Search

Directional wicking and spreading of liquids can be achieved by regular micro-patterns of specifically designed topographic features that break the reflection symmetry of the underlying pattern. The present study aims to understand the formation and stability of wetting films during the evaporation of volatile liquid drops on surfaces with a micro-pattern of triangular posts arranged in a rectangular lattice. Depending on the density and aspect ratio of the posts, we observe either spherical-cap shaped drops with a mobile three-phase contact line or the formation of circular or angular drops with a pinned three-phase contact line. Drops of the latter class eventually evolve into a liquid film extending to the initial footprint of the drop and a shrinking cap-shaped drop sitting on the film. The drop evolution is controlled by the density and aspect ratio of the posts, while no influence of the orientation of the triangular posts on the contact line mobility becomes evident. Our experiments corroborate previous results of systematic numerical energy minimization, predicting that conditions for a spontaneous retraction of a wicking liquid film depend weakly on the orientation of the film edge relative to the micro-pattern. [ABSTRACT FROM AUTHOR]

[Display omitted] Understanding moisture sorption in porous insulation materials is challenging due to the influence of multiscale pore structures on phase behavior and transport properties. Dynamic moisture sorption in dual-porous materials is likely co-determined by interior micro- and nano-scale pores, and an accurate physical model for predicting moisture evolution can be developed by clarifying the sorption mechanisms. Moisture behavior during the dynamic sorption of dual-porous insulation material is measured by low-field nuclear magnetic resonance (NMR) experiments. The contributions of micro- and nano-scale pores to the adsorbed moisture are differentiated using NMR relaxometry, and the evolution of moisture morphology is quantitatively analyzed. Analysis of T 2 evolution reveals that the moisture in nano-scale pores alters from adsorption layers to liquid with increasing relative humidity (RH), while minimal sorption occurs in micro-scale pores. Moisture is mainly transferred as vapor molecules at low RH levels, with the dynamic sorption enhanced by molecular diffusion in micro-scale pores. Capillary flow in nano-scale pores dominates moisture transport when RH rises above a threshold, leading to a significant increase in apparent moisture diffusivity. According to the elucidated mechanism, a physical model is further developed to predict moisture sorption inside dual-porous insulation materials, and it may serve as a basis for evaluating and optimizing the performance of dual-porous systems in different environments. [ABSTRACT FROM AUTHOR]

In severe cases, SARS-CoV-2 infection leads to severe respiratory failure. Although angiotensin-converting enzyme 2 (ACE2) receptors are not expressed in red blood cells, SARS-CoV-2 can interact with red blood cells (RBCs) via several receptors or auxiliary membrane proteins. Recent data show that viral infection causes significant damage to the RBCs, altering their morphology, deformability, and aggregability. Loss of RBC deformability and/or increased aggregability favors the development of thrombotic processes in the microcirculation, as has been described to occur in COVID-19 patients. In addition, many patients also develop systemic endotheliitis associated with generalized coagulopathy. This manifests itself clinically as obstructive microthrombi in the area of the medium and smallest vessels, which can affect all internal organs. It is thought that such changes in the RBCs may contribute to the microangiopathy/microthrombosis associated with COVID-19 and may result in impaired capillary blood flow and tissue oxygenation. [ABSTRACT FROM AUTHOR]

Aim: Rosacea is a chronic inflammatory skin disease characterized by consistent erythema, papules, pustules, telangiectasias, and recurrent hot flashes, mainly on the cheeks, nose, and forehead. Many palliative treatment options are available for this condition; currently, no radical treatment option is available. However, improvement has been observed in some cases after the use of Kampo medicine. In this study, we aimed to analyze the effects of Jumi‐Haidokuto (JHT) and a mixture of Keishi‐Bukuryo‐gan‐ka‐Yokuinin (KBY) and JHT on steroid‐induced rosacea in mice. Methods: Clobetasol propionate ointment was applied to the mice for 10 days and then the mice were provided food mixed with JHT and JHT + KBY for 28 days. Subsequently, the average velocity of capillary flow, area of the purpura, histopathologic features, and fecal metabolome were investigated. Results: Recovery of the capillary flow velocity, reduction in the area of purpura, and restoration of the epidermal features were observed in JHT‐ and JHT + KBY‐fed mice. The improvement in circulatory disturbances observed after JHT and JHT + KBY administration might have contributed to the reduction in telangiectasias and erythema. Recovery of the skin barrier system by both Kampo medicine might be the key factor of ameliorating rosacea‐like symptoms. [ABSTRACT FROM AUTHOR]

This paper establishes a fully analytical equation for the relative hydraulic conductivity of soils through a probabilistic porous network model. Under this approach, a parameter, accounting for the proportion of pores of a certain maximum size forming continuous paths of saturated elements between the boundaries, is obtained and used to compute the hydraulic conductivity of soils. This method avoids the necessity of the pore-scale model approach required by computational networks to obtain the hydraulic conductivity of soils at different water contents. Additionally, constraints related to computing time, memory size, and the effect of the size of the network on the results are avoided. Furthermore, the network can consider single-, double-, or triple-structured soil. The theoretical and experimental comparisons indicate that the capillary flow regime can account for the hydraulic conductivity of sandy soils for suctions below 0.1 MPa without the need for a different flow regime as the film flow. Finally, all parameters required in the relative conductivity equation can be obtained directly from the pore-size distribution or by fitting the numerical with the experimental soil water retention curves of the material. The determination of the hydraulic conductivity function of soils is required for a number of geotechnical problems: the flow of contaminants, the flow of water in slopes and cuts to define the variations in the factor of safety against the infiltration of water, the flow of water in expansive soils for the design of optimal foundations, and the behavior of buffers of bentonite pellets around the radioactive repositories of nuclear waste during wetting–drying cycles. With the present development, it is possible to define the relative permeability function from the retention curves of soils and the use of a probabilistic porous model. When the retention curves are fitted, the proportion of continuous paths of saturated pores of certain maximum size connecting the flow boundaries can be extracted. This procedure results in a fully analytical solution and a more expeditious method for the determination of the hydraulic conductivity of soils subjected to different suctions. [ABSTRACT FROM AUTHOR]

Consciousness is lost within seconds upon cessation of cerebral blood flow. The brain cannot store oxygen, and interruption of oxidative phosphorylation is fatal within minutes. Yet only rudimentary knowledge exists regarding cortical partial oxygen tension (PO2) dynamics under physiological conditions. Here we introduce Green enhanced Nano-lantern (GeNL), a genetically encoded bioluminescent oxygen indicator for PO2 imaging. In awake behaving mice, we uncover the existence of spontaneous, spatially defined “hypoxic pockets” and demonstrate their linkage to the abrogation of local capillary flow. Exercise reduced the burden of hypoxic pockets by 52% compared with rest. The study provides insight into cortical oxygen dynamics in awake behaving animals and concurrently establishes a tool to delineate the importance of oxygen tension in physiological processes and neurological diseases. [ABSTRACT FROM AUTHOR]

Glucose is an important biomarker for diagnosing and prognosing various diseases, including diabetes and hypoglycemia, which can have severe side effects, symptoms, and even lead to death in patients. As a result, there is a need for quick and economical glucose level measurements to help identify those at potential risk. With the increase in smartphone users, portable smartphone glucose sensors are becoming popular. In this paper, we present a disposable microfluidic glucose sensor that accurately and rapidly quantifies glucose levels in human urine using a combination of colorimetric analysis and computer vision. This glucose sensor implements a disposable microfluidic device based on medical-grade tapes and glucose analysis strips on a glass slide integrated with a custom-made polydimethylsiloxane (PDMS) micropump that accelerates capillary flow, making it economical, convenient, rapid, and equipment-free. After absorbing the target solution, the disposable device is slid into the 3D-printed main chassis and illuminated exclusively with Light Emitting Diode (LED) illumination, which is pivotal to color-sensitive experiments. After collecting images, the images are imported into the algorithm to measure the glucose levels using computer vision and average RGB values measurements. This article illustrates the impressive accuracy and consistency of the glucose sensor in quantifying glucose in sucrose water. This is evidenced by the close agreement between the computer vision method used by the sensor and the traditional method of measuring in the biology field, as well as the small variation observed between different sensor performances. The exponential regression curve used in the study further confirms the strong relationship between glucose concentrations and average RGB values, with an R-square value of 0.997 indicating a high degree of correlation between these variables. The article also emphasizes the potential transferability of the solution described to other types of assays and smartphone-based sensors. [ABSTRACT FROM AUTHOR]

Flow structure near three phase contact line (TPCL) of evaporating liquids plays a significant role in liquid wetting and dewetting, liquid film evaporation, and boiling. Despite the wide focus it receives, the interacting mechanisms therein remain elusive and in specific cases, controversial. Here, we reveal the profile of internal flow and elucidate the dominating mechanisms near TPCL of evaporating droplets, using mathematical modeling, trajectory analysis, and infrared thermography. We indicate that for less volatile liquids such as butanol, the flow pattern is dominated by capillary flow. With increasing liquid volatility, e.g., alcohol, the effect of evaporation cooling, under conditions, induces interfacial temperature gradient with cold droplet apex and warm edge. The temperature gradient leads to Marangoni flow that competes with outwarding capillary flow, resulting in the reversal of interfacial flow and the formation of a stagnation point near TPCL. The spatiotemporal variations of capillary velocity and Marangoni velocity are further quantified by mathematically decomposing the tangential velocity of interfacial flow. The conclusions can serve as a theoretical base for explaining deposition patterns from colloidal suspensions and can be utilized as a benchmark in analyzing more complex liquid systems. [ABSTRACT FROM AUTHOR]

This research delves into the unexplored territory of using CT image processing techniques to assess capillary flow in freshly felled Scotch pine logs during the drying process. Leveraging a high-resolution CT scanner, the study captures intricate details of the wood's internal structure, which were then quantified using image processing algorithms. The findings confirm the efficacy of CT image processing in accurately determining capillary flow in wood. This opens up new opportunities for non-destructive testing methods and contributes to a deeper understanding of wood properties. The implications of these findings are farreaching, offering substantial advancements in quality control and processing optimization in the wood industry. [ABSTRACT FROM AUTHOR]

Flexoelectric actuation employs an applied electric field to induce membrane curvature, which is the mechanism utilized by the outer hair cells (OHC) present in the inner ear. The model developed for this study, representing the OHC, integrates two key components: (i) an approximation of the flexoelectric membrane shape equation for circular membranes attached to the inner surface of a circular capillary, and (ii) the coupled capillary flow of contacting liquid viscoelastic phases characterized by the Tanner-Power law rheological equation of state. A second-order non-linear differential equation for average curvature has been derived, and a robust numerical method has been programmed. This model simplifies to a linear model used previously. The main challenge involves identifying and describing the enhancement in curvature change rate. It was observed that low symmetry, low viscosity, and soft membrane and shear-thickening behavior of the phases enhance the curvature change rate. Additionally, there exists a critical electric field frequency value that maximizes the curvature change rate (resonance effect). The current theory, model, and computational simulations add to the ongoing development comprehension of how biological membrane shape actuation through electromechanical couplings. [ABSTRACT FROM AUTHOR]

The present work investigates the size based self-sorting behavior of particles near the contact line (CL) region of an evaporating sessile aqueous droplet containing bidispersed (1 and 3 μm) colloidal particles. Experiments were performed on hydrophilic glass and hydrophobic (Poly)dimethylsiloxane (PDMS) substrates maintained at different temperatures (Ts = 23°C, 50°C, and 80°C). The role of substrate wettability and substrate temperature in the modulation of final deposition specifically, the self-sorting characteristics was examined. Various experimental techniques namely, high-speed visualization, 3D optical profilometry, fluorescence microscopy, and scanning electron microscopy were implemented to analyze the droplet evaporation and the morphology of the final deposition. As per the findings, in the case of hydrophilic substrate self-sorting existed at all temperatures. However, an appreciable improvement in the sorting quality was observed only at elevated temperatures. Particularly, for the case of Ts = 80°C in which the final deposition demonstrated better sorting of 1 and 3 μm particles. Since, most of the region in the CL's vicinity had a substantial reduction in the intermixing of 1 and 3 μm particles, thus effectively favouring the suppression of mixed region. In the case of nonheated (Ts = 23°C) hydrophobic substrate it was observed that a continuous depinning of the CL, in conjunction, with a weak radial flow led to complete intermixing of the bidispersed particles thus, lacking any self-sorting behavior. However, for the heated hydrophobic substrate cases, a substantial delay in the depinning of the CL existed. This, in turn, combined with the outward-driven capillary flow and recirculatory thermal-Marangoni flow resulted in the manifestation of self-sorting phenomenon. This study is expected to offer novel fundamental insights into the underlying mechanisms that can be effectively leveraged, to gain better control of the governing parameters for the realization of desired sorting characteristics. [ABSTRACT FROM AUTHOR]

The linear correspondence between flow rate and pressure drop for low Reynolds number hydrodynamics is often a constraint for the realization of miniaturized fluid circuits with selective junctions. Here we devise a micro-nanochannel junction with the directional flow in the nanochannel achieved by a combination of junction geometry and wall functionalization. The system can be compared to a fluid diode with parity-breaking between pressure drop and flow rate in the nanochannel junction with increasing flow rates in a particular configuration and negligible throughput in the reverse direction. This directional junction transport is tuned with slip length, characterizing channel wall functionalization as the bias parameter. Tuning the transport or leakage at a junction is key to engineering various applications. Such junctions are ubiquitous in systems like capillary blood flow, desalination systems, energy storage devices, etc. The resulting flow physics, thus unraveled, is an amalgamation of various factors which leads to a flow rectification system. We have delineated the effect of the confinement of the channel, the slip, and the geometry of the nanochannel towards the selective nature of the resulting configuration. We have successfully characterized a system to generate flow anisotropy while transporting fluid in different directions using numerical techniques. Additionally, our work demonstrates, for the first time, that a common definition of slip coefficient may be associated with three different flow regimes, which correspond to the order of magnitude of slip length relative to the channel dimensions thus providing a unifying key to engineer substrates and geometries towards designing fluid circuits. [ABSTRACT FROM AUTHOR]

Capillary invasion of liquid is a spontaneous phenomenon that occurs at length scales smaller than the capillary length. By means of capillary action, numerous applications have been developed. We investigate the time-dependent displacement of a Newtonian oil using viscoelastic polyethylene oxide solutions. The setup implies a capillary tube in a horizontal configuration that was partially prefilled with oil. We emphasize the prefilling liquid’s role in the dynamics of the system and show the influence of the displacing liquid’s viscoelastic properties. We find significant changes in the capillary regime as the displacing liquid’s viscoelastic properties change.

Coupling red blood cell (RBC) supply to O2 demand is an intricate process requiring O2 sensing, generation of a stimulus, and signal transduction that alters upstream arteriolar tone. Although actively debated, this process has been theorized to be induced by hypoxia and to involve activation of endothelial inwardly rectifying K+ channels (KIR) 2.1 by elevated extracellular K+ to trigger conducted hyperpolarization via connexin40 (Cx40) gap junctions to upstream resistors. This concept was tested in resting healthy skeletal muscle of Cx40-/- and endothelial KIR2.1-/- mice using state-of-the-art live animal imaging where the local tissue O2 environment was manipulated using a custom gas chamber. Second-by-second capillary RBC flow responses were recorded as O2 was altered. A stepwise drop in PO2 at the muscle surface increased RBC supply in capillaries of control animals while elevated O2 elicited the opposite response; capillaries were confirmed to express Cx40. The RBC flow responses were rapid and tightly coupled to O2; computer simulations did not support hypoxia as a driving factor. In contrast, RBC flow responses were significantly diminished in Cx40-/- mice. Endothelial KIR2.1-/- mice, on the other hand, reacted normally to O2 changes, even when the O2 challenge was targeted to a smaller area of tissue with fewer capillaries. Conclusively, microvascular O2 responses depend on coordinated electrical signaling via Cx40 gap junctions, and endothelial KIR2.1 channels do not initiate the event. These findings reconceptualize the paradigm of blood flow regulation in skeletal muscle and how O2 triggers this process in capillaries independent of extracellular K+. [ABSTRACT FROM AUTHOR]

The proposed flow problem is to analyze the behavior of dissipative heat on the time-dependent stagnation motion of nanofluids through a permeable surface. A novel approach to thermal buoyancy through the permeable medium enriches the flow properties. In the recent industrial applications for the cooling processes of the device, like the physiological application of the blood flow inside the capillary tube-like artery, drug delivery system, etc., the role of nanofluid is crucial. The proposed model equipped with various physical properties is used to design and subsequent transformation into a non-dimensional form is obtained for a set of similarity variables. Proposed models with different physical properties are designed and subsequent dimensionless transformations are obtained for a similar set of variables. In addition, shooting based Runge-Kutta fourth-order numerical technique is used to solve boundary value problems for nonlinear ordinary systems. The characteristics of the diversified quantities are presented graphically as well as numerically on the flow profile and other profiles. Furthermore, statistical approaches such as t-tests for simulated results of rate coefficients are also presented and validated with the obtained results. However, the important outcomes are presented as; the fluid velocity is controlled by the inclusion of the particle concentration as well as the magnetic parameter further the particle concentration and the dissipative heat encountered by the inclusion of Eckert number enhances the fluid temperature. [ABSTRACT FROM AUTHOR]

The drying shrinkage of porous materials is significantly dependent on external relative humidity (RHe$RH^{e}$). The perspective of temperature increase due to the climate change will accentuate the drying phenomenon in structures in lands and cities. The evolution of shrinkage can be determined by equivalent pore pressure consisting of capillary pressure Pc$P_c$, disjoining pressure and pressure caused by interfacial energy. For concrete structures, up to RHe=70%$RH^{e}=70 \%$ condition, standard models can reproduce the drying shrinkage experiments accurately. However, as the RHe$RH^{e}$ decreases to 30%, these models seem to be limited because the measured relationship (Pc−Sw${{P}_{c}}-{{S}_{w}}$) differs from the corresponding static equilibrium relationship as the drying occurs rapidly and the dynamic fluid flow effects on capillary pressure have been neglected. In this paper, the standard shrinkage model has been improved to take into account the dynamic flow effect and the viscoelastic behaviour of the solid skeleton. The dynamic and standard models have been compared with experimental results of drying shrinkage of concrete with two different relative humidity conditions. The standard model clearly showed its limitations at low external relative humidity RHe=30%$RH^{e}=30 \%$. However, the dynamic model showed good prediction of mass loss and shrinkage strains at high and low humidity conditions. Furthermore, the numerical and experimental investigations indicate that not only the dynamic effects but also the additional pressure induced by surface energy should be taken into account to quantify the drying shrinkage of cement‐based materials at low RHe$RH^{e}$ condition. [ABSTRACT FROM AUTHOR]

The response of the water–oil droplet flow to a perturbation of flow resistance added at the arms of a bypassed micro-T-junction is studied through a numerical method. The capillary number of the continuous flow varies between 0.007 and 0.034. Once an additional flow resistance is introduced at the arms of the T-junction, the flow self-adapts to the perturbation and droplets show complex dynamics at the junction, including splitting, merging, and reshaping. During the self-adaptive process, the instantaneous splitting ratios of the dispersed flow show positive correlations with that of the continuous flow. The correlation coefficient reduces as the increase in the amplitude of the perturbation. The ensemble splitting ratios of them, however, are independent. It shows a rather simple law that the ensemble splitting ratios of oil anchor at around a constant value while the corresponding parameter of water varies from 0 to 1. It illustrates that the droplet flow splitting at a T-junction resembles a resilient system, the stiffness of which depends on the capillary number of the flow. The energy loss of the system induced by a perturbation of the flow resistance is self-reduced by just redistributing of droplets into the two arms. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of n-butane (R600) and isobutane (R600a) flows in adiabatic capillary tubes. In total, 48 experimental data points were gathered spanning the typical conditions of household refrigerators, with capillary inner diameters ranging from 0.53 to 0.79 mm, tube lengths ranging from 2.5 to 3.5 m, inlet pressure ranging from 2.83 to 6.05 bar, exit pressure ranging from 0.3 to 0.9 bar, inlet subcooling ranging from 4.7 to 15.2 °C, and mass flow rates ranging from 0.53 to 2.95 kg h−1. In addition, the accuracy of π-type correlations priorly developed for R600a flows was verified when used with R600 to predict the refrigerant mass flow rate. Also, it was found the mass flow rate predictions of the algebraic model developed by Hermes et al. (2010) for R600a agreed well with the R600 experimental data, with more than 90 % of data points within ± 10 % error bands. [ABSTRACT FROM AUTHOR]

Background: Angiogenesis is essential for tissue repair in ischemic diseases, relying on glycolysis as its primary energy source. Prolyl 4-hydroxylase subunit alpha 1 (P4HA1), the catalytic subunit of collagen prolyl 4-hydroxylase, is a glycolysis-related gene in cancers. However, its role in glycolysis-induced angiogenesis remains unclear. Methods: P4HA1 expression was modulated using adenoviruses. Endothelial angiogenesis was evaluated through 5-ethynyl-2′-deoxyuridine incorporation, transwell migration, and tube formation assays in vitro. In vivo experiments measured blood flow and capillary density in the hindlimb ischemia (HLI) model. Glycolytic stress assays, glucose uptake, lactate production, and quantitative reverse transcription-polymerase chain reaction (RT-PCR) were employed to assess glycolytic capacity. Transcriptome sequencing, validated by western blotting and RT-PCR, was utilized to determine underlying mechanisms. Results: P4HA1 was upregulated in endothelial cells under hypoxia and in the HLI model. P4HA1 overexpression promoted angiogenesis in vitro and in vivo, while its knockdown had the opposite effect. P4HA1 overexpression reduced cellular α-ketoglutarate (α-KG) levels by consuming α-KG during collagen hydroxylation. Downregulation of α-KG reduced the protein level of a DNA dioxygenase, ten–eleven translocation 2 (TET2), and its recruitment to the fructose-1,6-biphosphatase (FBP1) promoter, resulting in decreased FBP1 expression. The decrease in FBP1 enhanced glycolytic metabolism, thereby promoting endothelial angiogenesis. Conclusions: Hypoxia-induced endothelial P4HA1 overexpression enhanced angiogenesis by promoting glycolytic metabolism reprogramming through the P4HA1/α-KG/TET2/FBP1 pathway. The study's findings underscore the significance of P4HA1 in post-ischemic angiogenesis, suggesting its therapeutic potential for post-ischemic tissue repair. [ABSTRACT FROM AUTHOR]

Predicting the compactness of the invasion front and the amount of trapped fluid left behind is of crucial importance to applications ranging from microfluidics and fuel cells to subsurface storage of carbon and hydrogen. We examine the interplay of wettability, macro‐ and pore scale heterogeneity (pore angularity and pore wall roughness), and its influence on flow patterns formation and trapping efficiency in porous media by a combination of 3D micro‐CT imaging with 2D direct visualization of micromodels. We observe various phase transitions between the following capillary flow regimes (phases): (a) compact advance, (b) wetting and drainage Invasion percolation, (c) Ordinary percolation. Plain Language Summary: The study of phase transitions in flow patterns that depend on the heterogeneity, wettability, and surface roughness of the pore space and their classification in phase diagrams is one of the challenges in recent multiphase flow physics. We study the dynamics of thick film and corner flows by visualization experiments with micromodels. Both flow types are characteristic of geologically representative porous media (sands, sandstones) and control the displacement and trapping process. The 2D micromodels accurately reproduce the characteristic geometric, morphological, and topological properties of 3D porous media. All microstructures were derived from μ‐CT images. We fabricated identical microstructures by both DRIE‐ICP etching of silicon wafers and anisotropic chemical etching of glass ceramics to vary the degree of surface roughness. The results are in excellent agreement with previous μ‐CT experiments. We observe various phase transitions between the following flow regimes (phases): (a) frontal/compact advance, (b) Ordinary percolation, and (c) Invasion percolation. We show that they can be classified according to Blunt's "heterogeneity versus wettability" phase diagram. Key Points: Interplay of pore‐scale heterogeneity, wettability, and surface roughness controls displacement patterns and capillary trapping efficiencyThe invasion flow pattern for capillary flow were visualized by micro‐CT‐ and micromodel experiments and classified in a new phase diagramFour generic flow regimes (phases) were observed: frontal advance, wetting and drainage invasion percolation, and ordinary percolation [ABSTRACT FROM AUTHOR]

The article analyzes the factors involved in making polyoxadiazole fiber-forming systems through spinneret capillaries under dry-wet method conditions. The drawbacks of the wet polyoxadiazole fiber forming method were identified. A method of two-stage extrusion of solutions of polyoxadiazole fiber-forming systems, the first of which is carried out through spinneret holes into a gaseous medium and the second, in a precipitating dilute sulfuric acid bath, is proposed. A mathematical interpretation of the technological factors of polymer solution flow through spinneret capillaries, including the rate of solution flow through capillaries with different diameters and spinneret drafting, is offered. [ABSTRACT FROM AUTHOR]

This review spans a wide arc from the first observations of the early anatomists to the present day. William Harvey was the first to describe the heart as the centre of the large and small circulatory system. He thus replaced the previously valid system of Galenos, It was Marcello Malpighi who first described that the capillary system connects the arteries with the veins. In 1688 Antoni van Leeuwenhoek (1632–1686) confirmed these results with a paper on capillary perfusion in the caudal fin of the glass eel. It was then Hermann Boerhave (1668–1738, Leiden) who was the first to carry out microcirculation tests on patients. He studied the microcirculation in the human bulbar conjunctiva. Even today, microcirculation studies in the conjunctiva bulbi of patients are carried out today. Until 1831, it was never quite clear whether the observations reported belonged mainly to the field of microcirculation, which had not yet been defined. This was done in Great Britain by Marshall Hall (1790–1857). Technical Improvements allowed increasingly sophisticated studies of the morphological structure of the terminal vasculature. According to Gustav Ricker (1870–1948, Vienna), the terminal vasculature comprises the functional unit of the smallest arteries, arterioles, capillaries and venules. In 1921 it was still thought that the blood circulation was the sole response to the pumping action of the heart. Even the classic work by Bayliss on the myogenic hypothesis (later referred to as "blood flow autoregulation") initially received little attention. More strikingly, even the findings of August Krogh, for which he received the Nobel Prize in Medicine in 1920 (for his discovery of the mechanisms of capillary motor regulation), were ignored. During an outstanding autoregulation symposium held in 1963 a broad consensus was reached on active and passive mechanisms, which is more or less valid till today. The mechanisms of regulation of capillary blood flow are now largely understood, although not completely resolved. The development of video systems with recording capability and automated off-line recording of capillary erythrocyte velocities allowed the application of morphological and dynamic studies of cutaneous capillaries in humans. These reopened the field of physiological or pathophysiological questions again for many groups worldwide. Since 1955, many publications on "microcirculation (5423)" and "capillary microscopy (2195)" have been listed in pubmed. [ABSTRACT FROM AUTHOR]

During the processing of elastomeric compounds under high flow rates, significant pressure drops (106–108 Pa) are encountered. Under such conditions, the viscosity of these compounds is significantly affected by pressure and viscous heating. Moreover, strong flow rates may cause these systems to slip at the wall, violating the classical no-slip boundary condition of fluid mechanics. To determine the slip velocity by the well-known Mooney method, the effects of pressure and viscous heating should be considered. In this work, an experimental methodology is developed to determine the slip velocity of styrene–butadiene compounds in capillary flow corrected for the effects of pressure and viscous heating. First, the temperature increase due to viscous heating is measured during the extrusion process and accounted for in correcting the experimental data to infer the slip velocity. Consequently, the corrected experimental data for the effects of pressure and viscous heating are used to calculate the slip velocity from the deviation of the linear viscoelastic behavior (deviation from the Cox–Merz rule). The Mooney method is also used to confirm the calculated slip velocity of the elastomeric compounds. [ABSTRACT FROM AUTHOR]

We investigate the capillary displacement of silicone oil columns by water in tandem with a Taylor gas bubble in horizontally aligned tubes that initially separate the two immiscible liquids. The experiments show that the gas slug's motion forces the drainage of the prefilling liquid through a thin film deposited on the tube's wall. The displaced oil is then recovered at the advancing water meniscus. The dynamics of the capillary displacement and drainage are studied as functions of the silicone oil and gas bubble volumes. We find that the Taylor bubble's length has a small influence on the capillary displacement and drainage of the prefilling liquid. The study presents an adapted model for the capillary drainage and oil recovery using Taylor's law for the deposited film thickness on the tube's wall, which collapses all experimental data onto a single curve. [ABSTRACT FROM AUTHOR]

Although immiscible fluid–fluid displacement in porous media has received extensive attention, understanding the dynamics behavior within complex structures remains elusive. This study utilizes the direct numerical simulation by solving the Navier–Stokes equations and coupling with the volume of fluid method to examine oil–water flow in porous media across various contact angles θ and capillary number Ca. Three kinds of artificial porous media were generated with designed opening angle β, including single-structure and dual-structure models. A theoretical analysis of the capillary barrier phenomenon, as well as its occurrence conditions, is identified under water-wet conditions. Generally, when θ + β < 90°, the capillary force consistently drives oil displacement from throats to pores. Conversely, if θ + β > 90°, the direction of the capillary force can move toward the water phase side and prevent the fluid interface from continuing to move. For a single-structure porous medium, the dynamics behavior of fluids is controlled by the capillarity, wettability, and geometric structures. The greatest efficiency occurs when the condition θ + β = 90° is met, particularly at an intermediate Ca. For a dual-structure porous medium with smaller opening angles inside, the water phase tends to infiltrate the embedded pore structure due to weaker capillary barrier effects. Conversely, larger opening angles within the embedded structure lead to stronger capillary barrier effects, hindering water entry into the interior porous medium. This obstruction forces the water phase to bypass and traverse longer flow paths, resulting in the formation of a large amount of residual oil. [ABSTRACT FROM AUTHOR]

Background: Glomus apparatus maintains flow in capillaries in response to changes in temperature. Glomus tumors are rare perivascular hamartomas arising from glomus bodies at fingertips. They are associated with classic triad of symptoms including paroxysmal pain, cold hypersensitivity, and pinpoint tenderness. Due to its rarity and peculiar presentation, they are often misdiagnosed and inappropriately treated. Surgical excision is the treatment of choice either by transungual or lateral periosteal approach. Materials and Methods: We conducted a retrospective analysis of the cases of glomus tumors that were operated in the past 5 years in our institute. Patient demographic details, clinical features, imaging parameters, operative details, photographs and complications if any during follow up were analysed. QuickDASH was the primary statistical parameter, and change in QuickDASH score was analyzed with paired t‑test. Results: The average age at diagnosis was 29.77 years. The male‑to‑female ratio was 1:5. The mean duration of symptoms is 10.08 months. The mean preoperative QuickDASH score was 25.27 (range: 11.25–34). The mean follow‑up was 26.7 months (range: 6–48 months). At 6‑month follow‑up, the mean score was 1.52 (range: 0–13.64). The difference in mean scores was 23.7708 with significant P < 0.001. Conclusion: Glomus tumors are rare but debilitating lesions. They are often misdiagnosed and intervened inappropriately before arriving at an actual diagnosis. With complete excision by magnification‑assisted surgery, quality of life generally improves, and recurrence is prevented. [ABSTRACT FROM AUTHOR]

BACKGROUND: At present, digital subtraction angiography is used in the clinical observation of blood supply of femoral head necrosis, and the patency of the nutrient blood vessels of the femoral head is evaluated by observing the in and out of the contrast agent. Although digital subtraction angiography can visually observe the feeding vessels of the femoral head, it cannot quantify the perfusion. In addition, the collapse of the femoral head is closely related to the prognosis of the disease, but there are few studies on the changes in blood supply in the femoral head during the peri-collapse period. OBJECTIVE: To compare the differences in microcirculation perfusion in different regions and different stages of femoral head necrosis, summarize the changes in microcirculation perfusion characteristics of femoral head necrosis, and observe the effect of dynamic contrast-enhanced magnetic resonance imaging in evaluating the microcirculation perfusion of the femoral head. METHODS: From February 16 to September 1, 2022, a total of 37 patients (69 hips) who visited a doctor for femoral head necrosis were retrospectively collected, including 29 males and 8 females; the age was (35.35±12.19) years (range 18-65 years). The patient’s bilateral femoral head and proximal femur were scanned by dynamic contrast-enhanced magnetic resonance imaging, and gadoteric acid meglumine was intravenously injected during the scanning. After scanning, Geniq software was used to post-process the data to obtain femoral head microcirculation perfusion parameters. Regions of interest were drawn at the necrotic zone, repair reaction zone, and greater trochanter, and time-signal intensity curves of the regions of interest were obtained and classified. Paired t-tests were used to evaluate differences between necrotic area, repair reaction area, and greater trochanter perfusion parameters, as well as differences in femoral head perfusion in different stages of necrosis. Differences in necrotic area, repair reaction area and greater trochanter time-intensity curve classification were evaluated using the χ2 test. RESULTS AND CONCLUSION: (1) Comparing the perfusion parameters in different regions, the peak value of enhanced signal intensity, area under the curve, maximum slope, volume transfer constant, and the median volume fraction of extravascular extracellular space in the necrotic region were lower than those of the greater trochanter, and the differences were statistically significant (P < 0.05). There was no statistically significant difference in the volume rate constant (P > 0.05). (2) The signal peak value, area under the curve, maximum slope, volume transfer constant, rate transfer constant, and the median ratio of extravascular to extracellular space in the repair reaction area were higher than those in the necrotic area and the greater trochanter, and the differences were statistically significant (P < 0.05). (3) The median signal peak value and maximum slope of the necrotic area in ARCO stage II were greater than those in ARCO stage III, and the difference was statistically significant (P < 0.05). There were no significant differences in area under the curve, rate transfer constant, volume transfer constant and the median ratio of extravascular to extracellular space (P > 0.05). (4) The signal peak value, area under the curve, maximum slope, volume transfer constant, rate transfer constant, and ratio of extravascular to extracellular space in the repair reaction zone of the ARCO Stage II were lower than those of the ARCO Stage III, and the difference was statistically significant (P < 0.05). (5) It is concluded that the microcirculation perfusion velocity, blood flow and capillary permeability in the necrotic area of the femoral head were significantly reduced, while the microcirculation perfusion velocity, blood flow and vascular permeability in the repair reaction area were significantly improved compared with those in the normal area. With the occurrence of collapse, the perfusion velocity and blood flow were further reduced, and the perfusion in the repair reaction zone was enhanced. [ABSTRACT FROM AUTHOR]

The fused deposition modeling (FDM) process, an extrusion-based 3D printing technology, enables the manufacture of complex geometrical elements. This technology employs diverse materials, including thermoplastic polymers and composites as well as recycled resins to encourage sustainable growth. FDM is used in a variety of industrial fields, including automotive, biomedical, and textiles, as a rapid prototyping method to reduce costs and shorten production time, or to develop items with detailed designs and high precision. The main phases of this technology include the feeding of solid filament into a molten chamber, capillary flow of a non-Newtonian fluid through a nozzle, layer deposition on the support base, and layer-to-layer adhesion. The viscoelastic properties of processed materials are essential in each of the FDM steps: (i) predicting the printability of the melted material during FDM extrusion and ensuring a continuous flow across the nozzle; (ii) controlling the deposition process of the molten filament on the print bed and avoiding fast material leakage and loss of precision in the molded part; and (iii) ensuring layer adhesion in the subsequent consolidation phase. Regarding this framework, this work aimed to collect knowledge on FDM extrusion and on different types of rheological properties in order to forecast the performance of thermoplastics. [ABSTRACT FROM AUTHOR]

A transpiration-type thermoelectric-power-generating paper based on previously developed carbon nanotube (CNT) composite paper, which is a composite material of CNTs and pulp that can generate thermoelectric power, was developed. The newly developed thermoelectric-power-generating material does not require an external high-temperature heat source due to the ability of paper to absorb liquid through capillary action and heat of vaporization generated when the liquid evaporates. The aim of this study is to investigate the feasibility of realizing the transpiration-type thermoelectric-power-generating paper. To begin with, the type of paper used as raw material for the composite paper was examined, and the fabrication process was modified in order to obtain more efficient liquid absorption based on capillary action. Then, the absorbing ability of the liquid was evaluated. Next, the feasibility of thermoelectric power generation using the heat of vaporization was confirmed. Moreover, for more efficient thermoelectric conversion, multisheet structures were also studied. Through several experiments, the material's feasibility was verified, and it was confirmed that more power can be easily obtained through the use of multiple sheets. Specifically, a single sample spontaneously generated a temperature difference of up to 1.7 °C due to the heat of vaporization, generating an electromotive force of 36 μ V. From the sample with a five-sheet structure, an electromotive force of 356 μ V was obtained at a temperature difference of 2 °C. This material can be used in watery environments, such as rivers, lakes, and hot springs, and is expected to become a new energy-harvesting device. [ABSTRACT FROM AUTHOR]

The generation of a directed flow on the water surface in channels with sources and resonators of capillary oscillations is detected and investigated. The surface flow is caused by the movement of the liquid through the gaps between the resonators, as well as between the resonator and the channel walls, under a curved surface that is locally deformed by the sources of capillary vibrations, the transfer of energy of the locally curved surface of the liquid by capillary waves, and the transmission of wave momentum to the particles of the liquid surface in one direction. It is shown that capillary waves together with the energy transfer an excess surface, the flux density of which is equal to the flux of the surface deformation. Moving devices with a capillary-wave accelerator of the surface liquid flow are demonstrated. [ABSTRACT FROM AUTHOR]

Alveolar gas flow competition with pulmonary capillary blood flow for restricted space within lungs during mechanical ventilation, which is well known in respiratory physiology but neglected in everyday clinical practice, is thoroughly discussed in the paper. Anatomical and physiological conditions of oxygen and carbon dioxide counter-diffusion through alveolar-capillary barrier and the role of ventilation-perfusion relationship are described, and the possibility of blood flow displacement from opened alveoli with high pressure inside to poorly ventilated compartments of low intra-alveolar pressures is demonstrated. Commercially available metabolographic and real-time gas analysis monitors from different manufacturers were used for optimal PEEP adjustment by means of pulmonary VO2 and VCO2 shifts comparison, influence of patient volaemic status on the physiologic possibility of alveolar recruitment is discussed. Limitations of modern approach to the mechanical lung ventilation aimed at maximal lung opening in underlined and refuted with consideration on effective diffusion surface changes. Inefficacy of mechanical ventilation is especially obvious when acute respiratory failure follows ventilation-perfusion mismatch, like it appears in COVID-19. Partially it can explain discouraging mechanical ventilation outcomes during current pandemic. [ABSTRACT FROM AUTHOR]

This study numerically investigates the effect of the contact angle on the hydrodynamics of liquid–liquid slug flow in a capillary with an internal diameter of 2.4 mm. The finite volume method is used to solve the Navier–Stokes equation, and the volume-of-fluid method is employed for interface capturing. The contact angle varies from 13° to 169°. The aqueous phase is observed as a continuous medium, the organic phase is in a dispersed phase at low contact angles, and the aqueous phase is dispersed as a medium at high contact angles. The slug velocity is lower at partial wetting contact angles than at fully wetting or non-wetting contact angles. The vorticity inside the slug is higher at extreme contact angles (169°/13°) and becomes very pronounced near the interface. At the Weber number W e slug > 0.135 , fully developed film is observed. The thickness of this film increases as the interfacial tension decreases. Additionally, the pressure within the slug rises with an increase in interfacial tension. [ABSTRACT FROM AUTHOR]

The present work aims to evaluate the curing temperatures on the engineering and structural properties of the compressed earth blocks (CEBs) produced using natural pozzolan-based acid and alkali-geopolymers as alternative binders. A fixed 15 wt% of binder made with both acid and alkaline solution and natural pozzolan was used to stabilize the laterite soils. Prior, the 7 days aged pressed samples were oven-cured at 45, 55, 65, and 75 °C for 2 days before covering and storing at room temperature for 28 days. The obtained products were subjected to physicochemical, mechanical, structural and microstructural characterizations. These include optical microscopic (OM), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), percentage of water absorption, dry and wet compressive strengths, and capillary rate flow. The results revealed that the acidic binder was more efficient for the stabilization of the blocks compared to the alkaline one. The values of the dry compressive strength were 17.48, 26.50, 26.00, 25.00, and 25.00 MPa, and 9.36, 9.75, 11.64, 10.08, and 9.00 MPa at 25, 45, 55, 65, and 75 °C for the acidic binder stabilized block and alkaline binder blocks, respectively. Furthermore, at 45 and 55 °C in acid and alkaline mediums, respectively, the lowest capillary rise values of 3.30 and 6.25 for acid-stabilized and alkaline-stabilized CEBs were recorded, making this value the optimal temperature for the consolidation process during the stabilization of CEB-based lateritic using the alternative activating binder. However, curing temperatures above 45 °C for the acidic-stabilized CEBs and 55 °C for the alkaline-stabilized CEBs reduce the mechanical performance of the end products. [ABSTRACT FROM AUTHOR]

The revelation of thermal energy exchange mechanism of human body is challenging yet worthwhile, because it can clearly explain the changes in human symptoms and health status. Understanding, the heat transfer of the skin is significant because the skin is the foremost organ for the energy exchange between the human body and the environment. In order to diagnose the physiological conditions of human skin without causing any damage, it is necessary to use a non-invasive measurement technique by means of a conformal flexible sensor. The harmonic method can minimize the thermal-induced injury to the skin due to its low heat generating properties. A novel type of computational theory assessing skin thermal conductivity, blood perfusion rate of capillaries in the dermis, and superficial subcutaneous tissues was formed by combining the multi-medium thermal diffusion model and the bio-thermal model (Pennes equation). The skins of the hand back of six healthy subjects were measured. It was found that the results revealed no consistent changes in thermal conductivity were observed across genders and ages. The measured blood perfusion rates were within the range of human capillary flow. It was found that female subjects had a higher perfusion rate range (0.0058–0.0061 s−1) than male subjects (0.0032–0.0049 s−1), which is consistent with invasive medical studies about the gender difference in blood flow rates and stimulated effects in relaxation situations. [ABSTRACT FROM AUTHOR]

Particle trapping and manipulation have a wide range of applications in biotechnology and engineering. Recently, a flow-based, particle-trapping device called the Stokes trap was developed for trapping and control of small particles in the intersection of multiple branches in a microfluidic channel. This device can also be used to perform rheological experiments to determine the viscoelastic response of an emulsion or suspension. We show that besides these applications, the various flow modes produced by the Stokes trap are able to manipulate drop shapes and induce active mixing inside droplets. To this end, we analyse the dynamics of a droplet in a Stokes trap through boundary-integral simulations. We also explore the dynamic response of drop shape with respect to distinct external flow modes, which allows us to perform numerical experiments such as step strain and oscillatory extension. A linear controller is used to manipulate drop position, and the drop deformation is characterized by a spherical-harmonic decomposition. For small drop deformations, we observe a linear superposition of harmonics, which, surprisingly, seems to hold even for moderate deformations. This result indicates that such a device can be used for shape control of droplets. We also investigate how the different flow modes may be combined to induce mixing inside the droplets. The transient combination of modes produces an effective chaotic mixing, which is characterized by a mixing number. The mixing inside the droplet can be further enhanced for lower viscosity ratios and low, but non-zero capillary number and flow frequencies. [ABSTRACT FROM AUTHOR]

This study is devoted to investigating the dynamics of liquid driven by capillary force in a circular tube. A microscope was used to visualize the meniscus movement and the contact angle. The experiments were carried out with glycerin–water mixtures with viscosity ranging from 0.21 to 1.36 Pa∙s by filling the test liquid in a borosilicate glass tube with an inner diameter of 200 μm. The wetting distances of the meniscus with time were compared with the theoretical solution by considering the dynamic variation of contact angle. The results show that the theoretical solution agrees well with experimental data due to the reflection of the actual dynamic contact angle for the transient motions in the developing entrance region. In view of momentum balance, variations of dominant force according to the time were determined by separated inertial periods, such as inertial, inertial-viscous, and viscous time stages. [ABSTRACT FROM AUTHOR]

When two fluid drops touch, they coalesce due to surface tension. At early times, there is only a relatively small fluid bridge joining the drops. An asymptotic solution is presented for an inertial regime of early-time coalescence, in which inertial forces balance surface tension at leading order. It is demonstrated that viscosity nevertheless has a leading-order effect. Radial momentum is created at the tightly curved edge of the fluid bridge by the net force $2\gamma$ (per unit length) due to surface tension. This momentum is left behind the radially expanding bridge edge in a thin viscous wake. The divergent volume flux in the wake entrains fluid from above and below the bridge, and drives an inviscid irrotational flow in the drops on the scale of the bridge radius. This flow widens the gap between the drops ahead of the bridge, and the larger gap width results in a lower rate of coalescence. Including viscosity in this way improves the agreement between theory and the available experimental and numerical data. [ABSTRACT FROM AUTHOR]

Compounds containing one carbon atom or no carbon-carbon bond (C1 compounds), such as trimethylamine and methanol, are important climate relevant gases in the atmosphere and play key roles in global warming. The ocean is a significant source or sink of such compounds, while the concentrations of trimethylamine and methanol in seawater remain largely unconstrained due to the analytical challenges involved. Therefore, it is necessary to establish a continuous, rapid and sensitive method for the determination of these compounds with high polarity, volatility or solubility at low seawater concentrations. Here we developed a purge and trap system, coupled to a gas chromatography equipped with dual nitrogen phosphorus detector (NPD) and flame ionization detector (FID) for the simultaneous online analysis of trimethylamine and methanol at nanomolar range using a small sample volume (~ 10 mL). The dual detection of trimethylamine and methanol with NPD or FID was achieved by installing a capillary flow splitter between the capillary column and detectors. After modification and optimization of the setup and conditions, excellent linearity (R² > 0.99) and repeatability (< 6%) were obtained for both compounds; the detection limits for trimethylamine andmethanol were 0.3 nM and 17.6 nM, respectively. Using this method, water samples collected from coastal and open ocean were analyzed; trimethylamine and methanol concentrations ranged from 0.6 to 18.8 nM and 26.0 to 256.2 nM, respectively. Collectively, this method allowed for online, rapid, sensitive and simultaneous quantification of trace trimethylamine and methanol concentrations with low-cost instrumentation and small sample volume, which makes it promising for further application in volatile compounds analysis in marine environments. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a compressible formulation for dealing with 2D/3D compressible interfacial flows. It integrates a monolithic solver to achieve robust velocity–pressure coupling, ensuring precision and stability across diverse fluid flow conditions, including incompressible and compressible single-phase and two-phase flows. Validation of the model is conducted through various test scenarios, including Sod's shock tube problem, isothermal viscous two-phase flows without capillary effects, and the impact of drops on viscous liquid films. The results highlight the ability of the scheme to handle compressible flow situations with capillary effects, which are important in computational fluid dynamics (CFD). [ABSTRACT FROM AUTHOR]

The Yungang Grottoes, one of China's most notable cultural heritage sites, are located in sandstone strata. The main causes of deterioration observed in the field are associated with moisture action, which greatly affects the long-term performance of the material. In particular, for immovable cultural heritage that is exposed to natural climatic fluctuations throughout the year, interaction with water vapor cannot be avoided. To obtain an insight into the water vapor transmission properties of local sandstone, a series of laboratory tests were conducted using the wet-cup method. The correlation of water vapor transmission with environmental relative humidity and pore structure was examined. The results indicate that as the relative humidity increased, the diffusion coefficient increased considerably due to the contribution of capillary condensate flow. In addition, a positive relationship was found between the diffusion coefficient and open porosity. The water vapor diffusion in sandstone occurred in transitory mode and the diffusion coefficient was estimated from the average pore radius. The calculated values were two orders of magnitude larger than those measured in the tests, reflecting the complex microstructural features concerning diffusion paths and area. The weathering processes constantly alter the sandstone's diffusion parameters, causing various damages in the Yungang Grottoes. [ABSTRACT FROM AUTHOR]

Aims: Sulfatide is a chaperone for insulin manufacturing in beta cells. Here we explore whether the blood glucose values normally could be associated with this sphingolipid and especially two of its building enzymes CERS2 and CERS6. Both T1D and T2D have low blood sulfatide levels, and insulin resistance on beta cells at clinical diagnosis. Furthermore, we examined islet pericytes for sulfatide, and beta‐cell receptors for GLP‐1, both of which are related to the insulin production. Materials and Methods: We examined mRNA levels in islets from the DiViD and nPOD studies, performed genetic association analyses, and histologically investigated pericytes in the islets for sulfatide. Results: Polymorphisms of the gene encoding the CERS6 enzyme responsible for synthesising dihydroceramide, a precursor to sulfatide, are associated with random blood glucose values in non‐diabetic persons. This fits well with our finding of sulfatide in pericytes in the islets, which regulates the capillary blood flow in the islets of Langerhans, which is important for oxygen supply to insulin production. In the islets of newly diagnosed T1D patients, we observed low levels of GLP‐1 receptors; this may explain the insulin resistance in their beta cells and their low insulin production. In T2D patients, we identified associated polymorphisms in both CERS2 and CERS6. Conclusions: Here, we describe several polymorphisms in sulfatide enzymes related to blood glucose levels and HbA1c in non‐diabetic individuals. Islet pericytes from such persons contain sulfatide. Furthermore, low insulin secretion in newly diagnosed T1D may be explained by beta‐cell insulin resistance due to low levels of GLP‐1 receptors. [ABSTRACT FROM AUTHOR]

This study investigates the energy signature associated with multiphase flow in porous media displacement regimes. We proposed that net efficiency, as the conversion of external work applied to surface energy generated, provides new insights into the transition of flow regimes. The combined effects of wettability and flow rates on immiscible fluid‐fluid displacement is experimentally investigated using high‐resolution imaging in microfluidic flow cells, which allows for tracking the evolution of interfacial area under applied external work. Our study focuses on the morphology of invasion patterns and the efficiency of conversion of external work to surface energy. The results show that the morphology of invasion patterns under unfavorable displacement condition is sharper than that under favorable displacement condition with larger ratios of length and width for fingers. The efficiency of conversion of external work to surface energy decreases with the increase of contact angles and reduces greatly with the increase of Capillary numbers. With favorable displacement conditions, the efficiency of conversion is consistently higher than that for unfavorable displacement. The trends of external work and surface energy serve as a signature of the transition between different flow regimes, which exhibits alteration especially at low Capillary numbers. The findings highlight the importance of wettability and flow rates in determining the efficiency of fluid‐fluid displacement in porous media. Understanding the energy signature associated with multiphase flow can have implications for various geoscience applications, such as oil/gas recovery, groundwater remediation, and underground energy storage. Plain Language Summary: This study investigates how different factors affect the movement of fluids in porous materials. Specifically, we looked at how the wetness of the material and the rate at which the fluids flow influences the displacement of one fluid by another. We conducted experiments using high‐resolution imaging in small channels to observe the patterns of fluid movement and calculate the energy changes involved. The results showed that the shape of the fluid invasion patterns differed depending on the wetness and the type of fluids used. In some cases, the invading fluid formed long, narrow fingers, while in others, it spread out more evenly. The efficiency of converting external work into surface energy also varied depending on the wetness and flow rates. Higher wetness and lower flow rates generally resulted in higher conversion efficiency. We also found that the signature of external work and surface energy served as indicators of the transition between different flow regimes. By analyzing these energy signals, we were able to determine the nature of the fluid displacement. Understanding how fluids move in porous materials is important for various applications, such as recovering oil and gas, cleaning contaminated groundwater, and storing energy. By studying the energy signature associated with multiphase flow in porous media, we can gain insights into the efficiency and behavior of fluid displacement in porous materials. This knowledge can help improve the design and optimization of subsurface engineering technologies. Key Points: We experimentally investigates the morphology of invasion patterns and the efficiency of conversion of external work to surface energyThe efficiency of conversion of external work to surface energy decreases with the increase of contact angles and notably reduces with increasing capillary numberThe trends of external work and surface energy serve as a signature of the transition between different flow regimes for multiphase flow [ABSTRACT FROM AUTHOR]

Abstract The evaporation of particle‐free silver ink droplets on heated substrates directly impacts the morphology of the resultant silver particles and electrically conductive inkjet‐printed films. In this work, COMSOL Multiphysics simulations of the droplet evaporation process are used to help explain the fluidic processes responsible for the experimental observations. The results show that the silver particle morphology depends on its location within the evaporating droplet where large particles (3 to 5 µm) accumulate at the center and smaller ones (1 to 2 µm) in the area beyond the central region. The smallest particles (≈500 nm) are near the contact line. Without the fluoro‐surfactant FS‐31, an inner ring with 3 µm particles also appears within the evaporating droplet. The large particles at the central region originate from the fluid near the droplet's apex due to the accumulation of polyacrylamide in the concentrated ethylene glycol solvent near the flow‐abundant apex. Furthermore, the capillary flow along the fluid–air interface transports silver ions and particles throughout the droplet, causing the larger particles to fall onto the substrate at the central vortex, forming the inner ring. The simulations also demonstrate that the evaporating droplet heterogeneously accumulates ethylene glycol in a sandhill formation at the bottom center.

This study is devoted to investigating the dynamics of liquid driven by capillary force in a circular tube. A microscope was used to visualize the meniscus movement and the contact angle. The experiments were carried out with glycerin–water mixtures with viscosity ranging from 0.21 to 1.36 Pa∙s by filling the test liquid in a borosilicate glass tube with an inner diameter of 200 μm. The wetting distances of the meniscus with time were compared with the theoretical solution by considering the dynamic variation of contact angle. The results show that the theoretical solution agrees well with experimental data due to the reflection of the actual dynamic contact angle for the transient motions in the developing entrance region. In view of momentum balance, variations of dominant force according to the time were determined by separated inertial periods, such as inertial, inertial-viscous, and viscous time stages.

Purpose: This study aimed to compare the anatomic and functional results of optical coherence tomography angiography (OCTA)-guided half-dose photodynamic therapy (PDT) versus indocyanine green angiography (ICGA)-guided PDT in eyes with acute central serous chorioretinopathy (CSC). Methods: One hundred and thirty-one eyes of 131 patients with acute central serous chorioretinopathy (CSC) were recruited, and randomly assigned to the OCTA-guided group and ICGA-guided group. The primary outcome measures were the rates of complete subretinal fluid (SRF) resolution at 1 month, 3 months, and 6 months. The secondary outcomes included best-corrected visual acuity (BCVA), central retinal thickness (CRT), choroidal capillary flow deficit density at each scheduled visit, and recurrence rate of SRF at 3 months and 6 months. Results: There were 110 eyes that finished the follow-up, with 56 eyes in the OCTA-guided group and 54 eyes in the ICGA guided group. OCTA-guided PDT was demonstrated to be noninferior to ICGA-guided PDT for SRF resolution rate at 1 months and 6 months (P = 0.021 and P = 0.037), but not at 3 months for acute CSC (P = 0.247). The average CRT of the ICGA-guided group was significantly lower than that of the OCTA-guided group at 3-month visit (P = 0.046), but no significant difference was found between them at the 1-month and 6-month visits (P = 0.891 and 0.527). There was no significant difference between the two groups for BCVA (P = 0.359, 0.700, and 0.143, respectively) and the deficit area on CC (P = 0.537, 0.744,and 0.604, respectively) at 1, 3, and 6 months. Conclusion: OCTA may replace ICGA to guide PDT for the treatment of acute CSC and their follow-up. [ABSTRACT FROM AUTHOR]

When the temperature rises during the brazing process, only the brazing material melts because of its low melting point. Several analytical approaches have been used to describe filler flow in channels and the progression of erosion grooves. However, only a few studies have examined filler-flow behavior in microgrooves during brazing. In this study, a computational model was constructed to examine the flow in microgrooves on an extruded material's surface. The capillary flow of the aluminum brazing material was numerically analyzed to investigate the physical properties and surface behavior. Specifically, the surface-tension flow behavior was analyzed by simulating various cross-sectional shapes of the channel grooves and various contact angles of the filler. The effects of various parameters, such as viscosity and boundary conditions, on the filler flow were also analyzed. When the cross-sectional area of the channel groove increases, the filler-flow velocity increases, and the rate of unsteady fluctuation increases with the increasing filler tip velocity. The driving force of the filler flow in the channel groove is considered to be (1) the surface tension, which is based on the filler free-surface curvature, or (2) the dynamic change in the shape of the meniscus, which can be unsteady and induced by Rayleigh–Taylor instability. As the cross-sectional area of the channel groove increases, the capillary force based on the dynamic change in meniscus shape dominates the unsteady change in filler tip velocity, rather than the surface tension based on the filler free-surface curvature formed in the groove. [ABSTRACT FROM AUTHOR]

Surfactant-free capillary foams (CFs) are known to be remarkably tolerant to oil, and possess unique stability and flow properties. These properties result from the presence of oil-and-particle-coated bubbles that are interconnected by a dense particle–oil capillary network. In this work, we present a study of the dynamics of capillary foams flowing through a porous micromodel. We determine that despite the presence of oil–particle networks, CFs can flow through a microporous environment and that above a threshold flowrate, >80% of foam pumped through the micromodel can be recovered. In addition, we highlight the absence of steady state in CF flow and identify the underlying phenomena including the increasing apparent viscosity, reconfigurable flow paths, and intermittent clogging of the micromodel from an oil–particle composite and bubbles trapped in pores. We also characterize bubble dynamics and show that CFs surprisingly exhibit the same bubble generation and destruction mechanisms as classical foams despite the absence of surfactants. Our observations suggest that the porous medium plays a key role in generating uniformly sized bubbles and that capillary foams in a microporous environment tend to reconfigure their flow paths in a manner that may provide opportunities for increased sweep efficiency in enhanced oil recovery. [ABSTRACT FROM AUTHOR]

In the realm of abrasive flow machining (AFM), precise finishing and maintaining dimensional accuracy have remained challenging due to non-uniformities in the AFM process and complexities associated with the abrasive media's shear viscosity and wall slip behavior. By addressing these challenges, this study introduces a comprehensive framework, combining theoretical foundations, measurement techniques, and experimental setups. Utilizing capillary flow, a novel compensation strategy is incorporated within the Mooney method to counter entrance pressure drop effects. This enhanced capillary flow method emerges as a promising alternative to the conventional Cox–Merz empirical rule, enabling precise characterization of wall slip behavior and shear viscosity, particularly at elevated shear rates. The abrasive media exhibit a Navier nonlinear wall slip, as highlighted by the Mooney method. Rigorous verification of the proposed methodologies and models against supplemental experiments showcases a high degree of congruence between predicted and observed results, emphasizing their accuracy and broad application potential in AFM. This research illuminates the intricacies of the abrasive media's behavior, accentuating the need for meticulous characterization, and provides a robust foundation for genuine modeling and predictions in material removal within AFM. [ABSTRACT FROM AUTHOR]

Capillary flow is known to be non-homogenous between vessels and variable over time, for reasons that are poorly understood. The local properties of individual vessels have been shown to have limited explanatory power in this regard. This exploratory study investigates the association of network-level properties such as vessel depth, branch order, and distance from the feeding arteriole with capillary flow. Detailed network connectivity analysis was undertaken in 3 healthy young subjects using flood-illuminated adaptive optics retinal imaging, with axial depth of vessels determined via optical coherence tomography angiography. Forty-one out of 70 vessels studied were of terminal capillary type, i.e. fed from an arterial junction and drained by a venous junction. Approximately half of vessel junctions were amenable to fitting with a model of relative branch diameters, with only a few adhering to Murray's Law. A key parameter of the model (the junction exponent) was found to be inversely related to the average velocity (r = -0.59, p = 0.015) and trough velocity (r = -0.67, p = 0.004) in downstream vessels. Aspects of cellular flow, such as the minimum velocity, were also moderately correlated (r = 0.46, p = 0.009) with distance to the upstream feeding arteriole. Overall, this study shows that capillary network topology contributes significantly to the flow variability in retinal capillaries in human eyes. Understanding the heterogeneity in capillary flow is an important first step before pathological flow states can be properly understood. These results show that flow within capillary vessels is not affected by vessel depths but significantly influenced by the upstream feeder distance as well as the downstream vessel junction exponents, but there remains much to be uncovered regarding healthy capillary flow. [ABSTRACT FROM AUTHOR]

Capillary invasion of liquid is a spontaneous phenomenon that occurs at length scales smaller than the capillary length. By means of capillary action, numerous applications have been developed. We investigate the time-dependent displacement of a Newtonian oil using viscoelastic polyethylene oxide solutions. The setup implies a capillary tube in a horizontal configuration that was partially prefilled with oil. We emphasize the prefilling liquid’s role in the dynamics of the system and show the influence of the displacing liquid’s viscoelastic properties. We find significant changes in the capillary regime as the displacing liquid’s viscoelastic properties change. [ABSTRACT FROM AUTHOR]