High Viscosity Conditions Research Articles

A one-way coupling approach for simulating in-nozzle flow and spray characteristics of a pressure-swirl atomizer

This article proposes a model framework coupling in-nozzle flow and external spray and presents its application to the simulation of a commercial pressure-swirl atomizer, focusing on the transient characteristics of the internal flow and subsequently the impact on the spray characteristics. High-fidelity in-nozzle simulation of the liquid–gas interactions is performed using the volume-of-fluid (VOF) method. Then, a corresponding Lagrangian simulation of sprays is performed where the parcels are injected using the information from the VOF predictions instead of phenomenological models. Both the internal flow and the spray are compared to the experimental data that are available in the literature, and satisfactory agreement is obtained in terms of the in-nozzle velocity, film thickness, and Sauter mean diameter. The effect of the different liquid properties and geometric features on the air–core formation, and consequently, on the spray characteristics have been obtained directly through spray simulation coupled with nozzle flow. As indicated by the Eulerian simulation results, the viscosity plays a key role in the formation of the air core, as the hollow-cone shape can degenerate into a solid cylindrical liquid jet under high viscosity conditions. Additionally, significantly distinct spray characteristics in terms of droplet velocity, mean diameter, and penetration were predicted depending on the formation of air core. Even if there is no stable air core in the nozzle, the spray is still discharged in a swirling motion. As opposed to the converging angle and orifice length, the nozzle diameter has a direct correlation with the formation of air core and spray atomization. This study implies that the in-nozzle flow field, which is usually ignored in fuel spray simulation, has a substantial impact on the spray characteristics and should be taken into account for design optimization by applying the developed one-way coupling approach.

Stereo-complex polylactide composite aerogel for crude oil adsorption

Adsorption materials are a cost-effective and simple method for oil spill remediation, but their efficiency is limited by high crude oil viscosity. Additionally, non-degradable materials pose another risk of secondary pollution, such as microplastic debris. Here, an environmentally-friendly stereo-complex polylactide composite (SCC) aerogel were developed via water-assisted thermally induced phase separation. The SCC with 3 wt% carbon nanotubes had a hierarchical structure of micro/nanoscale pores and high content of stereo-complex crystallites (35.7 %). Along with the excellent water repellency (water contact angle: 157°), SCC aerogel was 2.7 times as resistant to hydrolysis than poly(l-lactide) aerogel (Ph = 13, 37 °C). Additionally, a maximum absorption capacity of 41.2 g g−1 and over 97 % oil/water separation efficiency after 10 cycles were obtained in low viscosity conditions; while in high viscosity conditions, it displayed excellent photothermal performance, reaching a surface temperature of 85 °C under 1 sunlight, reducing crude oil absorption time from 42 min to 60 s (97.6 %-time savings). Moreover, it facilitated continuous crude oil spill recovery under sunlight with an adsorption rate of 3.3 × 104 kg m−3 h−1. The SCC aerogel presents a potential route for utilizing solar energy in crude oil adsorption applications without additional environmental burden.

Research Progress on Displacement Mechanism of Supercritical CO2 in Low-Permeability Heavy Oil Reservoir and Improvement Mechanism of Displacement Agents.

With the continuous growth of global energy demand and the late stage of conventional oilfield exploitation, the demand for developing and utilizing low-permeability heavy oil reservoirs is becoming increasingly urgent. However, the exploitation of low-permeability heavy oil reservoirs faces many challenges due to their high viscosity, low permeability, and complex geological conditions. To overcome these challenges, researchers have gradually introduced SC-CO2 as an oil displacement agent in the exploitation of heavy oil reservoirs. However, the oil displacement mechanism of SC-CO2 in low-permeability heavy oil reservoirs and its improvement mechanism are still not completely understood. The article provides a detailed study and understanding of the oil displacement mechanism of SC-CO2, which involves the expansion of heavy oil volume through SC-CO2 dissolution. This mechanism reduces the capillary resistance and flow resistance during the oil flow process. The permeation of CO2 disrupts the internal structure and arrangement of heavy oil, reducing its viscosity. CO2 extracts both light and heavy components from the heavy oil, reducing the residual oil saturation. In addition, the mechanism of improving the effect of oil displacement agents such as nanoparticles, polymers, and surfactants on SC-CO2 displacement was also explored. By further exploring the mechanisms and improvement mechanisms of SC-CO2 displacement for heavy oil, it can guide the selection and optimization of oil displacement agents. Furthermore, understanding the mechanism can also provide a theoretical basis for engineering practice and technical innovation. While the research on CO2 flooding is analyzed and evaluated, the obstacles and challenges that still exist at this stage are indicated, and future research work on CO2 in low-permeability heavy oil reservoirs is proposed.

Environmentally responsive multistage gas/enzyme/NIR-driven chemotactic transport nanorockets for single wavelength procedural combination therapy

The high viscosity and deep-seated conditions of tumor tissues have led to the ineffective delivery of anti-cancer drugs. In order to improve the anti-tumor efficacy, we have developed a multistage gas/enzyme/Near-infrared light driven nanorocket (HA@MnCuGOD@MSN@DIN) for the procedural combination of photodynamic therapy, photothermal therapy, starvation therapy, chemodynamic therapy, and chemotherapy. The nanorocket is multistage driven to achieve deep penetration of tumor tissue under the conditions of high glucose concentration, acidic microenvironment, and local high temperature. Specifically, the first stage is CO2 gas-driven, using enhanced diffusion from gases release by the acid-response of MnCO3, while Fenton-like reaction of the released Mn(II) with H2O2 can achieve chemodynamic therapy; the second stage is enzyme-driven which is realized by efficient enzymatic reaction of glucose oxidase and glucose; the last stage is CO2/NH3 gas-driven produced by NH4HCO3 at NIR 808 nm or in an acid environment. With the multistage gas/enzyme-driven, the movement speed was increased from 11 μm/s to 30 μm/s, and the excellent deep puncture ability combined with procedural combination therapy effectively improves the anticancer efficacy. The application of multistage gas/enzyme/NIR-driven chemotactic transport nanorockets opens a new chapter in the field of deeply penetrating cancer treatment through procedural combination therapy.

A novel design for a selective fluid inflow control device

In oil field development projects, reservoir heterogeneity can easily to produce water ridge problems, resulting in premature water discovery in wells. Selective inflow control devices can effectively slow water ridging. However, there are relatively few studies on inflow control devices for medium and low viscosity crude oil with viscosity below 50 mPa s. In this study, a new type of selective inflow control device was designed for wells with low oil viscosities, and its performance was analyzed using experimental and numerical simulation software. The effects of the structural (inner inlet) and fluid parameters (viscosity, flow rate and water cut) on the performance of the selective inflow control device were simulated. The experimental results show that the flow pressure loss is still low when the oil viscosity is 32 mPa s, and it can achieve a more considerable flow difference between oil and water at a larger flow rate. The simulation results show that the best suitable viscosity of the device is 50 mPa s. The internal structure of the tool has considerable influence on the pressure loss and flow-field distribution under low-viscosity conditions. Under high viscosity conditions, the pressure loss gradually exhibited a linear trend, and the influence of the internal structure decreased. When the flow rate is greater than 2 m³/d, the internal flow field distribution is more affected by the viscosity than the flow rate.

Liquid-liquid dispersion and flow characteristics in a miniaturized annular rotating device

Liquid-liquid microchemical processes suffer from the problems of small handling capacity and large pressure drops. In particular, process intensification is highly required for high phase ratios of the dispersion phase to the continuous phase and high- viscosity conditions. In this study, we reported a novel microdispersion device named miniaturized annular rotating device (m-ARD), which is a novel microdispersion device with a large handling capacity, small pressure drop, and relatively narrow droplet distribution, even at a low phase ratio of the continuous phase to the dispersion phase and under high-viscosity conditions. Various parameters were studied to determine the dispersion of the generated droplets and the flow pattern, average droplet diameter, pressure drop, and hold-up of the dispersion phase. Two typical droplet generation routes, namely, dripping and jetting, and typical flow patterns, i.e., helical and annular flows were also obtained. Transition maps of the droplet generation route and flow pattern were constructed. The average droplet diameter and handling capacity were up to 380 μm and 30 mL/min, respectively. A small pressure drop was observed in the m-ARD. Furthermore, two dimensionless equations were developed to calculate the average droplet diameter and hold-up of the dispersion phase. This work provides a promising dispersion technology for the process intensification of liquid–liquid mass transfer and reactions.

Determination of fluorescence quantum yields and decay times of NADH and FAD in water–alcohol mixtures: The analysis of radiative and nonradiative relaxation pathways

Combined studies on fluorescence quantum yield of coenzymes NADH and FAD in water–methanol, water–ethanol and water–propylene glycol mixtures and on time-resolved fluorescence of these molecules under excitation at 450 and 355 nm by means of time-correlated single photon counting (TCSPC) method have been carried out. A novel model that allowed to separate the contributions from several excited state relaxation mechanisms to fluorescence dynamics in the pico- and nanosecond time domains and to fluorescence quantum yield was developed and used for analysis of experimental data. The results indicated the existence of at least two different nonradiative relaxation mechanisms in NADH and FAD: a relatively slow nanosecond and a much faster picosecond ones. The analysis suggested that the increase of NADH fluorescence quantum yield with all alcohols concentration occurred mainly due to relatively slow nanosecond non-radiative and radiative relaxation mechanisms related with the change of conformation distributions, while the picosecond fluorescence quenching was found to have practically the same and conformation-insensitive value in water–monohydric alcohol mixtures. Similar conclusion was made for NADH in water–propylene glycol solutions where however a moderate decrease of the picosecond quenching rate was determined at high propylene glycol concentrations that was attributed to a slowdown of picosecond quenching under high viscosity conditions. In the case of FAD the analysis suggested that the dramatic rise of fluorescence quantum yield with alcohol concentration was mostly due to the conformation-sensitive picosecond quenching. This conclusion supports the known mechanism of the picosecond fluorescence quenching in FAD through electron transfer reaction in the π-stacked conformation between isoalloxazine and adenine moieties. Radiative decay times in NADH and FAD were estimated from experimental data and found to be about 10 ns and 20–30 ns, respectively.

Carbon nanotubes/polyethylenimine/glucose oxidase as a non-invasive electrochemical biosensor performs high sensitivity for detecting glucose in saliva

With the aim of improving the life quality for diabetics, we develop a novel electrode for the noninvasive glucose sensor which can determine the glucose levels in saliva. In this work, carbon nanotubes (CNTs) are directly grown on a fluorine-doped tin oxide (FTO) coated glass substrate through chemical vapor deposition, followed by the immobilization of glucose oxidase (GOx) via electrostatic force with the aid of polyethylenimine (PEI). The results confirm that the CNT forest can substantially enhance the charge transferability, and considerable quantities of GOx can be stably immobilized on the rough surface of the electrode because of the networked structure of the CNT forest. With a fast electron transfer rate and short electron transfer distance, both the current difference of the oxygen consumption and enzyme reduction reaction are detected for glucose sensor using the cyclic voltammetry method. The FTO-CNTs/PEI/GOx electrode exhibits the high sensitivity of 63.38 µA/mMcm2 with a wide linear range of 70–700 µM glucose. Furthermore, the FTO-CNTs/PEI/GOx electrode shows good stability as well as high selectivity towards glucose. Finally, the glucose sensing performance of the FTO-CNTs/PEI/GOx electrode is investigated in artificial saliva, which exhibits great sensitivity even under high-viscosity conditions such as artificial saliva, thus, reveals excellent potential for use in practical applications.

Viscous and centrifugal instabilities of massive stars

ABSTRACT Massive stars exhibit a variety of instabilities, many of which are poorly understood. We explore instabilities induced by centrifugal forces and angular momentum transport in massive rotating stars. First, we derive and numerically solve linearized oscillation equations for adiabatic radial modes in polytropic stellar models. In the presence of differential rotation, we show that centrifugal and Coriolis forces combined with viscous angular momentum transport can excite stellar pulsation modes, under both low- or high-viscosity conditions. In the low-viscosity limit, which is common in real stars, we demonstrate how to compute mode growth/damping rates via a work integral. Finally, we build realistic rotating $30\, \mathrm{M}_\odot$ star models and show that overstable (growing) radial modes are predicted to exist for most of the star’s life, in the absence of non-adiabatic effects. Peak growth rates are predicted to occur while the star is crossing the Hertzsprung–Russell gap, though non-adiabatic damping may dominate over viscous driving, depending on the effective viscosity produced by convective and/or magnetic torques. Viscous instability could be a new mechanism to drive massive star pulsations and is possibly related to instabilities of luminous blue variable stars.

Experimental investigation on the distribution characteristics of droplets in annular flow with wide liquid viscosity range

The existence of droplets in an annular flow has a non-negligible influence on the mass transfer and heat transfer between phases, and a phase property, such as liquid viscosity, can dominate the droplet characteristics. However, the effects of liquid viscosity on droplets have not yet received sufficient attention. In this study, the distribution characteristics of droplets in a vertical annular flow with a liquid viscosity of 1–30 mPa·s are experimentally investigated using a particle dynamic analyzer. The results reveal that the diameter and momentum of the droplet undergo two different changes during the increase of liquid viscosity, μL. In the low-liquid-viscosity range (μL < 10 mPa·s), the diameter and momentum of the droplet increase significantly with an increase in viscosity, whereas in the high-liquid-viscosity range (μL ≥ 10 mPa·s), their dependence on viscosity is considerably low. Owing to the different degrees of aggregation and fragmentation of droplets under different liquid viscosities, the radial evolution of droplets also show obvious distinctions. In addition, the slip ratio of the droplet velocity under different liquid viscosities is determined. When the liquid viscosity increases from 1 to 30 mPa·s, the droplet velocity decreases by 20.3% on average in the gas velocity range of 25–58 m/s, and small droplets have a relatively higher velocity and velocity range. Further, on the experiments show that the droplet deformation increases sharply with an increase in liquid viscosity because of the change in droplet generation mechanisms. The minimum proportion of the spherical droplet reduces to 9.2% at μL= 30 mPa·s, indicating that the droplet cannot be simply regarded as spherical when calculating the mass and heat transfer with high liquid viscosity. Finally, the present results can assist in multiphase flow modeling under high-viscosity conditions.

Interface-dominated mechanical behavior of CF/PEKK composites according to different heating rate during thermoforming process

While thermoplastic polymers exhibit several desirable properties, their applicability is limited by their high viscosity and extreme processing conditions. To overcome these limitations, in this study, we used the thermoforming process to produce carbon fiber/polyetherketoneketone (CF/PEKK) laminates, which were pre-made through an oven-based consolidation process using prepregs. The laminates were produced at three different heating rates ([Formula: see text]C/min, [Formula: see text]C/min and [Formula: see text]C/min). The laminates produced at the heating rate of [Formula: see text]C/min showed improved interlaminar shear strength, [Formula: see text] tensile strength, and average interlaminar fracture toughness. On the other hand, heating at rates higher than [Formula: see text]C/min increased the initiation value of the interlaminar fracture toughness ([Formula: see text] but resulted in nonuniform composites of poor quality. This is because increasing the heating rate reduced the uniformity of the heat distribution with the laminates, resulting in the polymer molecules exhibiting different binding rates and thus nonuniform cross-linking. Thus, the proposed method is a suitable one for producing high-quality thermoplastic composites.

Facile mitochondria localized fluorescent probe for viscosity detection in living cells

Fluorescent probes act as a powerful tool to understand the function of intracellular viscosity, which are closely associated with many functional disorders and diseases. Herein we report a boron-dipyrromethene (4,4-difluoro-4-borata-3a,4a-diaza-s-indacene, BODIPY) group based new fluorescent probe (BV-1), which was synthesized facilely by a one-step Knoevenagel-type condensation reaction, to detect viscosity in living cells with high selectivity and sensitivity. DFT calculation demonstrated that the unsaturated moiety at the meso-position of BODIPY suppressed the fluorescence via twisted intramolecular charge transfer (TICT) mechanism in low viscosity media. By restricting the rotation of the molecular rotor, the fluorescence would be enhanced significantly with redshift in emission wavelength in high viscosity conditions. The fluorescence intensity ratio (log (I/I0)) at 570 nm showed a good linearity (R2 = 0.991) with the viscosity (log η) in the range of 2–868 cP. And the limit of detection (LOD) and limit of quantification (LOQ) for viscosity were calculated to be 0.16 cP and 0.54 cP, respectively. BV-1 was demonstrated to be mitochondria localized with low cytotoxicity. Utilizing the new probe BV-1, the changes in mitochondrial viscosity caused by monensin or nystatin have been monitored successfully in real time. This work will provide new efficient ways for the development of viscosity probes, which are expected to be used for the study of intracellular viscosity properties and functions.

Facile preparation of Poly(butylene succinate)/Carbon nanotubes/polytetrafluoroethylene ternary nanocomposite foams with superior electrical conductivity by synergistic effect of “ball milling” and supercritical fluid-Assisted processing

Conductive polymer composites (CPCs) with different types of polytetrafluoroethylene (PTFE) were prepared via melt mixing, and the cellular structure was introduced into poly (butylene succinate) (PBS) by the supercritical CO2 foaming technique. The carbon nanotubes (CNTs) had the best dispersion in the PBS/CNTs/PTFE-P5 composite (PTFE with a diameter of approximately 5–10 μm). The CNTs enhanced the crystallizability of PBS, and the addition of PTFE was more significant, especially PTFE-P5. The storage modulus increased, and a transition from liquid-like to solid-like behavior occurred at low frequencies. Adding PTFE dramatically improved the pore structure, leading to a two-orders-of-magnitude increase in pore density, especially for PTFE-P5. The conductivity (δ) of solid PBS/CNTs/PTFE-P5 was four times higher than that of PBS/CNTs. The δ values of all the foams were much higher than those of their solid counterparts, demonstrating that the introduction of a large number of pores optimized the dispersion of CNTs and further improved the electrical conductivity because of the formation of a more complete conductive network structure (CNS). In particular, the δ value of foamed PBS/CNTs/PTFE-P5 under 3 wt% CNT loading reached 54.05 S/m. The thermal and mechanical properties, as well as the thermal conductivity, were also investigated. This work provides a simple method to prepare flexible biodegradable CPCs with a highly dispersed CNT CNS under high melt viscosity conditions.

Low-Dimensional Assemblies of Magnetic MnFe2O4 Nanoparticles and Direct In Vitro Measurements of Enhanced Heating Driven by Dipolar Interactions: Implications for Magnetic Hyperthermia

Magnetic fluid hyperthermia (MFH), the procedure of raising the temperature of tumor cells using magnetic nanoparticles (MNPs) as heating agents, has proven successful in treating some types of cancer. However, the low heating power generated under physiological conditions makes necessary a high local concentration of MNPs at tumor sites. Here, we report how the in vitro heating power of magnetically soft MnFe$_2$O$_4$ nanoparticles can be enhanced by intracellular low-dimensional clusters through a strategy that includes: a) the design of the MNPs to retain N\'eel magnetic relaxation in high viscosity media, and b) culturing MNP-loaded cells under magnetic fields to produce elongated intracellular agglomerates. Our direct in vitro measurements demonstrated that the specific loss power (SLP) of elongated agglomerates ($SLP=576\pm33$ W/g) induced by culturing BV2 cells in situ under a dc magnetic field was increased by a factor of 2 compared to the $SLP=305\pm25$ W/g measured in aggregates freely formed within cells. A numerical mean-field model that included dipolar interactions quantitatively reproduced the SLPs of these clusters both in phantoms and in vitro, suggesting that it captures the relevant mechanisms behind power losses under high-viscosity conditions. These results indicate that in situ assembling of MNPs into low-dimensional structures is a sound possible way to improve the heating performance in MFH.

A connection between magma chamber processes and eruptive styles revealed at Nisyros-Yali volcano (Greece)

Arc volcanoes generally emit water-rich, high-viscosity silicic magmas, which are prone to erupt explosively. However, effusive behavior is a common occurrence despite the high-H2O, high viscosity conditions. The contrasting shift from effusive to explosive behavior (and vice-versa) at any individual volcano raises the question on what controls eruptive style. Permeability development in conduits allows magma to outgas and is clearly a key factor. However, an important question is whether magma reservoir processes can also have an influence on eruptive styles. The answer could have direct impact on predicting eruptive behavior. Hence, we explore this potential connection by analyzing nine alternating effusive and explosive silicic deposits that were emplaced during distinct eruptions at the active Nisyros-Yali volcanic center. The lavas and pyroclastic deposits are compositionally similar. This indicates a negligible influence of the bulk rock composition on different eruptive styles. The crystal contents vary between units, without any clear correlation with eruptive style (from nearly aphyric to ~45 vol% crystals). Mineral textures and chemistry do show variations between effusive and explosive eruptions, with a larger proportion of resorbed plagioclase and, in most cases, more evolved amphiboles present in the lava flows. Mineral thermo-barometry and hygrometry show that the storage zones of magmas generating effusive eruptions evolved towards colder and more water-rich conditions (710–790 °C; 5.6–6.5 wt% H2O) than their explosive counterparts (815–850 °C; 4.2–4.6 wt% H2O). At storage pressures of 1.5–2 kbar, relevant for Nisyros-Yali, the volatile saturation level is reached at >5 wt% H2O. Therefore, it is likely that the magmas reached water-saturation before generating effusive eruptions, and were undersaturated before explosive events. We hypothesize that the presence of exsolved volatiles in the subvolcanic reservoir can enhance the outgassing potential of the magma during conduit ascent. Hence, the rhyolitic effusive-explosive transitions can be influenced by the pre-eruptive exsolved versus dissolved state of the volatiles in the magma chamber. This can lead to the less explosive eruptions for the most water-rich reservoir conditions.

Carbon Dioxide Diffusivity in Single, Levitated Organic Aerosol Particles.

The diffusivity of molecules relevant to condensed-phase chemistry within viscous secondary organic aerosol (SOA) remains highly uncertain. Whereas there has been an effort to characterize water diffusivity as well as the diffusivity of larger compounds, data are lacking almost entirely for small molecules, such as carbon dioxide (CO2). Here we use photochemically generated CO2 in single particles of aqueous citric acid as a SOA proxy, levitated in an electrodynamic balance, to deduce CO2 diffusivity in the particle with unprecedented accuracy. For medium viscosities at intermediate relative humidities (∼25-40% RH), we find CO2 diffusivities DCO2 ≈ 10-14 m2 s-1, agreeing with the Stokes-Einstein relationship based on current viscosity data but 10 times lower than that for water. Conversely, under dry high-viscosity conditions, we find that DCO2 ≈ 10-16 m2 s-1, which is 10 times higher than for water. We infer that the chemical degradation of atmospheric SOA particles will likely not be limited by CO2 diffusivity.

Effect of gas distributor on gas–liquid dispersion and mass transfer characteristics in stirred tank

Aiming at the fact that the function of gas distributor is often neglected in the case of high viscosity conditions, a novel spherical micro-orifice gas distributor was proposed and investigated experimentally in water system and non-Newtonian viscous system, respectively. The comparisons of gas–liquid dispersion and mass transfer performance between novel spherical micro-orifice gas distributor and traditional ring distributor were also done. Furthermore, the effects of gas distributors on the gas–liquid dispersion and mass transfer characteristics of three wide-viscosity-range impellers including LDB impeller, FZ impeller and MB impeller were also researched, and an impeller-distributor configuration with good gas–liquid dispersion and mass transfer performance was achieved. The results show that, compared with ring gas distributor, the bubbles dispersed by novel spherical micro-orifice gas distributor are smaller, and the gas holdup and volumetric mass transfer coefficient are relatively higher under the same power consumption per unit volume. Meanwhile, the significant effect of gas distributor geometry on gas dispersion was found for high-viscosity liquid, but not relevant for low-viscosity batches. In addition, compared with other impeller-distributor configurations, the configuration consisting of FZ impeller and novel spherical micro-orifice gas distributor can achieve greater global gas holdup and higher oxygen mass transfer rate, which is recommended especially in viscous system with high gas flow rate. The research is beneficial to promote the application of novel spherical micro-orifice gas distributor in stirred tanks.

Different adhesion behaviors of platelets depending on shear stress around stenotic channels

Platelet adhesion, activation, and aggregation play important roles in pathological thrombosis and the progression of atherosclerosis. In our previous study, it was observed that the probability of platelet adhesion increased under high-hematocrit conditions. The present study aimed to investigate how the interactions between hemodynamic properties and platelet adhesion around stenosed channels varied according to the hematocrit level. After passing through the narrow stenotic channels with different stenotic widths (100, 50, and 10 μm), the platelets were activated, and then these platelets were adhered on the downstream of the stenosis. Flow information, such as the velocity field and shear rate around the stenotic channels, was estimated by using particle image velocimetry (PIV) measurements and simulations. By using a Y-shaped device, the viscosity variations according to the shear rate could be measured for samples with different hematocrit levels (0, 30, and 50%). Based on the estimated flow and viscosity information, the distribution of shear stress around the stenotic channels was estimated. Due to the high shear stress in the 10-μm-wide stenosis, significant adhesion of platelets with a 3D circulating motion was observed at the posterior end of the stenosis. In the 50-μm-wide stenosis, the degree of platelet adhesion varied according to the hematocrit levels; the area of the adhered platelets increased as the hematocrit of the sample increased. Thus, in relatively high-viscosity conditions, frequent particle collision can contribute to the promotion of platelet activation and adhesion, even when the shear rate is relatively low. This study provides a better understanding of the effect of the hematocrit level on the adhesion of platelets after they pass through a stenosis.

Effect of Fluid Viscosity on the Cilia-Generated Flow on a Mouse Tracheal Lumen.

Mucous flow in a tracheal lumen is generated by the beat motion of ciliated cells to provide a clearance function by discharging harmful dust particles and viruses. Due to its physiological importance, the cilia-generated flow and the rheological properties of mucus have been investigated intensively. The effects of viscosity on the cilia-generated flow, however, have not been fully clarified. In this study, we measured bulk background velocity of ciliary flow using a micro particle tracking velocimetry method under various viscosity conditions in mice. The results showed that the flow velocity decreased as the increase with viscosity of ambient fluid. Moreover, no previous study has clarified the pump power generated by cilia, which provides important information with regard to understanding the molecular motor properties of cilia. Measurements of both the ciliary flow and the ciliary motion were conducted to determine the cilia pump power. Our results indicated that the cilia pump during the effective stroke did not drive the ciliary flow efficiently under high viscosity conditions; these findings are necessary to resolve the clearance function.

Multifunctional Single-Phase Photocatalysts: Extended Near Infrared Photoactivity and Reliable Magnetic Recyclability.

A practical photocatalyst should be able to integrate together various functions including the extended solar conversion, a feasible and economic recyclability, and above the room temperature operation potential, et al., in order to fulfill the spreading application needs in nowadays. In this report, a multifunctional single-phase photocatalyst which possesses a high photoactivity extended into the near infrared region, an easy magnetic recyclability and the high temperature stability was developed by doping Co into a new layer-structured Bi7Fe3Ti3O21 material. Light absorption and photocatalytic activity of the resulted Bi7Fe3-xCoxTi3O21 photocatalyst were extended to the long wavelength as far as 800 nm. Its strong ferromagnetism above the room temperature enables the nanopowders fully recyclable in viscous solutions simply with a magnet bar in an experimental demonstration. Furthermore, such photoactivity and magnetic recyclability were heavily tested under high-temperature and high-viscosity conditions, which was intended to simulate the actual industrial environments. This work brings the bright light to a full availability of a new multifunctional photocatalyst, via integrating the much enhanced ferromagnetic, ferroelectric, optoelectronic properties, most importantly, into a single-phase structure.