Exact Flow Equations and the U(1)-Problem

The effective action of a SU(N)-gauge theory coupled to fermions is evaluated at a large infrared cut-off scale k within the path integral approach. The gauge field measure includes topologically non-trivial configurations (instantons). Due to the explicit infrared regularisation there are no gauge field zero modes. The Dirac operator of instanton configurations shows a zero mode even after the infrared regularisation, which leads to U_A(1)-violating terms in the effective action. These terms are calculated in the limit of large scales k.Comment: 22 pages, latex, no figures, with stylistic changes and some arguments streamlined, typos corrected, References added, to appear in Phys. Rev.

Differential Responses of Calcifying and Non-Calcifying Epibionts of a Brown Macroalga to Present-Day and Future Upwelling pCO2

Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida) and Electra pilosa (Bryozoa) and the non-calcifier Alcyonidium hirsutum (Bryozoa) were maintained for 30 days under three pCO2 conditions: natural 460±59 µatm, present-day upwelling1193±166 µatm and future upwelling 3150±446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm) but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic. Only extreme future upwelling conditions impacted the tubeworm S. spirorbis, but not the bryozoans

Temperate skeletal carbonate sediments on Scott shelf, northwestren Vancouver Island, Canada

Scott shelf ( 2000 km2), centred at Scott Islands, northwestern Vancouver Island, is mainly shallower than 150 m, topographically diversified, and floored by bedrock outcrops and terrigenous lithic gravels and sands left stranded following the post-glacial rise in sea level (13,000 yrs B.P.). It lies in a zone of vigorous wind-wave currents and strong tidal flows, but is largely starved of modern terrigenous sediment. As a consequence it is slowly accumulating a thin, discontinuous blanket of clean, skeletal carbonate sands and gravels, admixed to varying degrees with the underlying terrigenous deposits. Principal skeletal contributors are infaunal bivalves (on coarse sandy and gravelly substrates), barnacles (on low-amplitude gravelly ridges), bryozoans (on bedrock outcrops and boulders) and benthic foraminifera (on fine sands in deep (> 100 m) waters south of the Scott Islands). Living carbonate benthos are scattered and generally sparse, occupying specific ecologic niches, and the shelf-wide rate of carbonate production is low. Skeletons are fragmented, transported and mixed during storms and are concentrated within bedrock hollows and crevices, and shallow depressions between gravel ridges. Where infaunal bivalves are abundant the carbonates are dominated by aragonite, but otherwise the skeletal hashes are predominantly calcitic. Many grains, and especially aragonitic ones, are corroded and weakened by epilithic and endolithic bioerosion, and probably also by marine and dissolution. The most corroded shells have ages of only about 1000 yrs so that their preservation potential is low. The character of Scott shelf skeletal carbonate deposits reflects their temperate latitude, cold-water heritage

(Table 1) Summary of accelerator mass spectrometer (AMS) radiocarbon ages in ODP Sites 169-1033 and 169-1034

Continuous coring in Saanich Inlet (Ocean Drilling Program, ODP Leg 169S), British Columbia, Canada, yielded a detailed record of Late Quaternary climate, oceanography, marine productivity, and terrestrial vegetation. Two sites (1033 and 1034) were drilled to maximum depths of 105 and 118 m, recovering sediments ranging in age from 13,300 to less than 300 14C yr. Earliest sediments consist of dense, largely massive, gray glaciomarine muds with dropstones and sand and silt laminae deposited during the waning stages of glaciation. Deposition of organic-rich olive gray sediments began in the fjord about 12,000 14C yr ago, under well-oxygenated conditions as reflected by the presence of bioturbation and a diverse infaunal bivalve community. At about 10,500 14C yr, a massive, gray unit, 40-50 cm thick, was emplaced in a very short span of time. The unit is marked by a sharp lower contact, a gradational upper contact and an abundance of reworked Tertiary microfossils. It has been interpreted as resulting from massive flood events caused by the collapse of glacial dams in the Fraser Valley of mainland British Columbia. Progressively greater anoxia in bottom waters of Saanich Inlet began about 7000 14C yr ago. This is reflected in the preservation of varved sediments consisting of diatomaceous spring-summer laminae and terrigenous winter laminae. Correlation of the sediments was based on: marked lithologic changes, the presence of massive intervals (reflecting localized sediment gravity flow events), the Mazama Ash, occasional thin gray laminae (indicative of abnormal flood events in nearby watersheds), varve counts between marker horizons, and 71 accelerator mass spectrometry (AMS) radiocarbon dates

A Methodology for Evaluating the Extensibility of Boolean Networks’ Structure and Function

International audienceFormal interaction networks are well suited for representing complex biological systems and have been used to model signalling pathways, gene regulatory networks, interaction within ecosystems, etc. In this paper, we introduce Sign Boolean Networks (SBNs), which are a uniform variant of Threshold Boolean Networks (TBFs). We continue the study of the complexity of SBNs and build a new framework for evaluating their ability to extend, i.e. the potential to gain new functions by addition of nodes, while also maintaining the original functions. We describe our software implementation of this framework and show some first results. These results seem to confirm the conjecture that networks of moderate complexity are the most able to grow, because they are not too simple, but also not too constrained, like the highly complex ones

Distinguishing Sediment Bedforms from Sediment Deformation in Prodeltas of the Mediterranean Sea

12 pages, 5 figuresMost Mediterranean prodeltas show undulated sediments on the foresets of their Holocene wedges. These features have been described all along the Mediterranean and interpreted as either soft sediment deformation or, more recently, as sediment bedforms. We present a detailed analysis of these features using ultrahighresolution seismic and bathymetric data, as well as geotechnical information and hydrodynamic time series and hydrographic transects. We show that the characteristics of the sediment undulations (morphology and configuration of the reflections down section and between adjacent undulations) are incompatible with a genesis by sediment deformationThe data on the Iberian prodeltas was acquired in the frame of the Spanish projects PRODELTA (REN2002-02323). We thank captain and crew of R/V L’Atalante ­(campagne PRISME 2007) and funding from French ANR projects ISIS and DANACOR. Data for some areas of the continental shelf (Ter prodelta) were acquired by “Secretaría General del Mar” of the “Ministerio de Medio Ambiente, y Medio Rural y Marino” and provided free of charge. Borehole geotechnical data was acquired in the frame EC funded project PROMESS-1 (EVR1-CT-2002-40024). Hydrodynamic transects and instrumented moorings were funded by the Office of Naval Research, NICOP Grant N00014-02-1-0252. The “Generalitat de Catalunya” is acknowledged for support through an excellence research group grant (2009-SGR-146). J. Déverchère (UBO-IUEM, Brest) and K. Yelles (CRAAG, Algiers) are thanked for discussions about the Algerian shelf. Reviews by Homa Lee and Michele Rebesco greatly improved the submitted version of the manuscriptPeer reviewe

Biostratigraphy, Depositional Environments, and Diagenesis of the Tamana Formation, Trinidad: a Tectonic Marker Horizon

The Tamana Formation of the Central Range of Trinidad was studied in order to determine its importance in the stratigraphical and structural development of north‐eastern South America. Biostratigraphical, petrological and mineralogical data, combined with field mapping show that the Tamana sediments are composed of five distinct lithofacies: inner to outer shelf, burrowed shaley mudstone; outer shelf, Fe‐rich sandy limestone; submarine channel, conglomeratic mudstone; middle shelf to nearshore, algal‐foram packstone/grainstone; and intertidal to nearshore, algal‐stromatolite‐coral boundstone with coral bioherms. Maximum thickness of the Tamana Formation is 244 m. Deposition of the Tamana limestones occurred between the Praeorbulina glomerosa (latest early Miocene) and Globorotalia fohsi robusta (middle part of the middle Miocene) planktonic foraminiferal zones, and in a more continuous trend than is seen in the current outcrop belt. Detailed biostratigraphy shows that the Tamana Formation is a facies equivalent of the shallow‐ and deep‐water shales of the Brasso Formation, and the deep water turbidites of the Herrera Member of the Cipero Formation. The early diagenetic history of the Tamana limestones was dominated by the precipitation of authigenic glauconitic smectite, and the dissolution of skeletal grains and carbonate matrix. Late burial diagenesis was dominated by the precipitation of illite and illite/smectite. Comparative mineralogy and textural analyses indicate a minimum range of burial depth for the Tamana Formation at 800–1500m, with a maximum of 2400 m. Alteration of Fe‐bearing minerals to geothite and late fracturing occurred during post‐Pliocene tectonic uplift and unroofing of the Central Range. The Tamana Formation sediments can be used as a structural and stratigraphical event marker within the Late Tertiary geological history of Trinidad. These units record a phase of the tectonic interaction between the Caribbean and South American plates in the south‐eastern Caribbean, and reflect the onset of contractile deformation in the Central Range