4 Material und Umwelt
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- 4 Material und Umwelt (45) (entfernen)
The halophilic bacterium Halomonas elongata can tolerate salt concentrations above 10% NaCl and uses the accumulation of the compatible solute ectoine as a major osmoregulatory mechanism. Ectoine can be accumalted inside the cell through import from the medium or de novo synthesis and establishes an osmotic equilibrium with the surrounding1. Ectoine also protects proteins from the effects of freezing, drying and high temperatures4 and DNA from ionizing radiation2. These features make ectoine a valuable compound for cosmetics and medical devices.
H. elongata was originally isolated from a solar salt facility, where it thrives under high salt concentrations. It was found that marine prokaryotes, which are exposed to high oxidative stress in their environment, vary glycolytic strategies5. A variation in the use of the glucose metabolic pathways is also assumed for H. elongata.
The particle size distribution is considered the most relevant information for nanoscale property identification and material characterization. The current OECD test guideline on particle size and size distribution (TG 110) is not applicable to ‘nano-sized’ objects. In this project we thus develop a new OECD test guideline for the measurement of the size and size distribution of particles and fibers with at least one dimension in the range of 1 - 1000 nm. A fiber is defined as an object having an aspect ratio of length/diameter l/d >3. The width and length of each fiber should be measured concurrently.
In order to measure the particle size distributions, many techniques are available. 9 methods for particles and 2 methods for fibres have been tested in a prevalidation study and appropriate methods will be compared in an interlaboratory round robin test starting in February 2019.
Microbiologically influence corrosion (MIC) has become a big concern due the increased usage of different metals by our society. Microorganisms can use metal as an electron donor, causing unpredictable but serious damages. Nowadays it is known that besides sulfate reducing bacteria (SRB), other microorganisms including acetogens, iron oxidizers and methanogens can also induce MIC. Current studies related to methanogen-induced MIC (MI-MIC) mainly focused on environmental isolates from the oil and gas industry (e.g. Methanococcus maripaludis) with industrial materials e.g. iron. However, MI-MIC can occur in many other environments as well, including the oral cavity. Methanobrevibacter oralis is a methanogen isolated from the human oral cavity and was found more frequently in patients suffering from peri-implantitis/periodontitis. Titanium-implants removed from those patients have also showed clear signs of corrosion. The aim of our study is to establish and analyze corrosion potentials of dental metals (e.g. titanium) by oral methanogens. Periodontal pockets samples from patients suffering from periodontitis/peri-implantitis were taken for methanogenic and SRB enrichments. Stainless steel, pure titanium or Ti-6Al-4V alloy was used for corrosion studies. Corrosion rates and methane production were measured using weight-loss method and gas chromatography, respectively. Metal surfaces were visualized with scanning electron microscopy. Microbial communities in the dental pockets of healthy people and patients will be compared using 16S rRNA amplicon sequencing. Overall, this is the first study investigating the susceptibility of different dental implant materials to corrosion using human-related Archaea. The outcomes of this study can be further explored for a variety of clinical applications.
While studying the socio-geographic history of inks, division 4.5 of the BAM (Bundesanstalt für Materialforschung und Prüfung) together with the Centre for the Study of Manuscript Cultures in Hamburg has developed a protocol for ink analysis. It consists of a primary screening to determine the type of the ink and a subsequent in-depth analysis using several spectroscopic techniques: XRF, FTIR, and Raman. In most cases, we can obtain satisfactory results using a non-invasive protocol. However, mixed inks that contain no metals evade such a protocol. These inks constitute a heterogeneous group of media used especially in the Middle East and the Islamicate world since at least the 10th century; they are characterized by blending carbon ink and tannins, with or without the addition of vitriol.
Our own research aims primarily at recreating a socio-geographic history of inks, parchment, and papyrus and includes the comparative analysis of the writing materials of the Dead Sea Scrolls, ink and papyrus in Ancient and Hellenistic Egypt, and inks in documents from various contemporary medieval communities in Fustat (first nucleus of Cairo). During many years of study, we concluded that the continuous production of Coptic manuscripts from late Antiquity to the Middle Ages offers a unique opportunity for historical study of the ink in a large geographic area. Thanks to the collaboration with the ERC project “PAThs” (www.paths.uniroma1.it), based at the University of Rome La Sapienza, and within the activities of a PhD research dedicated to this topic, we therefore created a new branch of our project focused entirely on the analysis of Coptic inks, pigments, and dyes. This pioneering systematic study of writing materials coming from a specific area and time frame (5th-10th century) aims not only at a better understanding of the complex Coptic multicultural and plurilingual society, but also and mainly at clarifying the links among the Coptic and other societies between the ancient and medieval eras. Finally, it will cast light on the history of the technological development of inks in the eastern world, from Antiquity to the middle ages.
In addition to previously reported results on the simulated aging of polystyrene samples (PS) containing 1 wt. % hexabromocyclododecane (HBCD), we present the first results of our investigations of polypropylene (PP)-samples containing 0.1 wt. % BDE-209. All studied polymer samples were exposed to a defined weathering schedule in a climate chamber in accordance to regulation EN ISO 4892-3:2006.For the determination of BDE-209 in the collected rain water samples derived from the used climate chamber, the samples were prepared in accordance with a validated protocol. Before the analyses, each sample was spiked with 2 µL of isotopically labeled BDE-209 (13C10-BDE-209) to serve as internal standard (ISTD) in the performed stable isotope dilution analysis. Subsequently the samples were extracted with isooctane, the obtained aliquots of the extracts were concentrated to 200 µL and 2 µL of the resulting solution were injected to the GC/MS for quantification.
Additionally, the total bromine contents are monitored for the aged and untreated samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as well as X-ray fluorescence analysis (XRF) as non-destructive and rapid method. Furthermore, results from surface analysis using environmental scanning electron microscopy (ESEM) for morphological characterization of the aged and untreated samples were presented and discussed. In general, the resulting data from the accelerated aging will be compared to those from the natural weathering experiments (“atmospheric exposure”, in soil).
The atmospheric exposure was performed by placing the samples on a weathering rack, which is aligned in SW direction (in a 45° angle to the horizon). The weathering data were regularly recorded by Deutscher Wetterdienst at this site. The surfaces of the test specimens (aged and stored references) were analyzed by ESEM as well as by LA-ICP-MS and by XRF. The surface of PS and PP specimens aged outdoors present the aging under real conditions and allow the comparison to the accelerated aged specimens by means of the weathering chamber. This way, we explore the efficiency of the accelerated aging procedure, which provides the advantage of well-defined and reproducible conditions compared to natural weathering, as a tool for testing different plastic materials.
Additionally “in soil” experiments were conducted in-door in a well characterized testing soil. The soil (boulder-clay, sand with 12 % loam, particle size in total 0.2-4 mm) is filled in a free-draining concrete basin inside of an air-conditioned room. In this manner, TOC, water capacity and humidity are recorded parameters. To assure a washing out process from the samples by the raining water, the target water content is calculated to 8%. The actual humidity is measured by a tensiometer, assuring the duration of the raining period. The water content is additionally monitored by weight of the basin, capturing water from raining periods. The correct humidity is a fundamental parameter for biological activity. Samples of PS resp. PP were of dimension 10x1cm and 5 specimens were placed up to the half in the soil per basin. Microbial activity of the soil, monitored by the reference polyurethane, sets HBCD resp. BDE-209 of the samples free and will be leached from the samples by raining water. Thereafter these will be captured by passive samplers placed in a distinct distance to the samples in the soil. The “in soil” experiments are complementary to the weathering experiments due to the biological activity in the soil. These experiments simulate the fate of the brominated flame retardants in the biosphere.