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Biofilms, mainly comprised of bacteria, form on materials' surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials that make up drains, and slippage. Inside of a biofilm is an environment conducive to the growth and propagation of bacteria. Problems with biofilms include the inability of disinfectants and antibiotics to act on them. Therefore, we have investigated the potential application of alternating electromagnetic fields for biofilm control. We obtained exciting results using various materials' specimens and frequency conditions. Through these studies, we gradually understood that the combination of the type of bacteria, the kind of material, and the application of an electromagnetic field with various low frequencies (4 kHz–12 kHz) changes the circumstances of the onset of the biofilm suppression effect. In this study, relatively high frequencies (20 and 30 kHz) were applied to biofilms caused by Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), and quantitative evaluation was performed using staining methods. The sample surfaces were analyzed by Raman spectroscopy using a Laser Raman spectrometer to confirm the presence of biofilms on the surface. [ABSTRACT FROM AUTHOR]

Steelmaking slags are prospective base materials for seaweed beds, resulting from a continuous process of biofouling, starting from biofilm formation and leading to growing algae. While focusing on biofilm formation, we investigated specific features of steelmaking slags when utilized as a base for seaweed beds by comparing the bacterial communities in marine biofilms between steelmaking slags and artificially produced ones. Genomic DNA was extracted from the biofilms collected on days 3 and 7, and partial 16S rRNA libraries were generated and sequenced by second-generation next-generation sequencing. The read sequences were analyzed using QIIME 2™, then heatmaps and non-metric multidimensional scaling based on the Bray–Curtis dissimilarity index in the R program. Rhodobacteraceae and Flavobacteriaceae were the most dominant family members in all samples on both days 3 and 7. However, Mariprofundus, comprising iron-oxidative bacteria, was predominantly detected in the samples of steelmaking slags on day 7. This suggested that the growth of Mariprofundus was dependent on Fe(II) ion concentration and that steelmaking slags eluted Fe(II) ions more easily than artificial slags. In contrast, Sulfurovaceae, sulfur-oxidizing bacteria, were dominantly present in all samples on day 3, but decreased by day 7, regardless of the sulfur content. It was supposed that engine oil-derived sulfur compounds strongly influenced Sulfurovaceae growth, whereas slag-derived sulfur compounds did not. Heatmap analysis indicated that the submersion period significantly influenced the bacterial communities, regardless of the differences in the main slag content ratios. Summarizing these results, the elution characteristics of steelmaking slags have the potential to influence the formation of marine biofilms, and this formation is significantly influenced by environmental conditions. [ABSTRACT FROM AUTHOR]

The precise observation of a solid–liquid interface by means of frequency modulation atomic force microscopy (FM-AFM) was performed, demonstrating its applicability to a study on lead acid batteries using an electrochemical test cell for in-liquid FM-AFM embedded with a specialized cantilever holder. The consistency and reproducibility of each surface profile observed via amplitude modulation AFM and FM-AFM were verified properly in a strong acidic electrolyte. In terms of FM-AFM, the ability to observe remarkable changes in the force mapping is the most beneficial, especially near the negative electrode surface. The localization of lignosulfonate (LS) added into the electrolyte as an expander could be visualized since this characteristic force mapping was captured when LS was added to electrolyte. [ABSTRACT FROM AUTHOR]

Biofilms have caused many problems, not only in the industrial fields, but also in our daily lives. Therefore, it is important for us to control them by evaluating them properly. There are many instrumental analytical methods available for evaluating formed biofilm qualitatively. These methods include the use of Raman spectroscopy and various microscopes (optical microscopes, confocal laser microscopes, scanning electron microscopes, transmission electron microscopes, atomic force microscopes, etc.). On the other hand, there are some biological methods, such as staining, gene analyses, etc. From the practical viewpoint, staining methods seem to be the best due to various reasons. Therefore, we focused on the staining method that used a crystal violet solution. In the previous study, we devised an evaluation process for biofilms using a color meter to analyze the various staining situations. However, this method was complicated and expensive for practical engineers. For this experiment, we investigated the process of using regular photos that were quantified without any instruments except for digitized cameras. Digitized cameras were used to compare the results. As a result, we confirmed that the absolute values were different for both cases, respectively. However, the tendency of changes was the same. Therefore, we plan to utilize the changes before and after biofilm formation as indicators for the future. [ABSTRACT FROM AUTHOR]

The evaluation of biofilm formation is important, given the ubiquity and problematic nature of biofilms in industrial and medical settings, as well as in everyday life. Basically, biofilms are formed on substrates. Therefore, it is essential to consider the properties of the substrates during biofilm evaluation. The common dye staining method to evaluate biofilm formation requires a short evaluation time and enables the evaluation of a large area of the sample. Furthermore, it can be easily determined visually, and quantitative evaluation is possible by quantifying color adsorption. Meanwhile, the dye staining method has the problem of adsorption even on substrate surfaces where no biofilm has formed. Therefore, in this study, we focused on Ag+ reduction reaction to devise a novel biofilm evaluation method. Ag+ is highly reductive and selectively reacts with organic substances, such as saccharides, aldehydes, and proteins contained in biofilms, depositing as metallic Ag. First, to simply evaluate biofilm formation, we used a glass substrate as a smooth, transparent, and versatile oxide material. We observed that the amount of Ag deposited on the substrate was increased proportionally to the amount of biofilm formed under light irradiation. Upon comparing the Ag deposition behavior and adsorption behavior of crystal violet, we discovered that for short immersion times in AgNO3 solution, Ag deposition was insufficient to evaluate the amount of biofilm formation. This result suggests that the Ag reduction reaction is more insensitive than the crystal violet adsorption behavior. The results of the Ag deposition reaction for 24 h showed a similar trend to the crystal violet dye adsorption behavior. However, quantitative biofilm evaluation using the proposed method was difficult because of the Ag+ exchange with the alkali metal ions contained in the glass substrate. We addressed this issue by using the basic solution obtained by adding an ammonia solution to aqueous AgNO3. This can cause Ag+ to selectively react with the biofilm, thus enabling a more accurate quantitative evaluation. The optimum was determined at a ratio of distilled water to aqueous ammonia solution of 97:3 by weight. This biofilm was also evaluated for materials other than ceramics (glass substrate): organic material (polyethylene) and metal material (pure iron). In the case of polyethylene, a suitable response and evaluation of biofilm formation was successfully achieved using this method. Meanwhile, in the case of pure iron, a significantly large lumpy deposit of Ag was observed. The likely reason is that Ag precipitation occurred along with the elution of iron ions because of the difference in ionization tendency. It could be concluded that the detection of biofilm formation using this method was effective to evaluate biofilm formation on materials, in which the reduction reaction of [Ag(NH3)2]+ does not occur. Thus, a simple and relatively quantitative evaluation of biofilms formed on substrates is possible using this method. [ABSTRACT FROM AUTHOR]

Biofilms are a result of bacterial activities and are found everywhere. They often form on metal surfaces and on the surfaces of polymeric compounds. Biofilms are sticky and mostly consist of water. They have a strong resistance to antimicrobial agents and can cause serious problems for modern medicine and industry. Biofilms are composed of extracellular polymeric substances (EPS) such as polysaccharides produced from bacterial cells and are dominated by water at the initial stage. In a series of experiments, using Escherichia coli, we developed three types of laboratory biofilm reactors (LBR) to simulate biofilm formation. For the first trial, we used a rotary type of biofilm reactor for stirring. For the next trial, we tried another rotary type of reactor where the circular plate holding specimens was rotated. Finally, a circular laboratory biofilm reactor was used. Biofilms were evaluated by using a crystal violet staining method and by using Raman spectroscopy. Additionally, they were compared to each other from the practical (industrial) viewpoints. The third type was the best to form biofilms in a short period. However, the first and second were better from the viewpoint of "ease of use". All of these have their own advantages and disadvantages, respectively. Therefore, they should be properly selected and used for specific and appropriate purposes in the future. [ABSTRACT FROM AUTHOR]

Biofilms are the result of bacterial activity. When the number of bacteria (attached to materials' surfaces) reaches a certain threshold value, then the bacteria simultaneously excrete organic polymers (EPS: extracellular polymeric substances). These sticky polymers encase and protect the bacteria. They are called biofilms and contain about 80% water. Other components of biofilm include polymeric carbon compounds such as polysaccharides and bacteria. It is well-known that biofilms cause various medical and hygiene problems. Therefore, it is important to have a sensor that can detect biofilms to solve such problems. Graphene is a single-atom-thick sheet in which carbon atoms are connected in a hexagonal shape like a honeycomb. Carbon compounds generally bond easily to graphene. Therefore, it is highly possible that graphene could serve as a sensor to monitor biofilm formation and growth. In our previous study, monolayer graphene was prepared on a glass substrate by the chemical vapor deposition (CVD) method. Its biofilm forming ability was compared with that of graphite. As a result, the CVD graphene film had the higher sensitivity for biofilm formation. However, the monolayer graphene has a mechanical disadvantage when used as a biofilm sensor. Therefore, for this new research project, we prepared bilayer graphene with high mechanical strength by using the CVD process on copper substrates. For these specimens, we measured the capacitance component of the specimens' impedance. In addition, we have included a discussion about the possibility of applying them as future sensors for monitoring biofilm formation and growth. [ABSTRACT FROM AUTHOR]

The intrinsic contact angle between liquid metal and a solid substrate is important for interpreting the contact interaction between them. However, the apparent contact angle revealed in a wetting test does not always coincide with the intrinsic angle. In this study, the intrinsic contact angle of liquid silver on monocrystalline and polycrytalline graphite substrates was investigated by means of a sessile drop method under a 10%H2−Ar atmosphere at 1273 K. The intrinsic contact angles were estimated to be 124° for the monocrystalline (C surface) and 127° for the polycrystalline. [ABSTRACT FROM AUTHOR]

Palladium nanoparticles encapsulated into graphite (Pd–graphite intercalation compound: Pd–GIC) were produced from two kinds of graphite, natural graphite (average flake size: 270 μm) and kish graphite (average flake size: 15 μm). Hydrogen storage properties of Pd–GIC have been investigated by means of differential scanning calorimetry (DSC) between 473 and 573 K at 1.0 MPa hydrogen pressure. It is found from the DSC measurement that Pd–GIC can absorb and emit hydrogen. [Copyright &y& Elsevier]

The decay of nano-islands on the surface of a Au(111) electrode, in contact with 50 mM sulfuric acid aqueous solution under an applied potential in the range of 0.15–1.2 V, has been investigated using electrochemical atomic force microscopy (EC-AFM). The results are compared with those previously obtained for Au(100). With either orientation, it is found that the area of the top layer of multi-layered islands decreases linearly with time at any applied potential. It was also found that the decay rate, defined as the rate of decrease of the number of atoms in the top-layer of the islands per second, increases with the magnitude of the applied potential. Further, the decay rate of the top layer of the islands on Au(111) is almost the same as that on Au(100). [Copyright &y& Elsevier]

Steelmaking slags are a promising resource as artificial seaweed beds for the reconstitution of marine environments. To grow seaweed well, the formation of biofilms is an essential process in biofouling. This study focused on the formation of initial biofilms on steelmaking slag samples and analyzed the resulting bacterial communities using the next-generation sequencing technique. Three types of steelmaking slag were submerged in an area of Ise Bay in Mie Prefecture, Japan, for 3 and 7 days in the summer and winter seasons to allow the formation of biofilms. The bacterial communities of these biofilms were richer in sulfur-oxidizing bacteria compared to the biofilms formed on polyurethane sponges. It was found that Helicobacteraceae dominantly grew on the biofilms formed on the slag samples. This shows that steelmaking slags have potential to be used as artificial seaweed beds and marine water purifiers. [ABSTRACT FROM AUTHOR]

N,N-diethyl-N-(2-methancryloylethy)-N-methylammonium bis(trifluoromethylsulfonyl) imide polymer (DEMM-TFSI) brush coated specimens (substrate: glasses) and a liquid ion type of polymer brush coating were investigated for their antifouling effect on biofilms. Biofilms were produced by two kinds of bacteria, E. coli and S. epidermidis. They were formed on specimens immersed into wells (of 12-well plates) that were filled with culture liquids and bacteria. The biofilm formation was observed. Also, brush coated specimens and glass substrates were investigated in the same way. DEMM polymer brush coated specimens formed more biofilm than PMMA (polymethyl methacrylate) polymer brush coated specimens and glass substrates. A greater amount of polarized components of biofilms was also observed for DEMM polymer brush coated specimens. The polar characteristics could be attributed to the attraction capability of bacteria and biofilms on DEMM polymer brush coated specimens. When considering the ease of removing biofilms by washing it with water, the ionic liquid type polymer brush (coated specimens) could be used for antifouling applications. If an initial antifouling application is needed, then the polar characteristics could be adjusted (design of the components and concentrations of ionic liquids, etc.) to solve the problem. [ABSTRACT FROM AUTHOR]