Extralimital Senegalese species during Marine Isotope Stages 5.5 and 11 in the Canary Islands (29° N): Sea surface temperature estimates

The presence of Harpa doris Röding, 1798 in marine deposits of the last interglacial period, ~130-120 ka (marine isotope stage or MIS 5.5) in the Canary Islands (Gran Canaria, Lanzarote and Fuerteventura) enabled us to compare this occurrence with its present habitat in the Gulf of Guinea and the Cape Verde Islands, well to the south. This comparison leads to the conclusion that sea surface temperatures (SSTs) in the waters around the Canary Islands during the last interglacial period were at least 3.3 °C higher than today. H. doris is found in association with the large gastropod Persististrombus latus (Gmelin, 1791) as well as the coral Siderastrea radians (Pallas, 1766). The presence of these extralimital southern,warm-water species in the Canary Islands during the last interglacial period also implies a northward expansion of plankton-feeding larvae in seawater with a high chlorophyll-a content. Such conditionswould require a shortening of the southern arm of the cool Canary Current that dominates the waters around the Canary Islands at present. Marine deposits dating to ~400 ka (MIS 11) are also found on the Canary Islands. In these deposits, the presence of Saccostrea cucullata (Born, 1778) allows a comparison with its present habitat in the Gulf of Guinea. In this analysis, we conclude that SSTs in waters around the Canary Islands during this major interglacial period were at least 4.2 °C higher than today. Middle Pleistocene fossils of S. cucullata have also been found in the western Mediterranean Sea and Morocco, as well as the Cape Verde Islands. If these deposits also date to MIS 11, SST warming could have been a regional phenomenon, including much of the eastern Atlantic Ocean and Mediterranean Sea.

Modal liquid crystal microaxicon array

A novel tunable liquid crystal microaxicon array is proposed and experimentally demonstrated. The proposed structure is capable of generating tunable axicons (thousands of elements) of micrometric size, with simple control (four control voltages) and low voltage, and is totally reconfigurable. Depending on the applied voltages, control over the diameter, as well as the effective wedge angle, can be achieved. Controls over the diameter ranging from 107 to 77 μm have been demonstrated. In addition, a control over the phase profile tunability, from 12π to 24π radians, has been demonstrated. This result modifies the effective cone angle. The diameter tunability, as well the effective cone angle, results in a control over the nondiffractive Bessel beam distance. The RMS wavefront deviation from the ideal axicon is only λ∕3. The proposed device has several advantages over the existing microaxicon arrays, including being simple having a low cost. The device could contribute to developing new applications and to reducing the fabrication costs of current devices.