Solvability of a moving contact-line problem with interface formation for an incompressible viscous fluid

We investigate the free-boundary problem of a steadily advancing meniscus in a circular capillary tube. The problem is described using the “interface formation model,” which was originally introduced with the aim of avoiding the singularities that arise when classical hydrodynamics is applied to problems with a moving contact line. We prove the existence of an axially symmetric solution in weighted Hölder spaces for low meniscus speeds.

Design and Automation of a vertical electrospinning system for manufacturing nanofibers

The objective of this research consists of the design, construction and automation of the electrospinning mechatronic system to obtain nanofibers. As a first stage, the structure of the electrospinning mechatronic system and the distribution, injection and manifold system were designed and built. In the second stage, the open-loop control system was outlined and implemented. It is made up of: control, isolation stage, and the plant. In the first element, the LabView interface and ATMega2560 microcontroller were used to manipulate the variables of the injection speed and distribution of the solution, the speed of the nanofiber collector and the height between the capillary tube and the collector, the magnitude of the temperature and humidity from the environment, also, the graphic interface was developed, the second element consists of isolating the control and power stage in addition to amplifying the command signals and enabling the correction elements, the third element receiving the signals from the power stage to perform the action and produce a change in the controlled variables in the process. With this prototype, it is intended to obtain nanofibers from different polymer solutions for use in the area of catalysis and biomaterials.

The Effect of Water Impact on the Refrigerant Pipeline between Compressor and Condensor on COP and Efficiency of Cooling Machine

The purpose of this research is (a) to design and assemble a steam compression cycle cooling machine using the main components on the market (b) to obtain the characteristics of the cooling engine, which includes the Coefficient of Performance (COP) and the efficiency of the cooling engine. The research was conducted experimentally in the laboratory. The refrigeration machine works by using a steam compression cycle, with the main components: a compressor, an evaporator, a capillary tube and a condenser. The compressor power is 1/6 PK, while the other main components are adjusted to the size of the compressor power. The refrigerant used is R134a. Variations of the research were carried out on the condition of the refrigerant pipe located between the compressor and condenser: (a) without being submerged in water (b) submerged in 0.50 liters of water and (c) submerged in 0.75 liters of water. The results of the study provide information that the water immersion in the refrigerant pipe which is located between the compressor and condenser affects the COP value and the efficiency of the refrigeration machine. Consecutively (1) without being submerged in water, the COP value is 2.45 and the efficiency is 0.64 (2) submerged in liter of water, the COP value is 2.41 and the efficiency is 0.62 (3) submerged in liter of water, the value COP is 2.34 and efficiency is 0.60.

Effect of nebulised BromAc® on rheology of artificial sputum: relevance to muco-obstructive respiratory diseases including COVID-19

Respiratory diseases such as cystic fibrosis, COPD, bronchiectasis asthma and COVID-19 are difficult to treat owing to viscous secretions in the airways that evade mucocilliary clearance. Since earlier studies have shown success with BromAc as mucolytic agent for treating a rare disease known as pseudomyxoma peritonei (PMP), we tested the formulation on two gelatinous airway representative sputa models, in order to determine whether similar efficacy exist. The sputum (1.5 ml) lodged in an endotracheal tube was treated to aerosolised N-acetylcysteine, bromelain, or their combination (BromAc) using a nebuliser with 6.0 ml of the agents in phosphate buffer saline, over 25 min. Controls received phosphate buffer saline. The dynamic viscosity was measured before and after treatment using a capillary tube method, whilst the sputum flow (ml/sec) was assessed using a 0.5 ml pipette. Finally, the sequestered agents (concentration) in the sputa after treatment were quantified using standard bromelain and N-acetylcysteine chromogenic assays. Results indicated that bromelain and N-acetylcysteine affected both the dynamic viscosities and pipette flow in the two sputa models, with changes in the former parameter having immense effect on the latter. BromAc showed a greater rheological effect on both the sputa models compared to individual agents. Further, correlation was found between the rheological effects and the concentration of agents in the sputa. Hence, this study indicates that BromAc may be used as a successful mucolytic for clearing airway congestion caused by thick mucinous immobile secretion, however further studies with patient sputum samples using aerosol BromAc is warranted.

Confined self-propulsion of an isotropic active colloid

To spontaneously break their intrinsic symmetry and self-propel at the micron scale, isotropic active colloidal particles and droplets exploit the nonlinear convective transport of chemical solutes emitted/consumed at their surface by the surface-driven fluid flows generated by these solutes. Significant progress was recently made to understand the onset of self-propulsion and nonlinear dynamics. Yet, most models ignore a fundamental experimental feature, namely the spatial confinement of the colloid, and its effect on propulsion. In this work the self-propulsion of an isotropic colloid inside a capillary tube is investigated numerically. A flexible computational framework is proposed based on a finite-volume approach on adaptative octree grids and embedded boundary methods. This method is able to account for complex geometric confinement, the nonlinear coupling of chemical transport and flow fields, and the precise resolution of the surface boundary conditions, that drive the system's dynamics. Somewhat counterintuitively, spatial confinement promotes the colloid's spontaneous motion by reducing the minimum advection-to-diffusion ratio or Péclet number, ${Pe}$ , required to self-propel; furthermore, self-propulsion velocities are significantly modified as the colloid-to-capillary size ratio $\kappa$ is increased, reaching a maximum at fixed ${Pe}$ for an optimal confinement $0<\kappa <1$ . These properties stem from a fundamental change in the dominant chemical transport mechanism with respect to the unbounded problem: with diffusion now restricted in most directions by the confining walls, the excess solute is predominantly convected away downstream from the colloid, enhancing front-back concentration contrasts. These results are confirmed quantitatively using conservation arguments and lubrication analysis of the tightly confined limit, $\kappa \rightarrow 1$ .

On the slow ionization waves forming the breakdown in a long capillary tube with helium at low pressure

The results of studies of an electrical breakdown leading to the glow discharge ignition in a long capillary quartz tube are presented. Under such conditions, the breakdown completion is preceded by the development of direct, backward, and counter slow ionization waves traveling in the tube. The initiation of the waves was created in helium at low pressure (P=10 Torr) by the high-voltage pulses of positive and negative polarity with amplitude of several kilovolts. In the beginning, the regime without the breakdown completion in the tube was studied. In this regime, the propagation of only direct positive and direct negative ionization waves happens. The research on dynamics of the direct, backward, and counter positive and negative waves followed by a complete breakdown was done as well. The influence of the pre-existing plasma on the ionization waves propagation was also studied. The plasma was created in advance by low-current glow discharge being formed in the tube. The instant images of ionization waves were correlated with the electrical currents formed by the waves, that is, with the displacement current through the dielectric wall and the conductive current through the plasma column. In the experiments, the fine-sectioned electrode wrapped around the lateral tube surface was used. The usage of such electrode allowed one to study the dynamics of the surface charge deposition and deletion happening during the direct and backward wave propagation, respectively. Finally, a strong difference in the spatial structure and velocity of positive and negative direct waves traveling through non-ionized gas was revealed. Contrary, both the positive and negative backward waves traveling through the plasma formed by previous direct waves have the parameters close to each other.

Qingre Huoxue Decoction, A Traditional Chinese Herbal Formulation, Impacts Angiogenesis in Psoriasis-Like Skin Through the HIF-1α/Flt-1/VEGF Pathway

Background: Qingre Huoxue Decoction (QHD), a traditional Chinese medicine (TCM) formulation, could alleviate psoriasis in our previous studies. The present work aimed to assess QHD’s effects on psoriasis and the underpinning mechanism in cultured cells and experimental animals.Methods: The CCK-8 assay was carried out for cell viability assessment. HUVEC migration was assessed by transwell and wound healing assays. QHD-induced suppression of capillary tube formation in HUVECs was detected by tube formation assay. In addition, the imiquimod (IMQ)-induced male BALB/c mouse model of psoriasis was established to examine the Psoriasis Area and Severity Index (PASI) after QHD administration. HIF-1α, Flt-1 and VEGF expression levels in vivo were assessed by immunoblot, qPCR and immunofluorescence. Results: The results showed that QHD dose-dependently reduced viability in HUVECs. In addition, QHD suppressed tube formation in HUVECs at levels below those needed to inhibit HUVECs. Upon QHD administration, HUVEC migration was markedly decreased; QHD effectively prevented the migratory ability of HUVECs, as determined by wound areas at 0h, 12h and 24h, respectively. Finally, QHD starkly downregulated HIF-1α, Flt-1 and VEGF in the IMQ-induced mouse model, at the protein and mRNA levels.Conclusions: In summary, QHD inhibits angiogenesis in cultured cells and mice. HIF-1α/Flt-1/VEGF signaling is important in angiogenesis and psoriasis development. These findings provide a rationale for developing QHD for clinical use against psoriasis.