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 $p_{ij}$ for a connection between two occupied sites $i,j$ at a distance $r_{ij}$ decays as a power law, i.e. $p_{ij} = \rho/[r_{ij}^\alpha N^{1-\alpha}]$ when $0 \le \alpha < 1$, and $p_{ij} = \rho/[r_{ij} \ln(N)]$ when $\alpha = 1$. Site dilution means that the occupancy probability of a site is $0 < p_s \le 1$. 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 $\alpha=0$ with $p_s =1$ is well-known, being the exactly solvable mean-field model. The percolation order parameter $P_\infty$ is investigated numerically for different values of $\alpha$, $p_s$ and $\rho$. We show that in the ranges $0 \le \alpha \le 1$ and $0 < p_s \le 1$ the percolation order parameter $P_\infty$ depends only on the average connectivity $\gamma$ of sites, which can be explicitly computed in terms of the three parameters $\alpha$, $p_s$ and $\rho$

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 $N^{th}$ 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