The magnetohydrodynamic turbulent cascade in the ecliptic solar wind: Study of Ulysses data

The occurrence of a nonlinear turbulent energy cascade in solar wind plasma has been recently established through the observation of an exact law from spacecraft measurements. The main results obtained in the fast, polar wind measured by Ulysses spacecraft are reviewed here. In particular, the turbulent cascade is seen as the mean to provide the energy necessary for the local heating in the non-adiabatic expansion of the solar wind. The importance of the density fluctuations in enhancing the turbulent energy transport is also evidenced. The ecliptic wind data measured by Ulysses are studied here in the same framework. This has been done by separating fast and slow streams, in order to avoid mixing of different physical conditions. The results further support the need for separate analysis of the two types of wind.     

Bearing capacity of pile groups under vertical eccentric load

The paper deals with the problem of the bearing capacity of pile groups under vertical eccentric load. Widespread practice is to consider the achievement of the axial capacity on the outermost pile as the ultimate limit state of the pile group. However, this approach neglects the ductility of the foundation system and may be thereby overconservative. With the aim of proposing an alternative and more rational approach, a novel formulation for interaction diagrams based on theorems of limit analysis is presented and discussed. The methodology is applicable to the general case of groups of unevenly distributed, dissimilar piles. Piles’ connections to the pile cap are modeled as either hinges or rigid-plastic internal fixities. An application example to a slender structure is also provided, showing that the proposed approach can lead to significant advantages over the traditional design.

     

Biomass composition and methods for the determination of metabolic reserve polymers in phototrophic sulfur bacteria

To study nutrient fluxes within aquatic ecosystems, the synthesis of biomass and of various storage polymers has been analysed in samples from a meromictic alpine lake. Methods are described for the quantitative determination of whole cell biomass, glycogen, polyhydroxyalkanoates (PHA) and sulfur. Methods were adapted to conditions present in natural environments and tested with samples from blooms of Chromatiaceae and with corresponding laboratory cultures. Dried bacterioplankton-biomass has been analyzed for sulfur, glycogen and polyhydroxyalkanoates, and after complete oxidation for SO ₄ ^2- , NO ₃ ^- and HPO ₄ ^2- . The average elemental composition of biomass from phototrophic sulfur bacteria, depleted of sulfur and carbon storage compounds, was C₃₈₀H₅₈₀O₁₅₃N₆₇P₃S_2.5M, where M stands for the content of the remaining minor elements. C, H, O, N, P and S accounted for 86.7% of the total dry mass. Storage sulfur in natural populations was equivalent to 2.5% to 13.5% of the dry mass; its content varied by 80% within a diurnal cycle. Glycogen contents fluctuated by approximately 50%; they accounted for 7.5% to 15.2% of the dry cell mass. The total content of reserve materials per cell never exceeded 30% of the dry mass. PHA had not been found in appreciable amounts in cells harvested from the natural lake habitat. Under certain conditions in the laboratoryChromatium okenii could be induced, however, to produce polyhydroxyalkanoates. Sulfur, glycogen and PHA contents of 33, 26 and 11%, respectively, were achieved under laboratory-culture conditions. Cells with up to 60% of their dry mass consisting of reserve materials can be obtained under selected laboratory conditions.     

Comparaison au moyen de la lysotypie entre souches d'Aeromonas de pisciculture et souches isolées de l'homme

The spreading of bacteria of the genusAeromonas in intensive fish rearing tanks was analyzed during one year. Lysotyping has established epidemiologic correlations between the strains ofAeromonas isolated from the aquatic environment and those of clinical (human) origin.

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Dédié à Wolfgang Geiger     

A strategy for the determination of the dielectric permittivity of a lossy soil exploiting GPR surface measurements and a cooperative target

In this paper we deal with an indirect measure of the dielectric permittivity of the soil starting from GPR surface data collected on a buried “cooperative” target, meant as an object buried on purpose and whose extent is known a-priori. This target is exploited in order to achieve, from its image obtained from a suitable GPR data processing, an indirect measure of the dielectric permittivity of the embedding soil. GPR data processing is based on a linear microwave tomographic approach funded on the Born Approximation. Using this Born approach on two-dimensional inversion tests, we investigate the effect of the soil's electrical conductivity and permittivity on this indirect measure and demonstrate that the electrical field scattered by a spot-like buried object permits an accurate estimation of the soil permittivity even when no information of the soil conductivity is available.     

Integrated Geophysical Investigations at the Greek Kamarina Site (Southern Sicily,Italy)

Kamarina, located in southern Sicily (Italy), was an important Greek colony since its foundation in the sixth century BC. Archaeological excavations, carried out since the twentieth century, uncovered only limited portions of the site so far. Despite the importance of the Greek colony, the presence of remarkable buildings that archaeologists expected to bring to light has not found fully correspondence in the archaeological excavations. Consequently, the integrated geophysical prospection carried out in the study area is aimed to support and address the future archaeological investigations. After the photographic and thermographic survey obtained by an unmanned aerial vehicle, we performed a systematic survey through ground magnetic and GPR methods over an area of 6200 m². The acquisition procedures have been optimized in order to get the best results combining high resolution and elevated speed of acquisition. The results derived from the three geophysical techniques have been conveniently combined by means of a cluster analysis, allowing us to clearly identify a series of buried archaeological features. Because of their geometrical characteristics, often in good agreement with the spatial arrangement of the archaeological remains at the surface, these buried archaeological features can be interpreted as roads, walls, or buildings foundations in which the various construction phases of the city can be clearly recognized. The integrated approach has proven to be essential for a robust interpretation of the archaeogeophysical investigation.