Control of Multilayer Networks

The controllability of a network is a theoretical problem of relevance in a variety of contexts ranging from financial markets to the brain. Until now, network controllability has been characterized only on isolated networks, while the vast majority of complex systems are formed by multilayer networks. Here we build a theoretical framework for the linear controllability of multilayer networks by mapping the problem into a combinatorial matching problem. We found that correlating the external signals in the different layers can significantly reduce the multiplex network robustness to node removal, as it can be seen in conjunction with a hybrid phase transition occurring in interacting Poisson networks. Moreover we observe that multilayer networks can stabilize the fully controllable multiplex network configuration that can be stable also when the full controllability of the single network is not stable

Nuovi approcci per lo studio non invasivo della cinetica enzimatica e biochimica in vivo mediante tecniche spettroscopiche di risonanza magnetica basate sull'impiego dell'iperpolarizzazione dinamica nucleare di substrati isotopicamente arricchiti con [13C]-carbonio.

Nell’ambito di questo lavoro di tesi è state valutato l’impiego di [1-13C] piruvato e [1-13C] iperpolarizzati e la spettroscopia di risonanza magnetica per lo studio non invasivo del metabolismo cardiaco in un modello porcino. Al fine di garantire un adeguato rapporto segnale rumore ed una sufficiente sensibilità della metodica sono stati messi a punto ed ottimizzati i parametri chimico fisici del processo di iperpolarizzazione e le metodiche di acquisizione del segnale spettroscopico impiegando uno scanner clinico a 3T ed un sistema di iperpolarizzazione dinamica nucleare. La somministrazione sistemica di acetato e piruvato arricchiti con [13C] iperpolarizzati si è dimostrata sicura, in termini di induzione di effetti farmacodinamici, ed ha consentito la valutazione dinamica del metabolismo cardiaco in vivo in modo non invasivo nel maiale da esperimento. E’ stato misurata la conversione enzimatica dei substrati iniettati nei sottoprodotti; sono state fornite le mappe 3D di distribuzione spaziale cardiache e le curve dinamiche di conversione per le regioni cardiache. In particolare, è stata fornita una stima semi-quantitativa delle costanti cinetiche di conversione del substrato nei vari metaboliti. I metodi di analisi metabolica sono stati applicati in un modello di stress inotropo nel maiale, evidenziando una buona correlazione tra la le stima delle costanti apparenti di conversione e lo stato fisiologico del miocardio. La mappatura metabolica della distribuzione spaziale dei metaboliti identificati globalmente nel cuore di maiale è stata effettuata mediante studi di Chemical Shift Imaging con [1-13C]piruvato o [1-13C]acetato: sono state prodotte mappe di distribuzione spaziale del segnale spettroscopico dei metaboliti prodotti nel miocardio sano e in un modello d ischemia transitoria. Con questo approccio, è stata dimostrata la capacità di studiare in un modello di ricerca pre-clinica traslazionale la potenzialità della tecnica di spettroscopia di substrati iperpolarizzati, per la valutazione non invasiva della cinetica enzimatica e biochimica in vivo. I protocolli sperimentali e le metodologie messe a punto durante il percorso di specializzazione rappresentare un punto di partenza per l'applicazione di questa tecnologia, non solo nella diagnostica ad immagini cardiologica, ma anche per la caratterizzazione di modelli fisiopatologici in altri ambiti, come la valutazione metabolica del microambiante tumorale, e lo studio delle proprietà farmacologiche di nuovi composti che agiscano su uno specifico pathway enzimatico

Distinct modes of neuritic growth in purkinje neurons at different developmental stages: axonal morphogenesis and cellular regulatory mechanisms.

BACKGROUND: During development, neurons modify their axon growth mode switching from an elongating phase, in which the main axon stem reaches the target territory through growth cone-driven extension, to an arborising phase, when the terminal arbour is formed to establish synaptic connections. To investigate the relative contribution of cell-autonomous factors and environmental signals in the control of these distinct axon growth patterns, we examined the neuritogenesis of Purkinje neurons in cerebellar cultures prepared at elongating (embryonic day 17) or arborising (postnatal day zero) stages of Purkinje axon maturation. METHODOLOGY/PRINCIPAL FINDINGS: When placed in vitro, Purkinje cells of both ages undergo an initial phase of neurite elongation followed by the development of terminal ramifications. Nevertheless, elongation of the main axon stem prevails in embryonic Purkinje axons, and many of these neurons are totally unable to form terminal branches. On the contrary, all postnatal neurites switch to arbour growth within a few days in culture and spread extensive terminal trees. Regardless of their elongating or arborising pattern, defined growth features (e.g. growth rate and tree extension) of embryonic Purkinje axons remain distinct from those of postnatal neurites. Thus, Purkinje neurons of different ages are endowed with intrinsic stage-specific competence for neuritic growth. Such competence, however, can be modified by environmental cues. Indeed, while exposure to the postnatal environment stimulates the growth of embryonic axons without modifying their phenotype, contact-mediated signals derived from granule cells specifically induce arborising growth and modulate the dynamics of neuritic elongation. CONCLUSIONS/SIGNIFICANCE: Cultured Purkinje cells recapitulate an intrinsically coded neuritogenic program, involving initial navigation of the axon towards the target field and subsequent expansion of the terminal arborisation. The execution of this program is regulated by environmental signals that modify the growth competence of Purkinje cells, so to adapt their endogenous properties to the different phases of neuritic morphogenesis

Influenza della velocità di deformazionenel carico di rottura di moschettoni in lega di alluminio e di acciaio

Si analizzano i dati sulla deformabilità, sul lavoro alla rottura e sulla resistenza ottenuti con prove di caduta a velocità di deformazione variabile (Torre CRASC) su moschettoni in lega di alluminio e in acciaio, evidenziando come all’aumentare della velocità di deformazione le caratteristiche di resistenza diminuiscano marcatamente. Queste variazioni vengono messe in relazione ai diversi intervalli dei valori della velocità di deformazione propri della progressione speleologica, torrentistica, alpinistica e ad alte velocità di deformazione (vie ferrate).We analyze data on the deformability, the work on resistance to breakage and obtained evidence of a fall in variable strain rate (Torre CRASC) on snap aluminum alloy and steel, noting that with increasing strain rate characteristics resistance decreases markedly. These changes are made in relation to the different ranges of values of strain rate of its progression caving, canyoning, mountaineering, high strain rate (via ferrata)

Distinct modes of neuritic growth in Purkinje neurons at different developmental stages: axonal morphogenesis and cellular regulatory mechanisms

BACKGROUND: During development, neurons modify their axon growth mode switching from an elongating phase, in which the main axon stem reaches the target territory through growth cone-driven extension, to an arborising phase, when the terminal arbour is formed to establish synaptic connections. To investigate the relative contribution of cell-autonomous factors and environmental signals in the control of these distinct axon growth patterns, we examined the neuritogenesis of Purkinje neurons in cerebellar cultures prepared at elongating (embryonic day 17) or arborising (postnatal day zero) stages of Purkinje axon maturation. METHODOLOGY/PRINCIPAL FINDINGS: When placed in vitro, Purkinje cells of both ages undergo an initial phase of neurite elongation followed by the development of terminal ramifications. Nevertheless, elongation of the main axon stem prevails in embryonic Purkinje axons, and many of these neurons are totally unable to form terminal branches. On the contrary, all postnatal neurites switch to arbour growth within a few days in culture and spread extensive terminal trees. Regardless of their elongating or arborising pattern, defined growth features (e.g. growth rate and tree extension) of embryonic Purkinje axons remain distinct from those of postnatal neurites. Thus, Purkinje neurons of different ages are endowed with intrinsic stage-specific competence for neuritic growth. Such competence, however, can be modified by environmental cues. Indeed, while exposure to the postnatal environment stimulates the growth of embryonic axons without modifying their phenotype, contact-mediated signals derived from granule cells specifically induce arborising growth and modulate the dynamics of neuritic elongation. CONCLUSIONS/SIGNIFICANCE: Cultured Purkinje cells recapitulate an intrinsically coded neuritogenic program, involving initial navigation of the axon towards the target field and subsequent expansion of the terminal arborisation. The execution of this program is regulated by environmental signals that modify the growth competence of Purkinje cells, so to adapt their endogenous properties to the different phases of neuritic morphogenesis

A Novel Approach for Determining the Electromagnetic Properties of a Colloidal Fluid With Magnetic Nanoparticles for Hyperthermia Applications

The paper presents a general analytical method for evaluating the magnetic properties of colloidal fluid with magnetic nanoparticles and agar through in vitro specific absorption rate (SAR) measurements. The approach for the determination of magnetic complex susceptibility herein presented reveals itself as simple, rapid, broadband, and accurate enough to compete with alternative conventional direct methods requiring complex and expensive instrumentation. In particular, it makes use of indirect equations based on the single-order Debye model [linear response theory (LRT)] combined with a punctual set of in vitro SAR measurements. The procedure is effective inside the range of validity of the LRT theory, and it can be easily applied in the up-growing field of magnetic hyperthermia studies