Effiziente und robuste, feature-basierte Wiedererkennung langer Zeitreihen in großen Datenbanken

Die Materialverfolgung gewinnt in der Metallindustrie immer mehr an Bedeutung:rnEs ist notwendig, dass ein Metallband im Fertigungsprozess ein festgelegtes Programm durchläuft - erst dann ist die Qualität des Endprodukts garantiert. Die bisherige Praxis besteht darin, jedem Metallband eine Nummer zuzuordnen, mit der dieses Band beschriftet wird. Bei einer tagelangen Lagerung der Bänder zwischen zwei Produktionsschritten erweist sich diese Methode als fehleranfällig: Die Beschriftungen können z.B. verloren gehen, verwechselt, falsch ausgelesen oder unleserlich werden. 2007 meldete die iba AG das Patent zur Identifikation der Metallbänder anhand ihres Dickenprofils an (Anhaus [3]) - damit kann die Identität des Metallbandes zweifelsfrei nachgewiesen werden, eine zuverlässige Materialverfolgung wurde möglich.Es stellte sich jedoch heraus, dass die messfehlerbehafteten Dickenprofile, die als lange Zeitreihen aufgefasst werden können, mit Hilfe von bisherigen Verfahren (z.B. L2-Abstandsminimierung oder Dynamic Time Warping) nicht erfolgreich verglichen werden können.Diese Arbeit stellt einen effizienten feature-basierten Algorithmus zum Vergleichrnzweier Zeitreihen vor. Er ist sowohl robust gegenüber Rauschen und Messausfällen als auch invariant gegenüber solchen Koordinatentransformationen der Zeitreihen wie Skalierung und Translation. Des Weiteren sind auch Vergleiche mit Teilzeitreihen möglich. Unser Framework zeichnet sich sowohl durch seine hohe Genauigkeit als auch durch seine hohe Geschwindigkeit aus: Mehr als 99.5% der Anfragen an unsere aus realen Profilen bestehende Testdatenbank werden richtig beantwortet. Mit mehreren hundert Zeitreihen-Vergleichen pro Sekunde ist es etwa um den Faktor 10 schneller als die auf dem Gebiet der Zeitreihenanalyse etablierten Verfahren, die jedoch nicht im Stande sind, mehr als 90% der Anfragen korrekt zu verarbeiten. Der Algorithmus hat sich als industrietauglich erwiesen. Die iba AG setzt ihn in einem weltweit einzigartigen dickenprofilbasierten Überwachungssystemrnzur Materialverfolgung ein, das in ersten Stahl- und Aluminiumwalzwerkenrnbereits erfolgreich zum Einsatz kommt.

Interactions of gold nanoparticles with polymeric membranes

This thesis focuses on the interactions of nanoparticles with artificial membranes. The synthesis of the block copolymer poly(dimethylsiloxane)-block-poly(2-methyloxazoline) (PDMS-b-PMOXA) is described, as well as the formation of polymersomes in water. These polymersomes act as minimal cell models, consisting of an artificial bilayer membrane only, allowing the study of the interactions between nanoparticles and polymeric membranes. Both spherical and rod-shaped gold nanoparticles (AuNPs) were used in this study and they were characterized using light scattering (PCS), transmission electron microscopy (TEM), UV/Vis spectroscopy, and polarization anisotropy measurements. The polymer grafting on the spherical cores is asymmetric (shell asphericity) but is parallel to the inherent, due to polycrystallinity, core anisotropy, resulting in a characteristic scattering of the AuNPs in PCS.rnInteractions of polymersomes and AuNPs were investigated by PCS, cryo-TEM and UV/Vis. Three possible scenarios upon mixing of polymersomes and AuNPs can be distinguished by using only PCS: (i) no interactions between particles and vesicles, (ii) attachment of the particles to the outer side of the vesicles (decoration), and (iii) uptake of particles into the vesicles. It is shown that all three scenarios are possible, solely depending on the particle’s surface functionalization. In addition, it was revealed that the AuNPs need to be attached to the inner side of the membrane instead of diffusing freely within the vesicle. The present experimental findings essentially help with the understanding of the interactions of nanoparticles with membranes and show that the process of endocytosis can be attributed to physical processes only. rn

Structural characterization of intermediate and metastable phases by electron microscopy

Structure characterization of nanocrystalline intermediates and metastable phases is of primary importance for a deep understanding of synthetic processes undergoing solid-to-solid state phase transitions. Understanding the evolution from the first nucleation stage to the final synthetic product supports not only the optimization of existing processes, but might assist in tailoring new synthetic paths. A systematic investigation of intermediates and metastable phases is hampered because it is impossible to produce large crystals and only in few cases a pure synthetic product can be obtained. Structure investigation by X-ray powder diffraction methods is still challenging on nanoscale, especially when the sample is polyphasic. Electron diffraction has the advantage to collect data from single nanoscopic crystals, but is limited by data incompleteness, dynamical effects and fast deterioration of the sample under the electron beam. Automated diffraction tomography (ADT), a recently developed technique, making possible to collect more complete three-dimensional electron diffraction data and to reduce at the same time dynamical scattering and beam damage, thus allowing to investigate even beam sensitive materials (f.e. hydrated phases and organics). At present, ADT is the only technique able to deliver complete three-dimensional structural information from single nanoscopic grains, independently from other surrounding phases. Thus, ADT is an ideal technique for the study of on-going processes where different phases exist at the same time and undergo several structural transitions. In this study ADT was used as the main technique for structural characterization for three different systems and combined subsequently with other techniques, among which high-resolution transmission electron microscopy (HRTEM), cryo-TEM imaging, X-ray powder diffraction (XRPD) and energy disperse X-ray spectroscopy (EDX).rnAs possible laser host materials, i.e. materials with a broad band emission in the near-infrared region, two unknown phases were investigated in the ternary oxide system M2O-Al2O3-WO3 (M = K, Na). Both phases exhibit low purity as well as non-homogeneous size distribution and particle morphology. The structures solved by ADT are also affected by pseudo-symmetry. rnSodium titanate nanotubes and nanowires are both intermediate products in the synthesis of TiO2 nanorods which are used as additives to colloidal TiO2 film for improving efficiency of dye-sensitized solar cells (DSSC). The structural transition from nantubes to nanowires was investigated in a step by step time-resolved study. Nanowires were discovered to consist of a hitherto unknown phase of sodium titanate. This new phase, typically affected by pervasive defects like mutual layer shift, was structurally determined ab-initio on the basis of ADT data. rnThe third system is related with calcium carbonate nucleation and early crystallization. The first part of this study is dedicated to the extensive investigations of calcium carbonate formation in a step by step analysis, up to the appearance of crystalline individua. The second part is dedicated to the structure determination by ADT of the first-to-form anhydrated phase of CaCO3: vaterite. An exhaustive structure analysis of vaterite had previously been hampered by diffuse scattering, extra periodicities and fast deterioration of the material under electron irradiation. rn

Three-dimensional electron microscopy of myriapod hemocyanin, planorbid snail acetylcholine-binding protein and cyanobacterial Vipp1

Three-dimensional electron microscopy (3-D EM) provides a framework for the analysis of large protein quaternary structures. The advantage over the generally higher resolving meth- od of X-ray crystallography is the embedding of the proteins in their physiological environ- ment. However, results of the two methods can be combined to obtain superior structural information. In this work, three different protein types – (i) Myriapod hemocyanin, (ii) vesi- cle-inducing protein in plastids 1 (Vipp1) and (iii) acetylcholine-binding protein (AChBP) – were structurally analyzed by 2-D and 3-D EM and, where possible, functionally interpreted.rnMyriapod hemocyanins have been previously shown to be 6x6-meric assemblies that, in case of Scutigera coleoptrata hemocyanin (ScoHc), show two 3x6-mer planes whith a stag- gering angle of approximately 60°. Here, previously observed structural differences between oxy- and deoxy-ScoHc could be substantiated. A 4° rotation between hexamers of two dif- ferent 3x6-mer planes was measured, which originates at the most central inter-hexamer in- terface. Further information about allosteric behaviour in myriapod hemocyanin was gained by analyzing Polydesmus angustus hemocyanin (PanHc), which shows a stable 3x6-mer and divergent histidine patterns in the inter-hexamer interfaces when compared to ScoHc. Both findings would conclusively explain the very different oxygen binding properties of chilopod and diplopod hemocyanin.rnVipp1 is a protein found in cyanobacteria and higher plants which is essential for thyla- koid membrane function and forms highly variable ring-shaped structures. In the course of this study, the first 3-D analysis of Vipp1 was conducted and yielded reconstructions of six differently sized Vipp1 rings from negatively stained images at resolutions between 20 to 30 Å. Furthermore, mutational analyses identified specific N-terminal amino acids that are essential for ring formation. On the basis of these analyses and previously published results, a hypothetical model of the Vipp1 tertiary and quaternary structure was generated.rnAChBP is a water-soluble protein in the hemolymph of mollusks. It is a structural and functional homologue of the ligand-binding domain of nicotinic acetylcholine receptors. For the freshwater snail Biomphalaria glabrata, we previously described two types of AChBP (BgAChBP1 and BgAChBP2). In this work, a 6 Å 3-D reconstruction of native BgAChBP is presented, which shows a dodecahedral assembly that is unprecedented for an AChBP. Single particle analysis of recombinantely expressed BgAChBP types led to preliminary results show- ing a dodecahedral assembly of BgAChBP1 and a dipentameric assembly of BgAChBP2. This indicates divergent biological functions of the two types.