Segmented Flow Research Articles

Dynamic mechanical properties of magnetorheological polyurethane elastomers in comparison to existing antivibration rubbers

ABSTRACT This article primarily focused on dynamic mechanical analysis over a frequency range (0.1 to 140 Hz), temperature range (−100 to 50°C) and strain amplitude (0.1 to 5 percent). During hysteresis testing, the damping coefficient (Tanδ) and energy dissipation of isotropic and anisotropic magnetorheological elastomers with iron nanoparticles in a polyurethane rubber matrix to existing antivibration rubber were compared. Under tensile loading, energy dissipation was measured using universal testing. Different percentages of carbon black (CB) filler (30 phr, 50 phr and 70 phr) in a polyurethane matrix were selected for anti-vibration rubber comparison. During hysteresis testing, energy absorption has been found to be greater in CB Magnetorheological Elastomers(MREs) than in isotropic and anisotropic MREs, owing largely to the inclusion of CB in the formulation. CB additives were also tested on materials that were like anisotropic MREs. Relative comparative samples with the same percentage concentration of CB mixed with iron nanoparticles have greater damping characteristics and energy absorption. However, at the glass transition temperature (Tg), certain trends in energy absorption have shifted because segment flow motion of rubber chains has the greatest impact on energy absorption at glass transition temperature.

Sea ice concentration impacts dissolved organic gases in the Canadian Arctic

Abstract. The marginal sea ice zone has been identified as a source of different climate-active gases to the atmosphere due to its unique biogeochemistry. However, it remains highly undersampled, and the impact of summertime changes in sea ice concentration on the distributions of these gases is poorly understood. To address this, we present measurements of dissolved methanol, acetone, acetaldehyde, dimethyl sulfide, and isoprene in the sea ice zone of the Canadian Arctic from the surface down to 60 m. The measurements were made using a segmented flow coil equilibrator coupled to a proton-transfer-reaction mass spectrometer. These gases varied in concentrations with depth, with the highest concentrations generally observed near the surface. Underway (3–4 m) measurements showed higher concentrations in partial sea ice cover compared to ice-free waters for most compounds. The large number of depth profiles at different sea ice concentrations enables the proposition of the likely dominant production processes of these compounds in this area. Methanol concentrations appear to be controlled by specific biological consumption processes. Acetone and acetaldehyde concentrations are influenced by the penetration depth of light and stratification, implying dominant photochemical sources in this area. Dimethyl sulfide and isoprene both display higher surface concentrations in partial sea ice cover compared to ice-free waters due to ice edge blooms. Differences in underway concentrations based on sampling region suggest that water masses moving away from the ice edge influences dissolved gas concentrations. Dimethyl sulfide concentrations sometimes display a subsurface maximum in ice -free conditions, while isoprene more reliably displays a subsurface maximum. Surface gas concentrations were used to estimate their air–sea fluxes. Despite obvious in situ production, we estimate that the sea ice zone is absorbing methanol and acetone from the atmosphere. In contrast, dimethyl sulfide and isoprene are consistently emitted from the ocean, with marked episodes of high emissions during ice-free conditions, suggesting that these gases are produced in ice-covered areas and emitted once the ice has melted. Our measurements show that the seawater concentrations and air–sea fluxes of these gases are clearly impacted by sea ice concentration. These novel measurements and insights will allow us to better constrain the cycling of these gases in the polar regions and their effect on the oxidative capacity and aerosol budget in the Arctic atmosphere.

Continuous synthesis of TiO2-supported noble metal nanoparticles and their application in ammonia borane hydrolysis

A stabilizer-free method based on segmented flow for the continuous synthesis of TiO2 supported noble metal nanoparticles (M/TiO2-MR, M = Pd, Pt or Au) was proposed. Due to the enhanced mixing performance arising from the internal circulation in the discrete plugs, the particle size of noble metal nanoparticles could be well controlled by reducing the metal precursors with NaBH4 just in the presence of TiO2 without using any stabilizer. In comparison with the batch method, the as-prepared M/TiO2-MR had smaller noble metal particle size and better dispersity. Experimental results showed that adjusting the oil-to-water phase ratio or increasing the total volume flow rate and synthetic temperature could lead to smaller average particle size with narrower distribution. The as-prepared M/TiO2-MR possessed higher catalytic activities in the hydrolysis of ammonia borane than those prepared by the batch method, which could be ascribed to smaller noble metal nanoparticles, exposing more active sites.

Endogenous expression of Notch pathway molecules in human trabecular meshwork cells

PurposeCells in the trabecular meshwork sense and respond to a myriad of physical forces through a process known as mechanotransduction. Whilst the effect of substratum stiffness or stretch on TM cells have been investigated in the context of transforming growth factor (TGF-β), Wnt and YAP/TAZ pathways, the role of Notch signaling, an evolutionarily conserved pathway, recently implicated in mechanotransduction, has not been investigated in trabecular meshwork (TM) cells. Here, we compare the endogenous expression of Notch pathway molecules in TM cells from glaucomatous and non-glaucomatous donors, segmental flow regions, and when subjected to cyclical strain, or grown on hydrogels of varying rigidity. MethodsPrimary TM from glaucomatous (GTM), non-glaucomatous (NTM) donors, and from segmental flow regions [high flow (HF), low flow (LF)], were utilized between passages 2–6. Cells were (i) plated on tissue culture plastic, (ii) subjected to cyclical strain (6 h and 24 h), or (iii) cultured on 3 kPa and 80 kPa hydrogels. mRNA levels of Notch receptors/ligands/effectors in the TM cells was determined by qRT-PCR. Phagocytosis was determined as a function of substratum stiffness in NTM-HF/LF cells in the presence or absence of 100 nM Dexamethasone treatment. ResultsInnate expression of Notch pathway genes were significantly overexpressed in GTM cells with no discernible differences observed between HF/LF cells in either NTM or GTM cells cultured on plastic substrates. With 6 h of cyclical strain, a subset of Notch pathway genes presented with altered expression. Expression of Notch receptors/ligands/receptors/inhibitors progressively declined with increasing stiffness and this correlated with phagocytic ability of NTM cells. Dexamethasone treatment decreased phagocytosis regardless of stiffness or cells isolated from segmental outflow regions. ConclusionsWe demonstrate here that the Notch expression in cultured TM cells differ intrinsically between GTM vs NTM, and by substratum cues (cyclical strain and stiffness). Of import, the most apparent differences in gene expression were observed as a function of substratum stiffness which closely followed phagocytic ability of cells. Interestingly, on soft substrates (mimicking normal TM stiffness) Notch expression and phagocytosis was highest, while both expression and phagocytosis was significantly lower on stiffer substrates (mimicking glaucomatous stiffness) regardless of DEX treatment. Such context dependent changes suggest Notch pathway may play differing roles in disease vs homeostasis. Studies focused on understanding the mechanistic role of Notch (if any) in outflow homeostasis are thus warranted.

Generalized synthesis of NaCrO2 particles for high-rate sodium ion batteries prepared by microfluidic synthesis in segmented flow

Ternary oxides NaMO2 (M = Cr, Fe, Co, Al) were prepared by microfluidic processing in water-in-oil emulsions followed by a short annealing step.

Re-crystallization mechanism of superplasticity of industrial titanium and nickel alloys

The results of the study are presented, showing that the mechanism of superplastic deformation of industrial titanium and nickel alloys is dynamic recrystallization (fluctuation-structural transition), which leads to a steady segmental (vacancy-segmental) flow of the material when the sample is stretched. The results obtained confirm the fallacy of the concept of the relationship between grain boundary sliding and the motion of grain boundary dislocations during superplastic deformation and the doubtfulness of the physical validity of the velocity sensitivity coefficient as a criterion for superplasticity. Keywords: superplasticity, grain boundary sliding, dynamic recrystallization, fluctuation-structural transition, velocity sensitivity coefficient, polycrystalline superplastic viscosity. Onischenko-ak@uecrus.com

Dynamic Semantic Occupancy Mapping Using 3D Scene Flow and Closed-Form Bayesian Inference

This paper reports on a dynamic semantic mapping framework that incorporates 3D scene flow measurements into a closed-form Bayesian inference model. Existence of dynamic objects in the environment can cause artifacts and traces in current mapping algorithms, leading to an inconsistent map posterior. We leverage state-of-the-art semantic segmentation and 3D flow estimation using deep learning to provide measurements for map inference. We develop a Bayesian model that propagates the scene with flow and infers a 3D continuous (i.e., can be queried at arbitrary resolution) semantic occupancy map outperforming its static counterpart. Extensive experiments using publicly available data sets show that the proposed framework improves over its predecessors and input measurements from deep neural networks consistently.

3D-printed capillary force trap reactors (CFTRs) for multiphase catalytic flow chemistry

Figure of 3D illustration of a capillary trap force reactor (CFTR) with transiently trapped liquid nanoparticle catalysts in dimple-shaped capillary traps in the presence of a gas–liquid segmented flow, for the hydrogenation of 1-hexene to n-hexane.

Toward continuous production of high-quality nanomaterials using microfluidics: nanoengineering the shape, structure and chemical composition.

Over the last decade, a multitude of synthesis strategies has been reported for the production of high-quality nanoparticles. Wet-chemical methods are generally the most efficient synthesis procedures since high control of crystallinity and physicochemical properties can be achieved. However, a number of challenges remain from inadequate reaction control during the nanocrystallization process; specifically variability, selectivity, scalability and safety. These shortcomings complicate the synthesis, make it difficult to obtain a uniform product with desired properties, and present serious limitations for scaling the production of colloidal nanocrystals from academic studies to industrial applications. Continuous flow reactors based on microfluidic principles offer potential solutions and advantages. The reproducibility of reaction conditions in microfluidics and therefore product quality have proved to exceed those obtained by batch processing. Considering that in nanoparticles' production not only is it crucial to control the particle size distribution, but also the shape and chemical composition, this review presents an overview of the current state-of-the-art in synthesis of anisotropic and faceted nanostructures by using microfluidics techniques. The review surveys the available tools that enable shape and chemical control, including secondary growth methods, active segmented flow, and photoinduced shape conversion. In addition, emphasis is placed on the available approaches developed to tune the structure and chemical composition of nanomaterials in order to produce complex heterostructures in a continuous and reproducible fashion.

Estimation of the phytoplankton biomass in Bahia Manzanillo, Colima (2016-2017)

Phytoplankton biomass (Chl-a) was estimated in 7 stations of Manzanillo Bay, Colima on the surface and at the Secchi depth in the rainy and dry season (2016-2017). To evaluate the biomass, a Millipore equipment and fiberglass GF / F filters were used using the spectrophotometric technique (Lorenzen, 1967). The physicochemical parameters were estimated with a YSI 85 equipment and the nutrients using a San Plus II segmented flow autoanalyzer. The average depth of the Secchi disk ranged from 5.9 m at the Puerto station to 12.8m at the center (A1 and A2). The temperature ranged from 26.9 to 28.1 ° C, the salinity between 31.6 and 33 ups and the dissolved oxygen from 3.81 to 4.82 mg L-1. The nutrients presented high values in Puerto, A1 and Carrizales. The central part of the bay registered values greater than one mg of Chl-a and a maximum of 2.67 mg .m-3 in the Puerto station. In 2016, Chl-a decreased significantly because of a very intense Niño event, also showing high concentrations of phaeopigments, which reveal grazing conditions or degraded chlorophyll. Through an analysis of variance, it was determined that there is a significant difference between the chlorophyll-a values (p≤0.05).

Gas–liquid slug flow in microfluidic heat exchanger: Effect of gas hold-up and bubble size on pressure drop and heat transfer

This work is an extension of our recent article, which was inspired by discussions with the reviewers. The paper presents an experimental study of the gas-liquid segmented flow as a method of intensifying microfluidic heat exchangers (MFHE) with a focus on studying the influence of the gas volume fraction. It was found that the highest heat transfer coefficient is achieved when the bubble size coincides with the channel diameter, which corresponds to a gas hold-up of 12%. Experimental studies have also shown that segmented flow makes it possible to increase the Nu up to 1.54 and reduce thermal resistance up to 1.67 times compared to single-phase flow.

Flow orientation as a parameter for process intensification in mesoscale biphasic flow

Interphase mass transfer and associated chemical reactions in biphasic liquid flow can be enhanced by tuning the phase distribution in the flow reactor. In reduced dimensions, a balance between surface, inertial and viscous forces results in either segmented flow where dispersed phase is distributed as plugs / droplets in the carrier phase, or thread flow where dispersed phase flows as a continuous thread through an annular film of the carrier phase. Our extensive experiments in up, down and horizontal co-flows of a liquid-liquid mixture through a glass conduit of 2.38 mm diameter reveal a subtle role of gravity in the mesodomain. We note plug generation by gravity assisted squeezing mechanism in upflow and observe squeezing, dripping and jetting mechanisms in the same device by a mere change in conduit orientation. While upflow promotes monodispersed plug generation, downflow is more conductive for thread flow and droplets rather than plugs are formed in horizontal flow. An in-depth investigation of plug generation cycle over a wide range of flow velocities suggests polydispersity to increase as thread pinch-off occurs further from the T-entry. The increase in dispersed phase hold-up with flow rate ratio is steeper for segmented flow than thread flow.

Effects of fluid film properties on fouling in biphasic flow systems

Flow chemistry has the potential to enhance the large-scale accessibility of precision-engineered nanomaterials. While reactor fouling presented a major challenge in precision control, the liquid–liquid segmented flow method has been demonstrated to reduce or even eliminate it. However, guidelines for properly selecting materials and designing parameters in such systems are currently lacking. For these reasons, the present study investigated two biphasic flow systems for continuous gold nanoparticle (AuNP) synthesis. Visual observations showed no evidence of fouling in the silicone oil–water flow system, but some localized fouling was observed in the heptane-water flow system. The results indicated the silicone oil–water system gave a 50% lower polydispersity index and a 25% higher reaction yield due to fouling mitigation. We investigated two important factors of the continuous phase for fouling reduction: liquid film continuity and film thickness. Film continuity was evaluated by temperature-controlled contact angle measurements and the film dewetting velocity; And film thickness was estimated using two different mathematical models. It was concluded that the formation of a continuous oil film of thickness higher than the maximum surface asperities, as was the case only for the silicone oil–water flow system, is critical to eliminate fouling in continuous AuNP synthesis.

Effect of Fluid Flow on Crystallization in a Segmented Flow Microchannel

Segmented flow crystallization has attracted the attention of engineers in the development of drug substance processes, because the crystallization behavior is different from that observed in conventional stirred tanks. Under segmented flow conditions, the crystal size distribution is narrower, and the crystallization rate is higher than that of batch crystallization. However, the phenomenological theory of segmented flow crystallization has not been clarified. The purpose of this study was to gain more insights into segmented flow crystallization phenomena. We focused on the influence of fluid behavior on crystallization. First, we analyzed the motion of crystals in a segmented flow using computational fluid dynamics. Under the assumption that the mass transfer is the rate-determining step of crystal growth, we evaluated how particle and flow conditions contribute to the mass transfer. The shear rate under segmented flow was found to be approximately 16 times greater than that in a stirred tank. The high shear rate induced a high mass transfer rate, which is often observed under segmented flow conditions.

Segmentation of the Aorta and Pulmonary Arteries Based on 4D Flow MRI in the Pediatric Setting Using Fully Automated Multi-Site, Multi-Vendor, and Multi-Label Dense U-Net.

Automated segmentation using convolutional neural networks (CNNs) have been developed using four-dimensional (4D) flow magnetic resonance imaging (MRI). To broaden usability for congenital heart disease (CHD), training with multi-institution data is necessary. However, the performance impact of heterogeneous multi-site and multi-vendor data on CNNs is unclear. To investigate multi-site CNN segmentation of 4D flow MRI for pediatric blood flow measurement. Retrospective. A total of 174 subjects across two sites (female: 46%; N=38 healthy controls, N=136 CHD patients). Participants from site 1 (N=100), site 2 (N=74), and both sites (N=174) were divided into subgroups to conduct 10-fold cross validation (10% for testing, 90% for training). 3 T/1.5T; retrospectively gated gradient recalled echo-based 4D flow MRI. Accuracy of the 3D CNN segmentations trained on data from single site (single-site CNNs) and data across both sites (multi-site CNN) were evaluated by geometrical similarity (Dice score, human segmentation as ground truth) and net flow quantification at the ascending aorta (Qs), main pulmonary artery (Qp), and their balance (Qp/Qs), between human observers, single-site and multi-site CNNs. Kruskal-Wallis test, Wilcoxon rank-sum test, and Bland-Altman analysis. A P-value <0.05 was considered statistically significant. No difference existed between single-site and multi-site CNNs for geometrical similarity in the aorta by Dice score (site 1: 0.916 vs. 0.915, P=0.55; site 2: 0.906 vs. 0.904, P=0.69) and for the pulmonary arteries (site 1: 0.894 vs. 0.895, P=0.64; site 2: 0.870 vs. 0.869, P=0.96). Qs site-1 medians were 51.0-51.3mL/cycle (P=0.81) and site-2 medians were 66.7-69.4mL/cycle (P=0.84). Qp site-1 medians were 46.8-48.0 mL/cycle (P=0.97) and site-2 medians were 76.0-77.4mL/cycle (P=0.98). Qp/Qs site-1 medians were 0.87-0.88 (P=0.97) and site-2 medians were 1.01-1.03 (P=0.43). Bland-Altman analysis for flow quantification found equivalent performance. Multi-site CNN-based segmentation and blood flow measurement are feasible for pediatric 4D flow MRI and maintain performance of single-site CNNs. 3 TECHNICAL EFFICACY: Stage 2.

Optimization of Airflow Field for Pneumatic Drum Magnetic Separator to Improve the Separation Efficiency

Traditional dry magnetic separation has poor separation efficiency for fine-grained materials, and combining airflow and a magnetic field may be one of the most effective means to improve it. Based on the pneumatic drum magnetic separator developed by our team, an improved pneumatic magnetic separator with a segmented flow field is proposed, which pushes materials to move along the separation surface. Analysis of flow field in the separation zone and the forces on particles show that the improved pneumatic magnetic separator makes it easier to collect fine magnetic particles, while nonmagnetic particles are more easily removed by airflow. Separation test results also show that the iron grade and the recovery of concentrate improved from 37.89% and 74.75% to 51.76% and 91.79%, respectively. The separation efficiency of the pneumatic drum magnetic separator has been remarkably improved by optimizing airflow field in the separation zone.

Determination of the transition boundary between segmented and continuous flow patterns in microfluidic liquid-liquid flows using dimensional analysis

Determination of the transition boundary between segmented and continuous flow patterns in microfluidic liquid-liquid flows using dimensional analysis

Comparison of Renal Segmental Artery Blood Flow on Doppler in Young Obese &amp; Non Obese Individuals

Aim: To compare renal segmental artery blood flow on Doppler in young obese &amp; non-obese individuals. Methodology: In University Ultrasound Clinic Green Town, Lahore, Pakistan, a comparative study was conducted. 180 patients of age group 16 to 25 were enrolled in this study with convenient sampling technique. All the obese &amp; non-obese patients having no history of renal disease were included in this study. Hypertensive and diabetic patients were also included. Pregnant females having any renal parenchymal disease were excluded. Results: In 90 non-obese individuals the average mean of PI was .989±.249 while in 90 obese individuals the average mean of PI was .985±.338. No statistical difference between the two averages as p-value 0.928&gt; α=0.05. Conclusion: Study concluded that no statistically significant difference between the average PI in non-obese individuals compared to the average of PI in obese individuals. Keywords: Obese, Renal segmental artery, Pulsatility Index (PI), Ultrasonography

Continuous synthesis of 2-tert-butyl phenol oxidation in gas-liquid segmented flow and its kinetic investigation

The process to produce tert-butylhydroquinone from 2-tert-butyl phenol (2-TBP) is of great importance in the application of phenolic derivatives. However, the oxidation of 2-TBP to 2-tert-butyl-1,4-benzoquinone (2-TBQ) as the first step is usually performed in traditional batch reactors, suffering the disadvantages of mass transfer limitation and potential risk of explosion. Herein, a safer process to enhance the catalytic oxidation was developed by introducing gas–liquid segmented flow in a microchannel reactor. The 2-TBQ yield was approximately 70% within 29.02 min while the time was 8 h to obtained almost the same yield (65%) in batch systems. CFD simulation was conducted, confirming that secondary flow was formed in liquid slugs. The corresponding intensive convection ensured the continuous and stable operation without particle sedimentation. On the basis of the enhanced mass transfer, the kinetics of 2-TBP oxidation was also investigated. The obtained reaction orders of 2-TBP and oxygen were 2.0948 and 0.4073, respectively.

Photoredox Iridium–Nickel Dual Catalyzed Cross-Electrophile Coupling: From a Batch to a Continuous Stirred-Tank Reactor via an Automated Segmented Flow Reactor

Photoredox Iridium–Nickel Dual Catalyzed Cross-Electrophile Coupling: From a Batch to a Continuous Stirred-Tank Reactor via an Automated Segmented Flow Reactor