Possible Pleistocene hominin tracks from South Africa’s west coast

Two probable tracks have been identified on the ceiling of a small overhang in the Pleistocene Langebaan Formation on South Africa’s west coast. They may have been made by a hominin trackmaker. They appear to have been registered at walking speed on a level, sandy dune substrate. Three tracks, attributed to Homo sapiens, were previously identified near Langebaan in 1995, and were popularly labelled ‘Eve’s Footprints’. The new identification of possible hominin tracks near Langebaan is the second from South Africa’s west coast. This discovery adds to the sparse but growing global record of possible hominin tracks preserved in aeolianites. Significance:• Two probable fossil tracks have been identified on the ceiling of an overhang near Langebaan.• The tracks may have been made by a human walking on a level dune surface during the Pleistocene.• This discovery is the second of its kind on the west coast, and complements the 1995 identification near Langebaan of Pleistocene fossil tracks attributed to humans

All-Dielectric Rod-Type Metamaterials at Optical Frequencies

Light propagation in all-dielectric rod-type metamaterials is studied theoretically. The electric and magnetic dipole moments of the rods are derived analytically in the long-wavelength limit. The effective permittivity and permeability of a square lattice of rods are calculated by homogenizing the corresponding array of dipoles. The role of dipole resonances in the optical properties of the rod array is interpreted. This structure is found to exhibit a true left-handed behavior, confirming previous experiments [L. Peng \textit{et al.}, Phys. Rev. Lett. \textbf{98}, 157403 (2007)]. A scaling analysis shows that this effect holds at optical frequencies and can be obtained by using rods made, for example, of silicon.Comment: 10 pages, 4 figures. The title has been shortened; Figs. 1, 2 and 3 have been modified; Eq. 4 has been corrected (sign error); A few sentences have been added/rewritte

Biofilm assists recognition of avian trackways in Late Pleistocene coastal aeolianites, South Africa

Fourteen fossil avian tracksites have been identified in Late Pleistocene aeolianite deposits on the Cape south coast of SouthAfrica. One of these sites is unusual because of the preferential adherence of organic material (biofilm) to the natural cast tracks. This has enabled the recognition and identification of two ~6 m long, approximately parallel trackways that would otherwise not have been noticed. The trackways are visible from a distance of over 100 metres and contain 20 and 14 individual tracks, respectively. Up to 50 avian tracks are evident at this site. As the biofilm layer continues to thicken, the trackways become increasingly visible. Avian trackways of this length are globally rare.We propose that the biofilm adheres to sections with higher relief on a sedimentary surface, and that an understanding of this mode of preservation can be useful to more easily identify trackways in areas of comparable geological setting.JN

The Pleistocene fauna of the Cape south coast revealed through ichnology at two localities

East of Still Bay on the Cape south coast of South Africa lies a rugged, remote stretch of sea cliffs that expose Late Pleistocene aeolianites. A zone of dense concentration of fossil tracks occurs within this area. Two large rocks, which we call Roberts Rock and Megafauna Rock, were identified ~400 metres apart. These rocks contained a variety of trackways, individual tracks, burrow traces and invertebrate trace fossils on multiple bedding planes. Both rocks were found ex situ, but their context could be determined. Roberts Rock has subsequently slid into the ocean, and Megafauna Rock lies at the base of a coastal cliff. Probable trackmakers include elephant, long-horned buffalo, giant Cape horse, rhinoceros, medium and small artiodactyls, golden mole, birds and invertebrates. Dating studies at an adjacent site, which is comparable to the stratigraphy described here, indicate that both rocks were most likely deposited in Marine Isotope Stage 5e (~128–116 ka). Analysis and description of these tracksites confirms the potential of ichnology to complement the skeletal fossil record and to enhance the understanding of Pleistocene life in southern Africa. The ephemeral nature of such tracksites makes repeated visits to this coastline desirable, both to monitor the fate of known sites and to search for newly exposed trace fossil surfaces. Significance: • Roberts Rock and Megafauna Rock are two remarkable fossil tracksites on the Cape south coast, which contain tracks of four members of the Late Pleistocene megafauna. They provide a glimpse of Pleistocene dune life and suggest an area teeming with large mammals. • These tracks were made on dune surfaces near an interface between the grassland of the Palaeo-Agulhas Plain and the inland Fynbos–Strandveld–Renosterveld. Faunal assemblages from both vegetation zones might therefore be recorded. • The trace fossil record and body fossil record both have inherent biases, but have the potential to independently provide complementary information on palaeofaunal composition. • The two rocks have provided the first South African records of fossil elephant tracks (as first described by Dave Roberts and colleagues in 2008), the first rhinoceros track and the first extinct giant Cape horse track, and track evidence of the extinct long-horned buffalo. • Roberts Rock has slumped into the ocean, and it provides an example of the fate of many exposed tracksites. Conversely, new sites frequently become exposed. This scenario stresses the need for regular ichnological surveys along this track-rich coastline to monitor existing sites and to search for new sites

Silicon Mie Resonators for Highly Directional Light Emission from monolayer MoS2

Controlling light emission from quantum emitters has important applications ranging from solid-state lighting and displays to nanoscale single-photon sources. Optical antennas have emerged as promising tools to achieve such control right at the location of the emitter, without the need for bulky, external optics. Semiconductor nanoantennas are particularly practical for this purpose because simple geometries, such as wires and spheres, support multiple, degenerate optical resonances. Here, we start by modifying Mie scattering theory developed for plane wave illumination to describe scattering of dipole emission. We then use this theory and experiments to demonstrate several pathways to achieve control over the directionality, polarization state, and spectral emission that rely on a coherent coupling of an emitting dipole to optical resonances of a Si nanowire. A forward-to-backward ratio of 20 was demonstrated for the electric dipole emission at 680 nm from a monolayer MoS2 by optically coupling it to a Si nanowire

The Digital MIQE Guidelines Update: Minimum Information for Publication of Quantitative Digital PCR Experiments for 2020

Digital PCR (dPCR) has developed considerably since the publication of the Minimum Information for Publication of Digital PCR Experiments (dMIQE) guidelines in 2013, with advances in instrumentation, software, applications, and our understanding of its technological potential. Yet these developments also have associated challenges; data analysis steps, including threshold setting, can be difficult and preanalytical steps required to purify, concentrate, and modify nucleic acids can lead to measurement error. To assist independent corroboration of conclusions, comprehensive disclosure of all relevant experimental details is required. To support the community and reflect the growing use of dPCR, we present an update to dMIQE, dMIQE2020, including a simplified dMIQE table format to assist researchers in providing key experimental information and understanding of the associated experimental process. Adoption of dMIQE2020 by the scientific community will assist in standardizing experimental protocols, maximize efficient utilization of resources, and further enhance the impact of this powerful technology

Possible Pleistocene hominin tracks from South Africa’s west coast

Two probable tracks have been identified on the ceiling of a small overhang in the Pleistocene Langebaan Formation on South Africa’s west coast. They may have been made by a hominin trackmaker. They appear to have been registered at walking speed on a level, sandy dune substrate. Three tracks, attributed to Homo sapiens, were previously identified near Langebaan in 1995, and were popularly labelled ‘Eve’s Footprints’. The new identification of possible hominin tracks near Langebaan is the second from South Africa’s west coast. This discovery adds to the sparse but growing global record of possible hominin tracks preserved in aeolianites.Significance: Two probable fossil tracks have been identified on the ceiling of an overhang near Langebaan. The tracks may have been made by a human walking on a level dune surface during the Pleistocene. This discovery is the second of its kind on the west coast, and complements the 1995 identification near Langebaan of Pleistocene fossil tracks attributed to humans

Large Pleistocene avian tracks on the Cape south coast of South Africa

Prior to the inception of the Cape south-coast ichnology project, only one avian tracksite had been reported from South Africa. An additonal twenty-nine sites have now been identified. Although there are limitations and challenges inherent in the study of fossil avian tracks, these tracks have the capacity to complement the traditional skeletal fossil record. Six of these tracksites exhibit the tracks of large avian trackmakers. In some of these cases, the tracks are larger than would be anticipated from an understanding of extant birds in the region and from the skeletal fossil record. This raises the possibility of large Pleistocene forms of extant taxa, and of Late Pleistocene avian extinctions. In one case, track preservation was of exceptional quality, and allowed the identification of previously unreported flamingo feeding traces. French Title: Grandes traces aviaires du Pléistocène sur la côte sud du Cap en Afrique du Sud Avant le lancement du projet d’ichnologie de la côte sud du Cap, un seul site de traces fossiles d’oiseaux avait été signalée en Afrique du Sud. Vingt-neuf autres sites ont maintenant été identifiés. Bien qu’il y ait des limites et des défis inhérents à l’étude des traces fossiles aviaires, ces traces ont la capacité de compléter les fossiles squelettiques traditionnels. Six de ces sites de traces fossiles aviaires présentent les traces de grands oiseaux. Dans certains cas, les traces sont plus grandes que ce que l’on pourrait prévoir à partir des connaissances des oiseaux existants dans la régionet des fossiles squelettiques collectés. Cela soulève la possibilité de présence de taxons existants de grande forme au Pléistocène, et donc  d’extinctions aviaires du Pléistocène tardif. Dans un cas, la conservation des traces était d’une qualité exceptionnelle et a permis d’identifier des traces d’alimentation de flamants roses non enregistrées auparavant. &nbsp

Newly identified hominin trackways from the Cape south coast of South Africa

Three new Pleistocene hominin tracksites have been identified on the Cape south coast of South Africa, one in the Garden Route National Park and two in the Goukamma Nature Reserve, probably dating to Marine Isotope Stage 5. As a result, southern Africa now boasts six hominin tracksites, which are collectively the oldest sites in the world that are attributed to Homo sapiens. The tracks were registered on dune surfaces, now preserved in aeolianites. Tracks of varying size were present at two sites, indicating the presence of more than one trackmaker, and raising the possibility of family groups. A total of 18 and 32 tracks were recorded at these two sites, respectively. Ammoglyphs were present at one site. Although track quality was not optimal, and large aeolianite surface exposures are rare in the region, these sites prove the capacity of coastal aeolianites to yield such discoveries, and they contribute to what remains a sparse global hominin track record. It is evident that hominin tracks are more common in southern Africa than was previously supposed. Significance: Three new Pleistocene hominin trackways have been identified on the Cape south coast, bringing thenumber of known fossil hominin tracksites in southern Africa to six. The tracks were all registered on dune surfaces, now preserved as aeolianites. These are the six oldest tracksites in the world that are attributed to Homo sapiens. Hominin tracks are more common in southern Africa than was previously supposed