Mineral Processing Symposium — Société de l'Industrie Minérale — Paris 1973     

Maxime Brandela 《International Journal of Mineral Processing》1974,1(1):101-105

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Les manifestations actuelles du volcanisme aux Nouvelles Hébrides (Mélanésie)     

E. Aubert De La Rüe 《Bulletin of Volcanology》1960,23(1):197-205

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Chronology of Vesuvius’ activity from A.D. 79 to 1631 based on archeomagnetism of lavas and historical sources     

Claudia?PrincipeEmail author  Jean?Claude?Tanguy  Simone?Arrighi  Anna?Paiotti  Maxime?Le?Goff  Ugo?Zoppi 《Bulletin of Volcanology》2004,66(8):703-724

The activity of Vesuvius between A.D. 79 and 1631 has been investigated by means of precise archaeomagnetic dating of primary volcanic deposits and taking into account the stratigraphy of lavas and tephra, historical written accounts, archaeological evidence related to the developing urbanisation, and radiocarbon ages. We found that the historical records are highly useful in constraining the timing of the main events, even if the data are often too scarce and imprecise for ascertaining the details of all phases of activity, especially their magnitude and emplacement of all the deposit types. In addition, some eruptions that took place in the 9^th and 10^th centuries appear to be unnoticed by historians. The archaeomagnetic study involved 26 sites of different lavas and 2 pyroclastic deposits. It shows that within the 15 centuries which elapsed between A.D. 79 and 1631, the effusive activity of Vesuvius clustered in the relatively short period of time between A.D. 787 and 1139 and was followed by a 5-century-long repose period. During this time Vesuvius prepared itself for the violent explosive eruption of 1631. The huge lavas shaping the morphology of the coast occurred largely through parasitic vents located outside the Mount Somma caldera. One of these parasitic vents is located at low elevation, very close to the densely inhabited town of Torre Annunziata. Among the various investigated lavas, a number of which were previously attributed to the 1631 eruption, none is actually younger than the 12^th century. Therefore it is definitively concluded that the destructive 1631 event was exclusively explosive.Editorial handling: J. McPhie  相似文献   

The impact of vegetation on fractionation of rare earth elements (REE) during water–rock interaction     

P. Stille  M. Steinmann  M.-C. Pierret  F. Gauthier-Lafaye  D. Aubert  A. Probst  D. Viville  F. Chabaux 《Journal of Geochemical Exploration》2006,88(1-3):341

Previous studies on waters of a streamlet in the Vosges mountains (eastern France) have shown that Sr and rare earth elements (REE) principally originate from apatite dissolution during weathering. However, stream water REE patterns normalized to apatite are still depleted in light REE (LREE, La–Sm) pointing to the presence of an additional LREE depleting process. Speciation calculations indicate that complexation cannot explain this additional LREE depletion. In contrast, vegetation samples are strongly enriched in LREE compared to water and their Sr and Nd isotopic compositions are comparable with those of apatite and waters. Thus, the preferential LREE uptake by the plants at the root–water–soil (apatite) interface might lead to an additional LREE depletion of the waters in the forested catchment. Mass balance calculations indicate that the yearly LREE uptake by vegetation is comparable with the LREE export by the streamlet and, therefore, might be an important factor controlling the LREE depletion in river waters.  相似文献   

Short-term measures for the control of ozone peaks: expertise from CTM simulations     

Fanny Lasry  Isabelle Coll  Sylvain Fayet  Maxime Havre  Robert Vautard 《Journal of Atmospheric Chemistry》2007,57(2):107-134

In Europe, in case of the observation or the forecast of a photochemical event, punctual and local reductions in anthropogenic emissions can be triggered at the regional scale. Although the necessity for the establishment of such measures appears to be justified by bad air quality records over large European cities, individual short-term action plans (STAPs) have been blindly elaborated by regional authorities. Moreover, as they impose industrial and road traffic emission restrictions, these measures have an elevated economical cost. It is consequently crucial to determine their efficiency and potential for ozone peak reduction. The study presented in this paper aims to draw up an expertise on standard European STAPs, through the example of a French Mediterranean city. The objective is to determine and investigate the impact of current STAPs on ozone peak formation and to test ways to optimise their efficiency. In this frame, a set of emission scenarios has been elaborated and tested with the chemistry-transport model CHIMERE on the Berre–Marseille area. Simulations have shown that the tested action plans are not sufficient to eradicate severe ozone peaks and that more drastic restrictions on emissions are required to significantly affect ozone plumes. However, results also showed that the potential for ozone reduction remains small, with a maximum impact of only 5 ppbv for feasible STAPs. Finally, a temporal analysis of the ozone-emission relationship was engaged in order to optimise their application.  相似文献   

Biological interactions between microorganisms in the sea     

M. Aubert  M.J. Gauthier 《Marine Chemistry》1977,5(4-6)

Marine ecosystems, like terrestrial biological communities, are generally considered to depend, regarding their structure and functioning, upon the trophic and sexual relationships between organisms, either “horizontally”, between individuals at the same level, or “vertically”, all the way down the various levels of the food chains. Nevertheless, the functioning of biosystems is mostly governed by their structure, i.e., the qualitative and quantitative distribution of individuals within biocenoses, as well as the relationships with one another and with the environment. Therefore, it is vital to get to know how these connections work in order to outline the main causes of microbiological equilibrium in the sea. Actually, the major problem remains that of communication between individuals in biocenoses. This is a general problem as far as life is concerned, but it proves especially acute when it comes to microbial life because of its importance in the oceanic cycles.Data available in the literature, together with the results of our own studies in this field, led us to the assumption that some of the dissolved organic substances present in seawater might well be responsible for the control of the relationships between species. These substances would be active at various degrees of concentration, after they have been released into the medium by certain species. This theory, already adumbrated by Lucas (1938, 1947, 1955), Nigrelli (1958) and Fontaine (1970) concerning direct relationships between marine species or groups of organisms, was resumed and generalized by M. Aubert (1971) who called these substances “telemediators”.Such chemical communication plays a major role in a variety of fields including sexual behaviour, nutrition and predation, as well as defense mechanisms, mobility and migration.Remote connection of two organisms through a chemical mediation involves a sequence of actions and reactions which raises a number of problems of biochemical microecology. The organism that produces the telemediator must synthesize it — either spontaneously or in an induced way — and release it into the medium, during its active growth or after cell lysis. Next, the mediator is conveyed to the remote receiving organism, which it should reach without being degraded or chemically modified (or after such a modification. Its concentration must remain equal to or higher than its activity threshold. The receptor detects it, with or without absorption, and reacts by modifying its own metabolism or behaviour. This may go as far as causing the receptor the receptor to die. In even more complex situations, another mediator will be synthesized and released into the medium.Theoretical as it may be, such a pattern is a useful guide to explain the microbial interactions in a marine environment. It involves a number of complex microecological phenomena, some phases of which begin to be known. One specific problem is chemoreception in microorganisms, hence chemotaxis. Telemediator activity threshold and turnover in the natural environment must also be investigated.One should also take account of the physical context in which the phenomena take place. For instance, it is a known fact that an important fraction of the bacterial flora in the sea is adsorbed on solid or particulate substrates. Thus, the relationships with which they are concerned are much more probable in a sphere of a few fractions of a millimeter: this emphasizes the significance of the biochemical processes which cause the microorganisms to colonize substrates and to compete with one another in so doing. Another point of interest is how they modify the substrate until they are replaced by higher organisms.In the microbial field, communication between species has been described at various levels. Horizontally, it can take place between different bacteria or between various species of algae. Vertically, it may involve bacteria and planktonic algae, bacteria and protozoa, or algae and zooplanktonic organisms.Besides, the communication may be “positive”, if the mediator enhances the growth of the receiving organism — then, it is used as a source of carbon or nitrogen, or as a growth factor — or “negative” whenever the mediator is toxic (antibiotic, antiseptic or toxin) or induces a lethal metabolic modification in the receiver.In fact, there are various telemediation mechanisms, which correspond to increasing degrees of complexity in the biological systems: a primary mechanism, in which the mediator is synthetized by a species and controls (or modifies) the metabolism of another species in one step, and a secondary mechanism, where the mediator is synthetized by a species, and modifies the metabolism of another species; the latter, in turn, releases a primary mediator which controls the functions of a third species. This might be a longer sequence, involving a higher number of species.If the mechanism becomes cyclic, feedback may occur: as far as we know, such feedback may be either positive or negative ecologically, depending on whether it speeds up or slows down a biological process.A conception of a marine universe whose equilibrium would be controlled by the interaction of organisms within a more or less dense biotic network, with meshes made up of the relationship functions as a whole, is highly suggestive of an homology with cybernetic structures. Then, each marine organism can be considered as a separate functional unit characterized by some particular properties, its functions, which govern its activity. These units are involved in the functioning of complex and varying systems in which they intervene locally to channel up the flow of energy and matter to a given extent and in a given direction.The analogy is still more pronounced as there are feedbacks, which can control various sectors of the system. In a series of studies based on biological systems regulated by various chemical mediators, authors were able to demonstrate that the introduction of varied chemical pollutants into the marine environment entails modifications in the structure of the biological components of seawater and results in either the modification or the destruction of the mediating metabolites or “signals”. The result could be a more or less pronounced ecological drift, that varies according to the activity of the pollutant.  相似文献   

Structure of the cantal strato-volcano, French Central Massif, from electric, magnetotelluric soundings and aeromagnetic data     

M. Aubert  A. Dupis  J.-F. Lenat  J. Roux  G. Senaud 《Journal of Volcanology and Geothermal Research》1982,12(1-2)

The Neogene composite volcano of Cantal is the largest volcano in Europe. Its area (2500 km²) is larger than that of Etna (1200 km²). It was formed between 23 and 3 Ma ago.An aeromagnetic survey, in addition to electrical (ES) and magnetotelluric soundings (MTS) carried out in recent years have made it possible to describe the structure of this volcano.The terrain effects of the various pyroclastics and lavas that make up the volcanic edifice have been computed and removed from the aeromagnetic data; the analysis of the resulting terrain-corrected residual anomalies gives clear evidence for the presence of three internal or deep-seated magnetized bodies which are also revealed by the ES and MTS investigations:

1. (1) The main hypostructure corresponds to a large volcano-tectonic trough filled with low-resistivity (10-5 ωm) and moderately magnetized (1 A/m) volcanic material. However, a part of the trough is filled with non-magnetic formations and it may be an Oligocene sedimentary graben cut across by the present volcanic trough.

2. (2) The hypovolcanic intrusion (monzonites and gabbros) of the Jordanne upper valley was previously known from an outcrop and a borehole (260 m). Its large extent (15 km²) is shown by magnetic study as well as by ES and MTS. According to the magnetic interpretation, its thickness would be 300 m.

3. (3) The nature of the structure inside the Plomb du Cantal is still uncertain. In view of its high resistivity and high magnetization, it may be an unexposed pile of lavas inside the cone or a large intrusion.

In the area where a caldera affects the volcanic cone, ES and MTS underline the importance of a hydrothermal process (propylitization) that lowers and homogenizes the resistivity (p = 30 ω m) of all volcanic rocks and probably that of the uppermost part of the crystallophyllian basement.  相似文献   

Mineral Processing Symposium — Société de l'Industrie Minérale — Toulouse, 1975     

Maxime Brandela 《International Journal of Mineral Processing》1976,3(1):97-100

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Nickel dispersion and enrichment at the bottom of the regolith: formation of pimelite target-like ores in rock block joints (Koniambo Ni deposit,New Caledonia)     

Michel Cathelineau  Benoît Quesnel  Pierre Gautier  Philippe Boulvais  Clément Couteau  Maxime Drouillet 《Mineralium Deposita》2016,51(2):271-282

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Scaling properties of convection-driven dynamos in rotating spherical shells and application to planetary magnetic fields   总被引：3，自引：0，他引：3  

U. R. Christensen  J. Aubert 《Geophysical Journal International》2006,166(1):97-114

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