Description of an aerodynamic levitation apparatus with applications in Earth sciences

<p>Abstract</p> <p>Background</p> <p>In aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination with CO₂-laser heating, containerless melting at high temperature of oxides and silicates is possible. We apply aerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reduction experiments.</p> <p>Results</p> <p>Liquid silicate droplets (~2 mm) were maintained stable in levitation using a nozzle with a 0.8 mm bore and an opening angle of 60°. The gas flow was ~250 ml min^-1. Rock powders were melted and homogenized for microchemcial analyses. Laser melting produced chemically homogeneous glass spheres. Only highly (e.g. H₂O) and moderately volatile components (Na, K) were partially lost. The composition of evaporated materials was determined by directly combining levitation and inductively coupled plasma mass spectrometry. It is shown that the evaporated material is composed of Na > K >> Si. Levitation of metal oxide-rich material in a mixture of H₂and Ar resulted in the exsolution of liquid metal.</p> <p>Conclusions</p> <p>Levitation melting is a rapid technique or for the preparation of bulk rock powders for major, minor and trace element analysis. With exception of moderately volatile elements Na and K, bulk rock analyses can be performed with an uncertainty of ± 5% relative. The technique has great potential for the quantitative determination of evaporated materials from silicate melts. Reduction of oxides to metal is a means for the extraction and analysis of siderophile elements from silicates and can be used to better understand the origin of chondritic metal.</p

Evidence of high genetic variation among linguistically diverse populations on a micro-geographic scale: a case study of the Italian Alps

Although essential for the fine-scale reconstruction of genetic structure, only a few micro-geographic studies have been carried out in European populations. This study analyzes mitochondrial variation (651 bp of the hypervariable region plus 17 single-nucleotide polymorphisms) in 393 samples from nine populations from Trentino (Eastern Italian Alps), a small area characterized by a complex geography and high linguistic diversity. A high level of genetic variation, comparable to geographically dispersed European groups, was observed. We found a difference in the intensity of peopling processes between two longitudinal areas, as populations from the west-central part of the region show stronger signatures of expansion, whereas those from the eastern area are closer to the expectations of a stationary demographic state. This may be explained by geomorphological factors and is also supported by archeological data. Finally, our results reveal a striking difference in the way in which the two linguistically isolated populations are genetically related to the neighboring groups. The Ladin speakers were found to be genetically close to the Italian-speaking populations and differentiated from the other Dolomitic Ladins, whereas the German-speaking Cimbri behave as an outlier, showing signatures of founder effects and low growth rate

Foraging–Farming Transitions in Island Southeast Asia

The origins of agriculture have been debated by archaeologists for most of the discipline’s history, no more so than in Island Southeast Asia. The orthodox view is that Neolithic farmers spread south by sea from mainland China to Taiwan and thence to Island Southeast Asia, taking with them a new material culture and domestic rice and pigs and speaking the precursor of the Austronesian languages that are spoken in the region today. Opponents of this ‘farming/language dispersal’ theory have proposed models of acculturation, in which foragers acquired new material culture and food resources by trading with farmers. However, new work in archaeology, palaeoecology, palynology and anthropology, especially in Borneo, and in genetics and linguistics for the region as a whole, is suggesting that foraging/farming transitions in Southeast Asia were far more complex than either of these opposing ‘grand narratives’ of discontinuity (population colonisation) or continuity (acculturation) allows. Through the course of the Early/Mid-Holocene new material culture, technologies and foods were variously taken up, promoted or resisted in order to provision changes in the social and ideological constitution of societies. Whilst new readings of the data for foraging–farming transitions in the region vary, a consensus is emerging that it is more useful to focus on how materials and modes of life were used to underwrite changes in social networks than to seek to explain the archaeological record in terms of migrating farmers or acculturating foragers