Characterization of wrench tectonics from dating of syn- to post-magmatism in the north-western French Massif Central

This work establishes the relative timing of pluton emplacement and regional deformation from new dating and structural data. (1) Monazite and (2) zircon dating show Tournaisian ages for the Guéret granites [Aulon granite 352 ± 5 Ma (1), 351 ± 5 Ma (2) and Villatange tonalite 353 ± 6 Ma (1)] and Viseo-Namurian ages for the north Millevaches granites [Chavanat granite 336 ± 4 Ma (1), Goutelle granite 336 ± 3 Ma (1), Royère granite 323 ± 2 Ma (1) and 328 ± 6 Ma (2), Courcelles granite 318 ± 3 Ma (1)]. The Guéret and Millevaches granites are separated by the N110 Arrènes–la Courtine Shear Zone (ACSZ), composed from West to East by the Arrènes Fault (AF), the North Millevaches Shear Zone (NMSZ) and the la Courtine Shear Zone (CSZ), respectively. Tournaisian Guéret granites experienced a non-coaxial dextral shearing (NMSZ) recorded by the Villatange granite while the Aulon granite (Guéret granite) cuts across this dextral shear zone which thus stopped shearing during Tournaisian time. Visean to Namurian Millevaches granites experienced a coaxial deformation. Therefore, low displacements along the NMSZ and the CSZ occurred at the emplacement time of Chavanat and Pontarion-Royère granites (336–323 Ma). The structural analyses of Goutelle granite emphasizes a deformation related to the dextral Creuse Fault System (CFS) oriented N150–N160. From 360 to 300 Ma, the Z strain axis is always horizontal inferring a wrench setting for these granite emplacements. During this tectonic evolution, the Argentat zone acted as a minor normal fault and is related with a local Middle Visean (340–335 Ma) syn-orogenic extension on the western border of the Millevaches massif.     

Transaction links through cities: ‘decision cities’ and ‘service cities’ in outsourcing by leading Brazilian firms

Most world city studies focus on where the provision of advanced producer services takes place, but in this study the location of the service clients are also taken into account. Production-service transactions are identified as links between ‘service city’ and ‘decision city’ (client HQ) and classified as intra-city (where a firms uses local (same city) services) and inter-city which may be domestic or foreign depending on whether the client uses services in or out of the country. Sampling the leading firms in Brazil, 218 transaction links are described and analysed in terms of cities, firm sectors, ownership and market. The analyses are used to inform a rereading of gateway city functions that takes into account the concentration/dispersal nexus in economic globalization. Thus, whereas the dominance of Sao Paulo in the Brazilian economy is confirmed, this is not interpreted as a simple gateway function with this one city ‘articulating’ the national economy into the world economy. A much more complex situation is revealed with by-passing of the gateway also much in evidence. The conclusion is that this shows concentration and dispersion of economic activity happening simultaneously in Brazil.     

A design procedure for tied braced frames

The paper deals with the analysis of the seismic behaviour and design of tied braced frames (TBFs). The behavioural properties of TBFs are described and a comparison drawn with standard eccentrically braced frames. A design procedure is then proposed that aims to achieve optimal collapse seismic behaviour, i.e. a global collapse mechanism characterized by uniform plastic rotations of links. The procedure is based on the displacement‐based approach so as to achieve direct and efficient control of the peak ground acceleration of collapse. Applications are carried out on systems with different numbers of storeys and lengths of links to obtain confirmation of the accuracy of the design hypotheses and methodologies. Copyright © 2007 John Wiley & Sons, Ltd.     

Attenuation tomography: An application to gas-hydrate and free-gas detection

We estimate the quality factor (Q) from seismic reflections by using a tomographic inversion algorithm based on the frequency‐shift method. The algorithm is verified with a synthetic case and is applied to offshore data, acquired at western Svalbard, to detect the presence of bottom‐simulating reflectors (BSR) and gas hydrates. An array of 20 ocean‐bottom seismographs has been used. The combined use of traveltime and attenuation tomography provides a 3D velocity–Q cube, which can be used to map the spatial distribution of the gas‐hydrate concentration and free‐gas saturation. In general, high P‐wave velocity and quality factor indicate the presence of solid hydrates and low P‐wave velocity and quality factor correspond to free‐gas bearing sediments. The Q‐values vary between 200 and 25, with higher values (150–200) above the BSR and lower values below the BSR (25–40). These results seem to confirm that hydrates cement the grains, and attenuation decreases with increasing hydrate concentration.     

A comparative analysis of three habitat suitability models for commercial yield estimation of Tapes philippinarum in a North Adriatic coastal lagoon (Sacca di Goro, Italy)

Habitat Suitability (HS) models have been extensively used by conservation planners to estimate the spatial distribution of threatened species and of species of commercial interest. In this work we compare three HS models for the estimation of commercial yield potential and the identification of suitable sites for Tapes philippinarum rearing in the Sacca di Goro lagoon (Italy) on the basis of six environmental factors. The habitat suitability index (HSI) is based on expert opinion while the habitat suitability conditional (HSC) is calibrated on observational data. The habitat suitability mixed (HSM) model is a two-part model combining expert knowledge and regression analysis: the first component of the model uses logistic regression to identify the areas in which clams are likely to be present; the second part applies the same parameter-specific suitability functions of the HSI model only in the areas previously identified as productive by the logistic component.The HS models were validated on an independent data set and estimates of potential yield of the Goro lagoon were compared. The effectiveness of the three approaches is then discussed in terms of predicted yield and identification of suitable sites for farming.     

On the MHD Acceleration of Astrophysical Jets

We present a 2.5D magnetohydrodynamic (MHD) simulation of the acceleration of a collimated jet from a magnetized accretion disk. We employ a MHD Adaptive Mesh Refinement (AMR) code (FLASH—University of Chicago). Thanks to this tool we can follow the evolution of the system for many dynamical timescales with a high-spatial resolution. Assuming an initial condition in which a Keplerian disk, thus with no accretion motions, is threaded by a uniform poloidal magnetic field, we show how both the accretion flow and the acceleration of the outflow occur, and we present in detail which are the forces responsible for the jet launching and collimation. Our simulation also shows how the collimating forces due to the self-generated toroidal magnetic field can produce some peculiar knotty features.     

Decomposition rate and invertebrate colonization of seagrass detritus along a hydrodynamic gradient in a Mediterranean coastal basin: The Stagnone di Marsala (Italy) case study

Seagrass leaf litter decomposition is a key component of marine carbon flow driven by both biotic and abiotic factors, including water movement. In this study, we analyse Posidonia oceanica litter decomposition and invertebrate colonization in three sites with different hydrodynamics in a coastal basin. Litterbags were put on the sea bed along a gradient of distance from the open sea, implying a different level of water exchange. Leaf litter mass loss and carbon and nitrogen concentration were analysed, and density and biomass of benthic invertebrates colonizing litterbags were recorded after 3, 7, 14, 47, 101, 152 and 221 days. Results showed that in the most sheltered site, the leaf litter decomposition rate, the invertebrate density and biomass and the detrital carbon release were the lowest. The reduction of the decomposition rates of seagrass leaves in the site characterized by low hydrodynamic forces may promote organic matter burial and carbon stocks, emphasizing the role of coastal basins such as ponds and lagoons as sinks of carbon and the important role of seagrass detritus in the Blue Carbon global balance.     

The Influence of Aircraft Speed Variations on Sensible Heat-Flux Measurements by Different Airborne Systems

Crawford et al. (Boundary-Layer Meteorol 66:237–245, 1993) showed that the time average is inappropriate for airborne eddy-covariance flux calculations. The aircraft’s ground speed through a turbulent field is not constant. One reason can be a correlation with vertical air motion, so that some types of structures are sampled more densely than others. To avoid this, the time-sampled data are adjusted for the varying ground speed so that the modified estimates are equivalent to spatially-sampled data. A comparison of sensible heat-flux calculations using temporal and spatial averaging methods is presented and discussed. Data of the airborne measurement systems $\hbox {M}^2\hbox {AV}$ , Helipod and Dornier 128-6 are used for the analysis. These systems vary in size, weight and aerodynamic characteristics, since the $\hbox {M}^2\hbox {AV}$ is a small unmanned aerial vehicle (UAV), the Helipod a helicopter-borne turbulence probe and the Dornier 128-6 a manned research aircraft. The systematic bias anticipated in covariance computations due to speed variations was neither found when averaging over Dornier, Helipod nor UAV flight legs. However, the random differences between spatial and temporal averaging fluxes were found to be up to 30 % on the individual flight legs.