1,722,046 research outputs found
Study of soft nanoparticles for drugs delivery
No full textL'interesse per i sistemi di "drug-delivery" a base di nanoparticelle (NDDS) è cresciuto nell'ultimo decennio. Lo scopo di questo lavoro è di sviluppare un sistema di nanoimaging multispettrale per studi biomedici. Questo avviene in collaborazione con A.P.E. Research, che progetta e sviluppa strumenti di imaging e caratterizzazione. Questo lavoro fa parte del progetto CATHENA (Cancer Therapy by Nanomedicine "POR FESR FVG PROJECT"). Gli NDDS sono sistemi che permettono di trasportare farmaci specifici in tessuti target. Questo lavoro si focalizza su specifici NDDS quali nanoparticelle a base lipidica (SLNPs). Queste nanoparticelle sono state abbondantemente studiate in soluzione. Il mio lavoro si propone quindi di studiare il comportamento di queste nanoparticelle una volta depositate su diverse superfici. Queste analisi verranno integrate in un futuro progetto per l'identificazione di nanoparticelle all'interno di sezioni di tessuti biologici. Parte di questo lavoro si concentra quindi sullo studio delle SLNPs e del colorante indocyanine green (ICG) utilizzando AFM, spettroscopia Raman e spettroscopia a fluorescenza. Questo studio servirà a comprendere il comportamento delle nanoparticelle e dell'ICG una volta depositati su un substrato specifico. L'obiettivo è quello di identificare una possibile proprietà che consentirà un facile rilevamento in sistemi complessi quali tessuti bilogici.Interest in nanoparticle-based drug delivery systems (NDDS) has grown in the last decade. The aim of this work is to develop a multispectral nanoimaging system for biomedical studies. This is done in collaboration with A.P.E. Research, which designs and develops imaging and characterization tools. This work is part of the CATHENA (Cancer Therapy by Nanomedicine "POR FESR FVG PROJECT") project. NDDS are systems that allow to transport specific drugs in target tissues. This work focuses on specific NDDS: Solid-Lipid Nanoparticles (SLNPs). These nanoparticles have been extensively studied in solution. My work therefore aims to study the behavior of these nanoparticles once deposited. These analyses will be integrated into the future project for the identification of nanoparticles within sections of biological tissues. Part of this work focus on the study of SLNPs and the dye indocyanine green (ICG) using AFM, Raman spectroscopy, and fluorescence spectroscopy. Those data, with also the morphological characterization of the deposited SLNPs, will be the basis for the multispectral nanoimaging system development
Surface impedance measurement of resistive coatings at microwave frequencies
No full textA simple approach to estimate the surface impedance of a thin ink deposition on dielectric substrates is described. The measured sample is transversally accommodated in a waveguide, and the scattering parameters are measured. Then, the surface impedance value is recovered by recurring to an efficient transmission-line approach. Closed-form relations are proposed, which allow removing the dispersive effect of the substrate on the estimated surface impedance. The robustness of the retrieving procedure is analyzed, showing that the one based on the transmission coefficient provides more accurate results than the reflection-based one. The positioning of the sample is also investigated, highlighting that the placement inside the waveguide leads to incorrect estimations of the surface impedance with fictitious high imaginary parts because of the presence of air gaps between the sample and the waveguide walls, which transform the uniform layer to a capacitive resistive frequency selective surface. A modified setup with a uniform resistive ink deposition pressed between the waveguide flanges is therefore adopted. Additional experimental results on the effect of the dielectric substrate and on the homogeneity of the ink deposition are reported
A Frequency Selective Radome With Wideband Absorbing Properties
Full text linkA frequency selective radome is presented, acting as a pass band filter at a given frequency band, while behaving as an absorber above the transmission band. The pass band behavior is obtained by a metallic FSS realized through a compact interdigitated Jerusalem cross element characterized by a very large rejection band. The metallic FSS is used as the ground plane of a thin wideband absorber based on resistive high-impedance surfaces within the total reflection band. The outer absorber reduces the signature of the antenna system when the radome is illuminated by out of band signals. The resistive FSS which comprises the absorber is designed so to minimize losses within the transmitting band of the radome. The composite structure is thoroughly analyzed by an efficient equivalent circuit approach and by full-wave numerical simulations
Design of subwavelength tunable and steer-able Fabry-Perot/leaky wave antennas
No full textThe design of a thin tunable and steerable Fabry-Perot antenna is presented. The subwavelength structure is analyzed both by an efficient transmission line model and by full-wave simulations. The tunable antenna consists of a low profile resonant cavity made up of a Partially Reflecting Surface (PRS) placed in close proximity of a tunable high-impedance surface. The active ground plane is synthesized by loading the high-impedance surface with varactor diodes. Such design allows both tuning the high-gain operational frequency and obtaining a beam steering/shaping for each resonant frequency. The transmission line model here presented includes averaged analytical expressions for modelling the tunable high-impedance surface and the frequency selective surfaces. All the theoretical speculations are verified by full-wave simulations on a finite size structure
Closed-Form Analysis of Reflection Losses in Microstrip Reflectarray Antennas
Full text linkMicrostrip reflectarray antennas consist of a grounded quasi-periodic array of printed elements able to compensate the phase displacement of a non-coherent electromagnetic excitation generated by a feeder. The design of reflectarray antennas is usually accomplished by tracing the reflection phase diagram of the periodic version of the printed surface, which is analogous to a high-impedance surface (HIS). Reflection losses of this periodic structure are here analyzed through a simple equivalent transmission line model. The analytical expressions of the surface impedance offered by a HIS (real and imaginary part) as a function of the imaginary part of the dielectric permittivity of the substrate are derived through well justified approximations. Some useful practical examples are then presented both for verifying the accuracy of the derived closed-form expressions and for studying the effect of the geometrical and electrical parameters of the periodic surface on the reflection losses. The dependence of the input impedance on the capacitance associated with the printed pattern is highlighted, demonstrating that highly capacitive elements (tightly coupled subwavelength elements) are preferable for minimizing reflection losses
Design of Subwavelength Tunable and Steerable Fabry-Perot/Leaky Wave Antennas
Full text linkThe design of a thin tunable and steerable Fabry-Perot antenna is presented. The subwavelength structure is analyzed both by an efficient transmission line model and by full-wave simulations. The tunable antenna consists of a low profile resonant cavity made up of a Partially Reflecting Surface (PRS) placed in close proximity of a tunable high-impedance surface. The active ground plane is synthesized by loading the high-impedance surface with varactor diodes. Such design allows both tuning the high-gain operational frequency and obtaining a beam steering/shaping for each resonant frequency. The transmission line model here presented includes averaged analytical expressions for modelling the tunable high-impedance surface and the partially reflecting surface. All the theoretical speculations are verified by full-wave simulations on a finite size structur
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