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Anammox granular sludge (AnGS) serves as an important platform for cost-effective nitrogen removal from wastewater. Different to the traditionally sphere-like granules, a novel type of AnGS in a unique ellipsoid-like shape was obtained through enhancing shear force. The ellipsoid-like AnGS significantly exhibited a smaller aspect ratio (-25.1 %) and granular size (-11.8 %), compared to traditional sphere-like AnGS (p < 0.01). Comprehensive comparisons showed that ellipsoid-like AnGS possessed a significantly higher extracellular polymeric substances (EPS) content and strength, as well as an enhanced mass transfer and a higher viable bacteria proportion due to the larger substrate permeable zone (p < 0.01). Additionally, the anammox bacterial abundance (Candidatus Kuenenia) was 12.2 % higher in ellipsoid-like AnGS than in sphere-like AnGS. All these characteristics of ellipsoid-like AnGS jointly increased the specific anammox activity by 29.0 % and nitrogen removal capacity by 22.6 %, compared to sphere-like AnGS. Further fluid field simulation suggested the enhanced flow shear on the side surface of AnGS likely drove the formation of ellipsoid-like AnGS. The higher shear force on the side surface led to an increase of EPS content (especially hydrophobic protein) and elastic modulus, thus constraining lateral expansion. This study sheds light on impacts of granular shape, an overlooked morphological factor, on anammox performance. The ellipsoid-like AnGS presented herein also offers a unique and promising aggregate to enhance anammox performance.

Three-dimensional turbulence simulations of a RFX-mod diverted plasma are performed in the presence of a biasing electrode. The simulations show a strong suppression of turbulent transport caused by the induced $\mathbf{E}\times\mathbf{B}$ flow shear, which leads to the formation of an edge transport barrier with a pedestal-like structure, in qualitative agreement with RFX-mod experiments. The strong $\mathbf{E}\times\mathbf{B}$ flow shear turbulence suppression with edge voltage biasing is also observed in the proximity of the density limit crossing, suggesting that edge voltage biasing may allow for larger maximum achievable density values. By leveraging the simulation results, the theoretical scaling law of the edge pressure gradient length derived in (Giacomin and Ricci 2020 J. Plasma Phys. 86 5) is extended here to account for the $\mathbf{E}\times\mathbf{B}$ flow shear turbulence suppression caused by voltage biasing. The improved theoretical scaling with typical RFX-mod shearing rate values predicts a factor of two increase of the pressure gradient at the separatrix, which is comparable to RFX-mod experiments in the presence of voltage biasing. The implications of the flow shear turbulence suppression due to voltage biasing on the density limit in RFX-mod are also discussed.

Various physical processes in association with magnetic reconnection occur over multiple scales from the microscopic to macroscopic scale lengths. This paper reviews multi-scale and cross-scale aspects of magnetic reconnection revealed in the near-Earth space beyond the general global-scale features and magnetospheric circulation organized by the Dungey Cycle. Significant and novel advancements recently reported, in particular, since the launch of the Magnetospheric Multi-scale mission (MMS), are highlighted being categorized into different locations with different magnetic topologies. These potentially paradigm-shifting findings include shock and foreshock transient driven reconnection, magnetosheath turbulent reconnection, flow shear driven reconnection, multiple X-line structures generated in the dayside/flankside/nightside magnetospheric current sheets, development and evolution of reconnection-driven structures such as flux transfer events, flux ropes, and dipolarization fronts, and their interactions with ambient plasmas. The paper emphasizes key aspects of kinetic processes leading to multi-scale structures and bringing large-scale impacts of magnetic reconnection as discovered in the geospace environment. These key features can be relevant and applicable to understanding other heliospheric and astrophysical systems. [ABSTRACT FROM AUTHOR]

Simultaneous observations from Defense Meteorological Satellite Program, Swarm, Resolute Bay all‐sky imagers, GPS Total Electron Content and Super Dual Auroral Radar Network, are used to investigate the evolution and key characteristics of the Tongue of Ionization (TOI) being restructured into a polar cap patch. Six satellites crossed the TOI of patch as it moved from the dayside to the nightside. It was initially hot, then a mix of both cold and hot, and finally it became a cold patch. This suggests that cold patch is not only a result of solar extreme ultraviolet radiation, but may also develop when a hot patch cools down. Soft‐electron precipitation and flow shears both contribute to the TOI restructuring and the appearance of polar cap patch. The plasma density of patch at ∼500 km was at least 4 times higher than at ∼800 km. The plasma density enhancement gradually decreased as the patch evolved due to decreased production and transport of cold nightside low‐density plasma. Moreover, the duskward motion of the patch was influenced by changes in the ionospheric convection pattern. Plain Language Summary: The appearance of high‐density plasma is a common phenomenon in the polar ionosphere. High‐density polar cap patches usually form near the dayside sunlit region, and then move from the dayside to the nightside with the ionospheric flow. In the paper, we use multiple instruments including six satellites and ground‐based observations to carefully investigate an event that started out on the dayside. It was initially a hot tongue of ionization (TOI) of high density and high electron temperature, followed by a mix of hot and cold (high vs. low electron temperature), before it finally became a cold patch. Soft‐electron precipitation and flow shears both influenced the dayside high‐density TOI plasma restructuring and the appearance of polar cap patch. The enhanced plasma density gradually weakened as the plasma migrated toward the nightside due to decreased production and transport of cold nightside low‐density plasma. Moreover, the duskward motion of the patch was influenced by changes in the ionospheric convection pattern. Key Points: Cold dense plasma in the polar cap can appear either via transport of solar extreme ultraviolet plasma or after a hot patch cools downSoft‐electron precipitation and flow shears both influence the Tongue of Ionization restructuring and the appearance of polar cap patchesThe enhanced plasma density is reduced due to decreased production and transport of cold nightside low‐density plasma [ABSTRACT FROM AUTHOR]

A gyrokinetic threshold model for pedestal width–height scaling prediction is applied to multiple devices. A shaping and aspect ratio scan is performed on National Spherical Torus Experiment (NSTX) equilibria, finding $\Delta_{\mathrm{ped}} = 0.92 A^{1.04} \kappa^{-1.24} 0.38^{\delta} \beta_{\theta,\mathrm{ped}}^{1.05}$ for the wide-pedestal branch with pedestal width $\Delta_{\mathrm{ped}}$ , aspect ratio A , elongation κ , triangularity δ , and normalized pedestal height $\beta_{\theta,\mathrm{ped}}$ . The width–transport scaling is found to vary significantly if the pedestal height is varied either with a fixed density or fixed temperature, showing how fueling and heating sources affect the pedestal density and temperature profiles for the kinetic-ballooning-mode (KBM) limited profiles. For an NSTX equilibrium, at fixed density, the wide branch is $\Delta_{\mathrm{ped} } = 0.028 \left(q_\textrm e/\Gamma_\textrm e - 1.7 \right)^{1.5} \sim \eta_\textrm e ^{1.5}$ and at fixed temperature $\Delta_{\mathrm{ped} } = 0.31 \left(q_\textrm e/\Gamma_\textrm e - 4.7 \right)^{0.85}$ $ \sim \eta_\textrm e ^{0.85}$ , where $q_\textrm e$ and $\Gamma_\textrm e$ are turbulent electron heat and particle fluxes and $\eta_\textrm e = \nabla \ln T_\textrm e / \nabla \ln n_\textrm e$ for an electron temperature $T_\textrm e$ and density $n_\textrm e$ . Pedestals close to the KBM limit are shown to have modified turbulent transport coefficients compared to the strongly driven KBMs. The role of flow shear is studied as a width–height scaling constraint and pedestal saturation mechanism for a standard and lithiated wide pedestal discharge. Finally, the stability, transport, and flow shear constraints are combined and examined for an NSTX experiment.

The role of a series of quasi-coherent modes (QCMs) on the turbulence properties has been investigated during Type-III ELMs under HL-2A high confinement mode (H-mode) scenarios. The QCMs are essentially electrostatic and appear during the inter-ELM periods, with a frequency ranging from 20 kHz to 60 kHz. These QCMs are localized in the pedestal region and are related to the saturation of density gradient in the pedestal. Nonlinear couplings between QCMs and ambient turbulence have been observed and also verified through the envelope modulation of turbulence in density by the radial electrical field fluctuation of the modes. The presence of QCMs can increase the radial and poloidal turbulence correlation lengths, thereby modulating the turbulent transport. Experimental results show that QCMs significantly impact pedestal turbulence and transport by increasing the correlation length as well as the decorrelation time of turbulent eddies. The flow shearing rate in pedestal region is also enhanced to a level that surpasses the decorrelation frequency of turbulence, thus, the existence of QCMs has the ability to put off the ELM burst due to relative stronger stabilization of turbulence by sheared flows. The above results have demonstrated that the pedestal dynamics is largely determined by the complex interactions among QCMs, turbulence and the shear flow.

The Langmuir probe observed an increase in density and floating potential fluctuations after the sawtooth crash at the edge of HL-2A neutral beam injection heated plasma. This process initiates fluctuating-induced radial inward particle transport once the plasma enters a period with strong sawtooth crash. The inward transport comprises broad-band fluctuations with varying scales, which occur uniquely in the immediate aftermath of the sawtooth crash-driven outflow, signifying a transient phenomenon confined to that specific interval. These results demonstrate that the sawtooth crash can significantly impact edge turbulence by modifying electrostatic fluctuations. This modification changes the direction of electric fluctuation-induced particle transport, thereby reducing the influence of the intense sawtooth crash-driven outflow. Furthermore, the observations support the existence of a damping mechanism for the outflow during the formation of inward flux after the sawtooth crash, which may be associated with the recovery process of sawtooth cycle.

In this study, we present the first data obtained from the new Transition Region Explorer (TREx) RGB Imager and analyze the apparent motion of STEVE and the Picket Fence structures in an event on 31 August 2019. The structures associated with STEVE are found to feature a fast westward motion (~5–10 km/s). This is consistent with the notions that STEVE is colocated with a fast subauroral ion drift (SAID) channel and that SAIDs play a key role in the production of STEVE. The apparent motion of the Picket Fence structures is much slower (~400–600 m/s) and can be both westward and eastward. This implies that either the Picket Fence is located at different magnetic flux tubes from that of STEVE, with much slower plasma convection speed, or that the motion of the Picket Fence does not follow the plasma convection. Plain Language Summary: The recently mounted Transition Region Explorer (TREx) RGB Imager is designed to capture "true color" images of the aurora and airglow with high time resolution and is thus ideal for the identification and tracking of STEVE (pink/mauve) and the Picket Fence (green) phenomena. Using the first data from the new TREx RGB imager at Lucky Lake, Canada, we analyze the apparent motion of STEVE and Picket Fence structures in an event on 31 August 2019. The structures associated with STEVE display a fast westward motion (~5–10 km/s), which is part of the reason for its acronym (velocity enhancement). The apparent motions of the Picket Fence structures are much slower (~400–600 m/s) and can be both westward and eastward. The above information on the motion speed of STEVE and the Picket Fence is important to the ongoing exploration of their underlying mechanisms. Key Points: We analyze the motion of STEVE and the Picket Fence using the first data obtained from the new Transition Region Explorer True‐Color ImagerThe structures within STEVE show a rapid westward motion (~5–10 km/s), compatible with the speed of a fast subauroral ion drift (SAID) channelThe motion of the Picket Fence is much slower (~400–600 m/s) and can be both westward and eastward, implying a strong flow shear with SAID [ABSTRACT FROM AUTHOR]

Although the postmidnight‐to‐dawn sector of the auroral ionosphere contains interesting dynamic phenomena that may significantly impact the magnetosphere‐ionosphere‐thermosphere system, it has been much less studied than the dusk‐to‐premidnight sector. We discuss a dynamic phenomenon in the postmidnight‐to‐dawn sector of the auroral oval, eastward fast flows mainly within the expanse of the Region 1 current (its part equatorward of the polar cap). These flows peak and have a steep speed gradient (increase from low to high latitude) near the interface between the Region 1 and Region 2 currents. Because such flows correspond to an electric field that most likely comes from enhanced Region 2 currents and an associated spatial conductivity gradient, their generation mechanism is analogous to that of a subauroral polarization stream. Therefore, we refer to such an eastward flow as a dawnside auroral polarization stream (DAPS). We show several examples of the presence and absence of DAPS under different geomagnetic activity levels. A DAPS' electric field can heat the ionosphere (and thus the thermosphere), change the convection pattern of the magnetosphere‐ionosphere system, and modify the drift path of magnetospheric particles. Because a DAPS' flow peak maps to a major site of magnetic‐kinetic energy conversion in the magnetosphere (the transition region between dipole and stretched field), it may be important for the conversion. A DAPS' steep flow gradient is also potentially important; it may lead to instabilities, such as that responsible for auroral Omega bands. Given its potential importance, knowledge of DAPS is fundamental for understanding the magnetosphere‐ionosphere‐thermosphere system. Plain Language Summary: Phenomena in Earth's magnetosphere (thousands of kilometers to hundreds of thousands of kilometers away from Earth's surface) lead to plasma flows in Earth's ionosphere (hundreds of kilometers above Earth's surface). Ionospheric properties modify these flows, which in turn feed back to the magnetosphere and result in other activities there. Ionospheric flows significantly affect ionospheric electric field, currents, and temperature, which greatly impact telecommunication, navigation, and power grids. We discuss one type of ionospheric flow that has been largely overlooked in previous studies and propose a generation mechanism for it. This type of flow may be crucial in magnetospheric plasma circulation, ionospheric heating, and energy transport in the magnetosphere‐ionosphere system. Key Points: Dawnside auroral polarization streams (DAPS) are eastward fast ionospheric flows within the return flow of the dawnside convection cellA DAPS is located within the Region 1 current; it has a flow peak and steep flow gradient near the boundary between Region 1 and 2 currentsA DAPS likely results from enhanced Region 2 current, which occurs during geomagnetically active time [ABSTRACT FROM AUTHOR]

Abstract: Omega bands are curved aurora forms that evolve from a quiet arc located along the poleward edge of a diffuse auroral band within the midnight to morningside auroral oval. They usually propagate eastward. Because omega bands are a significant contributor to an active magnetotail, knowledge about their generation is important for understanding tail dynamics. Previous studies have shown that auroral streamers, footprints of fast flows in the tail, can propagate into omega bands. Such events, however, are limited, and it is still unclear whether and how the flows trigger the bands. The ionospheric flows associated with omega bands may provide valuable information on the driving mechanisms of the bands. We examine these flows taking advantage of the conjunctions between the Swarm spacecraft and Time History of Events and Macroscale Interactions during Substorms all‐sky imagers, which allow us to demonstrate the relative location of the flows to the omega bands' bright arcs for the first time. We find that a strong eastward ionospheric flow is consistently present immediately poleward of the omega band's bright arc, resulting in a sharp flow shear near the poleward boundary of the band. This ionospheric flow shear should correspond to a flow shear near the inner edge of the plasma sheet. This plasma sheet shear may drive a Kelvin‐Helmholz instability which then distorts the quiet arc to form omega bands. It seems plausible that the strong eastward flows are driven by streamer‐related fast flows or enhanced convection in the magnetotail. [ABSTRACT FROM AUTHOR]

The mathematical model of flow shear constitutive relation during rheo-rolling process has been established. The distribution of velocity and shear stress in rolling cavity was investigated, and the effects of process parameters on shear stress of Sn-15Pb alloy during rheo-rolling process were studied. In rolling cavity, the nearer the roll is, the bigger the velocity and shear stress are. The shear stress increases with the increment of the roll speed and the roll radius during rheo-rolling process, but deceases with the increment of the thickness of the strip. When the solid fraction of Sn-15Pb alloy increases from 0.3 to 0.5, the shear stress increases slowly, but when the solid fraction increases from 0.5 to 0.6, the shear stress rapidly. [ABSTRACT FROM AUTHOR]

Abstract: For modeling the rate of deposition of cohesive flocs in estuaries the Krone equation is extensively used. It was derived from flume experiments on muddy sediment from the San Francisco Bay, and is applicable to low suspended sediment concentration environments in which shear-induced aggregation – the growth and break up of flocs – has a limited role. It is shown that the use of this equation can lead to erroneous estimates of the mass deposition flux at typically higher estuarine concentrations. Krone's own experimental data permit the development of a more general equation accounting for the effects of concentration and turbulent shear rate on aggregation. These effects are dramatically observed in a deposition test in which a wire mesh was inserted in the flow to change the turbulent shearing rate and increase deposition. Even with the inclusion of aggregation effect in the general equation, field-based observations from San Francisco Bay suggest that typical flumes generally may not meet the space and time scaling requirements for field application of laboratory data. Thus, although the Krone equation should be eschewed in favor of the general equation, interpretations of model-predicted deposition rate must not be accepted without robust field-based verification. [Copyright &y& Elsevier]

The effects of flow shear on the resistive wall mode (RWM) are numerically studied in a slab geometry. The reversed shear in the plasma flow has a stable effect on the linear evolution of the RWM. On the other hand, the direction of the plasma flow has an effect on the stabilization of the RWM. The field-aligned flow exhibits the strongest suppressing effect. The RWM saturates in the nonlinear phase. The saturation level decreases with increasing of shear rate s. The saturation can be attributed to flux piling-up on the resistive wall. [ABSTRACT FROM AUTHOR]

This research studies dynamic culture for 3D tissue construct development with computational fluid dynamics. It proposes a mathematical model to evaluate the impact of flow rates and flow shear stress on cell growth in 3D constructs under perfusion. The modeling results show that dynamic flow, even at flow rate as low as 0.002 cm/s, can support much better mass exchange, higher cell number, and more even cell and nutrient distribution compared to static culture. Higher flow rate can further improve nutrient supply and mass exchange in the construct, promoting better nutritious environment and cell proliferation compared to lower flow rate. In addition, consideration of flow shear stress predicts much higher cell number in the construct compared to that without shear consideration. While the nutrient can dominate shear stress in influencing cell proliferation, the shear effect increases with flow rate. The proposed model helps tissue engineers better understand the cell-flow relationship at the molecular level during dynamic culture. [ABSTRACT FROM AUTHOR]

In a recent paper, Varischetti et al. (Plasma Phys. Contr. F. 2008, 50, 105008-1-15) have found that in a slab geometry the effect of the flow shear in the field-aligned parallel flow on the linear mode stability of the ion temperature gradient (ITG)-driven modes is not very prominent. They found that the flow shear also has a negligible effect on the mode characteristics. The work in this paper shows that the inclusion of flow curvature in the field-aligned flow can have a considerable effect on the mode stability; it can also change the mode structure so as to effect the mixing length transport in the core region of a fusion device. Flow shear, on the other hand, has indeed an insignificant role in the mode stability and mode structure. Inhomogeneous field-aligned flow should therefore still be considered for a viable candidate in controlling the ITG mode stability and mode structure. [ABSTRACT FROM AUTHOR]

Magnetic reconnection at the high-latitude magnetopause is studied using 2.5-dimensional Hall-MHD simulation. Concentric flow vortices and magnetic islands appear when both Hall effect and sheared flow are considered. Plasma mixing across the magnetopause occurs in the presence of the flow vortices. Reconnected structure generated in the vicinity of the subsolar point changes its geometry with increasing flow shear while moving to high latitudes. In the presence of flow shear, with the Hall-MHD reconnection a higher reconnection rate than with the traditional MHD is obtained. The out-of-plane components of flow and magnetic field produced by the Hall current are redistributed under the action of the flow shear, which makes the plasma transport across the boundaries more complicated. The simulation results provide some help in understanding the dynamic processes at the high latitude magnetopause. [ABSTRACT FROM AUTHOR]

Biophysical cues, such as mechanical properties, play a critical role in tissue growth and homeostasis. During organ development and tissue injury repair, compressive and tensional forces generated by cell-extracellular matrix or cell-cell interaction are key factors for cell fate determination. In the vascular system, hemodynamic forces, shear stress, and cyclic stretch modulate vascular cell phenotypes and susceptibility to atherosclerosis. Despite that emerging efforts have been made to investigate how mechanotransduction is involved in tuning cell and tissue functions in various contexts, the regulatory mechanisms remain largely unknown. One of the challenges is to understand the signaling cascades that transmit mechanical cues from the plasma membrane to the cytoplasm and then to the nuclei to generate mechanoresponsive transcriptomes. YAP and its homolog TAZ, the Hippo pathway effectors, have been identified as key mechanotransducers that sense mechanical stimuli and relay the signals to control transcriptional programs for cell proliferation, differentiation, and transformation. However, the upstream mechanosensors for YAP/TAZ signaling and downstream transcriptome responses following YAP/TAZ activation or repression have not been well characterized. Moreover, the mechanoregulation of YAP/TAZ in literature is highly context-dependent. In this review, we summarize the biomechanical cues in the tissue microenvironment and provide an update on the roles of YAP/TAZ in mechanotransduction in various physiological and pathological conditions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Cai, Wang and Meng.)

Nanoparticles are commonly administered through systemic injection, which exposes them to the dynamic environment of the bloodstream. Injected nanoparticles travel within the blood and experience a wide range of flow velocities that induce varying shear rates to the blood vessels. Endothelial cells line these vessels, and have been shown to uptake nanoparticles during circulation, but it is difficult to characterize the flow-dependence of this interaction in vivo. Here, a microfluidic system is developed to control the flow rates of nanoparticles as they interact with endothelial cells. Gold nanoparticle uptake into endothelial cells is quantified at varying flow rates, and it is found that increased flow rates lead to decreased nanoparticle uptake. Endothelial cells respond to increased flow shear with decreased ability to uptake the nanoparticles. If cells are sheared the same way, nanoparticle uptake decreases as their flow velocity increases. Modifying nanoparticle surfaces with endothelial-cell-binding ligands partially restores uptake to nonflow levels, suggesting that functionalizing nanoparticles to bind to endothelial cells enables nanoparticles to resist flow effects. In the future, this microfluidic system can be used to test other nanoparticle-endothelial cell interactions under flow. The results of these studies can guide the engineering of nanoparticles for in vivo medical applications., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Multi‐geometry nanostructures with high‐order, complex, and controllable geometries have attracted extensive attention in the development of functional nanomaterials. A simple and versatile strategy is proposed to construct various anisotropic nanostructures through the directed self‐assembly (DSA) of patchy microgels. A general criterion for interaction parameters is developed by the variance analysis method to achieve the formation of 1D nanorods by the single directional DSA process, and 2D or 3D polymorphs including V/T/h/cross shapes, multiple arms, multi‐directional bending, single/multiple rings, nanocages, etc., by the multi‐directional DSA process of binary microgel blends. At the optimum interaction parameters, the nanorods exhibit the quickest formation process and the most thermodynamically stable geometry, while the various 2D or 3D assemblies exhibit controlled jointing behaviors for versatile assembly geometries. The number of recognition sites on the patchy microgel surface guides the aggregation modes of microgels during the DSA process. These assemblies can bear large curvature variance with the increase of shear rates due to the high flexibility and the ability of adjusting orientation spontaneously. The DSA behavior of patchy microgels differs from the traditional self‐assembly process of block copolymers, which may open a new route for guiding the formation of controllable nanoparticle architectures. [ABSTRACT FROM AUTHOR]