1,721,635 research outputs found
NATO’s Social Media Strategic Communication in the Making
No full textThe tenet of this investigation, stemming from Conoscenti (2016 and 2017), is that since 2014 the NATO military have been unable to introduce specific correctives to their social media strategy, particularly on Facebook, thus endangering their role and strategic capabilities. This paper builds on the chance that the author had to attend and lead, as a subject-matter expert, the NATO working groups that are active in this specific communicative environment. This also offered him the opportunity to be a participant observer and to access specific documents of the discourse community under scrutiny. After clarifying the elements that frame the military operations in this field, the current NATO communication on Facebook will be analysed in contrast to its communication in 2014. The paper also aims to document the effort of younger military generations to adapt to this new scenario. To account for this, an analysis of military discourse methodology is used. To achieve this goal a multimodal analysis approach (Conoscenti, 2017; Norris, 2011; Kress, 2010) is blended with netnography (Kozinet, Dolbec and Earley, 2014). Since the NATO Facebook page is a specific case of Computer-Mediated Communication to be analysed with a Discourse Analysis perspective that incorporates content analysis, this can be achieved through an extended paradigm of WebCA (Herring, 2010)
“ISIS’ Dabiq communicative strategies, NATO and Europe. Who is learning from whom?”: Review of an article by Michelangelo Conoscenti
No full textThis article is a review of the work of Michelangelo Conoscenti, professor of the Turin University
(Italy), “ISIS’ Dabiq communicative strategies, NATO and Europe. Who is learning
from whom?” The author of the review analyses M. Conoscenti’s work from the standpoint
of the communicative strategies between such actors of international relations as NATO and
ISIS. The review focuses on the nine sections of M. Conoscenti’s work: introduction; review of
the literature; corpus description and names of the entity; the corpus linguistic analysis; a linguistic
interpretation of Dabiq; deception, in Dabiq and in military doctrine; Dabiq as Armageddon?
A Western isotopy for a Western narrative trajectory; the narrative against Europe;
conclusion. The author of the review pays precise attention to the fact that M. Conoscenti,
exploring the content of eleven issues of the journal, uses the techniques of corpus linguistics
and the theory of meme introduced by Dawkins. M. Conoscenti writes that NATO uses narrative
of fear and military discourse to establish its communication with the world. The review
focuses on M. Conoscenti’s evidence in favor of the failure of NATO’s strategic communication
in comparison with the advanced strategies of Dabiq
Valutazione dell’erosione prodotta dai processi di dilavamento nel bacino del Fiume della Mendola (Sicilia, Italia)
No full textPOLITICHE EUROPEE DELLA PESCA E REALTA’ LOCALI: IMPATTO DEI FONDI EUROPEI SULLA PRODUTTIVITA’ DELLE IMPRESE ITTICHE IN SICILIA E IN GALIZIA
Get PDFPLLA-BASED SCAFFOLDS FOR OSTEOCHONDRAL TISSUE REGENERATION VIA THERMALLY INDUCED PHASE SEPARATION TECHNIQUE
Get PDFL’ingegneria tessutale (TE) è una scienza multidisciplinare che mira a progettare e sviluppare sostituti biologici per migliorare, riparare e/o sostituire i tessuti negli organismi umani. Sulla base della tipica triade dell’ingegneria tessutale è incentrato il primo capitolo Scaffold, Source and Signal; lo scaffold funge da struttura tridimensionale, le cellule rappresentano la source mentre il bioreattore fornisce gli adeguati segnali chimico/fisici. In questo lavoro di tesi sono stati presi in considerazione tutti e tre questi aspetti avendo come obiettivo la rigenerazione osteocondrale.
La guarigione dei difetti osteocondrali, riguardanti le lesioni della cartilagine che si esten- dono fino in profondità nell’osso subcondrale, rimangono tutt’oggi un difficile compito della chirurgia ricostruttiva. Tali difetti sono difficili da trattare perché i due tessuti hanno differenti capacità intrinseche di guarigione e diverse strutture anatomiche. Tra la pletora di strategie nella rigenerazione dei tessuti lo scaffold è sicuramente uno degli elementi costitutivi. Si tratta di una struttura polimerica, biocompatibile e biodegradabile, in grado di replicare la matrice extracellulare (ECM), la cui funzione principale è quella di fornire un supporto temporaneo per il tessuto vivente. Lo scaffold deve imitare nel miglior modo possibile il tessuto da rigenerare, il che implica adeguata resistenza meccanica, biodegradabilità, bio- compatibilità, facilità di sterilizzazione e lavorabilità.
Uno dei metodi più versatili per la produzione di scaffold è probabilmente la Separazione di Fase Indotta Termicamente (TIPS), presentato nel secondo capitolo, mediante la quale è possibile ottenere una struttura porosa con un elevato grado di interconnessione. In letteratura è stato ampiamente dimostrato che mediante opportuni protocolli tempo/temperatura è possibile coprire un ampio range di dimensioni dei pori (da circa 10μm a oltre 200μm) assicurando contemporaneamente notevoli livelli di porosità, rendendo tali strutture idonee alla coltura cellulare.
La TIPS si basa sulla riduzione di energia libera di Gibbs per indurre la smiscelazione di una soluzione polimerica omogenea in un sistema bifasico. Nel momento in cui si verifica la separazione di fase, la soluzione polimerica omogenea si separa in una fase ricca in polimero e una povera in polimero. In funzione della storia termica avvengono meccanismi di separazione differenti: nucleazione e crescita all’interno della regione metastabile (tra curva binodale e curva spinodale) o decomposizione spinodale all’interno della regione instabile (al di sotto della linea spinodale). In funzione del tempo di permanenza all’interno delle varie regioni e/o della velocità di raffreddamento è possibile ottenere diverse morfologie finali dello scaffold.
I parametri operativi più importanti sono: tipologia di polimero, rapporto solvente/non solvente, concentrazione di polimero e storia termica. In particolare mantenendo constanti tutti gli altri parametri, variando semplicemente il protocollo tempo/temperatura è possibile ottenere morfologie dello scaffold molto diverse tra loro. Tra tutti i possibili polimeri biocom- patibili, la famiglia dei poli(a-idrossiacidi), approvati dalla Food and Drug Administration (FDA) degli Stati Uniti per applicazioni cliniche, è stata ampiamente studiata come materiale per la reallizzazione di scaffold. In particolare all’interno di tale famiglia l’acido poli-L-lattico (PLLA) ha attirato notevole interesse grazie alle sue buone proprietà meccaniche, facilità di lavorazione e velocità di degradazione controllabile.
Come evidenziato precedentemente, lo scaffold deve possedere un’elevata porosità e inter- connettività, ma sebbene la sola presenza dei pori sia sufficiente per la ricrescita delle cellule è tuttavia possibile incrementare significativamente la qualità della rigenerazione ponendo l’attenzione sulla distribuzione di dimensione dei pori. Ogni organo o tessuto non è solo contraddistinto dalle diverse tipologie di cellule che lo compongono, ma anche e soprattutto dal modo in cui queste cellule e la matrice che le circonda sono organizzate nello spazio, cosa che determina le caratteristiche globali e il funzionamento dell’organo. Esempi in tal senso sono: le ossa, dal tessuto osseo compatto al tessuto osseo spugnoso; i vasi sanguigni, tunica intima, media e avventizia, ecc.
Al fine di ottenere uno scaffold che presenti un gradiente di dimensione dei pori è stato realizzato e testata una strumentazione sperimentale in grado di imporre una data storia termica ai due lati del campione in modo indipendente. La peculiarità di tale strumentazione, presentata nel capitolo 3, è la possibilità di controllare contemporaneamente la temperatura e la velocità di raffreddamento.
I polimeri da soli non possiedono le proprietà adeguate di bioattività, osteoconduttività e capacità di integrazione nei tessuti, un modo per superare tali limitazioni è la produzione di scaffold compositi polimero/ceramico. L’idea è quella di combinare la processabilità del polimero con le buone proprietà chimico/fisiche del riempitivo ceramico. Scaffold compositi PLLA/idrossiapatite (HA) e PLLA/bioglass(BG) sono presentati nel capitolo 4. Gli scaffold sono stati caratterizzati in termini di porosità (picnometro), struttura molecolare (XRD), morfologia (SEM), contenuto di riempitivo (TGA), e struttura chimica (FT-IR).
Affinché un determinato scaffold possa essere considerato idoneo per l’ingegneria tessutale è necessario valutarne la sua capacità di favorire la coltura cellulare. Il capitolo 5 presenta i risultati delle colture di diversi tipi cellulari in varie tipologie di scaffold.
Per valutare la sola influenza della morfologia dello scaffold sulla crescita e la differenzi- azione dei condrociti, sono stati realizzati scaffold in puro PLLA con due diverse dimensioni dei pori. Allo stesso modo sono stati seminate cellule staminali mesenchimali per verifi- care l’idoneità degli scaffold con gradiente di dimensioni dei pori (da ~70 μm ~200 μm) alla crescita cellulare. D’altro canto sono stati seminati condrociti e osteoblasti in scaffold compositi PLLA/BG e PLLA/HA, rispettivamente, per verificare l’influenza del riempitivo nella struttura 3D in relazione all’adesione, la proliferazione e l’espressione genica cellulare rispetto al puro polimero.
In questo lavoro di tesi sono stati analizzati tutti e tre gli aspetti del tipico protocollo dell’ingegneria dei tessuti. In particolare nel capitolo 6 è stato caratterizzato e testato un bioreattore in grado di replicare in vitro le condizioni microfisiologiche in vivo della giun- zione osteocondrale. Il bioreattore è costituito da una sistema a doppia camera per mantenere separati i mezzi di differenziazione condrogenico e osteogenico. Lo scaffold con gradiente di dimensioni di pori è stato posto all’interno di un inserto estraibile e seminato con cel- lule staminali mesenchimali umane estratte dal midollo osseo (hBMSCs). Lo scaffold è stato posto i pori di dimensioni inferiori nella camera con il mezzo condrogenico (camera superiore), mentre l’estremità con i pori maggiori è stata posta nella camera con il mezzo osteogenico (camera inferiore). Al termine del periodo di coltura sono stati effettuati test di vitalità cellulare, espressione genica e colorazioni istologiche.Tissue engineering (TE) is a multidisciplinary science aiming at designing and developing biological substitutes to improve, repair and/or replace tissues in human organisms. Based on the classical tissue engineering triad presented on the first chapter (Scaffold, Source and Signal), the scaffold acts as 3D template, the cells represent the source while the bioreactor provides the adequate physical/chemical signal. In this thesis work all three aspects were taken into account considering as a target the osteochondral regeneration. The osteochondral defects, regarding cartilage injuries extending deep into the subchon- dral bone, remains a challenging task in reconstructive surgery. They are difficult to treat because the two tissues present very different intrinsic healing capacities and completely different anatomic structures. Among the pletora of strategies in tissue engineering the use of a scaffold is one of the building blocks. It is a polymeric structure, biocompatible and biodegradable, able to replicate the extracellular matrix (ECM), whose major function is to provide a temporary support for tissue structures. The scaffold must mimic as closely as possible the structure of living tissue from a chemical and physical point of view. This implies specific characteristics such as high interconnected porosity, appropriate pore size and distribution (related to the tissue to be regenerated), sufficient initial mechanical strength, biodegradability and biocompatibility, ease of sterilisation and processability.
One of the most versatile methods for the fabrication of tissue engineering scaffolds is the so-called Thermally Induced Phase Separation (TIPS), presented in the second chapter, through which it is possible to obtain a porous structure with a high degree of interconnection. It has been widely reported in literature that via targeted temperature vs. time protocols it is easy to cover a wide range of pore dimensions (from ca. 10 μm to more than 200 μm) ensuring simultaneously remarkable levels of porosity, which makes those structures suitable for cell seeding, migration and colonisation.
TIPS technique is based on changes in Gibbs free energy to induce the demixing of a ho- mogeneous polymer solution into a two-phase system. When phase separation occurs, the homogenous polymer solution separates into a polymer-rich and polymer-lean phase. For polymer-solvent systems, a miscibility gap can be identified in a T vs. composition diagram and, as a function of the separation pathway, various mechanisms take place: nucleation and growth inside the metastable region, between the binodal and the spinodal curve; spinodal decomposition, inside the unstable region (i.e. below the spinodal line). Depending on the residence time inside the metastable region and/or the cooling rate, different morphologies can be obtained.
The most relevant operating parameters include: polymer type, solvent to non solvent ratio, polymer concentration and temperature vs. time history. These parameters are strongly important both in the early separation stages, when the onset of the first clusters takes place, and in the later stages, when the structure of the scaffold skeleton consolidates. It is evident from the aforementioned scenario that a crucial point in scaffold formation via TIPS is the thermal pathway, which allows one to obtain different morphologies by simply modifying the temperature vs. time protocol.
Among the all possible biocompatible polymers, the poly(a-hydroxy acids), approved by Food and Drug Administration (FDA) of USA for clinical applications, have been extensively studied as scaffolding materials for tissue regeneration. In the particular the poly-(L-lactic acid) (PLLA) has attracted most interest thanks to its suitable mechanical properties, low toxicity and predictable biodegradation kinetics. Furthermore the PLLA can be easily pro- cessed, and its mechanical and degradation properties can be tuned as a function of the target application.
As previous mentioned, the scaffold must present a high level of porosity and interconnectiv- ity, but although the presence of pores is sufficient for cell growth inside the 3D structure, it is possible to significantly improve the quality of the regeneration by focusing on the appropriate pore size distribution. Each organ or tissue is characterized not only by a specific cell type but also by a specific spatial organization, for example: bone, from the compact to the sponge bone, blood vessel, three layers (tunica intima, media and adventitia), etc. This structure determines the overall characteristics and resulting behavior of the organ.
For this reasons, obtaining a porosity gradient becomes a crucial point in order to mimic in the best possible way the tissue to regenerate. In order to attain a gradient pore size in the 3D structure, an experimental apparatus able to impose the desired thermal history on two sides of a scaffold in an independent way was designed, set-up and tested. The peculiarity of the experimental apparatus, presented in the chapter 3, is the possibility to control simultaneously temperature(s) and cooling rate. The sample is located between two Peltier cells, controlled by a computer interface, able to apply and control a T vs. time protocol.
Polymers alone do not possess the adequate proprieties of bioactivity, osteoconductivity or tissue integration, and therefore to overcome these limits, composite polymer/ceramic scaffolds are necessary. The rational is to combine the processability of the polymer with good chemical/mechanical properties of the ceramic filler. In the chapter 4 composite scaffold PLLA/hydroxyapatite(HA) and PLLA/bioglass(BG) were presented. The scaffolds were characterized in terms of porosity (pycnometry), molecular structure (XRD), morphology (SEM), filler content (TGA) and chemical structure (FT-IR).
To consider a specific scaffold suitable for tissue engineering purpose, the evaluation of cell proliferation and growth is necessary. Chapter 5 presents the cell culture of different cell strains in diverse substrates.
To evaluate the separate influence of scaffold morphology on chondrocyte growth and differ- entiation, PLLA scaffold with two different average pore dimensions were tested. Similarly, mesenchimal stem cell were cultured in gradient pore scaffold (from ~70 μm to ~200 μm) to assess their suitability. On the other hand chondrocytes and osteoblasts were cultured in PLLA/BG and PLLA/HA scaffolds, respectively, to check the influence of the filler in the 3D structure in relation to cell adhesion, proliferation and gene expression compared to the neat polymeric scaffold.
In this thesis work the three aspects of the typical tissue engineering pathway were considered. In particular, in chapter 6 a bioreactor able to replicate in vitro microphysiological conditions of the osteochondral junction was characterized and tested with the gradient pore size scaffold. The bioreactor consists of a dual chamber system to maintain separate chondrogenic/osteogenic specific differentiation media. A removable insert hosted the scaffold seeded with human bone marrow-derived mesenchymal stem cells (hBMSCs). The insert containing the gradient pore scaffold was positioned with the smaller pore side in the chondrogenic medium chamber (upper chamber) and the larger pore size in the osteogenic medium chamber (lower chamber). At the end of the cell culture period, cell viability, gene expression and histological staining were carried out
Predicting gully occurrence at watershed scale: Comparing topographic indices and multivariate statistical models
Get PDFIn this study, the ability of five topographic indices to predict the gully trajectories observed in two adjacent watersheds located in Sicily (Italy) was evaluated. Two of these indices, named MSPI and MTWI, as far as we know, have never been employed to this aim. They were obtained by multiplying the stream power index (SPI) and the topographic wetness index (TWI), respectively, by the convergence index (CI). The predictive ability of the topographic indices was measured by using both cut-off independent (AUC: area under the receiver operating characteristic curve) and dependent statistics (Cohen's kappa index κ, sensitivity, specificity). These statistics were calculated also for 100 MARS (multivariate adaptive regression splines) and 100 LR (logistic regression) model runs, which used as predictors the topographic variables (i.e. contributing area, slope steepness, plan curvature and convergence index) combined into the five indices. Performance statistics of both topographic indices and statistical models were calculated using 100 random samples of 2 m grid cells, which were extracted only from flow concentration lines. This was done in order to focus the validation process on where gully erosion is more likely to occur. MSPI achieved the best predictive skill (AUC > 0.93; κ > 0.71) among the topographic indices and exhibited similar and better accuracy than local (i.e. trained and validated in the same watershed) and transferred (i.e. trained in one watershed and tested in the other one) LR models, respectively. On the other hand, MSPI performed similarly to transferred MARS runs (AUC > 0.92; κ > 0.71) but slightly worse than local MARS runs (AUC > 0.95; κ > 0.77). Based on the results of this experiment, it can be inferred that (i) including CI helps in detecting hollow areas where gullies are more likely to occur and (ii) MPSI can be a valid alternative to a data driven approach for mapping gully erosion susceptibility in areas where a gully inventory is not available, which is necessary to calibrate statistical models
Capabilities and Limitations of Payment Channel Networks for Blockchain Scalability
Get PDFL'abstract è presente nell'allegato / the abstract is in the attachmen
Landslide susceptibility mapping using precipitation data, Mazandaran Province, north of Iran
No full textPrecipitation is a nonlinear and complex phenomenon and varies in time and space. It is also evident that there is a link between precipitation and shallow landslides, and precipitation is always considered as a landslide-triggering factor. This study aims to investigate the relationship between the characteristics of precipitation and the historical shallow landslides in Mazandaran Province, north of Iran. For this purpose, the spatial variability of rainfall was analyzed using monthly rainfall data collected at 15 synoptic stations distributed over the region between 1981 and 2014. Monthly precipitation and other derived parameters were used, and a hybrid model combining principal component analysis and cluster analysis (CA) was applied to all the precipitation parameters to regionalize the region into well-defined clusters in terms of precipitation and prove that there is a link between precipitation and the occurred slides. Then, the rotated PCs were combined and the precipitation characteristics map was produced. Demonstrating the linkage between the precipitation characteristics and the historical slides, the combined map can be considered as landslide susceptibility map. The accuracy of prediction was tested against a random guess and obtained as 77%. It is also noticeable that only 30% of the surface area of the study region in the landslide susceptibility map covers about 80% of the known landslides. The calculated measure suggests that the developed model well predicted the location of the occurred slides using only precipitation data
Regional variability of terrain index and machine learning model applications for prediction of ephemeral gullies
No full textTerrain, or topographic, index models aggregate morphometric features of a landscape and use them to predict trajectories and initiation points of classical or ephemeral gullies. As an alternative to the index-based models, statistical machine learning approaches have been recently gaining an increased attention for identification of areas of gully susceptibility. Application of index-based or statistical models is normally restricted to the area of study, and regional model transferability is not well understood. In this study, seven terrain index models and two machine learning algorithms were applied to eight watersheds in Kansas and two watersheds in Sicily. The predictive ability of the nine models was measured by using both cut-off independent (area under the receiver operating characteristic curve) and dependent (Cohen's kappa index, sensitivity, specificity) statistics. The performance statistics of both terrain index and statistical models were cross-examined by finding an optimal threshold in one watershed and applying it to other watersheds. In Kansas, the model based on stream order (GORD) was found to perform similar to machine learning approaches, whereas the modified stream power index (MSPI) model overperformed other terrain index models in Sicily. Different landform characteristics in cultivated areas of the High Plains region in Kansas and in the steep hillslopes of Central Sicily caused models to have variable success rate when the indexes from one region were transferred to another region. The results also showed that a well-calibrated terrain index model, especially based on stream grid order, can be viewed as a valid alternative to a data driven approach for ephemeral gully mapping, but transferability of the optimal thresholds can be applied with caution
- …
