This study explores the innovative approach in the development of freeze-dried hydrogel films, leveraging the unique properties of gum Karaya (GK), poly-(vinyl alcohol) (PVA), poly-(ethylene glycol) (PEG), and glycerol with a coating of octenidine dihydrochloride (OCT). These innovative hydrogel films exhibit at a certain glycerol concentration a sandwich-like structure, achieved through a tailored freeze-drying process, which enhances transparency and mechanical stability. OCT provides superior antibacterial performance, effectively combating multidrug-resistant bacteria with a controlled and gradual release mechanism, surpassing conventional OCT solutions that require frequent reapplication for infected wound treatment without the creation of bacterial resistance. Advanced environmental scanning electron microscopy (A-ESEM) reveals the complex microstructure of the hydrogel, highlighting the dense surface layer and interconnected porous bulk. Variations in glycerol concentrations proved to significantly impact hydrogels' properties. Increasing the glycerol concentration decreases the pore size (around 4.5 μm) while enhancing the polymer network density and flexibility. However, low concentration increases the pore size (7.8-15.6 μm), impacting enhanced swelling behavior and hydrolytic stability. OCT's rapid antibacterial action, releasing over 30% within the first hour and maintaining prolonged activity for up to 2 weeks, emphasizes the material's potential for diverse applications. Hydrogels' remarkable transparency, porosity, structural stability, and antibacterial efficacy against both Gram-positive and Gram-negative strains suggest promising uses as transparent dressings, biomedical devices, and infection-resistant surfaces.

• Publikační typ
• časopisecké články MeSH

This study investigates supersonic flow within a nozzle under low-pressure conditions at the continuum mechanics boundary. This phenomenon is commonly encountered in applications such as the differentially pumped chamber of an Environmental Scanning Electron Microscope (ESEM), which employs an aperture to separate two regions with a great pressure gradient. The nozzle geometry and flow control in this region can significantly influence the scattering and loss of the primary electron beam traversing the differentially pumped chamber and aperture. To this end, an experimental chamber was designed to explore aspects of this low-pressure regime, characterized by a varying ratio of inertial to viscous forces. The initial experimental results obtained using pressure sensors from the fabricated experimental chamber were utilized to refine the Ansys Fluent simulation setup, and in this combined approach, initial analyses of supersonic flow and shock waves in low-pressure environments were conducted. The refined Ansys Fluent system demonstrated a very good correspondence with the experimental findings. Subsequently, an analysis of the influence of surface roughness on the resulting flow behavior in low-pressure conditions was performed on this refined model using the refined CFD model. Based on the obtained results, a comparison of the influence of nozzle roughness on the resulting electron beam scattering was conducted for selected low-pressure variants relevant to the operational conditions of the Environmental Scanning Electron Microscope (ESEM). The influence of roughness at elevated working pressures within the ESEM operating regime on reduced electron beam scattering has been demonstrated. At lower pressure values within the ESEM operating regime, this influence is significantly diminished.

• Klíčová slova
• Ansys Fluent, CFD, ESEM, aperture, differentially pumped chamber, low pressure, nozzle, roughness, shock wave,
• Publikační typ
• časopisecké články MeSH

The article describes the combination of experimental measurements with mathematical-physics analyses in flow investigation in the chambers of the scintillator detector, which is a part of the environmental scanning electron microscope. The chambers are divided with apertures by small openings that keep the desirable pressure differences between three chambers: The specimen chamber, the differentially pumped intermediate chamber, and the scintillator chamber. There are conflicting demands on these apertures. On the one hand, the diameter of the apertures must be as big as possible so that they incur minimal losses of the passing secondary electrons. On the other hand, it is possible to magnify the apertures only to a certain extent so the rotary and turbomolecular vacuum pump can maintain the required operating pressures in separate chambers. The article describes the combination of experimental measurement using an absolute pressure sensor and mathematical physics analysis to map all the specifics of the emerging critical supersonic flow in apertures between the chambers. Based on the experiments and their tuned analyses, the most effective variant of combining the sizes of each aperture concerning different operating pressures in the detector is determined. The situation is made more difficult by the described fact that each aperture separates a different pressure gradient, so the gas flow through each aperture has its own characteristics with a different type of critical flow, and they influence each other, thereby influencing the final passage of secondary electrons detected by the scintillator and thus affecting the resulting displayed image.

• Klíčová slova
• Ansys Fluent, ESEM, aperture, critical flow, one-dimensional flow theory, pressure sensor, scintillation detector,
• Publikační typ
• časopisecké články MeSH

This paper describes the combination of experimental measurements with mathematical-physical analysis during the investigation of flow in an aperture at low pressures in a prepared experimental chamber. In the first step, experimental measurements of the pressure in the specimen chamber and at its outlet were taken during the pumping of the chamber. This process converted the atmospheric pressure into the operating pressure typical for the current AQUASEM II environmental electron microscope at the ISI of the CAS in Brno. Based on these results, a mathematical-physical model was tuned in the Ansys Fluent system and subsequently used for mathematical-physical analysis in a slip flow regime on a nozzle wall at low pressure. These analyses will be used to fine-tune the experimental chamber. Once the chamber is operational, it will be possible to compare the results obtained from the experimental measurements of the nozzle wall pressure, static pressure, total pressure and temperature from the nozzle axis region in supersonic flow with the results obtained from the mathematical-physical analyses. Based on the above comparative analyses, we will be able to determine the realistic slip flow at the nozzle wall under different conditions at the continuum mechanics boundary.

• Klíčová slova
• Ansys Fluent, low pressure, nozzle, shear stress, slip flow,
• Publikační typ
• časopisecké články MeSH

The Extended Low Temperature Method (ELTM) for the in-situ preparation of plant samples in an environmental scanning electron microscope enables carrying out repetitive topographical and material analysis at a higher resolution in the vacuum conditions of a scanning electron microscope or in the low gas pressure conditions of an environmental scanning electron microscope. The method does not require any chemical intervention and is thus suitable for imaging delicate structures rarely observable with common treatment methods. The method enables both sample stabilization as close to their native state as possible, as well as the transfer of the same sample from a low vacuum to an atmospheric condition for sample storage or later study. It is impossible for wet samples in the environmental scanning electron microscope. Our studies illustrate the high applicability of the ELTM for different types of plant tissue, from imaging of plant waxes at higher resolution, the morphological study of highly susceptible early somatic embryos to the elemental microanalysis of root cells. The method established here provides a very fast, universal and inexpensive solution for plant sample treatment usable in a commercial environmental scanning electron microscope equipped with a cooling Peltier stage.

• MeSH
• mikroanalýza elektronovou sondou metody   MeSH
• mikroskopie elektronová rastrovací metody   MeSH
• rostliny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Somatic embryogenesis (SE) is an important biotechnological technique used for the propagation of many pine species in vitro. However, in bog pine, one of the most endangered tree species in the Czech Republic, limitations were observed, which negatively influenced the development and further germination of somatic embryos. Although initiation frequency was very low-0.95 %, all obtained cell lines were subjected to maturation. The best responding cell line (BC1) was used and subjected to six different variants of the maturation media. The media on which the highest number of early-precotyledonary/cotyledonary somatic embryos was formed was supplemented with 121 μM abscisic acid (ABA) and with 6 % maltose. In the end of maturation experiments, different abnormalities in formation of somatic embryos were observed. For visualization and identification of abnormalities in meristem development during proliferation and maturation processes, the environmental scanning electron microscope was used. In comparison to the classical light microscope, the non-commercial environmental scanning electron microscope AQUASEM II has been found as a very useful tool for the quick recognition of apical meristem disruption and abnormal development. To our knowledge, this is the first report discussing somatic embryogenesis in bog pine. Based on this observation, the cultivation procedure could be enhanced and the method for SE of bog pine optimized.

• Klíčová slova
• Abnormalities, Environmental scanning electron microscope, Pinus uncinata subsp. uliginosa, Somatic embryogenesis,
• MeSH
• borovice růst a vývoj   ultrastruktura   MeSH
• klíčení MeSH
• mikroskopie elektronová rastrovací MeSH
• mokřady MeSH
• semena rostlinná růst a vývoj   ultrastruktura   MeSH
• somatická embryogeneze rostlin MeSH
• Publikační typ
• časopisecké články MeSH