Coexistence of fish species with strongly similar life histories - population dynamical feedback forces species to pick sides

Fish generally grow several orders of magnitude between the larval and adult stage. Many ecological properties of organisms are related to body size, and hence small fish often have very different ecological roles than large conspecifics. This also implies that omnivory, the feeding on more than one trophic level by individuals of the same species, is a common phenomenon in fish. Intraguild predation is omnivory in its simplest form, where two species compete for the same resource, but one of the species can also eat its competitor. In models, persistence of both species in such a configuration is difficult to obtain. In marine fish communities however, it is observed routinely. One way in which persistence of omnivorous species can be established is by incorporating it as an ontogenetic diet shift, where small individuals of both species compete, and large individuals of one can feed on the small individuals of the others species. We show in this study that this mechanism can not only lead to persistence of a single omnivorous species, but also to persistence of multiple omnivorous species. This is possible given that the adults have sufficiently different diets. It is shown that, while adults of both species can feed both on small competitors or on the basic resource, due to the population dynamical feedback, one species will in practice act as a predator, while the other acts as prey. This way, a system with two omnivores in practice persists as a tritrophic system. Which of the species assumes which role depends on the specific community characteristics. We show here that by incorporating complex size-dependent feeding relationships in food webs, many more species may be able to coexist than is possible based on either species-level considerations or size spectrum models which do incorporate within-population size differences, but relate diet only to individual body size irrespective of species identity. The mechanism underlying our result may be part of the explanation why fish species with seemingly similar life histories do coexist in marine ecosystems

Verkenning van mogelijkheden voor mosselteelt op Noordzee

In dit rapport wordt nagegaan of er wereldwijd zodanig perspectiefrijke experimenten met invang dan wel kweek van mosselen in het open zee milieu (offshore) plaatsvinden, of dat er reeds volledig commercieel draaiende mosselculturen op open zee bestaan. Indien dit het geval is wordt bezien of hiervan gebruik kan worden gemaakt voor de innovatie van de Nederlandse mosselsector. Wij achten de studies het meest relevant voor het toepassen van installaties als de fysische omstandigheden (diepte, golfhoogte en stroomsnelheid) zoveel als mogelijk overeenkomen met die in de Noordzee

Poincare Polynomials and Level Rank Dualities in the N=2N=2 Coset Construction

We review the coset construction of conformal field theories; the emphasis is on the construction of the Hilbert spaces for these models, especially if fixed points occur. This is applied to the $N=2$ superconformal cosets constructed by Kazama and Suzuki. To calculate heterotic string spectra we reformulate the Gepner con- struction in terms of simple currents and introduce the so-called extended Poincar\'e polynomial. We finally comment on the various equivalences arising between models of this class, which can be expressed as level rank dualities. (Invited talk given at the III. International Conference on Mathematical Physics, String Theory and Quantum Gravity, Alushta, Ukraine, June 1993. To appear in Theor. Math. Phys.)Comment: 14 pages in LaTeX, HD-THEP-93-4

Groei en conditie van zwaardschede (Ensis directus, Conrad) voor, tijdens en na geplande zandwinning in 2013 - 2017: Berekeningen voor het HHNK

In dit project is het effect van zandwinning op de groei van Ensis directus geanalyseerd d.m.v. een Dynamic Energy Budget (DEB) model voor een zestal punten gelegen op drie raaien in de kustzone. Centrale vraag bij het gezamenlijke Deltares-IMARES onderzoek was: Wat is het effect van zandwinning op de slib- en algenconcentraties in de Noordzee en Waddenzee en op de groei en conditie van zwaardschede Ensis directus gegeven de berekende veranderingen in slib en algenconcentraties

The non-compact elliptic genus: mock or modular

We analyze various perspectives on the elliptic genus of non-compact supersymmetric coset conformal field theories with central charge larger than three. We calculate the holomorphic part of the elliptic genus via a free field description of the model, and show that it agrees with algebraic expectations. The holomorphic part of the elliptic genus is directly related to an Appell-Lerch sum and behaves anomalously under modular transformation properties. We analyze the origin of the anomaly by calculating the elliptic genus through a path integral in a coset conformal field theory. The path integral codes both the holomorphic part of the elliptic genus, and a non-holomorphic remainder that finds its origin in the continuous spectrum of the non-compact model. The remainder term can be shown to agree with a function that mathematicians introduced to parameterize the difference between mock theta functions and Jacobi forms. The holomorphic part of the elliptic genus thus has a path integral completion which renders it non-holomorphic and modular.Comment: 13 page

Biosimilar therapeutics—what do we need to consider?

Patents for the first generation of approved biopharmaceuticals have either expired or are about to expire. Thus the market is opening for generic versions, referred to as ‘biosimilars’ (European Union) or ‘follow-on protein products’ (United States). Healthcare professionals need to understand the critical issues surrounding the use of biosimilars to make informed treatment decisions

Automorphism Modular Invariants of Current Algebras

We consider those two-dimensional rational conformal field theories (RCFTs) whose chiral algebras, when maximally extended, are isomorphic to the current algebra formed from some affine non-twisted Kac--Moody algebra at fixed level. In this case the partition function is specified by an automorphism of the fusion ring and corresponding symmetry of the Kac--Peterson modular matrices. We classify all such partition functions when the underlying finite-dimensional Lie algebra is simple. This gives all possible spectra for this class of RCFTs. While accomplishing this, we also find the primary fields with second smallest quantum dimension.Comment: 32 pages, plain Te

DEB ensis vs. data

Along the Dutch coast (North sea) large quantities of sand are mined in certain locations to supply sand for coastal defence at other locations in order to retain the existing coastline. Without these nourishments of sand the coast would erode and eventually this erosion would lead to an increased risk of flooding. This project provides the opportunity to use measured environmental data to predict growth of Ensis directus using the DEBEnsis model and compare it to measured biotic data on Ensis. Here we report on the findings of the comparison of field data and model estimates and suggest improvements, both in field measurements, experiments and (adjustments to DEB) modelling. For this study, Ensis directus was taken as a model organism, because of its high dominance in biomass in the Dutch coastal zone