512 resultados para 573 - Biologia general i teòrica


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Comentaris a les Resolucions de la Direcció General de Dret i Entitats Jurídiques de 31 de juliol 2006, de 7 de setembre 2006, de 18 de setembre 2006, de 9 d'octubre 2006, de 30 d¿octubre 2006, de 31 d'octubre 2006 i de 24 de novembre 2006.

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Comentaris a les Resolucions de la Direcció General de Dret i Entitats Jurídiques de 5 de maig 2008, 16 de juliol 2008 i 29 de setembre 2008.

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Comentaris a les Resolucions de la Direcció General de Dret i Entitats Jurídiques 22 de gener 2007, de 24 de gener 2007, de 15 de febrer 2007, de 16 de febrer 200 i de 19 de febrer 2007.

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Comentaris a les Resolucions de la Direcció General de Dret i Entitats Jurídiques de 2 de maig 2007, de 10 de juliol 2007, d'11 de juliol 2007, de 16 de juliol 2007, de 17 de juliol 2007, de 22 d'octubre 2007, de 21 de desembre 2007 i 4 de febrer 2008.

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Comentaris a les Resolucions de la Direcció General de Dret i Entitats Jurídiques de 30 de març 2006, de 18 d'abril 2006, de 10 de maig 2006, de 12 de maig 2006, de 19 de maig 2006, de 22 de maig 2006, de 23 de maig 2006 i de 7 de juliol 2006.

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Comentaris a les Resolucions de la Direcció General de Dret i Entitats Jurídiques de 6 de febrer 2008, 8 de febrer 2008, 20 de febrer 2008, 2 d'abril 2008 i 18 d¿abril 2008.

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Comentaris a les Resolucions de la Direcció General de Dret i Entitats Jurídiques de 20 de març 2007, de 26 d'abril 2007, de 27 d'abril 2007 i de 30 d'abril 2007

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We derive a Hamiltonian formulation for the three-dimensional formalism of predictive relativistic mechanics. This Hamiltonian structure is used to derive a set of dynamical equations describing the interaction among systems in perturbation theory.

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We develop a full theoretical approach to clustering in complex networks. A key concept is introduced, the edge multiplicity, that measures the number of triangles passing through an edge. This quantity extends the clustering coefficient in that it involves the properties of two¿and not just one¿vertices. The formalism is completed with the definition of a three-vertex correlation function, which is the fundamental quantity describing the properties of clustered networks. The formalism suggests different metrics that are able to thoroughly characterize transitive relations. A rigorous analysis of several real networks, which makes use of this formalism and the metrics, is also provided. It is also found that clustered networks can be classified into two main groups: the weak and the strong transitivity classes. In the first class, edge multiplicity is small, with triangles being disjoint. In the second class, edge multiplicity is high and so triangles share many edges. As we shall see in the following paper, the class a network belongs to has strong implications in its percolation properties.

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Outgoing radiation is introduced in the framework of the classical predictive electrodynamics using LorentzDiracs equation as a subsidiary condition. In a perturbative scheme in the charges the first radiative self-terms of the accelerations, momentum and angular momentum of a two charge system without external field are calculated.

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Ten years of demographic and genetic monitoring of Stachys maritima in Catalonia (2001-2010). Implications for a recovery plan.- Stachys maritima is a species typical of the coastal dunes, with a wide distribution within the Mediterranean Basin. In spite of this, the species shows a clear regression. In Catalonia, it has been observed an important reduction of its populations since early 20th century, where it has disappeared from several localities in which it was relatively common (Tarragonès, Barcelonès). Herein we present the results of the demographic monitoring of the species during the last 10 years (2001-2010) in the known localities in Catalonia. Besides corroborating the disappearance (northern Sant Martí d'Empúries), the re-discovering (Llobregat Delta beach) and the detection of new populations (inner dunes of the Montgrí), a large year-to-year fluctuation of the monitored populations is stated; the possible reasons are discussed. In addition, the present work also includes the results of the allozyme diversity analysis of the new detected populations as well as the rediscoveries of the period 2004-2008, which were not included in a former study of genetic diversity carried out in 2002-2003. It is necessary to emphasize that the contribution of the new populations to the genetic diversity of Stachys maritima is very small, which can be attributed to their limited population size and /or to founder effects. Despite that the species is included in the Annex 2 ('En Perill d'Extinció') within the Catàleg de Flora Amenaçada de Catalunya (Catalogue of Endangered Flora of Catalonia), and some 'soft' conservation measures have been applied at local level (signposting of the beach accesses, environmental education, etc.) coupled with other more significant measures (e.g. translocation of individuals discovered in an artificial sandbank), it would be necessary the coordinated action and the scientific support of any initiative of conservation that could be carried out. The general frame to initiate actions of conservation should be the recovery plan of Stachys maritima, whose draft and application is mandatory in accordance to the Catàleg.

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The first part of a general survey of the vegetation of Catalonia andAndorra, this paper reports all the phytocoenological associations and subassociations recorded in this area. For each community, we provide the correct name and usual synonyms, its typification (where appropriate), all the references including relevés, and the most outstanding features of its structure, species composition, ecology, distribution and diversity. Moreover, associations and subassociations are ordered appropriately in a syntaxonomic scheme. Syntaxonomic ranks are considered in a fairly broad, conservative sense. This classification established 101 associations, which correspond to the classes Lemnetea, Zosteretea, Potametea, Littorelletea, Montio-Cardaminetea, Phragmiti-Magnocaricetea, Scheuchzerio-Caricetea, Isoeto-Nanojuncetea and Molinio-Arrhenatheretea.

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Artemisio annuae-Conietum maculati ass. nova is described from the lower valley of Llobregat and Besòs rivers. Communities of this association, which is included into the Silybo-Urticion Sissingh 1950 alliance, are hygronitrophilous meadows up to 3 m high and more than 80% of vegetation cover. They are commonly restricted to the river bed and are made up almost exclussively by therophytes and hemicryptophytes. However, the mostcharacteristic trend of these herbaceous communities is the abundance of neophytes, which stand for 20% of the species but close to 50% of vegetation cover. Several widespread neophytes such as Aster squamatus, Conyza spp., Xanthium spp. are commonly found in these communities, and other rare aliens such as Artemisia annua, Rumex cristatus and R. palustris have recently been recorded. Ecological implications of the neophyte abundance in these communities are discussed in relation to the role of human disturbance and population biology of alien species in general.

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S'ha posat a informació pública l'Avantprojecte de Llei de la Biodiversitat i el Patrimoni Natural de Catalunya, esperada des de fa força anys i que ha de ser el marc general de tota l'activitat de conservació i gestió de la diversitat biològica en el futur del nostre país. A la tercera part de l'article s'analitza el tractament que hi rep la flora, així com les conseqüències pràctiques que se'n derivaran.