High-spatial resolution functional chemistry of nitrogen compounds in the observed UK meteorite fall Winchcombe

Organic matter in extraterrestrial samples is a complex material that might have played an important role in the delivery of prebiotic molecules to the early Earth. We report here on the identification of nitrogen-containing compounds such as amino acids and N-heterocycles within the recent observed meteorite fall Winchcombe by high-spatial resolution spectroscopy techniques. Although nitrogen contents of Winchcombe organic matter are low (N/C ~ 1–3%), we were able to detect the presence of these compounds using a low-noise direct electron detector. These biologically relevant molecules have therefore been tentatively found within a fresh, minimally processed meteorite sample by high spatial resolution techniques conserving the overall petrographic context. Carbon functional chemistry investigations show that sizes of aromatic domains are small and that abundances of carboxylic functional groups are low. Our observations demonstrate that Winchcombe represents an important addition to the collection of carbonaceous chondrites and still preserves pristine extraterrestrial organic matter

High-quality germanium growth on (111)-faceted V-groove silicon by molecular beam epitaxy

High-quality and low-defect-density germanium (Ge) buffer layers on silicon (Si) substrates have long been developed for group IV and III–V devices by suppressing defect propagation during epitaxial growth. This is a crucial step for the development of highly efficient photonic devices on Si substrates. Patterned silicon substrates have increasingly been employed for their ability to restrict and hinder the motion of defects. In this work, we demonstrate the effectiveness of an optimised two-step growth recipe structure on a (111)-faceted V-groove silicon substrate with a 350 nm flat ridge. This strategy successfully reduces the threading dislocation (TD) density while growing a 1 μm Ge buffer layer via molecular beam epitaxy. As a result, a high-quality buffer is produced with a low TD density on the order of 107 cm−2 and a surface roughness below 1 nm

Limpet Shells from the Aterian Level 8 of El Harhoura 2 Cave (Témara, Morocco): Preservation State of Crossed-Foliated Layers

International audienceThe exploitation of mollusks by the first anatomically modern humans is a central question for archaeologists. This paper focuses on level 8 (dated around * 100 ka BP) of El Har-houra 2 Cave, located along the coastline in the Rabat-Témara region (Morocco). The large quantity of Patella sp. shells found in this level highlights questions regarding their origin and preservation. This study presents an estimation of the preservation status of these shells. We focus here on the diagenetic evolution of both the microstructural patterns and organic components of crossed-foliated shell layers, in order to assess the viability of further investigations based on shell layer minor elements, isotopic or biochemical compositions. The results show that the shells seem to be well conserved, with microstructural patterns preserved down to sub-micrometric scales, and that some organic components are still present in situ. But faint taphonomic degradations affecting both mineral and organic components are nonetheless evidenced, such as the disappearance of organic envelopes surrounding crossed-foliated lamellae, combined with a partial recrystallization of the lamellae. Our results provide a solid case-study of the early stages of the diagenetic evolution of crossed-foliated shell layers. Moreover, they highlight the fact that extreme caution must be taken before using fossil shells for palaeoenvironmental or geochronological reconstructions. Without thorough investigation, the alteration patterns illustrated here would easily have gone unnoticed. However, these degradations are liable to bias any proxy based on the elemental, isotopic or biochemical composition of the shells. This study also provides significant data concerning human subsistence behavior: the presence of notches and the good preservation state of limpet shells (no dissolution/recrystallization, no bioerosion and no abrasion/fragmentation aspects) would attest that limpets were gathered alive with tools by Middle Palaeolithic (Aterian) populations in North Africa for consumption

Journal of veterinary parasitology

North Africa is quickly emerging as one of the more important regions yielding information on the origins of modern Homo sapiens. Associated with significant fossil hominin remains are two stone tool industries, the Aterian and Mousterian, which have been differentiated, respectively, primarily on the basis of the presence and absence of tanged, or stemmed, stone tools. Largely because of historical reasons, these two industries have been attributed to the western Eurasian Middle Paleolithic rather than the African Middle Stone Age. In this paper, drawing on our recent excavation of Contrebandiers Cave and other published data, we show that, aside from the presence or absence of tanged pieces, there are no other distinctions between these two industries in terms of either lithic attributes or chronology. Together, these results demonstrate that these two \u27industries\u27 are instead variants of the same entity. Moreover, several additional characteristics of these assemblages, such as distinctive stone implements and the manufacture and use of bone tools and possible shell ornaments, suggest a closer affinity to other Late Pleistocene African Middle Stone Age industries rather than to the Middle Paleolithic of western Eurasia

New Excavations at the Site of Contrebandiers Cave, Morocco

New excavations at Contrebandiers Cave, Morocco, began in 2007 and continued through 2010. This site, origi- nally excavated by Roche in the 1950s, contained deposits with Aterian, Iberomaurusian, and Neolithic materials, although the latter were completely removed during Roche\u27s excavations. This report presents an overview of the recent excavations, the stratigraphic sequence of the site, absolute dates based on OSL, TL, and ESR, and detailed data on the lithic (Iberomaurusian, Aterian, and Mousterian) and faunal assemblages, the latter of which includes large mammals, microvertebrates, and marine shells

The Pleistocene of Rabat (Morocco): Mollusks, Coastal Environments and Human Behavior

International audienc

Integrating Human-Animal Relationships into New Data on Aterian Complexity: a Paradigm Shift for the North African Middle Stone Age

International audienc

Abrupt Schottky Junctions in Al/Ge Nanowire Heterostructures

International audienceIn this Letter we report on the exploration of axial metal/semiconductor (Al/Ge) nanowire heterostructures with abrupt interfaces. The formation process is enabled by a thermal induced exchange reaction between the vapor-liquid-solid grown Ge nanowire and Al contact pads due to the substantially different diffusion behavior of Ge in Al and vice versa. Temperature-dependent I-V measurements revealed the metallic properties of the crystalline Al nanowire segments with a maximum current carrying capacity of about 0.8 MA/cm(2). Transmission electron microscopy (TEM) characterization has confirmed both the composition and crystalline nature of the pure Al nanowire segments. A very sharp interface between the (111) oriented Ge nanowire and the reacted Al part was observed with a Schottky barrier height of 361 meV. To demonstrate the potential of this approach, a monolithic Al/Ge/Al heterostructure Was used to fabricate a novel impact ionization device