1,720,974 research outputs found
La fauna bentonica associata alla vegetazione sommersa del lago di Posta Fibreno (Lazio).
No full textSpatial distribution and diversity of plant-associated invertebrates in a lotic-lentic ecosystem (Lake Posta Fibreno, Central Italy) and water quality monitoring.
No full textA survey on plant-associated invertebrates in Lake Fibreno was carried out for the first time in 2004 with the aim to evaluate the fauna composition, distribution and diversity, and to define the lake ecological status. The basin (surface area: 0.3 km2; maximum depth:15 m) is an original example of a lotic-lentic system, located in Central Italy in a Reserve classified as a Special Area of Conservation (SAC, European Union Directive 92/43/EEC). The lake originates from a complex of groundwater and surface karstic springs belonging to the Marsica hydrogeologic system and comprises a wide reed stand crossed by canals and the only floating island of the South Europe (diameter: abount 30 m). High flow and constant temperature (10-11 °C) characterize the lake water, which discharges in the Fibreno river at a flow of about 10 m3.sec-1. Aquatic vegetation and invertebrates were collected bimonthly with an hand dredge in six stations during one year. Ten tipically lotic/lentic plant taxa were collected, which colonized mostly the 0-3 m depth range and were distributed according to water flow regimes. High numbers of zoological groups (28) were found, comprising 94 taxa, mostly represented by insects (34) and secondarily by nematodes, oligochaetes, gastropods and crustaceans, thank to the assemblage of invertebrates typical of lentic and lotic waters. The presence of indicator taxa and the measure of some bioindices performed on the invertebrate community have indicated an oligo-mesotrophic condition, with a trophic gradient varying from oligotrophy to mesotrophy according to different plant composition and lake hydrodynamics. Although some signs of eutrophication were revelead by high phosphate contents in the water, high concentration of organic matter in the sediments, disappearance of vegetation with respect to the past years, extensive growth of the sulfumbacterium Thiopedia rosea on the bottom, the plant-associated invertebrate community still showed a good ecological status following the positive effect of dilution-removal of nutrients caused by the continuous water flow of the lake
Spatial distribution of plant-associated invertebrates and environmental bioassessment in a natural riverine Lake (Lake Fibreno, Central Italy).
No full textLake Fibreno is a Mediterranean riverine lake located in Central Italy and fed by large flows of groundwater and characterized by the presence of a wide reed stand area and of the only floating island of the South Europe. It is enclosed in a Natural Reserve recognized as Special Area of Conservation (SAC-IT6050015) for the presence of habitats and species (92/43/EEC) of relevant scientific interest. In this paper, we compare the plant-associated meio-macrobenthic invertebrates among sites with different environmental characteristics. Both vegetation and invertebrates of Lake Fibreno were well diversified and abundant and were composed of a mixing of species typical of lentic and lotic waters. Our results show that a gradient of orthophosphate and nitrite contents and current velocity appeared to be the driver factors affecting the flora and fauna spatial distribution at the sampling sites. To obtain a bioassessment of the ecological quality of the vegetation zone, we compared the riverine Lake Fibreno with typical lentic lakes previously studied in Central Italy. We selected metrics, such as macrophyte belt extent and taxa richness, invertebrate species richness and Shannon diversity, ETOM (Ephemeropta + Trichoptera + Odonata + Mollusca), ETOC (Ephemeropta + Trichoptera + Odonata + Coleoptera) and LCrM (Large Crustacea + Mollusca). The comparison indicated a good ecological status of the vegetation zone of Lake Fibreno mainly due to the continuous washout effects (dilution and fast water removal) which reduce the nutrient content available for phytoplankton and maintain the high transparency and good oxygenation of the lake waters
Water level reduction and plant associated invertebrates in the deep Lake Albano (Central Italy).
No full textThe volcanic Lake Albano is one of the deepest Italian lakes (max. depth: 175m), subjected from 1960 to considerable eco-morphological modifications taken to encourage recreational activities. Recent climate changes and increasing amount of water drawing from the cathment basin further deteriorated the littoral area, following the water level reduction of about 5 m, which bared wide parts of lake bottoms, today transformed in emerged sandy shores. The comparison of recent preliminary data with a previous study on littoral invertebrates (1986) displayed the almost total disappearance of the aquatic vegetation in the whole perimeter, including also several parts of common reed bed. In some stations plants were completely replaced by sand characterized by predominance of coarse fractions. The disappearance of plants produced a dramatic decrease of the fauna abundance at shallow depths (0-4 m depth range) and, excluding one station, the total disappearance of fauna at deeper littoral areas (4-8 m). This decrease of production was associated with a slight reduction of total phosphorus in the water and a transparency increase (mean: 7.4 m in 1986, 9.5 m in 2008). In spite of this serious deterioration, the same number of plant taxa (9 in 1986 and 8 in 2008) and faunal groups (18 in 1986 and 20 in 2008) was still observed. The preservation of a high number of faunal groups is a sign of the high homeostatic capability of the littoral community, which represents the most important source of lake biodiversity and the basis of any possible amelioration of the environmental conditions
Capacitor Placement in Three-phase Distribution Systems with Nonlinear and Unbalanced Loads
No full textAn Advanced Collision Avoidance Algorithm considering Ellipsoidal Safety Bubble
No full textAbstract — This paper presents an optimal three-dimensional analytical solution for aircraft non-cooperative collision avoidance, having the capability of avoiding a safety bubble with ellipsoidal shape. Based on an analytical approach, a closed form solution to a proper kinematic optimization problem is here derived, which implies the simultaneous change of all control variables (speed module, track and slope angles). The proposed algorithm does not require the solution of any programming problem, thus resulting suitable for real-time applications. Moreover, the availability of an analytical solution allows the application of well assessed control analysis and synthesis techniques in order to improve stability and performance robustness. The proposed algorithm performs optimal avoidance maneuvers, by minimizing aircraft deviation from its nominal trajectory. From a practical point of view, the implementation of the proposed algorithm implies that, in a pair-wise non-cooperative collision avoidance, the speed vector of the aircraft implementing the proposed control strategy is continuously changed with the aim of skimming the safety bubble surrounding the other aircraft (considered as an intruder). The effectiveness of the algorithm here described has been proved by means of numerical simulations, where proper conflict scenarios which take into account aircraft dynamics and on-board sensors errors and limitations have been considered
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
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