TY - JOUR A1 - Frunza, L. A1 - Schönhals, Andreas A1 - Frunza, S. A1 - Parvulescu, V.I. A1 - Cojocaru, B. A1 - Carriazo, D. A1 - Martín, C. A1 - Rives, V. T1 - Rotational Fluctuations of Water Confined to Layered Oxide Materials - Nonmonotonous Temperature Dependence of Relaxation Times N2 - The rotational molecular dynamics of water confined to layered oxide materials with brucite structure was studied by dielectric spectroscopy in the frequency range from 10-2 to 107 Hz and in a broad temperature interval. The layered double hydroxide samples show one relaxation process, which was assigned to fluctuations of water molecules forming a layer, strongly adsorbed to the oxide surface. The temperature dependence of the relaxation rates has an unusual saddlelike shape characterized by a maximum. The model of Ryabov et al. (J. Phys. Chem. B 2001, 105, 1845) recently applied to describe the dynamics of water molecules in porous glasses is employed also for the layered materials. This model assumes two competing effects: rotational fluctuations of water molecules that take place simultaneously with defect formation, allowing the creation of free volume necessary for reorientation. The activation energy of rotational fluctuations, the energy of defect formation, a pre-exponential factor, and the defect concentration are obtained as main parameters from a fit of this model to the data. The values of these parameters were compared with those found for water confined to nanoporous molecular sieves, porous glasses, or bulk ice. Several correlations were discussed in detail, such as the lower the value of the energy of defect formation, the higher the number of defects. The pre-exponential factor increases with increasing activation energy, as an expression of the compensation law, and indicates the cooperative nature of the motional process. The involvement of the surface OH groups and of the oxygen atoms of the interlayer anions in the formation of hydrogen bonds was further discussed. For the birnessite sample, the relaxation processes are probably overlaid by a dominating conductivity contribution, which is analyzed in its frequency and temperature dependence. It is found that the conductivity of birnessite obeys the characteristics of semiconducting disordered materials. Especially the Barton/Nakajima/Namikawa relationship is fulfilled. Analyzing the temperature dependence of the direct current (dc) conductivity σ0 in detail gives some hint that σ0(T) has also an unusual saddlelike form. PY - 2007 DO - https://doi.org/10.1021/jp0717140 SN - 1089-5639 SN - 1520-5215 VL - 111 IS - 24 SP - 5166 EP - 5175 PB - Soc. CY - Washington, DC AN - OPUS4-15718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Constantinescu, B. A1 - Bugoi, R. A1 - Cojocaru, V. A1 - Radtke, Martin A1 - Calligaro, T. A1 - Salomon, J. A1 - Pichon, L. A1 - Röhrs, S. A1 - Ceccato, D. A1 - Oberländer-Târnoveanu, E. T1 - Micro-SR-XRF and micro-PIXE studies for archaeological gold identification - The case of Carpathian (Transylvanian) gold and of Dacian bracelets N2 - Trace-elements are more significant for provenancing archaeological metallic artifacts than the main components. For gold, the most promising elements are platinum group elements (PGE), Sn, Te, Sb, Hg and Pb. Several small fragments of natural Transylvanian gold – placer and primary – were studied by using micro-PIXE technique at the Legnaro National Laboratory AN2000 microbeam facility, Italy and at the AGLAE accelerator, C2RMF, Paris, France and by using micro synchrotron radiation X-ray fluorescence (micro-SR-XRF) at BESSY synchrotron, Berlin, Germany. The goal of the study was to identify the trace-elements, especially Sn, Sb and Te. A spectacular application to five Dacian gold bracelets authentication is presented (Sn and Sb traces). KW - Micro-PIXE KW - Micro-SR-XRF KW - Gold KW - Dacian bracelets KW - Transylvania PY - 2008 DO - https://doi.org/10.1016/j.nimb.2008.03.054 SN - 0168-583X SN - 1872-9584 VL - 266 IS - 10 SP - 2325 EP - 2328 PB - Elsevier CY - Amsterdam AN - OPUS4-17736 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Constantinescu, B. A1 - Bugoi, R. A1 - Cojocaru, V. A1 - Radtke, Martin A1 - Calligaro, T. A1 - Salomon, J. A1 - Pichon, L. A1 - Röhrs, S. A1 - Ceccato, D. A1 - Oberländer-Târnoveanu, E. A1 - Ionescu, C. A1 - Pop, D. T1 - Dacian bracelets and Transylvanian gold: ancient history and modern analyses KW - SRXRF KW - Gold KW - Archaeometrie KW - Authentication KW - Provenance KW - XRF KW - Micro-PIXE KW - Micro SR-XRF KW - Or KW - Authentification KW - FX PY - 2009 SN - 0399-1237 VL - 33 SP - 221 EP - 225 PB - Groupe CY - Rennes AN - OPUS4-23172 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Constantinescu, B. A1 - Oberländer-Târnoveanu, E. A1 - Bugoi, R. A1 - Cojocaru, V. A1 - Radtke, Martin T1 - The Sarmizegetusa bracelets N2 - We present the authentication and analysis of these beautiful Dacian bracelets of the first century BC, originally pillaged by treasure hunters and recovered thanks to an international crime chase. They were originally fashioned from gold panned from the rivers or dug from the mines of Transylvania and hammered into the form of coiled snakes. The lack of context is the greatest loss, but a votive purpose is likely given their proximity to the great sacred centre at Sarmizegetusa Regia. KW - Romania KW - Sarmizegetusa KW - Dacian KW - First century BC KW - Gold KW - Bracelets KW - Hoard KW - Sacred centre KW - World heritage site PY - 2010 UR - http://antiquity.ac.uk/ant/084/ant0841028.htm SN - 0003-598x VL - 84 SP - 1028 EP - 1042 PB - Univ. Press CY - Oxford AN - OPUS4-23169 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -