Downloaded fromwhen approaching the HOMO or LUMO resonance of the molecular wire (28). The increased conductance at higher bias voltages then compensates for the molecular wire length increase in Fig. 4B (a factor of 40 is not sufficient for the achieved current increase). Thus, such a setup allows the determination of the small conductance (8.6 × 10 -13 S) of a single and the same molecular wire with 20 nm length (the conductance at small bias voltages cannot be measured over such a large distance, due to the extremely low current-below the detection limit-passing through the polymer in this case). In this regard, it would be interesting to prepare and study conjugated polymers with smaller HOMO-LUMO gaps. Such molecular wires should exhibit higher conductances and allow charge transport to be determined over even larger distances. Hominin footprints offer evidence about gait and foot shape, but their scarcity, combined with an inadequate hominin fossil record, hampers research on the evolution of the human gait. Here, we report hominin footprints in two sedimentary layers dated at 1.51 to 1.53 million years ago (Ma) at Ileret, Kenya, providing the oldest evidence of an essentially modern human-like foot anatomy, with a relatively adducted hallux, medial longitudinal arch, and medial weight transfer before push-off. The size of the Ileret footprints is consistent with stature and body mass estimates for Homo ergaster/erectus, and these prints are also morphologically distinct from the 3.75-millionyear-old footprints at Laetoli, Tanzania. The Ileret prints show that by 1.5 Ma, hominins had evolved an essentially modern human foot function and style of bipedal locomotion. Bipedalism is a key human adaptation that appears in the fossil record by 6 million years ago (Ma) (1). Considerable debate continues over when and in what context a modern human-like form of bipedalism evolved, because of a fragmentary record and disagreements over the functional interpretations of existing fossils and footprints (2-7). Modern human footprints reflect the specialized anatomy and function of the human foot, which is characterized by a fully adducted hallux, a large and robust calcaneus and tarsal region, a pronounced medial longitudinal arch, and short toes (2). Footprints reflect the pressure distribution as the foot makes contact with the substrate, but also the sediment's geomechanical properties (8). During normal walking, the weight-bearing foot undergoes a highly stereotypical movement and pressure distribution pattern in which the heel contacts the ground first, making a relatively deep impression on the substrate. This is followed by contact with the lateral side of the foot and metatarsal heads, after which weight transfers to the ball of the foot with peak pressure under the medial metatarsal heads, and finally ending with toe-off pressure under the hallux (9, 10). As a consequence, the deepest part of a footprint often occurs beneath the first and second metatarsal heads, that along with a deep hallucal impression cor...

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Modes of debris entrainment and subsequent transfer in seven “normal” and five surge-type glaciers in Svalbard (76–79° N) are outlined in the context of the structural evolution of a glacier as the ice deforms during flow. Three main modes of entrainment and transfer are inferred from structural and sedimentological observations: (i) The incorporation of angular rockfall material within the stratified sequence of snow/firn/superimposed ice. This debris takes an englacial path through the glacier, becoming folded. At the margins and at the boundaries of flow units the stratified ice including debris is strongly folded, so that near the snout the debris emerges at the surface on the hinges and limbs of the folds, producing medial moraines which merge towards the snout. The resulting lines of debris are transmitted to the proglacial area in the form of regular trains of angular debris. (ii) Incorporation of debris of both supraglacial and basal character within longitudinal foliation. This is particularly evident at the surface of the glacier at the margins or at flow unit boundaries. It can be sometimes demonstrated that foliation is a product of strong folding, since it usually has an axial planar relationship with folded stratification. Foliation-parallel debris thus represents a more advanced stage of deformation than in (i). Although the presence of basal debris is problematic, it is proposed that this material is tightly folded ice derived from the bed in the manner of disharmonie folding. The readily deformed subglacial sediment or bedrock surface represents the plane of décollement. (iii) Thrusting, whereby debris-rich basal ice (including regelation ice) and subglacial sediments are uplifted into an englacial position, sometimes emerging at the ice surface. This material is much more variable in character than that derived from rockfalls, and reflects the substrate lithologies; diamicton with striated clasts and sandy gravels are the most common facies represented. Thrusting is a dynamic process, and in polythermal glaciers is probably linked mainly to the transition from sliding to frozen bed conditions. It is not therefore a solely ice-marginal or proglacial process.

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It is commonly held that the major functional features of the human foot (e.g. a functional longitudinal medial arch, lateral to medial force transfer and hallucal (big-toe) push-off ) appear only in the last 2 Myr, but functional interpretations of footbones and footprints of early human ancestors (hominins) prior to 2 million years ago (Mya) remain contradictory. Pixel-wise topographical statistical analysis of Laetoli footprint morphology, compared with results from experimental studies of footprint formation; foot-pressure measurements in bipedalism of humans and non-human great apes; and computer simulation techniques, indicate that most of these functional features were already present, albeit less strongly expressed than in ourselves, in the maker of the Laetoli G-1 footprint trail, 3.66 Mya. This finding provides strong support to those previous studies which have interpreted the G-1 prints as generally modern in aspect.