Fluid Movement Research Articles

Subsurface microbial community structure shifts along the geological features of the Central American Volcanic Arc.

Subduction of the Cocos and Nazca oceanic plates beneath the Caribbean plate drives the upward movement of deep fluids enriched in carbon, nitrogen, sulfur, and iron along the Central American Volcanic Arc (CAVA). These compounds fuel diverse subsurface microbial communities that in turn alter the distribution, redox state, and isotopic composition of these compounds. Microbial community structure and functions vary according to deep fluid delivery across the arc, but less is known about how microbial communities differ along the axis of a convergent margin as geological features (e.g., extent of volcanism and subduction geometry) shift. Here, we investigate changes in bacterial 16S rRNA gene amplicons and geochemical analysis of deeply-sourced seeps along the southern CAVA, where subduction of the Cocos Ridge alters the geological setting. We find shifts in community composition along the convergent margin, with communities in similar geological settings clustering together independently of the proximity of sample sites. Microbial community composition correlates with geological variables such as host rock type, maturity of hydrothermal fluid and slab depth along different segments of the CAVA. This reveals tight coupling between deep Earth processes and subsurface microbial activity, controlling community distribution, structure and composition along a convergent margin.

Dysregulated Neurofluid Coupling as a New Noninvasive Biomarker for Primary Progressive Aphasia.

Accumulation of pathological tau is one of the primary causes of Primary Progressive Aphasia (PPA). The glymphatic system is crucial for removing metabolite waste from the brain whereas impairments in glymphatic clearance in PPA are poorly understood. Thus, this study aims to investigate the role of dysregulated macroscopic cerebrospinal fluid (CSF) movement in PPA. Fifty-six PPA individuals and ninety-four healthy controls were included in our analysis after excluding those with excessive head motions during the scan. The coupling strength between blood-oxygen-level-dependent (BOLD) signals in the gray matter and CSF flow was calculated using Pearson correlation and compared between the groups. Its associations with clinical characteristics including scores from Clinical Dementia Rating (CDR), Mini-Mental State Exam, Geriatric Depression Scale and with morphological measures in the hippocampus and entorhinal cortex were examined. PPA subjects exhibited weaker global BOLD-CSF coupling compared to HCs, indicating impairments in glymphatic function in the patients (p = 0.01). In the PPA but not HC group, global BOLD-CSF coupling correlated with the CDR scores (p = 0.04) and hippocampal volume (p = 0.009). The observed decoupling between global brain activity and CSF flow and its association with symptomatology and brain structural changes in PPA converges with previous reports on the same measure in other neurodegenerative diseases. These findings support the potential role of global BOLD-CSF coupling as a noninvasive marker for glymphatic dysregulation in PPA.

Parametric influences on flow, heat transfer, and nutrient transport in the knee joint cavity, a numerical approach

A novel aspect of this study is the investigation of the impact of temperature-dependent Arrhenius reactions and metabolic heat generation on the overall heat transfer within a knee joint cavity. This is a unique contribution where the interaction between thermal effects and metabolic activity is shown to influence the transport of nutrients and the removal of waste products. For the first time, the study also aims to examine the influence of key non-dimensional numbers on the characteristics of mixed convection flow, providing new insights into the dominant physical mechanisms at play. An innovative feature of the model is the incorporation of a non-linear reaction term to address the balance between protein synthesis and degradation. By integrating both thermal and biochemical dynamics, this approach offers a comprehensive analysis of protein aggregation in the knee joint, with potential implications for understanding and treating joint diseases, particularly those related to the health of synovial fluid and cartilage, such as osteoarthritis. The findings have the potential to inform the development of improved therapeutic strategies for managing these conditions. In the context of knee joint cavity dynamics, a low Cauchy number Ca plays a crucial role in ensuring steady and laminar flow, which reduces inertia and ensures that the continuity equation is satisfied. This laminar nature of the flow is essential for maintaining stable synovial fluid movement within the cavity, which aids in the smooth transport of nutrients and waste products. Additionally, higher Peclet number Pe values indicate an increased dominance of convective transport over diffusion, thereby enhancing the supply of essential nutrients to cartilage and bone, while also facilitating the removal of waste products and inflammatory mediators. This efficient convective transport mechanism is vital for the overall health of the joint and for mitigating inflammation. Furthermore, the Zeldovich number β significantly influences the temperature sensitivity of the Arrhenius reaction term within the cavity, where higher values reflect increased reactivity to temperature changes. This temperature dependence impacts metabolic heat generation and protein dynamics, further influencing the biochemical processes that occur within the joint. Collectively, these non-dimensional parameters highlight key aspects of synovial fluid dynamics, nutrient transport, and biochemical reactions that are essential to the functioning and health of the knee joint.

Optic disc pit maculopathy: Covering or filling technique with human amniotic membrane patch to treat the optic disc pit maculopathy?

To describe two patients affected by optic disk pit-maculopathy ODP-M surgically treated with pars-plana vitrectomy (PPV) and the apposition of a human Amniotic Membrane (hAM) patch. Patients underwent a PPV with the apposition of a hAM patch to cover the ODP. In case 1, a 2nd surgery was necessary to push the hAM patch inside the pit, whereas in case 2 the patch was pulled inside the pit following the pressure gradient when infusion was turned on. After surgery the hAM patch filled the ODP and in both cases, during follow-up, there was a progressive reduction of macular OCT changes and a concomitant BCVA improvement. Our experience seems to support the idea that the dynamic fluctuation of pressure between intra-ocular and intra-cranial spaces can direct the movement of fluid through the anomalous communication created by the ODP. In this perspective, our cases seem to support the idea that the primary goal of any surgery should be to create a permanent barrier to fluid migration through the ODP to the intra-ocular space, and that hAM can be successfully used to fill the OPD and to create that permanent barrier to achieve the resolution of ODP-M.

An Analytical Exploration of Low Reynolds Number Cilia-Driven Flow of Johnson-Segalman Fluid with Heat Transfer Effects

This article discusses the properties of heat transfer on Johnson-Segalman fluids in a complex wavy channel made of metachronal wavy cilia. Such complex wall structures can be used in the design of biomimetic systems. The movement of fluid through a two-dimensional complex wave channel produced by the metachronal wave of cilia is characterized as laminar and incompressible. Firstly, the system of equations is transformed from a fixed frame of reference to a wavy frame of reference. Secondly, the system of equations of motion (EOM) is transformed into a non-dimensional form by using the scaling factors. Mathematical analysis has been conducted using long wavelength as well as low Reynold numbers assumptions. The Perturbation approach is used to solve the simplified governing equations for the axial velocity, temperature, stream function, pressure rise, and heat transfer coefficients. The equations representing axial velocity, pressure rise, and the streaming function are illustrated, and the reason for observed changes in different physical aspects are explained using basic theoretical principles. A solution for small values of the Weissenberg numbers is generated for the resulting nonlinear system. The current study investigates the effects of different boundaries and rheology on fluid flow.The velocity profile increases near the channel center with higher Q (time-mean flow rate) and e¯ (slip parameter), but decreases with greater Weissenberg number (We). The Brinkman number (Br), Q, and e¯ directly influence the temperature distribution, while We have the opposite effect. The size and number of trapped boluses increase with higher Q but decrease with rising We and e¯. It is noteworthy that the overall number of trapped zones rises throughout the complex wavy path.

Metallogenic model of sandstone-hosted copper deposits: a case study from the Paleogene in Jiashi area, northwestern China

Sandstone-hosted copper deposits, a type of Sediment-Hosted Stratiform Copper (SSC) deposits, are widely distributed globally. While economically viable deposits of SSC are relatively scarce, they account for approximately 30 % of the world's total discovered copper resources. However, there is still a lack of comprehensive and in-depth research into the depositional and metallogenic models of these deposits. The Jiashi area of the Tarim Basin in northwestern China, known for its economically significant Paleogene SSC deposit, lacks in-depth studies on metallogenic processes. To address this, field profile observations were conducted to analyze the sedimentary evolution, sequence stratigraphy, and tectonism of the Paleogene strata in the Jiashi area. Combined with elemental geochemical analysis of samples, the provenance of sediment, and the source of metallogenic materials, a robust metallogenic model was established. The results reveal the influence of provenance for the origin of Paleogene copper-rich strata. Sedimentary evolution played a crucial role in controlling the distribution of copper and sulfur elements, as well as the spatial arrangement of metallogenic beds. Additionally, nappe movement potentially generated faults, allowing upward movement of basin fluids, which played a crucial role in the formation of copper deposits within sandstone-hosted systems. Thus, this study offers a comprehensive analysis of the metallogenic processes involved in sandstone-hosted copper deposits, thereby contributing significant insights to the broader research on SSC deposits worldwide.

The periaxonal space as a conduit for cerebrospinal fluid flow to peripheral organs

Mechanisms controlling the movement of the cerebrospinal fluid (CSF) toward peripheral nerves are poorly characterized. We found that, in addition to the foramina Magendie and Luschka for CSF flow toward the subarachnoid space and glymphatic system, CSF outflow could also occur along periaxonal spaces (termed "PAS pathway") from the spinal cord to peripheral organs, such as the liver and pancreas. When interrogating the latter route, we found that serotonin, acting through 5-HT2B receptors expressed in ependymocytes that line the central canal, triggered Ca2+ signals to induce polymerization of F-actin, a cytoskeletal protein, to reduce the volume of ependymal cells. This paralleled an increased rate of PAS-mediated CSF redistribution toward peripheral organs. In the liver, CSF was received by hepatic stellate cells. CSF efflux toward peripheral organs through the PAS pathway represents a mechanism dynamically connecting the nervous system with the periphery. Our findings are compatible with the traditional theory of CSF efflux into the glymphatic system to clear metabolic waste from the cerebral parenchyma. Thus, we extend the knowledge of CSF flow and expand the understanding of connectivity between the CNS and peripheral organs.

Forced flow reversal in ferrofluidic Couette flow via alternating magnetic field

Time-dependent boundary conditions are very common in natural and industrial flows and by far no exception. An example of this is the movement of a magnetic fluid forced due to temporal modulations. In this study, we used numerical methods to examine the dynamics of ferrofluidic wavy vortex flows (WVF2, with dominant azimuthal wavenumber m=2) in the counter-rotating Taylor–Couette system, which was subjected to time-periodic modulation/forcing in a spatially homogeneous magnetic field. In the absence of a magnetic field, all WVF2 states move in the opposite direction to the rotation of the inner cylinder, they are retrograde. However, when strength or frequency of the alternating magnetic field increases, the motion direction of the flow pattern changes. Thus, the alternating field provides a precise and controllable key parameter for triggering the system response and controlling the flow. Aside, we also observed intermittent behavior when one solution became unstable, leading to random transitions in both, the transition time and toward the different final solutions. Our findings suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which may have applications in the development of modern fluid devices in laboratory experiments. These findings provide a framework to study other types of magnetic flows driven by time-dependent forcing.

Geometric flow control in lateral flow assays: Macroscopic two-phase modeling

Lateral flow assays (LFAs) are widely employed in a diverse range of applications, including clinical diagnostics, pharmaceutical research, forensics, biotechnology, agriculture, food safety, and environmental analysis. A pivotal component of LFAs is the porous polymeric membrane, which facilitates the capillary-driven movement of fluids, known as “imbibition,” in which a wetting fluid displaces a non-wetting fluid within the pore space of the membrane. This study presents a multi-scale modeling framework designed to investigate the imbibition process within LFAs. The framework integrates microscopic membrane characteristics into a macroscopic two-phase flow model, allowing the simulation of imbibition in membranes with different micro-scale properties and macro-scale profiles. The validity of the model was established through comparative analysis with documented case studies, a macro-scale single-phase flow model, and experimental observations, demonstrating its accuracy in simulating the imbibition process. The study also examines imbibition in various geometric configurations, including bifurcated (Y-shaped) and multi-branch geometries commonly found in multiplexed LFAs. The influence of geometric features such as length ratio, width ratio, branching angle, bifurcation point location, and asymmetry on fluid transport is investigated. Results indicate that membranes with larger branching angles exhibit slower imbibition. In addition, the influence of membrane type on macroscopic flow patterns is evaluated, showing that membranes with lower permeability require longer imbibition times. The insights gained from this research support a data-driven strategy for manipulating wetting behavior within LFAs. This approach can be leveraged to optimize the performance of LFAs and increase their effectiveness in various applications.

Decoupling Between Brain Activity and Cerebrospinal Fluid Movement in Neurological Disorders.

Recent research has identified a link between the global mean signal of resting-state functional MRI (fMRI) and macro-scale cerebrospinal fluid movement, indicating the potential link between this resting-state dynamic and brain waste clearance. Consistent with this notion, the strength of this coupling has been associated with multiple neurodegenerative disease pathologies, especially the build-up of toxic proteins. This article aimed to review the latest advancements in this research area, emphasizing studies on spontaneous global brain activity that is tightly linked to the global mean resting-state fMRI signal, and aimed to discuss potential mechanisms through which this activity and associated physiological modulations might affect brain waste clearance. The available evidence supports the presence of a highly organized global brain activity that is linked to arousal and memory systems. This global brain dynamic, along with its associated physiological modulations, has the potential to influence brain waste clearance through multiple pathways through multiple pathways. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 3.

A multiphasic model for determination of mouse ascending thoracic aorta mass transport properties with and without aneurysm.

Thoracic aortic aneurysms (TAAs) are associated with aortic wall remodeling that affects transmural transport or the movement of fluid and solute across the wall. In previous work, we used a Fbln4E57K/E57K (MU) mouse model to investigate transmural transport changes as a function of aneurysm severity. We compared wild-type (WT), MU with no aneurysm (MU-NA), MU with aneurysm (MU-A), and MU with an additional genetic mutation that led to increased aneurysm penetrance (MU-XA). We found that all aneurysmal aortas (MU-A and MU-XA) had lower fluid flux compared to WT. Non-aneurysmal aortas (MU-NA) had higher 4kDa FITC-dextran solute flux than WT, but aneurysmal MU-A and MU-XA aortas had solute fluxes similar to WT. Our experimental results could not isolate competing factors, such as changes in aortic geometry and solid material properties among these mouse models, to determine how intrinsic transport properties change with aneurysm severity. The objective of this study is to use biphasic and multiphasic models to identify changes in transport material properties. Our biphasic model indicates that hydraulic permeability is significantly decreased in the severe aneurysm model (MU-XA) compared to non-aneurysmal aortas (MU-NA). Our multiphasic model shows that effective solute diffusivity is increased in MU-NA aortas compared to all others. Our findings reveal changes in intrinsic transport properties that depend on aneurysm severity and are important for understanding the movement of fluids and solutes that may play a role in the diagnosis, progression, or treatment of TAA.

The development, characterisation and optimisation of bismuth ferrite (BFO)-incorporated Nafion membrane with comb-shaped inner structure as IPMC actuator for driving valveless micropump

Micropumps have become increasingly popular in biomedical devices due to their accurate, safe, and precise pharmaceutical administration. Ionic polymer-metal composites (IPMC) have shown great potential as diaphragm materials for micropump actuation. Redesigning the diaphragm shape can increase deformation by eliminating edge limitations in circular IPMC actuators. The present study demonstrates the application of inner cantilever-based (comb-shape) IPMC as actuation diaphragms in a micropump to enhance fluid movement. Furthermore, the effectiveness of an IPMC actuator is influenced by water absorption capacity, capacitance, and proton conductivity. To enhance the aforementioned characteristics, bismuth ferrite (BFO) was added to a Nafion matrix, resulting in a porous structure that increases capacitance. Moreover, the BFO-Nafion nanocomposite membrane exhibits a notably higher proton conductivity (0.1806 Scm−1) at a temperature of 30° C, in comparison to the normal Nafion 117 membrane (0.0254 Scm−1). The COMSOL Multiphysics and LASER Doppler Vibrometer are used to optimise the shape of the membrane and assess the IPMC’s electromechanical response. The deflection of the comb-shape geometries is around 171μm, surpassing existing membrane geometries. Finally, the drug delivery device prototype has a pump module, an Android-operated electronic control module, and an OLED display. This gadget achieves an insulin flow rate of 70 μL/min when operated at 3 V with a square wave frequency of 0.1 Hz. Moreover, the experimental findings indicate that applying an 8 V voltage resulted in a peak flow rate of 270 μL/min and a maximum back pressure of 140 Pascal.

Induced magnetic field and thermal regulation of synovial fluid flow through irregular surfaces with first-order slip and gold nanoparticles

ABSTRACT The current computational exploration develops a poroelastic model of the knee cartilage to elevate its temperature under cyclic sinusoidal loading. A contributing factor to the rise in temperature is this tissue’s viscous dissipation, which converts some of the mechanical energy supplied into heat. The manipulation of cartilage temperature is mostly reliant on the movement of synovial fluid inside the space between joints and within the permeable cartilage. We developed the region flow model in the presence of induced magnetic fields and gold nanoparticles, which enhanced the efficiency of joint lubrication by boosting the load-carrying capacity. We dealt with the problem for two different models. Model 1 assumes that viscosity is exponentially dependent on concentration. The shear thinning index in Model 2 is regarded as a concentration-dependent variable. We introduce these models for a complex wavy surface, where the first-order slip effect occurs. We modified the governing problem by assuming a long wavelength and a low Reynolds number. We followed up with a computational analysis utilizing the Rung–Kutta–Merson approach with Newton iteration in a shooting and matching strategy. We have conducted detailed comparisons between Model 1 and Model 2. The graphical findings have been shown for the distributions of velocity, temperature, and nanoparticle concentration. Additionally, the pressure gradients, streamlines, and axially generated magnetic fields have also been included. These results are presented for numerous physical parameters. The mechanics of trapping are thoroughly examined through the use of streamlines.

Development of a Custom Fluid Flow Chamber for Investigating the Effects of Shear Stress on Periodontal Ligament Cells.

The periodontal ligament (PDL) is crucial for maintaining the integrity and functionality of tooth-supporting structures. Mechanical forces applied to the tooth during orthodontic tooth movement generate pore pressure gradients, leading to interstitial fluid movement within the PDL. The generated fluid shear stress (FSS) stimulates the remodeling of PDL and alveolar bone. Herein, we present the construction of a parallel fluid-flow apparatus to determine the effect of FSS on PDL cells. The chamber was designed and optimized using computer-aided and computational fluid dynamics software. The chamber was formed by PDMS using a negative molding technique. hPDLCs from two donors were seeded on microscopic slides and exposed to FSS of 6 dyn/cm2 for 1 h. The effect of FSS on gene and protein expression was determined using RT-qPCR and Western blot. FSS upregulated genes responsible for mechanosensing (FOS), tissue formation (RUNX2, VEGFA), and inflammation (PTGS2/COX2, CXCL8/IL8, IL6) in both donors, with donor 2 showing higher gene upregulation. Protein expression of PTGS2/COX2 was higher in donor 2 but not in donor 1. RUNX2 protein was not expressed in either donor after FSS. In summary, FSS is crucial in regulating gene expression linked to PDL remodeling and inflammation, with donor variability potentially affecting outcomes.

A Photopolymerizable Hyaluronic Acid-Collagen Model of the Invasive Glioma Microenvironment with Interstitial Flow.

Glioblastoma recurrence is a major hindrance to treatment success and is driven by the invasion of glioma stem cells (GSCs) into healthy tissue that are inaccessible to surgical resection and are resistant to existing chemotherapies. Tissue-level fluid movement, or interstitial fluid flow (IFF), regulates GSC invasion in a manner dependent on the tumor microenvironment (TME), highlighting the need for model systems that incorporate both IFF and the TME. We present an accessible method for replicating the invasive TME in glioblastoma: a hyaluronan-collagen I hydrogel composed of human GSCs, astrocytes, and microglia seeded in a tissue culture insert. Elevated IFF can be represented by applying a fluid pressure head to the hydrogel. Additionally, this model can be tuned to replicate inter- or intra-patient differences in cellular ratios, flow rates, or matrix stiffnesses. Invasion can be quantified, while gels can be harvested for a variety of outcomes, including GSC invasion, flow cytometry, protein or RNA extraction, or imaging.

Intelligent neuron based interpretation of carreau trihybrid nanofluid model with streamline analysis: Configuration of distinct geometries

This current attempt develops a more efficient predictive model that can accurately simulate the behavior of Carreau trihybrid nanofluids in non-trivial configurations. This study interprets thermal behavior of Carreau trihybrid nanofluid model with streamline analysis considering the two geometries wedge and cone. Three nanoparticles are involved in base fluid (water) with physical effects of non-uniform heat sink source and nonlinear thermal radiation are assumed for heat transport and Lorentz forces are considered for velocity inspection. Furthermore, this study employs intelligent neural networks to interpret data for streamline and thermal transport analysis, focusing on the specific cases of wedge and cone geometries. Initial data fetched through bvp4c and further, obtained data trained through supervised neural scheme, Levenberg marquardt neural network (LM-NN) is applied and required predictions are made. Higher “Gc” indicates stronger solutal buoyancy forces, which promote upward fluid movement, thereby increasing the velocity gradient. With increasing (M), the velocity profile decreases. Fluid exhibits enhancing the velocity gradient with higher (n). Higher particle concentration enhances the fluid's viscosity and resistance.

Hypogene Alteration of Base–Metal Mineralization at the Václav Vein (Březové Hory Deposit, Příbram, Czech Republic): The Result of Recurrent Infiltration of Oxidized Fluids

The Václav vein (Březové Hory deposit, Příbram ore area, Czech Republic) is a base–metal vein containing minor Cu-Zn-Pb-Ag-Sb sulfidic mineralization in a usually hematitized gangue. A detailed mineralogical study using an electron microprobe revealed a complicated multistage evolution of the vein. Early siderite and Fe-rich dolomite were strongly replaced by assemblages of hematite+rhodochrosite and hematite+kutnohorite/Mn-rich dolomite, respectively. In addition, siderite also experienced strong silicification. These changes were associated with the dissolution of associated sulfides (sphalerite, galena). The following portion of the vein contains low-Mn dolomite and calcite gangue with Zn-rich chlorite, wittichenite, tetrahedrite-group minerals, chalcopyrite, bornite, and djurleite, again showing common replacement textures in case of sulfides. The latest stage was characterized by the input of Ag and Hg, giving rise to Ag-Cu sulfides, native silver (partly Hg-rich), balkanite, and (meta)cinnabar. We explain the formation of hematite-bearing oxidized assemblages at the expense of pre-existing “normal” Příbram mineralization due to repeated episodic infiltration of oxygenated surface waters during the vein evolution. Episodic mixing of ore fluids with surface waters was suggested from previous stable isotope and fluid inclusion studies in the Příbram ore area. Our mineralogical study thus strengthens this genetic scenario, illustrates the dynamics of fluid movement during the evolution of a distinct ore vein structure, and shows that the low content of ore minerals cannot be necessarily a primary feature of a vein.

Surface tension enables induced pluripotent stem cell culture in commercially available hardware during spaceflight

Low Earth Orbit (LEO) has emerged as a unique environment for evaluating altered stem cell properties in microgravity. LEO has become increasingly accessible for research and development due to progress in private spaceflight. Axiom Mission 2 (Ax-2) was launched as the second all-private astronaut mission to the International Space Station (ISS). Frozen human induced pluripotent stem cells (hiPSCs) expressing green fluorescent protein (GFP) under the SOX2 promoter, as well as fibroblasts differentiated from SOX2-GFP hiPSCs, were sent to the ISS. Astronauts then thawed and seeded both cell types into commercially available 96-well plates, which provided surface tension that reduced fluid movement out of individual wells and showed that hiPSCs or hiPSC-derived fibroblasts could survive either in suspension or attached to a Matrigel substrate. Furthermore, both cell types could be transfected with red fluorescent protein (RFP)-expressing plasmid. We demonstrate that hiPSCs and hiPSC-fibroblasts can be thawed in microgravity in off-the-shelf, commercially-available cell culture hardware, can associate into 3D spheroids or grow adherently in Matrigel, and can be transfected with DNA. This lays the groundwork for future biomanufacturing experiments in space.

Road section traffic risk propagation model based on macro traffic flow energy consumption

Traffic risk is an important source of road traffic accidents. Effectively predicting the propagation of accident risks on the road after an accident is of great significance for preventing secondary accidents. Therefore, this paper establishes a road section accident risk propagation model based on macro traffic flow energy consumption. Firstly, the influence of lane occupation and vehicle lane changing after the accident on traffic flow is analyzed, and a macro traffic flow model under the risk after the accident is constructed. Secondly, combined with the definition of traffic flow energy dissipation, the movement of the whole vehicle is abstracted as a fluid movement process, and a traffic flow energy consumption model under the risk after the accident is proposed to quantify the accident risk. Finally, according to the spatiotemporal correlation of risk propagation, a risk impact range and duration calculation model is proposed to describe the risk propagation process. In order to verify the effectiveness of the risk propagation model proposed in this paper, MATLAB and VISSIM are used to carry out numerical simulation and simulation verification of traffic flow operation under different initial traffic flow densities. The experimental results show that the greater the initial density of the road section when the accident occurs, the wider the risk impact range and the longer the duration. The absolute value of the prediction deviation rate of the proposed model is below 8%, which has a good prediction effect.

Crucial role of Aquaporin-4 extended isoform in brain water Homeostasis and Amyloid-β clearance: implications for Edema and neurodegenerative diseases

The water channel aquaporin-4 (AQP4) is crucial for water balance in the mammalian brain. AQP4 has two main canonical isoforms, M23, which forms supramolecular structures called Orthogonal Arrays of Particles (OAP) and M1, which does not, along with two extended isoforms (M23ex and M1ex). This study examines these isoforms’ roles, particularly AQP4ex, which influences water channel activity and localization at the blood-brain barrier. Using mice lacking both AQP4ex isoforms (AQP4ex-KO) and lacking both AQP4M23 isoforms (OAP-null) mice, we explored brain water dynamics under osmotic stress induced by an acute water intoxication (AWI) model. AQP4ex-KO mice had lower basal brain water content than WT and OAP-null mice. During AWI, brain water content increased rapidly in WT and AQP4ex-KO mice, but was delayed in OAP-null mice. AQP4ex-KO mice had the highest water content increase at 20 min. Immunoblot analysis showed stable total AQP4 in WT mice initially, with increases at 30 min. AQP4ex and its phosphorylated form (p-AQP4ex) levels rose quickly, but the p-AQP4ex/AQP4ex ratio dropped at 20 min. AQP4ex-KO mice showed a compensatory rise in canonical AQP4 at 20 min post-AWI. These findings highlight the important role of AQP4ex in water content dynamics in both normal and pathological states. To evaluate brain waste clearance, amyloid-β (Aβ) removal was assessed using a fluorescent Aβ intra-parenchyma injection model. AQP4ex-KO mice demonstrated markedly impaired Aβ clearance, with extended diffusion distances and reduced fluorescence in cervical lymph nodes, indicating inefficient drainage from the brain parenchyma. Mechanistically, the polarization of AQP4 at astrocytic endfeet is essential for efficient clearance flow, aiding interstitial fluid movement into the CSF and lymphatic system. In AQP4ex-KO mice, disrupted polarization forces reliance on slower, passive diffusion for solute clearance, significantly reducing Aβ removal efficiency and altering extracellular space dynamics. Our results underscore the importance of AQP4ex in both brain water homeostasis and solute clearance, particularly Aβ. These findings highlight AQP4ex as a potential therapeutic target for enhancing waste clearance mechanisms in the brain, which could have significant implications for treating brain edema and neurodegenerative diseases like Alzheimer’s.