PH-responsive release of chlorhexidine from modified nanoporous silica nanoparticles for dental applications

A pH-sensitive stimulus-response system for controlled drug release was prepared by modifying nanoporous silica nanoparticles (NPSNPs) with poly(4-vinylpyridine) using a bismaleimide as linker. At physiological pH values, the polymer serves as gate keeper blocking the pore openings to prevent the release of cargo molecules. At acidic pH values as they can occur during a bacterial infection, the polymer strains become protonated and straighten up due to electrostatic repulsion. The pores are opened and the cargo is released. The drug chlorhexidine was loaded into the pores because of its excellent antibacterial properties and low tendency to form resistances. The release was performed in PBS and diluted hydrochloric acid, respectively. The results showed a considerably higher release in acidic media compared to neutral solvents. Reversibility of this pH-dependent release was established. In vitro tests proved good cytocompatibility of the prepared nanoparticles. Antibacterial activity tests with Streptococcus mutans and Staphylococcus aureus revealed promising perspectives of the release system for biofilm prevention. The developed polymer-modified silica nanoparticles can serve as an efficient controlled drug release system for long-term delivery in biomedical applications, such as in treatment of biofilm-associated infections, and could, for example, be used as medical implant coating or as components in dental composite materials

How to measure monotony-related fatigue? A systematic review of fatigue measurement methods for use on driving tests

The aim of this study is to identify suitable science-based methods for measuring monotony-related fatigue. Monotony is one of three causes of fatigue that to date has rarely been considered in isolation. With an ongoing automation of the driving task the drivers monotony will drastically increase in the future. The methods used, such as the questions asked in interviews, can influence and distort the monotony experienced by subjects during driving tests. For this reason, not all measurement methods generally used to measure fatigue can be used when studying the role of monotony. A systematic literature search based on previously defined criteria allowed us to identify 53 publications which adequately described and evaluated the measurement methodology used to measure fatigue. The result was a list of 25 methods used in the 53 studies that we analysed. These include studies of drivers’ condition data and data about their performance. The measurement methods were evaluated based on the evaluations published by the authors who used each method. Further the methods influence on a monotonous study design was critically discussed by the authors of this paper. The paper concludes with a derived measurement concept for simulated driving tests. This work supports future research teams in the selection of a suitable measurement concept for investigating monotony related fatigue and appropriate countermeasures

Area-wide soil parameters of the germanic-roman battlefield site Harzhorn, Northeim (Lower Saxony, Germany)

Within the framework of the DFG-funded project Archaeological and geoarchaeological investigations at the germanic-roman battlefield site Harzhorn (Northeim, Lower Saxony, Germany), more than 630 samples of the topsoil were taken in relatively high spatial density in order to investigate the relationship between soil parameters and the conservation status of iron objects. The Harzhorn incident took place around the year 235 CE on a Muschelkalk ridge (Harzhorn site) and a neighbouring hill (Kahlberg site) consisting of Jurassic limestone. Upper Buntsandstein and Quaternary loess also occur in some areas. During previous archaeological excavations, the very heterogenuous preservation of iron finds, such as arrow heads, pilae, or shoe nails, was noticed and a correlation with the surface geology/soil properties was assumed. In order to investigate into this relationship, soil samples were taken across the areas at a relatively high density. The sampling was carried out in 2018, the laboratory analyses in the Laboratory for Physical Geography of the Institute for Geographical Sciences at Freie Universität Berlin were finished in 2019. At the Harzhorn site, the vast majority of archaeological finds were discovered at a depth between 15 - 20 cm. As we were interested in the area-wide in situ soil conditions to evaluate the soil aggressiveness, the soil samples at the Harzhorn site were taken at a depth of 15 cm. At the Kahlberg site, the vast majority of archaeological finds were discovered at a depth between 25 - 30 cm. Thus, at the Kahlberg site the soil samples were taken at a depth of 25 cm. Additionally, in the course of archaeological excavations, we sampled 8 profiles at different depths at the Kahlberg site. All samples were analysed with regard to: pH value (Hanna instruments pH meter, measured in KCl), Electric conductivity (Hanna instruments EC meter, measured in distilled water), and loss on ignition (550°C + 880°C). On a selected number of samples grain size analyses were carried out (laser particle sizer LS 13320 PIDS Beckman Coulter)