4 Material und Umwelt
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Zearalenone (ZEN) and its sulfate and glucoside conjugates have been detected in (a broad variety of) food and feed commodities1. Both conjugated derivatives are formed as part of fungal or plant secondary metabolism and thus, belong to the group of modified mycotoxins2. After consumption of contaminated foodstuff, the conjugates can be hydrolyzed by human intestinal microbiota leading to liberation of ZEN that implies an underestimation of the true ZEN exposure. In order to include ZEN conjugates in routine analysis, as well as for toxicological investigation reliable standards are needed.
The objective of the present study was to develop a simple and economic method for biosynthesis of ZEN conjugates. Preceding experiments on the biotransformation of ZEN by Rhizopus and Aspergillus species showed a mixed metabolite formation3. Therefore, these known ZEN conjugating fungal strains were screened for their potential to selectively synthesize the ZEN derivatives ZEN-14-sulfate (Z14S), ZEN-14-glucoside (Z14G) and ZEN-16-glucoside (Z16G). The screening was conducted by adding ZEN to liquid fungal cultures. Cultivation conditions and ZEN incubation time were varied. All media samples were analyzed for metabolite formation by HPLC-MS/MS. Z14S was exclusively formed by A. oryzae. Under optimized conditions a specific biosynthesis of Z14G by R. oryzae and Z16G by R. oligosporus was achieved. After liquid-liquid-extraction and preparative chromatographic cleanup 1H-NMR purities of ≥ 73% for Z14S, ≥ 82% for Z14G and ≥ 50% for Z16G were obtained. In addition, a consecutive biosynthesis was developed by first using Fusarium graminearum for ZEN biosynthesis on rice based liquid medium. After inactivation of Fusarium the subsequent conjugation reaction was conducted utilizing Aspergillus and Rhizopus species under the various optimized conditions.
In this study an easy and cost-efficient biosynthesis for Z14S, Z14G and Z16G was developed. The developed biosynthesis could be also used for other metabolites like ZEL conjugates. Our results of the in vitro screening indicate also the formation of a ZEL-glucoside and α ZEL-sulfate as major metabolites by R. oryzae. In sum, under optimized cultivation conditions fungi can be easily utilized for a targeted and stereospecific synthesis of ZEN conjugates.
Bee populations have declined significantly in recent years and this is thought to be attributable at least in part to the (re-)emergence of viruses. These viruses are predominantly positive single stranded (+ss) RNA viruses belonging to the Picornavirales. Managed honeybees are often infested with the invasive mite, Varroa destructor, which vectors RNA viruses including Deformed wing virus (DWV, family Iflaviridae): a leading culprit of colony losses. Many bee viruses have been sequenced and structural features are now available for viruses such as DWV. DWV consists of at least 3 distinct genotypes, two of which have been shown to be differentially virulent in honeybees. Molecular studies have demonstrated that DWV has a mean evolutionary rate of 1.35 x 10-3 per site per year. For such viruses – in contrast to their eukaryotic hosts – ecological and evolutionary timescales significantly overlap. This rapid evolution allows RNA viruses to adapt quickly to novel host environments with recombination representing an additional key source of genetic variation. Interestingly, recombination between genotypes of DWV has recently been shown to be a common occurrence in honeybees. A challenge has been to develop bioinformatics tools that can accurately reconstruct viral haplotypes – including recombinants – from heterogenous high-throughput sequence data.
The impact of blood-to-blood Varroa destructor transmission on virus evolution represents an important question in bee virus research. Due to the nature of the V. destructor life cycle, predictions can be made about the potential impact of the mite on virus virulence evolution. Specifically, the developing honeybee host pupa should remain alive until close to the completion of metamorphosis to provide sufficient time for successful mite reproduction, including offspring mating. For optimal transmission, any virus found in a mature and mated daughter mite will hold a significant selective advantage over a virus found in an immature or unmated daughter mite – placing a cost on virus virulence that impacts honeybee pupae before mites can mate. On the other side, viruses replicating too slowly and with delayed virulence effects will hold a selective handicap because fewer transmission units will be found in mated mites. I have hypothesized that the evolution of virus virulence shifted following the arrival of V. destructor, with viruses, including recombinants and/or specific viral genotypes being selected for a level of virulence in pupae (and likely also in adults) that maximises R0, which represents the basic reproductive number of the virus in the host population. R0 is defined by the number of subsequent infections caused by a single infection and it must be greater than 1 for an infection to spread in a population. It is enhanced by maximising the number of transmission units passed to uninfected susceptible vectors, and ultimately hosts (Figure 1).
Honeybee viruses are also shared with sympatric wild bees and viral prevalence and sequence data indicate frequent virus transmission between managed and wild bee species. In addition to infecting the western honeybee (Apis mellifera), DWV can infect other Asian honeybee species such as Apis ceranae. Outside of honeybees, DWV has been found widely in bumblebees, including solitary bees and wasps and there is evidence that it can actively replicate in several Bombus and solitary bee species. Whether the arrival of the V. destructor mite in A. mellifera has driven viral emergence in non-Apis bees is a target of ongoing research.
Technical advances in the study of molecular evolution have crystallized the fundamental insight that many bee pathogens evolve and adapt over timescales that overlap with host ecology. At the same time, the role played by bee host community ecology is increasingly being appreciated in host-parasite interactions. Here, we focus on Deformed wing virus (DWV) and present recent studies exploring the link between virulence, DWV genetic diversity and changes to host ecology - namely the arrival of an invasive ectoparasite, the Varroa destructor mite, which vectors viruses between honeybees. Specifically, we show how V. destructor may have created conditions for the emergence of more virulent strains of DWV in the western honeybee, Apis mellifera. We present a molecule-to-ecology framework to help interpret findings and to guide future hypotheses, emphasizing the role of molecular interactions between viruses and host immunity as drivers of change at the bee population level.
Our understanding of RNA viruses from edible insects is minimal at best, with studies largely focusing on model insect species and those associated with obvious signs of disease. This represents a considerable gap in understanding, given the growing role of insects as a source of food and feed, as well as the more general relevance of insects in agriculture and health. Illness due to entomophagy is rare but well documented, including fatal cases following the consumption of termites. Termites are eaten commonly in tropical Asia, Africa and South America, and are among the insects with the highest recorded fat content. There are many species of termites, with a wide range of diets and habitats centering around the consumption of wood and soil substrates. In this study, we report the results from a survey of more than 30 cockroach and termite transcriptomes, with the aim of understanding the diversity and evolution of RNA viruses as well as other potentially pathogenic organisms that are associated with this relevant but somewhat overlooked group of insects. We discuss our results in the context of the possible zoonotic risk posed by insects, as well as in the context of emerging viral and other disease threats that may face insects being reared at industrial scales.
The termites are a derived eusocial lineage of otherwise non-social cockroaches. Understanding the proximal and ultimate drivers of this major evolutionary transition represents an important goal in biology. One outstanding question concerns the evolution of termite immunity, which is thought to have undergone broad-sweeping adaptations in order to enhance group-level immune protection. To understand the evolutionary origins of termite immunity, we conducted qualitative and quantitative transcriptome analyses along a gradient of sociality. Firstly, we aimed to identify large-scale genetic shifts in immune traits linked to eusociality by comparing immune gene repertoires in solitary and subsocial cockroaches and across a range of eusocial termite lineages. Secondly, we compared the responses of a solitary cockroach, a subsocial wood-roach and different castes of a lower termite species to a non-specific immune challenge, in order to understand how sociality may have influenced the evolution of immune gene regulation. Firstly, we found that termites have a broadly representative repertoire of canonical immune genes as compared to gregarious cockroaches and subsocial wood-roaches. Secondly, with respect to immune challenge, the solitary cockroach and the subsocial wood-roach displayed a similarly comprehensive induced response, while the termite response was considerably dampened by comparison and strongly influenced by caste; with reproductives displaying a generally higher constitutive level of immune-gene expression compared to sterile castes. In summary we did not find termite eusociality to be associated with significant changes in immune gene diversity, but rather to be linked with significant modifications to the regulation of immunity following the origin of division of labour.
X-ray fluorescence analysis, due to its non-destructive nature and ist suitability to work with historic objects in situ, quickly became one of the most important methods for the evaluation of iron-gall ink. The main advantage of this qualitative and semi-quantitative method is that it makes it easy to differentiate between inks, based on the assumption that the differences result from the manufacture of the ink.
This work explores the question whether the ink ‘fingerprint’ results strictly from the elemental composition of the basic ink ingredients even if it is stored in vessels made of metals or metal alloys. In addition, we tested and compared the performance of three different XRF spectrometers.
We prepared various lab-grade inks according to historical ink recipes and measured the metal content of the ink deposited on sized cotton Linters paper with three types of XRF spectrometers: a simple hand-held device with an interaction spot of 4 mm and two devices equipped with poly-capillary Xray optics for line scanning and imaging. Since the exact elemental mass composition of the non-aged ink samples was known, we were able to evaluate the accuracy of the research procedure. Lab-grade inks were then aged in the metal jars imitating inkwells. The aging of the inks in the metal containers resulted in the significant change of the primary inks fingerprint as opposed to that of the control inks stored in glass containers. This effect was independently confirmed by the measurements conducted with every instrument we used. We will present a brief comparison of the results 43 achieved when using different spectrometers and a possible hypothesis explaining the processes that occurred.
The mayor part of the Berlin collection `Manuscripta Americana´ consists of documents compiled by Alexander von Humboldt. The diversity of the written fragments and their shape presume few accordance concerning purpose, place or time of production. Even before the papers came to Berlin, manuscripts were copied, divided and collected by famous scholars also in Mexico. Back in Europe, Humboldt visited further collections and published the detected hieroglyphic writings altogether with cultural objects and landscapes in the book `Vues des Cordillères et Monuments des Peuples Indigènes de l`Amerique, voyage de Humboldt et Bonpland´, labelled corresponding to the cultural background.
By scientific and culture historical analyses, the Humboldt codices are revised and related to each other and others. In especial, the compilation of fragments shown on plate 36 in the book is looked at more closely. Whereas most of the plates represent only one sheet of painted amate paper, here segments with details of seven fragments are put together. It is tried to comprehend why these pieces are on one plate.
To find out a common feature of the documents, their content and represented form are compared. A correlation between some pieces is obvious and thus is also expected in the manufacture of the codices, in the kind of material used. For this the inks and colors are determined by scientific analysis including XRF-, Raman-, FTIR- and VIS- spectroscopy. Special material is detected and related to results of former analysis of codices written during the colonial period of America. Herewith a clear cultural assignment of the manuscripts is performed.
A relation of the fragments represented on plate 36 among each other and to other codices of the collection Manuscripta Americana in Berlin is discussed. Also, if the manuscripts are unique `originals´ or represent fragments of documents, whose corresponding pieces maybe found- in the best case- incorporated in other collections. We detected, that at least two of them can be put into relation to similar manuscripts deposited in Mexico. Further material analysis should clarify, if the corresponding pieces are identical- from one document, or if one of them is a copy. Herewith an approximation to authenticity features and history is issued.
Antimicrobial resistance is a major threat to human health. The prevalence of multi-drug resistant (MDR) bacteria is predicted to increase in the future requiring robust control strategies. One cornerstone to prevent the spread of MDR bacteria in clinical settings is the application of disinfectants to improve hygiene standards. However, bacteria can evolve resistance to disinfectants, which in turn can confer cross-resistance to antibiotics. Additionally, clonal bacterial populations can display phenotypic heterogeneity with respect to the tolerance of antibiotic stress leading to a prolonged survival of a sub-population; this phenomenon is termed persistence. Persistence to antibiotics is an evolvable trait and can serve as a stepping stone for the evolution of genetically encoded resistance. Until now, there is a lack of systematic studies that investigate if bacterial populations establish persister subpopulations that tolerate disinfectant stress longer than the majority of the population. Our results in E. coli indicate that persistence is a bacterial survival strategy against benzalkonium chloride, a widely used disinfectant.
In future experiments, we will investigate the evolution of persistence in the face of fluctuating exposure to disinfectants and whether persistence facilitates resistance against disinfectants. Lastly, we will test how tolerance and resistance against disinfectants affects susceptibility against antibiotics.
Infections with multi-resistant Gram negative pathogens are a major threat to our health system. In order to serve the needs in antibiotics development we selected untapped bioresources and implemented high throughput approaches suitable for the discovery of strains producing antibiotics with anti-Gram negative activity.
Our approaches rely on the hypothesis that Termite associated bacteria are likely to produce potent antibiotics to defend their hosts against entomopathogenic microorganisms. Termite nests and guts harbor suitable, highly diverse microbiomes in which bacterial taxa are present known to potentially produce natural compounds. In
a first step the diversity of Coptotermes species nest microbiomes was assessed carefully by using 16S rDNA amplicon sequencing on the Illumina MiSeq platform and nest material was selected to retrieve viable cells by using Nycodenz density gradient centrifugation. In order to analyze the diversity of the culturable termite nest microbiome, bacterial cells were either distributed in 384-well plates
(approach 1) or encapsulated in small spheric agarose beads by an high throughput microfluidics technique (approach 2). Cultures obtained from approach 1 were scaled-up in 96-well Duetz-systems for characterization of diversity and for rapid supernatant screening using the bioluminescence-labeled E. coli pFU166. The generated
droplets of approach 2 simultaneously received a small population of GFP-tagged Gram negative screening cells and were sorted for low fluorescence using FACS. After elimination of redundancy we performed a fast scale-up of active strains.
Implementation of this pipeline allows us to prioritize antibiotics producing strains in a ultra-high throughput fashion and by cultivation of broad diversity in our approches.
Environmental sustainability and –stability of Materials concerning the Migration of pollutants
(2018)
MaUS is an acronym for ”Material und Umweltsimulationen“. Plastics are in the focus of environmental politics due to their long-term behaviour and therefore to their persistence. Not only that they appear as visible contaminants in the sea and on the beach, but their unknown behaviour concerning their additives as well as the related transformation products are anxious. Therefore, we wish to establish a certified reference method to provide a method for testing plastics.
Aim of this project is the development of fast motion standard reference methods for testing plastics regarding to their environmental compatibility. To establish these testing methods, we use polystyrene (PS) and polypropylene (PP) with environmental relevant brominated flame retardants, known for their persistent bioaccumulative and toxic (PBT) properties. In case of PS the material contains 1 wt% of 1,2,5,6,9,10-hexabromocyclododecan (HBCD) and in case of PP 0.1 wt% bromodiphenylether (BDE-209), which is known as a substance of very high concern (SVHC). Furthermore, we use polycarbonate (PC), which is still used as material in baby flasks and releases Bisphenol A (BPA), an estrogenic active substance.
As an additional material PTFE is used for its importance as a source for two ubiquitous environmental substances (PFOS and PFOA), whose toxicological effects are still incompletely known.
The focus in this current work is set on the transfer of potential pollutants out of applied materials mentioned above into environmental compartments like water or soil. Here an accelerated aging concept should be developed to shortened time consuming natural processes. For these resulting simulations we use a programmable weathering chamber with dry and wet periods and with high and low temperatures. These programmes run for several weeks and according to a defined sampling schedule we take water samples, run a clean-up procedure by SPE (Molecular imprinted polymers (MiPs) resp. polymer-based cartridges (Waters Oasis HLB)) and analyse them by HPLC-UV resp. LC-MS/MS. Of most interest in case of flame retardants are photocatalytic transformation products. Therefore, we conduct a non-target-screening resp. a suspected target-screening by LC-MS/MS and HRMS.
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.
Background Bacterial biofilms are regarded as the most common cause of chronic infections and are often associated with medical devices, such as implants and catheters. Bacteria growing in biofilms produce a protective, extracellular matrix, which enables them to tolerate much higher antimicrobial concentrations than free-living bacteria and survive long enough to acquire antimicrobial resistance. Preventive and therapeutic strategies against biofilm infections in clinical settings commonly involve the application of multiple antimicrobials: biocidal coatings on the biomaterials and systemically administered antibiotics. This frequent practice harbors the risk of the development of cross-resistance via shared resistance mechanisms between antimicrobials used in material coatings and administered antibiotics.
Aim Our goal is to determine how bacteria adapt to antimicrobials during biofilm formation on surfaces coated with antimicrobials and how population dynamics within biofilms affect the transmission of resistance mutations. Specifically, we want to identify antimicrobial-antibiotic-combinations that select for and against antibiotic resistance in biofilms by following the population dynamics of resistant and susceptible strains in competition assays on a single cell level.
Methodology To study the effect of antimicrobial-antibiotic exposure on resistance development and population dynamics on bacterial biofilms in a multidrug environment, we will grow Pseudomonas aeruginosa on glass surfaces with and without antimicrobial coatings and expose them to antibiotics. First, we will screen in vitro for combinations of antibiotics and antimicrobials that select for and against antibiotic resistance. Second, effective combinations will be chosen for in-depth investigations during bacterial adhesion and of mature biofilms of resistant and susceptible genotypes. Third, based on the outcome of the screen and the obtained mechanistic understanding we will choose a clinical example in which we study the relevance of our findings in biofilms grown in vivo.
Relevance Studying the biointerfacial interactions between bacterial biofilms and medical devices in terms of population dynamics as well as on single cell level during multidrug selection will help us understand how drug resistance develops and spreads in persistent biofilm infections. Based on our findings we aim to provide clinical recommendations for improved administration of antibiotics/antimicrobials in combination with medical device materials in order to mitigate against biofilm associated antimicrobial resistance.
Selection of resistance in bacteria grown on antimicrobial surfaces in a multidrug environment
(2018)
Bacterial biofilms are regarded as the most common cause of chronic infections and are often associated with medical devices, such as implants and catheters. Bacteria growing in biofilms produce a protective, extracellular matrix, which enables them to tolerate much higher antimicrobial concentrations than free-living bacteria and survive long enough to acquire antimicrobial resistance. Preventive and therapeutic strategies against biofilm infections in clinical settings commonly involve the application of multiple antimicrobials: antimicrobial coatings on the biomaterials and systemically administered antibiotics. This frequent practice harbors the risk of the development of cross-resistance via shared resistance mechanisms between antimicrobials used in material coatings and administered antibiotics.
Our goal is to determine how population dynamics within biofilms affect the transmission of resistance mutations. Specifically, we want to identify antimicrobial-antibiotic-combinations that select for and against antibiotic resistance in biofilms by following the population dynamics of resistant and susceptible strains in competition assays. Gaining a better understanding about resistance development and spread in persistent biofilm infections will enable us to provide clinical recommendations for improved administration of antibiotics/antimicrobials in combination with medical device materials to mitigate against biofilm associated antimicrobial resistance.
Here, we will discuss our first findings on the effects of combinations of the carbapenem drug meropenem and various antimicrobials.
Background Bacterial biofilms are regarded as the most common cause of chronic infections and are often associated with medical devices, such as implants and catheters. Bacteria growing in biofilms produce a protective, extracellular matrix, which enables them to tolerate much higher antimicrobial concentrations than free-living bacteria and survive long enough to acquire antimicrobial resistance. Preventive and therapeutic strategies against biofilm infections in clinical settings commonly involve the application of multiple antimicrobials: biocidal coatings on the biomaterials and systemically administered antibiotics. This frequent practice harbors the risk of the development of cross-resistance via shared resistance mechanisms between antimicrobials used in material coatings and administered antibiotics.
Aim Our goal is to determine how bacteria adapt to antimicrobials during biofilm formation on surfaces coated with antimicrobials, how antimicrobial resistance mutations are acquired and evolve within mature biofilms, and how population dynamics within biofilms affect the transmission of resistance mutations. Specifically, we want to identify antimicrobial-antibiotic-combinations that select for and against antibiotic resistance in biofilms by following the population dynamics of resistant and susceptible strains in competition assays.
Methodology We will grow biofilms of Pseudomonas aeruginosa on glass surfaces with and without antimicrobial coatings and expose them to antibiotics. Then we will track their physiological properties, evolutionary adaptations, and population dynamics. First, we will screen in vitro for combinations of antibiotics and antimicrobials that select for and against antibiotic resistance. Second, effective combinations will be chosen for in-depth investigations during bacterial adhesion and of mature biofilms of resistant and susceptible genotypes. Third, based on the outcome of the screen and the obtained mechanistic understanding we will choose a clinical example in which we study the relevance of our findings in biofilms grown in vivo.
Relevance Studying the biointerfacial interactions between bacterial biofilms and medical devices in terms of population dynamics as well as on single cell level during multidrug selection will help us understand how drug resistance develops and spreads in persistent biofilm infections. Based on our findings we aim to provide clinical recommendations for improved administration of antibiotics/antimicrobials in combination with medical device materials in order to mitigate against biofilm associated antimicrobial resistance.
This work presents the non-destructive spectroscopic characterisation of original Dead Sea Scrolls (DSS)parchment fragments from Ronald Reed collection. The fragments are of paramount importance becausethey have never been subjected to any treatment of preservation and restoration, this allows to investi-gate the manufacturing method of real original Jewish parchments. The manufacture of “sacred” Jewishparchments, in fact, is traditionally supposed to use a superficial tannin treatment. To study the DSS frag-ments, it was necessary both to analyse mock-up samples, especially manufactured in order to reproduceancient Oriental Jewish ritual parchments, and to compare the results with those obtained in the analysisof modern and ancient Western Jewish ritual parchments, in order to test the effectiveness of the selectedspectroscopic techniques. Traditionally, the main difference between Oriental and Western traditionalparchment preparation consisted in the dehairing method: enzymatic for Oriental and lime-based forWestern. Moreover, a finishing treatment with tannin was supposed to be applied on ritual Jewish parch-ments. The need of reference samples derives from the knowledge that each parchment preparation,treatment and degradation can induce structural modifications that affect the spectral features. FourierTransform Infrared Spectroscopy by Attenuated Total Reflection (ATR-FTIR), FT-Raman and m-Ramanwere used in this study. The experimental results allowed us to recognise, with different sensitivity, thepresence of tannin by using m-Raman and IR spectroscopies and to prove that not all the archaeologicalsamples were manufactured in the same way with vegetal extracts. Many salts (tschermigite, dolomite,calcite, gypsum and iron carbonate) were found on the surface of DSS fragments. They can derive fromthe degradation processes and storage environment before the discovery or from the manufacture. More-over, the different sensitivities and instrumental characteristics of the used techniques permitted us toestablish an analytical protocol, useful for further studies of similar materials.
Initial situation:
Aluminum is an often-used building material in modern architecture, not only for construction but as well for facades and decorative elements. In the 1950th and 1960th, after World War II, many buildings in Germany were constructed with aluminum or contain elements of colored anodized aluminum. In the last years a larger number of these buildings are increasingly in the sight of conservation works including the aluminum parts such as window frames or facade coverings.
Damaged Aluminum Surfaces:
Common damages are a change of color or gloss changes through weathering processes, drill holes or marks due to later modifications, scratches in the anodized layer due to extensive wear e.g. at handrails or door handles.
To repair damaged aluminum surfaces, there are usually two options: smaller damaged areas are repaired by using a touch-up pen. In case of larger damages, the complete re-anodization is necessary. This includes to de-anodize the surface with cleaning and grinding the whole aluminum object. Both possibilities are disadvantageous for the objects. The touch-up pen often does not match the color of the original surface together with an insufficient corrosion protection for outdoors. While the newly anodized surface differs in color and gloss from the originally applied color.
Research Approach:
The whole procedure contrasts with the principal approach in conservation which aims to intervene as less as possible, in case of the conservation of an object. To fulfill this approach in a more appropriate way the research project focuses on a mobile and partial application for colored, anodized aluminum parts.
To anodize aluminum the application of an electrolyte onto the surface together with sufficient voltage and current is necessary. Generally diluted sulfuric acid is used as electrolyte. Different possibilities are examined to enable the mobile application of the electrolyte, e. g. the application by producing a gel matrix or like in electroplating by pen or brush wrapped with a fleece fabric.
Experimental part:
First experiments are conducted to examine the structure of the anodized layer in relation with proper cleaning, anodization time with applied voltage and current and the coloring process. The aim was to reduce the preparation procedure and the anodization time as much as possible to facilitate the mobile application.
Examinations with Keyence microscope, Eddy current testing and REM are performed to characterize the layers. The results are shown in table 1. A clear connection between proper cleaning, anodization time, voltage and amperage and the achieved thickness of the anodized layer is significant. Cracks in the layer show that raising the voltage and amperage results in thicker layers but as well in a crumbled and less stable anodized surface.
Gel preparation:
In addition to the anodization process with a liquid e.g. sulfuric acid a gel application is tested to prevent the electrolyte from rinsing down during the mobile application. For this purpose, several gel-forming agents are tested together with their stability in acid systems. It was observed, that the consistency of the gels varies dependent of the time.
Conductivity:
The conductivity of sulfuric acid combined with different gel-systems was measured and compared in order to predict the possible growth of layers during anodic oxidation process.
Further steps:
Determination and optimization of application parameters like voltage, amperage and anodization-time to build up a preferably stable and sufficient thick anodized layer. Examination of gel preparation to guarantee a stable product, enforcing with textile tape for easy application.
Two new approaches towards an emission reference material for use in quality assurance measures for materials emissions testing were developed and intensively tested. The overall goal was to obtain solid materials with homogenous and reproducible (S)VOC release. Since the application in inter-laboratory comparisons is aimed at, it should furthermore be long-term stable to ensure safe shipment to the customer without sustaining compound losses. In the first approach, thermoplastic polyurethane (TPU) was impregnated with the VOC texanol under high-pressure with liquid CO2 as solvent. In the second, styrene (VOC) and the SVOC 2,6-diisopropylnaphthalene (DIPN) were spiked into vacuum grease (VG) and a mixture of paraf-fin/squalane (P/S). For the prediction of the emission rates a finite element model (FEM) was developed for the VG and P/S type materials. All requirements for reference materials were fulfilled, whereas the TPU samples need to be aged for about 10 days until repeatable and reproducible emission rates were obtained.
Two new approaches towards an emission reference material for use in quality assurance measures for materials emissions testing were developed and intensively tested. The overall goal was to obtain solid materials with homogenous and reproducible (S)VOC release. Since the application in inter-laboratory comparisons is aimed at, it should furthermore be long-term stable to ensure safe shipment to the customer without sustaining compound losses. In the first approach, thermoplastic polyurethane (TPU) was impregnated with the VOC texanol under high-pressure with liquid CO2 as solvent. In the second, styrene (VOC) and the SVOC 2,6-diisopropylnaphthalene (DIPN) were spiked into vacuum grease (VG) and a mixture of paraf-fin/squalane (P/S). For the prediction of the emission rates a finite element model (FEM) was developed for the VG and P/S type materials. All requirements for reference materials were fulfilled, whereas the TPU samples need to be aged for about 10 days until repeatable and re-producible emission rates were obtained.
Soil microbes are exposed to different environmental stressors originating from various sources. Biocides used as material preservatives can represent environmental stressors since they are in direct contact with the environment including soil. Microorganism in soils can adapt to stress by different mechanisms; for example, by transferring mobile genetic elements via horizontal gene transfer (HGT). Here, we hypothesize that material preservatives can cause increased frequencies of HGT (i.e. altered community permissiveness) facilitating microbial community adaptation to stress. Furthermore, we hypothesize that soil microbial communities are primed by biocide exposure facilitating the response to different types of stresses. We will incubate soil mesocosms with selected biocides to investigate if these compounds promote HGT of plasmids that carry resistance genes in soil microbial communities. Subsequently, we will prime the soil microbial community with sub-inhibitory concentrations of biocides followed by exposure to toxic biocide concentrations or other types of common environmental stresses including metals, antibiotics, and salt. Using suitable control experiments, a shift in the functional response of the primed as compared to the non-primed community would indicate that biocides prime microbial communities via HGT. Together these results will elucidate the effect of biocides on HGT-mediated adaptation to environmental stressors in soil microbial communities.
Soil microbes are exposed to different environmental stressors originating from various sources. Biocides used as material preservatives can represent environmental stressors since they are in direct contact with the environment including soil. Microorganism in soils can adapt to stress by different mechanisms; for example, by transferring mobile genetic elements via horizontal gene transfer (HGT). Here, we hypothesize that material preservatives can cause increased frequencies of HGT (i.e. altered community permissiveness) facilitating microbial community adaptation to stress. Furthermore, we hypothesize that soil microbial communities are primed by biocide exposure facilitating the response to different types of stresses. We will incubate soil mesocosms with selected biocides to investigate if these compounds promote HGT of plasmids that carry resistance genes in soil microbial communities. Subsequently, we will prime the soil microbial community with sub-inhibitory concentrations of biocides followed by exposure to toxic biocide concentrations or other types of common environmental stresses including metals, antibiotics, and salt. Using suitable control experiments, a shift in the functional response of the primed as compared to the non-primed community would indicate that biocides prime microbial communities via HGT. Together these results will elucidate the effect of biocides on HGT-mediated adaptation to environmental stressors in soil microbial communities.