1,721,331 research outputs found
Impact of the genus Amphistegina on the benthic foraminiferal association of the Pelagian Islands, an example of invasion in the Central Mediterranean Sea
No full textIn recent years the Mediterranean Sea is increasingly subject to colonization by non-indigenous marine organisms, many of which migrate through the Suez Canal. Its opening, which took place in 1869, connected two different biogeographical provinces after millions of years, facilitating the migration of over 600 nonindigenous species, some of which are seriously threatening the native biodiversity. This study shows the results of benthic foraminiferal analyses carried out on algal and sediment samples collected in 2014 around the Pelagian Islands (Lampedusa and Linosa). These islands, starting from 2005 (the year of the first report), are undergoing the invasion of the non-native Indo-Pacific species Amphistegina lobifera Larsen. The obtained data have been compared with those of previous sampling carried out in 2005 and 2009 (Caruso & Cosentino, 2014). This comparison highlights how, in most cases, A. lobifera is increasing its abundance dominating the assemblages with percentages over 50% and causing the drastic decrease of the native species. Its carbonatic tests, accumulated on the Linosa seabed are progressively changing the composition of marine
sediments and for the first time are also giving rise to accumulations in the coastal environment, inside pools filled during storm surges, as happens in the Indo-Pacific atolls. These results show how, in just a few years, some non-indigenous foraminifera are capable of massively colonize new environments, modifying native biodiversity and influencing sedimentary processes.
Caruso A. & Cosentino C. (2014). The first colonization of the Genus Amphistegina and other exotic benthic foraminifera of the Pelagian Islands and south-eastern Sicily (central Mediterranean Sea). Mar. Micropal., 111, 38-52, https://doi. org/10.1016/j.marmicro.2014.05.002
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Sufficient conditions for finite-time stability and stabilization of nonlinear quadratic systems
No full textIn this paper we deal with the finite-time stability problem for
quadratic systems. Such class of systems plays an important role in the
modeling of a wide class of nonlinear processes (electrical, robotic, biological,
etc.). The main results of the paper consist of two sufficient conditions
for finite-time stability analysis and finite-time stabilization via static state
feedback; both conditions are given in terms of the feasibility of a convex
optimization problem, involving linear matrix inequalities. A numerical example
illustrates the applicability of the proposed technique
An insight into tumor dormancy equilibrium via the analysis of its domain of attraction
No full textThe trajectories of the dynamic system which regulates the competition between the populations of
malignant cells and immune cells may tend to an asymptotically stable equilibrium in which the sizes of
these populations do not vary, which is called tumor dormancy. Especially for lower steady-state sizes of
the population of malignant cells, this equilibrium represents a desirable clinical condition since the
tumor growth is blocked. In this context, it is of mandatory importance to analyze the robustness of this
clinical favorable state of health in the face of perturbations. To this end, the paper presents an
optimization technique to determine whether an assigned rectangular region, which surrounds an
asymptotically stable equilibrium point of a quadratic systems, is included into the domain of attraction
of the equilibrium itself. The biological relevance of the application of this technique to the analysis of
tumor growth dynamics is shown on the basis of a recent quadraticmodel of the tumor–immune system
competition dynamics. Indeed the application of the proposedmethodology allows to ensure that a given
safety region, determined on the basis of clinical considerations, belongs to the domain of attraction of
the tumor blocked equilibrium; therefore for the set of perturbed initial conditions which belong to such
region, the convergence to the healthy steady state is guaranteed. The proposed methodology can also
provide an optimal strategy for cancer treatment
- …
