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Instability of the O(5) multicritical behavior in the SO(5) theory of high-Tc superconductors
No full textWe study the nature of the multicritical point in the three-dimensional
O(3)+O(2) symmetric Landau-Ginzburg-Wilson theory, which describes the
competition of two order parameters that are O(3) and O(2) symmetric,
respectively. This study is relevant for the SO(5) theory of high-Tc
superconductors, which predicts the existence of a multicritical point in the
temperature-doping phase diagram, where the antiferromagnetic and
superconducting transition lines meet.
We investigate whether the O(3)+O(2) symmetry gets effectively enlarged to
O(5) approaching the multicritical point. For this purpose, we study the
stability of the O(5) fixed point. By means of a Monte Carlo simulation, we
show that the O(5) fixed point is unstable with respect to the spin-4 quartic
perturbation with the crossover exponent , in substantial
agreement with recent field-theoretical results. This estimate is much larger
than the one-loop -expansion estimate , which has
often been used in the literature to discuss the multicritical behavior within
the SO(5) theory. Therefore, no symmetry enlargement is generically expected at
the multicritical transition.
We also perform a five-loop field-theoretical analysis of the
renormalization-group flow. It shows that bicritical systems are not in the
attraction domain of the stable decoupled fixed point. Thus, in these
systems--high-Tc cuprates should belong to this class--the multicritical point
corresponds to a first-order transition
The Wandering Token: Congestion Avoidance of a Shared Resource
No full textIn a distributed system where scalability is an issue, like in a GRID, the problem of enforcing mutual exclusion often arises in a soft form: the infrequent failure of the mutual exclusion predicate is tolerated, without compromising the consistent operation of the overall system. For instance this occurs when the operation subject to mutual exclusion requires massive use of a shared resource. We introduce a scalable soft mutual exclusion algorithm, based on token passing: one distinguished feature of our algorithm is that instead of introducing an overlay topology we adopt a random walk approach. The consistency of our proposal is evaluated by simulation, and we exemplify its use in the coordination of large data transfers in a backbone based network
A Compositional Coalgebraic Model of Monadic Fusion Calculus
No full textWe propose a compositional coalgebraic semantics of the Fusion calculus
of Parrow and Victor in the version with explicit fusions by Gardner and
Wischik. We follow a recent approach developed by the same authors and
previously applied to the pi-calculus for lifting calculi with structural
axioms to bialgebraic models. In our model, the unique morphism to the final
bialgebra induces a bisimilarity relation which coincides with
hyperequivalence and which is a congruence with respect to the operations.
Interesting enough, the explicit fusion approach allows to exploit for the
Fusion calculus essentially the same algebraic structure used for the
pi-calculus
Implicit and Explicit Representation of Approximated Motifs
No full textDetecting repeated 3D protein substructures has become a new crucial
frontier in motifs inference. In \cite{cpm} we have suggested a
possible solution to this problem by means of a new framework in
which the repeated pattern is required to be conserved also in terms
of relations between its position pairs. In our application
these relations are the distances between -carbons of amino
acids in 3D proteins structures, thus leading to a \emph{structural
consensus} as well.
In this paper we motivate some complexity issues claimed (and assumed, but
not proved) in \cite{cpm} concerning inclusion tests between
occurrences of repeated motifs. These inclusion tests are
performed during the motifs inference in \emph{KMRoverlapR}
(presented in \cite{cpm}), but also within other motifs
inference tools such as
\emph{KMRC} (\cite{kmrc}). These involve
alternative representations of motifs, for which
we also prove here some interesting
properties concerning pattern matching issues.
We conclude this contribution with a few tests on cytochrome
P450 protein structures
Proceedings of the CoreGRID Integration Workshop (CGIW'2005)
No full textThe workshop is organised by the Network of Excellence CoreGRID funded by the European Commission under the sixth framework programme IST-2003-2.3.2.8 starting September 1st, 2004. CoreGRID aims at strengthening and advancing scientific and technological excellence in the area of Grid and Peer-to-Peer technologies. To achieve this objective, the network brings together a critical mass of well-established researchers (119 permanent researchers and 165 PhD students) from forty-two institutions who have constructed an ambitious joint programme of activities.
The goal of the workshop is to promote the integration of the CoreGRID network and of the European research community in the area of Grid technologies, in order to overcome the current fragmentation and duplication of efforts in this area. The list of topics of Grid research covered at the workshop includes but is not limited to: knowledge & data management; programming models; system architecture; Grid information, resource and workflow monitoring services; resource management and scheduling;systems, tools and environments;trust and security issues on the Grid
Normal Forms for Stateless Connectors
No full textThe conceptual separation between computation and coordination in distributed computing systems motivates the use of peculiar entities commonly called connectors, whose task is managing the interaction among distributed components. Different kinds of connectors exist in the literature at different levels of abstraction. We focus on a basic algebra of connectors which is expressive enough to model e.g. all the architectural connectors of CommUnity. We first define the operational, observational and denotational semantics of connectors, then we show that the observational and denotational semantics coincide and finally we give a complete normal-form axiomatization
Operations Research Methods and Models for Crisis Prevention and Early Warning
No full textSecurity is one particular global challenge that has recently come
to the fore due to world events and societal changes. Within this
context, one of the areas in which Operations Research can give an
important contribution is the area of early warning and
crisis prevention. This is a challenging research area
requiring a multidisciplinary approach, which has enjoyed an
increased interest in recent years. Here, we will highlight some
of the problems arising in this area in which O.R. techniques can
find useful applications
Elementi di genetica del cane
Get PDFL'opera è composta di tre parti: nella prima parte abbiamo considerato argomenti di base, come i cenni storici sull'evoluzione della genetica animale, le origini del cane, la simbologia, con una notevole sezione dedicata alla terminologia generale (glossario); nella seconda parte è trattata la genetica mendeliana e le sue eccezioni, con quei collegamenti alla genetica delle altre specie che non sempre trova riscontro nei trattati di genetica del cane, anche in lingua inglese; nella terza parte è trattata la genetica dei mantelli del cane, che è la parte della genetica più vicina ai cinofili e contiene diverse foto
Branzini (Dicentrarchus labrax) di diversa provenienza e confronto organolettico delle carni
No full textRIASSUNTO Oggetto della prova sperimentale è stato lo studio delle differenze organolettiche fra le carni di branzini di diversa origine a parità di taglia commerciale. I branzini utilizzati provenivano da pesca in mare, da allevamento a terra in vasca “fredda” e da allevamento a terra in vasca “calda”. Le caratteristiche organolettiche delle diverse derrate sono state valutate mediante test triangolare su campioni di carne sottoposti a 2 tipi di cottura (bollitura e cottura a secco in forno) e sul liquido di cottura. Ciascun assaggiatore nei confronti ortogonali e nei confronti di controllo doveva quindi individuare l’eventuale diversità tra i campioni di carne e tra i liquidi di cottura. Oltre alla diverse rese di preparazione, differenze organolettiche sono state evidenziate fra tutte le tesi sperimentali. La preparazione mediante cottura in forno ventilato ha fornito i risultati più attendibili (2 dei confronti fra tesi diverse 8,40**, 11,45** e 8,40**; 2 del confronto fra tesi uguali = 0,91ns) mentre la cottura in acqua salata ha fornito i risultati meno attendibili sia per la carne (2 dei confronti fra tesi diverse 9,88**, 7,00** e 11,45**; 2 del confronto fra tesi uguali = 8,40**) che per il liquido di cottura (2 dei confronti fra tesi diverse 12,27**, 17,12** e 20,57**; 2 del confronto fra tesi uguali = 5,14*). La valutazione sensoriale effettuata tramite il test triangolare ha mostrato quindi che un gruppo di 9 persone è sufficiente ad individuare differenze fra derrate di diversa origine seppure l’abilità di valutazione si sia confermata una caratteristica fortemente individuale nel caso del pesce (2 = 26,66**). SUMMARY Organoleptic differences between the meat of sea basses of different origin (same marketable size and different ages) were analysed of by mean of a triangular test. The sea basses used in the trial were captured from the fishes living in wildlife (fished) or differently farm raised (in ground “cold” water and in ground “warm” water). The Organoleptic differences were evaluated through the study of different samples: the fishes boiled or cooked in oven, and the fish cooking waters. Every judge had to discover differences between each couple of sample of meat or water-extract in the orthogonal tests with the hidden controls. Dipartimento di Produzioni Animali, Direttore Prof. Paolo Verità. In addition to the yield at cooking, Organoleptic differences were found between every thesis. The oven cooking method gave the best results (2 related to the different thesis 8.40**, 11.45**, and 8.40**; 2 related to the hidden controls = 0.91ns), The water cooking method gave the worst results, either in the boiled meat evaluation (2 related to the different thesis 9.88**, 7.00** e 11.45**; 2 related to the hidden controls = 8.40**) or in the water extract evaluation (2 related to the different thesis 12.27**, 17.12** e 20.57**; 2 related to the hidden controls = 5.14*). The use of the triangular test with only 9 no trained judges is sufficient to analyze fish of different origin, even if results showed that the ability to discriminate the different samples depends on the individual competence (2 = 26.66**)
‘L’effetto tunnel’ mediante tubi bioerodibili nella Nerve Regeneration
No full textRIASSUNTO I nervi periferici possono essere gravemente danneggiati in seguito ad un trauma meccanico, in particolare quando è presente una totale resezione del nervo (neurotmesi). Le difficoltà che si incontrano durante la riunione chirurgica dei monconi nervosi sono: la reazione cicatriziale che si forma attorno al nervo, la reazione granulomatosa in seguito alla sutura microchirurgica, l’interposizione di sangue o altre sostanze sul decorso del nervo in rigenerazione, il corretto allineamento dei monconi nervosi e la tensione nel sito di riunione che si può creare se il gap è molto vasto. Allo scopo di ottenere un perfetto e funzionale ri-allineamento delle fibre neuronali sono state sviluppate numerose tecniche di ricostruzione del gap nervoso, in particolare, ha mostrato risultati considerevoli l’impianto di canali guida polimerici biodegradabili. In questo studio preliminare, sono state realizzate con un sistema di estrusione a caldo guide in Poliuretano, e, successivamente, sono state riempite con specifiche biomolecole di adesione cellulare (gelatina e polilisina). Le guide sono state testate in vitro ed in vivo, prendendo soprattutto in considerazione i parametri elettromiografici dei ratti prima dell’espianto ed i risultati istologici dopo l’espianto. Dal confronto con i risultati ottenuti con l’impiego di tubi in Policaprolattone, un polimero biodegradabile approvato dalla FDA ed usato in molti prodotti commerciali, si può evidenziare una buona rigenerazione sia in vitro che in vivo con un discreto recupero della funzione del tessuto nervoso. SUMMARY Peripheral nerves may be severely compromised as a consequence of mechanical trauma, especially when they present a total resection of the nerve (neurotmesis). The difficulty that we meet during the surgical realignment of the proximal and distal nerve ends are: scar reaction around the nerve, the granulomatous reaction as result of micro-surgically suture, the blood or other material interposition along the nerve in regeneration, a careful alignment of both nerve stumps and the tension at the coaptation site in case of a large gap. In order to obtain a perfect and functional alignment of neuronal fibres different techniques for bridging defects in peripheral nerve have been developed, in particular the implant of biodegradable polymeric guidance channels has shown considerable results. In this study preliminarily polyurethane-based nerve guide have been realised with an extrusion system and then filled with specific cell adhesion biomolecules (gelatine and polylisine). This guides have been tested in vitro and in vivo. In particular during in-vivo experiments an accurate electromyography on the rat before the explant and histology of explanted tube were performed. These results have been compared with those obtained using polycaprolactone tubes, that is a bioerodable polymer approved by FDA and used in several commercial product. The results have shown a good regeneration either in vitro and in vivo with an appreciable restore of neural tissue function