hardly adsorbed. The results obtained in the present study strongly suggest the potential usefulness of air bubbles for the selective microfiltration of dissolved organic molecules or ions.

Efficacy of cyanoacrylate adhesive as a mounting medium for soft tissue sections as an alternative to Kirkpatrick and Lendrum's DPX

Introduction: Mounting is the final stage in histologically preparing a slide and creates a permanent the bond between the coverslip and the slide, preventing breakage, air drying artefacts, and stain fading. Materials & methods: In this study, fifty slides were prepared, twenty-five of which were mounted using DPX and twenty five using cyanoacrylate adhesive. The slides were assessed for clarity of nuclear and cytoplasmic details, adhesion between coverslip and slide, and the presence of air bubbles by two blinded observers. Results: The results showed that adhesion between coverslip and slide was better when mounted with cyanoacrylate adhesive, but better clarity of nuclear and cytoplasmic details and minimal air bubble entrapment was seen when tissue sections were mounted using DPX. Conclusion: Therefore, the use of cyanoacrylate adhesive cannot be an alternative to DPX for mounting soft tissue sections.

On the HARQ performance in underwater optical wireless communication systems with the presence of air bubbles

On the HARQ performance in underwater optical wireless communication systems with the presence of air bubbles

Comprehensive experimental and statistical analysis of the effects of salinity gradient, temperature gradient, air bubbles on the performance of underwater wireless optical communication link

Salinity gradients (SGs), temperature gradients (TGs), and different-sized air bubbles affect the optical signal propagating in the UWOC link. These effects contribute to beam wandering, spot dancing, and intensity fluctuations in the received optical signal. In this paper, experimental analysis has been carried out to estimate the effect of SG, TG and air bubbles on the underwater optical signal. The beam wandering, mean and variance deviation, displacement of weighted centroid, the statistical distribution of received intensities and link outage probability have been estimated in this work. It has been found that the beam wandering effects follow a Gaussian mixture model (GMM). It is also observed that in the presence of air bubbles in the SG, the chances of link outage increase from 48% to 80% and it increases from 7% to 28% in the TG conditions. Furthermore, the experimental and theoretical modelled outage probabilities are in close agreement.

Performance of Vertical Underwater Wireless Optical Communications With Cascaded Layered Modeling

This paper investigates the performance of vertical underwater wireless optical communication (UWOC) systems in the presence of air bubbles and temperature gradients. We consider a generalized UWOC channel model that contains <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N$</tex-math></inline-formula> layers, each having the same distribution but with different parameters to consider the vertically inhomogeneous nature of the underwater environment. To capture the effects of air bubbles and temperature gradients on channel statistics, we model each layer with a mixture exponential-generalized Gamma distribution. A closed-form probability density function (PDF) is presented for the end-to-end signal-to-noise ratio. Based on the PDF, we derive the average bit-error-rate (BER) and the ergodic capacity. Moreover, we provide asymptotic BER and ergodic capacity results in simple forms. The performance and behavior of vertical UWOC systems are thoroughly analyzed, and all the derived expressions are verified via Monte Carlo simulations.

Intravenous Infusion Monitoring and Flow Control System Equipped with Automatic Air Bubble Detection

In clinical care, intravenous infusion is one of the best ways for continuous drug delivery or clinical therapy. In most medical institutions, the workload of nurses and patient care increases due to fluctuating populations. This causes an increase in the work intensity of medical personnel. If the infusion is not monitored properly, it will lead to a medical accident. The problem is also affected due to the lack of economical and automatic infusion monitoring devices. In this case, it is proposed to design an automatic infusion control instrumentation that can detect the presence of air bubbles in the infusion to prevent air bubbles from entering the body and detect the rate of infusion flow. The proposed device is equipped with Thin Film Transistor technology (TFT) which functions to display and enter information about the condition of the intravenous infusion and a buzzer as a reminder alarm when an undesirable condition occurs. System accuracy and precision are verified for all flow rates. The results of the drops per minute test show accuracy with an error percentage of less than 2% within 1 minute. The device can detect the presence of air bubbles at high speed for response times below 20 ms and reduce the possibility of air bubbles escaping in the infusion hose according to the system test results that have been carried out. In the evaluation using target 20 drops per minute the infusion flow rate changes stably according to the angular movement of the servo motor. So it is hoped that the proposed system can help officers to monitor the condition of infusion and reduce the work intensity of medical workers.

Optimization and Validation of a Custom-Designed Perfusion Bioreactor for Bone Tissue Engineering: Flow Assessment and Optimal Culture Environmental Conditions.

Various perfusion bioreactor systems have been designed to improve cell culture with three-dimensional porous scaffolds, and there is some evidence that fluid force improves the osteogenic commitment of the progenitors. However, because of the unique design concept and operational configuration of each study, the experimental setups of perfusion bioreactor systems are not always compatible with other systems. To reconcile results from different systems, the thorough optimization and validation of experimental configuration are required in each system. In this study, optimal experimental conditions for a perfusion bioreactor were explored in three steps. First, an in silico modeling was performed using a scaffold geometry obtained by microCT and an expedient geometry parameterized with porosity and permeability to assess the accuracy of calculated fluid shear stress and computational time. Then, environmental factors for cell culture were optimized, including the volume of the medium, bubble suppression, and medium evaporation. Further, by combining the findings, it was possible to determine the optimal flow rate at which cell growth was supported while osteogenic differentiation was triggered. Here, we demonstrated that fluid shear stress up to 15 mPa was sufficient to induce osteogenesis, but cell growth was severely impacted by the volume of perfused medium, the presence of air bubbles, and medium evaporation, all of which are common concerns in perfusion bioreactor systems. This study emphasizes the necessity of optimization of experimental variables, which may often be underreported or overlooked, and indicates steps which can be taken to address issues common to perfusion bioreactors for bone tissue engineering.

The clinical management of peripancreatic fluid collection after distal pancreatectomy.

Peripancreatic fluid collection (PFC) is a frequent radiological finding on postoperative computed tomography (CT) after distal pancreatectomy (DP). We evaluated the risk factors for drainage of PFC after DP to clarify the optimal management of PFC. This study included 85 patients who underwent elective DP between January 2010 and December 2020. PFC was defined as an area of fluid located at the pancreatic resection margin on postoperative routine CT on approximately postoperative day 7 (first CT). We retrospectively investigated the relationship between clinical variables, including CT findings and PFC drainage. Drainage was performed in 19 patients (22.4%). Drainage for PFC was significantly associated with a longer postoperative hospital stay, higher PFC volume, presence of air bubbles, and higher white blood cell (WBC) count at the time of the first CT. According to the multivariate analyses, a PFC volume ≥ 60mL and WBC count ≥ 12,400/μL on the day of the first CT were independent risk factors for PFC drainage after DP. The combination of these 2 factors showed 73.7% sensitivity and 90.9% specificity. The PFC volume and WBC count at the first CT were significantly associated with PFC drainage and may help determine the appropriate treatment.

Treatment of sinus membrane perforations during sinus lift surgeries using leukocyte and platelet-rich fibrin: A report of three cases

Schneiderian membrane (SM) perforation is the most frequent intraoperative complication during sinus lifts, which can lead to implant failure or delayed implant treatment. This article aims to show the results of using leukocyte and platelet-rich fibrin (L-PRF) in the treatment of perforations occurring during sinus lifts with a lateral window approach. Three patients (n = 5 implants) with a mean ± SD age of 57.67 ± 12.12 years were included, in whom perforations of the SM of 3-5 mm and >5 mm occurred. The mean ± SD preoperative bone height was 4.42 ± 2.96 and, at 6 months it was 9.58 ± 2.41 (P < 0.05). All implants had a 100% survival rate at 6-24 months. At the split-mouth, the mean ± SD baseline height was 5.05 ± 2.99 mm in repaired SM versus 2.92 ± 1.01 in those without any complications (P > 0.05). At 6 months, mean ± SD gains were 10.09 ± 2.44 mm versus 7.73 ± 0.90 mm, respectively, (P > 0.05). L-PRF simplifies SM repair, reducing the need for high surgical experience and/or skills. Although there are no significant differences between repaired and intact SM, at the radiological level, greater bone compactness and maturation were observed in the latter, which may be associated with the presence of air bubbles caused by anaerobic bacterial activity in repaired SM. The use of L-PRF greatly simplifies the resolution of SM perforations during sinus lift surgeries, reducing treatment times, and providing predictable results. Being of autologous origin, it accelerates and enhances healing, eliminating the possibility of autoimmune rejection reactions.

The Compressive Strength Of Fly Ash Foamed Concrete With Polypropylene Fiber

Lightweight concrete is widely used for various structural applications because its lighter than normal concrete. Foamed concrete is made to produce low-density concrete by introducing air bubbles or foam into it. In the presence of air bubbles, the density of concrete only reaches 300-1700 kg/m 3 [1]. The addition of fly ash can reduce the pores that cause the entry of acids. In addition, the modulus of elasticity in the polypropylene fiber mixture prevents cracked so it can make foamed concrete more ductile than foamed concrete without fibers and can make concrete stronger. The manufacture of foamed concrete specimens was planned by the SNI Module 3 specifications [4] and was equipped with ASTM [2], [3]. The foaming agent content in foamed concrete was 0.8 % where the polypropylene fiber variations are 0 %, 0.15 %, 0.2 %, and 0.3 % with 25 % fly ash as a cement substitute. The compressive strength test results show that the addition of fibers to foamed concrete increases the compressive strength of concrete where the maximum compressive strength produced by foamed concrete with polypropylene fibers is 0.3% and the lowest compressive strength is produced by foamed concrete without fibers.

Acoustic enhancement of aerobic greywater treatment processes

Increasing the efficiency of aerobic greywater treatment is crucial to ensure that greywater recycling can be effectively implemented in individual and community households. In this work, we demonstrate that exposing greywater samples to low intensity high frequency (MHz-order) surface acoustic waves (SAWs) during the aerobic treatment process can result in increases in the total suspended solids (TSS), chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal efficiencies by 24%, 24% and 21%, respectively, over a 2 h aerobic digestion period, and up to 37% (TSS removal efficiency) over a 4 h period compared to the unexposed controls. These values are considerably higher than that typically obtained with lower frequency (kHz-order) bulk ultrasound, particularly because the SAW does not cause denaturation of bacteria in the greywater suspension unlike its low frequency counterpart. The SAW enhancement in removal efficiencies can primarily be attributed to the acoustic radiation pressure and acoustic streaming that it generates, which act to efficiently deagglomerate the bacterial flocculates in addition to promoting more uniform mixing of the suspended waste, bacteria and dissolved oxygen in the sample. Also, the results indicate that in the presence of air bubbles in the greywater, the MHz-order SAW treatment remains effective. Additionally, we show that it is possible to further increase the TSS removal efficiency by about twofold through a hybrid process. This ability to significantly accelerate the rate of aerobic digestion to achieve a given removal efficiency level highlights the potential of this novel low-cost technology for improving domestic greywater treatment.

A Direct Metal‐Free Synthetic Approach for the Efficient Production of Privileged Benzimidazoles in Water Medium under Aerobic Condition

AbstractA metal‐free methodology for the synthesis of 1,2‐disubstituted and 2‐substituted benzimidazoles with high to excellent yields has been developed. The course of synthesis involves easy work‐up, straightforward purification, inexpensive reaction setup, and wide substrate scope under extremely mild and operationally simple conditions which makes the synthetic strategy more lucrative, practical and reliable. The serious challenge to carry out these reactions in a pure aqueous medium has been achieved at 75 °C in presence of air bubbles. The applicability of this operationally simple and metal‐free synthetic approach for the gram‐scale synthesis of benzimidazole derivatives with good yield (∼74%) further strengthens its potentiality for the synthesis at an industrial scale.

Application of food preservatives and food additives in making Maldivian food products

Food additives play a huge role in food safety and development of various food products. Stabilizers are one of the food additives which help in increasing the stability as well as the viscosity of the food products. Stabilizers are found in almost all of the dairy products, desserts and many beverages. In addition, food colours are added to different types of foods to increase shelf life, visual attractiveness and to compensate for natural colour variations. Food dyes utilized in colouring mostly come from natural or artificial sources. The objectives of this study were to produce coconut ice cream using agar-agar stabilizer, conduct a sensory evaluation by a panel of 20 people using Likert scale to see the acceptability of the ice cream. Parameters like melting time and the presence of air bubbles were observed after freezing of the ice cream. Based on the sensory evaluation, for the overall acceptance of the ice cream a score of 9 was given. The results showed that it had a melt run of 130s/g and many air bubbles were formed before and after freezing. In the second part, a traditional Maldivian sweet known as “Ulhaali”was produced by adding beetroot extract into its key ingredient coconut honey or “Dhiyaa hakuru”, and ran a sensory evaluation of the product by a group of 15 participants, in terms of colour, aroma and taste, in order to draw a conclusion regarding the acceptability of the addition of the natural food colourant into the Maldivian sweet. Factors such as the colour retention was observed before and after frying. From the results obtained for the sensory evaluation, the product was highly accepted by the participants as all three descriptors received scores of 8.5 and above out of 10, and after addressing the limitations, the success of the study was rather high.