Studio e sviluppo di modelli di connettività effettiva del sistema olfattivo mediante tecnica di Risonanza Magnetica Funzionale

Il lavoro di questa tesi s’inquadra all’interno di una ricerca, svolta presso l’Istituto di Fisiologia Clinica dell’area della ricerca di Pisa, che si pone l’obiettivo di individuare attraverso la Risonanza Magnetica funzionale (fMRI) le regioni cerebrali coinvolte nell’attività olfattiva: in particolare viene affrontato il problema dello studio e dello sviluppo di modelli di connettività effettiva, con l’obiettivo di applicarli ai segnali fMRI delle aree olfattive, cercando di individuare e di risolvere le principali problematiche che si possono incontrare nell’affrontare uno studio di questo tipo. La connettività effettiva tenta di spiegare l’influenza che un sistema neurale esercita, direttamente o no, su un altro, ovvero vuole spiegare il “come” il cervello riesce a portare a termine la comunicazione fra tutte le regioni coinvolte in una certa risposta neurale. Questo tipo di studio non può prescindere da ipotesi fondate circa la presenza di legami anatomici tra le diverse regioni; per questo motivo sono utilizzati metodi d’analisi “hypothesis-driven” tra cui i più diffusi sono lo Structural Equation Modeling (SEM) e il Dynamic Causal Modeling (DCM). L’obiettivo principale è lo studio e la valutazione delle potenzialità del SEM, attraverso simulazioni e test specifici, quindi l’applicazione del modello ai dati sperimentali, l’interpretazione dei risultati e l’indicazione dei possibili sviluppi futuri della ricerca

Surface Fluctuations of an Aging Colloidal Suspension: Evidence for Intermittent Quakes

We present measurements of the thermal fluctuations of the free surface of an aging colloidal suspension, Laponite. The technique consists in measuring the fluctuations of the position of a laser beam that reflects from the free surface. Analysing the data statistics, we show that, as the fluid ages, the dynamics becomes intermittent. The intermittent events correspond to large changes in the local slope of the free surface over a few milliseconds. We show that those quakes are uncorrelated, although they are kept in memory by the surface over short time scales

Analisi dei processi manutentivi in SCA PACKAGING ITALIA

Sommario: La presente tesi è stata svolta nello stabilimento di Porcari (Lucca) della società SCA Packaging Italia S.p.A., facente parte del Gruppo multinazionale SCA. Lo stabilimento di Porcari (Lucca) è costituito da due linee produttive per la produzione di carta a base macero per la realizzazione di cartone ondulato. L’obiettivo di questa tesi è l’ottimizzazione dei processi manutentivi già in atto presso questo impianto, insieme all’analisi e alla successiva organizzazione della manutenzione di un impianto per l’essiccazione degli scarti, accessorio al processo principale, chiamato “Reject Dryer”. Nella prima parte del progetto sono stati analizzati i flussi informativi e di materiali che si generano all’insorgere di un guasto. Oltre a questo si è cercato di comprendere con quali strumenti l’azienda controlla l’efficacia e l’efficienza di questi flussi ed infine sono state adottate alcune procedure per l’ottimizzazione degli interventi di manutenzione. Nella seconda fase è stato analizzato l’impianto per l’essiccazione degli scarti. Tramite questa analisi è stata organizzata una strategia manutentiva e studiata una serie di indicatori di performance (KPI) per verificarne l’efficacia d’impiego. Abstract: This thesis is the result of work carried out at the SCA Packaging Italia S.p.A. factory site in Porcari (Lucca) - part of the SCA Group. The plant is consists of two lines for the production of paper based on recycled fibre utilised in manufacturing corrugated packaging. The stated object of the work was the improvement of the maintenance processes already present on the plant, together with an analysis and organization of the maintenance of an accessory plant for drying the waste, called “Reject Dryer”. The first phase of the project analyses material and data flows generated as and when a failure occurs. In addition an attempt to understand how the company monitors the effectiveness and efficiency of these flows, and following this certain procedures were adopted to optimise maintenance. The second phase comprises an in depth study of the plant for drying waste. As a result of this analysis a maintenance strategy was proposed together with a study of the relevant performance indicators (KPI) to check the effectiveness of its implementation

Preparation and Analysis of PCL Spun Chitosan Scaffolds as Guidance Channels for Peripheral Nerve Regeneration

The results of this work show that the process of oriented solidification and lyophilisation is able to produce porous chitosan scaffolds with appropriate porosity and pore size for nerve regeneration. Interesting in this context are the results of statistical analysis of image analysis from SEM micrographs of uncrosslinked and UV cross-linked samples. The average pore size and mean minimum pore diameter show only small differences if the cooling rate is varied from B = 1…5 K / min and the temperature gradient from G = 1, 1.5, 2.0 K / mm. The average pore size (cross sectional area) of these samples can be estimated with reasonable accuracy, with 2100 μm². The average minimum pore diameter is within the range of 36-38 μm. These values are in a favourable range for the cell growth of nerve regeneration

Soliton ratchets

The mechanism underlying the soliton ratchet, both in absence and in presence of noise, is investigated. We show the existence of an asymmetric internal mode on the soliton profile which couples, trough the damping in the system, to the soliton translational mode. Effective soliton transport is achieved when the internal mode and the external force are phase locked. We use as working model a generalized double sine-Gordon equation. The phenomenon is expected to be valid for generic soliton systems.Comment: 4 pages, 4 figure

DNA transport by a micromachined Brownian ratchet device

We have micromachined a silicon-chip device that transports DNA with a Brownian ratchet that rectifies the Brownian motion of microscopic particles. Transport properties for a DNA 50mer agree with theoretical predictions, and the DNA diffusion constant agrees with previous experiments. This type of micromachine could provide a generic pump or separation component for DNA or other charged species as part of a microscale lab-on-a-chip. A device with reduced feature size could produce a size-based separation of DNA molecules, with applications including the detection of single nucleotide polymorphisms.Comment: Latex: 8 pages, 4 figure

Downstream processing of high chain length polysialic acid using membrane adsorbers and clay minerals for application in tissue engineering

Polysialic acid (polySia) is a carbohydrate polymer of varying chain length. It is a promising scaffold material for tissue engineering. In this work, high chain length polySia was produced by an Escherichia coli K1 strain in a 10-L bioreactor in batch and fed-batch mode, respectively. A new downstream process for polySia is presented, based on membrane adsorber technology and use of inorganic anion exchanger. These methods enable the replacement of precipitation steps, such as acetone, cetavlon, and ethanol precipitation of the already established purification process. The purification process was simplified, while process efficiency and product qualities were improved. The overall yield of polySia from a 10-L batch cultivation process was 61% and for 10-L fed-batch cultivation process the yield was 40% with an overall purity of 98%. The endotoxin content was determined to be negligible (14 EU mg-1). The main advantage of this new downstream process is that polySia with high chain length of more than 130 degree of polymerization can be obtained. In fed-batch cultivation, chain lengths up to 160 degree of polymerization were obtained.DFG/FOR/54

In vitro evaluation of cell-seeded chitosan films for peripheral nerve tissue engineering

Natural biomaterials have attracted an increasing interest in the field of tissue-engineered nerve grafts, representing a possible alternative to autologous nerve transplantation. With the prospect of developing a novel entubulation strategy for transected nerves with cell-seeded chitosan films, we examined the biocompatibility of such films in vitro. Different types of rat Schwann cells (SCs)-immortalized, neonatal, and adult-as well as rat bone-marrow-derived mesenchymal stromal cells (BMSCs) were analyzed with regard to their cell metabolic activity, proliferation profiles, and cell morphology after different time points of mono-and cocultures on the chitosan films. Overall the results demonstrate a good cytocompatibility of the chitosan substrate. Both cell types were viable on the biomaterial and showed different metabolic activities and proliferation behavior, indicating cell-type-specific cell-biomaterial interaction. Moreover, the cell types also displayed their typical morphology. In cocultures adult SCs used the BMSCs as a feeder layer and no negative interactions between both cell types were detected. Further, the chitosan films allow neurite outgrowth from dissociated sensory neurons, which is additionally supported on film preseeded with SC-BMSC cocultures. The presented chitosan films therefore demonstrate high potential for their use in tissue-engineered nerve grafts.This work was supported by the European Community's Seventh Framework Programme (FP7-HEALTH-2011) under grant agreement No. 278612. This work was also co-funded by Programa Operacional Regional do Norte (ON.2-O Novo Norte), ao abrigo do Quadro de Referencia Estrategico Nacional (QREN), and atraves do Fundo Europeu de Desenvolvimento Regional (FEDER). The authors gratefully acknowledge the delivery of the chitosan raw material by Altakitin S.A., Portugal, and the fabrication of chitosan films by Medovent GmbH, Germany

Brownian motion exhibiting absolute negative mobility

We consider a single Brownian particle in a spatially symmetric, periodic system far from thermal equilibrium. This setup can be readily realized experimentally. Upon application of an external static force F, the average particle velocity is negative for F>0 and positive for F<0 (absolute negative mobility).Comment: 4 pages, 3 figures, to be published in PR

Disorder Induced Diffusive Transport In Ratchets

The effects of quenched disorder on the overdamped motion of a driven particle on a periodic, asymmetric potential is studied. While for the unperturbed potential the transport is due to a regular drift, the quenched disorder induces a significant additional chaotic ``diffusive'' motion. The spatio-temporal evolution of the statistical ensemble is well described by a Gaussian distribution, implying a chaotic transport in the presence of quenched disorder.Comment: 10 pages, 4 EPS figures; submitted to Phys. Rev. Letter