3 research outputs found
Colour changes upon cooling of Lepidoptera scales containing photonic nanoarchitectures
The effects produced by the condensation of water vapours from the ambient in
the various intricate nanoarchitectures occurring in the wing scales of several
Lepidoptera species were investigated by controlled cooling (from room
temperature to -5 - -10 {\deg}C) combined with in situ measurement of changes
in the reflectance spectra. It was determined that, due to this procedure, all
photonic nanoarchitectures giving a reflectance maximum in the visible range
and having an open nanostructure exhibited alteration of the position of the
reflectance maximum associated with the photonic nanoarchitectures. The
photonic nanoarchitectures with a closed structure exhibited little to no
alteration in colour. Similarly, control specimens coloured by pigments did not
exhibit a colour change under the same conditions. Hence, this effect can be
used to identify species with open photonic nanoarchitectures in their scales.
For certain species, an almost complete disappearance of the reflectance
maximum was found. All specimens recovered their original colours following
warming and drying. Cooling experiments using thin copper wires demonstrated
that colour alterations could be limited to a millimetre, or below. Dried
museum specimens do not exhibit colour changes when cooled in the absence of a
heat sink due to the low heat capacity of the wings.Comment: 18 pages, 9 figures, including supplemen
Ancient genomic time transect from the Central Asian Steppe unravels the history of the Scythians
The Scythians were a multitude of horse-warrior nomad cultures dwelling in the Eurasian steppe during the first millennium BCE. Because of the lack of first-hand written records, little is known about the origins and relations among the different cultures. To address these questions, we produced genome-wide data for 111 ancient individuals retrieved from 39 archaeological sites from the first millennia BCE and CE across the Central Asian Steppe. We uncovered major admixture events in the Late Bronze Age forming the genetic substratum for two main Iron Age gene-pools emerging around the Altai and the Urals respectively. Their demise was mirrored by new genetic turnovers, linked to the spread of the eastern nomad empires in the first centuries CE. Compared to the high genetic heterogeneity of the past, the homogenization of the present-day Kazakhs gene pool is notable, likely a result of 400 years of strict exogamous social rules.N