Integrating habitat concerns into Gordon-Schaefer model

In the Gordon-Schaefer model (G-S model), widely used to design fisheries management policy, only resource stock dynamic is considered and carrying capacity is constant. We propose an extension to the G-S model that incorporates the dynamics of carrying capacity as an indicator of dynamics of the marine habitats. The study yields two main findings. First, we demonstrate that habitats matter, by showing that the main outcomes of the G-S model are dramatically modified if habitats are included in the analysis. Second, through a heuristic model and simulations, we show, for the first time, that our extended model provides an appropriate framework to analyse the putative contribution of MPAs and ARs. The model presented in this article opens the way to a better understanding of the benefits of MPAs and ARs, as well as other habitat protection policies.Bioeconomics, Gordon-Schaefer model, Marine habitats, Artificial reefs

The hydrogen isotopic composition and water content of southern Pacific MORB: A reassessment of the D/H ratio of the depleted mantle reservoir

In this paper, we re-investigate the isotopic composition of hydrogen in MORB and the possible effects of contamination on δD and water content. A suite of 40 N-MORB from the Pacific–Antarctic ridge, far from any hotspot, was analyzed for chlorine content by electron microprobe and for water content and δD with silica tubes. Cl concentrations (from 29 to 2400 ppm) indicate widespread contamination, more intense with faster spreading rates, while water contents (from 840 to 7800 ppm) are mainly controlled by igneous processes. δD values range from −76 to −48‰−48‰, with an average value of −61‰−61‰. The lack of correlation between Cl content and either H_2O/Ce or δD indicate that contamination has a negligible effect on δD for our samples, which is therefore characteristic of the mantle below the Pacific–Antarctic ridge. We suggest that the 20‰ lower δD value reported for the North Pacific and North Atlantic is highly unlikely from geodynamical arguments. We propose that the convecting mantle is characterized by a δD of −60±5‰−60±5‰, as supported by the most recent data from North Atlantic N-MORB

Анаэробные неклостридиальные флегмоны таза: современный взгляд на проблемы хирургического лечения

Проанализированы современные литературные источники по проблеме хирургического лечения анаэробных неклостридиальных флегмон таза, выявлены дискуссионные и требующие дальнейшего изучения вопросы как оперативного, так и послеоперационного местного лечения патологического процесса.Проаналізовано сучасні літературні джерела з проблеми хірургічного лікування анаеробних неклостридіальних флегмон тазу, виявлено дискусійні питання як оперативного, так і післяопераційного місцевого лікування патологічного процесу, що потребують подальшого вивчення.Contemporary literature on the problem of surgical treatment of anaerobic nonclostridial cellulitis of the pelvis was analyzed. Disputable questions and those requiring research concerning both operative and postoperative topical treatment of the pathological process were revealed

Nitrogen isotopic evolution of carbonaceous matter during metamorphism: Methodology and preliminary results

Nitrogen content and isotopic composition of carbonaceous-rich metasediments were determined by on-line and sealed-tube combustion using ultra-high vacuum line and static mass spectrometer adapted to analyse nitrogen nanomoles. Accurate measurements showed that nitrogen amount released by on-line combustion technique was underestimated to various extents. As a result, the nitrogen isotopic composition was not correctly determined. In contrast, sealed-tube combustion appeared to yield the most reproducible and accurate measurements, except for nitrogen depleted carbonaceous matter (semi-graphite to graphite transition) containing less than around 60 ppm of nitrogen, which were contaminated during their extraction from the rock. In view of that, a preliminary sealed-tube investigation of the organic nitrogen content and isotopic composition in a homogenous series of low-grade metasediments was undertaken: in spite of an important nitrogen loss, the carbonaceous matter nitrogen isotopic composition remains about the same during the meta-anthracite and semi-graphitisation stages. Inferences on the process of organic nitrogen mineralization during carbonaceous matter metamorphism can be drawn and several paleo-biogeochemical implications envisaged

A comprehensive study of noble gases and nitrogen in Hypatia, a diamond-rich pebble from SW Egypt

This is a follow-up study of a work by Kramers et al. (2013) on an unusual diamond-rich rock found in the SW side of the Libyan Desert Glass strewn field. This pebble, called Hypatia, is composed of almost pure carbon. Transmission Electron Microscopy and X-ray diffraction results reveal that Hypatia is made of defect-rich diamond containing lonsdaleite and deformation bands. These characteristics are compatible with an impact origin on Earth and/or in space. We analyzed concentrations and isotopic compositions of all five noble gases and nitrogen in several mg sized Hypatia samples. These data confirm that Hypatia is extra-terrestrial. The sample is rich in trapped noble gases with an isotopic composition close to the meteoritic Q component. 40Ar/36Ar ratios in individual steps are as low as 0.4. Concentrations of cosmic-ray produced 21Ne correspond to a nominal cosmic-ray exposure age of ca. 0.1 Myr if produced in a typical m-sized meteoroid. Such an atypically low nominal exposure age suggests high shielding in a considerably larger body. In addition to the Xe-Q composition, an excess of radiogenic 129Xe (from the decay of extinct 129I) is observed (129Xe/132Xe = 1.18 +/- 0.03). Two N components are present, an isotopically heavy component ({\delta}15N = +20 permil) released at low temp. and a major light component ({\delta}15N = -110 permil) at higher temp. This disequilibrium in N suggests that the diamonds in Hypatia were formed in space. Our data are broadly consistent with concentrations and isotopic compositions of noble gases in at least three different types of carbon-rich meteoritic materials. However, Hypatia does not seem to be related to any of these materials, but may have sampled a similar cosmochemical reservoir. Our study does not confirm the presence of exotic noble gases that led Kramers et al. to propose that Hypatia is a remnant of a comet that impacted the Earth

Incorporating Habitat Dynamics into Bioeconomic Model of Fishery. Application to Artificial Reefs

In this paper the emphasis is put on an important aspect of renewable resource use that was disregarded until now. It is the evolution of environmental carrying capacity which is traditionally interpreted as a maximal population level that can be supported by the environment (or by habitats of which it consists). Hence we adapt the Gordon-Schaefer model with constant carrying capacity by incorporating time-dependent carrying capacity that determines the state of habitats. They are subject to some biological processes (habitat rehabilitation) as well as to human aggressions (in particular habitat degradation due to fishing). Based on the developed model, we reassess the recommendations considered as a benchmark for resource managers until recently. Under simple hypotheses on the form of habitat (carrying capacity) dynamics, the current study has shown the importance of the latter for the design of management tools. When dynamic patterns of habitats are not taken into account, fishery recommendations based on Gordon-Schaefer model can be aberrant and lead to the collapse of the fishery. The presented model allows not only to enrich the design of management tools but also to assess the performance of artificial reefs, a promising ecosystem-based tool widely used in some coastal areas. The economic benefits of artificial reefs are still not well studied and represent a challenge to take up. Since artificial reefs are conceived as replacement for natural habitats, they assume the same role as these latter. Therefore the structure of our model seems appropriate to evaluate this particular management tool.Keywords: Modeling and Economic Theory, Fisheries Modeling, Fisheries Economic

Regional patterns in the paragenesis and age of inclusions in diamond, diamond composition, and the lithospheric seismic structure of Southern Africa

Abstract The Archean lithospheric mantle beneath the Kaapvaal -Zimbabwe craton of Southern Africa shows F 1% variations in seismic P-wave velocity at depths within the diamond stability field (150 -250 km) that correlate regionally with differences in the composition of diamonds and their syngenetic inclusions. Seismically slower mantle trends from the mantle below Swaziland to that below southeastern Botswana, roughly following the surface outcrop pattern of the Bushveld-Molopo Farms Complex. Seismically slower mantle also is evident under the southwestern side of the Zimbabwe craton below crust metamorphosed around 2 Ga. Individual eclogitic sulfide inclusions in diamonds from the Kimberley area kimberlites, Koffiefontein, Orapa, and Jwaneng have Re -Os isotopic ages that range from circa 2.9 Ga to the Proterozoic and show little correspondence with these lithospheric variations. However, silicate inclusions in diamonds and their host diamond compositions for the above kimberlites, Finsch, Jagersfontein, Roberts Victor, Premier, Venetia, and Letlhakane do show some regional relationship to the seismic velocity of the lithosphere. Mantle lithosphere with slower P-wave velocity correlates with a greater proportion of eclogitic versus peridotitic silicate inclusions in diamond, a greater incidence of younger Sm -Nd ages of silicate inclusions, a greater proportion of diamonds with lighter C isotopic composition, and a lower percentage of low-N diamonds whereas the converse is true for diamonds from higher velocity mantle. The oldest formation ages of diamonds indicate that the mantle keels which became continental nuclei were created by middle Archean (3.2 -3.3 Ga) mantle depletion events with high degrees of melting and early harzburgite formation. The predominance of sulfide inclusions that are eclogitic in the 2.9 Ga age population links late Archean (2.9 Ga) subduction-accretion events involving an oceanic lithosphere component to craton stabilization. These events resulted in a widely distributed younger Archean generation of eclogitic diamonds in the lithospheric mantle. Subsequent Proterozoic tectonic and magmatic event

Modélisation déterministe des ressources naturelles renouvelables exploitées: applications en halieutique (zone artisanale/industrielle, réserve de pêche)

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