The Tidal Tails of 47 Tucanae

The Galactic globular cluster 47 Tucanae (47 Tuc) shows a rare increase in its velocity dispersion profile at large radii, indicative of energetic, yet bound, stars at large radii dominating the velocity dispersion and, potentially, of ongoing evaporation. Escaping stars will form tidal tails, as seen with several Galactic globular clusters, however, the tidal tails of 47 Tuc are yet to be uncovered. We model these tails of 47 Tuc using the most accurate input data available, with the specific aim of determining their locations, as well as the densities of the epicyclic overdensities within the tails. The overdensities from our models show an increase of 3-4% above the Galactic background and, therefore, should be easily detectable using matched filtering techniques. We find that the most influential parameter with regard to both the locations and densities of the epicyclic overdensities is the Heliocentric distance to the cluster. Hence, uncovering these tidal features observationally will contribute greatly to the ongoing problem of determining the distance to 47 Tuc, tightly constraining the distance of the cluster independent of other methods. Using our streakline method for determining the locations of the tidal tails and their overdensities, we show how, in principle, the shape and extent of the tidal tails of any Galactic globular cluster can be determined without resorting to computationally expensive N-body simulations.Comment: Original paper has 10 pages, 10 figures and 2 tables. Please note that this now includes an erratum. Erratum has 6 pages, 8 figures and 2 tables. Ignore the exclamation marks in Section 2 of the erratum, these are an artifact of the LaTeX class file used to produce the manuscrip

Chytridiomycosis of marine diatoms : the role of stress physiology and resistance in parasite-host recognition and accumulation of defense molecules

Little is known about the role of chemotaxis in the location and attachment of chytrid zoospores to potential diatom hosts. Hypothesizing that environmental stress parameters affect parasite-host recognition, four chytrid-diatom tandem cultures (Chytridium sp./Navicula sp., Rhizophydium type I/Nitzschia sp., Rhizophydium type IIa/Rhizosolenia sp., Rhizophydium type IIb/Chaetoceros sp.) were used to test the chemotaxis of chytrid zoospores and the presence of potential defense molecules in a non-contact-co-culturing approach. As potential triggers in the chemotaxis experiments, standards of eight carbohydrates, six amino acids, five fatty acids, and three compounds known as compatible solutes were used in individual and mixed solutions, respectively. In all tested cases, the whole-cell extracts of the light-stressed (continuous light exposure combined with 6 h UV radiation) hosts attracted the highest numbers of zoospores (86%), followed by the combined carbohydrate standard solution (76%), while all other compounds acted as weak triggers only. The results of the phytochemical screening, using biomass and supernatant extracts of susceptible and resistant host-diatom cultures, indicated in most of the tested extracts the presence of polyunsaturated fatty acids, phenols, and aldehydes, whereas the bioactivity screenings showed that the zoospores of the chytrid parasites were only significantly affected by the ethanolic supernatant extract of the resistant hosts

The potential role of kelp forests on iodine speciation in coastal seawater

Funding: FCK would like to thank the TOTAL Foundation (Paris) and the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) for their support. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. JG acknowledges support from an SDSU Research Foundation Summer Undergraduate Research Award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Peculiarities in Velocity Dispersion and Surface Density Profiles of Star Clusters

Based on our recent work on tidal tails of star clusters (Kuepper et al. 2009) we investigate star clusters of a few 10^4 Msun by means of velocity dispersion profiles and surface density profiles. We use a comprehensive set of $N$-body computations of star clusters on various orbits within a realistic tidal field to study the evolution of these profiles with time, and ongoing cluster dissolution From the velocity dispersion profiles we find that the population of potential escapers, i.e. energetically unbound stars inside the Jacobi radius, dominates clusters at radii above about 50% of the Jacobi radius. Beyond 70% of the Jacobi radius nearly all stars are energetically unbound. The velocity dispersion therefore significantly deviates from the predictions of simple equilibrium models in this regime. We furthermore argue that for this reason this part of a cluster cannot be used to detect a dark matter halo or deviations from Newtonian gravity. By fitting templates to the about 10^4 computed surface density profiles we estimate the accuracy which can be achieved in reconstructing the Jacobi radius of a cluster in this way. We find that the template of King (1962) works well for extended clusters on nearly circular orbits, but shows significant flaws in the case of eccentric cluster orbits. This we fix by extending this template with 3 more free parameters. Our template can reconstruct the tidal radius over all fitted ranges with an accuracy of about 10%, and is especially useful in the case of cluster data with a wide radial coverage and for clusters showing significant extra-tidal stellar populations. No other template that we have tried can yield comparable results over this range of cluster conditions. All templates fail to reconstruct tidal parameters of concentrated clusters, however. (abridged)Comment: 23 pages, 13 figures, accepted for publication in MNRA

Entre las causas y las razones: sobre la explicación social y sus límites

"Este texto es el resultado de las reflexiones teóricas suscitadas por mi participación en el proyecto SEC96-0639 del Plan Nacional de I+D, dirigido por Ludolfo Paramio. No quiero dejar de agradecer los detallados comentarios de Antonio Niño Rodríguez y Leopoldo Moscoso Sarabia a los dos borradores previos".ME

The future of marine biodiversity and marine ecosystem functioning in UK coastal and territorial waters (including UK Overseas Territories) – with an emphasis on marine macrophyte communities

Funding from the UK Natural Environment Research Council (NERC) through Oceans 2025 (WP4.5), Funder Id: 10.13039/501100000270, Grant Number: Oceans 2025 – WP 4.5 and the MASTS pooling initiative (Marine Alliance for Science and Technology for Scotland, funded by the Scottish Funding Council and contributing institutions; grant reference HR09011) is gratefully acknowledged.Peer reviewedPublisher PD

Predicting diversity in benthic macro-scale communities associated with mussel matrices in three Pacific ecoregions

Scottish Funding Council. Grant Number: HR09011Peer reviewedPublisher PD

Emission of volatile halogenated compounds, speciation and localization of bromine and iodine in the brown algal genome model Ectocarpus siliculosus

This study explores key features of bromine and iodine metabolism in the filamentous brown alga and genomics model Ectocarpus siliculosus. Both elements are accumulated in Ectocarpus, albeit at much lower concentration factors (2-3 orders of magnitude for iodine, and < 1 order of magnitude for bromine) than e.g. in the kelp Laminaria digitata. Iodide competitively reduces the accumulation of bromide. Both iodide and bromide are accumulated in the cell wall (apoplast) of Ectocarpus, with minor amounts of bromine also detectable in the cytosol. Ectocarpus emits a range of volatile halogenated compounds, the most prominent of which by far is methyl iodide. Interestingly, biosynthesis of this compound cannot be accounted for by vanadium haloperoxidase since the latter have not been found to catalyze direct halogenation of an unactivated methyl group or hydrocarbon so a methyl halide transferase-type production mechanism is proposed

The current state of DNA barcoding of macroalgae in the Mediterranean Sea : presently lacking but urgently required

The research work disclosed in this publication is partially funded by the ENDEAVOUR Scholarship Scheme (Malta)-Group B – National Funds. FCK would also like to thank the UK Natural Environment Research Council (grants NE/D521522/1, NE/J023094/1, 2025/WP 4.5), the TOTAL Foundation (Project “Diversity of brown algae in the Eastern Mediterranean”) and the Marine Alliance for Science and Technology for Scotland (MASTS) pooling initiative, which is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. AFP was funded by the project IDEALG (France: ANR-10-BTBR-04).Peer reviewedPostprin