APPLICATION OF LASER-INDUCED BREAKDOWN CAVITATION BUBBLES FOR CELL LYSIS IN VITRO

Objective: Understanding the basic mechanism of the cavitation bubble action on living cells as a crucial step of development and application ofsophisticated methods based on controlled cavitation in cell behaviour manipulation. Optimisation of parameters in order to expand cell lysis regioncreated by a single bubble.Methods: The cavitation bubbles are generated by the laser-induced breakdown method. The impact of controlled cavitation bubble on thebiological system is synchronously monitored under a microscope and recorded. Visualization of the cavitation bubble course is monitored by a highspeedcamera. The impact of technology on the healthy confluent cell layer is verified. Evaluation of the cavitation bubbles´ effect on cells in real timeand by subsequent analysis of the cell lysis region and impact of the cavitation bubble on cell viability is carried out by optical visualization and life/dead fluorescence staining.Results: Cavitation bubble induced in distance of 1.5 mm from the cell surface overcomes properties of sessile bubble and enables to create cell lysisregion over 1000 μm in diameter due to transient shear stress produced by liquid displaced by the bubble expansion.Conclusion: Cell lysis region is strongly dependent on the spot laser energy (SLE) and the bubble induction distance from cells. This knowledge iscrucial for application in chemical free cell lysis in vitro, wound induction for experimental purposes and cell layers patterning in desired scale

Research report GACČR nr. 17-19444S Interaction of heterogeneous liquid with flexible wall

Pulse flow was generated by a membrane pump. The nature of the pulsatile flow was measured with pressure sensors. We got information on the pressure development inside the circuit. Each phase of the pulse was evenly divided into 10 equal time slots. The individual slots were synchronized to the initial pressure change at 0.14Bar. The evaluation of the pressure measurement has already revealed the backward effect of the flexible wall. Especially when compared to glass rigid wall. Differences in pressures course are mostly significant in the peak width and lower stabilised pressure value. The flexible material absorbs part of pressure and expands its diameter. The liquid flow can be divided into four regimes: The first regime corresponds to pressure increase. The liquid flow is accelerated. The maximal fluid velocities reach 440 mm/s (Re 8800). The second regime is the highest point of pressure increase, where physically occurs the maximum membrane inclination, and closure of the pumps valves. At this point, the fluid stagnates, resulting in slowing down of the flow rate to 70 mm/s (Re 1400), and changing the characteristic velocity profile. This regime can be said as transient mode. The velocity profile is characterized with typical velocity decrease in the middle of cross section. This effect was found for both measurements – using rigid and flexible wall. The other phase of liquid acceleration can be observed in the third regime. Here, the liquid is fed with the pump. This acceleration last during the pressure decrease. This regime is characteristic with turbulent profile shape, and maximal flow velocity reach 260 mm/s (Re 5200). The fourth regime is observed since 6/5π period, when the pressure drop and starts to be stabilized. Here we can observe the liquid flow slowdown that is close to laminar profile shape. The maximal velocities in this regime are 35 mm/s (Re 700). There is an oscillation of a pressure, which leads to the formation of vortex structures near the wall. These structures are highlighted by the elasticity of the wall. The vortex structures were analysed using Proper Orthogonal Decomposition (POD). The most significant modes are for transient part of fluid flow and turbulent zone. The first 20 decomposition modes can be said as dominant. Here can be found vortex structures with kinetic energy of 10%. The nonstationary backward vortexes are developed close to the wall, as the fluid flow velocity is very small. The prevailing dominant effect on the fluid flow comes from the released kinetic energy from the relaxing flexible walls, especially in the fourth regime of pressure course. This effect is not significant for rigid walls. There were set an experimental setup for studying of cavitation base on Ventury tube. The fluid flow was analysed using high speed visualization methods in two interrogation areas in crosssection. The region of interest was focused on the swirling cavitation structure. The experiments run in 2018 were run in rigid wall. The fluid was also seeded with fluorescent particles for PIV measurement so the simple visualization was filled with fluid motion data’s. The investigated area was observed with synchronized two cameras recording parallel. The set of images were processed using supressing and dewarping algorithms. The experimental setup is prepared for the measurement on flexible wall and pulsatile flow

The interaction between fluid flow and ultra-hydrophobic surface in mini channel

Interaction of liquid with ultra-hydrophobic surface is accompanied by creation of layer of air. The effect of the air film has a potential of use in industry in many applications. The quality of the surface is influenced by matrix roughness, the character of physical or chemical cover. There was developed a method for analysis of the liquid flow and the air film using the lighting in volume, visualization with CCD camera and long distance microscope, and optical filters. There were prepared four stainless steel samples of inner channel of dimensions (80 × 8 × 8) mm and initial surface roughness Ra 0.33, Ra 1.0, Ra 2.0, and Ra 2.2. The inner channel was treated with plasma and commercial hydrophobic coating Greblon (WEILBURGER Coatings GmbH). There was realized study focused on the liquid flow velocity profile close to the air film. There are present results for laminar, transient and turbulent flows. The study also estimated the air film thickness depending on the Re number. The knowledge of the air film behaviour helps applied suitable degree of processing and cover for the target application

On the use of laser fragmentation for the synthesis of ligand-free ultra-small iron nanoparticles in various liquid environments

Traditionally, the synthesis of nanomaterials in the ultra-small size regime (1–3 nm diameter) has been linked with the employment of excessive amounts of hazardous chemicals, inevitably leading to significant environmentally detrimental effects. In the current work, we demonstrate the potential of laser fragmentation in liquids (LFL) to produce highly pure and stable iron ultra-small nanoparticles. This is carried out by reducing the size of carbonyl iron microparticles dispersed in various polar solvents (water, ethanol, ethylene glycol, polyethylene glycol 400) and liquid nitrogen. The explored method enables the fabrication of ligand-free iron oxide ultra-small nanoparticles with diameter in the 1–3 nm range, a tight size distribution, and excellent hydrodynamic stability (zeta potential > 50 mV). The generated particles can be found in different forms, including separated ultra-small NPs, ultra-small NPs forming agglomerates, and ultra-small NPs together with zero-valent iron, iron carbide, or iron oxide NPs embedded in matrices, depending on the employed solvent and their dipolar moment. The LFL technique, aside from avoiding chemical waste generation, does not require any additional chemical agent, other than the precursor microparticles immersed in the corresponding solvent. In contrast to their widely exploited chemically synthesized counterparts, the lack of additives and chemical residuals may be of fundamental interest in sectors requiring colloidal stability and the largest possible number of chemically active sites, making the presented pathway a promising alternative for the clean design of new-generation nanomaterials. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Internal Grant at the Institute for Nanomaterials, Advanced Technologies and Innovation of the Technical University of Liberec [8106]; Ministry of Education, Youth and Sports in the Czech Republic under the Research Infrastructures NanoEnviCz [LM2018124]; European Structural and Investment Funds [CZ.02.1.01/0.0/0.0/16_019/0000843]; project DKRVO by the Ministry of Education, Youth and Sports of the Czech Republic [RP/CPS/2020/006]; Visegrad International Scholarship Grant [52011086]Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: CZ.02.1.01/0.0/0.0/16_019/0000843, LM2018124, RP/CPS/2020/006; Technická Univerzita v Liberci: 810

Application of the Methodology of Communication Skills Training for Employees of Hotel Companies, Based on Immersion into the Virtual World

This paper describes a research study of communication skills training for future hotel workers in an immersive environment. The research team developed a model of the hotel reception in a virtual environment, and proposed a methodology for three-phase training. The research involved 56 testers who provided detailed feedback. To improve the communication skills of the participants, it is necessary to repeat the simulations and analyze the individual aspects of the communication in depth