Logic gates operated by bipolar photoelectrochemical water splitting

International audienceA new approach for the design of logic gates that do not involve chemical inputs is presented here. This concept is based on the polarization of a light-sensitive interface. AND and OR logic gates, working with cheap reactants, which locally triggered water splitting half reactions, were designed and operated

Mesoscale fluvial erosion parameters deduced from modeling the Mediterranean sea level drop during the Messinian (late Miocene)

International audienceAfter a base level drop, rivers are the first components of the landscape to respond by incising into topography. A base level drop results in a knickpoint in the downstream part of river longitudinal profiles. Whether knickpoints are preserved or erased during the upstream propagation of incision is still debated. Preservation and erasure of knickpoints are two end-member processes that work in natural systems at different timescales, different length scales, and different places. The huge (1500 m) and fast (tens of kiloyears) sea level drop in the Mediterranean during the Messinian resulted in the fast propagation of incision far inland. This is especially the case in the Rhone Valley (southern France) where the knickpoint is 300 km from the Mediterranean coast. Numerical modeling of this event has been performed using the ros model, which simulates both erosional and depositional processes in rivers. The best fit between numerical results and geological data is obtained for a nonlinear relation between incision and drainage area and for a small transport length of sediment. This small transport length, at least 2 orders of magnitude lower than the length of the Rhone, suggests that the longitudinal profile relaxed in a diffusive way, so that the initial knickpoint was not preserved. Finally, after a base level fall, the propagation of fluvial incision is very fast at geological timescales (hundreds of kiloyears). Despite this, the diffusive response implies that the time required for restoration of an equilibrium profile is very long

The mediterranean overflow in the Gulf of Cadiz: a rugged journey

The pathways and transformations of dense water overflows, which depend on small-scale interactions between flow dynamics and erosional-depositional processes, are a central piece in the ocean's large-scale circulation. A novel, high-resolution current and hydrographic data set highlights the intricate pathway travelled by the saline Mediterranean Overflow as it enters the Atlantic. Interaction with the topography constraints its spreading. Over the initial 200 km west of the Gibraltar gateway, distinct channels separate the initial gravity current into several plunging branches depth-sorted by density. Shallow branches follow the upper slope and eventually detach as buoyant plumes. Deeper branches occupy mid slope channels and coalesce upon reaching a diapiric ridge. A still deeper branch, guided by a lower channel wall marked by transverse furrows, experiences small-scale overflows which travel downslope to settle at mid-depths. The Mediterranean salt flux into the Atlantic has implications for the buoyancy balance in the North Atlantic. Observations on how this flux enters at different depth levels are key to accurately measuring and understanding the role of Mediterranean Outflow in future climate scenarios.project INGRES3 [CTM2010-21229]; project STOCA (IEO); project PESCADIZ (IEO); project INDEMARES [LIFE07 NAT/E/000732+]; project MOC2 [CTM2008-06438-C02-01]; project MED-OUTFLOW [CTM2008-03422-E/MAR, CTM2010-11488-E]; project PELCOSAT (IEO); project SEMANE; project DILEMA [CTM2014-59244-C3-2-R]; project INPULSE [CTM2016-75129-C3-1-R]; SISMER data center; PANGEA data center; IEO data center; ICES data center; BODC data center; NOAA data center; CONTOURIBER project [CTM2008-06399-C04-01/MAR]info:eu-repo/semantics/publishedVersio

Single-Step Screening of the Potential Dependence of Metal Layer Morphologies along Bipolar Electrodes

The preparation of surface gradients is a hot topic in contemporary research. Among various physical chemistry approaches, bipolar electrochemistry allows the control of such gradients through the interfacial polarization between a conducting substrate and an electrolyte solution. Here, we report the straightforward, single‐step generation of metal composition gradients on cylindrical carbon fibers. The screening of different metal deposit morphologies, which evolve gradually along a bipolar electrode, is demonstrated with monometallic layers as well as a bimetallic composite layer based on copper and nickel

Testing fluvial erosion models using the transient response of bedrock rivers to tectonic forcing in the Apennines, Italy

The transient response of bedrock rivers to a drop in base level can be used to discriminate between competing fluvial erosion models. However, some recent studies of bedrock erosion conclude that transient river long profiles can be approximately characterized by a transport‐limited erosion model, while other authors suggest that a detachment‐limited model best explains their field data. The difference is thought to be due to the relative volume of sediment being fluxed through the fluvial system. Using a pragmatic approach, we address this debate by testing the ability of end‐member fluvial erosion models to reproduce the well‐documented evolution of three catchments in the central Apennines (Italy) which have been perturbed to various extents by an independently constrained increase in relative uplift rate. The transport‐limited model is unable to account for the catchments’response to the increase in uplift rate, consistent with the observed low rates of sediment supply to the channels. Instead, a detachment‐limited model with a threshold corresponding to the field‐derived median grain size of the sediment plus a slope‐dependent channel width satisfactorily reproduces the overall convex long profiles along the studied rivers. Importantly, we find that the prefactor in the hydraulic scaling relationship is uplift dependent, leading to landscapes responding faster the higher the uplift rate, consistent with field observations. We conclude that a slope‐ dependent channel width and an entrainment/erosion threshold are necessary ingredients when modeling landscape evolution or mapping the distribution of fluvial erosion rates in areas where the rate of sediment supply to channels is low

Avant la « langue des calculs ». L’écriture des opérations dans l’Algebra de Pierre de La Ramée

Dans son Algebra de 1560, Pierre de La Ramée (1515-1572) emploie une manière originale de poser les opérations de l’algèbre sous la forme de ce que j’appellerai des « schémas de calcul ». Ces schémas constituent un aspect singulier de l’écriture mathématique de Pierre de La Ramée par rapport à celle de ses contemporains. Avec ses « schémas de calcul », La Ramée contribue à l’invention, pour les mathématiques de la modernité, d’une langue propre. Leur étude conduit donc à réfléchir sur les prémisses de ce que les philosophes des mathématiques appellent parfois la « révolution symbolique » du xviie siècle. Mon but est de montrer en quoi cette révolution est liée pour une part aux possibilités offertes par l’imprimerie. Je m’appuierai pour cela sur les travaux de Walter J. Ong.In Peter Ramus’s treatise of Algebra published in 1560, algebraic operations are displayed in an original and systematic way, in a form I will call “calculation diagrams”. These diagrams appear as one original aspect of Ramus’s mathematical writing compared to his contemporaries’. With his “calculation diagrams”, Ramus contributed to the invention of a specific language for mathematics. The Algebra can therefore be considered as an indicator of what philosophers and historians of mathematics call the “symbolic revolution” that occurs in the 17th Century. My aim is to show that this so-called “symbolic Revolution” may have had something to do with the development of the printing press. To achieve this I will base my study on Walter J. Ong’s works

À qui incombe le patrimoine religieux québécois ?

Cette étude rend compte des rapports ambigus, oscillant de la coopération à la concurrence, entre l’Église, l’État et les musées québécois au regard de l’administration et de la protection du patrimoine matériel religieux, spécifiquement en contexte d’aliénation.This study focuses on the ambiguous relationship, alternating between cooperation and competition, between Quebec’s Church, State and museums in relation to the administration and the protection of tangible religious heritage, particularly in the context of disposal

Fifteen years of research on oral–facial–digital syndromes: from 1 to 16 causal genes

Oral–facial–digital syndromes (OFDS) gather rare genetic disorders characterised by facial, oral and digital abnormalities associated with a wide range of additional features (polycystic kidney disease, cerebral malformations and several others) to delineate a growing list of OFDS subtypes. The most frequent, OFD type I, is caused by a heterozygous mutation in the OFD1 gene encoding a centrosomal protein. The wide clinical heterogeneity of OFDS suggests the involvement of other ciliary genes. For 15 years, we have aimed to identify the molecular bases of OFDS. This effort has been greatly helped by the recent development of whole-exome sequencing (WES). Here, we present all our published and unpublished results for WES in 24 cases with OFDS. We identified causal variants in five new genes (C2CD3, TMEM107, INTU, KIAA0753 and IFT57) and related the clinical spectrum of four genes in other ciliopathies (C5orf42, TMEM138, TMEM231 and WDPCP) to OFDS. Mutations were also detected in two genes previously implicated in OFDS. Functional studies revealed the involvement of centriole elongation, transition zone and intraflagellar transport defects in OFDS, thus characterising three ciliary protein modules: the complex KIAA0753-FOPNL-OFD1, a regulator of centriole elongation; the Meckel-Gruber syndrome module, a major component of the transition zone; and the CPLANE complex necessary for IFT-A assembly. OFDS now appear to be a distinct subgroup of ciliopathies with wide heterogeneity, which makes the initial classification obsolete. A clinical classification restricted to the three frequent/well-delineated subtypes could be proposed, and for patients who do not fit one of these three main subtypes, a further classification could be based on the genotype

Reduction of Long-Term Bedrock Incision Efficiency by Short-Term Alluvial Cover Intermittency

International audienceFluctuations of the sediment volume stored in mountain channels are driven by stochastic variations of discharge and sediment supply and can inhibit bedrock incision if sediment thickness is too large. Here, I study how this shortƒ]term stochasticity propagates into the longƒ]term reduction of bedrock incision efficiency (the cover effect) at geological time scales. I introduce a new numerical model that resolves sediment transport and bedrock incision at daily time scales, and is run for thousands of years. It incorporates (1) a transport threshold and daily stochastic variations in water discharge and sediment supply, (2) a freely evolving channel width and slope, and (3) an explicit treatment of alluvial thickness variations and corresponding bed incision reduction. For typical mountain river conditions the model predicts that alluvial cover oscillates between complete and negligible incision reduction. In this intermittent regime the longƒ]term cover effect is mainly set by the fraction of time spent in full cover, and the presentƒ]day extent of alluvial cover is not representative of longƒ]term dynamics. The longƒ]term dynamics. The longƒterm integrated cover effect law differs strongly from proposed theoretical and experimental models, and it is controlled by sediment supply stochasticity rather than the details of cover development at the hydraulic time scale. Model results also suggest that steady state channel configuration always depends on sediment supply rate, while being never limited by transport capacity or strictly detachment limited. These results point out that discharge and sediment supply stochasticity should not be considered less important than the intricate details of incision laws to model long-term bedrock channel dynamics

The EChemPen: A Guiding Hand To Learn Electrochemical Surface Modifications

The Electrochemical Pen (EChemPen) was developed as an attractive tool for learning electrochemistry. The fabrication, principle, and operation of the EChemPen are simple and can be easily performed by students in practical classes. It is based on a regular fountain pen principle, where the electrolytic solution is dispensed at a tip to locally modify a conductive surface by triggering a localized electrochemical reaction. Three simple model reactions were chosen to demonstrate the versatility of the EChemPen for teaching various electrochemical processes. We describe first the reversible writing/erasing of metal letters, then the electrodeposition of a black conducting polymer “ink”, and finally the colorful writings that can be generated by titanium anodization and that can be controlled by the applied potential. These entertaining and didactic experiments are adapted for teaching undergraduate students that start to study electrochemistry by means of surface modification reactions