A real-time estimator of electrical parameters for vector controlled induction motor using a reduced order extended Kalman filter

This paper presents an application of the extended Kalman filter (EKF) to the simultaneous on-line estimation of the dq rotor flux components and all the electrical parameters of a vector controlled induction motor. A time-discrete reduced order model structure is deduced and presents a simple and reduced state equation and a scalar output equation. This approach, combined with the use of the rotor reference frame, offers advantages for real-time identification, compared with full order models, because it reduces the computational cost. The proposed new approach requires the measurement of motor speed, stator voltages and currents signals. Simulation and experimental studies presented in this paper highlight the improvements produced by this new approach based on the extended Kalman filter and a new discretization technique, under real operation conditions

Effects of Experimental Agents Containing Tannic Acid or Chitosan on the Bacterial Biofilm Formation in Situ

Chitosan and tannic acid are known for their antibacterial properties. In the present in-situ study, their antibacterial and anti-adherent effects on biofilm formation on enamel were investigated. Six subjects carried upper jaw splints with bovine enamel specimens, allowing in-situ biofilm formation. During the two-day trial, subjects rinsed with experimental solutions that contained either chitosan, tannic acid (pH = 2.5), tannic acid (pH = 7) or hydrochloric acid. Water served as the negative and chlorhexidine as the positive control. Rinsing occurred four or five times following two different rinsing protocols to investigate both the immediate and long-lasting effects. After 48 h of intraoral exposure, the dental plaque was stained with LIVE/DEAD® BacLight, and fluorescence micrographs were evaluated by using the software ImageJ. The results were verified by scanning electron microscopy. Rinsing with chitosan resulted in little immediate antibacterial and anti-adherent effects but failed to show any long-lasting effect, while rinsing with tannic acid resulted in strong immediate and long-lasting effects. Except for a slightly lower antibacterial effect, the neutral solution of tannic acid was as good as the acidic solution. Hydrochloric acid showed neither an antibacterial nor an anti-adherent effect on dental biofilm formation. Experimental solutions containing tannic acid are promising anti-biofilm agents, irrespective of the pH values of the solutions. Chitosan, on the other hand, was not able to prevent biofilm formation

Exploratory study of nanoparticle interaction with intraorally formed dental biofilms

Background The development of nanoparticles offers promising potential for improving biofilm management; however, the biofilm itself acts as a diffusion barrier, limiting effective treatment. This study aimed to investigate the adsorption and diffusion of nanoparticles in an intraorally formed biofilm. Methods Bovine enamel specimens (n=24) were mounted on customized maxillary splints and worn intraorally by two subjects for 24 h to allow biofilm formation. Specimens not exposed to the oral cavity served as controls (n=12). Ex vivo, 20 nm gold nanoparticles with a low-charge polymer outer layer were applied to the biofilm for 10 to 30 min, followed by either a single wash, 20 washes with water, or 24 h of water storage. The outer surface and basal layer of the biofilm were analysed using scanning electron microscopy, while cross-sections were examined using transmission electron microscopy. Results After 24 h of intraoral exposure, enamel was covered by a globular-structured pellicle with bacterial adhesion and occasional biofilm formation, more pronounced in subject 2. Both facilitated nanoparticle adsorption, which increased with exposure time and remained detectable after 20 washes. In subject 2, distinctly more nanoparticles persisted after 24 h of water storage. Transmission electron microscopy confirmed outer surface retention without penetration into deeper biofilm layers. Conclusions The diffusion of 20 nm nanoparticles in dental biofilms appears limited, leaving open questions regarding the optimal nanoparticle size for effective biofilm management and their toxicological implications

Einfluss experimenteller Mundspüllösungen auf die bakterielle Biofilm-Bildung in-situ

Ziel: In dem vorliegenden in-situ-Versuch wird die antibakterielle und antiadhärente Wirkung von Tanninsäure, Hydroxylapatit und Chitosan auf die Biofilm-Bildung unter Mundhöhlenbedingungen untersucht. Material und Methode: Sechs Probanden haben Oberkiefer-Schienen mit bovinen Schmelz-Prüfkörper getragen, um eine Biofilm-Bildung zu ermöglichen. Während des zweitägigen Versuchs haben die Probanden mit experimentellen Mundspüllösungen gespült, die entweder Salzsäure (pH = 2,5), Tanninsäure (5%; pH = 2,5), Tanninsäure (5%; pH = 7), Hydroxylapatit (5%) oder Chitosan (0,5%) enthalten haben. Wasser diente als Negativ- und Chlorhexidin (0,2%) als Positivkontrolle. Die Spülung erfolgte 4 oder 5 Mal nach zwei verschiedenen Spülprotokollen, dadurch konnte sowohl die sofortige als auch die langanhaltende Wirkung untersucht werden. Nach einer 48-stündigen intraoralen Exposition wurde der Biofilm mit LIVE/DEAD BacLight gefärbt, und die fluoreszenzmikroskopischen Aufnahmen wurden mit der Software ImageJ ausgewertet. Die Ergebnisse wurden mit der Rasterelektronenmikroskopie verifiziert. Ergebnisse: In der Negativkontrolle Wasser waren die Prüfkörper zur Hälfte mit Biofilm bedeckt, der aus gleichen Anteilen lebender und toter Bakterien bestand. Mit der Positivkontrolle Chlorhexidin konnte die Bedeckung der Prüfkörper mit Biofilm und die Vitalität des Biofilms kurzfristig und langanhaltend am stärksten reduziert werden. Die Spülung mit Hydroxylapatit ergab einen geringfügigen antiadhärenten Effekt, wohingegen die Spülung mit Chitosan zusätzlich antibakteriell wirkte. Keines der beiden Mundspüllösungen zeigte eine langanhaltende Wirkung, während die Spülung mit Tanninsäure (pH = 2,5) eine langanhaltende Wirkung ergab. Mit Ausnahme der etwas geringeren antibakteriellen Wirkung war die Spülung mit der neutralen Lösung der Tanninsäure genau so gut wie mit der sauren Lösung. Die Salzsäure-Lösung zeigte weder einen antibakteriellen noch einen antiadhärenten Effekt auf die dentale Biofilm-Bildung. Schlussfolgerung: Tanninsäure zeigt selbst bei neutralem pH-Wert vielversprechende antibakterielle und antiadhärente Effekte, während die Verwendung von Hydroxylapatit oder Chitosan unter den gewählten Versuchsbedingungen die Biofilm-Bildung nicht nachhaltig beeinflussen konnte.Title: Effects of experimental agents on the bacterial biofilm formation in-situ. Objectives: In the present in-situ study the antibacterial and anti-adherent effect of tannic acid, hydroxyapatite and chitosan on biofilm formation on enamel was investigated. Materials and methods: Six subjects carried upper jaw splints with bovine enamel speci-mens, allowing in-situ biofilm formation. During the two-day trial, subjects rinsed with exper-imental agents that contained either hydrochloric acid (pH = 2.5), tannic acid (5%, pH = 2.5), tannic acid (5%, pH = 7), hydroxyapatite (5%) or chitosan (0.5%). Water served as negative and chlorhexidine (0.2%) as positive control. Rinsing was performed 4 or 5 times following two different rinsing protocols to investigate both the immediate and long-lasting effect. After 48 h of intraoral exposure, dental plaque was stained with LIVE/DEAD BacLight and fluo-rescence micrographs were evaluated by using the software ImageJ. The results were verified by scanning electron microscopy. Results: In the negative control water, specimens were half covered with biofilm consisting of equal amounts of living and dead bacteria. With the positive control chlorhexidine, the coverage of specimens with biofilm and the viability of the biofilm were reduced the most in the short and long term. Rinsing with hydroxyapatite or chitosan resulted in little anti-adherent effects, and with chitosan additionally in little antibacterial effects. Both agents failed to show any long-lasting effect, while rinsing with tannic acid (pH = 2.5) resulted in strong immediate and long-lasting effects. Except of a slightly lower antibacterial effect, the neutral solution of tannic acid was as effective as the acidic solution. Hydrochloric acid showed neither an antibacterial nor an anti-adherent effect on dental biofilm formation. Conclusion: Experimental solutions containing tannic acid are promising anti-biofilm agents, irrespective of the pH value of the solutions. Hydroxyapatite and chitosan on the other hand were not able to prevent biofilm formation.DFG, SFB 102

Evaluation of Anti-Biofilm Activity of Mouthrinses Containing Tannic Acid or Chitosan on Dentin In Situ

In contrast to enamel, dentin surfaces have been rarely used as substrates for studies evaluating the effects of experimental rinsing solutions on oral biofilm formation. The aim of the present in situ study was to investigate the effects of tannic acid and chitosan on 48-h biofilm formation on dentin surfaces. Biofilm was formed intraorally on dentin specimens, while six subjects rinsed with experimental solutions containing tannic acid, chitosan and water as negative or chlorhexidine as positive control. After 48 h of biofilm formation, specimens were evaluated for biofilm coverage and for viability of bacteria by fluorescence and scanning electron microscopy. In addition, saliva samples were collected after rinsing and analyzed by fluorescence (five subjects) and transmission electron microscopy (two subjects) in order to investigate the antibacterial effect on bacteria in a planktonic state and to visualize effects of the rinsing agents on salivary proteins. After rinsing with water, dentin specimens were covered by a multiple-layered biofilm with predominantly vital bacteria. In contrast, chlorhexidine led to dentin surfaces covered only by few and avital bacteria. By rinsing with tannic acid both strong anti-adherent and antibacterial effects were observed, but the effects declined in a time-dependent manner. Transmission electron micrographs of salivary samples indicated that aggregation of proteins and bacteria might explain the antiadhesion effects of tannic acid. Chitosan showed antibacterial effects on bacteria in saliva, while biofilm viability was only slightly reduced and no effects on bacterial adherence on dentin were observed, despite proteins being aggregated in saliva after rinsing with chitosan. Tannic acid is a promising anti-biofilm agent even on dentin surfaces, while rinsing with chitosan could not sufficiently prevent biofilm formation on dentin

Mechanical characterization of cellulose aerogels

Due to dwindling fossil resources, biobased cellulose aerogels, whose three-dimensionally structured networks are characterized by nanoscale fibrils, have been of particular interest in recent years. They can be produced by bringing the polymer chains into solution and subsequent regeneration processes and offer the low density and thermal conductivity typical of aerogels. Their bulk properties depend on their nano and microstructure, which is influenced by their manufacturing process [1]. For practical applications of cellulose aerogels, insights into their elastic and inelastic mechanical properties are desired. To the best of our knowledge, the reports in the literature merely describe the stress-strain curves under monotonic uniaxial compressive loading [2] without exploring the inelastic features. This work aims at extending the state of the art knowhow on mechanical characterization of cellulose aerogels within this context. For this purpose, cellulose aerogels having different cellulose concentrations synthesized using ZnCl2 as solvent, salt hydrate routine [3] were subjected to an intensive mechanical characterization. This included quasi static compression and tensile tests, which for the first time allow a detailed characterization of their strain dependent elastic as well as inelastic properties. Furthermore, the results will be illustrated in the context of computational design of their microstructure with already established approaches [4] to better investigate structure property relations in the future. REFERENCES [1] Rege A, Schestakow M, Karadagli I, Ratke L, Itskov M, Micro mechanical modelling of cellulose aerogels from molten salt hydrates, Soft Matter. 12(34),7079-88, 2016. [2] Buchtova N, Pradille C, Bouvard JL, Budtova T, Mechanical properties of cellulose aerogels and cryogels, Soft Matter, 15, 7901-8, 2019. [3] Schestakow M, Karadagli I, Ratke L, Cellulose aerogels prepared from an aqueous zinc chloride salt hydrate melt, Carbohydrate Polymers, 137, 642-9, 2016. [4] Aney S, Rege A, The effect of pore sizes on the elastic behaviour of open porous cellular materials, Mathematics and Mechanics of Solids, 0(0), 2022

Nanostrukturierte Cellulose-Aerogel-Polyesterverbunde

The mechanically stable nature of cellulose makes it potentially suitable for the reinforcement of polymers. In dissolving the initial cellulose in an aqueous zinc chloride salt hydrate melt it is shaped into a desired form, regenerated, washed, and dried in supercritical CO2 to yield Cellulose-Aerogel (CA) sheets. The aerogel offers a three dimensional network of open porous and thus well accessible cellulose fibrils of 7-25 nm in diameter and lengths of several 100 nm. That randomly arranged nano fibrous felt serves as a predefined network that can be infused by a suitable matrix system to achieve Cellulose-Aerogel Reinforced Polymers(CARPs). The air contained in the aerogel is replaced by capillary assisted infusion with an unsaturated polyester resins for the matrix system to give outstanding composite materials. The density of these composites is found to be only slightly above that of the thermoset itself, since only 6-22 vol.% of fiber reinforcement already has an impact. Mechanical testing using impulse excitation, dynamic mechanical analysis, tensile, and 3-point bending reveal significant improvement by multiplication of the Young’s modulus with respect to the reference thermoset. Furthermore, the incorporation of the cellulose network allows for substantially altered deformation mechanisms yielding shear fracture in CARPs and cleavage fracture in CA. Apart from the strong frequence dependency enormous breaking elongations (>20 %) are observed. Digital image correlation is used to follow local deformation and SEM investigations depict the effect of the Cellulose-Aerogel on the strain behaviour of the final composite material. The strong dependency on the strain rate and the inability of necking leads to the conclusion of CARPs being superplastic materials. As a result, the predefined network of high strength cellulose fibrils can very well serve as a renewable fiber reinforcement for polymers (FRP) utilizing its full potential to yield high performance polymer composites

Impact of modifications on the characteristics of salivary pellicle on dental hard tissue - a scoping review

Recent advances in pellicle engineering have introduced new strategies to enhance dental health by modifying the pellicle, a thin layer of salivary proteins and macromolecules that covers and protects the tooth surface. Despite the growing interest in pellicle modification, a comprehensive evaluation of how different agents affect the pellicle’s characteristics has not been conducted. This scoping review aims to analyze the impact of various modification agents on the structure, composition, and protective properties of the salivary pellicle. By identifying gaps in current research, this review seeks to highlight potential areas for future investigation and provide insights into how targeted modifications can improve the pellicle’s protective functions, ultimately contributing to better oral health

Pellicle engineering with statherin: a scoping review

This scoping review aims to systematically explore the literature on the application of statherin in pellicle engineering, with a particular focus on its capacity to enhance the protective properties of the pellicle. These protective roles include resistance to tooth wear (e.g., erosion, abrasion, attrition) and reduction of bacterial adhesion. Statherin is a salivary protein with known affinity for hydroxyapatite and potential to modulate pellicle composition and function. This review will identify existing experimental and in vivo/in situ studies, summarize the findings, and highlight knowledge gaps that could inform future research and clinical applications