Ribs of Pinna nobilis shell induce unexpected microstructural changes that provide unique mechanical properties

The reinforcement function of shell ribs depends not only on their vaulted morphology but also on their microstructure. They are part of the outer layer which, in the case of the Pinna nobilis bivalve, is built from almost monocrystalline calcitic prisms, always oriented perpendicular to the growth surfaces. Originally, prisms and their c-axes follow the radii of rib curvature, becoming oblique to the shell thickness direction. Later, prisms bend to reach the nacre layer perpendicularly, but their c-axes retain the initial orientation. Calcite grains form nonrandom boundaries. Most often, three twin disorientations arise, with two of them observed for the first time. Nano-indentation and impact tests demonstrate that the oblique orientation of c-axes significantly improves the hardness and fracture toughness of prisms. Moreover, compression tests reveal that the rib area achieves a unique strength of 700 MPa. The detection of the specific microstructure formed to toughen the shell is novel.The work was supported by the Polish National Agency for Academic Exchange (grant PPI/APM/2018/1/00049/U/001) and the National Science Center (grant UMO-2018/29/B/ST8/02200). MS was supported by the European Union from the resources of the European Social Fund (Project No.WNDPOWR. 03.02.00-00-I043/16). AGC was funded by project CGL2017-85118-P of the Spanish Ministerio de Ciencia e Innovación

Examination of Late Palaeolithic archaeological sites in northern Europe for the preservation of cryptotephra layers

We report the first major study of cryptotephra (non-visible volcanic ash layers) on Late Palaeolithic archaeological sites in northern Europe. Examination of 34 sites dating from the Last Termination reveals seven with identifiable cryptotephra layers. Preservation is observed in minerogenic and organic deposits, although tephra is more common in organic sediments. Cryptotephra layers normally occur stratigraphically above or below the archaeology. Nearby off-site palaeoclimate archives (peat bogs and lakes <0.3 km distant) were better locations for detecting tephra. However in most cases the archaeology can only be correlated indirectly with such cryptotephras. Patterns affecting the presence/absence of cryptotephra include geographic position of sites relative to the emitting volcanic centre; the influence of past atmospherics on the quantity, direction and patterns of cryptotephra transport; the nature and timing of local site sedimentation; sampling considerations and subsequent taphonomic processes. Overall, while tephrostratigraphy has the potential to improve significantly the chronology of such sites many limiting factors currently impacts the successful application

Use of unmanned aerial vehicles for water sampling in hard-to-reach water reservoirs

Collecting water samples for laboratory analysis from hard-to-reach surface areas such as post-industrial reservoirs (for example, tailings depositories) or overgrown lakes and ponds poses several difficulties, and it is potentially dangerous for the persons carrying out such activity. This can be improved by the use of unmanned aerial vehicles (UAVs) while ensuring an adequate level of safety and full compliance with the requirements of PN-ISO standards. This article presents the possibility of using the BSP in the option of autonomous (automatic) operation, allowing for the collection of water samples intended for physico-chemical tests, from hard-to-reach surface reservoirs, following the provisions of the relevant PN-ISO standards