Network Of Tubes Research Articles

Selective and Marked Blockade of Endothelial Sprouting Behavior Using Paclitaxel and Related Pharmacologic Agents

Whether alterations in the microtubule cytoskeleton affect the ability of endothelial cells (ECs) to sprout and form branching networks of tubes was investigated in this study. Bioassays of human EC tubulogenesis, where both sprouting behavior and lumen formation can be rigorously evaluated, were used to demonstrate that addition of the microtubule-stabilizing drugs, paclitaxel, docetaxel, ixabepilone, and epothilone B, completely interferes with EC tip cells and sprouting behavior, while allowing for EC lumen formation. In bioassays mimicking vasculogenesis using single or aggregated ECs, these drugs induce ring-like lumens from single cells or cyst-like spherical lumens from multicellular aggregates with no evidence of EC sprouting behavior. Remarkably, treatment of these cultures with a low dose of the microtubule-destabilizing drug, vinblastine, led to an identical result, with complete blockade of EC sprouting, but allowing for EC lumen formation. Administration of paclitaxel invivo markedly interfered with angiogenic sprouting behavior in developing mouse retina, providing corroboration. These findings reveal novel biological activities for pharmacologic agents that are widely utilized in multidrug chemotherapeutic regimens for the treatment of human malignant cancers. Overall, this work demonstrates that manipulation of microtubule stability selectively interferes with the ability of ECs to sprout, a necessary step to initiate and form branched capillary tube networks.

Action and inertia in the study of hyphal growth

Hyphae are microscopic filaments that elongate and branch to create networks of interconnected tubes. Understanding how they work remains a formidable challenge in experimental mycology. Important advances in hyphal research in the 20th century came from electron microscopy, which revealed clusters of cytoplasmic vesicles in the cell apex, and biochemical studies that identified the cell wall materials that are assembled at the tip. Early genetic experiments on hyphae based on mutant analysis were disappointing and provided little information on the relationship between genotype and phenotype. Progress has come more recently, in the first decades of this century, by combining the techniques of molecular genetics with modern imaging methods. Live-cell imaging has allowed us to study the dynamics of cell components in strains of fungi engineered with plasmids encoding proteins fused to fluorescent probes. This technology has provided significant insights on the growth process and yet the fundamentals of hyphal growth remain elusive.

Tropoelastin Promotes the Formation of Dense, Interconnected Endothelial Networks.

Tropoelastin, the soluble precursor of elastin, has been used for regenerative and wound healing purposes and noted for its ability to accelerate wound repair by enhancing vascularization at the site of implantation. However, it is not clear whether these effects are directly due to the interaction of tropoelastin with endothelial cells or communicated to endothelial cells following interactions between tropoelastin and neighboring cells, such as mesenchymal stem cells (MSCs). We adapted an endothelial tube formation assay to model in vivo vascularization with the goal of exploring the stimulatory mechanism of tropoelastin. In the presence of tropoelastin, endothelial cells formed less tubes, with reduced spreading into capillary-like networks. In contrast, conditioned media from MSCs that had been cultured on tropoelastin enhanced the formation of more dense, complex, and interconnected endothelial tube networks. This pro-angiogenic effect of tropoelastin is mediated indirectly through the action of tropoelastin on co-cultured cells. We conclude that tropoelastin inhibits endothelial tube formation, and that this effect is reversed by pro-angiogenic crosstalk from tropoelastin-treated MSCs. Furthermore, we find that the known in vivo pro-angiogenic effects of tropoelastin can be modeled in vitro, highlighting the value of tropoelastin as an indirect mediator of angiogenesis.

An Interactive Automation for Human Biliary Tree Diagnosis Using Computer Vision

The biliary tree is a network of tubes that connects the liver to the gallbladder, an organ right beneath it. The bile duct is the major tube in the biliary tree. The dilatation of a bile duct is a key indicator for more major problems in the human body, such as stones and tumors, which are frequently caused by the pancreas or the papilla of vater. The detection of bile duct dilatation can be challenging for beginner or untrained medical personnel in many circumstances. Even professionals are unable to detect bile duct dilatation with the naked eye. This research presents a unique vision-based model for biliary tree initial diagnosis. To segment the biliary tree from the Magnetic Resonance Image, the framework used different image processing approaches (MRI). After the image’s region of interest was segmented, numerous calculations were performed on it to extract 10 features, including major and minor axes, bile duct area, biliary tree area, compactness, and some textural features (contrast, mean, variance and correlation). This study used a database of images from King Hussein Medical Center in Amman, Jordan, which included 200 MRI images, 100 normal cases, and 100 patients with dilated bile ducts. After the characteristics are extracted, various classifiers are used to determine the patients’ condition in terms of their health (normal or dilated). The findings demonstrate that the extracted features perform well with all classifiers in terms of accuracy and area under the curve. This study is unique in that it uses an automated approach to segment the biliary tree from MRI images, as well as scientifically correlating retrieved features with biliary tree status that has never been done before in the literature.

Tunable network sound absorber based on additive manufacturing.

Broadband sound absorption at low frequencies is always a challenge owing to the strong penetrability of acoustic waves. Combining detuned components, such as coupling curled Fabry-Pérot channels, has been proposed for broadband sound absorption. However, the components of the structure are generally arranged in parallel, so that it is difficult to assemble channels with gradient lengths into a compact and thin absorber. Tube networks, which can be seen as broadband and low-frequency sound absorbers, can circumvent this problem. However, the network absorber can only work at fixed frequencies once fabricated. Here, we propose a tunable low-frequency sound absorber consisting of honeycomb plates and detached chips and fabricate it by additive manufacturing. By replacing chips of the sound absorber, we experimentally validate different sound absorption spectrums. A low reduced frequency model and genetic algorithm are developed to design the chips according to targeted absorption spectrums. Moreover, we theoretically study the impact of radius of tube on sound absorption and extend the two-dimensional network to a three-dimensional structure. The remarkable efficiency and versatility of the tunable network sound absorber may pave the way for programmed absorbing material design.

Multi-occupation segregation through London's tube network

As an extension of public space, the public transport system in modern society is an arena for cross-group interactions. Uncovering social segregation in public transport space is an essential step in shaping a socially sustainable transport system. Based on 2011 origin–destination flow data for London, we simulate the working flows between each pair of connected tube stations for every occupation with minimised transfer times and travelling hours and calculate the multi-occupation segregation index for all tube stations and segments. This segregation index captures the density and diversity aspects of the working population. The results demonstrate that segregation levels vary significantly across stations, lines, and segments. Transfer stations and tube segments in the city centre do not necessarily have lower levels of segregation. Those stations or segments close to a terminus can also be socially inclusive, e.g., Heathrow. Victoria is the line with the lowest levels of segregation, and Green Park is the most socially inclusive station during commuting peaks. The proposed mapping approach demonstrates the spatial complexity in the social performance of the public transport system and provides a tool for implementing relevant policy with improved precision.

Tubular Carbon Nitride with Hierarchical Network: Localized Charge Carrier Generation and Reduced Charge Recombination for High‐Performance Photocatalysis of H2 and H2O2 Production

Polymeric carbon nitride (PCN), as an appealing metal‐free and low‐cost photocatalyst for solar‐to‐fuel conversion, is still suffering from insufficient light‐harvesting efficiency and short excited state lifetime of electron–hole pairs. Herein, a 3D hierarchical network of carbon nitride tubes (NCNT) with intercrossing few‐layer tubes of uniform diameter, synthesized by a synergistic strategy of tailoring the chemical and hydrogen bond, is reported. This hollow network structure facilitates the internal light reflection, thus promoting the light‐induced electron–hole pair generation. Moreover, the few‐layer NCNT with nitrogen defects effectively decreases the undesired electron–hole recombination. These advantages are disclosed by experimental spectra and finite difference time domain (FDTD) simulations and density functional theory (DFT) calculations. Impressively, the optimized NCNT exhibits almost 32 times the photocatalytic hydrogen evolution ability (8.6 mmol h−1 g−1) and 4 times (485.7 μmol h−1 g−1) the hydrogen peroxide production of those of bulk PCN, respectively. This work provides a new strategy to construct a hierarchical nanostructure of a high‐performance carbon nitride photocatalyst through enhancing the solar‐light capture and conversion.

Diffusion of Disinformation on The You Tube Network about Chinese Covid-19: Based on Influential Spreaders and Types of Information

Diffusion of Disinformation on The You Tube Network about Chinese Covid-19: Based on Influential Spreaders and Types of Information

Numerical solution of the viscous flows in a network of thin tubes: Equations on the graph

A non-stationary flow in a network of thin tubes is considered. Its one-dimensional approximation was proposed in a paper by G. Panasenko and K. Pileckas, Flows in a tube structure: equation on the graph (Panasenko and Pileckas, 2014 [19]). It consists of a set of equations with weakly singular kernels, on a graph, for the macroscopic pressure. A new difference scheme for this problem is proposed. Several variants are discussed. Stability and convergence are carefully investigated, theoretically and numerically. In addition, numerical results are compared to the direct numerical solution of the full dimension Navier-Stokes equations.

The Movement of CO2 Through the Frozen World of Sea Ice

Every winter, a frozen blanket known as sea ice completely covers the Arctic Ocean. For centuries, sea ice has been viewed as a solid lid on the ocean that acts as a boundary to block gases traveling between the ocean and the atmosphere. However, scientific discoveries over recent years have shown that sea ice is more like a sponge, a porous substance that is also home to microscopic life forms. The pores in sea ice are filled with very salty liquid called brine that is rich in carbon dioxide (CO2). These liquid pockets create a network of tubes or channels that move gases like CO2, similar to the way veins and arteries move blood in our bodies. In this article, you will discover how CO2 enters, exits, and is transformed in one of the harshest environments on Earth.

Hierarchical Microchannel Carbons Derived from Biological Phloem Tissues as High-Performance Anode for Lithium-Ion Batteries

With the upgrading of consumption, the existing carbon-based anode materials are facing the major challenges of high preparation cost and low initial Coulomb efficiency. The fast-growing and developed sieve tube network is an inspiration to transform cattail phloem tissue (CPT) into a high-performance carbon-based anode for lithium-ion battery. In this study, porous carbon materials from CPT with abundant microchannel and nanochannel were prepared by a top-down strategy combined with an indispensable passivation process. The sidewall and end of the sieve tube are fully covered by a large number of pore structures and various supporting cells, thus ensuring the stiffness and tensile strength of phloem tissue. And benefiting from the neoteric hierarchical porous structure without Li⁺ trapping sites, the cells with CPT anode showed high electrochemical performance. For the passivated CPT electrode, the reversible capacity increased to 321.6 mAh/g, and the initial Coulomb efficiency was 1.47 times higher than that of the passivated CPT electrode. The CPT exhibits excellent rate performance under high current, which indicates that the abundant pore structure on the surface of the sieve tube is an effective measure to improve ion diffusion. Besides, the generation mechanism of high-performance CPT is analyzed through microstructure characterization. The improvement of electrochemical performance of CPT in this work has provided a clear strategy for the application of resource-rich natural biomass to electrochemical products.

The Role of Mitochondrial Quality Control in Cardiac Ischemia/Reperfusion Injury.

A healthy mitochondrial network produces a large amount of ATP and biosynthetic intermediates to provide sufficient energy for myocardium and maintain normal cell metabolism. Mitochondria form a dynamic and interconnected network involved in various cellular metabolic signaling pathways. As mitochondria are damaged, controlling mitochondrial quantity and quality is activated by changing their morphology and tube network structure, mitophagy, and biogenesis to replenish a healthy mitochondrial network to preserve cell function. There is no doubt that mitochondrial dysfunction has become a key factor in many diseases. Ischemia/reperfusion (IR) injury is a pathological manifestation of various heart diseases. Cardiac ischemia causes temporary tissue and organelle damage. Although reperfusion is essential to compensate for nutrient deficiency, blood flow restoration inconsequently further kills the previously ischemic cardiomyocytes. To date, dysfunctional mitochondria and disturbed mitochondrial quality control have been identified as critical IR injury mechanisms. Many researchers have detected abnormal mitochondrial morphology and mitophagy, as well as aberrant levels and activity of mitochondrial biogenesis factors in the IR injury model. Although mitochondrial damage is well-known in myocardial IR injury, the causal relationship between abnormal mitochondrial quality control and IR injury has not been established. This review briefly describes the molecular mechanisms of mitochondrial quality control, summarizes our current understanding of the complex role of mitochondrial quality control in IR injury, and finally speculates on the possibility of targeted control of mitochondria and the methods available to mitigate IR injury.

Service: Retracted and Reframed.

Service: Retracted and Reframed.

Residential Buildings’ Foundations as a Ground Heat Exchanger and Comparison among Different Types in a Moderate Climate Country

Shallow Geothermal Energy Systems (SGESs) constitute Renewable Energy Systems (RES), which find application in the residential sector through the use of Ground Source Heat Pumps (GSHPs). GSHPs are associated with Ground Heat Exchangers (GHEs), whereby heat is gained/lost through a network of tubes into the ground. GSHPs have failed to flourish in the RES market due to their high initial costs and long payback periods. In this study, the use of Energy Geo-Structure (EGS) systems, namely, the foundation (or energy) piles and the foundation bed of a residential building in Cyprus, was computationally modeled in the COMSOL Multiphysics software. First, the single-houses’ trend in number of units and area in Cyprus was examined and a theoretically typical house with nearly Zero Energy Building (nZEB) characteristics was considered. The heating and cooling loads were estimated in the TRNSYS software environment and used as inputs to investigate the performance of the GSHP/GHE systems. Both systems were shown to exhibit steady performance and high Coefficient of Performance (COP) values, making them an alternative RES solution for residential building integration. Next, the systems were economically evaluated through a comparison with a convectional Air Source Heat Pump (ASHP) system. The economic analysis showed that the cost of the suggested conversions of the foundation elements into GHEs had short payback periods. Consequently, either using the foundation piles or bed as a GHE is a profitable investment and an alternative to conventional RES.

Tomographic PIV analysis of physiological flow conditions in a patient-specific arteriovenous fistula

The arteriovenous fistula (AVF), which is a vasculature created for end-stage renal disease patients who require haemodialysis, is susceptible to many vascular diseases. It is well known that disturbed hemodynamics is a factor in the initiation of vascular disease; however, only a limited number of experimental studies have been conducted to assess the flow behaviour within the AVF. The current study is an investigation of the complex three-dimensional flow within a physiological AVF geometry, using tomographic particle image velocimetry. To this end, a benchtop model of a patient-specific geometry was created by casting silicone around a soluble 3D print of the vessels. The patient-specific boundary conditions were reproduced by driving a refractive-index matched working fluid from a pulsatile pump, which was connected to the model via a tubing network inclusive of valves and compliance chambers. The seeded working fluid was illuminated with a 1 kHz double-pulsed laser, and four high-speed cameras placed at optimised locations were used to capture the particle images, with the volume reconstructions refined by a 3D internal mask created using morphological operations. The velocity magnitude contour plots of the resulting vector field revealed two zones of low velocity in the anastomosis, while locations of high turbulent kinetic energy are observed in the anastomosis and venous regions. These results suggested that the collision of the two opposing inlet flows and the curvature at the anastomosis cause disturbance in the flow that is carried downstream.

Case studies of operational failures of vanadium redox flow battery stacks, diagnoses and remedial actions

Vanadium redox flow batteries show enormous scope in large-scale storage and load balancing of energy from intermittent renewable energy sources. Although a number of studies have been published in the last two decades on various aspects of these flow batteries, very few have reported on practical aspects such as design considerations, guidelines and operational failures. Adequate attention to engineering aspects, failure detection and diagnosis are essential for smooth operation of the flow batteries. This paper discusses a few case studies of operational failures during the design and development of kilowatt-scale flow batteries together with their diagnoses and remedial actions. Specifically, failures in the membrane, tubing network and state of electrode have been discussed and suitable recommendations and guidelines are given to avoid these. In each case, rectification of the malfunction was confirmed through results obtained using electrochemical testing protocols established in previous studies. Based on these experiences, good practice guidelines have been recommended for proper fabrication, assembly and characterization of stacks.

An experimental and numerical study of feasibility of a novel technology to manufacture hot stamping dies with pre-constructed tube network

The cooling system is a critical element in tooling for hot stamping high-strength aluminium alloys, for which very high quenching rates are required to ensure a supersaturated solid solution state in formed parts. To enhance cooling, ducts within the tools should be close and conformal to the surface die profile. Currently, ducts with curved profiles are made by drilling short straight lengths in die segments which are clamped together to form a complete die, which is expensive and hard to achieve the shape of duct with best cooling performance. To address these disadvantages, a novel method which enables efficient manufacture of conformal cooling systems by embedding a network of tubular cooling ducts within a cast matrix is presented in this paper. The feasibility of the proposed method of making ducts in the hot stamping die is demonstrated. Both experimental and computer-based die quenching tests using heated aluminium test pieces were undertaken to determine the cooling performance of a laboratory-scale tool set with cooling ducts. Simulations using the validated FE model were performed to investigate the effects of cross-sectional geometry, material and duct layout, on the quenching performance of the tools. It was found that ducts made of mild steel perform sufficiently well to make the use of high conductivity copper unnecessary. For a flat die surface, square section ducts provided highest cooling rates in comparison with circular and diagonal ones. The uniformity of die temperature increases with the decreased distance between neighbouring ducts, which indicates that a minimal gap is recommended without deteriorating tool strength. The developed tooling technology has the potential to provide a low-cost, highly efficient method of making conformal cooling ducts because the hot stamping die of high-strength aluminium alloy panels requires larger dimension, greater complexity and higher quenching rates.

Umbilical cord-derived pericytes present an optimal cell population for vascular tissue engineering in newborns

Abstract Introduction Newborns with severe congenital heart defects often require implantation of a graft to replace defective arteries and valves soon after birth. The current materials used for grafts all possess an inability to integrate and grow with the patient, resulting in repeated surgical interventions to replace failed grafts. Tissue engineering has aimed to address this limitation by seeding grafts with cells to create a biological “living” graft, however, the choice of cells is a critical aspect that is often not thoroughly explored, and thus limited success has been achieved. Here we identify and characterise a novel umbilical cord-derived pericyte (UCP) population with enhanced therapeutic potential for vascular tissue engineering in patients with CHD. Methods and results CD31-/NG2+ UCPs were isolated from the umbilical cord by explant outgrowth, and purified using magnetic activated cell sorting and flow cytometry. Doubling time and viability was quantified by counting cells on consecutive days for 1 week. UCPs maintained a viability of above 90% throughout culture and demonstrated a population doubling time of 50–70 hours. To assess angiogenic potential, endothelial-fibroblast cocultures were treated with UCP-conditioned medium and the cumulative tube network was measured. UCPs induced an increase of 9.9mm±2mm in tube length whereas mesenchymal stromal cells (MSCs) only induced a 1.8±1mm increase. The promigratory effect of UCPs on endothelial cells was tested using a scratch assay treated with conditioned medium. Endothelial cells treated with UCP conditioned medium demonstrated a 3.0±0.2-fold increase in migration compared with endothelial cells treated with MSC conditioned medium. Finally, the capability of UCPs to form functional vascular tissue was assessed using a differentiation and contraction assay. Differentiated cells demonstrated an increased expression of vascular smooth muscle markers alpha smooth muscle actin (aSMA; 7.1±1.6 protein fold change vs control), calponin (22.5±3.9 protein fold change vs control), Transgelin (7.4±1.6 protein fold change vs control) and smooth muscle myosin heavy chain (SM-MHC; 1.7±0.1 protein fold change vs control). Both differentiated and undifferentiated UCPs exhibited a contractile response to vasoactive peptide endothelin-1, however, differentiated UCPs demonstrated a 65.3±14.9% increase in contraction from the inhibited state, compared to 37.3±10.7% for undifferentiated UCPs. Conclusion UCPs are an ideal autologous cell population for vascular tissue engineering in newborns. They are capable of forming functional vascular tissue and can be expanded sufficiently within the surgical window for CHD treatment. Furthermore, UCPs hold distinct advantages over MSCs. Namely, UCPs induce a greater increase in endothelial migration and network formation, which is essential for endothelisation and perfusion of engineered tissue. Funding Acknowledgement Type of funding source: Other. Main funding source(s): Heart Research UK

Defining an Upstream VEGF (Vascular Endothelial Growth Factor) Priming Signature for Downstream Factor-Induced Endothelial Cell-Pericyte Tube Network Coassembly.

In this work, we have sought to define growth factor requirements and the signaling basis for different stages of human vascular morphogenesis and maturation. Approach and Results: Using a serum-free model of endothelial cell (EC) tube morphogenesis in 3-dimensional collagen matrices that depends on a 5 growth factor combination, SCF (stem cell factor), IL (interleukin)-3, SDF (stromal-derived factor)-1α, FGF (fibroblast growth factor)-2, and insulin (factors), we demonstrate that VEGF (vascular endothelial growth factor) pretreatment of ECs for 8 hours (ie, VEGF priming) leads to marked increases in the EC response to the factors which includes; EC tip cells, EC tubulogenesis, pericyte recruitment and proliferation, and basement membrane deposition. VEGF priming requires VEGFR2, and the effect of VEGFR2 is selective to the priming response and does not affect factor-dependent tubulogenesis in the absence of priming. Key molecule and signaling requirements for VEGF priming include RhoA, Rock1 (Rho-kinase), PKCα (protein kinase C α), and PKD2 (protein kinase D2). siRNA suppression or pharmacological blockade of these molecules and signaling pathways interfere with the ability of VEGF to act as an upstream primer of downstream factor-dependent EC tube formation as well as pericyte recruitment. VEGF priming was also associated with the formation of actin stress fibers, activation of focal adhesion components, upregulation of the EC factor receptors, c-Kit, IL-3Rα, and CXCR4 (C-X-C chemokine receptor type 4), and upregulation of EC-derived PDGF (platelet-derived growth factor)-BB, PDGF-DD, and HB-EGF (heparin-binding epidermal growth factor) which collectively affect pericyte recruitment and proliferation. Overall, this study defines a signaling signature for a separable upstream VEGF priming step, which can activate ECs to respond to downstream factors that are necessary to form branching tube networks with associated mural cells.

Size‐ and Temperature‐Dependent Suppression of Phonon Thermal Conductivity in Carbon Nanotube Thermoelectric Films

AbstractHeat transport in nanoscale carbon materials such as carbon nanotubes and graphene is normally dominated by phonons. Here, measurements of in‐plane thermal conductivity, electrical conductivity, and thermopower are presented from 77–350 K on two films with thickness <100 nm formed from semiconducting single‐walled carbon nanotubes. These measurements are made with silicon–nitride membrane thermal isolation platforms. The two films, formed from disordered networks of tubes with differing tube and bundle size, have very different thermal conductivity. One film matches a simple model of heat conduction assuming constant phonon velocity and mean free path, and 3D Debye heat capacity with a Debye temperature of 770 K. The second film shows a more complicated temperature dependence, with a dramatic drop in a relatively narrow window near 200 K where phonon contributions to thermal conductivity essentially vanish. This causes a corresponding large increase in thermoelectric figure‐of‐merit at the same temperature. A better understanding of this behavior can allow significant improvement in thermoelectric efficiency of these low‐cost earth‐abundant, organic electronic materials. Heat and charge conductivity near room temperature is also presented as a function of doping, which provides further information on the interaction of dopant molecules and phonon transport in disordered nanotube films.