Search results for "strontium"
showing 10 items of 195 documents
Intrinsic nanostructures on the (001) surface of strontium titanate at low temperatures
2020
Atomically smooth (001) surfaces of SrTiO3 cut from the high-quality single crystals at two different miscut angles 0.9 and 7.0 deg between the real flat surfaces and crystallographic planes (001) were analyzed by means of the reflection high energy electron diffraction (RHEED) method from the room down to liquid helium temperatures. The diffraction patterns typical of the RHEED geometry close to ideal for a small miscut angle and those exhibiting distinct features of the specific periodicity associated with regular steps, which form due to the larger miscut angle, are presented. The surface symmetry and energetics were shown to impose differences in lattice parameters in parallel to a surf…
Preparation, Characterisation and Dielectric Properties of YBa2Cu3O7-δ/ Insulator-Heterostructures
1996
YBa 2 Cu 3 O 7-δ /insulator/Au-heterostructures on SrTiO 3 or LaAlO 3 substrates were prepared to study the properties of the materials SrTiO 3 , BaTiO 3 and Ceo 2 . X-ray diffraction measurements in Bragg-Brentano geometry show c-axis-oriented growth for the superconductor and the insulators SrTiO 3 and CeO 2 . Typical values for the rocking curve width of the different insulating films are between 0.4° and 0.8°. The highest breakdown fields are measured for the insulator SrTiO 3 with +37.5 kV/mm and -8.8 kV/mm. The permittivity for CeO 2 is independent of applied field and only weakly temperature dependent. This is in contrast to the perovskite type insulators, where the permittivity depe…
Recent progress in understanding the persistent luminescence in SrAl 2 O 4 :Eu,Dy
2019
Ever since the discovery of SrAl2O4:Eu,Dy persistent afterglow material, that can intensively glow up to 20 h, the mechanism of long-lasting luminescence has been a popular area of research. The re...
Synthesis of Eu<sup>2+</sup> and Dy<sup>3+</sup> Doped Strontium Aluminates and their Properties
2016
Strontium aluminate phosphors were synthesized by the solution combustion method using citric acid, urea or glycine as reducing agent and europium and dysprosium as dopants. The content of both dopants was in the range of 1 – 2 mol%. Dependence of phase composition, crystallite size and specific surface area on calcinations temperature, used reducing agents and dopants were determined. Luminescent properties of the calcinated at 1300 °C powders contained SrAl2O4 (90 %) and Sr4Al24O25 (10%) phases with crystallite size of 80 nm were determined.
Evidence for “Celtic migrations”? Strontium isotope analysis at the early La Tène (LT B) cemeteries of Nebringen (Germany) and Monte Bibele (Italy)
2013
Abstract Strontium isotope analysis on human remains from the Iron Age (4th/3rd century BC) cemeteries of Nebringen, Germany and Monte Bibele, Italy were carried out to investigate the role of residential changes during the period of the historic “Celtic migrations”. From an archaeological perspective, the location of the cemeteries in the Celtic core (Nebringen) and expansion area (Monte Bibele), and the distinctive development of their material culture, suggest that the buried populations had differing mobility rates. On the contrary, the strontium results indicate that only few individuals were mobile or non-local. There is, however, a difference in variation of strontium isotope ratios …
Diet and mobility during the Christian conquest of Iberia: The multi-isotopic investigation of a 12th-13th century military order in Évora, Portugal
2020
Abstract The Kingdom of Portugal was established with the help of military-monastic orders, which provided important defence against Muslim armies during the 12th–13th century Christian conquest. While historical sources document the main events of this period, this research seeks to elucidate individual lifestyles and movement, aspects typically absent from written records. A multi-isotopic approach was used on skeletal material from eight Christian and two Muslim burials from Evora, Portugal (11th–13th centuries). Anthropological and archaeological evidence suggests the Christian adults belonged to the Evora Militia, which we seek to confirm through the reconstructed diet and mobility of …
Mobility across the pre-Pyrenean mountain ranges during the Chalcolithic through strontium isotopes in human enamel: La Cueva de los Cristales (Sarsa…
2020
Abstract There is an increasing abundance in the archaeological record in Iberia for the Late Neolithic and the beginning of the Chalcolithic periods, mostly regarding burials. The higher pre-Pyrenean areas began to be settled more frequently, but the poor weather conditions have led researchers to suggest that human presence mostly took the form of sporadic visits. This argument has provoked substantial controversy given the increase not only in the archaeological artefacts recorded but also in the number of burial sites in less accessible places. To shed more light on the knowledge of these Chalcolithic mountain groups, we have carried out strontium isotope analysis of human enamel of ind…
The lay of land: Strontium isotope variability in the dietary catchment of the Late Iron Age proto-urban settlement of Basel-Gasfabrik, Switzerland
2018
Abstract Basel-Gasfabrik (Switzerland) comprises an extensive La Tene (chiefly Lt D, 150–80 BCE) settlement and two associated cemeteries at which strontium (87Sr/86Sr) isotope analysis of human and animal teeth investigated regional and supra-regional contacts. The interpretation of the analytic data, however, requires information on the isotopic baseline values around the site. Using 102 modern vegetation and 9 water samples from 51 localities, this study characterizes the isotopic ratios of the biologically available strontium of geological units and watercourses around Basel and compares these to 28 human infant, 6 pig, and 5 dog teeth from the site. Furthermore, pedological criteria ev…
Bioavailable 87Sr/86Sr in different environmental samples — Effects of anthropogenic contamination and implications for isoscapes in past migration s…
2012
(87)Sr/(86)Sr reference maps (isoscapes) are a key tool for investigating past human and animal migrations. However, there is little understanding of which biosphere samples are best proxies for local bioavailable Sr when dealing with movements of past populations. In this study, biological and geological samples (ground vegetation, tree leaves, rock leachates, water, soil extracts, as well as modern and archeological animal teeth and snail shells) were collected in the vicinity of two early medieval cemeteries ("Thuringians", 5-6th century AD) in central Germany, in order to characterize (87)Sr/(86)Sr of the local biosphere. Animal tooth enamel is not appropriate in this specific context t…
Burned bones forensic investigations employing near infrared spectroscopy
2017
The use of near infrared (NIR) spectroscopy was evaluated, by using chemometric tools, for the study of the environmental impact on burned bones. Spectra of internal and external parts of burned bones, together with sediment samples, were treated by Principal Component Analysis and cluster classification as exploratory techniques to select burned bone samples, less affected by environmental processes, to properly carry out forensic studies. Partial Least Square Discriminant Analysis was used to build a model to classify bone samples based on their burning conditions, providing an efficient and accurate method to discern calcined and carbonized bone. Additionally, Partial Least Square regres…