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During the late Miocene and the Pliocene, changes in the Central American and Indonesian seaway geometry are very important for ocean circulation and global climate. Various modelling studies have examined the separate effects of these two tropical seaways, especially their link to the onset of the Northern Hemisphere ice sheets through changes in the Atlantic meridional overturning circulation and associated heat and moisture transport. Although the existence of dual tropical seaways is closer to reality, there are very scarce modelling studies exploring the co-effects of dual tropical seaway changes, especially on the Pacific ocean circulation. Here we provide the results of a modelling study on this issue. Our results show that the combined shallow opening of tropical seaways can generate an active Pacific meridional overturning circulation (that is absent in modern conditions) by which the meridional and zonal sea surface temperature gradient in the Pacific largely reduce. In contrast, a deeper opening of tropical seaways cannot produce these changes in the Pacific ocean circulation. This study provides insights into and a better understanding of the role of tropical seaways in shaping the Pacific climate and highlights the importance of the sill depth of each seaway.

The mid-Holocene period (MH) has long been an ideal target for the validation of general circulation model (GCM) results against reconstructions gathered in global datasets. These studies aim to test GCM sensitivity, mainly to seasonal changes induced by the orbital parameters (longitude of the perihelion). Despite widespread agreement between model results and data on the MH climate, some important differences still exist. There is no consensus on the continental size (the area of the temperature anomaly) of the MH thermal climate response, which makes regional quantitative reconstruction critical to obtain a comprehensive understanding of the MH climate patterns. Here, we compare the annual and seasonal outputs from the most recent Paleoclimate Modelling Intercomparison Project Phase 3 (PMIP3) models with an updated synthesis of climate reconstruction over China, including, for the first time, a seasonal cycle of temperature and precipitation. Our results indicate that the main discrepancies between model and data for the MH climate are the annual and winter mean temperature. A warmer-than-present climate condition is derived from pollen data for both annual mean temperature (∼0.7 K on average) and winter mean temperature (∼1 K on average), while most of the models provide both colder-than-present annual and winter mean temperature and a relatively warmer summer, showing a linear response driven by the seasonal forcing. By conducting simulations in BIOME4 and CESM, we show that surface processes are the key factors creating the uncertainties between models and data. These results pinpoint the crucial importance of including the non-linear responses of the surface water and energy balance to vegetation changes.

The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent oceanic circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoaling and final closure of the eastern Tethys seaway played a major role in the oceanic circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reorganisation of oceanic circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO2 drawdown and that the oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.

The Pliocene climate (3.3 ~ 3.0 Ma) is often considered as the last sustained warm period with close enough geographic configurations compared to the present one and associated with atmospheric CO2 concentration (405 ± 50 ppm) higher than the modern level. It is therefore suggested that the warm Pliocene climate may provide a plausible scenario for the future climate warming with the important advantage, that for mid-Pliocene, many marine and continental data are available. To investigate this issue, we selected RCP4.5 scenario, one of the current available future projections, to compare the pattern of tropical atmospheric response with past warm mid-Pliocene climate. We performed three OAGCM simulations (RCP4.5 scenario, mid-Pliocene and present day simulation) with the IPSL-CM5A model and investigated atmospheric tropical dynamics through Hadley and Walker cell responses to warmer conditions. Our results show that there is a damping of the Hadley cell intensity in the northern tropics and an increase in both subtropics. Moreover, northern and southern Hadley cells expand poleward. The response of Hadley cell is stronger for RCP4.5 scenario than for mid-Pliocene, but in very good agreement with the fact the atmospheric CO2 concentration is higher in future scenario than mid-Pliocene (543 versus 405 ppm). Concerning the response of the Walker cell, we showed that, despite very large similarities, there are also some differences. i.e. the common features are for both scenarios: weakening of the ascending branch, leading to a suppression of the precipitation over the western tropical Pacific. The response of Walker cell is stronger in RCP4.5 scenario than mid-Pliocene but also depicts some major difference as an eastward shift of the rising branch of Walker cell in future scenario compared to the mid-Pliocene. In this paper, we explain the dynamics of the Hadley and Walker cell, and show that despite minor discrepancy, mid-Pliocene is certainly an interesting analogue for future climate changes in the tropical areas.

Climate and environments of the mid-Pliocene Warm Period (3.264 to 3.025 Ma) have been extensively studied. Whilst numerical models have shed light on the nature of climate at the time, uncertainties in their predictions have not been systematically examined. The Pliocene Model Intercomparison Project quantifies uncertainties in model outputs through a co-ordinated multi-model and multi-model/data intercomparison. Whilst commonalities in model outputs for the Pliocene are evident, we show substantial variation in the sensitivity of models to the implementation of Pliocene boundary conditions. Models appear able to reproduce many regional changes in temperature reconstructed from geological proxies. However, data/model comparison highlights the potential for models to underestimate polar amplification. To assert this conclusion with greater confidence, limitations in the time-averaged proxy data currently available must be addressed. Sensitivity tests exploring the "known unknowns" in modelling Pliocene climate specifically relevant to the high-latitudes are also essential (e.g. palaeogeography, gateways, orbital forcing and trace gasses). Estimates of longer-term sensitivity to CO2 (also known as Earth System Sensitivity; ESS), suggest that ESS is greater than Climate Sensitivity (CS), and that the ratio of ESS to CS is between 1 and 2, with a best estimate of 1.5.

Chromosome, a knowledge-based analysis system has been designed for the classification of human chromosomes. Its aim is to perform an optimal classification by driving a tool box containing the procedures of image processing, pattern recognition and classification. This paper presents the general architecture of Chromosome, based on a multiagent system generator. The image processing tool box is described from the met aphasic enhancement to the fine classification. Emphasis is then put on the knowledge base intended for the chromosome recognition. The global classification process is also presented, showing how Chromosome proceeds to classify a given chromosome. Finally, we discuss further extensions of the system for the karyotype building.

This paper describes briefly the new facility of the Saclay tandem booster for nuclear, atomic and solid state physics. An overview of the beam optics and dynamics inside the new superconducting linac booster is given.

A remotely-sensed image represents natural objects with irregular shapes, some of which have fractal properties. During data processing the most often used methods of determining the fractal dimension are analysed according to objects of known dimension. A new method which improves the accuracy of previous techniques is then presented. This process can be used for specific applications in remote sensing; on the one hand for the determination of the dimension of natural reliefs observed from a satellite and on the other hand for the analysis of the degree of decay of diseased trees observed in aerial photographs.

The Saclay heavy ion superconducting linac is now in full operation with all 50 resonators. The first half of the machine runs routinely since more than a year. We summarize in this paper our experience of the resonator behaviour on the accelerating line and give their present performances. Cooldown, multipactor barrier conditioning, and field raising procedures are also discussed.

The main characteristics and performance of the helix superconducting resonators designed and mounted in the new Saclay Booster Linac, the first European heavy ion superconducting accelerator, are reported. Half-wave resonators have been tested with a continuous /sup 12/C beam delivered by the FN tandem. The behavior is very similar to the theoretical calculations done with field distribution measurements. The accelerating field achieved is 2.15 MV/m, corresponding to an energy gain of 535 keV/charge. The complete booster, which now has 16 half-wave resonators in the first and last large cryostats, makes it possible to extend the mass range from A=12 up to at least A=80 with excellent optical and dynamical beam qualities. The important advantages of the new structures are the broadness of the transmit time factor curve, which makes it possible to accelerate low-velocity beams with good efficiency, and the simplicity of the mechanical design which only requires two helix welds. >

SAGAPA (System Architecture Generated from A Parallel Algorithm) is an image processing system design tool based on an original methodology that automatically carries out the minimal architecture adapted to the application algorithm in respect with a maximal execution time constraint. The obtained architecture is minimal in terms of number of processors, amount of memory, and complexity of interconnection network. An execution-driven type simulation is performed in order to estimate resource's utilization and to check the time constraint.

This paper deals with a CAD tool dedicated to the design and the simulation of specific array processor architectures. These architectures are described into a specific notation which includes major characteristics of the VHDL syntax. This language provides a very concise and legible means to specify array processors. A preprocessor generates full standard VHDL code describing the behavior of the designed architecture. An original application to image processing is given: the design of a specific architecture for the extraction of regions of interests.

To improve the optics and dynamics calculations along the booster lines, emittances in the longitudinal and radial phase space have been measured just before injection in the booster linac. We report here the main results of these measurements which are used to set the initial conditions in our ray tracing and transport programs. A first order calculation has also been performed from which we deduce the matrix equivalent to a resonator in the radial phase space.

A fully automatic system is presented for the analysis and the classification of human chromosomes. Its architecture is based on two cooperating sub-systems: a rule-based system including two types of knowledge (cytogenetics, image analysis) and a tool box containing the low level processings such as pattern recognition and classification methods. The multi-agents design of this system makes further developments easier (modularity) and allows to generalize it to other image analysis applications.

Despite their apparent complexity, remotely-sensed images present a simple structure specific to the remotely-sensed field. Using the concepts of variogram and fractal dimension, this paper proposes a classification of the textures of images based on simple models. Applications are given to segmentation and resampling.

Pour permettre d'augmenter la gamme de masse des ions lourds qui seront produits par l'Accélérateur Supraconducteur du CEN Saclay, des cavités à hélice demi-onde ont été étudiées et réalisées en série. Dans cet article, on donnera les caractéristiques principales de ces cavités ; en particulier le facteur de surtension et le gain d'énergie par charge, mesuré sous faisceau de 12C. Les principaux avantages de ces nouvelles structures sont essentiellement, l'élargissement de la courbe de facteur de temps de transit, permettant de garder une bonne efficacité pour de faibles vitesses, et la simplicité de réalisation mécanique qui minimise le nombre de soudures. On donnera également les performances atteintes pour la série de cavités qui équipe deux des six cryostats du post-accélérateur. Les premiers faisceaux ont été délivrés au début de l'année.