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Search Results: 1 - 10 of 401583 matches for " Marchetti M "
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Some comments on forest resource assessments according to international standards
Marchetti M,Mariano A
Forest@ , 2006,
Abstract: La conoscenza della notevole dipendenza dell’uomo dalle foreste è ormai nota: esse non offrono soltanto legno e altri prodotti, ma assumono un ruolo multifunzionale fondamentale. E’ purtroppo noto che numerosi paesi sfruttano le proprie risorse forestali in modo accelerato ed è preoccupante che tra questi ci siano grandi nazioni, con gli ambiti forestali più considerevoli in relazione alla superficie forestale mondiale. Diviene quindi fondamentale il reperimento di informazioni attendibili sulla consistenza e lo stato delle foreste e per verificare i cambiamenti nel tempo della loro estensione. Il monitoraggio su ampia scala consente di valutare lo stato dell’ambiente naturale e le condizioni degli habitat forestali. E’ quindi trattata la storia delle rilevazioni delle risorse forestali negli ultimi 60 anni, realizzate in particolare dalla FAO, che ha recentemente pubblicato i primi risultati dell’ultimo Forest Resource Assessment (FRA 2005), per fornire informazioni aggiornate e comparabili sul settore forestale a politici, scienziati ed opinione pubblica. Il rapporto FRA 2005 ha anche fornito una descrizione sulla situazione delle risorse forestali a scala nazionale, delineando l’immagine che l’Italia offre al mondo del proprio patrimonio boschivo. Anche a livello europeo si registra un interesse crescente per una migliore conoscenza quantitativa e qualitativa dei patrimoni forestali, divenendo fondamentale allineare le politiche forestali ai reciproci impegni internazionali assunti dai Paesi membri e dalla stessa UE, come dimostra la MCPFE, processo sul reporting a mezzo di indicatori di gestione sostenibile delle foreste. D’altro canto, in Europa sono in corso una serie di azioni di supporto agli obiettivi della gestione forestale sostenibile, tra cui l’EU Forest Action Plan, che si pone l’obiettivo di rivisitare le esistenti regolamentazioni in ambito comunitario per facilitare il coordinamento, la comunicazione e la cooperazione tra i diversi settori politici che influenzano le attività forestali.
The effects of okadaic acid on Enchytraeus crypticus (Annelida: Oligochaeta)
A Franchini,M Marchetti
Invertebrate Survival Journal , 2006,
Abstract: We describe the morpho-functional effects of different concentrations of okadaic acid (OA) on specimens of Enchytraeus crypticus. The results demonstrate that this experimental model is very sensitive to the treatment and presents time- and dose-related effects mainly involving an immune response associated with a reaction in the chloragogenous tissue. At the lower dose (100 nM), the main organs do not appear particularly affected except for a swelling of the coelomatic cavity and an increased number of circulating coelomocytes. At the higher dose (200 nM), the chloragogenous tissue extends in volume to occupy the body cavity almost completely, while the circulating amoebocytes and chloragocytic cells undergo conformational changes. At the highest OA dose (400 nM), there is a general cell suffering in the main animal organs. In control animals, the immunocytochemical reaction with anti-IL-6 antibody is positive in neuron cell bodies and fibres from the ventral nerve cord and in circulating amoebocytes. Following OA treatment, fewer immunoreactive cells are seen in the damaged nervous tissue, and the high number of recruited amoebocytes is also positive.
Independencies Induced from a Graphical Markov Model After Marginalization and Conditioning: The R Package ggm
Giovanni M. Marchetti
Journal of Statistical Software , 2006,
Abstract: We describe some functions in the R package ggm to derive from a given Markov model, represented by a directed acyclic graph, different types of graphs induced after marginalizing over and conditioning on some of the variables. The package has a few basic functions that find the essential graph, the induced concentration and covariance graphs, and several types of chain graphs implied by the directed acyclic graph (DAG) after grouping and reordering the variables. These functions can be useful to explore the impact of latent variables or of selection effects on a chosen data generating model.
Modification of the Magnetic Flux-Line Interaction at a Superconductor's Surface
M. Cristina Marchetti
Physics , 1992,
Abstract: The pair interaction between magnetic flux lines in a semi-infinite slab of an anisotropic type-II superconductor in an external field is derived in the London limit. The case where the applied field is normal to the superconductor/vacuum interface is considered. The presence of stray fields near the surface leads to an additional contribution to the repulsive interaction between flux lines that vanishes exponentially with the distance from the interface. The pair interaction is used to obtain the continuum elastic energy of a distorted semi-infinite flux-line array. The presence of the superconductor/vacuum interface yields surface contributions to the compressional and tilt elastic constants.
Driven vortices in confined geometry: the Corbino disk
M. Cristina Marchetti
Physics , 2000, DOI: 10.1016/S0921-4534(00)00760-7
Abstract: The fabrication of artificial pinning structures allows a new generation of experiments which can probe the properties of vortex arrays by forcing them to flow in confined geometries. We discuss the theoretical analysis of such experiments in both flux liquids and flux solids, focusing on the Corbino disk geometry. In the liquid, these experiments can probe the critical behavior near a continuous liquid-glass transition. In the solid, they probe directly the onset of plasticity.
Models of plastic depinning of driven disordered systems
M. Cristina Marchetti
Physics , 2005, DOI: 10.1007/BF02704171
Abstract: Two classes of models of driven disordered systems that exhibit history-dependent dynamics are discussed. The first class incorporates local inertia in the dynamics via nonmonotonic stress transfer between adjacent degrees of freedom. The second class allows for proliferation of topological defects due to the interplay of strong disorder and drive. In mean field theory both models exhibit a tricritical point as a function of disorder strength. At weak disorder depinning is continuous and the sliding state is unique. At strong disorder depinning is discontinuous and hysteretic.
Depinning and plasticity of driven disordered lattices
M. Cristina Marchetti
Physics , 2005, DOI: 10.1007/3-540-33204-9_9
Abstract: We review in these notes the dynamics of extended condensed matter systesm, such as vortex lattices in type-II superconductors and charge density waves in anisotropic metals, driven over quenched disorder. We focus in particular on the case of strong disorder, where topological defects are generated in the driven lattice. In this case the repsonse is plastic and the depinning transition may become discontinuous and hysteretic.
Family murder in post-apartheid South Africa: reflections for mental health professionals
M C Marchetti-Mercer
Health SA Gesondheid , 2003, DOI: 10.4102/hsag.v8i2.128
Abstract: In the late eighties the phenomenon of family murder was closely linked to Afrikaans-speaking families faced withpolitical change and uncertainty. Opsomming In die laat 1980s het die opvatting ontstaan dat daar ’n noue verband bestaan tussen gesinsmoord en Afrikaansprekende gesinne wat met politieke veranderinge en onsekerheid gekonfronteer word. *Please note: This is a reduced version of the abstract. Please refer to PDF for full text.
Nonequilibrium Statistical Mechanics of Self-propelled Hard Rods
Aparna Baskaran,M. Cristina Marchetti
Physics , 2010, DOI: 10.1088/1742-5468/2010/04/P04019
Abstract: Using tools of nonequilibirum mechanics, we study a model of self-propelled hard rods on a substrate in two dimensions to quantify the interplay of self-propulsion and excluded-volume effects. We derive of a Smoluchowski equation for the configurational probability density of self-propelled rods that contains several modifications as compared to the familiar Smoluchowski equation for thermal rods. As a side-product of our work, we also present a purely dynamical derivation of the Onsager form of the mean field excluded volume interaction among thermal hard rods.
Spinodal decomposition in polarised Fermi superfluids
A. Lamacraft,F. M. Marchetti
Physics , 2007, DOI: 10.1103/PhysRevB.77.014511
Abstract: We discuss the dynamics of phase separation through the process of spinodal decomposition in a Fermi superfluid with population imbalance. We discuss this instability first in terms of a phenomenological Landau theory. Working within the mean-field description at zero temperature, we then find the spinodal region in the phase diagram of polarisation versus interaction strength, and the spectrum of unstable modes in this region. After a quench, the spinodal decomposition starts from the Sarma state, which is a minimum of the free energy with respect to the order parameter at fixed density and polarisation and a maximum at fixed chemical potentials. The possibility of observing non-trivial domain structures in current experiments with trapped atomic gases is discussed.
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