Scientific, Technical and Economic Committee for Fisheries. Impact assessment of Bay of Biscay sole (STECF-11-01)

This report is one of two reports to the STECF of EWG 11-01 of the STECF Expert Working Group on management plans, (28 February to 4 March 2011) and provides an Impact Assessment report on the Bay of Biscay sole fisheries. It summaries biological modelling of a range of different stock dynamics incorporating uncertainty in stock recruitment function and measurement error. The results from an integrated bio-economic model showing economic impact on the sole fishery in the Bay of Biscay are presented. The simulations carried out show that a target F of 0.26 (Fmsy ) can be accepted as precautionary in the long term. Target Fs between 0.15 and 0.35 will give yields within 5% of yield at F=0.26. Economic considerations suggest that the management plan is expected to have slight long term gains and short term negative economic impacts for all the fleets involved in the sole fishery. The economic viability of fleets is not endangered and effort reallocation is expected to offset losses although it is difficult to predict such reallocation. The report provides details of approaches that could be used if the ICES assessment fails. The report has been endorsed by the STECF during its 36th plenum in April 2011

Multiscale Modeling of Bacterial Colonies: How Pili Mediate the Dynamics of Single Cells and Cellular Aggregates

Neisseria gonorrhoeae is the causative agent of one of the most common sexually transmitted diseases, gonorrhea. Over the past two decades there has been an alarming increase of reported gonorrhea cases where the bacteria were resistant to the most commonly used antibiotics thus prompting for alternative antimicrobial treatment strategies. The crucial step in this and many other bacterial infections is the formation of microcolonies, agglomerates consisting of up to several thousands of cells. The attachment and motility of cells on solid substrates as well as the cell–cell interactions are primarily mediated by type IV pili, long polymeric filaments protruding from the surface of cells. While the crucial role of pili in the assembly of microcolonies has been well recognized, the exact mechanisms of how they govern the formation and dynamics of microcolonies are still poorly understood. Here, we present a computational model of individual cells with explicit pili dynamics, force generation and pili–pili interactions. We employ the model to study a wide range of biological processes, such as the motility of individual cells on a surface, the heterogeneous cell motility within the large cell aggregates, and the merging dynamics and the self-assembly of microcolonies. The results of numerical simulations highlight the central role of pili generated forces in the formation of bacterial colonies and are in agreement with the available experimental observations. The model can quantify the behavior of multicellular bacterial colonies on biologically relevant temporal and spatial scales and can be easily adjusted to include the geometry and pili characteristics of various bacterial species. Ultimately, the combination of the microbiological experimental approach with the in silico model of bacterial colonies might provide new qualitative and quantitative insights on the development of bacterial infections and thus pave the way to new antimicrobial treatments

A global perspective on the trophic geography of sharks

Carbon isotopic analysis reveals global biogeographic traits in shark trophic interactions, and sheds light on the diverse foraging behaviour of sharks

Scientific, Technical and Economic Committee for Fisheries (STECF) - Report of the STECF Study Group on the Evaluation of Fishery Multi-annual Plans (SGMOS 09-02)

SG-MOS 09-02 was held in IPIMAR, Lisbon, (Portugal), on 23-27 November 2009. The aim of the workshop was to provide Evaluations of three multiannual fisheries management plans:- R(EC) No 388/2006 ¿ multi-annual plan for sole in the Bay of Biscay; R(EC) No 209/2007 ¿ multi-annual plan for sole in the Western Channel R(EC) No676/2007 ¿ multi-annual plan for sole and plaice in the North Sea. STECF reviewed the report during its Plenary meeting on 26-30 April 2010.JRC.DG.G.4-Maritime affair

Strategies used as spectroscopy of financial markets reveal new stylized facts

We propose a new set of stylized facts quantifying the structure of financial markets. The key idea is to study the combined structure of both investment strategies and prices in order to open a qualitatively new level of understanding of financial and economic markets. We study the detailed order flow on the Shenzhen Stock Exchange of China for the whole year of 2003. This enormous dataset allows us to compare (i) a closed national market (A-shares) with an international market (B-shares), (ii) individuals and institutions and (iii) real investors to random strategies with respect to timing that share otherwise all other characteristics. We find that more trading results in smaller net return due to trading frictions. We unveiled quantitative power laws with non-trivial exponents, that quantify the deterioration of performance with frequency and with holding period of the strategies used by investors. Random strategies are found to perform much better than real ones, both for winners and losers. Surprising large arbitrage opportunities exist, especially when using zero-intelligence strategies. This is a diagnostic of possible inefficiencies of these financial markets.Comment: 13 pages including 5 figures and 1 tabl

A model for a large investor trading at market indifference prices. I: single-period case

We develop a single-period model for a large economic agent who trades with market makers at their utility indifference prices. A key role is played by a pair of conjugate saddle functions associated with the description of Pareto optimal allocations in terms of the utility function of a representative market maker.Comment: Shorten from 69 to 30 pages due to referees' requests; a part of the previous version has been moved to "The stochastic field of aggregate utilities and its saddle conjugate", arXiv:1310.728

How do financial intermediaries create value in security issues?

We study incentive provision in a model of securities issuance with an informed issuer and uninformed investors. We show that the presence of an informed intermediary may increase surplus even if we allow for collusion between the intermediary and the issuer. Collusion is neutralized by introducing a misalignment between the interests of the issuer and those of the intermediary. To achieve this, the intermediary commits to hold some of the securities. The intermediary then underprices the remaining securities and extracts any investor surplus through a “participation fee.” We provide an explanation for the diffusion of book building and quid pro quo practices in Initial Public Offerings (IPOs)

Common Cell Shape Evolution of Two Nasopharyngeal Pathogens

Respiratory infectious diseases are the third cause of worldwide death. The nasopharynx is the portal of entry and the ecological niche of many microorganisms, of which some are pathogenic to humans, such as Neisseria meningitidis and Moraxella catarrhalis. These microbes possess several surface structures that interact with the actors of the innate immune system. In our attempt to understand the past evolution of these bacteria and their adaption to the nasopharynx, we first studied differences in cell wall structure, one of the strongest immune-modulators. We were able to show that a modification of peptidoglycan (PG) composition (increased proportion of pentapeptides) and a cell shape change from rod to cocci had been selected for along the past evolution of N. meningitidis. Using genomic comparison across species, we correlated the emergence of the new cell shape (cocci) with the deletion, from the genome of N. meningitidis ancestor, of only one gene: yacF. Moreover, the reconstruction of this genetic deletion in a bacterium harboring the ancestral version of the locus together with the analysis of the PG structure, suggest that this gene is coordinating the transition from cell elongation to cell division. Accompanying the loss of yacF, the elongation machinery was also lost by several of the descendants leading to the change in the PG structure observed in N. meningitidis. Finally, the same evolution was observed for the ancestor of M. catarrhalis. This suggests a strong selection of these genetic events during the colonization of the nasopharynx. This selection may have been forced by the requirement of evolving permissive interaction with the immune system, the need to reduce the cellular surface exposed to immune attacks without reducing the intracellular storage capacity, or the necessity to better compete for adhesion to target cells