NanoSIMS-Analyse und hochauflösende Elektronenmikroskopie an präsolaren Silikaten aus roten Riesensternen und Supernovaexplosionen

This thesis deals with the analysis of “presolar” silicates and oxides by high resolution mass spectrometry and electron microscopy techniques. This “stardust” was identified by its extreme oxygen isotopic anomalies, which point to nucleosynthetic reactions in stellar interiors, in the carbonaceous chondrite Acfer 094. Isotopic, chemical and mineralogical studies on these stardust grains therefore allow the testing of astrophysical questions on Earth, which are otherwise only accessible by spectroscopy and theoretical models. The class of presolar silicates has been identified only six years ago in 2002, although it was known already from spectroscopic observations that silicates represent the most abundant type of dust in the galaxy. The development of the “NanoSIMS” was a crucial step in this respect, because this ion probe with its superior spatial resolution of only 50 nm allowed the detection of the typically 300 nm sized presolar silicates. A total of 142 presolar silicates and 20 presolar oxides were identified within Acfer 094, whose matrix therefore contains 163 ± 14 ppm presolar silicates and 26 ± 6 ppm presolar oxides. This is among the highest amounts reported so far for any primitive solar system material. The majority of detected stardust grains derive from asymptotic giant branch stars of 1 – 2.5 Msun and close-to-solar or slightly lower-than-solar metallicity. However, by measuring the Si isotopic compositions of some enigmatic grains, it could be shown that there is a sub-class of presolar silicates characterized by an extreme enrichment of 17O and a moderate enhancement of 30Si relative to solar, whose origins might be explained by formation in binary stellar systems. About 10% of all grains exhibit an enrichment in 18O and some of them also of 28Si relative to solar, which most likely point to an origin in type II supernova explosions. The Si isotopic measurements also allowed to quantify the effect of the s-process on the Si isotopes in low-mass asymptotic giant branch stars. The results agree well with theoretical predictions. The grains were furthermore characterized by SEM and the chemistries of about half of the grains were determined by Auger electron spectroscopy. The majority of grain morphologies are consistent with what is expected from condensation experiments. However, a lot of grains are altered by Fe-rich minerals, which are either of primary condensation or of secondary ISM or solar nebula origin. Furthermore, complex presolar grains consisting of refractory Al-rich grains attached to silicate material could be identified, which have been predicted by condensation theory and observational evidence. Nine presolar silicates were analyzed by combined NanoSIMS/TEM studies. The majority of grains are Mg-rich and amorphous, which is in contrast to astrophysical evidence, which mainly postulate crystalline Mg-rich and amorphous Fe-rich circumstellar condensates. However, the grains might have been rendered amorphous by secondary processes in the ISM or could have condensed under non-equilibrium, low-temperature conditions in the circumstellar outflow. The grains are more likely characterized by a variable, pyroxene-like chemistry, which could be a result of sputtering in the ISM, which preferentially removes Mg. The detected crystalline presolar silicates in this study and in other work are all olivines, whereas grains with a pyroxene stoichiometry are all amorphous except one. This supports astrophysical models which point to different formation pathways for these two types of grains and therefore different crystallinity. However, the relatively high Fe content of three detected presolar olivines in this study and in other work is in contrast to astrophysical evidence and theoretical considerations, which predict essentially Fe-free crystalline grains. It is therefore possible that the infrared spectra might also be compatible with less Mg-rich olivines. The only crystalline presolar silicate with a pyroxene-like stoichiometry is the unusual grain 1_07: although it is chemically enstatite, the electron diffraction pattern could only be indexed to silicate perovskite, which is stable above ~23 GPa. The discovery of a high-pressure phase of presolar origin shows that dust grains encountering interstellar shocks might not necessarily be completely destroyed. In astrophysical models it is in principle also possible that a fraction of larger grains might survive such a shock wave encounter as a high-pressure modification, which is supported by this discovery.Diese Arbeit beschäftigt sich mit der Analyse „präsolarer“ Silikat- und Oxidkörner mit Hilfe hochauflösender Massenspektrometrie- und Elektronenmikroskopie-Techniken. Dieser „Sternenstaub“ wurde anhand seiner extremen Isotopenanomalien in Sauerstoff, die auf nukleosynthetische Reaktionen im Innern von Sternen hindeuten, in dem kohligen Chondriten Acfer 094 lokalisiert. Isotopische, chemische und mineralogische Studien an diesem Staub erlauben die Überprüfung astrophysikalischer Fragestellungen auf der Erde, die ansonsten nur über Spektroskopie oder theoretische Modelle zugänglich sind. Die Klasse der präsolaren Silikate ist dabei erst 2002 entdeckt worden, obwohl man über spektroskopische Untersuchungen wusste, dass es sich bei Silikaten um die häufigste Staubart in der Galaxie handelt. Die Entwicklung der „NanoSIMS“ war dabei ein entscheidender Schritt, denn mit diesem Sekundärionen-Massenspektrometer konnte man erstmals mit einer Ortsauflösung von bis zu 50 nm die typischerweise nur etwa 300 nm großen präsolaren Silikatkörner aufspüren. Insgesamt wurden 142 präsolare Silikate und 20 präsolare Oxide in Acfer 094 detektiert, dessen Matrix damit 163 ± 14 ppm präsolare Silikate und 26 ± 6 ppm präsolare Oxide enthält. Diese Werte sind verglichen mit anderen Meteoriten sehr hoch, und folglich repräsentiert Acfer 094 eine der ursprünglichsten Proben, die zur Erforschung des frühen Sonnensystems zur Verfügung stehen. Der Großteil der gefundenen Körner stammt aus roten Riesensternen mit etwa 1 bis 2.5 Sonnenmassen und solarer oder sub-solarer Metallizität. Die Messung der Silizium-Isotopie einiger Silikate zweifelhafter Herkunft hat gezeigt, dass ein Teil der Körner extrem in 17O und moderat in 30Si angereichert ist, was durch den Ursprung in einem Binär-Sternsystem erklärt werden könnte. Ein weiterer Teil 18O-angereicherter Silikate (etwa 10%) zeigt einen Überschuss an 28Si, was auf den Ursprung in Supernovae hindeutet. Durch die Messung der Silizium-Isotopie einer großen Anzahl präsolarer Silikate konnte außerdem der Einfluss des s-Prozess auf die Siliziumisotope in roten Riesensternen geringer Masse quantifiziert werden. Die Resultate in dieser Arbeit stimmen gut mit theoretischen Vorhersagen überein. Weiterhin wurden die präsolaren Silikate im SEM charakterisiert und von fast der Hälfte die Chemie durch Augerelektronen-Spektroskopie bestimmt. Der Großteil der Morphologien stimmt mit den Erwartungen aus Kondensationsexperimenten überein. Viele Körner sind jedoch durch Eisenminerale verändert, die entweder mit den präsolaren Körnern zusammen primär kondensiert sind, oder durch sekundäre Prozesse im ISM oder im solaren Nebel implantiert wurden. Weiterhin konnten zum ersten Mal komplexe präsolare Silikate bestehend aus Al-reichen Oxiden und silikatischem Material nachgewiesen werden, die von theoretischen Kondensationsberechnungen und aufgrund astronomischer Beobachtungen vorhergesagt werden. Neun präsolare Silikate wurden neben der NanoSIMS mit TEM untersucht. Der Großteil dieser Körner ist Mg-reich und amorph, was mit den Modellen nicht übereinstimmt, welche kristalline Mg-reiche und amorphe Fe-reiche Silikate postulieren. Die Körner könnten jedoch im ISM sekundär amorphisiert worden sein oder unter Nicht-Gleichgewichtsbedingungen in der Sternatmosphäre kondensiert sein. Chemisch kennzeichnet die Silikate eher eine variable, pyroxen-ähnliche Chemie, was ebenfalls ein Effekt der Amorphisierung sein könnte, denn beim „Sputtering“ im ISM wird bevorzugt Mg in die Gasphase überführt. Weiterhin überwiegt in den bisherigen TEM-Arbeiten und in dieser Arbeit der Anteil der kristallinen Olivine, während Körner mit Pyroxen-Zusammensetzung bis auf eine Ausnahme amorph sind. Dies unterstützt astrophysikalische Modelle, die auf verschiedene Formationswege dieser beiden Minerale hindeuten und somit auf verschiedene Kristallinität. Weiterhin wurde ein präsolarer Fe-haltiger Olivin gefunden, was mit zwei anderen TEM-Arbeiten an präsolaren Silikaten übereinstimmt, von Theorien und anhand astronomischer Beobachtungen jedoch nicht vorhergesagt wird. Die Infrarotspektren könnten demnach eventuell auch mit weniger refraktären kristallinen Silikaten interpretiert werden. Das einzige, bisher gefundene kristalline präsolare Silikat mit pyroxen-artiger Chemie ist das Korn 1_07: Obwohl chemisch Enstatit, konnte das erzeugte Beugungsmuster im TEM nur Silikat-Perowskit zugeordnet werden, das erst ab ~23 GPa stabil ist. Die Entdeckung eines Hochdruck-Minerals präsolaren Ursprungs zeigt, dass Staubkörner im ISM nicht unbedingt komplett zerstört werden. In den theoretischen Modellen ist es prinzipiell auch möglich, dass ein Bruchteil größerer Körner eine solche Konfrontation als Hochdruck-Modifikation überlebt, was die Entdeckung dieses Korns unterstreicht

Kosmischer Staub im Nano-Labor : ein Blick in die Kinderstube des Sonnensystems

Staubwolken sind im Universum die Geburtsstätten neuer Sterne. Dort wiederholen sich Prozesse, die vor 4,56 Milliarden Jahren auch zur Entstehung unseres Sonnensystems geführt haben. Noch heute gibt es Zeugen aus dieser Zeit: Kometenstaub, Sternenstaub und interstellarer Staub. Die »Stardust-Mission« hat sie eingefangen, und Frankfurter Geowissenschaftler haben darin – dank modernster Labor-Analytik – erstaunliche Funde gemacht

Advancement and application of sparse coding approaches for the analysis of arm movement trajectories

Eine von vielen Modalitäten zur Vermittlung von Information in Interaktion zwischen Mensch und Maschine ist die Gestik. Mit Hilfe dynamischer Gesten können sowohl Begriffe, als auch Emotionen kommuniziert werden. In dieser Arbeit wird der zeitliche Verlauf der Position einer Gliedmaße bei Ausführung der Geste, die sogenannte Bewegungstrajektorie, betrachtet. Damit eine Maschine Gesten wahrnehmen kann, müssen die Trajektorien mittels Sensoren aufgenommen werden und anschließend durch eine entsprechende Verarbeitung der Daten interpretiert werden. Dabei kommt ein mehrstufiger Mustererkennungsprozess zum Einsatz. Ein Schritt in diesem Prozess ist die Merkmalsextraktion, welche das aufgenommene Signal in einer kompakten Form darstellt. Diese Arbeit widmet sich einer Untersuchung zur Anwendung von Sparse Coding in der Merkmalsextraktion für Bewegungstrajektorien. Sparse Coding kann eine Datenmenge durch eine beschränkte Menge repräsentativer, wiederkehrender Merkmale darstellen. Diese Merkmale werden in einer Lernphase aus Trainingsdaten gelernt und in der Kannphase in einem unbekannten Signal detektiert. Dieses Konzept hat gegenüber konventionellen Methoden zur Merkmalsextraktion in zeitlichen Signalen den Vorteil, dass die Merkmale optimal an die Daten angepasst sind und so die charakteristischen Eigenschaften der Trainingsdaten beschreiben. In dieser Arbeit wird das Verfahren für die Anwendung auf Bewegungstrajektorien optimiert. Es wird untersucht, unter welchen Rahmenbedingungen Sparse Coding für Bewegungstrajektorien anwendbar ist und wie die aufgenommenen Daten vorverarbeitet werden müssen. Des Weiteren werden die Auswirkungen des Verfahrens auf nachgelagerte Verarbeitungsschritte im Mustererkennungsprozess, wie die Klassifikation und die Generierung von Bewegungstrajektorien, betrachtet. Die Leistungsfähigkeit des Verfahrens beim Einsatz in der Gestenerkennung wird in Experimenten anhand eines, im Rahmen dieser Arbeit selbst erstellten, Datensatzes demonstriert. Um die Generalisierbarkeit des Verfahrens auf andere Anwendungsdomänen zu untersuchen, wird es auf Benchmark-Datensätze aus den Bereichen der Activity Recognition und der Handschrifterkennung angewendet. Des Weiteren wird eine echtzeitfähige Implementierung des Verfahrens in einer Demonstrator-Applikation vorgestellt.One modality for the transmission of information during interaction between a human and a machine is gesticulation, by which concepts and emotions can be communicated. In this work, the temporal evolution of the position of one limb during the performance of the gesture, the so called movement trajectory, is analyzed. For a machine to be able to perceive a gesture, those trajectories must be recorded via sensors, and the data must be interpreted by means of a suitable data processing mechanism. This data processing is usually implemented by a pattern recognition pipeline, consisting of multiple processing steps. One of those steps is the feature extraction, the purpose of which is to represent the incoming data in a compact form. In this work, the applicability of Sparse Coding as a feature extraction step in the pattern recognition pipeline is investigated. The main motivation for this research is the ability of Sparse Coding to represent a dataset with a minimal set of representative and recurring features. Those features are learnt in a learning phase and are detected in an unknown signal in the application phase. Compared to conventional methods for feature extraction in temporal signals, this approach has the advantage that the features are adapted to the domain specific data and can thus capture optimally the characteristics of the training data. In this work, the a general Sparse Coding approach is adapted for the application to movement trajectories. It is investigated, under which preconditions Sparse Coding is applicable to movement trajectories, and how the data must be pre-processed. Further, the effects of the application of the approach for down-stream processing steps, like classification and generation of movement trajectories are examined. Particularly for classification, there are interesting advantages arising from the way Sparse Coding is representing the data. The feasibility of the approach for processing movement trajectories is demonstrated in experiments on a gesture dataset that has been recorded as part of this work. To show the generalizability of the approach to other application domains, it is applied to benchmark dataset from the fields of activity recognition and handwriting recognition. Further a real-time capable implementation of the approach in form of a demonstrator application is described

NanoSIMS analysis and high resolution electron microscopy of silicate stardust grains from red giant stars and supernova explosions

This thesis deals with the analysis of presolar silicates and oxides by high resolution mass spectrometry and electron microscopy techniques. This stardust was identified by its extreme oxygen isotopic anomalies, which point to nucleosynthetic reactions in stellar interiors, in the carbonaceous chondrite Acfer 094. Isotopic, chemical and mineralogical studies on these stardust grains therefore allow the testing of astrophysical questions on Earth, which are otherwise only accessible by spectroscopy and theoretical models. The class of presolar silicates has been identified only six years ago in 2002, although it was known already from spectroscopic observations that silicates represent the most abundant type of dust in the galaxy. The development of the NanoSIMS was a crucial step in this respect, because this ion probe with its superior spatial resolution of only 50 nm allowed the detection of the typically 300 nm sized presolar silicates. A total of 142 presolar silicates and 20 presolar oxides were identified within Acfer 094, whose matrix therefore contains 163 ± 14 ppm presolar silicates and 26 ± 6 ppm presolar oxides. This is among the highest amounts reported so far for any primitive solar system material. The majority of detected stardust grains derive from asymptotic giant branch stars of 1 2.5 Msun and close-to-solar or slightly lower-than-solar metallicity. However, by measuring the Si isotopic compositions of some enigmatic grains, it could be shown that there is a sub-class of presolar silicates characterized by an extreme enrichment of 17O and a moderate enhancement of 30Si relative to solar, whose origins might be explained by formation in binary stellar systems ...thesi

Separation of Heavy Rare-Earth Elements from Light Rare-Earth Elements Via Solvent Extraction from a Neodymium Magnet Leachate and the Effects of Diluents

In recent decades, rare-earth elements (REEs) have seen a considerable increase in usage in modern technologies and the so-called green energy sources. The REEs are currently regarded to be among the most critical elements by the European Union (EU) and the United States (USA). Large investments are made in the research of recycling of the REEs from end-of-life products and E-scrap. One potential source for recycling of larger amounts of neodymium and dysprosium are end-of-life neodymium magnets. In this work, the selective extraction of REEs from a sulfuric media leachate (containing Nd, Dy, Pr, Gd, Co, and B) obtained by selective roasting of NdFeB waste and leaching was investigated. The extracting agent D2EHPA (di-(2-ethylhexyl) phosphoric acid) diluted in Solvent 70, hexane, octane, cyclohexanone, chloroform, 1-octanol, and toluene was used for the investigation of the effects of using different diluents on the extraction of REEs and the separation between the light and the heavy REEs. The concentrations of D2EHPA in the used diluents were 0.3, 0.6, 0.9, and 1.2 M. The highest separation factors between the heavy and the light REEs were achieved using 0.3 M D2EHPA in hexane, while no B or Co extraction was measurable. The REEs were completely extracted as a group using 0.9 M or 1.2 M D2EHPA in either octane or hexane, also with no B or Co extraction. The aliphatic nonpolar diluents showed better properties than the aromatic and polar ones. The complete stripping of REEs from the loaded organic phases was proven to be efficient using hydrochloric acid at concentrations of 2 M or higher

Characterization and Leaching of Neodymium Magnet Waste and Solvent Extraction of the Rare-Earth Elements Using TODGA

The rare-earth elements (REEs) are considered as some of the most critical elements in the EU and the USA today. E-scrap, such as end-of-life neodymium magnets, could be a viable secondary source for the recovery of these elements. Neodymium magnets (NdFeB) consist of considerable amounts of Nd, Dy, Pr, and some other REEs, depending on the specific application. Apart from REEs, neodymium magnets are made up of around 60% iron, which can pose a challenge in their recycling. For example, iron can be dissolved along with other elements during leaching or co-extracted during solvent extraction. In this work, extraction of REEs with TODGA (tetraoctyl-diglycolamide) from a real leachate, obtained by neodymium magnet powder dissolution in nitric acid, was studied. The goal was to selectively extract the REEs from other elements in the solution. TODGA was used as the extracting agent due to its selective extraction properties for REEs and other f-block elements. The influence of the diluent on the overall extraction and the selectivity of the extraction was studied in order to determine application feasibility of future processes. To this end, experiments using Solvent 70 (hydrocarbons C11-C14, ae 0.5 wt% aromatics), hexane, toluene, cyclohexanone and 1-octanol as the diluents were performed. TODGA has shown good selectivity between REEs and other elements in solution under almost all conditions, reaching the highest distribution ratios of REEs in the aliphatic diluents, while the distribution ratios of other non-REEs reach a mere value of 0.1. An exception was cyclohexanone, which has the ability to extract small amounts of ions itself. The highest separation factors between Dy and the light REEs (Nd and Pr) were observed with a 0.01 M solution of TODGA in Solvent 70. REEs, as group, were extracted with 0.1 M solutions of TODGA in all diluents except for cyclohexanone, which led to extraction of Al and B at amounts greater than 10%. Stripping with over 98% efficiency was achieved using MQ water in one step

Cloudy operating systems

This article discusses the notion of cloud operating systems, the operation of the cloud system and the specifics of its use. Types of cloud operating systems, as well as advantages and disadvantages of using cloud operating systems

Correlation of EGFR expression, gene copy number and clinicopathological status in NSCLC

Background: Epidermal Growth Factor Receptor (EGFR) targeting therapies are currently of great relevance for the treatment of lung cancer. For this reason, in addition to mutational analysis immunohistochemistry (IHC) of EGFR in lung cancer has been discussed for the decision making of according therapeutic strategies. The aim of this study was to obtain standardization of EGFR-expression methods for the selection of patients who might benefit of EGFR targeting therapies. Methods: As a starting point of a broad investigation, aimed at elucidating the expression of EGFR on different biological levels, four EGFR specific antibodies were analyzed concerning potential differences in expression levels by Immunohistochemistry (IHC) and correlated with fluorescence in situ hybridization (FISH) analysis and clinicopathological data. 206 tumor tissues were analyzed in a tissue microarray format employing immunohistochemistry with four different antibodies including Dako PharmDx kit (clone 2-18C9), clone 31G7, clone 2.1E1 and clone SP84 using three different scoring methods. Protein expression was compared to FISH utilizing two different probes. Results: EGFR protein expression determined by IHC with Dako PharmDx kit, clone 31G7 and clone 2.1E1 (≤ 0.05) correlated significantly with both FISH probes independently of the three scoring methods; best correlation is shown for 31G7 using the scoring method that defined EGFR positivity when ≥ 10% of the tumor cells show membranous staining of moderate and severe intensity (p = 0.001). Conclusion: Overall, our data show differences in EGFR expression determined by IHC, due to the applied antibody. Highest concordance with FISH is shown for antibody clone 31G7, evaluated with score B (p = 0.001). On this account, this antibody clone might by utilized for standard evaluation of EGFR expression by IHC

Numerical Investigations of Mixed Convection of Incompressible Viscous Fluid in LNG Storage with a Various Locations of Input and Output Mass

The article shows the results of mathematical simulation of mixed convection in the low-temperature storage of liquefied natural gas with a regenerative cooling. The regimes of mixed convection in a closed area with the different arrangement of the input and output sections of the masses are investigated. Two-dimensional nonstationary problem in the model of the Navier-Stokes in dimensionless variables "vorticity - stream function - temperature" was examined. Are obtained distributions of the hydrodynamic parameters and temperatures, characteristic basic laws governing the processes being investigated. Detailed circulating currents and carried out analysis of the mechanism of vortices formation and the temperature distribution in the solution for mixed convection mode with low Reynolds and Grashof numbers (Gr=10{6}, 100<Re<1000). Is established the significant influence of the geometrical arrangement of the input and output mass sections and input stream velocity on the structure of liquid flow and temperature in the low temperature LNG storage tanks