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The poor operational stability of non-fullerene electron acceptor (NFA) organic solar cells (OSCs) currently limits their commercial application. While previous studies have primarily focused on the degradation of the NFA component, we also consider here the electron donor material. We examine the stability of three representative donor polymers, PM6, D18, and PTQ10, paired with the benchmark NFA, Y6. After light soaking PM6 and D18 in air, we find an enhanced conversion of singlet excitons into trapped interchain polaron pairs on sub-100 femtosecond timescales. This process outcompetes electron transfer to Y6, significantly reducing the charge generation yield. However, this pathway is absent in PTQ10. We identify twisting in the benzo[1,2-b:4,5-b′]dithiophene (BDT)-thiophene motif shared by PM6 and D18 as the cause. By contrast, PTQ10 does not contain this structural motif and has improved stability. Thus, we show that the donor polymer can be a weak link for OSC stability, which must be addressed collectively with the NFA.

The structure and dynamics of networks formed by rod-shaped particles can be indirectly investigated by measuring the diffusion of spherical tracer particles. This method was used to characterize cellulose nanofibril (CNF) networks in both dispersed and arrested states, the results of which were compared with coarse-grained Brownian dynamics simulations. At a CNF concentration of 0.2 wt% a transition was observed where, below this concentration tracer diffusion is governed by the increasing macroscopic viscosity of the dispersion. Above 0.2 wt%, the diffusion of small particles (20-40 nm) remains viscosity controlled, while particles (100-500 nm) become trapped in the CNF network. Sedimentation of silica microparticles (1-5 mu m) in CNF dispersions was also determined, showing that sedimentation of larger particles is significantly affected by the presence of CNF. At concentrations of 0.2 wt%, the sedimentation velocity of 5 mu m particles was reduced by 99 % compared to pure water. Funding Agencies|The Knut and Alice Wallenberg; Wallenberg Wood Science Center

International audience; Atom probe tomography is unique in its ability to image in 3D at the atomic scale and measure composition in asemiconductor device with high sensitivity. However it suffers from many artefacts. The current state of the art ofnanoelectronic device analysis by atom probe is addressed and the challenges in device analysis in the next tenyears are laid out. Finally the improvements necessary in sample preparation, instrumentation and reconstructionprocedures are discussed

International audience; An analytical model describing the field evaporation dynamics of a tip made of a thin layer deposited on a substrate is presented in this paper. The difference in evaporation field between the materials is taken into account in this approach in which the tip shape is modeled at a mesoscopic scale. It was found that the non-existence of sharp edge on the surface is a sufficient condition to derive the morphological evolution during successive evaporation of the layers. This modeling gives an instantaneous and smooth analytical representation of the surface that shows good agreement with finite difference simulations results, and a specific regime of evaporation was highlighted when the substrate is a low evaporation field phase. In addition, the model makes it possible to calculate theoretically the tip analyzed volume, potentially opening up new horizons for atom probe tomographic reconstruction.

The issue of ancient human single or multiple dispersal pathways into Eurasia is theoretically significant for understanding adaptive processes involved in peopling vacant spaces and varied, unfamiliar ecosystems, but receives mostly marginal attention. The Western Asian staging-post remains most plausible, whereas an alternative peopling directly from the Maghreb across the Gibraltar Strait into Iberia and beyond, though problematic, is proposed repeatedly. The present review discusses these issues and findings requiring interpretation, with respect to chronology, fossil human and Palaeolithic evidence, and Early Pleistocene circumstances in the Circum-Mediterranean Basin and Europe. The spatiotemporal distribution of palaeoanthropological occurrences and Ethiopian fossil mammal expansions does not support the hypothesis of a single Early Pleistocene biogeographic event originating in Subsaharan Africa, spreading throughout Western Asia and Europe. On the other hand, this spatiotemporal distribution of ancient human evidence in Europe reveals an intriguing bimodal chronological pattern. Early Pleistocene occurrences in both Eastern Europe and Western Europe prove earlier than those in West-Central Europe and the Italian Peninsula, which are dateable to the Mid-Pleistocene. This Early Pleistocene distribution cluster of occurrences in Iberia and Atlantic Europe refutes implicitly a single linked human-Ethiopian mammal biogeographic event exclusively through Western Asia, while reviving the notion of ‘sweepstake’ dispersal directly across the Strait of Gibraltar, a scenario which, however, demands independent confirmation by reviewing past circumstances favourable for a crossing, as well as suggesting a series of multiple staging-posts. The observed bimodal spatiotemporal configuration becomes more compatible with another hypothesis namely, that Europe was peopled independently by converging population movements from both the Western Asian and Ibero-Moroccan staging posts during the Early Pleistocene, between ca. 1.85–1.40 Ma.

Although anthropogenesis reaches back to Pliocene times in Subsaharan Africa, hominid dispersals beyond began only by the Early Pleistocene, with the appearance of genus Homo with Lower Palaeolithic repertoires. Causes responsible for these events remain poorly understood. Direct evidence for environmental factors, such as prolonged aridity stress or linkage with emigrating African ungulate or carnivorous species, while plausible, remains weak or ambiguous. Bio-cultural evolutionary evidence, however, provides more compelling indications, supported by empirical findings. These are rooted in the hominid ‘dual heritage’ involving higher primate ancestry and a partly but significant zoophagous dietary shift. Several million years of evolutionary divergence separated early Homo from its pongid relatives. The consequences of an omnivorous–carnivorous shift, on the other hand, besides enabling harvesting food resources at different levels of the trophic pyramid, included ‘natural history intelligence’, observed commonly among social carnivores. It enhanced human–landscape–plant–animal relationship and knowledge. It also favoured home-ranges expansion and the eurytopic adaptability of mobile ancient foraging hominids, as well as ecological polymorphism. The latter enabled hominids to adapt and exploit an increasing range of ecosytems, from the semi-arid tropics to subtropical steppes or woodlands, Mediterranean habitats, temperate woodland/grasslands, and a diversity of tropical forest formations in Eastern Asia. This adaptive versatility, linked with encephalization, particularly the expansion and increasing complexity of the brain cortex surface, was reinforced by cultural behaviour, best documented by technological behaviour. Lower Palaeolithic toolmaking demonstrates another behavioural discontinuity or technological ‘mutation’ by a familiarity and mastery, as ‘first geologists’, in acquiring suitable minerals, and skill in producing and using tools, as ‘secondary energy traps’ for various purposes, including prey carcass processing. Intermittent fire production represents another ‘mutation’ implying that hominids were virtually unique in overcoming the genetically inherited pyrophobic response, common among mammals. Cultural behaviour, as domain of socially acquired and transmitted interpretation and meaning of events, objects or activities, for mediating the world, pervades various aspects of human life (technology, subsistence, social life, cognition). It inserted progressively a new ‘cultural environment’ to which hominids became increasingly adapted and reliant on. This African dual heritage and bio-cultural evolutionary path documents how early hominids began following a new, hitherto unexploited adaptive niche, illustrated by long-range dispersals and gradual colonization of Eurasian ecosystems throughout the Pleistocene. This expansion became increasingly non-biological and contingent on cultural repertoires.

Sediment cores were recovered from Stella Lake and Baker Lake, sub-alpine lakes located in Great Basin National Park, NV, in 2005 and 2007, respectively. The cores were analyzed for subfossil chironomid (Insecta: Diptera: Chironomidae) remains. Chronologies for the sediment cores, developed using 210Pb, indicate the cores span the 20th century. The midge communities present in the lakes experience muted compositional change through much of the 20th century; however, the post-AD 1980 interval is notable due to rapid lake-specific faunal turnover. The recently deposited sediment in Baker Lake is characterized by decreases in the relative of abundance of Psectrocladius semicirculatus/sordillelus, Cladotanytarsus mancus group and Procladius, the local extirpation of Chironomus, and an increase the proportion of Sergentia, Tanytarsus type G and Tanytarsus type B. The Stella Lake midge community experienced a shift post-AD 1990 from an assemblage dominated by Tanytarsus type G to a P. semicirculatus/sordillelus dominated community. Application of a chironomid-based inference model for mean July air temperature (MJAT), based on a calibration set developed for the Inter-Mountain West of the United States consisting of 79 lakes and 54 midge taxa (rjack2 = 0.55 °C, RMSEP = 0.9 °C, maximum bias = 1.66 °C), provided a means to reconstruct the 20th century temperature regime for the region. Stella Lake and Baker Lake experience large fluctuations in MJAT during the early to mid-20th century and consistently above average temperature during the late-20th century. The chironomid-inferred MJAT reconstructions for Stella Lake and Baker Lake track observed July temperature in the region encompassed by Nevada Climate Division #2 during the late-20th century.