Charakterisierung antiker Keramik und ihrer Herstellungstechniken mit mineralogischen Methoden am Beispiel Mayener Gebrauchskeramik

Mehr als hundert Jahre archäologischer Forschung haben gezeigt, dass in Mayen in römischer und mittelalterlicher Zeit eines der wichtigsten europäischen Produktionszentren für die Herstellung qualitätsvoller Gebrauchskeramik bestand. Im Rahmen dieser Studie wurden vier Befundkomplexe aus Töpfereisiedlungen vom 4. bis in das 14. Jahrhundert untersucht. Genauer handelt es sich um Keramik aus zwei spätantiken Brennanlagen des 4. Jahrhunderts im Bereich der Flur „Auf der Eich“ an den Straßen „Am Sonnenhang“ und „Frankenstraße“. Weiterhin konnte Material aus zwei Töpferofenfüllungen des 5. bis 9. Jahrhunderts analysiert werden, das 1975 auf dem Grundstück 55 an der „Siegfriedstraße“ in Brennanlagen entdeckt wurde. Hinzu kam Brenngut aus elf Töpferöfen des späten 8. bis 14. Jahrhunderts, welches in den so genannten „Burggärten“ der Genovevaburg von Mayen in den Jahren 1986/87 durch die archäologische Denkmalpflege in Koblenz geborgen wurde. Die mineralogischen Untersuchungen zur Charakterisierung der „Mayener Keramik“ wurden systematisch an den Keramikmaterialien aus diesen Fundstellen durchgeführt. Mittelalterliche Keramik aus Bornheim-Walberberg, Brühl-Eckdorf, Höhr-Grenzhausen, Langerwehe, Frechen, Brühl-Pingsdorf, Paffrath, Raeren, Ratingen-Breitscheid, Siegburg-Seehofstraße, Siegburg-Scherbenhügel, Fredelsloh und Brühl-Badorf konnte für diese Arbeit als Referenzmaterialien ebenfalls untersucht werden. Provenienzanalysen wurden an Keramikproben aus 27 Fundorten, die makroskopisch nach Mayener Ware aussehen, mit mineralogischen Methoden durchgeführt, um sie der Fundregion Mayen eindeutig zuordnen zu können.rnPhasenanalyse, chemische Analyse und thermische Analyse wurden an Keramik sowie Ton durchgeführt. Die Phasenanalyse wurde zur Bestimmung der mineralischen Zusammensetzung von Grundmasse und Magerungsmittel (Röntgendiffraktometrie (XRD), Polarisationsmikroskop, Mikro-Raman-Spektroskopie) verwendet. Die chemische Zusammensetzung wurde durch Röntgenfluoreszenzanalyse (RFA) ermittelt. Elektronenstrahlmikroanalyse (ESMA) und Laser-Massenspektrometrie mit induktiv gekoppeltem Plasma (LA-ICP-MS) wurden bei den Proben, bei denen weniger als 2g Material zur Verfügung standen, eingesetzt. Brennexperimente wurden am originalen Rohstoff der Keramik aus den „Burggärten“ der Genovevaburg durchgeführt. Gebrannter Ton wurde durch Röntgendiffraktometrie (XRD), Infrarotspektroskopie (IR) und Differential-Thermoanalyse (DTA) analysiert. rnAnhand der Messergebnisse lässt sich die Mayener Keramik aus den vier Fundplätzen in zwei Typen zusammenzufassen: der mit Feldspat-reichem Sand gemagerte römische Typ und der mit Quarz-reichem Sand gemagerte mittelalterliche Typ. Die Änderung des Magerungsmittels von Feldspat- zu Quarzsand weist eine technische Entwicklung zu höheren Brenntemperaturen von der Römerzeit bis in das Mittelalter nach. Nach der Untersuchung und dem Vergleich mit den Referenzkeramikgruppen ist festzustellen, dass durch multivariate Statistikanalysen der chemischen Komponenten die Charakterisierung der Keramik und eine Differenzierung zwischen den Keramikgruppen gelingt. Diese Erkenntnisse bildeten die Basis für Provenienzanalysen. 16 Fundorte können durch Provenienzanalyse sicher als Exportregionen der Mayener Ware festgestellt werden. Gemäß den Brennexperimenten lassen sich die chemischen Reaktionen während des Brandprozesses nachvollziehen. Zwei Methoden wurden mittels Röntgendiffraktometrie (XRD) und Differential-Thermoanalyse (DTA) zur Bestimmung der Brenntemperaturen der Keramik modelliert. Die Töpferöfen der „Burggärten“ können nach der Brenntemperatur in zwei Typen zusammengefasst werden: solche mit einer Brenntemperatur unter 1050°C und solche mit einer Brenntemperatur über 1050°C.rn

Internal characteristics, chemical compounds and spectroscopy of sapphire as single crystals

In this study more than 450 natural sapphire samples (most of basaltic type) collected from 19 different areas were examined. They are from Dak Nong, Dak Lak, Quy Chau, two unknown sources from the north (Vietnam); Bo Ploi, Khao Ploi Waen (Thailand); Ban Huay Sai (Laos); Australia; Shandong (China); Andapa, Antsirabe, Nosibe (Madagascar); Ballapana (Sri Lanka); Brazil; Russia; Colombia; Tansania and Malawi. rnThe samples were studied on internal characteristics, chemical compositions, Raman-, luminescence-, Fourier transform infrared (FTIR)-, and ultraviolet-visible-near infrared (UV-Vis-NIR)- spectroscopy. The internal features of these sapphire samples were observed and identified by gemological microscope, con focal micro Raman and FTIR spectroscopy. The major and minor elements of the samples were determined by electron probe microanalysis (EPMA) and the trace elements by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). rnThe structural spectra of sapphire were investigated by con focal Raman spectroscopy. The FTIR spectroscopy was used to study the vibration modes of OH-groups and also to determine hydrous mineral inclusions in sapphire. The UV-Vis-NIR absorption spectroscopy was used to analyze the cause of sapphire color. rnNatural sapphires contain many types of mineral inclusions. Typically, they are iron-containing inclusions like goethite, ilmenite, hematite, magnetite or silicate minerals commonly feldspar, and often observed in sapphires from Asia countries, like Dak Nong, Dak Lak in the south of Vietnam, Ban Huay Sai (Laos), Khao Ploi Waen and Bo Ploi (Thailand) or Shandong (China). Meanwhile, CO2-diaspore inclusions are normally found in sapphires from Tansania, Colombia, or the north of Vietnam like Quy Chau. rnIron is the most dominant element in sapphire, up to 1.95 wt.% Fe2O3 measured by EPMA and it affects spectral characteristics of sapphire.rnThe Raman spectra of sapphire contain seven peaks (2A1g + 5Eg). Two peaks at about 418.3 cm-1 and 577.7 cm-1 are influenced by high iron content. These two peaks shift towards smaller wavenumbers corresponding to increasing iron content. This shift is showed by two equations y(418.3)=418.29-0.53x andy(577.7)=577.96-0.75x, in which y is peak position (cm-1) and x is Fe2O3 content (wt.%). By exploiting two these equations one can estimate the Fe2O3 contents of sapphire or corundum by identifying the respective Raman peak positions. Determining the Fe2O3 content in sapphire can help to distinguish sapphires from different origins, e.g. magmatic and metamorphic sapphire. rnThe luminescence of sapphire is characterized by two R-lines: R1 at about 694 nm and R2 at about 692 nm. This characteristic is also influenced by high iron content. The peak positions of two R-lines shift towards to smaller wavelengths corresponding to increasing of iron content. This correlation is showed by two equations y(R_2 )=692.86-0.049x and y(R_1 )=694.29-0.047x, in which y is peak position (nm) of respective R-lines and x is Fe2O3 content (wt.%). Two these equations can be applied to estimate the Fe2O3 content of sapphire and help to separate sapphires from different origins. The luminescence is also applied for determination of the remnant pressure or stress around inclusions in Cr3+-containing corundum by calibrating a 0-pressure position in experimental techniques.rnThe infrared spectra show the presence of vibrations originating from OH-groups and hydrous mineral inclusions in the range of 2500-4000 cm-1. Iron has also an effect upon the main and strongest peak at about 3310 cm-1. The 3310 cm-1 peak is shifted to higher wavenumber when iron content increases. This relationship is expressed by the equation y(3310)=0.92x+3309.17, in which y is peak position of the 3310 cm-1 and x is Fe2O3 content (wt.%). Similar to the obtained results in Raman and luminescence spectra, this expression can be used to estimate the Fe2O3 content and separate sapphires from different origins. rnThe UV-Vis-NIR absorption spectra point out the strong and sharp peaks at about 377, 387, and 450 nm related to dispersed Fe3+, a broad band around 557 and 600 nm related to intervalence charge transfer (IVCT) Fe2+/Ti4+, and a broader band around 863 nm related to IVCT of Fe2+/Fe3+. rnGenerally, sapphires from different localities were completely investigated on internal features, chemical compounds, and solid spectral characteristics. The results in each part contribute for identifying the iron content and separate sapphires from different localities order origins. rn

Raman-spektroskopische Untersuchungen an Alkali- und Erdalkalisilicatgläsern bei hohen Temperaturen

In der vorliegenden Arbeit wird die Struktur von Alkali- und Erdalkalisilicatglaesern bei hohen Temperaturen (bis 1800 K) mit Hilfe der Raman-Spektroskopie untersucht. Ein wesentlicher Teil der vorliegenden Arbeit besteht in dem Aufbau einer Hochtemperatureinrichtung, die es erlaubt, Raman-Spektren von Silicatglaesern bei sehr hohen Temperaturen zu messen. Mit der Hochtemperatur-Raman-Spektroskopie an Silicatglaesern sind erhebliche experimentelle Schwierigkeiten verbunden: Die thermische Strahlung der Probe überlagert sich mit dem Raman-Spektrum.Die Temperaturbestimmung der Glasprobe, die einen Durchmesser von nur 0,8 mm hat, erfolgt durch den Vergleich der Stokes- und Anti-Stokes-Raman-Intensitaeten einer intensiven Linie einer Referenzprobe. Die Natriumsilicatglaeser werden detailliert untersucht und die Verteilung der Struktureinheiten in den Natriumsilicatglaesern wird zwischen Zimmertemperatur und 900 K bestimmt. Aus der Verteilung der Strukturelemente wird eine Gleichgewichtskonstante K berechnet, welche die Disproportionierungsreaktion zwischen den Struktureinheiten in den Glaesern beschreibt. Der Wert für die Reaktionsenthalpie liegt im untersuchten Konzentrationsbereich zwischen 0 und 28 kJ/mol und haengt systematisch von der Zusammensetzung ab. Die Reaktionsenthalpie nimmt mit zunehmendem Natriumoxid-Gehalt zu.Die quantitative Auswertung der Raman-Spektren der Kaliumsilicatglaeser und der Bariumsilicatglaeser ist auf Grund deren Kristallisation bei hohen Temperaturen mit Problemen behaftet.

Determination of trace elemental species in periostracum of Cypraea shells

n this work, three Cypraea species (C. talpa, C. tigris and C. zebra) were exhaustively studied. The shells have been separated in the structural layers. The mineralogy, ultra- and micro-structure of each layer were analyzed by Confocal Laser Scanning Microscopy (CLSM), Scanning Electron Microscopy (SEM), X-Ray Diffractometry (XRD) and Raman Spectroscopy (RS). The presence of biologically relevant trace metals (Mn, Co, Fe, Zn, Cr, etc.) has been investigated using Instrumental Neutron Activation Analysis (INAA) and Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) as detection tool. A new method has been developed and optimized to extract and analyze the soluble organic matrix (SOM) of the shell. Although the molecular nature of the SOM is not really known, it contains at least large protein fraction, if not only consists of proteins. The extracted matrices were compared between layers and species using Size Exclusion High Performance Liquid Chromatography coupled with Ultra Violet Spectrometry (SE-HPLC-UV), Gel electrophoresis (GE) and protein quantification tests. For the first time to our knowledge the association of trace elements to the protein in the SOM of the shell was studied using hyphenated on line as well as combined off line techniques and validated through inter-comparison tests between the different methods applied. Interesting correlations between the trace element concentration, the microstructure and the protein content were directly and indirectly detected. The metals Cu, Ni, Co and Zn have shown to bind to the SOM extracted from C. talpa, C. tigris and C. zebra shells. Within the conclusions of this work it was demonstrated that these protein-metal-complexes (or metal containing proteins) change from one layer to the other and are different between the three snails analyzed. In addition, the complexes are clearly related only to certain protein fractions of the SOM, and not to the whole SOM observed. These fractions and show not to be very metal-specific (i.e. some of these fractions bind two or three different metals).

Time-resolved surface enhanced resonance Raman spectro-electrochemistry of heme proteins

The membrane protein Cytochrome c Oxidase (CcO) is one of the most important functional bio-molecules. It appears in almost every eukaryotic cell and many bacteria. Although the different species differ in the number of subunits, the functional differences are merely marginal. CcO is the terminal link in the electron transfer pathway of the mitochondrial respiratory chain. Electrons transferred to the catalytic center of the enzyme conduce to the reduction of molecular oxygen to water. Oxygen reduction is coupled to the pumping of protons into the inter-membrane space and hence generates a difference in electrochemical potential of protons across the inner mitochondrial membrane. This potential difference drives the synthesis of adenosine triphosphate (ATP), which is the universal energy carrier within all biological cells. rnrnThe goal of the present work is to contribute to a better understanding of the functional mechanism of CcO by using time-resolved surface enhanced resonance Raman spectroscopy (TR-SERRS). Despite intensive research effort within the last decades, the functional mechanism of CcO is still subject to controversial discussions. It was the primary goal of this dissertation to initiate electron transfer to the redox centers CuA, heme a, heme a3 and CuB electrochemically and to observe the corresponding redox transitions in-situ with a focus on the two heme structures by using SERRS. A measuring cell was developed, which allowed combination of electrochemical excitation with Raman spectroscopy for the purpose of performing the accordant measurements. Cytochrome c was used as a benchmark system to test the new measuring cell and to prove the feasibility of appropriate Raman measurements. In contrast to CcO the heme protein cc contains only a single heme structure. Nevertheless, characteristic Raman bands of the hemes can be observed for both proteins.rnrnIn order to investigate CcO it was immobilized on top of a silver substrate and embedded into an artificial membrane. The catalytic activity of CcO and therefore the complete functional capability of the enzyme within the biomimetic membrane architecture was verified using cyclic voltammetry. Raman spectroscopy was performed using a special nano-structured silver surface, which was developed within the scope of the present work. This new substrate combined two fundamental properties. It facilitated the formation of a protein tethered bilayer lipid membrane (ptBLM) and it allowed obtaining Raman spectra with sufficient high signal-to-noise ratios.rnSpectro-electrochemical investigations showed that at open circuit potential the enzyme exists in a mixed-valence state, with heme a and and heme a3 in the reduced and oxidized state, respectively. This was considered as an intermediate state between the non-activated and the fully activated state of CcO. Time-resolved SERRS measurements revealed that a hampered electron transfer to the redox center heme a3 characterizes this intermediate state.rn