5,777 research outputs found
Evidence from multivariate morphometric study of the quercus pubescens complex in southeast Italy
The name Quercus pubescens s.l. encompasses a complex of deciduous oak taxa with mainly southeastEuropean
distribution and a large ecological niche. As the easternmost region of Italy, Apulia is
rather isolated from a geographical and physiographical viewpoint and counts the highest number
of oak species (10). In the taxonomic and phytosociological literature, the occurrence of several
species belonging to the Quercus pubescens collective group is reported for this region. In order to
verify if different sets of morphological characters are associated with different taxa, 24 populations
of Quercus pubescens s.l. located in different ecological-geographical areas of Apulia were sampled.
A total of 367 trees, 4254 leaves and 1120 fruits were collected and morphologically analysed.
Overall, 25 morphological characters of oak leaves and fruits were statistically treated using both
univariate and multivariate analysis. Nested ANOVA showed that leaves collected from a single tree
exhibited a degree of morphological variability higher than that observed when comparing leaves
coming from different trees of the same population and from different trees of different populations
as well. Almost all the morphological characters analysed exhibited a continuous trend of variation
so that none of them can be used as a character to discriminate between populations. Only leaf
and fruit âsizeâ and fruit petiole length emerged as slightly discriminating characters. Our results
suggest that it is unlikely that more than one species belonging to the Quercus pubescens complex
occurs in the Apulia region. Comparison between the Apulian populations and a genetically
pure Q. pubescens population coming from a different area (the Molise region) strengthened the
assumption as to the existence of a single species that can provisionally be classified under the name
of Q. pubescens s.
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A management architecture for active networks
In this paper we present an architecture for network and applications management, which is based on the Active Networks paradigm and shows the advantages of network programmability. The stimulus to develop this architecture arises from an actual need to manage a cluster of active nodes, where it is often required to redeploy network assets and modify nodes connectivity. In our architecture, a remote front-end of the managing entity allows the operator to design new network topologies, to check the status of the nodes and to configure them. Moreover, the proposed framework allows to explore an active network, to monitor the active applications, to query each node and to install programmable traps. In order to take advantage of the Active Networks technology, we introduce active SNMP-like MIBs and agents, which are dynamic and programmable. The programmable management agents make tracing distributed applications a feasible task. We propose a general framework that can inter-operate with any active execution environment. In this framework, both the manager and the monitor front-ends communicate with an active node (the Active Network Access Point) through the XML language. A gateway service performs the translation of the queries from XML to an active packet language and injects the code in the network. We demonstrate the implementation of an active network gateway for PLAN (Packet Language for Active Networks) in a forty active nodes testbed. Finally, we discuss an application of the active management architecture to detect the causes of network failures by tracing network events in time
Critical behaviour of the O(3) nonlinear sigma model with topological term at theta=pi from numerical simulations
We investigate the critical behaviour at theta=pi of the two-dimensional O(3)
nonlinear sigma model with topological term on the lattice. Our method is based
on numerical simulations at imaginary values of theta, and on scaling
transformations that allow a controlled analytic continuation to real values of
theta. Our results are compatible with a second order phase transition, with
the critical exponent of the SU(2)_1 Wess-Zumino-Novikov-Witten model, for
sufficiently small values of the coupling.Comment: Revised version. 24 pages, 7 figure
Central serotonin-2A (5-HT2A) receptor dysfunction in depression and epilepsy : the missing link?
5-Hydroxytryptamine 2A receptors (5-HT2A-Rs) are G-protein coupled receptors. In agreement with their location in the brain, they have been implicated not only in various central physiological functions including memory, sleep, nociception, eating and reward behaviors, but also in many neuropsychiatric disorders. Interestingly, a bidirectional link between depression and epilepsy is suspected since patients with depression and especially suicide attempters have an increased seizure risk, while a significant percentage of epileptic patients suffer from depression. Such epidemiological data led us to hypothesize that both pathologies may share common anatomical and neurobiological alteration of the 5-HT2A signaling. After a brief presentation of the pharmacological properties of the 5-HT2A-Rs, this review illustrates how these receptors may directly or indirectly control neuronal excitability in most networks involved in depression and epilepsy through interactions with the monoaminergic, GABAergic and glutamatergic neurotransmissions. It also synthetizes the preclinical and clinical evidence demonstrating the role of these receptors in antidepressant and antiepileptic responses.peer-reviewe
Quantum dynamics of a vibrational mode of a membrane within an optical cavity
Optomechanical systems are a promising candidate for the implementation of
quantum interfaces for storing and redistributing quantum information. Here we
focus on the case of a high-finesse optical cavity with a thin vibrating
semitransparent membrane in the middle. We show that robust and stationary
optomechanical entanglement could be achieved in the system, even in the
presence of nonnegligible optical absorption in the membrane. We also present
some preliminary experimental data showing radiation-pressure induced optical
bistability.Comment: 6 pages, 2 figures. Work presented at the conference QCMC 2010 held
on 19-23 July 2010 at the University of Queensland, Brisbane, Australi
Selective Deamidation and Enzymatic Methylation of Seminal Ribonuclease
Isoenzymatic forms alfa2, alfa-beta, and beta2 of bovine seminal ribonuclease are generated by the transformation of beta-type into alfa-type subunit through deamidation of a single amide group. The residue involved in this selective deamidation has been identified as Asn67 . Deamidation occurs by formation of a cyclic imide intermediate involving the Gly at position 68. Opening of the cyclic imide may occur on either side of the nitrogen, generating
both the normal alfa-aspartyl and an isoaspartyl residue at position 67. The alfa-carboxyl of the isoaspartyl residue is effectively methylated by bovine brain protein carboxylmethyltransferase
Quantum dynamics of a high-finesse optical cavity coupled with a thin semi-transparent membrane
We study the quantum dynamics of the cavity optomechanical system formed by a
Fabry-Perot cavity with a thin vibrating membrane at its center. We first
derive the general multimode Hamiltonian describing the radiation pressure
interaction between the cavity modes and the vibrational modes of the membrane.
We then restrict the analysis to the standard case of a single cavity mode
interacting with a single mechanical resonator and we determine to what extent
optical absorption by the membrane hinder reaching a quantum regime for the
cavity-membrane system. We show that membrane absorption does not pose serious
limitations and that one can simultaneously achieve ground state cooling of a
vibrational mode of the membrane and stationary optomechanical entanglement
with state-of-the-art apparatuses.Comment: 14 pages, 7 figure
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