Abundances of Iron-Binding Photosynthetic and Nitrogen-Fixing Proteins of Trichodesmium Both in Culture and In Situ from the North Atlantic

Marine cyanobacteria of the genus Trichodesmium occur throughout the oligotrophic tropical and subtropical oceans, where they can dominate the diazotrophic community in regions with high inputs of the trace metal iron (Fe). Iron is necessary for the functionality of enzymes involved in the processes of both photosynthesis and nitrogen fixation. We combined laboratory and field-based quantifications of the absolute concentrations of key enzymes involved in both photosynthesis and nitrogen fixation to determine how Trichodesmium allocates resources to these processes. We determined that protein level responses of Trichodesmium to iron-starvation involve down-regulation of the nitrogen fixation apparatus. In contrast, the photosynthetic apparatus is largely maintained, although re-arrangements do occur, including accumulation of the iron-stress-induced chlorophyll-binding protein IsiA. Data from natural populations of Trichodesmium spp. collected in the North Atlantic demonstrated a protein profile similar to iron-starved Trichodesmium in culture, suggestive of acclimation towards a minimal iron requirement even within an oceanic region receiving a high iron-flux. Estimates of cellular metabolic iron requirements are consistent with the availability of this trace metal playing a major role in restricting the biomass and activity of Trichodesmium throughout much of the subtropical ocean

Combining autocracy and majority voting: the canonical succession rules of the Latin Church

The autocratic turn of the Latin Church in the XI-XIII century, a reaction to the secular power interferences, concentrated the decision-making power in the hands of the top hierarchy, and finally in the hands of the pope. A fundamental step was the change and the constitutionalisation of the procedures for leadership replacement, which were open successions where the contest for power was governed by elections. The autocratic reform limited the active electorate to the clergy only and gradually substituted the episcopal elections by the pope’s direct appointment. Besides, the voting rules changed from unanimity to the dual principle of maioritas et sanioritas (where the majority was identified with the greater part by number and wisdom) and finally to the numerical rule of qualified majority. This evolution aimed at preserving the elections from external interferences and at eliminating the elements of arbitrariness. The most important succession, the papal election, was protected by institutionalising a selectorate and its decision-making rules. The selectorate and the elections did not insert accountability and representation mechanisms but only protected the quality of the autocratic leadership and its autonomy

Global-scale variations of the ratios of carbon to phosphorus in exported marine organic matter

The ratio of carbon (C) to phosphorus (P) in marine phytoplankton is thought to be constant throughout the worlds'oceans. Known as the Redfield ratio, this relationship describes the links between carbon and phosphorus cycling and marine ecosystems. However, variations in the stoichiometry of phytoplankton have recently been identified, in particular strong latitudinal variability. Here we assess the impact of this variability in the C:P ratio of biomass on the C:P ratio of organic matter that is exported to the deep ocean using a biogeochemical inverse-model based on a data-constrained ocean circulation model and a global database of dissolved inorganic carbon and phosphate measurements. We identify global patterns of variability in the C:P ratios of exported organic matter, with higher values in the nutrient-depleted subtropical gyres, where organic matter export is relatively low, and lower ratios in nutrient-rich upwelling zones and high-latitude regions, where organic matter export is high. This suggests that total carbon export is relatively constant throughout the oceans, in agreement with recent estimates of carbon fluxes. We conclude that the latitudinal patterns of C:P in exported organic matter are consistent with the large-scale stoichiometric variations in phytoplankton C:P. We suggest that a future expansion of nutrient-depleted waters could result in a shift to more efficient C export that compensates for the expected decline in productivity

Effects of nutrient enrichment on surface microbial community gene expression in the oligotrophic North Pacific Subtropical Gyre

Marine microbial communities are critical for biogeochemical cycles and the productivity of ocean ecosystems. Primary productivity in the surface ocean is constrained by nutrients which in part are supplied by mixing with deeper water. Little is known about the time scales, frequency, or impact of mixing on microbial communities. We combined in situ sampling using the Environmental Sample Processor and a small-scale mixing experiment with lower euphotic zone water to determine how individual populations respond to mixing. Transcriptional responses were measured using the MicroTOOLs (Microbiological Targets for Ocean Observing Laboratories) microarray, which targets all three domains of life and viruses. The experiment showed that mixing substantially affects photosynthetic taxa as expected, but surprisingly also showed that populations respond differently to unfiltered deep water which contains particles (organisms and detritus) compared to filtered deep water that only contains nutrients and viruses, pointing to the impact of biological interactions associated with these events. Comparison between experimental and in situ population transcription patterns indicated that manipulated populations can serve as analogs for natural populations, and that natural populations may be frequently or continuously responding to nutrients from deeper waters. Finally, this study also shows that the microarray approach, which is complementary to metatranscriptomic sequencing, is useful for determining the physiological status of in situ microbial communities

Cyclic triaxial apparatus for the study of permanent deformations of bituminous mixes

Rutting is one of the main modes of degradation of bituminous pavements. In order to study the rutting behaviour under realistic stress states, the Laboratoire Central des Ponts et Chaussées (LCPC) has acquired a new cyclic triaxial apparatus for bituminous materials. This apparatus allows to perform cyclic tests in compression and tension, on 80 mm or 100 mm diameter specimens, at controlled temperatures between 0 and 60 °C. Axial and radial strains are measured on the sample. This paper describes the experimental work that is going on at LCPC using this new device and the conclusions of these first tests. The first part of the paper presents the experimental device. The choice of appropriate test conditions, for the study of permanent deformations is also discussed, on the basis of the modelling of stress states in pavement layers under traffic loading. The second part of the paper presents first experimental results of creep tests at constant stress and at constant strain rate performed with the triaxial apparatus. Based on these results and complex modulus tests, parameters of the DBN visco-elasto-plastic model have been determined. A first assessment of the capacity of this model

Isolation and expression of tilapia (Oreochromis niloticus) serine 8-type GnRH coding and regulatory sequences

The complete Serine 8-type gonadotropin releasing hormone (GnRH) coding sequence with a substantial 5-prime regulatory sequence (5 kb) has been isolated and characterised in Nile Tilapia (Oreochromis niloticus) from a relevant genomic library. The primary structure of the protein precursor was identified for this gene. The promoter efficacy has been tested using 0.6 kb of the GnRH promoter driving a lacZ reporter gene in both cultured spleen cells and transiently expressing zebrafish. In the cell transfection experiments, the average level of b- galactosidase activity in transfected cells was more than 2.1 (P , 0:05) times higher than the control promoter-less vector in five independent cultures indicating that the 0.6GnRH/lacZ construct is able to express in spleen cells. In addition, the transient expression of the lacZ gene was detected in the brain of G0 zebrafish embryos (Danio rerio) 4 days after fertilisation following egg injection with the construct, which demonstrated the efficacy of the tilapia GnRH promoter. <br/

Multiscale approach to characterize mechanical properties of tissue engineered skin

International audienceTissue engineered skin usually consist of a multi-layered visco-elastic material composed of a fibrillar matrix and cells. The complete mechanical characterization of these tissues has not yet been accomplished. The purpose of this study was to develop a multiscale approach to perform this characterization in order to link the development process of a cultured skin to the mechanical properties. As a proof-of-concept, tissue engineered skin samples were characterized at different stages of manufacturing (acellular matrix, reconstructed dermis and reconstructed skin) for two different aging models (using cells from an 18- and a 61-year-old man). To assess structural variations, bi-photonic confocal microscopy was used. To characterize mechanical properties at a macroscopic scale, a light-load micro-mechanical device that performs indentation and relaxation tests was designed. Finally, images of the internal network of the samples under stretching were acquired by combining confocal microscopy with a tensile device. Mechanical properties at microscopic scale were assessed. Results revealed that adding cells during manufacturing induced structural changes, which provided higher elastic modulus and viscosity. Moreover, senescence models exhibited lower elastic modulus and viscosity. This multiscale approach was efficient to characterize and compare skin equivalent samples and permitted the first experimental assessment of the Poisson’s ratio for such tissues

Vulnerable Territories: The Perpetually Shifting Edge

New Zealand’s coastline is rapidly receding. The increased threat of rising sea levels continues to erode the shore line causing extensive and irreparable damage to thousands of coastal properties, often dismantling communities and the kiwi dream of living near the ocean. With global temperatures continuing to rise, all of our coastal communities are at risk. The current measure of response to this issue is through managed retreat, the removal and relocation of all ‘at risk’ buildings in coastal hazard zones. While this approach is successful in preserving the physical structures, it remains an undesirable solution that forces homeowners to abandon their community and the coastline for the safety of higher ground. The retreat is hampered among debate within the effected regions as the forced detachment of long standing communities often results in the loss of ‘sense of place’ that living within a coastal community enables. This thesis proposes that Haumoana in Hawkes Bay offers the fitting location to introduce an alternative coastal community model that actively responds to the impending hazards whilst retaining the societal poetics. Situated just south of the nearby communities of Te Awanga and Haumoana, two of the most at-risk coastal regions in New Zealand that are currently facing the prospect of dismantlement. The site was specifically chosen due to the fact that erosion is predicted to diminish half its usable land over the next century, this thesis will investigate the potential risks to the respective coastline, the role that this would play in an adaptive community, and the possible design options that can respond and enhance a future sustainable landscape. This thesis argues that a coastal community can be designed to actively adapt and respond to the threat of erosion rather than being dismantled through retreat; that by adopting design principles that protect the land on which they are placed, the coastal hazards of the region can be lessened; and that an adaptive community model can be achieved whilst retaining the ‘sense of place’ that coastal community’s exhibit. The thesis proposes that this can be achieved by incorporating and reinforcing natural features of the coast into the architectural design at various scales; accommodating for, and adapting to the imminent threat of erosion; and by invoking principles of sustainable design in company with adaptive planning and resilient design, thereby pushing the standards of coastal planning beyond typical practice

Characterization of the mechanical properties of a dermal equivalent compared with human skin in vivo by indentation and static friction tests

International audienceThe study of changes in skin structure with age is becoming all the more important with the increase in life. The atrophy that occurs during aging is accompanied by more profound changes, with a loss of organization within the elastic collagen network and alterations in the basal elements. The aim of this study is to present a method to determine the mechanical properties of total human skin in vivo compared with dermal equivalents (DEs) using indentation and static friction tests