A dense assemblage of the brachiopod Magellania fragilis was sampled by trawl and underwater photography during the expedition ANT IX/3 (1991) of RV ‘Polarstern’ on the shelf of the Lazarev Sea, Antarctica. Mean abundance and biomass estimates for M. fragilis were 26.15 individuals m2 and 1.13 g AFDM m2, respectively. Growth bands visible on the shell were interpreted as annual growth marks caused by the strong seasonality of food input to the benthos and were treated as size-at-age data. The von Bertalanffy growth function Lt (mm) = 51.67 (1 - e0020 (t +1.326))3.828 described these data best. The annual somatic P/B ratio was very low, 0.046 y1, and annual production amounted to 0.052 g AFDM m2 y1 at this particular site. These results indicate that M. fragilis is a comparatively slow-growing species with very low annual productivity.
In this contribution we are concerned with tight a posteriori error estimation for projection based model order reduction of inf -sup stable parameterized variational problems. In particular, we consider the Reduced Basis Method in a Petrov-Galerkin framework, where the reduced approximation spaces are constructed by the (weak) Greedy algorithm. We propose and analyze a hierarchical a posteriori error estimator which evaluates the difference of two reduced approximations of different accuracy. Based on the a priori error analysis of the (weak) Greedy algorithm, it is expected that the hierarchical error estimator is sharp with efficiency index close to one, if the Kolmogorov N-with decays fast for the underlying problem and if a suitable saturation assumption for the reduced approximation is satisfied. We investigate the tightness of the hierarchical a posteriori estimator both from a theoretical and numerical perspective. For the respective approximation with higher accuracy we study and compare basis enrichment of Lagrange-and Taylor-type reduced bases. Numerical experiments indicate the efficiency for both, the construction of a reduced basis using the hierarchical error estimator in a weak Greedy algorithm, and for tight online certification of reduced approximations. This is particularly relevant in cases where the inf -sup constant may become small depending on the parameter. In such cases a standard residual-based error estimator -complemented by the successive constrained method to compute a lower bound of the parameter dependent inf -sup constant -may become infeasible.
Growth, reproduction and production of the epizoic bivalve Lissarca notorcadensjs were compared between 2 regions of the Weddell Sea, the South Orkney and South Shetland shelves (north of 63" S) and the southeastern continental shelf (south of 70' S). Growth lines on the shell surface were interpreted as annual growth marks. Von Bertalanffy growth functions were fitted to length-at-age data for the northern region (L, = 12.140 mm. K = 0.085 yr-', t o = -1.477 yr) and for the southern region (L, = 9.802 mm, K = 0.112 yr-l, t o = -1.247 yr). Female gonad production was estimated from the number of embryos brooded per female, embryo mass at release and the fraction of females in the population. Somatic production was calculated from weight specific growth rates. Annual somatic and gonad production/biomass (P/B) ratios were 0.316 and 0.151 (north), and 0.305 and 0.132 (south), respectively. These values are lower than P/B ratios of boreal mollusc populations of comparable mean body mass.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.