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Organisationseinheit der BAM
Eingeladener Vortrag
- nein (3)
Fe K-edge XANES measurements were performed to determine the oxidation state of iron in iron gall inks. These data are used to investigate the relationship between the Fe oxidation state and ink corrosion in historical manuscripts. The oxidation state is determined using the pre-edge based on a general variation trend that was derived from model compounds and validated here independently on a suite of samples with known oxidation state and Fe in octahedral coordination (i.e. similar to Fe in gall ink). As long as suitable references for the pure ferric and ferrous state of iron gall inks cannot be pointed out, the analysis of the pre-edge of the Fe K-edge represents the only way to acquire absolute values for the Fe oxidation state (Fe3+/Fetot) with spatial resolution for this usually non-crystalline compound. Fe3+/Fetot values for the ink samples vary between ca. 0.7 and 1.0. Spatially resolved analyses performed across ink strokes of various historical manuscripts as well as newly made samples did not reveal any systematic spatial dependence. On average, historical samples that were exposed to conservation treatments show a more oxidized state. However, the measurements demonstrate explicitly that the exposure to X-rays during the XANES acquisition affects the oxidation state of Fe in most iron gall inks.
Lithium and boron are trace components of magmas, released during exsolution of a gas phase during volcanic activity. In this study, we determine the difusivity and isotopic fractionation of Li and B in hydrous silicate melts. Two glasses were synthesized with the same rhyolitic composition (4.2 wt% water), having diferent Li and B contents; these were studied in difusion-couple experiments that were performed using an internally heated pressure vessel, operated at 300 MPa in the temperature range 700–1250 °C for durations from 0 s to 24 h. From this we determined activation energies for Li and B difusion of 57±4 kJ/mol and 152±15 kJ/mol with pre-exponential factors of 1.53 × 10–7 m2/s and 3.80× 10–8 m2 /s, respectively. Lithium isotopic fractionation during difusion gave β values between 0.15 and 0.20, whereas B showed no clear isotopic fractionation. Our Li difusivities and isotopic fractionation results difer somewhat from earlier published values, but overall confrm that Li difusivity increases with water content. Our results on B difusion show that similarly to Li, B mobility increases in the presence of water. By applying the Eyring relation, we confrm that B difusivity is limited by viscous fow in silicate melts. Our results on Li and B difusion present a new tool for understanding degassing-related processes, ofering a potential geospeedometer to measure volcanic ascent rates.
The most profound consequences of the presence of Ca–Mg carbonates (CaCO3–MgCO3) in the Earth’s upper mantle may be to lower the melting temperatures of the mantle and control the melt composition.
Low-degree partial melting of a carbonate-bearing mantle produces CO2-rich, silica-poor melts compositionally imposed by the melting relations of carbonates. Thus, understanding the melting relations in the CaCO3–MgCO3 system facilitates the interpretation of natural carbonate-bearing silicate systems.
We report the melting relations of the CaCO3–MgCO3 system and the partition coefficient of trace elements between carbonates and carbonate melt from experiments at high pressure (6 and 9 GPa) and temperature (1300–1800 ◦C) using a rocking multi-anvil press. In the absence of water, Ca–Mg carbonates are stable along geothermal gradients typical of subducting slabs. Ca–Mg carbonates (∼ Mg0.1–0.9Ca0.9–0.1CO3) partially melt beneath mid-ocean ridges and in plume settings. Ca–Mg carbonates melt incongruently, forming periclase crystals and carbonate melt between 4 and 9 GPa. Furthermore, we show that the rare earth element (REE) signature of Group-I kimberlites, namely strong REE fractionation and depletion of heavy REE relative to the primitive mantle, is resembled by carbonate melt in equilibrium with Ca-bearing magnesite and periclase at 6 and 9 GPa. This suggests that the dolomite–magnesite join of the CaCO3–MgCO3 system might be useful to approximate the REE signature of carbonate-rich melts parental to kimberlites.
We present a series of remarkable structural transformations for a family of layered metal–organic frameworks (MOFs) in a three-step solid-state reaction cycle. The cycle represents new dynamic behavior of 2D coordination polymers and involves the sequence of reactions: {[Mn2(ina)4(H2O)2]·2EtOH}n (JUK-1) → {(NH4)2[Mn(ina)2(NCS)2]}n·xH2O (JUK-2) → {[Mn2(ina)2(Hina)2(NCS)2]}n (JUK-3) → JUK-1 (Hina = isonicotinic acid), each accompanied by rearrangement of intralayer coordination bonds and each induced by a different external stimulus. In situ investigation of the first step of the cycle by combined synchrotron X-ray diffraction and Raman spectroscopy reveals direct mechanochemical unzipping of JUK-1 bilayers to respective JUK-2 layers with reaction rates dependent on the milling conditions. In contrast, the reverse zipping of JUK-2 layers involves two steps and proceeds through a new MOF (JUK-3) whose structure was elucidated by powder X-ray diffraction. Magnetic measurements confirm conversions of manganese nodes in the reaction cycle. The findings indicate the possibility of developing coordination-based assemblies with large structural responses for use in smart stimuli-responsive systems and sensor technologies.
Seabird excrements (guano) have been preserved in the arid climate of Northern Chile since at least the Pliocene. The deposits of marine organic material in coastal areas potentially open a window into the present and past composition of the coastal ocean and its food web. We use the stable isotope composition of nitrogen and carbon as well as element contents to compare the principal prey of the birds, the Peruvian anchovy, with the composition of modern guano. We also investigate the impact of diagenetic changes on the isotopic composition and elemental contents of the pure ornithogenic sediments, starting with modern stratified deposits and extending to fossil guano. Where possible, 14C systematics is used for age information. The nitrogen and carbon isotopic composition of the marine prey (Peruvian anchovy) of the birds is complex as it shows strong systematic variations with latitude. The detailed study of a modern profile that represents a few years of guano deposition up to present reveals systematic changes in nitrogen and carbon isotopic composition towards heavier values that increase with age, i.e. depth. Only the uppermost, youngest layers of modern guano show compositional affinity to the prey of the birds. In the profile, the simultaneous loss of nitrogen and carbon occurs by degassing, and non-volatile elements like phosphorous and calcium are passively enriched in the residual guano. Fossil guano deposits are very low in nitrogen and low in carbon contents, and show very heavy nitrogen isotopic compositions. One result of the study is that the use of guano for tracing nitrogen and carbon isotopic and elemental composition in the marine food web of the birds is restricted to fresh material. Despite systematic changes during diagenesis, there is little promise to retrieve reliable values of marine nitrogen and carbon signatures from older guano. However, the changes in isotopic composition from primary marine nitrogen isotopic signatures towards very heavy values generate a compositionally unique material. These compositions trace the presence of guano in natural ecosystems and its use as fertilizer in present and past agriculture.
ADAMTS4-specific MR-probe to assess aortic aneurysms in vivo using synthetic peptide libraries
(2022)
The incidence of abdominal aortic aneurysms (AAAs) has substantially increased during the last 20 years and their rupture remains the third most common cause of sudden death in the cardiovascular field after myocardial infarction and stroke. The only established clinical parameter to assess AAAs is based on the aneurysm size. Novel biomarkers are needed to improve the assessment of the risk of rupture. ADAMTS4 (A Disintegrin And Metalloproteinase with ThromboSpondin motifs 4) is a strongly upregulated proteoglycan cleaving enzyme in the unstable course of AAAs. In the screening of a one-bead-one-compound library against ADAMTS4, a low-molecular-weight cyclic peptide is discovered with favorable properties for in vivo molecular magnetic resonance imaging applications. After identification and characterization, it’s potential is evaluated in an AAA mouse model. The ADAMTS4-specific probe enables the in vivo imaging-based prediction of aneurysm expansion and rupture.
We studied the oxidation and migration processes of inorganic compounds in iron gall inks with a combination of micro X-ray fluorescence analysis (micro-XRF) and micro X-ray absorption near edge structure spectroscopy (micro-XANES). With elemental mapping by micro-XRF, the correlation of the minor elements in the ink to the major element Fe was investigated. Along concentration profiles of Fe, micro-XANES measurements were carried out in order to determine the oxidation state and the local environment. With the help of model inks, we could show that Cu is a further important element in the paper degradation process due to iron gall ink corrosion.
Volatile Organic Compounds (VOC) are ubiquitous in the indoor air, since they emit from materials used indoors. Investigations of these materials are mostly carried out in test chambers under controlled climatic conditions. Quality control of these test chamber measurements is important but there is a lack of commercially available homogenous reference materials as required for round robin tests or quality assurance of laboratories. The approach of the present study is the impregnation of a supporting material with VOC, which are reproducibly released in measurable chamber air concentrations under standardised test conditions. A polymer made of Thermoplastic Polyurethane (TPU) was chosen as carrier material. It was impregnated with the VOC trimethyl pentanediol isobutyrat (texanol).
Emission testing of products is currently a rapidly increasing field of measurement activity. Labelling procedures for construction products are based on such emission test chamber measurements and hence measurement performance should be verified. A suited procedure for this purpose is the testing of one unique homogenous material in different laboratories within a Round Robin Test (RRT). Therefore, it is useful to have a reference material which can be used within inter-laboratory studies or as part of the quality management system to ensure comparable results. Several approaches on the development of reproducibly emitting materials have been published. These have in common only to emit a single VOC – toluene. Two further research studies carried out by BAM aimed to develop reference material for emissions testing containing one or more VOC in a single material. The first approach was a doped lacquer with Volatile and Semi-Volatile Organic Compounds (VOC/SVOC) and the second was Thermoplastic Polyurethane (TPU) or a Squalane/Paraffin mixture. Results received with the lacquer based material were presented in more detail.
The European biocides directive (98/8/EG) demand the control of emissions into the envi-ronment like soil, water and air. In this study a method for measuring the input of biocides into the indoor air from materials should be developed. The emission of two products containing biocides (plastic foil, wool carpet) and six different types of biocide containing formulations applied on wood or ceramic tiles were investigated in 20 or 23 l glass emission chambers. Each chamber test was performed over a period of 100 up to 200 days. SVOC show totally different emission curves in chamber tests compared to volatile organic com-pounds (VOC). They reach their maximum value after some days or weeks. Thus a period of 3 months is sometimes necessary for exact measurements. Area specific emission rates (SERa in µg/m²h) for permethrin (0.006), propiconazole (0.2), dichlofluanid (1.5), tolylfluanid (1.2), octylisothiazolinone (2.5) and for iodpropinylbutyl-carbamat (1.7) were determined.
Remake of ancient green
(2006)
Background:
Molecular-MRI is a promising imaging modality for the assessment of abdominal aortic aneurysms (AAAs). Interleukin-1β (IL-1β) represents a new therapeutic tool for AAA-treatment, since pro-inflammatory cytokines are key-mediators of inflammation. This study investigates the potential of molecular-MRI to evaluate therapeutic effects of an anti-IL-1β-therapy on AAA-formation in a mouse-model.
Methods:
Osmotic-minipumps were implanted in apolipoprotein-deficient-mice (N = 27). One group (Ang-II+01BSUR group, n = 9) was infused with angiotensin-II (Ang-II) for 4 weeks and received an anti-murine IL-1β-antibody (01BSUR) 3 times. One group (Ang-II-group, n = 9) was infused with Ang-II for 4 weeks but received no treatment. Control-group (n = 9) was infused with saline and received no treatment. MR-imaging was performed using an elastin-specific gadolinium-based-probe (0.2 mmol/kg).
Results:
Mice of the Ang-II+01BSUR-group showed a lower aortic-diameter compared to mice of the Ang-II-group and control mice (p < 0.05). Using the elastin-specific-probe, a significant decrease in elastin-destruction was observed in mice of the Ang-II+01BSUR-group. In vivo MR-measurements correlated well with histopathology (y = 0.34x-13.81, R2 = 0.84, p < 0.05), ICP-MS (y = 0.02x+2.39; R2 = 0.81, p < 0.05) and LA-ICP-MS. Immunofluorescence and western-blotting confirmed a reduced IL-1β-expression.
Conclusions:
Molecular-MRI enables the early visualization and quantification of the anti-inflammatory-effects of an IL-1β-inhibitor in a mouse-model of AAAs. Responders and non-responders could be identified early after the initiation of the therapy using molecular-MRI.
Two divalent manganese aminophosphonates, manganese mono (nitrilotrimethylphosphonate) (MnNP3) and manganese bis N-(carboxymethyl)iminodi(methylphosphonate)) (Mn(NP2AH)2), have been prepared by mechanochemical synthesis and characterized by powder X-ray diffraction (PXRD). The structure of the novel compound Mn(NP2AH)2 was determined from PXRD data. MnNP3 as well as Mn(NP2AH)2 exhibits a chain-like structure.
In both cases, the manganese atom is coordinated by six oxygen atoms in a distorted octahedron. The local coordination around Mn was further characterized by extended X-ray absorption fine structure. The synthesis process was followed in situ by synchrotron X-ray diffraction revealing a three-step reaction mechanism. The asprepared manganese(II) phosphonates were calcined on air.
All samples were successfully tested for their suitability as catalyst material in the oxygen evolution reaction.