Graph Rewriting for Agent Oriented Visual Modeling

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MRI-based radiomic prognostic signature for locally advanced oral cavity squamous cell carcinoma: development, testing and comparison with genomic prognostic signatures

Background. At present, the prognostic prediction in advanced oral cavity squamous cell carcinoma (OCSCC) is based on the tumor-node-metastasis (TNM) staging system, and the most used imaging modality in these patients is magnetic resonance image (MRI). With the aim to improve the prediction, we developed an MRI-based radiomic signature as a prognostic marker for overall survival (OS) in OCSCC patients and compared it with published gene expression signatures for prognosis of OS in head and neck cancer patients, replicated herein on our OCSCC dataset.MethodsFor each patient, 1072 radiomic features were extracted from T1 and T2-weighted MRI (T1w and T2w). Features selection was performed, and an optimal set of five of them was used to fit a Cox proportional hazard regression model for OS. The radiomic signature was developed on a multi-centric locally advanced OCSCC retrospective dataset (n = 123) and validated on a prospective cohort (n = 108).ResultsThe performance of the signature was evaluated in terms of C-index (0.68 (IQR 0.66-0.70)), hazard ratio (HR 2.64 (95% CI 1.62-4.31)), and high/low risk group stratification (log-rank p < 0.001, Kaplan-Meier curves). When tested on a multi-centric prospective cohort (n = 108), the signature had a C-index of 0.62 (IQR 0.58-0.64) and outperformed the clinical and pathologic TNM stage and six out of seven gene expression prognostic signatures. In addition, the significant difference of the radiomic signature between stages III and IVa/b in patients receiving surgery suggests a potential association of MRI features with the pathologic stage.ConclusionsOverall, the present study suggests that MRI signatures, containing non-invasive and cost-effective remarkable information, could be exploited as prognostic tools

Novel materials and geometries for plasmonic crystal based sensors

The research activity of this thesis is focused on the fabrication of plasmonic nanostructure supports and on the synthesis of hybrid organic/inorganic materials. The aim of this work is to couple a sensitive hybrid material with plasmonic nanostructures, that by amplifying the signal allow to obtain an increase of the sensitivity. Two different research areas (physical and chemical) have been involved. Apparently they are separate, but actually they are functional to each other. In particular, the physical aspect of the work involves surface-plasmon-polaritons (SPPs), that are collective electromagnetic excitations of free surface electrons induced by light propagating along the interface shared dielectric medium . SPPs are extremely sensitive to the refractive index of adjacent dielectric to metallic medium. The sensitivity of SPPs is caused by the confinement of polaritons, due to the opposite sign of metallic-dielectric permittivity constant. In this field, the phenomenon associated to the SPPs and the fabrication (Electron Beam Litography -EBL , Focused Ion Beam -FIB, UV Lithography -UVL, Interferential Lithography -IL, Nanoimprinting Lithography -NIL ) and metal deposition techniques for the preparation of metallic nanostructures have been studied in depth. The morphological and optical characterization of plasmonic crystals has been performed by scanning electron microscope (SEM), atomic force microscope (AFM) and spectroscopic ellipsometry. The other aspect of the research concerns the synthesis and characterization of hybrid organic inorganic materials prepared by sol–gel techniques. Bridged polysilsesquioxane (BPS) compounds are employed to control porosity dimension through the variation of the length and rigidity of the organic bridge. The porosity is necessary because it allows the access of fluid or gas in the material that interact with the organic species present in the film or with active molecules intentionally introduced in the hybrid film or the film structure during synthesis. In the first case, the organic bridges have the double finality of producing the porous structure and to constitute the sensitive specie. Porous structure influences the answer time and the selectivity of sensors because the pore dimension influences the permeability of chemical compound. Hybrid films are characterized by Fourier infrared spectroscopy (FTIR), differential (DTA) and thermo-gravimetric (TGA) analysis and ellipsometric spectroscopy. In order to optimize the plasmonic effect, resist material has been produced. The possibility to have the same dielectric constant on the top and on the bottom of the metallic film enables the excitation of long range surface plasmon (LRSPP), whose wave is more sensitive to the dielectric variations. In this work, an innovative way of controlling film porosity coupled with plasmonic crystal lead to a sensitivity improvement in the detection of xylene vapours.Il lavoro svolto durante la tesi si è concentrato principalmente sulla fabbricazione di supporti plasmonici nanostrutturati e sulla sintesi di materiali ibridi oraginico/inorganici. Lo scopo finale del lavoro è l’accoppiamento di un materiale ibrido, di per se sensibile, con strutture amplificatrici del segnale, come le strutture plasmoniche, al fine di ottenere un aumento della sensibilità. Sono stati quindi presi in considerazione due ambiti di ricerca (un fisico e uno chimico) apparentemente separati, ma in realtà funzionali l’uno all’altro. In particolare, i plasmoni di superficie (SPPs) sono oscillazioni elettromagnetiche di elettroni localizzati all’interfaccia fra un metallo e un dielettrico. Per questa localizzazione del campo elettromagnetico, i plasmoni sono estremamente sensibili a variazioni di indice di rifrazione o di spessore del dielettrico posto sulla superficie metallica. In quest’ambito, si è approfondito lo studio dei fenomeni associati ai plasmoni di superficie e l’uso di diverse tecniche litografiche (Electron Beam Litography -EBL- , Focused Ion Beam –FIB- ,UV Lithography, Interferential Lithography -IL, Nanoimprinting Lithography-NIL), di deposizione di metalli (crescite elettrolitiche e evaporazione) necessarie alla realizzazione di nanostrutture metalliche. I cristalli plasmonici così ottenuti sono stati caratterizzati sia morfologicamente, con osservazioni al microscopio elettronico a scansione (SEM) e a forza atomica (AFM), sia otticamente, con misure ellissometriche. Per quanto riguarda l’altro ambito di ricerca, si è considerato la sintesi e caratterizzazione di matrici ibride, tramite la tecnica sol-gel, a partire da precursori detti bridged polysilsesquioxanes (BPS), che permettono la realizzazioni di materiali a porosità controllata consentendo a fluidi di potersi introdurre nei pori. In questo lavoro, la matrice sensibile è stata ottenuta introducendo molecole attive al suo interno o utilizzando precursori di per sé sensibili in grado di reagire con un analita. Una struttura a porosità controllata influenza sia i tempi di risposta sia la selettività dei sensori poiché la variazione della dimensione dei pori gioca un ruolo nella permeabilità delle specie chimiche. Le matrici utilizzate sono state quindi ampiamente studiate e caratterizzate attraverso analisi di spettroscopia infrarossa a trasformata di Fourier (FTIR), analisi termica differenziale (DTA), termo-gravimetrica (TG) ed ellissometriche. Per avere una maggiore flessibilità nella realizzazione di strutture plasmoniche e per poter ottimizzare l’effetto plasmonico si sono cominciati a sviluppare materiali che possono comportarsi come resist, ad es. materiali sensibili alla radiazione UV. Infatti, l’accoppiamento di due dielettrici che abbiamo le stesse costanti dielettriche in un sandwich con un film metallico si prospetta essere uno sviluppo futuro di tale lavoro. In particolare, questo lavoro ha permesso di sviluppare innovativi sistemi per ottenere film porosi, di approfondire la microstruttura dei materiali ibridi sintetizzati e la caratterizzazione della loro porosità tramite tecniche non distruttive e di avere un effettivo miglioramento della sensibilità utilizzando substrati plasmonici in particolare nella rilevazione di vapori di xylene

Natively porous films as halide anion fluorescence optical sensors

A halogen-anion fluorescent solid-state sensor based on natively porous films doped with a quinolinium derivative is reported. The sensitive films are prepared with a low temperature sol\u2013gel synthesis starting from bridged silsesquioxane precursors, and 6-methoxyquinolinium moieties are covalently linked to the organic\u2013inorganic hybrid network. This sensor system is reversible and allows selective detection and measurement of halogen anion concentrations in the physiological range by a dynamic quenching effect of the sensitive fluorophore. The quenching constants are unaffected by dye inclusion in the bridged polysilsesquioxane matrix

Sensitivity of plasmonic crystal with active sol-gel thin film

Sol\u2013gel hybrid films based on alkyl bridged polysilsesquioxane and doped with phenol red molecules, were synthesized for sensing purposes. Doped films changes colour from yellow to orange to red when exposed to hydrochloric acid (HCl) both in solution and gas phases. The synthesis was optimized in order to produce porous films after spin coating. The porosity increases reacting surface area and chemical reactivity of the sensing thin film. Porosity, optical and structural characterizations of these films were investigated by transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Spectroscopic Ellipsometry (SE). Variation of optical characteristics upon immersion of the film in the solution was characterized by UV\u2013visible (UV\u2013vis) spectroscopy. Moreover the same porous sensitive hybrid film was deposited on gold sinusoidal grating in order to detect variations of the dielectric film optical constant after HCl solution dip. This variation was revealed by monitoring surface plasmon polariton excitations

Porous inorganic thin films from bridged silsesquioxane sol-gel precursors

International audienceA sol-gel process was exploited to produce porous inorganic thin films from phenyl-bridged silsesquioxanes. The evolution of both structural and optical properties of the starting hybrid so-gel films were monitored, during synthesis and successive thermal curing steps, by Fourier transform infrared (FT-IR) spectroscopy, differential thermal analysis (DTA), thermogravimetric analysis (TGA) and spectroscopic ellipsometry (SE). Involved chemical species, structural and chemical modifications were identified when thermal treatments at increasing temperatures in the range of 60-800 degrees C were applied to the hybrid films. The progressive formation of a crosslinked silica network, template elimination and film densification were observed, resulting in completely inorganic porous thin films of low refractive index. The distinctiveness of this system directly comes from the extremely controlled and uniform dispersion of the porogen at a molecular level, which is intrinsic to the bridged silsesquioxane precursor choice. A quantitative porosity analysis was performed by environmental ellipsometric porosimetry (EEP), studying inorganic film optical and mechanical properties under different relative humidity conditions. A transmission electron microscopy (TEM) in-situ characterization of porosity size and distribution confirms the presence of a spatially structured organization of pores of a few nanometers in diameter

Laser devices based on one- and two-photon pumped semiconductor core-shell quantum dots

Highly luminescent CdSe-ZnS core-shell nanocrystals are utilized as dopants within ZrO2 and HfO2 hybrid sol-gel matrices. The emission properties of these hybrid materials are studied upon one and two-photon excitation by fs laser pulses. Under these optical pumping regimes, low-threshold amplified stimulated emission is observed. Furthermore, the optical gain characteristics of these QD hybrid materials within 1D and 2D distributed feedback laser architectures are explored