2,843 research outputs found
Dyck Paths Enumerated by the Q-bonacci Numbers
No full textWe consider Dyck paths having height at most two with some constraints on the number of consecutive valleys at height one which must be followed by a suitable number of valleys at height zero. We prove that they are enumerated by so-called Q-bonacci numbers (recently introduced by Kirgizov) which generalize the classical q-bonacci numbers in the case where q is a positive rational.In Proceedings GASCom 2024, arXiv:2406.1458
Automatizzazione di un'accurata descrizione delle funzioni di risposta nei sistemi a bassa dimensionalità tramite teoria delle perturbazioni dei sistemi a molti corpi
No full textNella scienza dei materiali, la combinazione di simulazioni teoriche con tecniche High-throughput(HT) sta guadagnando maggiore attenzione, in quanto può accelerare la ricerca e la scoperta di nuovi materiali con le proprietà desiderate. Nell'ultimo decennio, i metodi HT sono stati applicati principalmente alla density functional theory (DFT) con grande successo. Tuttavia, la DFT manca di accuratezza quando si tratta di eccitazioni e spettroscopie, come ad esempio nella previsione delle proprietà delle quasiparticelle (esperimenti ARPES) o degli spettri di assorbimento ed electron energy loss(EELS), dove è necessaria una descrizione accurata degli effetti eccitonici.
In questa tesi vogliamo combinare la potenza dello screening HT con l'accuratezza della many-body-perturbation-theory (MBPT) per studiare le proprietà elettroniche e ottiche di sistemi a bassa dimensionalità. In particolare, adottiamo l'approssimazione GW per studiare la struttura elettronica delle bande, e l'equazione di Bethe-Salpeter per calcolare gli spettri ottici.
La prima parte del lavoro è stata dedicata allo sviluppo di una serie di workflow per eseguire studi di convergenza automatizzati dei principali parametri computazionali che entrano nei calcoli MBPT. Essendo i test di convergenza in MBPT di fondamentale importanza per ottenere risultati significativi, rappresentando anche la parte che richiede più tempo umano nei calcoli GW/BSE, questo passaggio è stato essenziale nello sforzo di unire MBPT con gli schemi HT. I workflow sopra menzionati sono stati prima validati su sistemi ben noti come hBN o TiO2, e poi applicati per studiare gli effetti eccitonici in C3N, un sistema 2D recentemente realizzato.
Il C3N è un semiconduttore a gap indiretto 2D emergente con interessanti proprietà meccaniche, termiche ed elettroniche. In questa tesi abbiamo eseguito una descrizione completa delle proprietà elettroniche e dielettriche di C3N, concentrandoci sulla struttura a bande eccitonica. Come per altri materiali 2D, troviamo una dispersione eccitonica lineare non analitica prossima a q=0, che però mostra una convessità verso il basso legata alla natura indiretta del band gap.
Successivamente, questi workflow sono stati utilizzati per studiare l'accuratezza della Godby-Needs plasmon-pole approximation (GN-PPA) implementata nel codice Yambo sul set GW100, un set di 100 molecole utilizzate per confrontare i principali codici MBPT mediante G0W0. Per tutte le molecole abbiamo calcolato il potenziale di ionizzazione (IP) e l'affinità elettronica (EA) e confrontato i risultati con gli altri codici MBPT con i dati GW100 disponibili. I risultati di questo studio ci hanno permesso di concludere che lo schema GN-PPA supera altre approssimazioni comunemente usate, come il modello Hybertsen-Louie, e fornisce risultati in un accordo ragionevole con implementazione più sofisticate del GW come full-frequency e contour-deformation. Recentemente, il gruppo EPFL-THEOS (Lausanne, CH), guidato dal Prof. Nicola Marzari, ha eseguito una HT computational exfoliation di composti 3D sperimentalmente conosciuti, scoprendo più di 1800 materiali 2D esfoliabili.
La parte finale di questa tesi è dedicata allo studio delle proprietà elettroniche e ottiche di un sottoinsieme di questi sistemi, al fine di identificare possibilmente materiali candidati che possano realizzare la tanto ricercata fase di isolante eccitonico (EI). La fase EI è una fase correlata della materia, proposta più di 50 anni fa da L. Keldysh, W. Kohn, in cui lo stato fondamentale di un sistema, al di sotto di una temperatura critica, è formato da un condensato di eccitoni di Bose. Per fare previsioni sulle possibili instabilità eccitoniche nello stato fondamentale, sono indispensabili una stima molto accurata del band gap elettronico e delle energie di legame eccitoniche, e workflow per automatizzare calcoli MBPT costituiscono uno strumento estremamente efficace per questa ricerca.In materials science, the combination of theoretical simulations with high-throughput (HT) techniques is gaining larger attention, as it can speed up the search and discovery of novel materials expressing desired properties. In the last decade, HT methods have been mostly applied to density functional theory (DFT) demonstrating great success. Nevertheless, DFT lacks of predictive accuracy when dealing with excitations and spectroscopies, as for instance in the prediction of quasiparticle properties (ARPES experiments), or absorption and electron energy loss spectra (EELS) where an accurate description of the excitonic effects is needed.
In this Thesis we want to combine the power of HT screening with the accuracy of many-body perturbation theory (MBPT) to study the electronic and optical properties of low-dimensional systems. In particular, we adopt the GW approximation to study the electronic band structure and the Bethe-Salpeter equation to compute optical spectra.
The first part of the work has been devoted to developing a set of workflows to perform automated convergence studies of the main computational parameters entering in MBPT calculations. Being convergence tests in MBPT of paramount importance to obtain meaningful results, also representing the most human time-consuming part of a GW/BSE calculation, this step has been essential in the effort of joining MBPT with HT schemes. The above mentioned workflow was first validated on well-known systems like hBN or TiO2, and then applied to study excitonic effects in C3N, a recently synthesized 2D system.
Monolayer C3N is an emerging 2D indirect gap semiconductor with interesting mechanical, thermal, and electronic properties. In this thesis we have performed a complete description of C3N electronic and dielectric properties, focusing on the momentum-resolved excitonic band structure. As for other 2D materials, we find a linear non-analytic excitonic dispersion close to q=0, which however shows a downward convexity related to the indirect nature of the band gap.
Next, these workflows were used to study the accuracy of the Godby-Needs plasmon-pole approximation (GN-PPA) implemented in the Yambo code on the GW100 set, a set of 100 molecules used to benchmark the main MBPT codes by means of G0W0 approximation. For all the molecules we computed converged ionization potential (IP) and electron affinity (EA), and compared the results with the other MBPT codes with available GW100 data. The results of this study allowed us to conclude that the GN-PPA scheme outperforms other commonly used approximations such as the Hybertsen-Louie plasmon pole model, and provides results in a reasonable agreement with more sophisticated implementation of GW as the full-frequency and contour deformation methods.
Recently, the EPFL-THEOS (Lausanne, CH) group, led by Prof. Nicola Marzari, performed a HT computational exfoliation of experimentally known 3D compounds, discovering more than 1800 exfoliable layered materials.
The final part of this Thesis is dedicated to the investigation of the electronic and optical properties of a subset of these recently discovered 2D systems, in order to possibly identify candidate materials that can realize the long sought excitonic insulator (EI) phase.The EI phase is a correlated phase of matter, proposed more than 50 years ago by L. Keldysh, W. Kohn, in which the ground state of a system, below a critical temperature, is formed by a Bose condensate of excitons. To make prediction on the possibile excitonic instabilities in the ground state, very accurate estimation of the electronic band gap and excitonic binding energies are indispensable and workflows capable of making automatic calculations based on MBPT constitute an extremely effective tool for this research
Who is the author of the 1876 Stefano manuscript?
No full textFor over one hundred years the Stefano manuscript was a private document in the possession of the Baccich family and descendants. It told a story of the 1875 Stefano shipwreck as narrated by the shipwreck survivor and the founding family patriarch Miho Baccich. In these circumstances the question of authorship of the manuscript was immaterial and did not arise as an issue. However, with the publication of the manuscript the author‟s name, or names, need to be formally attributed to it. It turns out that this is not such a clear-cut matter.
As we shall see, all informed sources attributed the authorship, and the ownership, of the manuscript to Miho Baccich. But the manuscript itself was written by Canon Stjepan Skurla – a priest from Miho‟s hometown of Dubrovnik. The question then arises: should Skurla also be considered as an author of the manuscript, or, even as the sole author (as some would have it)
Fashion Culture: Power In Fashion with Stefano Tonchi and Grazia d'Annunzio
No full textStefano Tonchi, global chief creative officer for L’Officiel Group, and Grazia d’Annunzio, former deputy director of Vogue Italia, discuss the power of military uniforms and their influence on high fashion. Tonchi is co-author of the book "Uniform: Order and Disorder.
Introduzione [a I cartolari del notaio Stefano di Corrado di Lavagna]
No full textSaggio introduttivo all’edizione dei frammenti dei protocolli del notaio Stefano di Corrado di Lavagna nel quale viene fatta l’analisi codicologica dei frammenti e si ricostruisce la biografia del notaio. Vengono inoltre esaminate la tipologia dei documenti, le tecniche redazionali del notaio e l’organizzazione burocratica della Chiesa genovese nella seconda metà del secolo XIII.
Introduction essay to the edition of the fragments of the protocols of the notary Stefano di Corrado of Lavagna in which the analysis of the codex fragments and reconstructs the biography of the notary is made by the author. She also examined the types of documents, the technical drafting of the notary and the bureaucratic organization of the Church of Genoa in the second half of the thirteenth century
From Lausanne to Luxembourg: the CJEU’s Seraing Judgment and the Boundaries of Sports Arbitration Under EU Law
No full textIn this expert analysis, Professor Stefano Bastianon dissects the CJEU’s landmark Seraing ruling (Case C-600/23), which reshapes the contours of sports arbitration under EU law. With particular focus on judicial review and EU public policy, the author explores how the Court balances the autonomy of arbitral mechanisms like CAS with the imperative of effective judicial protection — a judgment that could have far-reaching implications for the future of dispute resolution in sport
Recensione di Robert G. La France, Bachiacca: artist of the Medici court, Firenze, Olschki, 2008
No full textABSTRACT ITALIANO
Francesco Ubertini detto il Bachiacca ebbe scarsa fortuna critica ma questo volume di Robert G. La France colma una lacuna grave nella critica d’arte con una solida monografia in lingua inglese che prende in esame tutte le opere e i documenti di questo pittore. Stefano Colonna giudica positivamente il libro, pubblicato da Leo Olschki, limitandosi a sottolineare che alcune opere, inserite come autografe dall’autore, presentino differenti qualità.
ENGLISH ABSTRACT
Francesco Ubertini called Bachiacca has had little critical fortune, but this book by Robert G. La France fills a serious lacuna in art criticism with a solid English monograph that examines all the existing works and documents. Stefano Colonna welcomes the book published by Leo Olschki and simply points out that some of the works included by the author as autograph have a different quality
Spaghetti Enriched with Inulin: Effect of Polymerization Degree on Quality Traits and α-Amylase Inhibition
No full textInulin is considered a dietary fiber and represents a noteworthy ingredient for food biofortification due to its health effects and its neutral taste. The aim of the work was the evaluation of the quality of pasta produced using whole-meal flours of two ancient Sicilian landraces (Senatore Cappelli-CAP and Timilia—TIM) fortified with two types of inulin (long-chain topinambur inulin IT and low-chain chicory inulin IC), at two different levels of substitution (2 and 4%) to evaluate its possible effect on α-amylase inhibition. The color indices L* and a* were mainly influenced by cultivars, while IT improved the sensory attributes, mainly the elasticity sensation, and influenced less the other sensory attributes: adhesiveness, color, odor, taste, and Over Quality Score for both landraces. The cooking quality was linked mainly to the landrace used, due to the very different gluten matrix of CAP and TIM. IC and IT showed promising α-Amy inhibitory activity with comparable IC50 values of 0.45 ± 0.04 and 0.50 ± 0.06 mg/mL. The enrichment of spaghetti with inulin with an inhibitory effect on α-amylase determined the hypoglycemic properties of pasta, thus lowering the corresponding IC50 value
The role of theragnostics in oncology: an interview with Stefano Buono
No full text Stefano Buono* speaks to Commissioning Editor, Sebastian Dennis-Beron: Stefano Buono is the Chief Executive Officer, a member of the board of directors, and a founder of Advanced Accelerator Applications (AAA). He has been responsible for overseeing AAA operations, including the development and commercialization of the current portfolio of diagnostic and therapeutic molecular nuclear medicine products, and listing AAA on Nasdaq (stock symbol: AAAP). Prior to founding the company in 2002, he worked as a physicist at the Centre for Advanced Studies, Research and Development, or CRS4, in Italy. During his 6-year tenure with CRS4, he headed a team of engineers working on different international research projects in the field of energy production and nuclear waste transmutation. Before working at CRS4, and alongside his appointment at CRS4, he worked with Physics Nobel Laureate Carlo Rubbia at The European Organization for Nuclear Research (CERN), the world’s largest research laboratory for particle physics, in Geneva, Switzerland. He actively participated in the development of CERN’s Adiabatic Resonance Crossing (ARC) method. He is the author of numerous scientific papers. He received his Master’s degree in Physics from the University of Turin, in Italy, in 1991. </jats:p
Hemp Flour Particle Size Affects the Quality and Nutritional Profile of the Enriched Functional Pasta
No full textThe rheological and chemical quality of pasta samples, which were obtained using the durum wheat semolina fortified with the hemp seed solid residue, after oil extraction, sieved at 530 mu m (Hemp 1) or 236 mu m (Hemp 2) at different percentages of substitution (5%, 7.5%, and 10%, were evaluated. The total polyphenolic content in hemp flour was quantified in the range of 6.38-6.35 mg GAE/g, and free radical scavenging was included in the range from 3.94-3.75 mmol TEAC/100 g in Hemp 1 and Hemp 2, respectively. The phenolic profiles determined by UHPLC-ESI/QTOF-MS showed that cannabisin C, hydroxycinnamic and protocatechuic acids were the most abundant phenolic compounds in both hemp flours. Among the amino acids, isoleucine, glutamine, tyrosine, proline, and lysine were the most abundant in raw materials and pasta samples. Although the hemp seeds were previously subjected to oil extraction, hemp flours retain about 8% of oil, and the fatty acids present in the largest amount were linoleic acid and alpha-linolenic acid. Characterization of the minerals showed that the concentration of macro and trace elements increased according to fortification percentage. Sensory evaluation and cooking quality indicated that the best performance in terms of process production and consumer acceptance was obtained using Hemp 2 at 7.5%. Hemp supplementation could be a potential option for producing high-quality, nutritionally rich, low-cost pasta with good color and functionality
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