Ingenieurwissenschaften und zugeordnete Tätigkeiten
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A high-pressure neutron diffraction study was conducted on polycrystalline samples of the two known polymorphs of 2,4,6-trinitrotoluene [monoclinic (m) and orthorhombic (o) TNT] under hydrostatic conditions. Isothermal equations of state were obtained for both polymorphic forms. Neither polymorph was observed to undergo a phase transition in the pressure region 0–5 GPa, with both polymorphs displaying smooth compression behavior across the pressure range. This differs somewhat from previous X-ray diffraction and Raman spectroscopy investigations in which discontinuities were observed in the P–V curves and spectral changes were reported at ∼2 GPa. The high-pressure response of these materials is supported by dispersion-corrected density functional theory calculations which, while overestimating the experimental bulk moduli, give excellent agreement with the observed smooth compression response of both phases.
In den vergangen Jahren hat das Umweltbewusstsein in der Bevölkerung stark zugenommen und somit auch das Interesse an der Vermeidung von anthropogenen (Schad-)Stoffen in der Umwelt. Eine (neue) Substanzklasse, deren Umweltauswirkungen noch nicht vollständig untersucht sind und die in den vergangenen Jahren immer mehr an Bedeutung gewonnen hat, sind (metallbasierte) Nanomaterialien. Im Gegensatz zu bspw. Elementspezies weisen Nanomaterialien eine Vielzahl von Eigenschaften auf und lassen sich nicht über nur ein Merkmal beschreiben - dies stellt eine große analytische Herausforderung dar. Hier haben sich vor allem die Feld-Fluss-Fraktionierung (AF4) und die single-particle-ICP-MS als leistungsstarke analytische Methoden herausgestellt. In (aquatischen) Umweltmatrizes (z.B. Oberflächengewässern) liegen neben artifiziellen auch natürliche Partikel vor, was eine weitere große Herausforderung für den Nachweis von Nanomaterialien darstellt.
Neben dem Nachweis von anthropogenen Stoffen in der Umwelt ist zudem deren ökotoxikologische Bewertung wichtig. In der aquatischen Ökotoxikologie werden hierzu Testorganismen mit den jeweiligen Substanzen über die Wasserphase exponiert. Effektkonzentrationen (EC50) werden dabei auf Basis der Konzentrationen in der Wasserphase abgeleitet - tatsächlich bioakkumulierte Mengen werden hierbei jedoch meist nicht ermittelt; eine weitere große Herausforderung besteht zudem in der Bewertung von Mischungstoxizitäten. Gängige Testorganismen sind u.a. Kieselalgen (Diatomeen). Diatomeen stehen am Anfang der Nahrungskette - toxikologisch relevante Metalle/Nanomaterialien können sich hierüber im Nahrungsnetz der Oberflächengewässer anreichern und ggf. nachhaltig auswirken.
Im ersten Teil des Vortrages werden zunächst neue elementanalytische Methoden zum Nachweis von metallbasierten Nanopartikeln in Umweltmatrizes auf Basis der AF4/ICP-SFMS sowie stabilen Isotopenlabeln am Beispiel von Eisennanopartikeln vorgestellt.
Im zweiten Teil wird eine neue elementanalytische Methode als komplementäre Technik zur ökotoxikologischen Bewertung von (Schad-)Stoffen vorgestellt. Die neue Methode basiert auf der on-line Kopplung von HPLC mit der single-cell-ICP-(ToF)-MS (sc-ICP-(ToF)-MS) [1, 3-5]. Hierüber konnten wir erfolgreich die automatisierte Multielementanalytik einzelner Diatomeen realisieren und zur Analyse von mit Metallen inkubierten Diatomeen (cyclotella meneghiniana) einsetzen. Wir konnten zeigen, dass die sc-ICP-ToF-MS zukünftig eine leistungsstarke, komplementäre Technik in der aquatischen Ökotoxikologie zum z.B. Test von Metallen und Nanomaterialien darstellt.
Multiplexed encoding schemes of nano- and micrometer sized particles with fluorescent dyes or quantum dots (QDs) and their optical detection, are of increasing interest for applications in the life sciences, for example in flow cytometry. Almost all strategies utilizing fluorescence focus on spectrally distinguishable emission bands or colors and different intensity levels as fluorescence codes. The fluorescence parameter lifetime has been, however, barely exploited. In this work the goal is to perform multiplexing with encoding fluorophores with different fluorescence lifetimes (LTs). In comparison to the spectral multiplexing strategies this has the advantage, that the different fluorescence LT codes can be measured with the excitation and emission wavelength, thus reducing instrument costs. Moreover, LTs should not depend on emitter concentration. Unlike organic dyes, the LTs of which are typically < 10 ns, the fluorescence LTs of ternary semiconductor QDs that represent a “green” alternative to conventional Cd-containing QDs are in the range of several hundred ns, independent of oxygen concentration, and can be tuned to a certain extent by chemical composition and surface chemistry. This present a time region that can be barely covered by other emitters that have either much shorter or longer lifetimes. In this project, different encoding strategies will be assessed and the encoded particles will be then used for fluorescence assays for the analysis of several targets in parallel. Therefor the encoded particles will be functionalized with different target-specific bioligands and read out with a specifically designed flow cytometer enabling time-resolved fluorescence detection. With this instrument, the particles will be discriminated by their fluorescence LTs In one detection channel while the analytes will be quantified by fluorescence labels in a second channel in the intensity domain.
Multiplexed encoding schemes of nano- and micrometer sized polymer particles with fluorescent dyes or quantum dots (QDs) and their optical detection, are of increasing interest for applications in the life sciences, for example in flow cytometry. Almost all strategies utilizing fluorescence focus on spectrally distinguishable emission bands or colors and different intensity levels as fluorescence codes.
In this work the goal is to perform multiplexing with encoding fluorophores with different fluorescence lifetimes (LTs). In comparison to the spectral multiplexing strategies this has the advantage, that the different fluorescence LT codes can be measured with the same excitation and emission wavelength, thus reducing instrumental costs. Moreover, LTs should not depend on emitter concentration. Unlike organic dyes, the LTs of which are typically <10ns, the fluorescence LTs of ternary semiconductor QDs which represent a “green” alternative to conventional Cd-containing QDs are in the range of several hundred ns, independent of oxygen concentration, and can be tuned to a certain extent by chemical composition and surface chemistry. This presents a time region that can barely be covered by other emitters that have either much shorter or longer lifetimes. In this project, different encoding strategies will be assessed, and the encoded particles will then be used for fluorescence assays for the analysis of several targets in parallel. Therefore, the encoded particles will be functionalized with different target-specific bioligands and read out with a specifically designed flow cytometer enabling time-resolved fluorescence detection. With this instrument, the particles will be discriminated by their fluorescence LTs in one detection channel while the analytes will be quantified by fluorescence labels in a second channel in the intensity domain.
Molecular MRI is a promising in-vivo modality to detect and quantify morphological and molecular vessel-wall changes in atherosclerosis. The combination of different molecular biomarkers may improve the risk stratification of patients. This study aimed to investigate the feasibility of simultaneous visualization and quantification of plaque-burden and inflammatory activity by dual-probe molecular
MRI in a mouse-model of progressive atherosclerosis and in response-to-therapy. Homozygous apolipoprotein E knockout mice (ApoE−/−) were fed a high-fat-diet (HFD) for up to four-months prior to MRI of the brachiocephalic-artery. To assess response-to-therapy, a statin was administered for the same duration. MR imaging was performed before and after administration of an elastin-specific gadolinium-based and a macrophage-specific iron-oxide-based probe. Following in-vivo MRI, samples were analyzed using histology, immunohistochemistry, inductively-coupled-mass-spectrometry and laser-inductively-coupled-mass-spectrometry. In atherosclerotic-plaques, intraplaque expression
of elastic-fibers and inflammatory activity were not directly linked. While the elastin-specific probe demonstrated the highest accumulation in advanced atherosclerotic-plaques after four-months of HFD, the iron-oxide-based probe showed highest accumulation in early atherosclerotic-plaques after two months of HFD. In-vivo measurements for the elastin and iron-oxide-probe were in good agreement
with ex-vivo histopathology (Elastica-van-Giesson stain: y = 298.2 + 5.8, R2 = 0.83, p < 0.05; Perls‘ Prussian-blue-stain: y = 834.1 + 0.67, R2 = 0.88, p < 0.05). Contrast-to-noise-ratio (CNR) measurements of the elastin probe were in good agreement with ICP-MS (y = 0.11x-11.3, R² = 0.73, p < 0.05). Late stage atherosclerotic-plaques displayed the strongest increase in both CNR and gadolinium concentration (p < 0.05). The gadolinium probe did not affect the visualization of the iron-oxide-probe and vice versa. This study demonstrates the feasibility of simultaneous assessment of plaque-burden.
This study demonstrates the potential of the concurrent assessment of inflammatory activity and ECM degradation by dual-probe molecular MRI in an experimental mouse model of AAA. Based on the combined information from both molecular probes the rupture of AAAs could reliably be predicted, with higher accuracy compared with each probe alone. The combined in vivo quantification of these biomarkers in 1 imaging session may be useful to improve the in vivo characterization of AAAs.
Non-linear optical emitters are promising materials for energy applications and biotechnologies. Solid-state multi-band emitters like lanthanide doped up-conversion nanoparticles (UCNPs) show excellent photostability, are excitable in the near infrared (NIR), and show emission bands from the UV to SWIR spectral regions. The optical properties of these materials strongly depend on the excitation power density, i.e., the number of photons absorbed per time interval. The upconversion (ΦUC) and downshifting quantum efficiencies (ΦDS) of these materials, the excitation power dependent population, and the deactivation dynamics are influenced by nanoparticle architecture, doping concentration, and the microenvironment. We studied the fundamental changes of the luminescence properties of ß-NaYF4 UCNPs doped with Yb3+ and Er3+ depending on size, different surroundings such as aqueous and organic media, and different surface chemistries. We obtained further insights into shelling procedures, FRET optimization, influence of doping concentration, and advantages of different sensitizer ions.
During the last years Additive Manufacturing (AM) became increasingly important. That becomes clear, while looking at the advantages like a high degree of freedom concerning the geometry of the parts, low waste rates and a reduction of postprocessing, to name just three. Laser Metal Deposition (LMD) is one of those AM- methods. It can be used for different kinds of applications, e.g. repair weldings of used parts, coatings to increase the corrosion resistance or to build up new components. But for all applications, the production of defect free parts is crucial. Therefore, different kinds of non-destructive monitoring techniques were tested for the LMD-process to identify their potential to detect imperfections in-situ.