Problems in fuelling spark ignition engines with dimethyl ether

This paper discusses briefly the production technology of dimethyl ether, taking into account plant raw materials and the physical and chemical properties of DME as compared to diesel fuel. The benefits and disadvantages of DME as a fuel are presented and changes in the emission of harmful substances characterised as compared to the combustion of diesel fuel. Also, basic usage problems are addressed, e.g. the wear of engine’s elements, cavity and leakages in the fuel system

A multiproxy approach to studying a large prehistoric enclosure in Ojców, Kraków Upland, Poland

Due to the presence of multiple caves and rock shelters as well as flint outcrops, Ojców Upland is a region with an exceptionally high concentration of prehistoric human settlement traces. It has attracted archaeologists for over 150 years, leading to what was considered to have been a proper prospection of the area. Nonetheless, the analysis of airborne laser scanning has recently brought surprising results. In the very centre of the upland, on the densely forested hill ‘Złota Góra’ (Golden Hill), the remains of an exceptionally large defensive structure in the form of several rows of embankments were found. The use of magnetic methods made it possible to confirm their anthropogenic origin and the likely type of embankment construction. In turn, the layout of embankments combined with the results of a surface survey and the analyses of the acquired artefacts and the settlement context speak in favour of linking this defensive structure with a high degree of probability with the Neolithic or Eneolithic, most likely the Lengyel-Polgár cycle or Baden culture. The presence of such a large fortification in the immediate vicinity of flint mines could shed new light on the image of the Late Neolithic-Early/Middle Eneolithic period in this part of Europe