Electrochemistry reveals archaeological materials

The characterization of materials constituting cultural artefacts is a challenging step in their conservation, due to the object’s uniqueness and the reduced number of conservation institutes able to supply non-destructive analysis. We propose an alternative analytical tool, which combines accessibility (low cost and portable) and high sensitivity, based on electrochemical linear sweep voltammetry (LSV) with paraffin impregnated graphite electrode (PIGE). To investigate the composition of “white alloys” that certainly have been used as decoration on copper-based Roman fibulae, sampling was done very locally by gently rubbing the selected areas with the PIGE. LSV results evidence the presence of silver, lead, and tin, supporting the argument provided by typological analysis that these metals were used for decoration

Object tracking and pose estimation using light-field object models

Geometric object models have been widely used for visual object tracking. In this contribution we present particle filter based object tracking with pose estimation using an appearance based lightfield object model. A light-field is an image-based object representation which can be used to render a photo realistic view of an arbitrarily shaped object from arbitrary viewpoints. It is shown how lightfield object models can be generated and utilized. Furthermore, we show how these models fit into the probabilistic framework of dynamic state estimation by defining an appropriate likelihood distribution from an image similarity metric. Finally, we present results and accuracy evaluations from tracking experiments of different objects.

Determination of the standard Gibbs energies of transfer of cations across the nitrobenzene|water interface utilizing the reduction of iodine in an immobilized nitrobenzene droplet

When a nitrobenzene (NB) droplet containing iodine is attached to a graphite electrode and immersed into a chloride containing aqueous (AQ) solution, the electrochemical reduction of iodine is accompanied by a transfer of chloride ions from NB to water. These chloride ions enter the NB phase in a preceding partition between the AQ and the NB phases, supported by formation of I2Cl� ions in NB and accompanied by the transfer of stoichiometric amounts of cations. The overall electrode reaction is of CErev type, where C refers to the preceding chemical step forming I2Cl�, and Erev refers to the reversible reduction of iodine at the graphitejNB interface and the simultaneous transfer of chloride from NB to water. If the chloride concentration in NB is insufficient to compensate by leaving the NB the amount of electrochemically produced iodide, a second voltammetric signal occurs at more negative potentials due to the transfer of iodide from NB to water. The kinetics and thermodynamics of the preceding chemical step C, determine the voltammetric behaviour of the system in such way that the ratio of peak currents of the first and second signals depends linearly on the Gibbs energy of transfer of the co-partitioned cations. The method was validated for cations of known Gibbs energies of transfer, and it was applied to cations of amino acids

Skulls on the road – historical traces of anatomical connections between Erlangen and Tartu/Dorpat

The Chair for the History of Medicine at the Friedrich-Alexander-University of Erlangen-Nürnberg (FAU) is currently researching the provenance of human remains in the University Collections. Obviously, the by far largest number of those specimens is found in the Anatomical Collection, which is studied in close cooperation with the Institute of Functional and Clinical Anatomy a joint research project. Several specimens dating back to the time of Heinrich Friedrich Isenflamm (1771–1828) have been identified that went from Erlangen to Dorpat as well as others that came from Dorpat to Erlangen

Abrasive Stripping Voltammetry and ESR Spectroscopy of Manganese in Carbonates

A combined approach using solid state electroanalysis (abrasive stripping voltammetry) and ESR spectroscopy was made to characterize the different species of manganese which are present in natural and synthetic calcium carbonates. Abrasive stripping voltammetry permits identifying Mn02 and MnC03, but the method fails when it comes to detecting unambiguously MnC03 in the presenee of Mn02. Neither can this method detect Mn2+ ions in mixed crystals of Cal_xMIlxC03because of their low concentrations. ESR spectroscopy can show that Mn2+ ions are present in calcite on Ca2+ sites. Additionally, information about the state and symmetry of Mn2+ site s and the local dynamics of the lattice can be obtained. In aragonite, only extremely small amounts of individual Mn2+ ions are present and most of the manganese is found in the form of Mn02 agglomerates. Solid state electroanalysis and ESR spectroscopy allow a rather complete qualitative specification of manganese in calcium carbonates

Determination of Standard Gibbs Energies of Transfer of Organic Anions across the Water/Nitrobenzene Interface

The oxidation of decamethylferrocene dissolved in a nitrobenzene droplet and attached to a graphite electrode that is immersed in an aqueous electrolyte solution provides the basis to determine the standard Gibbs energies of transfer of simple organic anions, such as those of aliphatic and aromatic mono- and dicarboxylic acids, and phenols. The data are rationalized on the basis of the constitution of the compounds

A Comparative Study of Lead Oxide Modified Graphite Paste Electrodes and Solid Graphite Electrodes with Mechanically Immobilized Lead Oxides

The cyclic voltammetry of red PbO, α-PbO2, β-PbO2 and BaPbO3 was studied with two different types of electrodes in acidic and alkaline media. In one case, microcrystalline particles of lead oxides were mechanically immobilized on the surface of paraffin-impregnated graphite rod electrodes (PIGE), while in the other case, lead oxides were added to a paste of graphite and silicone oil. The overall behaviour of lead oxides in both electrodes is very similar to the well-known behaviour of electrodes made of lead oxide powders. The results show that the binder does not effect the overall electro-chemistry of lead oxides. Moreover, the electrochemical reactions are more reversible for the paste electrode than in the case of the PIGE

Selective knockout of gold active sites

It has long been known that defects on a gold surface play an important role in electrocatalysis, but the precise mechanism has always been unclear. This work indicates that the defect sites provide partially filled d-orbitals that stabilize freeradical intermediates. Strong evidence for this hypothesis is that the sites can be selectively knocked out by treatment with OH• radicals generated by Fenton's reagent. The knockout effect is demonstrated using oxygen reduction, hydrogen reduction, and the redox electrochemistry of hydroquinone