In vivo, neutrophil motion is known to be propelled by concentration gradient of cytokine. However, the mechanism of propulsion has not been elucidated yet in the previous research. Based on the assumption that neutrophil is propelled by the concentration Marangoni effect, concentration gradient of cytokine on the neutrophil membrane and the neutrophil motion is investigated experimentally. In our previous investigations, it was found that neutrophil generate pseudopods for infiltration of organs near the wall. In this study, to investigate the phenomenon that neutrophil pseudopods generation near the wall, a microscopy-based observation experiment is conducted. The distance between the neutrophils and the wall and geometrical characteristics of the neutrophils are measured. From the results, the following three findings were obtained. First, arithmetic mean roughness and root mean square roughness are higher at distances of 2 and 4 μm from the wall surface. Second, skewness and kurtosis are highest value at distances of 2 μm from the wall surface. Third, neutrophil generates pseudopods at 4 μm from the wall surface and completely change shape at 2 μm. These findings suggest that near-wall interactions promote pseudopod-induced roughening that is likely to influence transport on the neutrophil membrane and, consequently, propulsion in cytokine gradients.
In the immune system, neutrophil movement toward the site of inflammation by concentration gradient is essential. In our previous studies, concentration gradient of cytokine on the neutrophil membrane is experimentally quantified. The results showed that the concentration gradient on the neutrophil membrane repeats positive and negative values while neutrophil moving. However, the key gap remains unclear: how external, membrane-scale cytokine gradient dynamics are coupled to intracellular signalling that drives protrusion and propulsion, and what the observed phase relationship implies for chemotaxis. In this study, the dynamics of intracellular calcium (Ca²⁺) in neutrophils were measured, and these findings were compared with previously measured cytokine concentration gradients to verify their correlation. The results show three main findings: (1) Neither IL-8 stimulation nor neutrophil viability produced a statistically significant change in the global intracellular Ca2+-indicator intensity or its decay rate. (2) The dominant frequencies of the membrane cytokine gradient and the intracellular Ca2+ gradient were similar, suggesting that external gradient dynamics and intracellular signaling are linked. (3) A consistent phase difference was observed between cytokine and Ca2+gradients, indicating a delayed intracellular response to changes in membrane cytokine gradients. These findings support a mechanistic role of calcium signaling in neutrophil propulsion and provide quantitative constraints for chemotaxis models.
One of the most important methods used to reduce manufacturing and maintenance costs for single-rotor wind turbines is to replace them with a multi-rotor turbine system, which captures the same amount of energy expended by the single turbine. The multi-rotor turbine system consists of several small turbines that reduce system loads and improve reliability. However, the use of this type of system faces many challenges, which many researchers and designers are working to overcome to reach an ideal design at the lowest cost in manufacturing, operation and maintenance with the best performance. This study presents the main reasons for using and developing multi-rotor wind turbines in terms of efficiency and cost, and the methods used by researchers and manufacturers to enhance the efficiency of this type of wind turbines. This review article will present an in-depth investigation of the power generating capabilities, cost concerns, and design characteristics of multi rotor wind turbines. By integrating current research and data on this revolutionary technology, this article hopes to add to the continuing conversation around sustainable energy alternatives and guide future developments in the field. Furthermore, multi-rotor turbines have faster wake recovery times, resulting in lower turbulence intensity in the wake than typical single-rotor turbines. Control of multi-rotor turbines is critical for reducing structural stress while increasing power output, necessitating advanced control algorithms and simulations. Noise prediction and control in multi-rotor systems provide additional issues, with rotor proximity influencing performance and noise production, demanding high-fidelity approaches for reliable predictions. Overall, while multi-rotor wind turbines improve performance, they also introduce complexity in design, control, and noise management that need careful analysis and innovative solutions.
Because of their potential to increase accessible area and overall heat diffusion, fins are often used as a thermal control approach for heat exchange. Nevertheless, these surfaces have undergone several modifications to improve their performance, one of which is perforation. Perforation shows outstanding promise in augmenting exchanged heat by enhancing turbulent stream and, most importantly, reducing the mass of these fins. The core goal of this review is to provide an extensive summarisation of the perforation impact as passive approaches that aim to enhance the thermo-hydraulic features of various fin forms that are employed in different applications, like heat sinks in electronics cooling, and heat exchangers in air-conditioning. Perforation in various fin shapes has been covered, such as (round, plate, longitudinal, pin, etc,) along with different parameters to investigate hole diameter, hole shape, hole quantity, hole distance, etc. Selected research was conducted under different conditions (forced and free convection, laminar and turbulent flow, and steady and unsteady). According to previous studies, drilled fins have a higher rate of heat than regular ones. The review concluded that freshly designed drilled fins outperform solid fins in enhancing the rate of heat transfer in a variety of thermal systems.
Refrigeration systems are integral to industries like food preservation, industrial processes, and air conditioning. As the demand for energy-efficient and environmentally friendly solutions grows, refrigeration lubricants have become crucial for improving system performance. However, selecting the right lubricant remains challenging due to the varying operating conditions in modern systems. This paper reviews the key properties of refrigeration lubricants, such as thermal stability, viscosity, chemical compatibility, and wear protection, which significantly influence system efficiency. The purpose of this study is to evaluate the effectiveness of both traditional and synthetic lubricants, particularly focusing on their compatibility with low-global-warming-potential (GWP) refrigerants and the impact of nanoparticles on lubricant performance. A comparative analysis of mineral oils and synthetic lubricants like polyol ester (POE), polyalkylene glycol (PAG), and polyvinyl ether (PVE) was conducted. Methods include a review of existing literature and performance data on lubricant-refrigerant compatibility, thermal stability tests, and the inclusion of nanoparticles to enhance lubricant properties. Results indicate that synthetic lubricants, which now account for over 50% of usage in refrigeration system, exhibit up to 30% better thermal stability and 25% improved chemical resistance compared to mineral oils. Nanoparticles, such as SiO2 and TiO2, were found to improve thermal conductivity by 10-15%, significantly enhancing system efficiency. The study concludes that selecting appropriate synthetic lubricants and incorporating nanoparticles can substantially improve the performance and sustainability of modern refrigeration systems.
