Stability of the Triangular Libration Points in the Unrestricted Planar Problem of a Symmetric Rigid Body and a Point Mass

In papers (Godziewski and Maciejewski, 1998a, b, 1999), we investigate unrestricted, planar problem of a dynamically symmetric rigid body and a sphere. Following the original statement of the problem by Kokoriev and Kirpichnikov (1988), we assume that the potential of the rigid body is approximated by the gravitational field of a dumb-bell. The model is described in terms of a 2D Hamiltonian depending on three parameters.In this paper, we investigate the stability of triangular equilibria permissible by the dynamics of the model, under the assumption of low-order resonances. We analyze all resonances of order smaller than four, and we examine the stability with application of theorems by Markeev and Sokolsky. These are the possible following cases: the non-diagonal resonance of the first order with two null characteristic frequencies (unstable); resonances of the first order with one nonzero frequency (diagonal and non-diagonal, stable and unstable); the second-order resonance, which is non-diagonal and stable, and the third-order resonance which is generically unstable, except for three points in the parameters' space, corresponding to stable equilibria.We discuss a perturbed version of Kokoriev and Kirpichnikov model, and we find that if the perturbation is small and depends on the coordinates only, the triangular equilibria persist, except if for the unperturbed equilibria the first-order resonance occurs. We show that the resonances of the order higher than two are also preserved if the perturbation acts.     

étude expérimentale de la couche limite interne associée à la brise de mer

Résumé Sur un site de la côte méditerranéenne française, à l'aide d'un avion spécialement équipé pour les mesures atmosphériques et d'une installation fixe (pylône de 50 m), ont été observées, dans des cas de brise de mer, des caractéristiques essentielles de la couche limite interne à caractère convectif formée à partir de la ligne côtière au sein d'un écoulement stable: particularités du champ de vitesse, discontinuité du champ thermique, contraste des flux verticaux, turbulence induite dans la couche stable. Pour compenser le caractère pseudo-eulérien des mesures par avion, les données de plusieurs expériences menées dans des conditions semblables ont été regroupées: on établit ainsi un schéma moyen du sommet de la couche interne pouvant être exprimé comme une puissance 0,4 de la distance à la côte.

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The sea-breeze has been observed at a site along the French Mediterranean coast, using an aircraft specially fitted for atmospheric instruments and a fixed 50 m tower. The essential characteristics of the convective internal boundary layer, formed downwind from the coast in the primarily stable flow include the following: wind field distortions, a thermal field discontinuity, contrasts in vertical fluxes, turbulence induced in the stable layer. In order to compensate for the pseudo-eulerian feature of aircraft measurements, the data of several experiments obtained in similar circumstances have been grouped: this yields a height for the internal layer top, which can be expressed as the 0.4 power of the fetch.

     

Differentiation of the sensitivity to copper and cadmium in different life stages of a copepod

Copper is more toxic to all life stages of the copepod Tisbe than cadmium. The most sensitive life stage of Tisbe to both copper and cadmium is the one-day-old nauplius. The resistance of larval stages of Tisbe increases with age (one-day-old nauplii 48h $\text{lc}{}_{50}\text{=0.3142}$ mg Cu l^?1. and 0.5384 mg Cd l^?1, 0.3415 mg Cu l^?1. and 0.645 mg Cd l^?1. for five-days-old nauplii and 0.5289 mg Cu l^?1. and 0.9061 mg Cd l^?1. for ten-days-old nauplii. The two reproductive stages of Tisbe tested (females with ovigerous bands and females bearing the first ovigerous sac) demonstrated an increased sensitivity to metals and proved more sensitive than the ten-days-old copepodids (only females with ovigerous bands had a similar sensitivity to copper with the ten-days-old copepodids).     

Synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the Mediterranean region

Land-sea climatic proxies have been obtained from the Last Glacial section of IMAGES core MD95-2043 (western Mediterranean Sea). Vegetation and alkenone derived SST curves indicate rapid (~150 years) and synchronous terrestrial and marine climatic changes, paralleling the Dansgaard-Oeschger (D-O) climatic variability over Greenland. This frequency of climate change can be related to shifts between the two modes of operation of the North Atlantic Oscillation (NAO). Transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during Heinrich events (HEs) in comparison with other D-O stadials. The development and persistence of both Scandinavian and Atlantic Mobile Polar Highs over southwestern Europe may explain the extreme cooling (~10 °C) and dryness (400 mm) during Heinrich events 5 and 4 in the Mediterranean region. Comparison of the results of core MD95-2043 with similar climatic data from IMAGES core MD95-2042, located off Portugal, indicates that thermal and precipitation gradients occurred between the Mediterranean and the Atlantic sides of Iberia within HEs. HEs 4 and 5 are associated with more humid conditions in the Atlantic (by 200 mm) than in the Mediterranean site, as is the case at the present time. This comparison also illustrates the different behaviour of these areas during the D-O stadials. In contrast with the Mediterranean site, the Atlantic site shows similar precipitation and temperature drops for all the D-O stadials, including those related to the HEs. Here we propose the operation of different Mobile Polar Highs (MPH) as the driving mechanism for this difference in behaviour between the Atlantic and Mediterranean sides of Iberia. HEs are related to a stronger influence of the Scandinavian MPH, forcing a severe aridification and cooling of the full Iberian Peninsula. The Atlantic MPH may have been dominant during the other stadials, which would preferentially affect Southwestern Iberia.     

Premières datations de feux holocènes dans les Monts de Saint-Guilhem-le-Désert (Hérault,France), contribution à l'histoire de la forêt relique de Pinus nigra Arnold ssp Salzmanni (Dun.) Franco

The charcoal discovery in the soils and sediments of the relic forest of Pinus nigra ssp Salzmanni near Saint-Guilhem-le-Désert allows us to establish a chronology of Holocene fires. Their origin dates from the Middle Holocene, but they are especially significant after the construction of the medieval abbey during the 9th century. The original pine plantation was heterogeneous, with another pine, Pinus sylvestris, which has now been eradicated. Changes in the fire modes have been observed, recent human fires being generalized, which resulted in a significant regression of the forest cover, which was replaced by box-tree formations. To cite this article: J.-L. Vernet et al., C. R. Geoscience 337 (2005).     

地学信息基础数据库系统—GIS-dB3的基本结构

本文介绍了立足于微机和超级微机上的地学信息基础数据库管理系统的基本结构。它采用通用的中西文关系数据库dBASEⅢ编译语言,统一管理地学信息的质量、数量、时间、空间以及信息传输等5个方面的特性数据,以FORTRAN和BASCI编译等系统软件进行数据处理及图形的显示和绘出,即采用各系统软件所长组成了一个地学的基础系统。该系统的空间特性数据中的“边”是采用超图(HYPERGRAPH)的概念组织的。它具有原中西文dBASEⅢ的操作方便、资源广泛,一定的分类统计能力,对各软件界面“友好”的特点,并具有可广泛提供各合理子集数据并使之动态成库,足够大的的分类数及库容和一定的数据独立性的特点。     

Hydrothermal manganese oxide deposits from Galapagos mounds,DSDP Leg 70, hole 509B and “Alvin” dives 729 and 721

During DSDP Leg 70, a 1.60 m thick manganese oxide layer was sampled in hole 509B. This deposit is formed of alternating layers of hard plates of pure todorokite, about 2 mm thick, and of a more powdery material deeply impregnated with manganese oxide, about 3 mm thick. A SEM study of the plates and the associated powder shows that the powdery material is a transformation of a pre-existing sediment, while the plates are a direct precipitation from a hydrothermal solution.The uranium series disequilibrium method was used to determine the ages of the plates. They are found to be in good chronological sequence and in accordance with the sedimentation rate of the area (4.9 cm/10³ years) which implies that they have been formed at the sediment-seawater interface during a pulsed injection of hydrothermal solution. The powder presents systematically an “older age” which is explained by a slowing down of the injection while the normal sediment settles; the older age is due to the²³⁰Th excess of the sediment.     

Heavy metals in sediments as evidence for recent pollution and quasi-estuarine processes: an example from Lake Druzno,Poland

This article presents the results of a geochemical investigation of sediments from Lake Druzno (northern Poland), a reservoir fed by freshwater from the catchment, with periodic input of brackish water from Vistula Lagoon. This study analyzed the spatial variation in heavy metal content in surface sediments as well as the temporal changes in metal content in two sediment cores dated using the ²¹⁰Pb method. In the surface sediments, the highest metal concentrations were recorded in the northern part of the lake, with lower concentrations in the central and southern parts. Absolute values of metal concentrations in the cores were low, but normalization with respect to Al showed an increase during the second half of the 20th century. Mean enrichment factors (EF) in sediments from the second half of the 20th century ranged from insignificant (1–1.2) for Fe to (1.55–3.3) for Cu, Cd, Pb and Zn. The sediments deposited before 1950 had lower EF values (>1.5) and had low variability. Results from both the surface sediments and the cores indicate that the main source of lake pollution is brackish water intrusion from the Vistula Lagoon via the contaminated River Elbląg.     

High-resolution atmospheric forcing for regional oceanic model: the Iroise Sea

This study was aimed at modeling, as realistically as possible, the dynamics and thermodynamics of the Iroise Sea by using the Model for Applications at Regional Scale (MARS), a regional ocean 3D model. The horizontal resolution of the configuration in use is 2 km with 30 vertical levels. The 3D model of the Iroise Sea is embedded in a larger model providing open boundary conditions. As regards the atmospheric forcing, the originality of this study is to force the regional ocean model with the high-resolution (6 km) regional meteorological model, Weather Research and Forecasting (WRF). In addition, as the air surface temperature is highly sensitive to the sea surface temperature (SST), this regional meteorological model is improved by taking into account a regional climatologic SST to compute meteorological parameters. By allowing a better coherence between the SST and the temperature of the atmospheric boundary layer while giving a more realistic representation of heat fluxes exchanged at the air/sea interface, this forcing constitutes a noticeable improvement of the Iroise Sea modeling. The different sensitivity tests discussed here pinpoint the importance of entering, in WRF, SST data of sufficiently high quality before the computation of meteorological forcing when the aim is a study of dynamics and thermodynamics far away from the coast. On the other hand, when the target is the reproduction of coastal small-scale features in Iroise Sea modeling, the resolution of the meteorological forcing and the quality of SST are both paramount. The simulation of reference was carried out throughout the Summer and Autumn of year 2005 to allow comparisons with a campaign of surface current measurements by high-frequency radars conducted at the same period.     

Heat contamination in groundwater sourced from heat pump for heating in Bratislava (Slovakia)’s historic centre

The aim of the study is to evaluate the warming effect (thermal contamination) of city centres with high building density. This phenomenon has a number of scientific and practical implications. The case study was conducted in Bratislava (Slovakia), in the geological environment of alluvial gravels of the Danube River, where a permanent warming of the subsurface in the city centre is experienced, which is mainly affected by high building density and underground utilities. Thanks to this thermal contamination, the heat pumps efficiency is greater in winter, while in summer, their effectiveness is lower. Economically, this negative phenomenon in the case of heat pumps has a positive effect, since it increases energy efficiency during the heating period. This phenomenon is not universal and depends on the specific boundary conditions of the geological settings and hydrogeological conditions.