3,138 research outputs found
La tomba del Tifone: effetti speciali etruschi
No full textGli autori esaminano la Tomba del Tifone di Tarquinia da tre diversi punti di vista archeologici: architettura e impaginato (G. Bagnasco Gianni); pittura tombale (M. Marzullo); scelte iconografiche legate a creature mostruose (L. Perego
Antitumor Platinum(II) Hybrid Compounds Based on a Glucosylglycerol Scaffold
No full textPlatinum(II) drugs such as cisplatin, carboplatin and oxaliplatin are antineoplastic drugs
clinically available for the treatment of different kinds of cancers, including ovarian
carcinoma. However, their use is limited by the occurrence of severe systemic side effects and
resistance [1, 2]. For these reasons, the development of new platinum-based compounds
endowed with higher selectivity against cancer cells and able to overcome resistance is an
active research field. A promising strategy to pursuit these goals is the design of hybrid
platinum(II) compounds bearing bioactive ligands able to selectively target cancer cells,
improve the platinum-mediated antitumor activity and/or overcome resistance by interacting
with selected targets known for their involvement in cancer resistance [3]. In this context, due
to its peculiar structure, 2-O-β-D-glucosylglycerol (a natural compound named Lilioside B)
[4] could be efficiently used at the same time as the complexing agent of platinum(II) and as
the point of attachment of cancer involved bioactive compounds. Thus, the present
communication will show some preliminary results on the synthesis and cytotoxicity data, on
ovarian cancer cells, of a water soluble platinum(II) hybrid compound in which, similarly to
carboplatin, a properly modified 2-O-β-D-glucosylglycerol is able to complex platinum(II).
References
1. Khoury, A.; Deo, K.M.; Aldrich-Wright, J.R. J. Inorg. Biochem., 2020, 207, 111070.
2. Rottenberg, S., Disler, C., & Perego, P. Nature reviews. Cancer, 2021, 21, 37.
3. Zuccolo, M,; Arrighetti, N.; Perego, P.; Colombo, D. Curr. Med. Chem., 2022, 29, 2566.
4. Kaneda, M.; Mizutani, K.; Takahashi, Y.; Kurono, G.; Nishikawa, Y. Tetrahedron Lett., 1974, 15,
3937
Multiscale Molecular Modelling of ATP‐Fueled Supramolecular Polymerisation and Depolymerisation**
No full textRaw research data supporting the publication Perego C. et al., ChemSystemsChem 2021, DOI: https://doi.org/10.1002/syst.20200003
A Cannibalistic Approach to Grand Canonical Crystal Growth
No full textCanonical molecular dynamics simulations of crystal growth from solution suffer from severe finite-size effects. As the crystal grows, the solute molecules are drawn from the solution to the crystal, leading to a continuous drop in the solution concentration. This is in contrast to experiments in which the crystal grows at an approximately constant supersaturation of a bulk solution. Recently, Perego et al. [J. Chem. Phys. 2015, 142, 144113] showed that in a periodic setup in which the crystal is represented as a slab, the concentration in the vicinity of the two surfaces can be kept constant while the molecules are drawn from a part of the solution that acts as a molecular reservoir. This method is quite effective in studying crystallization under controlled supersaturation conditions. However, once the reservoir is depleted, the constant supersaturation conditions cannot be maintained. We propose a variant of this method to tackle this depletion problem by simultaneously dissolving one side of the crystal while letting the other side grow. A continuous supply of particles to the solution due to the crystal dissolution maintains a steady solution concentration and avoids reservoir depletion. In this way, a constant supersaturation condition can be maintained for as long as necessary. We have applied this method to study the growth and dissolution of urea crystal from water solution under constant supersaturation and undersaturation conditions, respectively. The computed growth and dissolution rates are in good agreement with those obtained in previous studies
Beyond accuracy: enhancing multiple perspectives of recommendation through multi-objective optimization and evaluation
No full textI sistemi di raccomandazione sono diventati strumenti essenziali per alleviare il problema dell’information overload, fornendo suggerimenti personalizzati in vari settori, tra cui l'e-commerce, le piattaforme di streaming e i social network. Tradizionalmente, la valutazione e l'ottimizzazione dei sistemi di raccomandazione si sono concentrate sull'accuratezza come parametro principale di successo. Sebbene l'accuratezza sia fondamentale per predire le preferenze degli utenti, essa non affronta dimensioni più ampie, cruciali per migliorare la soddisfazione degli utenti, garantire l'equità degli stakeholder e affrontare gli impatti sociali. Inoltre, quando si considerano più obiettivi, spesso sorgono conflitti, cioè il miglioramento di un obiettivo può influire negativamente sugli altri, portando a uno spettro di possibili soluzioni ottimali. Queste sfide danno origine a diverse domande critiche: Come possono i sistemi di raccomandazione evolversi per bilanciare l'accuratezza con altri obiettivi, come la diversità, la novità e l'equità, soddisfacendo al contempo le esigenze di più parti interessate, tra cui utenti, fornitori di contenuti e piattaforme? Come possiamo valutare simultaneamente l'efficacia dei sistemi di raccomandazione attraverso diversi criteri? Come si può selezionare un'unica soluzione ottimale da un insieme di compromessi? Infine, possiamo progettare un framework generico per l'ottimizzazione dei sistemi di raccomandazione che tenga conto di obiettivi multipli, spesso in conflitto tra loro? Queste domande evidenziano le principali sfide aperte nel campo della ricerca sui sistemi di raccomandazione.
Questa tesi affronta queste lacune concentrandosi su due aree principali: le metodologie per la valutazione multi-obiettivo deli sistemi di raccomandazione e le sfide associate alla progettazione di sistemi di raccomandazione multi-obiettivo. Dopo un'esplorazione approfondita del background dei sistemi di raccomandazione e dell'ottimizzazione multi-obiettivo, la tesi fornisce contributi significativi nelle seguenti aree:
(i) l'applicazione delle frontiere di Pareto per condurre una valutazione multi-obiettivo di sistemi di raccomandazione basati su grafi, concentrandosi sugli aspetti di equità;
(ii) l'introduzione di indicatori di qualità per le frontiere di Pareto per scoprire il potenziale dei sistemi di raccomandazione al di là delle tradizionali metriche di accuratezza;
(iii) lo sviluppo di un quadro analitico per valutare la sensibilità dei sistemi di raccomandazione al tuning degli iperparametri in scenari multi-obiettivo;
(iv) uno studio sulla riproducibilità che identifica le principali sfide e ambiguità nella progettazione e nella valutazione dei sistemi di raccomandazione multi-obiettivo;
(v) la proposta di una nuova strategia di selezione di soluzioni Pareto-ottimali post-hoc, adattata esplicitamente ai task di raccomandazione;
(vi) la progettazione di un framework flessibile di sistema di raccomandazione multi-obiettivo che incorpora loss functions indipendenti dagli obiettivi e consapevoli della loro magnitudine per ottenere l'ottimizzazione di diversi obiettivi di raccomandazione.Recommender Systems (RSs) have become essential tools for alleviating information overload by providing personalized suggestions across various domains, including e-commerce, streaming platforms, and social networks. Traditionally, the evaluation and optimization of RSs have centered on accuracy as the primary success metric. While accuracy is critical for predicting user preferences, it fails to address broader dimensions crucial for enhancing user satisfaction, ensuring stakeholder fairness, and addressing societal impacts. Moreover, when multiple objectives are considered, conflicts often arise, i.e., improving one objective can detrimentally affect others, leading to a spectrum of possible optima. These challenges give rise to several critical questions: How can RSs evolve to balance accuracy with other objectives, such as diversity, novelty, and fairness, while meeting the needs of multiple stakeholders, including users, content providers, and platforms? How can we simultaneously evaluate RS effectiveness across diverse criteria? How can a single optimal solution be selected from a set of trade-offs? Finally, can we design a generic framework for optimizing RSs that accounts for multiple, often conflicting objectives? These questions highlight key open challenges in the field of RS research.
This dissertation addresses these gaps by focusing on two main areas: methodologies for multi-objective evaluation of RSs and the challenges associated with designing Multi-Objective Recommender Systems (MORSs). After an in-depth exploration of the background of RSs and multi-objective optimization, the thesis makes significant contributions in the following areas:
(i) the application of Pareto frontiers to conduct a multi-objective evaluation of graph-based RSs, focusing on fairness aspects;
(ii) the introduction of quality indicators for Pareto frontiers to uncover the potential of RSs beyond traditional accuracy metrics;
(iii) the development of an analytical framework to assess the sensitivity of RSs to hyper-parameter tuning in multi-objective scenarios;
(iv) a reproducibility study that identifies key challenges and ambiguities in the design and evaluation of MORSs;
(v) the proposal of a novel, post-hoc Pareto-optimal solution selection strategy tailored explicitly for RS tasks;
(vi) designing a flexible MORS framework incorporating objective-agnostic and scale-aware loss functions to achieve optimization across diverse recommendation objectives
Collective excitability, synchronization, and array-enhanced coherence resonance in a population of lasers with a saturable absorber
No full textIn this article we present a numerical study of the collective dynamics in a population of coupled semiconductor lasers with a saturable absorber, operating in the excitable regime under the action of additive noise. We demonstrate that temporal and intensity synchronization takes place in a broad region of the parameter space and for various array sizes. The synchronization is robust and occurs even for a set of nonidentical coupled lasers. The cooperative nature of the system results in a self-organization process which enhances the coherence of the single element of the population too and can have broad impact for detection purposes, for building all-optical simulators of neural networks and in the field of photonics-based computation
Array-enhanced synchronization and coherence resonance in coupled excitable semiconductor lasers
No full textWe present a numerical study of the nonlinear dynamics of a population of coupled semiconductor lasers with saturable absorber operating in the excitable regime [1] and described by a set of coupled Yamada models [2]. In particular we have investigated the self-organized synchronization process taking place spontaneously among the lasers, showing significant correlations between the spike-like pulses emitted by different lasers. Our findings demonstrate that synchronization in time and also in intensity occurs in a large region of the parameter space and for different population sizes and furthermore it is robust with respect to random distribution of the lasers' pump parameter which is linked to the excitability threshold
The nitrification inhibitor Vizura® reduces N2O emissions when added to digestate before injection under irrigated maize in the Po Valley (Northern Italy)
No full textThe agricultural area in the Po Valley is prone to high nitrous oxide (N2O) emissions as it is characterized by irrigated maize-based cropping systems, high amounts of nitrogen supplied, and elevated air temperature in summer. Here, two monitoring campaigns were carried out in maize fertilized with raw digestate in a randomized block design in 2016 and 2017 to test the effectiveness of the 3, 4 DMPP inhibitor Vizura® on reducing N2O-N emissions. Digestate was injected into 0.15 m soil depth at side-dressing (2016) and before sowing (2017). Non-steady state chambers were used to collect N2O-N air samples under zero N fertilization (N0), digestate (D), and digestate + Vizura® (V). Overall, emissions were significantly higher in the D treatment than in the V treatment in both 2016 and 2017. The emission factor (EF, %) of V was two and four times lower than the EF in D in 2016 and 2017, respectively. Peaks of NO3-N generally resulted in N2O-N emissions peaks, especially during rainfall or irrigation events. The water-filled pore space (WFPS, %) did not differ between treatments and was generally below 60%, suggesting that N2O-N emissions were mainly due to nitrification rather than denitrification
Disorder-induced localization of excitability in an array of coupled lasers
No full textWe report on the localization of excitability induced by disorder in an array of coupled semiconductor lasers with a saturable absorber. Through numerical simulations we show that the exponential localization of excitable waves occurs if a certain critical amount of randomness is present in the coupling coefficients among the lasers. The results presented in this Rapid Communication demonstrate that disorder can induce localization in lattices of excitable nonlinear oscillators, and can be of interest in the study of photonics-based random networks, neuromorphic systems, and, by analogy, in biology, in particular, in the investigation of the collective dynamics of neuronal cell populations
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