The effective elastic thickness of the India Plate from receiver function imaging, gravity anomalies and thermomechanical modelling

The range and the meaning of the effective elastic thickness (EET) in continental areas have been subject to controversy over the last two decades. Here we take advantage of the new data set from the Hi-CLIMB seismological experiment to re-estimate the EET of the India Plate along a south-north profile extending from the Ganges basin to central Tibet. Receiver functions give a high-resolution image of the base of the foreland basin at similar to 5 km depth and constrain the crustal thickness, which increases northwards from similar to 35 km beneath the indo-gangetic plain to similar to 70 km in southern Tibet. Together with available data sets including seismic profiles, seismological images from both INDEPTH and HIMNT experiments, deep well measurements and Bouguer anomaly profiles, we interpret this new image with 2-D thermomechanical modelling solutions, using different type of crustal and mantle rheologies. We find that (1) the EET of the India Plate decreases northwards from 60-80 to 20-30 km as it is flexed down beneath Himalaya and Tibet, due to thermal and flexural weakening; (2) the only resistant layer of the India Plate beneath southern Tibet is the upper mantle, which serves as a support for the topographic load and (3) the most abrupt drop in the EET, located around 200 km south of the MFT, is associated with a gradual decoupling between the crust and the mantle. We show that our geometrical constraints do not allow to determine if the upper and lower crust are coupled or not. Our results clearly reveal that a rheology with a weak mantle is unable to explain the geometry of the lithosphere in this region, and they are in favour of a rheology in which the mantle is strong

Stress buildup in the Himalaya

The seismic cycle on a major fault involves long periods of elastic strain and stress accumulation, driven by aseismic ductile deformation at depth, ultimately released by sudden fault slip events. Coseismic slip distributions are generally heterogeneous with most of the energy being released in the rupture of asperities. Since, on the long term, the fault's walls generally do not accumulate any significant permanent deformation, interseismic deformation might be heterogeneous, revealing zones of focused stress buildup. The pattern of current deformation along the Himalayan arc, which is known to produce recurring devastating earthquakes, and where several seismic gaps have long been recognized, might accordingly show significant lateral variations, providing a possible explanation for the uneven microseismic activity along the Himalayan arc. By contrast, the geodetic measurements show a rather uniform pattern of interseismic strain, oriented consistently with long-term geological deformation, as indicated from stretching lineation. We show that the geodetic data and seismicity distribution are reconciled from a model in which microseismicity is interpreted as driven by stress buildup increase in the interseismic period. The uneven seismicity pattern is shown to reflect the impact of the topography on the stress field, indicating low deviatoric stresses (<35 MPa) and a low friction (<0.3) on the Main Himalayan Thrust. Arc-normal thrusting along the Himalayan front and east-west extension in southern Tibet are quantitatively reconciled by the model

Anode buffer layer at the transparent conductive anode/organic electron donor interface in organic solar cells

International audienc

XPS Study of the Band Alignment at the Interface ITO/CuI

The band alignment at the interface of an ITO/CuI heterojunction is studied by X-ray photoelectron spectroscopy (XPS). The measurements have been performed on samples obtained under the same experimental conditions as those used to achieve organic photovoltaic cells. The CuI upper layer was 3 nm thick. The semidirect XPS technique used to measure the band offsets allows us to estimate the band discontinuities at the interface ITO/CuI: ΔEv = 2.10 eV and ΔEc = 1.56 eV. This band alignment induces an increase of the work function of the anode when the structure ITO/CuI is used as electrode in organic solar cells for instance. As a matter of fact, the measurement, by means of a Kelvin probe, of the work function of the structures ITO/CuI, shows that it is significantly higher than that of ITO alone: 5.2 eV and 4.8 eV.

About MoO3 as buffer layer in organic optoelectronic devices, Technology Letters

MoO3 is well known as efficient anode buffer layer in optoelectronic devices. Actually, MoO3 can be easily deposited under vacuum, by sublimation for instance, and also by wet process. So it is known from a long time that the films deposited by sublimation are amorphous and slightly oxygen deficient, which induces a light blue coloration due to oxygen vacancies. These oxygen vacancies imply the presence of Mo4+ and Mo5+ in the films. The presence of oxygen vacancies increases the conductivity from 10-12 to 10-6 (Ωcm)-1, while stoichiometric films are insulating and MoO2 has a metallic like behaviour with s = 2 102 (Ωcm)-1. About the efficiency of MoO3 as buffer layer, recent studies questioned the MoO3 band structure generally admitted. Under ultra high vacuum, the measured ionisation energy, IE, and electron affinity are found to be 9.7 eV and 6.7 eV respectively, while the films are strongly n-type. Its means that the very large IE energy of the MoO3 excludes any hole transport via the valence band, while the energy alignment between the band conduction minimum, CB, of MoO3 and the Highest Occupied Molecular Orbital (HOMO) of the organic material is favourable for electron transfer between the two materials. In the case of organic photovoltaic cells, the photogenerated hole recombines with an electron at the interface between MoO3 and the organic layer. Indeed, the work function, WF, of the molybdenum oxide films depends strongly of its composition, WF decreases when the oxygen deficiency increases, and on the exposition, or not, of its surface to air contamination. This makes that WF varies from 6.9 eV for a layer studied under ultra high vacuum to 5.2 eV for a layer exposed to the air a few hours. However, since the initial value of WF is very high, MoO3 remains effective if the Highest Occupied Molecular Orbital of the organic material is lower than 6 eV. The band structure of MoO3 and the large possible variations of WF make that, for specific conditions of preparation and conditioning, MoO3 can also be used as CBL

Why are some species older than others? A large-scale study of vertebrates.

BACKGROUND: Strong variations are observed between and within taxonomic groups in the age of extant species and these differences can clarify factors that render species more vulnerable to extinction. Understanding the factors that influence the resilience of species is thus a key component of evolutionary biology, but it is also of prime importance in a context of climate change and for conservation in general. We explored the effect of extrinsic and intrinsic factors on the timing of the oldest diversification event in over 600 vertebrate species distributed worldwide. We used phylogenetic comparative methods to show that color polymorphism, latitude and reproduction (the latter through its interaction with latitude) affected the timing of the oldest diversification event within a species. RESULTS: Species from higher latitudes tended to be younger, and colour-polymorphic species were older than monomorphic species. Mode of reproduction was important also, in that the age of oviparous species decreased with latitude, whereas no pattern was apparent for viviparous species. Organisms which have already persisted for a long time may be more likely to deal with future modifications of their environment. CONCLUSIONS: Species that are colour polymorphic, viviparous, and/or live at low latitudes have exhibited resilience to past environmental changes, and hence may be better able to deal with current climate change

Standardized on-road tests assessing fitness-to-drive in people with cognitive impairments: A systematic review.

The on-road assessment is the gold standard because of its ecological validity. Yet existing instruments are heterogeneous and little is known about their psychometric properties. This study identified existing on-road assessment instruments and extracted data on psychometric properties and usability in clinical settings. A systematic review identified studies evaluating standardized on-road evaluation instruments adapted for people with cognitive impairment. Published articles were searched on PubMed, CINHAL, PsycINFO, Web of Science, and ScienceDirect. Study quality and the level of evidence were assessed using the COSMIN checklist. The collected data were synthetized using a narrative approach. Usability was subjectively assessed for each instrument by extracting information on acceptability, access, cost, and training. The review identified 18 published studies between 1994 and 2016 that investigated 12 different on-road evaluation instruments: the Performance-Based Driving Evaluation, the Washington University Road Test, the New Haven, the Test Ride for Practical Fitness to Drive, the Rhode Island Road Test, the Sum of Manoeuvres Score, the Performance Analysis of Driving Ability, the Composite Driving Assessment Scale, the Nottingham Neurological Driving Assessment, the Driving Observation Schedule, the Record of Driving Errors, and the Western University's On-road Assessment. Participants were mainly male (64%), between 48 and 80 years old, and had a broad variety of cognitive disorders. Most instruments showed reasonable psychometric values for internal consistency, criterion validity, and reliability. However, the level of evidence was poor to support any of the instruments given the low number of studies for each. Despite the social and health consequences of decisions taken using these instruments, little is known about the value of a single evaluation and the ability of instruments to identify expected changes. None of the identified on-road evaluation instruments seem currently adapted for clinical settings targeting rehabilitation and occupational priorities rather than road security alone. PROSPERO registration number CRD42018103276

Facile enhancement of bulk heterojunction solar cells performance by utilizing PbSe nanorods decorated with graphene

An efficient approach for improving the photoelectrical conversion efficiency (PCE) of the bulk heterojunction (BHJ) solar cells, based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acidmethyl ester (PC61BM), by incorporating PbSe nanorods decorated with graphene (G) into their active layer has been reported for the first time. Pristine PbSe and PbSe:G composites (with different amount of graphene) are synthesized via hydrothermal process and the formation mechanism is explained. The systematic investigation indicates that the crystallite size of PbSe:G increases with increasing grapheme content. The PCE of the classical BHJ solar cells based on P3HT:PC61BM is improved from 2.32 up to 2.57% by the incorporation of pristine PbSe. It is also enhanced by the incorporation of PbSe:G up to certain composition of graphene in which a maximum PCE value of 5.16% is achieved. The external quantum efficiency of the BHJ solar cells is also investigated. The photovoltaic parameters are discussed based on the morphology variation detected by scanning electron microscope and atomic force microscope of the active layers together with their UV–VIS absorption measurements

Open circuit voltage of organic photovoltaic cells using C60 as acceptor: variation with the donor

The open circuit voltage (Voc) of organic photovoltaic cells (OPVs) is an important parameter in terms of OPV performance. In the present work, we check that its value depends on the energy difference between the Lowest Unoccupied Molecular Orbital of the electron acceptor (LUMOA) and the Highest Occupied Molecular Orbital of the donor (HOMOD). The electron acceptor is the fullerene, while the electron acceptors are used as parameter. The results show that Voc increases with the value of Δ(LUMOA–HOMOD). However, for some molecules, this increase is not linear, which shows that other parameters are also determinant