Hemodynamic Principles in Free Tissue Transfer: Vascular Changes at the Anastomosis Site

Purpose: Various factors such as blood velocity, turbulent flow,and intimal injury are the most basic elements in free tissue transfers. However, how blood flow is reestablished, maintained, and changed after vascular anastomosis has rarely been studied.Methods: A 54-year-old male sustained an unreplantable severe crushing injury to his right hand. The middle finger was transferred to the thumb as an ectopic replantation using an anastomosis between the radial and digital arteries. However, secondary reconstruction for the first web space defect was inevitable and an anteromedial thigh free flap procedure was performed 2 months later using the previously anastomosed vessels. During the procedures, we noted morphologic changes in the microvessels and tried to explain those phenomena by applying the principles of hemodynamics.Results: Due to the discrepancy in vascular size between the radial and digital arteries, the velocity of the blood flow in the post-anastomotic site, which was the digital artery, must have been increased by Poiseuille’s law. Supposing that the velocity through the post-anastomotic site of the digital artery was increased, the pressure exerted by that flow decreased, resulting in more shrinkage of the vessel lumen of the digital artery by Bernoulli’s principle. Pascal’s law could also be applied in confined spaces with a static flow; where there is a constant pressure, as the radius of the post-anastomotic digital artery diminishes, the tension within the digital artery’s wall also simultaneously decreases. By Laplace’s law, the post-anastomotic digital artery’s wall thickens as less tension is exerted on the wall.Conclusion: Understanding these simple flow mechanics will enable microsurgeons to better avoid the risk factors causing thrombosis, which is related to flap failure.

Selecting a Product for Wax Remediation: From Characterization of Field Wax Deposits to Improvement of Treatment Sustainability

Wax deposition is one of the known challenges of flow assurance management in upstream oil production and operations demanding continuous improvements and the search for more effective prevention and remediation methods. At the same time, there are no universally agreed upon test methods to evaluate the efficiency and mechanisms related to the chemical treatments. The objective of this paper is to present and debate different methods to evaluate the effectiveness of batch treatments for remediation of wax deposits and compare commonly applied solvents with fluids containing biosurfactants. One of the presented methods is a new test methodology that simulates dynamic and quasi-static flow regimes in production tubing and pipelines, as benchmarked methods, showed that the chemical treatments with biosurfactants, besides being a greener, sustainable option, were more efficient at dispersing wax deposits than the traditional solvent treatments.

Difference between SFMR and SITMR 1 compensation for hydrostatic thrust bearing

Both flat and island type membranes are used in single-action membrane restrictors. But the difference between the single-action flat membrane restrictor (SFMR) and the single-action island type membrane restrictor (SITMR) has rarely been reported in the literature. In this study, we first compared the static and dynamic characteristics of SFMR and SITMR, and found that there is a little difference between them when the difference between supply pressure ps and outlet pressure pr is not large. Then, we investigated the dynamic characteristics of hydrostatic thrust bearings using both SFMR and SITMR compensation, and found SITMR having a better dynamic bearing performance. The reason for this phenomenon is that the mass of the membrane in SITMR is smaller than that of the membrane in SFMR. When the difference between supply pressure ps and outlet pressure pr becomes large, SFMR reduces the static flow rate of the lubricant of bearing systems more significantly than SITMR.

Stabilization of Sand with Colloidal Nano-Silica Hydrosols

Colloidal nano-silica (NS) hydrosols are electrochemically stabilized, polymerized amorphous silica in low viscosity solutions, and in the form of hydrated gels, silica globules or pellicles. Compared to applications in concrete technology, the use of silica-based binders for groundwork applications has received little attention. Silica-based hydrosols impose no known direct risks to humans and are generally courteous to the soil health and ecosystem service functions. Their localized impact on microorganisms however needs to be further investigated. To this end, NS hydrosols have a scope for use as an alternative low-viscose material in groundworks. The current understanding of interactions between NS hydrosols and soil (sand) is, however, confused by the limited availability of experimental evidence concerning undrained static flow and large strain behavior. The contributions, presented in this paper, advance the knowledge through experimental testing, molecular modelling, and micro-analytical measurements. Four grades of colloidal NS (1–15 wt.%) were synthesized for grouting medium-dense sub-angular fine siliceous sand specimens. Consolidated-undrained triaxial compression testing was performed on the base and treated sand for isotropic consolidation over the effective stress range 100–400 kPa. Overall, silica impregnation produced improvements in yield and residual undrained shear strengths, restricted unwelcomed impacts of excess pore water pressure, and led to the formation of generally more dilative, strain-hardening behavior. Steady states and static flow potential indices are also studied as functions of confinement level and viscosity of the NS grout.

Method and System for Testing the Working Characteristics of Vehicle Fuel Injector

Background: The vehicle fuel injector directly affects the power performance, emission characteristics and economic efficiency of the engine. At present, several testing standards are stipulated on accurate measurement of the working characteristics of fuel injectors. Objective: The purpose of this study is to provide an efficient patent about the method and system for testing the working characteristics of vehicle fuel injector. Methods: Two key techniques are significant to establish the standard test environment. The patent about the pressure control approach and injector driving method was proposed. The adaptive fuzzy PID approach is applied in pressure control. An adaptive multi-functional driver was designed and developed for both the voltage-driven and current-driven port fuel injectors. Results: The experiments on the two key technologies were operated. During the dynamic flow test, the settling time using the system was 1ms. For the static flow test, the settling time was 1 s. The maximum changing rate of the pressure fluctuation was 1%. Then the system was verified by test on the flow characteristics and dynamic response of the voltagedriven and current-driven injectors. The linear deviation of each dynamic flow curve is between ± 3% to ± 6%. Furthermore, the deviation of the dynamic flow curves from the repeated test is small. The maximum deviation of the static flow results is less than 4%. And the dynamic response of the injector varies with the change of the pressure. Conclusion: The system meets the requirements of the related standards. The experimental results prove that the system is stable and reliable.

Quasi-static Flow Model for Predicting the Extreme Values of Air Pocket Pressure in Draining and Filling Operations in Single Water Installations

Inertial models have been used by researchers to simulate the draining and filling processes in water pipelines, based on the evolution of the main hydraulic and thermodynamic variables. These models use complex differential equations, which are solved using advanced numerical codes. In this study, a quasi-static flow model is developed to study these operations in hydraulic installations. The quasi-static flow model represents a simplified formulation compared with inertial flow models, in which its numerical resolution is easier because only algebraic equations must be addressed. Experimental measurements of air pocket pressure patterns were conducted in a 4.36 m long single pipeline with an internal diameter of 42 mm. Comparisons between measured and computed air pocket pressure oscillations indicate how the quasi-static flow model can predict extreme values of air pocket pressure for experimental runs, demonstrating the possibility of selecting stiffness and pipe classes in actual pipelines using this model. Two case studies were analysed to determine the behaviour of the quasi-static flow model in large water pipelines.

Mechanism Underlying Flow Velocity and Its Corresponding Influence on the Growth of Euglena gracilis, a Dominant Bloom Species in Reservoirs

The effects of hydrodynamics on algae growth have received considerable attention, and flow velocity is one of the most frequently discussed factors. For Euglena gracilis, which aggregates resources and is highly resistant to environmental changes, the mechanism underlying the impact of flow velocity on its growth is poorly understood. Experiments were conducted to examine the response of algae growth to different velocities, and several enzymes were tested to determine their physiological mechanisms. Significant differences in the growth of E. gracilis were found at different flow velocities, and this phenomenon is unique compared to the growth of other algal species. With increasing flow velocity and time, the growth of E. gracilis is gradually inhibited. In particular, we found that the pioneer enzyme is peroxidase (POD) and that the main antioxidant enzyme is catalase (CAT) when E. gracilis experiences flow velocity stress. Hysteresis between total phosphorus (TP) consumption and alkaline phosphatase (AKP) synthesis was observed. Under experimental control conditions, the results indicate that flow velocities above 0.1 m/s may inhibit growth and that E. gracilis prefers a relatively slow or even static flow velocity, and this finding could be beneficial for the control of E. gracilis blooms.