Application of Magnonic Crystals in Magnetic Bead Detection

This paper aims at studying a sensor concept for possible integration in magnetic field-based lab-on-chip devices that exploit ferromagnetic resonance (FMR) phenomena in magnonic crystals. The focus is on 2D magnetic antidot arrays, i.e., magnetic thin films with periodic non-magnetic inclusions (holes), recently proposed as magnetic field sensor elements operating in the gigahertz (GHz) range. The sensing mechanism is here demonstrated for magnetic nano/microbeads adsorbed on the surface of permalloy (Ni80Fe20) antidot arrays with a rhomboid lattice structure and variable hole size. Through extensive micromagnetic modelling analysis, it is shown that the antidot arrays can be used as both bead traps and high-sensitivity detectors, with performance that can be tuned as a function of bead size and magnetic moment. A key parameter for the detection mechanism is the antidot array hole size, which affects the FMR frequency shifts associated with the interaction between the magnetization configuration in the nanostructured film and the bead stray field. Possible applications of the proposed device concept include magnetic immunoassays, using magnetic nano/microbeads as probes for biomarker detection, and biomaterial manipulation

From Micromagnetic to In Silico Modeling of Magnetic Nanodisks for Hyperthermia Applications

Magnetic nanodisks have been recently proposed as biomedical tools for therapeutics at the nanoscale level, with a special focus on hyperthermia for cancer cure. Here we present a detailed study of permalloy nanodisks to be used in alternative to superparamagnetic iron oxide nanoparticles, as efficient heating agents that release heat via magnetic hysteresis. A micromagnetic modeling analysis is carried out to identify sizes and ac field parameters that maximize the specific loss power (SLP), guaranteeing the fulfillment of biophysical constraints (Hergt–Dutz limit) and vortex state at remanence (reduced agglomeration effects). The highest SLP (790 W g−1) is found for 100 nm diameter and 20 nm thickness nanodisks, excited at a frequency of 75 kHz. Further analysis elucidates the influence of magnetostatic interactions and local nanodisk-field orientation on the SLP of nanodisk clusters, which originate from the deposition in target tissues. At high concentrations, magnetostatic interactions can lead to a reduction of 40–50% in the hysteresis losses. From thermal simulations, we finally demonstrate that in a murine model temperature increments comparable to that obtained in calorimetric measurements under quasi-adiabatic conditions can be achieved only by using an order of magnitude larger dosage of nanodisks, due to blood perfusion effects

In silico experiments as a tool to reduce preclinical tests of magnetic hyperthermia

In silico models can be useful tools to guide preclinical tests of magnetic hyperthermia, which employs Magnetic Nanoparticles (MNPs) excited by AC magnetic fields, as heat mediators for cancer cure. We virtually reproduce the heating process induced by magnetic hyperthermia in murine models, as a function of field applicator features, properties and size of target tissue, MNP dose and animal size

Origin and fate of the pseudogap in the doped Hubbard model

We investigate the doped two-dimensional Hubbard model at finite temperature using controlled diagrammatic Monte Carlo calculations allowing for the computation of spectral properties in the infinite-size limit and, crucially, with arbitrary momentum resolution. We show that three distinct regimes are found as a function of doping and interaction strength, corresponding to a weakly correlated metal with properties close to those of the non-interacting system, a correlated metal with strong interaction effects including a reshaping of the Fermi surface, and a pseudogap regime at low doping in which quasiparticle excitations are selectively destroyed near the antinodal regions of momentum space. We study the physical mechanism leading to the pseudogap and show that it forms both at weak coupling when the magnetic correlation length is large and at strong coupling when it is shorter. In both cases, we show that spin-fluctuation theory can be modified in order to account for the behavior of the non-local component of the self-energy. We discuss the fate of the pseudogap as temperature goes to zero and show that, remarkably, this regime extrapolates precisely to the ordered stripe phase found by ground-state methods. This handshake between finite temperature and ground-state results significantly advances the elaboration of a comprehensive picture of the physics of the doped Hubbard model

Proposte per delle politiche pubbliche green e innovative. Riqualificazione energetica del patrimonio edilizio esistente e settore delle costruzioni

La riqualificazione del patrimonio edilizio esistente sia residenziale che produttivo e di servizi rappresenta un nodo fondamentale dell’economia del nostro paese. Da un lato la necessità di ridurre l’impatto sull’ambiente del costruito e di migliorare la qualità dello spazio, dall’altro quella di sostenere un settore economico importante come quello edile si impongono quali urgenze nel panorama sociale. Tuttavia, le politiche di incentivo e i notevoli sforzi promossi a diversi livelli non sembrano aver risolto questo nodo. Molti ostacoli ancora sui frappongono alla generalizzazione di un processo di recupero dei centri urbani. La non completa efficacia delle incentivazioni, il permanere di un’asimmetria informativa tra domanda e offerta, la scarsa strutturazione organizzativa delle imprese del settore appaiono alcuni tra i punti irrisolti in un settore, quale l’edilizia, che conserva tuttora un notevole patrimonio di professionalità. La difficoltà di comunicazione tra soggetti e di strutturazione del processo (filiera) sono il tema da affrontare e don essi la formazione, la qualità e le regole del processo di mantenimento e uso razionale del patrimonio edilizio. Tale fenomeno deve essere, a nostro avviso, esaminato con attenzione alle realtà territoriali di riferimento e alle specificità del settore che unisce elementi di innovazione rilevanti con la necessità di sviluppare economie e processi con una scala territoriale e locale rilevante, si pensi ai temi dell’uso e consumo di territorio, del ciclo dei rifiuti, dei consumi energetici, del rapporto con filiere produttive locali quali quelle del legno, dei prodotti agricoli, dei materiali edilizi in generale. Il contributo propone un approccio al problema sistemico e basato sull’attivazione di processi che possano mettere in relazione orizzonti economici diversi, quali quelli del risparmio atteso in termini energetici dei committenti e le esigenze degli operatori della manutenzione, riferiti a diversi soggetti del processo ipotizzando anche il ruolo degli operatori pubblici e del sistema del credito. In questo orizzonte la definizione di processi di controllo e gestione della qualità di tutto il processo, dalla progettazione all’esecuzione, dalla produzione di materiali e componenti alla gestione degli impianti, diviene essenziale come essenziale diviene la formazione. L’uso e il mantenimento del patrimonio immobiliare divengono, infine, elementi essenziali anche per le dinamiche economiche cui possono contribuire

Influence of shape, size and magnetostatic interactions on the hyperthermia properties of permalloy nanostructures

We present a detailed study of permalloy (Ni80Fe20) nanostructures with variable shape (disk, cylinder and sphere) for magnetic hyperthermia application, exploiting hysteresis losses for heat release. The study is performed modifying nanostructure aspect ratio and size (up to some hundreds of nanometres), to find the optimal conditions for the maximization of specific heating capabilities. The parameters are also tuned to guarantee negligible magnetic remanence and fulfilment of biophysical limits on applied field amplitude and frequency product, to avoid aggregation phenomena and intolerable resistive heating, respectively. The attention is first focused on disk-shaped nanostructures, with a comparison between micromagnetic simulations and experimental results, obtained on nanodisks still attached on the lithography substrate (2D array form) as well as dispersed in ethanol solution (free-standing). This analysis enables us to investigate the role of magnetostatic interactions between nanodisks and to individuate an optimal concentration for the maximization of heating capabilities. Finally, we study magnetization reversal process and hysteresis properties of nanocylinders (diameter between 150 nm and 600 nm, thickness from 30 nm up to 150 nm) and nanospheres (size between 100 nm and 300 nm), to give instructions on the best combination of geometrical parameters for the design of novel hyperthermia mediators

L'artigianato nella prospettiva della green economy

- Indice #5- Green Economy e settore delle costruzioni #13- Sostenibilità, Green economy ed Eco-industry #17- Tendenze evolutive e direzioni di trasformazione del settore #43- Gli attori e i settori #69- Piccole imprese e artigiani dell'eco-costruzione in Piemonte #161- Conclusioni e indicazioni per le politiche regionali #22

L'aggiornamento dei conti regionali: un'applicazione per il Piemonte

Working paper ; n. 131/2000- Indice #3- Premessa #5- Introduzione #7- La metodologia #9- Le stime #21- Riferimenti bibliografici #3