Effectiveness of UV-C radiation in inactivation of microorganisms on materials with different surface structures.

INTRODUCTION AND OBJECTIVE: Ultraviolet light in the UV-C band is known as germicidal radiation and was widely used for both sterilization of the equipment and creation of a sterile environment. The aim of the study is to assess the effectiveness of inactivation of microorganisms deposited on surfaces with various textures by UV-C radiation disinfection devices. MATERIAL AND METHODS: Five microorganisms (3 bacteria, virus, and fungus) deposited on metal, plastic, and glass surfaces with smooth and rough textures were irradiated with UV-C light emitted by low-pressure mercury lamp and ultraviolet emitting diodes (LEDs), from a distance of 0.5 m, 1 m, and 1.5 m to check their survivability after 20-minute exposure. RESULTS AND CONCLUSIONS: Both tested UV-C sources were effective in inactivation of microorganisms; however, LED emitter was more efficient in this respect than the mercury lamp. The survival rate of microorganisms depended on the UV-C dose, conditioned by the distance from UV-C source being the highest at 0.5 m and the lowest at 1.5 m. For the tested microorganisms, the highest survival rate after UV-C irradiation was usually visible on glass and plastic surfaces. This observation should be considered in all environments where the type of material (from which the elements of technical equipment are manufactured and may be contaminated by specific activities) is important for maintaining the proper level of hygiene and avoiding the unwanted and uncontrolled spread of microbiological pollution.

Impact of the Carbon Nanofillers Addition on Rheology and Absorption Ability of Composite Shear Thickening Fluids.

Synthesis and characterization of composite shear thickening fluids (STFs) containing carbon nanofillers are presented. Shear thickening fluids have attracted particular scientific and technological interest due to their unique ability to abruptly increase viscosity in the case of a sudden impact. The fluids have been developed as a potential component of products with high energy absorbing efficiency. This study reports on the rheological behavior, stability, and microstructure of the STFs modified with the following carbon nanofillers: multi-walled carbon nanotubes, reduced graphene oxide, graphene oxide, and carbon black. In the current experiment, the basic STF was made as a suspension of silica particles with a diameter of 500 nm in polypropylene glycol and with a molar mass of 2000 g/mol. The STF was modified with carbon nanofillers in the following proportions: 0.05, 0.15, and 0.25 vol.%. The addition of the carbon nanofillers modified the rheological behavior and impact absorption ability; for the STF containing 0.25 vol.% of carbon nanotubes, an increase of force absorption up to 12% was observed.

Visualization of the internal structure of Didymosphenia geminata frustules using nano X-ray tomography.

For the first time, the three-dimensional (3D) internal structure of naturally produced Didymosphenia geminata frustules were nondestructively visualized at sub-100 nm resolution. The well-optimized hierarchical structures of these natural organisms provide insight that is needed to design novel, environmentally friendly functional materials. Diatoms, which are widely distributed in freshwater, seawater and wet soils, are well known for their intricate, siliceous cell walls called 'frustules'. Each type of diatom has a specific morphology with various pores, ribs, minute spines, marginal ridges and elevations. In this paper, the visualization is performed using nondestructive nano X-ray computed tomography (nano-XCT). Arbitrary cross-sections through the frustules, which can be extracted from the nano-XCT 3D data set for each direction, are validated via the destructive focused ion beam (FIB) cross-sectioning of regions of interest (ROIs) and subsequent observation by scanning electron microscopy (SEM). These 3D data are essential for understanding the functionality and potential applications of diatom cells.