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Fish assemblages in the seagrass beds at Inhaca Island (Mozambique): cold season
Bol. Mus. Mun. Funchal, Sup. N.º 6: 111-125, 2001The fish communities in the seagrass beds at Inhaca Island (Mozambique) were sampled in three stations during the cold season (July-August 1993). On the whole, 66 species of fishes belonging to 34 families were collected by trawling. Cluster and factorial correspondence analyses showed that the fish community structure was different at the three stations. These structural differences were attributed to the type of seagrass association and to the proximity of mangrove and coral reef areas. Differences between day and night samples attest to the occurrence of marked circadian changes between nocturnal and diurnal components of this seagrass fish community. Carnivorous fishes were dominant both in number and biomass while herbivorous and omnivorous species were less represented in these assemblages.As comunidades ictiológicas dos fundos de fanerogâmicas da Ilha da Inhaca (Moçambique) foram amostradas em 3 estações durante a estação a estação fria (Julha-Agosto de 1993). No total, 66 espécies de peixes pertencendo a 34 famílias foram colhidas com arrasto. A análise dos dados mostrou que as comunidades ictiológicas tinham estruturas diferentes nas 3 estações. Estas diferenças foram atribuídas ao tipo de associação vegetal e à distância às áreas de coral e de mangal. Diferenças entre as amostragens diurnas e nocturnas atectam a ocorrência de ciclos circadianos marcados e a sua influência nas comunidades. Espécies carnívoras foram dominantes, quer em número, quer em biomassa, em relação às herbívoras e omnívoras
A percolation system with extremely long range connections and node dilution
We study the very long-range bond-percolation problem on a linear chain with
both sites and bonds dilution. Very long range means that the probability
for a connection between two occupied sites at a distance
decays as a power law, i.e. when , and
when . Site dilution means that the occupancy probability of a site
is . The behavior of this model results from the competition
between long-range connectivity, which enhances the percolation, and site
dilution, which weakens percolation. The case with is
well-known, being the exactly solvable mean-field model. The percolation order
parameter is investigated numerically for different values of
, and . We show that in the ranges
and the percolation order parameter depends only on
the average connectivity of sites, which can be explicitly computed in
terms of the three parameters , and
Overview of Constrained PARAFAC Models
In this paper, we present an overview of constrained PARAFAC models where the
constraints model linear dependencies among columns of the factor matrices of
the tensor decomposition, or alternatively, the pattern of interactions between
different modes of the tensor which are captured by the equivalent core tensor.
Some tensor prerequisites with a particular emphasis on mode combination using
Kronecker products of canonical vectors that makes easier matricization
operations, are first introduced. This Kronecker product based approach is also
formulated in terms of the index notation, which provides an original and
concise formalism for both matricizing tensors and writing tensor models. Then,
after a brief reminder of PARAFAC and Tucker models, two families of
constrained tensor models, the co-called PARALIND/CONFAC and PARATUCK models,
are described in a unified framework, for order tensors. New tensor
models, called nested Tucker models and block PARALIND/CONFAC models, are also
introduced. A link between PARATUCK models and constrained PARAFAC models is
then established. Finally, new uniqueness properties of PARATUCK models are
deduced from sufficient conditions for essential uniqueness of their associated
constrained PARAFAC models
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