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Some analytical results of chemotaxis hyberbolic parabolic models on network
No full textwe study a hyperbolic and parabolic model of pde arising from a biological problem and defined on netowrks. We give some results of existence and uniqueness of solution of these problems and we study the asymptotic behaviour of solution in a special case
FUNZIONI E RESPONSABILITA’ DEI SOGGETTI GARANTI DELL’OBBLIGO DI SICUREZZA NEL TESTO UNICO N. 81 DEL 2008.
No full textAspetti dell'identità gallica nel Tardo Impero alla luce delle testimonianze di alcuni scrittori gallo-romani (fine III - fine V secolo d.C.)
No full textBio-Inspired Dynamic Radio Access in Cognitive Networks based on Social Foraging Swarms
No full textThere is strong trend, in current research on communication and sensor networks,
to study selforganizing, self-healing systems. This poses great challenges
to the research on decentralized systems, but at the same offers great potentials
for future developments, especially in view of the current trend towards miniaturized
systems. Even if the development of self-organizing systems is probably
at the beginning, biological systems offers many examples of self-organization
and selfhealing. This is as testified, for example, by swarming behaviors, brain
activity, and so on. It is then of great interest to derive mathematical models of
biological systems and see how they can suggest novel design tools for engineers.
Signal Processing can play a big role in this cross-fertilization, as it can help
to find out manageable mathematical problems, study their behavior and test
the performance in the presence of disturbances. The challenge is to establish a
cross-fertilization of ideas from biological to artificial systems, as well as to help
understanding biological systems as such.
This dissertation considers the problem of dynamic radio access based on sensing
in cognitive radio networks. In particular, we follow a rather alternative path
with respect to more conventional approaches and, inspired by biological models,
we formulate the search for radio resources, i.e. time and frequency slots, as the
search for food by a flock of birds swarming in a cooperative manner, but without
any centralized control. The interference distribution in the time-frequency
plane takes the role of the food spatial distribution: The birds (radio nodes) fly (allocate their resources) over the regions (time-frequency domain) where there
is more food (less interference). During the flight, the birds move (choose their
time-frequency slots) in a coordinated way, even in the absence of any central
control, in order to avoid collisions (conflicts over common radio resources), yet
maintaining the swarm cohesion (i.e., avoiding unnecessary spread in the occupancy
of the time-frequency plane). This procedure is applied to the dynamic
resource allocation in the frequency domain and in the time-frequency domain,
where the primary users in a cognitive radio system are modeled as statistically
independent homogeneous continuous-time Markov processes.
A rigorous mathematical analysis of the proposed algorithm is also derived. First,
we study the stability and the cohesiveness of the swarm in case of local interactions
among the nodes, providing closed form expressions for the upper and
lower bounds of the swarm size as a function of the network connectivity. Then,
using stochastic approximation arguments, we derive the convergence properties
of the swarming algorithm in the presence of random disturbances introduced by
realistic channels, i.e., link failures, quantization, noise and estimation errors.
Spectrum sensing is a critical prerequisite in envisioned applications of wireless
cognitive radio networks which promise to resolve the perceived bandwidth
scarcity versus under-utilization dilemma. Creating an interference map of the
operational region plays an instrumental role in enabling spatial frequency reuse
and allowing for dynamic spectrum allocation in a hierarchical access model comprising
primary and secondary users. For such purpose, a distributed technique
for cooperative spectrum estimation in cognitive radio systems is proposed based
on a basis expansion model of the power spectral density map in frequency. The
proposed method, based on diffusion adaptation algorithms, estimates and learns
the interference profile through local cooperation and without the need for a
central processor. Convergence and mean square analysis of the diffusion filter
applied to the distributed cooperative sensing problem is also derived. Finally, it is proposed a dynamic resource allocation technique combining a distributed
diffusion algorithm, for implementing cooperative sensing, with a swarming
technique, for allocating resources in a parsimonious way (i.e., avoiding unnecessary
spread in the frequency domain), yet avoiding collisions. In particular,
the procedure is applied to the dynamic resource allocation problem in the frequency
domain. Numerical results show the improvement that results in the
resource allocation performance due to the cooperative estimation of the spectrum.
Furthermore, it is shown how the proposed technique endows the resulting
bio-inspired network with powerful learning and adaptation capabilities
Sbarramenti fluviali e rifornimento idrico nel Lazio in epoca romana: il caso del fiume Aniene
No full textA study of the water use in the Aniene Valley (Latium, Central Italy) in relation to the Roman Occupation of the Valley, by means of the analysis of one particular type of monument, the dam. The project anticipated the carrying out of field surveys, the collection of bibliographic and archival materials, the study of historical maps and the design of a GIS
Challenges to Sustainable Knowledge Transfer in cross-cultural Teacher Education
No full textThe policy of transferring international educational knowledge across cultural and geographical borders has become a common practice for the international community, especially after the 1990 Education for All (EFA) agreement. Egypt is complying with this policy by relying on teacher education to transfer international knowledge to more traditional sectors, in an attempt to bridge the quality gap in its national (Early Childhood) education system. However, according to many scholars, knowledge transfer is not a straightforward process, as educational settings and knowledge are autopoietic, value-laden and idiosyncratic. At the same time, constructivist and reflective models of teacher education, which claim to foster sustainable knowledge transfer, are becoming increasingly popular. ‘Sustainable transfer’ is defined here as the process by which international knowledge is successfully accommodated within local educational settings. This study investigates the circumstances which may hinder or facilitate the transfer of international knowledge to local developing realities within the framework of constructivist and reflective teacher education, in order to understand the sustainability of this international policy
Applicazione al Credito Cooperativo Italiano
No full textSul tema del rischio negli intermediari e nel sistema bancario in generale e del rischio sistemico nello specifico, questo lavoro non intende innanzitutto proporre un ‘modello’. Piuttosto, attraverso l’analisi critica dei presupposti epistemologici della categoria generale del rischio, si vuole giungere ad un quadro di riferimento per la validazione delle strutture semantiche afferenti le proposizioni sul rischio in generale e nello specifico il rischio sistemico, la sua ‘natura’, gli strumenti di valutazione e le proposte di gestione. Nella letteratura sui network applicati allo studio del sistema bancario e finanziario e con specifico riferimento all’analisi del rischio sistemico, il processo di formazione delle connessioni fra agenti è spesso modellizzato tramite simulazione di un processo stocastico di Poisson. Come sottolineano Amini, Cont e Minca, (2010), “i network bancari presentano strutture molto complesse e soprattutto eterogenee fra di loro, lontani assai dai modelli stilizzati. La concezione per cui importanti caratteristiche di un network finanziario quali sono il grado di connettività e le mutue connessioni via le poste di bilancio seguono un processo aleatorio con distribuzioni uniforme fra gli intermediari è quanto meno poco realistico”. In altri termini, manca la prospettiva dell’intenzionalità presente nell’agire strategico delle banche. Nell’ambito dei network che nascono e evolvono dall’interazione strategica fra i nodi, il presente lavoro intende proporre un altro criterio per spiegare il perché del formarsi delle connessioni fra nodi. L’ipotesi centrale che si vuole sostenere è che alcuni network si formano come risposta ex-ante alle situazioni di incertezza che si determineranno nel futuro e dalle quali potranno sorgere rischi per i singoli nodi e per l’insieme della rete che si sarà formata. Inoltre, si ipotizza che questa ragione per la formazione dei network sia particolarmente significativa per le imprese cooperative dove giuoca un ruolo fondamentale il principio della mutualità. In questa prospettiva, l’obiettivo dei singoli nodi nell’interagire con gli altri non è più la massimizzazione del profitto, ma il mantenere un insieme di condizioni che consentano la propria sopravvivenza nella rete formatasi. In condizioni di incertezza, il principio di mutualità garantisce l’impegno di tutti nei confronti di ognuno per minimizzare i rischi. Ma affinché il principio di mutualità dispieghi tutto il suo potenziale, si deve realizzare la condizione per cui la densità di connessioni fra i soggetti mutualistici sia maggiore della densità di connessioni nei confronti dei soggetti non mutualistici. Il rischio sistemico non è più solo funzione della densità delle relazioni nel network e della posizione relativa del singolo nodo. Esso è anche e soprattutto funzione del grado d’incertezza che si determina nei mercati dove operano i soggetti.La ricerca qui intrapresa delinea un fattore di congiunzione essenziale fra l’analisi del rischio sistemico e la NWT applicata al rischio sistemico. Tale fattore è individuato nell’incertezza. Per il punto in cui sono arrivati sia gli studi sul rischio sistemico, sia gli studi della NWT applicati al rischio sistemico , le cooperative di credito diventano un banco di verifica interessante
POTENZIALITA' DELLA MICROCOGENERAZIONE E PROGETTAZIONE DI UN MICROCOGENERATORE A CICLO STIRLING
No full textMICROCHP ANALYSIS, DEVELOPMENT AND TESTING OF A MICROCHP STIRLING ENGINE OF 1 KW POWER. ANALISI DEL POTENZIALE DELLA MICROCOGENERAZIONE IN AMBITO CIVILE E DOMESTICO, E PROGETTAZIONE E REALIZZAZIONE DI UN MICROCOGENERATORE A CICLO STIRLING DA 1 KW ELETTRICO
Novel Classes of Porphyrazine Macrocycles: Effect of -Delocalization, Exocyclic Coordination and Quaternization Processes
No full textThe pyrazinoporphyrazine macrocycles having formula [Py8TPyzPzH2], (Figure 1B) and its metal complexes [Py8TPyzPzM], with M = bivalent first transition series and non transition series metal ions, were extensively investigated by our group [1]. Structural and electronic features were studied by single crystal X-ray work, spectral (IR, UV-visible, NMR) and electrochemical investigations, and contributed by detailed theoretical DFT and TDDFT studies. The important role of the external pyridine rings has been examined by considering their capability of electronic contact with the central pyrazinoporphyrazine core. Their ability to coordinate metal centers [2] or to undergo quaternization processes at the N atoms [1b,c] has also been studied. The attention for applicative aspects has been particularly devoted to learn about their behavior as photosensitizers in PDT and their potentialities as multimodal anticancer agents [3, 2b-d].
The present thesis work has selected as the main subject the synthesis of two novel types of porphyrazine macrocycles, strictly related to the above considered “pyrazinoporphyrazines”, but showing a narrower (“restricted” macrocycle) or more extended porphyrazine core (“expanded” macrocycle”). The two compounds, in the form of unmetalated species are schematically shown in Figures 1A and 1C respectively. The targets of the present project were to explain: a) how the change in the expansion or contraction of the central planar or quasi-planar -conjugated skeleton, with respect to that of the pyrazinoporphyrazine core, will modify stability, solubility, tendency to aggregation, general physicochemical and redox behaviour of the new species and their applicative potentialities, with attention centered on their photoactivity properties; b) how the presence of the external pyridine rings, directly attached to the porphyrazine core (“restricted” macrocycle; Figure 1A) or more far away than in the already studied “pyrazinoporphyrazine” macrocycle (“expanded” macrocycle; Figure 1C) added of local metal coordination or quaternization processes, can produce consistent effects on the structural and electronic features of the new macrocyclic skeletons; c) how do the data concerning the response of the new species as photosensitizers compare with those already known for the original “pyrazinoporphyrazine” macrocycles.
UV-visible spectral data in the low-donor nonaqueous solvents indicate that there is a progressive highly remarkable bathochromic shift of the barycentre of the overall spectrum in the direction pyridylporphyrazines pyrazinoporphyrazines quinoxalinoporphyrazines, in line with the parallel enhanced extension of the -conjugated system of the macrocycles in the order given.
The eight external pyridines allow the accomplishment of exocyclic coordination and formation of pentanuclear species carrying externally PdCl2 and PtCl2. Figure 2 shows the pentametallic species for the pyridyl- (A) and quinoxalinoporphyrazines (B). Data at hand indicate that coordination of the PdII or PtII units takes place in all cases at the pyridine N atoms, and sites of the type N2(pyr)MCl2 (M = PdII, PtII; “py-py” coordination) are generated, displaying a square planar geometry and directed nearly perpendicularly to the plane of the central -conjugated macrocyclic system. External ligation modifies the UV-visible spectrum of the initial mononuclear species, the effect evidencing a bathochromic shift of the original main Q band by an average value of 15-20 nm. This remarkable shift is surprising if account is taken that exocyclic coordination of PdII and PtII, particularly for the pyrazino- and even more for the quinoxalinoporphyrazine compounds, takes place at the extreme periphery of the macrocycle and progressively more far away from the central metal.
Further extension of the work focused on the synthesis of supercharged macrocycles for the pyridyl- and quinoxalinoporphyrazines. The new octacationic compounds which are moderately water soluble, were prepared from the mononuclear species upon reaction with CH3I, a process which results in the full N-methylation of the pyridine rings (Figure 3).
The UV-visible spectra in water solution and in the low-donor solvents pyridine, DMSO and DMF show interesting effects which parallel those determined by the external metalation. The spectra evidence in the process from neutral to octacationic species a bathochromic shift of the Q bands about of the same order observed for the change mononuclear pentanuclear species. This means that the charged macrocycles enhance their electron deficiency; a fact that should be confirmed by the electrochemical behaviour in terms of the expected less negative half-wave potentials with respect to those pertinent to the neutral mononuclear species.
The final challenge of some of the pyridyl- and quinoxalinoporphyrazines, especially those carrying centrally ZnII and MgII (closed shell metal ions) is their measured photoactivity for the generation in DMF of singlet oxygen, 1O2, the cytotoxic agent in the photodynamic therapy of cancer (PDT). The quantum yields of 1O2 measured, particularly for the two pyridylporphyazines having centrally ZnII and MgII, qualify these compounds as excellent photosensitizers. A combination of purity of the samples, water solubility, stability under the appropriate irradiation (600-750 nm), absence of aggregation in solution may be profitable for application in the PDT curative modality. The species carrying outside PtCl2 units may open perspectives for applications as bimodal PDT/cis-platin anticancer agents.
Concomitant work was conducted on “pyrazinoporphyrazine” macrocycles carrying externally thienyl rings (Figure 4). The work on the thienyl pyrazinoporphyrazines involved modifications of the peripheral part of the macrocycle, focusing on the coordination properties of the S atoms inserted in the external 2-thienyl rings, in an interesting comparison with those seen for the pyridine rings in the pyridinated “pyrazinoporphyrazines” [4]. On the other hand the singlet oxygen and fluorescence response of the mono- and pentametallic complexes open perspectives for their potential use in PDT of cancer and for medical imaging and diagnosis.
References:
[1] a) Donzello, M. P.; Ou, Z.; Monacelli, F.; Ricciardi, G.; Rizzoli, C.; Ercolani, C.; Kadish, K. M. Inorg. Chem. 2004, 43, 8626; b) Donzello, M. P.; Ou, Z.; Dini, D.; Meneghetti, M.; Ercolani, C.; Kadish, K. M. Inorg. Chem., 2004, 43, 8637; c) Bergami, C.; Donzello, M. P.; Ercolani, C.; Monacelli, F.; Kadish, K. M.; Rizzoli, C. Inorg. Chem., 2005, 44, 9852; d) Bergami, C.; Donzello M. P.; Monacelli, F.; Ercolani, C.; Kadish, K. M. Inorg. Chem., 2005, 44, 9862.
[2] a) Donzello, M. P.; Viola, E.; Cai, X.; Mannina, L.; Rizzoli, C.; Ricciardi, G.; Ercolani, C.; Kadish, K. M.; Rosa, A. Inorg. Chem., 2008, 47, 3903; b) Donzello, M. P.; Viola, E.; Cai, X.; Mannina, L.; Ercolani, C.; Kadish, K. M. Inorg. Chem., 2010, 49, 2447; c) Donzello, M. P.; Viola, E.; Mannina, L.; Barteri, M.; Fu, Z.; Ercolani, C. J. Porphyrins Phthalocyanines, 2011, 15, 984; d) Donzello, M. P.; Vittori, D.; Viola, E.; Manet, I.; Mannina , L.; Cellai, L.; Monti, S.; Ercolani, C. Inorg. Chem., 2011, 50, 7391.
[3] Donzello, M. P.; Viola, E.; Bergami, C.; Dini, D.; Ercolani, C.; Giustini, M.; Kadish, K. M.; Meneghetti, M.; Monacelli, F.; Rosa, A.; Ricciardi, G. Inorg. Chem., 2008, 47, 8757.
[4] a) De Mori, G.; Fu, Z.; Viola, E.; Cai, X.; Ercolani, C.; Donzello, M. P.; Kadish, K. M. Inorg. Chem., 2011, 50, 8225; b) Donzello, M.P.; De Mori, G.; Viola, E.; Ercolani, C.; Bodo, E.; Mannina, L.; Capitani, D.; Rizzoli, C.; Gontrani, L.; Aquilanti, G.; Kadish, K. M.; D’Angelo, P. Inorg. Chem., 2011, 50, 12116