Local Constriction Research Articles

Viscous shear is a key force in Drosophila ventral furrow morphogenesis.

Ventral furrow (VF) formation in Drosophila melanogaster is an important model of epithelial folding. Previous models of VF formation require cell volume conservation to convert apically localized constriction forces into lateral cell elongation and tissue folding. Here, we investigated embryonic morphogenesis in anillin knockdown (scra RNAi) embryos, where basal cell membranes fail to form and therefore cells can lose cytoplasmic volume through their basal side. Surprisingly, the mesoderm elongation and subsequent folding that comprise VF formation occurred essentially normally. We hypothesized that the effects of viscous shear may be sufficient to drive membrane elongation, providing effective volume conservation, and thus driving tissue folding. Since this hypothesis may not be possible to test experimentally, we turned to a computational approach. To test whether viscous shear is a dominant force for morphogenesis in vivo, we developed a 3D computational model incorporating both accurate cell and tissue geometry and experimentally measured material parameters. Results from this model demonstrate that viscous shear generates sufficient force to drive cell elongation and tissue folding in vivo.

Structure, Thermodynamics, Chemomechanics, and Kinetics: The Hidden Complexities of LiNiO2

After being abandoned due to mechanical and thermodynamic instabilities, layered transition metal oxides with ultra-high Ni content currently see a revival as promising cathode active material in the effort of further pushing the energy density of lithium ion batteries. Because such materials are in many aspects closely related to the pure LiNiO2, understanding the properties and mechanisms of this model system on an atomic level is vital for the development of more complex materials. Therefore, we have analyzed the structure, thermodynamics, chemomechanics and kinetics of LiNiO2 and its delithiated states including the presence of native defects by making use of atomistic simulations to grasp the peculiarities of this material.What makes the structure and related properties of LiNiO2 especially interesting and challenging is the presence of dynamic Jahn-Teller distortions of the NiO6 octahedra. This leads to local monoclinic distortions and our simulations revealed why the material still appears to be of rhombohedral symmetry on a global scale.[1]Upon delithiation and the concurrent oxidation to Ni4+, the Jahn-Teller distortions start to vanish and particularly stable Li orderings may be observed. In this context, we used a cluster expansion approach and were able to reproduce the experimental phase diagram. Moreover, we included native defects in the analysis because LiNiO2 can hardly be prepared stoichiometric. Instead, many synthesis approaches lead to additional Ni ions occupying the Li layers (NiLi). The introduction of such defects as well as other substitutionals in a surrogate model shows that single phase regions tend to be suppressed and solid-solution behavior is favored. This smooths the voltage curves and gives good agreement with experiments.[2]We then focused on more extended defects in layered transition metal oxides: Stacking faults (observed at low Li content and responsible for stacking changes from O3 to O1-type layering) and dislocations (needed to drive stacking changes through the material). We found that the energetics and gliding barriers of stacking faults in stoichiometric LiNiO2 are similar to LiCoO2 for all degrees of lithiation. However, by acknowledging the presence of NiLi we quantified for the first time how this defect hinders layer gliding: In the fully delithiated material, 2% of NiLi in the Li layer has a similar effect as 11%-15% Li, effectively increasing the gliding barriers. In terms of dislocations, their excess energies in LiNiO2 are much lower than in LiCoO2, which we mostly attribute to the Jahn-Teller distortions that are able to collinearly orient in the vicinity of a dislocation in LiNiO2, effectively taking a part of the strain. Moreover, dislocations are able to attract both Li and O vacancies, potentially affecting the kinetics of the material as well as acting as a precursor for further degradation mechanisms.[3]Lastly, we mention our recent analysis again focusing on NiLi defects. Our simulations show that such Ni ions remain in a +2 oxidation state independent on the degree of lithiation. This contradicts the broad opinion of an oxidation state change to +3 at low Li content, which is believed to lead to a local constriction of the layer that can hardly be relithiated again. Nevertheless, we show that NiLi indeed leads to an attraction of Li vacancies within two lattice sites and the potential to split fast divacancies into two considerably slower single vacancies. These observations together with the fact that any NiLi depicts an obstacle for diffusing Li ions or Li vacancies shed light on the kinetics of non-stoichiometric LiNiO2 and support the development of further optimization schemes.[4][1] Chem. Mater. 2020, 32, 23, 10096–10103[2] J. Mater. Chem. A , 2021,9, 14928-14940[3] Chem. Mater. 2023, 35, 2, 584–594[4] https://doi.org/10.26434/chemrxiv-2023-hkmsn-v3

SCARY ECG IN TAKOTSUBO CARDIOMYOPATHY

Abstract Takotsubo cardiomyopathy (TTC) is characterized by a transient ventricular wall motion abnormality and shares common features with acute coronary syndrome (ACS) with a wide spectrum of triggers, such as both emotional or physical, activating common toxic catecholamines–mediated pathways. TTC might be associated with severe clinical complications. We report a case of a 74–year female patient with circulatory shock with mixed phenotype, distributive due to sepsis and cardiogenic due to TTC. The patient presented to the emergency department with severe hypotension, pathological qSOFA score and clinical and laboratory findings consistent with severe sepsis. ECG showed diffuse lambda ST–segment elevation, also called “shark fin”(fig.1). According to hemodynamically unstable scenario and ECG pattern, emergency coronary angiography was performed, showing absence of coronary artery disease(fig. 2). Echocardiography revealed severe LV systolic disfunction (EF 20–25%) with apical ballooning and severe systolic anterior motion (SAM) of the anterior mitral leaflet eliciting dynamic LVOTO with peak gradient greater than 90 mmHg; fig. 3) and severe MR. Patient was treated with cautious fluid administration, hemotrasfusion and empiric large spectrum antibiotic therapy. According to TTC working diagnosis, even if septic state was thought to contribute to cardiogenic shock, norepinephrine was not administered due to concerns for LVOTO and SAM. After overcoming of dramatic first phase and after hemodynamic steadiness was achieved, beta blockade and ACEi were progressively administered. Seriate transthoracic echocardiogram revealed progressive improvement of LV systolic function, regression of apical ballooning, SAM and LVOTO. ECG monitoring showed regression of ischemic ST elevation. ST elevation has been described in about 56% of TTC cases, however with amplitude tipically lower than in STEMI. Lambda–wave ST elevation has been rarely reported. Vasospasm, local intermittent microvascular constriction, catecholamine–induced metabolic toxicity, transmural systolic wall tension and its the mechano–electric feedback can explain scaring ECG–pattern. Despite its rare prevalence in TTC “shark fin” pattern appears to relate to adverse outcome and it should be used as an early marker of potential further clinical deterioration, suggesting more intensive monitoring to avoid delays in possible therapy escalation.

Cerebral Artery Overexpression of the NMUR1 Gene Is Associated with Moyamoya Disease: A Weighted Gene Co-Expression Network Analysis

Introduction: This study aimed to elucidate mechanisms underlying moyamoya disease (MMD) pathogenesis and to identify potential novel biomarkers. We utilized gene co-expression networks to identify hub genes associated with the disease. Methods: Twenty-one middle cerebral artery (MCA) samples from MMD patients and 11 MCA control samples were obtained from the Gene Expression Omnibus (GEO) dataset, GSE189993. To discover functional pathways and potential biomarkers, weighted gene co-expression network analysis (WGCNA) was employed. The hub genes identified were re-assessed through differential gene expression analysis (DGEA) via DESeq2 for further reliability verification. Additional 4 samples from the superficial temporal arteries (STAs) from MMD patients were obtained from GSE141025, and a subgroup analysis stratified by arterial type (MCA vs. STA) DGEA was performed to assess if the hub genes associated with MMD are expressed significantly greater on the affected arteries compared to healthy ones in MMD. Results: WGCNA revealed a predominant module encompassing 139 hub genes, predominantly associated with the neuroactive ligand-receptor interaction (NLRI) pathway. Of those, 17 genes were validated as significantly differentially expressed. Neuromedin U receptor 1 (NMUR1) and thyrotropin-releasing hormone were 2 out of the 17 hub genes involved in the NLRI pathway (log fold change [logFC]: 1.150, p = 0.00028; logFC: 1.146, p = 0.00115, respectively). MMD-only subgroup analysis stratified by location showed that NMUR1 is significantly overexpressed in the MCA compared to the STA (logFC: 1.962; p = 0.00053) which further suggests its possible localized involvement in the progressive stenosis seen in the cerebral arteries in MMD. Conclusion: This is the first study to have performed WGCNA on samples directly affected by MMD. NMUR1 expression is well known to induce localized arterial smooth muscle constriction and, recently, type 2 inflammation which can predispose to arterial stenosis potentially advancing the symptoms and progression of MMD. Further validation and functional studies are necessary to understand the precise role of NMUR1 upregulation in MMD and its potential implications.

DEM and DEM-CFD modeling of systems with geometric constrictions using a new particle location based multi-level coarse graining approach

A popular Lagrangian approach for modeling granular systems is the discrete element method (DEM). Currently, the simulation of industrial granular systems often exceeds modern computer capacities. Therefore, the coarse graining (CG) approach bundles multiple particles into grains, which are less computationally demanding due to the reduced number of entities considered. In systems, where the maximum grain size is limited by local geometry constrictions, uniform grain sizes lead to inefficient computations since far from the constrictions larger grain sizes could be reasonably used. Multi-level coarse graining (MCG) addresses this by using multiple grain sizes, which are adapted to the geometric constrictions. In this study, geometrical non-uniform hoppers and a Wurster coater system were modeled using a new MCG approach. Results from literature regarding hopper discharge were matched. For the Wurster coater system MCG outperforms conventional CG by providing a higher resolution of the granular material close to the geometric constriction.

Solute translocation probability, lifetime, and "rectification" in membrane channels with localized constriction.

We study the translocation probability and lifetime of a solute molecule in a cylindrical membrane channel that contains a localized constriction at an arbitrary location. Using a one-dimensional continuous diffusion description of solute dynamics in the channel, we explore two models. The first one describes a molecule's interaction with the constriction in terms of a narrow rectangular barrier in the potential of mean force. The second novel model proposed here represents this interaction by introducing an infinitely thin permeable partition. It is shown that when the parameters of the two models are chosen to warrant the same translocation probability, both models predict the same mean lifetime of the molecule in the channel. While the translocation probability is independent of the constriction location, the mean lifetime is a function of the location. The benefit of the thin partition model is that it allows one to lump together the height and length of the potential barrier into a single parameter, which is the partition's permeability. It is shown that in the case of an asymmetric location of the localized constriction and strong repulsion between the solutes, the solute flux through the channel is a function of the direction in which it goes, analogous to the phenomenon known in ion channel electrophysiology as rectification.

Transport of Steam-Gas Mixture in Hydrodynamic Devices: A Numerical Study of Steam Reforming of Methane

The paper introduces a mathematical model that describes the cavitation process occurring during the passage of a water steam flow in various geometric configurations of a hydrodynamic device. The flow experiences a localized constriction (convergent nozzle) followed by expansion (divergent nozzle), exemplified by a Venturi tube or a Laval nozzle. A narrow flow channel connecting the convergent and divergent sections is equipped with a narrow-section nozzle for injecting methane molecules into the high-speed steam flow. As the steam-gas mixture passes through this zone, it is irradiated with an electron beam and sprayed into a cylindrical chamber at atmospheric pressure, where the distribution of methane molecules in water vapor forms an aerosol. Key geometric parameters of the constriction and expansion zones of the hydraulic system (cavitation-jet chamber) are determined to ensure the uniform distribution of dispersed-phase particles (methane) in the dispersion medium (water vapor). Velocity and pressure distributions of the mixed steam-gas flow are calculated using a turbulent mathematical model, specifically the k-ω model, while the motion of methane particles is simulated using a particle tracing method. The uniformity of methane molecule distribution in water vapor is assessed using Ripley’s K-function. The best performance of the hydrogen-producing chamber was observed when the cavitation-inducing nozzle’s convergence angle exceeded 50 degrees. The divergence angle of the nozzle within the range of 30–40 degrees provided the best distribution in terms of uniformity of the methane particles in the chamber.

Effects of vacancy concentration on the edge dislocation motion in copper by atomic simulations

Nonequilibirum vacancy concentration widely appears in crystals under many extreme loading conditions, but receives relatively few attentions. In this work, we systematically explore the influence of a serial of different vacancy concentrations on the edge dislocation motion in copper using molecular dynamics (MD) simulations. Our result shows that the vacancy would hinder the dislocation motion, but the mechanism depends on the detailed dislocation motion regions. In thermally activated region, its influence is mainly reflected by modifying the dynamic and static threshold stresses required for edge dislocation initiation and continuous motion. In the linear region, the hindering mechanism is gradually transformed from phonon damping to vacancy pinning with the increasing vacancy concentration. In contrasts, the dislocation structure is almost unchanged under different vacancy concentrations in the non-linear region. Under high applied stress, high vacancy concentration will cause the dislocation velocity to jump back and forth between transonic and subsonic velocities more frequently. It has been attributed to the reactions between the dislocation and vacancies. The latter may result in dislocation local constriction and climbing. Moreover, a mobility equation suitable for describing edge dislocations at different non-equilibrium vacancy concentrations is proposed, which fits the MD results well. Finally, the roles of the nonequilibirum vacancy concentration on the edge dislocation motion is interpreted using the degrading elastic property and stacking fault energy.

Macropinocytosis: Blowing bubbles

Macropinocytosis is a form of endocytosis in which cells engulf relatively large quantities of extracellular fluid through cup-shaped invaginations of the plasma membrane. New work shows that macropinosome closure occurs without a localized constriction of actin filaments, indicating that membrane tension drives cup closure.

A Fully Integrated Pipeline for Visual Carotid Morphology Analysis

AbstractAnalyzing stenoses of the internal carotids – local constrictions of the artery – is a critical clinical task in cardiovascular disease treatment and prevention. For this purpose, we propose a self‐contained pipeline for the visual analysis of carotid artery geometries. The only inputs are computed tomography angiography (CTA) scans, which are already recorded in clinical routine. We show how integrated model extraction and visualization can help to efficiently detect stenoses and we provide means for automatic, highly accurate stenosis degree computation. We directly connect multiple sophisticated processing stages, including a neural prediction network for lumen and plaque segmentation and automatic global diameter computation. We enable interactive and retrospective user control over the processing stages. Our aims are to increase user trust by making the underlying data validatable on the fly, to decrease adoption costs by minimizing external dependencies, and to optimize scalability by streamlining the data processing. We use interactive visualizations for data inspection and adaption to guide the user through the processing stages. The framework was developed and evaluated in close collaboration with radiologists and neurologists. It has been used to extract and analyze over 100 carotid bifurcation geometries and is built with a modular architecture, available as an extendable open‐source platform.

Bed Stability of Step‐Pool Channels With Macrorough Sidewalls

AbstractA step‐pool bed morphology often develops in steep mountain streams. The main controlling parameters of step formation and stability are hydraulic forcing, sediment transport, and granular effects (i.e., grain‐grain interlocking, jamming). Previous studies found macrorough sidewalls to further increase bed stability due to grain‐sidewall interlocking but the effect of the reduced bed shear stress caused by sidewall friction was not explicitly considered. The present study aims at untangling hydraulic effects induced by the macrorough sidewalls and granular effects, that is, grain‐sidewall interaction. Flume experiments with five types of macrorough sidewalls were conducted under clear‐water conditions for bed slopes ranging between 4% and 10% and jamming ratios 5.3 < Wm/d84 < 11.2, where Wm is the mean channel width and d84 is a characteristic grain size of the sediment mixture. A modified sidewall correction procedure accounting for sidewall friction was applied to estimate bed shear stress. Bed stability considerably increased with increasing sidewall roughness. The dimensionless bed shear stress θRb controlled step occurrence as the system evolved toward a state of a maximum number of steps for critical Shields ratios θRb/θc ≈ 1. Contrary to the expectations, fewer steps formed in the roughest sidewall experiments as few very stable steps inhibited sediment relocation and therewith step formation. Steps were more frequently located in the constrictions caused by the macrorough elements and sustained higher bed shear stress increments. Overall, hydraulic effects fully explained the increase in bed stability in moderately rough sidewall experiments whereas granular effects became important in channels with strong local constrictions.

Decision Support Tool for the Optimal Sizing of Solar Irrigation Systems

Solar photovoltaic (PV) irrigation is increasingly used in agriculture, driven by its low operation cost and virtually zero emissions, providing electricity access in rural areas. However, the high investment cost requires an optimal design. The objective of this work was to develop a user-friendly tool to optimally size a PV generator that satisfies crop irrigation needs under local constrictions. The ODSIS (Optimal Design of Solar Irrigation System) tool, was organized in three calculation modules, preceded by two complements, which determine the daily crop irrigation needs and power demand of the pumping system. Then, the first module sizes the PV plant, considering a multiplication factor, and provides the PV production potential throughout each day of the season. The second and third modules evaluate the total investment cost and equivalent greenhouse gas emissions avoided by comparison with traditional energy sources. This tool was applied to a case study in Senegal for which a multiplication factor of 1.4 was obtained for the optimal PV plant size. Between 22% to 64% of the investment cost corresponded to the PV pumping system, depending on the irrigation technique. The use of PV energy in the case study would represent an annual economic saving for the farmer after 5 to 8 years of payback period, avoiding the emission of between 29.8 and 37.9 tCO2eq/year for the case study area.

Double diffusive instability with a constriction

Confined geometries have an effect on hydrodynamic instabilities, and this provides opportunities for controlling the rate of mixing in flows of engineering relevance. In multi-component fluids, differential diffusion allows for novel types of hydrodynamic instability that have finite amplitude manifestations even in millimeter-scale channels. We present numerical simulations that demonstrate that localized channel constrictions can serve to partially “catch” the manifestations of double diffusive instabilities. The fluid collects just above the narrowest point of the constriction and eventually undergoes a secondary instability. We study this secondary instability, focusing on its chaotic nature and on the way in which flow into the region below the constriction is controlled by the constriction amplitude and shape.

Curvature gradient drives polarized tissue flow in the Drosophila embryo

Tissue flow during morphogenesis is commonly driven by local constriction of cell cortices, which is caused by the activation of actomyosin contractility. This can lead to long-range flows due to tissue viscosity. However, in the absence of cell-intrinsic polarized forces or polarity in forces external to the tissue, these flows must be symmetric and centered around the region of contraction. Polarized tissue flows have been previously demonstrated to arise from the coupling of such contractile flows to points of increased friction or adhesion to external structures. However, we show with experiments and modeling that the onset of polarized tissue flow in early Drosophila morphogenesis occurs independent of adhesion and is instead driven by a geometric coupling of apical actomyosin contractility to tissue curvature. Particularly, the onset of polarized flow is driven by a mismatch between the position of apical myosin activation and the position of peak curvature at the posterior pole of the embryo. Our work demonstrates how genetic and geometric information inherited from the mother interact to create polarized flow during embryo morphogenesis.

Interaction between Movement Proteins of Hibiscus green spot virus.

Movement proteins (MPs) of plant viruses enable the translocation of viral genomes from infected to healthy cells through plasmodesmata (PD). The MPs functions involve the increase of the PD permeability and routing of viral genome both to the PD entrance and through the modified PD. Hibiscus green spot virus encodes two MPs, termed BMB1 and BMB2, which act in concert to accomplish virus cell-to-cell transport. BMB1, representing an NTPase/helicase domain-containing RNA-binding protein, localizes to the cytoplasm and the nucleoplasm. BMB2 is a small hydrophobic protein that interacts with the endoplasmic reticulum (ER) membranes and induces local constrictions of the ER tubules. In plant cells, BMB2 localizes to PD-associated membrane bodies (PAMBs) consisting of modified ER tubules and directs BMB1 to PAMBs. Here, we demonstrate that BMB1 and BMB2 interact in vitro and in vivo, and that their specific interaction is essential for BMB2-directed targeting of BMB1 to PAMBs. Using mutagenesis, we show that the interaction involves the C-terminal BMB1 region and the N-terminal region of BMB2.

3D optogenetic control of arteriole diameter in vivo.

Modulation of brain arteriole diameter is critical for maintaining cerebral blood pressure and controlling regional hyperemia during neural activity. However, studies of hemodynamic function in health and disease have lacked a method to control arteriole diameter independently with high spatiotemporal resolution. Here, we describe an all-optical approach to manipulate and monitor brain arteriole contractility in mice in three dimensions using combined in vivo two-photon optogenetics and imaging. The expression of the red-shifted excitatory opsin, ReaChR, in vascular smooth muscle cells enabled rapid and repeated vasoconstriction controlled by brief light pulses. Two-photon activation of ReaChR using a spatial light modulator produced highly localized constrictions when targeted to individual arterioles within the neocortex. We demonstrate the utility of this method for examining arteriole contractile dynamics and creating transient focal blood flow reductions. Additionally, we show that optogenetic constriction can be used to reshape vasodilatory responses to sensory stimulation, providing a valuable tool to dissociate blood flow changes from neural activity.

A numerical technique to solve a problem of the fluid motion in a straight plane rigid duct with two axisymmetric rectangular constrictions. An alternative approach

A numerical technique is devised to solve a problem of the steady laminar fluid motion in a straight plane hard-walled duct with two local axisymmetric rectangular constrictions. It uses the stream function, the vorticity and the pressure as the basic variables, has the second order of accuracy in the spatial and the first order of accuracy in the temporal coordinates, provides high stability of a solution, and needs significantly less computational time to obtain a result compared to appropriate techniques available in a scientific literature. The technique consists in: a) introducing the stream function and the vorticity, and subsequent transiting from the non-dimensional governing relations for the fluid velocity and the pressure to the corresponding non-dimensional relations for the stream function, the vorticity and the pressure; b) deriving their discrete counterparts in the nodes of the chosen space-time computational grid; c) integrating the systems of linear algebraic equations obtained after making the discretization. The discretization is based on applying appropriate differencing schemes to the terms of the equations for the basic variables. These are the two-point temporal onward difference for the unsteady term of the vorticity equation, as well as the two-point backward differences (for its convective term) and the five-point approximations (for its diffusive term and for the Poisson’s equations for the stream function and the pressure) in the axial and cross-flow coordinates. As for the velocity components, the appropriate central differences are applied to discretize their expressions. The above-mentioned systems of linear algebraic equations for the stream function and the pressure are integrated by the iterative successive over-relaxation method. The algebraic relation for the vorticity does not need application of any method to be solved, because it is a computational scheme to find this quantity based on the known magnitudes computed at the previous instant of time.

Simulation of a pulsating flow in a pipe with local constrictions as applied to hemodynamics of blood vessels

Simulation of a pulsating flow in a pipe with local constrictions as applied to hemodynamics of blood vessels

Evidence for a Role of the Lateral Ectoderm in Drosophila Mesoderm Invagination.

The folding of two-dimensional epithelial sheets into specific three-dimensional structures is a fundamental tissue construction mechanism in animal development. A common mechanism that mediates epithelial folding is apical constriction, the active shrinking of cell apices driven by actomyosin contractions. It remains unclear whether cells outside of the constriction domain also contribute to folding. During Drosophila mesoderm invagination, ventrally localized mesoderm epithelium undergoes apical constriction and subsequently folds into a furrow. While the critical role of apical constriction in ventral furrow formation has been well demonstrated, it remains unclear whether, and if so, how the laterally localized ectodermal tissue adjacent to the mesoderm contributes to furrow invagination. In this study, we combine experimental and computational approaches to test the potential function of the ectoderm in mesoderm invagination. Through laser-mediated, targeted disruption of cell formation prior to gastrulation, we found that the presence of intact lateral ectoderm is important for the effective transition between apical constriction and furrow invagination in the mesoderm. In addition, using a laser-ablation approach widely used for probing tissue tension, we found that the lateral ectodermal tissues exhibit signatures of tissue compression when ablation was performed shortly before the onset of mesoderm invagination. These observations led to the hypothesis that in-plane compression from the surrounding ectoderm facilitates mesoderm invagination by triggering buckling of the mesoderm epithelium. In support of this notion, we show that the dynamics of tissue flow during mesoderm invagination displays characteristic of elastic buckling, and this tissue dynamics can be recapitulated by combining local apical constriction and global compression in a simulated elastic monolayer. We propose that Drosophila mesoderm invagination is achieved through epithelial buckling jointly mediated by apical constriction in the mesoderm and compression from the neighboring ectoderm.

RapidQ: A reader-free microfluidic platform for the quantitation of antibodies against the SARS-CoV-2 spike protein.

We describe RapidQ, a fast, disposable, easy-to-use microfluidic assay for the quantitation of the anti-SARS-CoV-2 spike (S) protein IgG in plasma samples. The assay utilizes antigen-coated paramagnetic microbeads, which are induced to aggregate inside the RapidQ microfluidic device in the presence of the target antibody. Aggregation occurs via interaction between the biotinylated detection antibody and polymeric streptavidin. The mobility of the beads inside the two microchannels of the device depends on their aggregation state, with larger clusters moving at higher velocities under a given liquid flow rate. One of the microchannels incorporates a permanent magnet that captures arriving beads and forms a localized constriction that retards liquid flow. Since the constriction grows faster when the beads are more aggregated, the length of the liquid column accumulated downstream from the constriction relative to that of the unconstricted control channel is proportional to the sample antibody concentration. The assay demonstrates a detection limit of 4 μg/ml of monoclonal anti-S protein antibody diluted in plasma with CV ≤ 13%, as well as negative and positive percent agreements of 100% (95% CI: 92.75%-100%) and 100% (95% CI: 80.5%-100%), respectively, when compared to a nucleic acid amplification test used to identify COVID-19 positive individuals, whose samples were collected ≥17 d from a positive PCR test. Finally, the RapidQ assay was used to monitor the kinetics of antibody responses to COVID-19 vaccination in a small study cohort.