Making money out of making money in Ancient Athens

The observed weights of ancient coins are usually less than the nominal “ideal” weights of the coin standards to which they belong because state authorities took a fee—“seigniorage”—for minting coins to cover costs and to make a profit. The basis for calculating the amount taken by the state and the way it administered manufacture are not well understood. Here we analyze the weights of 1344 of the earliest coins of Athens (c. 550–479 bce). We reveal a parabolic relationship between the cost of the silver and the weights of the coins whereby a progressively higher proportion was taken as the denomination decreased, meaning that the smaller the coin, the larger was the proportion of silver taken from it. There was tight control of the minting process and mathematical sophistication in precisely adjusting the silver content from the first introduction of coinage. It also made minting a profitable business. Changes in minting practice can be detected with the introduction of the Athenian “owl” coins, when the percentage of silver taken by the state increased and the spread of weights widened to include coins weighing more than the nominal weight. The latter indicates a significant shift toward monetization of the economy

Fractionnement isotopique de l'Erbium et de l'Ytterbium dans le système Terre-Lune

Nous avons développé une méthode pour analyse isotopique de Yb et Er, deux terres rares aux propriétés chimiques identiques et aux températures de condensation différentes, avec comme objectifs (1) de déterminer la variabilité isotopique de ces éléments dans les processus pétrologiques terrestres, et (2) de comparer leurs compositions isotopiques dans les chondrites, la Terre et la Lune afin de déterminer le rôle potentiel de la condensation à haute température à partir de vapeurs qui a suivi l impact géant à l origine de la formation de la Lune. Les résultats obtenus montrent une plus grande variabilité des fractionnements isotopiques de Yb par rapport à ceux d Er. Deux effets contribuent à cette différence : un effet oxydo-réducteur et un effet de température. La corrélation positive obtenue entre la composition isotopique en Yb, et le rapport La/Yb dans les échantillons terrestres, peut être interprétée par la présence d une faible fraction d Yb(2+), Yb étant majoritairement présent sous la forme Yb(3+). La kimberlite (liquide magmatique formé par un faible taux de fusion partielle) est enrichie en isotopes lourds et les grenats, résidus de fusion partielle, sont isotopiquement légers, tandis que les basaltes de ride ou d îles ont des compositions isotopiques intermédiaires.La composition isotopique en Yb de la Lune est enrichie en isotopes légers par rapport à celle de la Terre et des chondrites. Dans le disque proto-lunaire, les frictions entre les phases fondues et gazeuses favorisent la migration des premiers condensats très réfractaires et enrichis en isotopes lourds vers la Terre, et celle de la vapeur enrichie en isotopes légers, vers l extérieur, au-delà de la limite de Roche à partir de laquelle la Lune s accrète. Ceci est un nouvel argument en faveur de la condensation de la Lune à partir de vapeur générée par un impact géant. La mesure de la composition isotopique d Er dans les échantillons lunaires reflète pour la première fois la capture par 167Er des neutrons produits par interaction du rayonnement cosmique galactique avec la surface lunaire. L apport de Er aux systèmes communément utilisés pour déterminer le spectre d énergie des neutrons d un matériau peut permettre de couvrir une gamme énergétique plus large et de disposer ainsi d un proxy plus complet pour l étude des histoires des irradiations des matériaux planétaires.Er and Yb are two refractory rare-earth elements that have overall similar crystallochemical properties but differ in their temperatures of condensation from the nebular gas. We developed an analytical protocol for the measurement of Er and Yb isotope compositions 1) to establish their isotopic variability in terrestrial magmatic processes 2) to compare their isotopic composition in chondrites, Earth and Moon in order to study fractionation during the high temperature condensation of vapor formed by the giant impact that generated the Moon. The range of mass-dependent isotope fractionation obtained is larger for Yb than Er isotopes. Two effects contribute to the difference between Er and Yb : a redox effect and a temperature effect.First, for terrestrial rocks, the presence of a small fraction of Yb(2+) together with the most common Yb(3+) is inferred from the positive corre- lation between Yb and the La/Yb ratio. Yb(3+) fractionates favorably into tighter bonds and, at the same time, is much more compatible than Yb(2+). Small-degree melts (kimberlite) tend to be enriched in the heavy Yb isotopes, whereas the opposite is true for residual garnets. Second, the stronger volatility of Yb with respect to Er is demonstrated by the apparent deficit of heavy Yb isotopes in the Moon with respect to the Earth, chondrites, and eucrites. Separation of vapor from melt and of heavy from light isotopes is first expected during the adiabatic expansion of the initial vapor plume. Subsequently, friction between melt and gas tends to further enrich the Moon feeding zone in silicate vapor to compensate the inward migration of melt out of the pre-lunar disk. The lighter isotope composition of Yb in lunar samples provides new evidence that the Moon formed by condensation of silicate vapor in the aftermath of the giant lunar impact.Erbium isotope ratios in lunar samples reflect for the first time the capture by 167Er of secondary neutrons produced by interactions of galactic cosmic rays with the lunar surface. The cross section of 167Er for neutron capture being particularly strong and its first resonance standing out at energies poorly covered by other nuclides, 167Er anomalies may help refine the knowledge of the neutron energy spectrum on the Moon and other planetary bodies.LYON-ENS Sciences (693872304) / SudocSudocFranceF

Definition of a new approach in ancient harbor geoarchaeology: geochemistry and ostracod analyses at Portus (Tiber delta, central Italy)

International audiencePortus constituted the harbour complex of imperial Rome from the 1st century AD onward. Located in a deltaic environment, the harbour was subject to influences of the Tyrrhenian marine environment and of the fluvial waters of the Tiber River. Such complex sedimentary processes registered also rapid environ-mental changes. Our research is based on the study of a sediment core (TR14) drilled in the access channel of the hexagonal basin of Trajan (Fig. 1). The goal of our study is the reconstruction the palaeo-environmental dynamics of the water column of the harbour according to a geochemical and an ostra-codological approach. The analysis of the ostracod assemblage has evidenced several palaeo-environmental phases. These phases could be identified through the autoeco-logical analysis of the 25 recognised taxa and their classification in four eco-logical groups (MAZZINI et al., 2011). The results obtained present a succession of four environments, defined by variations in salinity and oxygenation. From the bottom to a depth of 643 cm, the environment was a marine to brackish lagoon influenced by strong marine inputs as evidenced by the vic-ariance of Cyprideis torosa and Pontocythere turbida. P. turbida is a typical phy-tal ostracod often found together with Posidonia oceanica remains. From 600 to 454 cm the coastal marine environment becomes more stable. This could be linked to the establishment of the harbour activities and maintenance. The sta-bility of the environment is still evident in the subsequent group, from 435 to 305 cm, characterised by the dominance of C. torosa and the lack of any fresh-water influence. The increase in salinity could be related to evaporative effects on a closed body of water. From 300 cm the freshwater input becomes clear and constant although the influence of the close sea/brackish body of water is still noticeable. In the last metres a typical freshwater assemblage is represent-ed, dominated by truly freshwater taxa (Candona sp. and Pseudocandona marchica), evidence for the occurrence of a freshwater marsh. The geochemical results were analysed by Principal Components Analy-sis (PCA). The samples were assembled in several groups based on a Hierar-chical Ascendant Classification (cluster analysis). Through PCA analysis, the geochemical and ostracological results of the "functional" harbour unit (800-300 cm) were combined. The different elements recorded in the geochemical analysis are distributed according to the main ostracod assemblages (from fresh water to brackish water and sea water). These elements have been grouped according to the model proposed by SAGEMAN & LYONS (2003). An evolution of these deposits in three stages is proposed. While the fluvial envi-ronments were quite well oxygenated, the harbour environment was more characterised by an increasing anoxia of the water column as it was observed by ELMALEH et al. (2012) in the harbor of Tyre. In a second phase, the varia-tions in salinity distinguished the nature of the fluvial environments and the degree of openness to the sea of the harbour environment. The final phase is specific to a body of water completely isolated from fluviatile and marin

Variations du rapport (231Pa/230Th)xs,0 et de la composition isotopique du zinc dans des sédiments de l'océan Pacifique équatorial au Quaternaire (implications pour la productivité biologique et relations avec la thermocline)

LYON-ENS Sciences (693872304) / SudocSudocFranceF

La Terre à l'Archéen. Apport des isotopes de métaux de transition (Zn, Fe)

L Archéen, de 4 à 2,5 Ga, est la période qui a connu les plus grands bouleversements géologiques et biologiques de l histoire de la Terre : formation des continents, transition d une tectonique à composante verticale vers une tectonique des plaques horizontale, apparition de la vie, Le but de cette thèse est d étudier les conditions environnementales de la Terre à l Archéen, par l analyse des compositions isotopiques de métaux de transition (Fe, Zn) de roches provenant principalement de la province d Isua au Groenland (3,8 Ga). Apre s avoir adapté le protocole de séparation du Fe, Cu, Zn à des échantillons riches en Fe, nous avons acquis les données par spectrométrie de masse à source plasma et à multicollection MC-ICPMS. Nous nous sommes d abord intéressés au processus de serpentinisation de la croûte océanique, réaction produisant à la fois des nutriments pour la vie (CH 4 , H 2 ) et des minéraux catalyseurs (mackinawite) de la formation abiotique d acides aminés, molécules du vivant. L affleurement d Isua comporte une unité ophiolitique présentant les serpentinites les plus anciennes (3.81-3.70 Ga) : leur analyse permet d appréhender la réaction de serpentinisation à l Archéen. Les résultats obtenus pour la composition isotopique du zinc dans ces roches et dans des serpentinites modernes ont permis d établir une correspondance entre le processus de serpentinisation à Isua et la mise en place de volcans de boues de serpentinites à l aplomb de la fosse des Mariannes. Nous avons ainsi pu identifier Isua comme une zone d arrière-arc de subduction océanique, lieu d une serpentinisation produisant des fluides de température variable (100-300C) et de pH alcalin (9-12). Nous montrons que cette configuration atypique réunissant serpentinisation, fluides alcalins et édifices volcaniques est favorable à l émergence du vivant. Nous avons ensuite analysé de nombreux échantillons de formations de fer rubané (BIFs), sédiments propres à l Archéen et au début du Protérozoïque. L évolution de la composition isotopique du zinc de ces échantillons au cours du temps a permis d établir une chronologie de l'émersion des continents.Nos résultats sont en faveur d une émersion débutant il y a 2,9 Ga. Enfin, nos données nous informent sur la colonisation des continents émergés par la vie à 2,6 Ga et sur la pédogenèse de sols archéens comportant un horizon organique.During the Archean (4 to 2.5 Ga ago), the Earth experienced the biggest changes in terms of geological and biological settings continental growth, transition from sagduction towards purely horizontal plate tectonics, emergence of life, The purpose of the present study is to better understand the archean earth environment by measuring the isotopic composition of transition metals Zn, Fe of archean rocks. Most of the samples belong to the Isua supracrustal belt, in Greenland, dated 3.8 Ga. The chemical extraction protocol of Fe, Cu, Zn was adapted to our Fe-rich samples and isotopic analyses were conducted by multicollection inductively coupled plasma mass spectrometry. The serpentinization of the oceanic crust produces fuels for life (CH 4 , H 2 ) and mackinawite, which catalyses formation of complex organic compounds. Serpentinization may thus provide a suitable environment for the emergence of the first biomolecules. We analysed the oldest known serpentinites from Isua (3.81-3.70 Ga) to comprehend the archean serpentinization process. The isotopic compositions of zinc reported in this samples and in modern serpentinites attest to a strong similarity between Isua and the Mariana serpentinite mud volcanoes. We identified Isua as an oceanic forearc environment permeated by high-pH (9-12) hydrothermal solutions at medium temperature (100-300C). We show that such an environment could have fostered the emergence of early life. We also analyzed several banded iron formations (BIF), which are sediments limited to the Archean and Proterozoic. The temporal evolution of these samples' isotopic composition shows a close relationship with the continental freeboard. Our results support the continental emersion starting 2.9 Ga ago. Besides, we identified the life colonization of continents at 2.6 Ga together with pedogenesis of archean soils with an organic horizon.LYON-ENS Sciences (693872304) / SudocSudocFranceF

Exploration de l’apport de l’analyse des perceptions oculaires : étude préliminaire pour le bouclage de pertinence

National audienceOur work aims to evaluate the potential impact of the use of ocular perceptions analy- sis in the relevance feedback mechanism of a retrieval engine. We focus on ecological situations where the user evaluates the relevance of the results of a query via the snippets displayed on the results page. Our hypothesis is that the knowledge of the terms read by a user on the result page can be used to improve the relevance feedack mechanism, without explicit intervention of the user. For this, we model the visual behavior of the user when reading the results of a query, to extract indicators. We explored the last fixed word and the longest fixed word, in the results page and in each snippet. The results of the user experiments indicate that the longest fixation word is often a relevant word to complement the query.Nos travaux visent à évaluer l’impact potentiel de l’utilisation des perceptions ocu- laires vis-à-vis du mécanisme de bouclage de pertinence d’un moteur de recherche d’informa- tion. Nous nous sommes intéressés aux situations écologiques où l’utilisateur évalue la per- tinence des résultats d’une requête via les snippets affichées sur la page des résultats. Notre hypothèse est que la connaissance des termes lus par un utilisateur sur cette page de résultats peut être utilisée pour améliorer le mécanisme de bouclage de pertinence, sans intervention explicite de l’utilisateur. Pour cela, nous modélisons le comportement visuel de l’utilisateur lorsqu’il consulte les résultats d’une requête, pour extraire de cette modélisation des indicateurs. Nous avons étudié le dernier mot fixé et le mot le plus longtemps fixé, dans la page de résultats et dans chaque snippet. Les résultats des expériences réalisées avec des utilisateurs indiquent que le mot le plus longtemps fixé est souvent un mot pertinent pour compléter la requête

Toward Eye Gaze Enhanced Information Retrieval Relevance Feedback

International audienceInformation Retrieval (IR) is dedicated to retrieve relevant documents according to a user’s query. The literature in this field shows that gathering relevance information provided by the user on the documents retrieved by the IR system increases the overall quality of the system. The relevance information provided by the user is processed to refine his/her initial query, in a process called Relevance Feedback.Since it is cumbersome and time consuming for the user to explicitly provide such informa- tion, our hypothesis is that eye gaze information could be used to implicitly estimate the user’s interests, and thus help the relevance feedback mechanism.The main research question tackled here is is twofold: (1) what is the user behavioral model at the visual level in an information retrieval task, and how this model would determine the user’s interests and (2) how to integrate effectively such eye gaze elements into a relevance feedback mechanism in classical IR systems that present results list with documents extracts (called snippets).To achieve this goal, we split the problem into the following steps: (a) to model the user behaviour in front of a result list composed of snippets; (b) to define the eye gaze elements to be acquired and the way to link them to the user’s interests in document contents; (c) to build relevance feedback mechanisms that are able to use these elements; and (d) to ex- periment the proposal on a classical IR test collections to compare them to other relevance feedback approaches.The work presented here focuses on the former two elements above: we define a experimen- tal context to gather relevant information about user’s behaviour in front a result display composed of snippets, and we deduce the EM elements that will need to be acquired in order to perform IR relevance feedback