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Laser technologies for processing metals used as heat exchange surfaces are unrivaled to solve a number of problems in the energy industry. This is explained by the fact that after laser radiation treatment, metal surfaces gain unique surface functional properties (extreme wettability properties, high resistance to corrosion in contact with traditional coolants, high abrasive and cavitation resistance). The study of the processes of evaporation, boiling, and condensation on such surfaces is hampered by one of the unsolved problems, which is the lack of the ability to predict the configuration of microtextures, for example, in the form of micropillars and microchannels with predetermined sizes. In this work, a graphic–analytical technique based on the use of ablation spot sizes for the formation of a given configuration and microtexture dimensions on traditional structural materials of heat exchange surfaces is developed. Based on experimental data, regime maps were constructed for the formation of microtextures on the surfaces of aluminum alloy AlMg6 and steel AISI 310. The prospects for using metal surfaces with a given microtexture formed by laser radiation to intensify the phase transition of coolants and control convective flows in a droplet lying on a heated surface were assessed. The obtained results can be used in the development of spray (drip) irrigation systems to provide thermal protection for heat-stressed equipment. [ABSTRACT FROM AUTHOR]

The characteristics of water droplet heating and evaporation on structured hydrophobic and hydrophilic surfaces in the range of static contact angles from 73° to 155° were studied experimentally using high-speed video recording. Two fundamentally different technologies for applying coatings on a metal surface were used in comparison with the results on a polished surface. Microscopic studies were conducted to identify the features of the formed coatings. The wetting properties were characterized by means of the static contact angle and the contact angle hysteresis: on polished surface No. 1 (contact angle—73°, hysteresis—11°), on structured surface No. 2 (contact angle—125°, hysteresis—9°), and on structured surface No 3 (contact angle—155°, hysteresis—7°). The experimental dependences of the droplet evaporation rate on the different surfaces under normal conditions (ambient air temperature—293 K, atmospheric pressure, humidity—35%) were obtained. The evaporation regimes of droplets on the surfaces under study were identified. Water droplets evaporated in the pinning mode on surfaces No. 1 and No. 2. When a water droplet evaporated on surface No 3, the droplet was in the constant contact angle regime for ≈90% of its lifetime. Based on the experimental data obtained, a two-dimensional model of conjugate heat and mass transfer was developed, which describes the heating and evaporation of a liquid droplet on structured hydrophobic and hydrophilic surfaces at a wide range of contact angles. Satisfactory agreement was obtained between the numerical simulation results and experimental data. Using the model, the fields of temperature, concentration and other key characteristics were established at different points in time. Recommendations for its application in the development of gas–vapor–droplet applications were formulated. [ABSTRACT FROM AUTHOR]

In the framework of this work, the surface properties of Cu-SiC composite material were studied when spreading micro- and nanoliter liquids. The Cu-SiC samples with a SiC content of 5 to 20 wt.% were fabricated by spark plasma sintering at temperatures from 700 to 850 °C. The Cu-SiC surfaces were processed by two different methods: using abrasive materials and nanosecond laser radiation. Surface analysis was performed by scanning electron microscopy, profilometry, energy dispersive spectroscopy and Vickers methods. The surface properties (wetting and dynamic characteristics of spreading) were studied using a shadow optical technique when interacting the Cu-SiC surfaces with water (up to 10 μL). It was proved that the recorded deterioration of the wettability properties of Cu-SiC surfaces processed by abrasive materials with an increase in their sintering temperature and the reason for the spontaneous hydrophobization of the Cu-SiC composite materials modified by nanosecond laser radiation, are due to the adsorption of airborne hydrocarbon contaminants, similar to the known wetting inversion of metal surfaces. It was established that the wetting properties of materials prior to modification by laser radiation do not affect the intensity, duration of stages, and steady-state values of contact angles upon wetting inversion of Cu-SiC composite materials. It was also found that the processing of Cu-SiC surfaces by laser radiation makes it possible to change the dynamic characteristics of the liquid spreading (at a flow rate of 5 μL/min, the liquid front speed is more than three times, and the dynamic contact angles are in the range of 30°). [ABSTRACT FROM AUTHOR]

We formulated and experimentally proved a hypothesis on the causes of dispersion (puffing and microexplosion) of binary fuel droplets, including those in the composition of gel fuels. This hypothesis is based on the concepts of wetting thermodynamics and the theory of the two-component surface energy of substances and materials. An effective and reliable criterion was established that allowed the assessment of the possibility of the onset of puffing and microexplosion during the high-temperature heating of binary liquids. Microexplosions were found to occur only when isothermal conditions were necessarily reached at the liquid–liquid interface during the mixing of mutually insoluble components, provided that one component had to be polar, and the second had to be dispersive. In addition, it was necessary to provide external heating conditions under which the value of the surface free energy of the liquid–liquid interface formation tended to zero. [ABSTRACT FROM AUTHOR]

The main characteristics of ignition and combustion of fuel droplets (organic coal-water fuel, oil emulsion, and oil in the usual state) placed on the heated surfaces of structural steel (DIN standard grade X16CrNi25-20) were experimentally determined under conditions corresponding to the start-up and nominal operation of power-generating equipment. It was shown that due to the application of texture on the steel surfaces, it is possible to change the ignition and combustion characteristics of fuel droplets. A graphic-analytical method was developed to predict the dimensions of textures in the form of microchannels using laser technology for processing metal surfaces. It was found that the texture configuration in the form of microchannels formed by nanosecond laser radiation on steel surfaces makes it possible to significantly increase the surface resistance to adhesion of combustion products of liquid and slurry fuels. [ABSTRACT FROM AUTHOR]

We experimentally studied the influence of the texture of copper and steel surfaces on the possibility of controlling the phase transition of water droplets in the single-phase regime. The texture of metals was formed by polishing and grinding, which corresponded to the finishing treatment of heat transfer surfaces in cooling systems for energy-saturated equipment. The samples were studied by microscopy and profilometry. The texture was estimated by three-dimensional roughness parameters. It was found that, with a 2–2.5-fold increase in roughness, the wetting of copper deteriorates (the contact angle increases from 66° to 93°), whereas the wetting of steel improves (the contact angle decreases from 89° to 71°). It was experimentally proven that, among the two main factors that affect the spreading diameter (wetting and roughness), wetting is the most significant. A hypothesis was formulated regarding the reason for the increase in the contact angle of 7–10° and the drop in the decrease rate of the contact diameter during the transition from the pinning to the mixed stage of droplet evaporation. It was found that an increase in the surface area of 0.1% leads to an increase in the total droplet evaporation rate of 4–6.5%. [ABSTRACT FROM AUTHOR]

Exosomes are crucial players in cell-to-cell communication and are involved in tumorigenesis. There are two fractions of blood circulating exosomes: free and cell-surface-associated. Here, we compared the effect of total blood exosomes (contain plasma exosomes and blood cell-surface-associated exosomes) and plasma exosomes from breast cancer patients (BCPs, n = 43) and healthy females (HFs, n = 35) on crucial steps of tumor progression. Exosomes were isolated by ultrafiltration, followed by ultracentrifugation, and characterized by cryo-electron microscopy (cryo-EM), nanoparticle tracking analysis, and flow cytometry. Cryo-EM revealed a wider spectrum of exosome morphology with lipid bilayers and vesicular internal structures in the HF total blood in comparison with plasma. No differences in the morphology of both exosomes fractions were detected in BCP blood. The plasma exosomes and total blood exosomes of BCPs had different expression levels of tumor-associated miR-92a and miR-25-3p, induced angiogenesis and epithelial-to-mesenchymal transition (EMT), and increased the number of migrating pseudo-normal breast cells and the total migration path length of cancer cells. The multidirectional effects of HF total blood exosomes on tumor dissemination were revealed; they suppress the angiogenesis and total migration path length of MCF10A, but stimulate EMT and increase the number of migrating MCF10A and the total path length of SKBR3 cells. In addition, HF plasma exosomes enhance the metastasis-promoting properties of SKBR3 cells and stimulate angiogenesis. Both cell-free and blood cell-surface-associated exosomes are involved in the crucial stages of carcinogenesis: the initiation of EMT and the stimulation of proliferation, cell migration, and angiogenesis. Thus, for the estimation of the diagnostic/prognostic significance of circulating exosomes in the blood of cancer patients more correctly, the total blood exosomes, which consist of plasma exosomes and blood cell-surface-associated exosomes should be used. [ABSTRACT FROM AUTHOR]

Exosomes are important intercellular communication vehicles, secreted into body fluids by multiple cell types, including tumor cells. They contribute to the metastatic progression of tumor cells through paracrine signalling. It has been recently discovered that blood circulating exosomes contain distinguishable fractions of free and cell-surface-associated vesicles. We evaluated the influence of protein cargoes from exosomes from plasma, and exosomes from the total blood of healthy females (HFs) and breast cancer patients (BCPs), on cell motility. We conducted a mass spectrometric analysis of exosomal contents isolated from samples using ultrafiltration and ultracentrifugation approaches and verified their nature using transmission electron microscopy, nanoparticle tracking analysis and flow cytometry. We observed that malignant neoplasm-associated proteins in exosomes from BCP total blood were detected more often than in plasma (66% vs. 59%). FunRich analysis to assess Gene Ontology (GO) enrichment revealed that proteins with catalytic activities, transporter functions and protein metabolism activities were increased in exosomes from BCP blood. Finally, GO analysis revealed that proteomic profiles of exosomes from HF total blood were enriched with proteins inhibiting cell migration and invasion, which explains the low stimulating activity of exosomes from HF total blood on SKBR-3 cancer cell migration velocity. This allows exosomes to act as intermediaries providing intercellular communications through horizontal transfer of RNA and functionally active proteins, potentially affecting the development of both primary neoplasms and distant metastases. [ABSTRACT FROM AUTHOR]