Effects of a uniform acceleration on atom-field interactions

We review some quantum electrodynamical effects related to the uniform acceleration of atoms in vacuum. After discussing the energy level shifts of a uniformly accelerated atom in vacuum, we investigate the atom-wall Casimir-Polder force for accelerated atoms, and the van der Waals/Casimir-Polder interaction between two accelerated atoms. The possibility of detecting the Unruh effect through these phenomena is also discussed in detail.Comment: 6 pages. Special Issue: 20th Central European Workshop on Quantum Optics - Stockholm - June 201

Non-thermal effects of acceleration in the resonance interaction between two uniformly accelerated atoms

We study the resonance interaction between two uniformly accelerated identical atoms, one excited and the other in the ground state, prepared in a correlated (symmetric or antisymmetric) state and interacting with the scalar field or the electromagnetic field in the vacuum state. In this case (resonance interaction), the interatomic interaction is a second-order effect in the atom-field coupling. We separate the contributions of vacuum fluctuations and radiation reaction to the resonance energy shift of the system, and show that only radiation reaction contributes, while Unruh thermal fluctuations do not affect the resonance interaction. We also find that beyond a characteristic length scale related to the atomic acceleration, non-thermal effects in the radiation reaction contribution change the distance-dependence of the resonance interaction. Finally, we find that previously unidentified features appear, compared with the scalar field case, when the interaction with the electromagnetic field is considered, as a consequence of the peculiar nature of the vacuum quantum noise of the electromagnetic field in a relativistically accelerated background.Comment: 10 page

The effects of seasonal variability of precipitation and vegetation cycle on enhanced weathering for carbon sequestration

Enhanced weathering (EW) is one of the most promising technologies for sequestering atmospheric carbon. It consists on accelerating the chemical weathering fluxes naturally occurring in soils, by means of the addition of silicate minerals (i.e., forsterite), used as amendments, to the soil. If crushed into micrometer-sized particles, these minerals are characterized by high dissolution rates, that may be further improved under high soil water content and low pH conditions. Before actually applying EW technique at the global scale for carbon sequestration, an in-depth characterization of weathering and carbon sequestration rates, under different environmental conditions, is needed, also looking at correlated beneficial/detrimental effects. In this context, modeling approaches may play a pivotal role, since they allow to achieve this goal without affording costs required by laboratory and field experiments. The present study describes the application of a dynamic mass balance model connecting ecohydrological, biogeochemical and olivine dissolution dynamics. The model is composed of four connected components and is solved through an explicit system of eight mass balance total differential equations and an implicit one having 22 algebraic equations. In this study, the model is applied to two sites in Italy (i.e., Sicily, in the south and the Padan plain, in the north) and two in the USA (i.e., California, in the south-west and Iowa, in the north-central area). The most common crops for the case studies, i.e., wheat for Sicily and California and corn for the Padan plain and Iowa are here considered, along with the most frequent soil types, namely the clay loam for Sicily and California and the silty clay loam for the Padan plain and Iowa. Maps of lithological composition of bedrocks and spatial distributions of soil pH have been also used to calibrate the background weathering flux, responsible of the H+ consume from all the minerals naturally present in the soil. Apart from deriving the most suitable locations, among those presented, providing the highest weathering and carbon sequestration rates, these simulations allow to assess the role of different climate, crop and soil types on EW dynamics, in perspective to find the combination that maximizes the CO2 sequestration

Dynamical atom-wall Casimir-Polder effect after a sudden change of the atomic position

We investigate the dynamical Casimir-Polder force between an atom and a conducting wall during the time evolution of the system from a partially dressed state. This state is obtained by a sudden change of the atomic position with respect to the plate. To evaluate the time-dependent atom-plate Casimir-Polder force we solve the Heisenberg equations for the field and atomic operators by an iterative technique. We find that the dynamical atom-plate Casimir-Polder interaction exhibits oscillation in time, and can be attractive or repulsive depending on time and the atom-wall distance. We also investigate the time dependence of global observables, such as the field and atomic Hamiltonians, and discuss some interesting features of the dynamical process bringing the interaction energy to the equilibrium configuration.Comment: 10 pages, 3 figures, submitted to Journal of Physics: Conference Series (Proceedings of the DICE2022 Conference - Castiglioncello, Italy

The Gelling Ability of Some Diimidazolium Salts: Effect of Isomeric Substitution of the Cation and Anion

The gelling ability of some geminal imidazolium salts was investigated both in organic solvents and in water solution. Organic salts differing either in the cation or anion structure were taken into account. In particular, the effects on the gelphase formation of isomeric substitution on the cation or anion as well as of the use of mono- or dianions were evaluated. As far as the cation structure is concerned, isomeric cations, such as 3,3’-di-n-octyl-1,1’-(1,4-phenylenedimethylene)diimidazolium and 3,3’-di-n-octyl-1,1’-(1,3-phenylenedimethylene) diimidazolium, were used. On the other hand, in addition to the bromide anion, isomeric dianions, such as the 1,5- and 2,6-naphthalenedisulfonate anions, were also examined. After preliminary gelation tests, different factors affecting the obtained gel phases, such as the nature of the solvent, organogelator concentrations, and action of external stimuli, were analyzed. The gel-phase formation was also studied as a function of time, by using resonance light scattering measurements. Gel morphologies were analyzed by scanning electron microscopy. To further support the understanding of the different behavior shown by the isomeric cations, some representative ion pairs were analyzed by DFT-based investigations. The collected data underline the significant role played by isomeric substitution of both cation and anion structures in determining the gelling capability of the investigated salts, as well as the properties of the gel phases. Finally, DFT investigations were helpful in the identification of the structural features affecting the self-assembly

Integrating spatially-and temporally-heterogeneous data on river network dynamics using graph theory

: The study of non-perennial streams requires extensive experimental data on the temporal evolution of surface flow presence across different nodes of channel networks. However, the consistency and homogeneity of available datasets is threatened by the empirical burden required to map stream network expansions and contractions. Here, we developed a data-driven, graph-theory framework aimed at representing the hierarchical structuring of channel network dynamics (i.e., the order of node activation/deactivation during network expansion/retraction) through a directed acyclic graph. The method enables the estimation of the configuration of the active portion of the network based on a limited number of observed nodes, and can be utilized to combine datasets with different temporal resolutions and spatial coverage. A proof-of-concept application to a seasonally-dry catchment in central Italy demonstrated the ability of the approach to reduce the empirical effort required for monitoring network dynamics and efficiently extrapolate experimental observations in space and time

Fluorescent naphthalimide-imidazolium hydrogels for biomedical applications

Bioimaging and in vivo imaging are cornerstone technologies in support of biomedical diagnosis. However, in some cases imaging methods have increased cancer risks for patients. Moreover, the most widely used diagnostic medical imaging technique, X-ray imaging, is the largest man-made source of radiation exposure to the general population. Thus, the research of new efficient and less invasive materials for imaging is quite urgent. Supramolecular hydrogels have recently proved to be promising biological carriers to load versatile bioimaging agents for in vitro or in vivo bioimaging, thanks to the ability to undergo reversible swelling and gel–sol transition in response to various physiological stimuli. In addition, the biodegradability and biocompatibility allowed the use of supramolecular gels also for cancer diagnosis, as they can be facilely endocytosed into cells [1]. Remembering the good biological response of some imidazolium derived hydrogels [2], fluorescent imidazolium organic salts, that should own the double function of gelator and bioimaging agent, have been synthesized. New fluorescent hydrogels with interesting physico-chemical properties (rheology, gel-sol temperature transition and optical properties) have been tested for anti-proliferative activity, in vitro bioimaging on cancer cells and controlled release of gelator in physiological medium. Results evidence how these hydrogels can be potentially investigated as new theranostic media for anticancer researc

An automatic ANN-based procedure for detecting optimal image sequences supporting LS-PIV applications for rivers monitoring

River flow monitoring has recently experienced rapid development due to advancements in optical methods, which are non-intrusive and enhance safety conditions for operators. Surface velocity fields are obtained recording and analyzing displacements of floating tracer materials, artificially introduced or already present on the water surface. River discharge can be assessed coupling the surface velocity fields with geometric data of a cross section. The accuracy of optical techniques is strongly affected by different environmental and hydraulic factors, and software parameterization, with tracer features that often play a prominent role. An adequate density and spatial distribution of tracer is required to ensure a complete characterization of surface velocity fields. In practical applications such conditions might occur only for a limited portion of the entire acquired images sequence. This work proposes an automatic procedure for identifying and extracting the best portion of a recorded video in terms of seeding characteristics and demonstrates how LS-PIV software performances can be enhanced through this approach. The procedure is implemented through a data-driven empirical approach based on an Artificial Neural Network, trained using data collected during an extensive measurement campaign across different rivers in Sicily (Italy). Performances are evaluated in terms of error in reproducing surface velocity profiles along specific transects, where benchmark profiles derived using an Acoustic Doppler Current Profiler are available. The procedure, also tested via numerical simulations on synthetic image sequences, outperformed an approach based on an existing metric for seeding characterization and represents a simple and useful tool for LS-PIV based applications

UN SISTEMA DI EARLY WARNING RELATIVO AL RISCHIO IDRAULICO FLUVIALE IN AMBITO URBANO BASATO SULLA DEFINIZIONE DI SCENARI DI EVENTO: IL CASO STUDIO DI PALERMO

La progressiva espansione delle aree urbanizzate, osservata negli ultimi decenni a scala globale, ha profondamente modificato i processi di formazione e trasferimento del deflusso superficiale ed ha portato ad un considerevole aumento degli elementi esposti a rischio alluvioni. I cambiamenti climatici in atto hanno inoltre indotto un’intensificazione degli eventi meteorici, con un probabile incremento della frequenza e della severità di eventi estremi in ambito urbano come urban flood e fash flood. Secondo una recente stima da parte della Commissione Europea [1], nel periodo 1980-2017 i danni causati da disastri naturali hanno superato i 500 milioni di euro, di cui il 90% dovuti ad eventi idrometeorologici rari e particolarmente intensi per i quali non era stata diramata un’allerta preventiva o non erano state adottate adeguate misure di pianificazione territoriale. È dunque evidente la necessità, specialmente in aree urbane e ad alta densità abitativa, di sviluppare efficaci strumenti previsionali atti alla mitigazione del rischio idraulico e idrogeologico sia in fase di pianificazione che in corso di evento per la gestione emergenziale. Il presente studio si inserisce in questo contesto, proponendo un Early Warning System (EWS) per rischio idraulico sviluppato relativamente al tratto urbano del Fiume Oreto, principale corso d’acqua attraversante la città di Palermo (Italia). In particolare, è stato sviluppato un sistema capace di determinare una relazione fra possibili scenari di evento e alcuni potenziali precursori. L’EWS proposto è in grado di individuare potenziali punti di prima esondazione, zone di allagamento e pericolosità in funzione della tipologia di evento pluviometrico previsto e delle condizioni iniziali di umidità del bacino. La tipologia dell’evento meteorico atteso viene definita mediante forma dello ietogramma, altezza cumulata e durata prevista, dedotti sulla base delle informazioni riportate nei Bollettini di Vigilanza Nazionale e quindi con preavviso di 24/48 ore. Le condizioni iniziali di umidità vengono invece stimate in tempo reale attraverso un proxy dato dal tirante idrometrico osservato in una sezione del corso d’acqua poco più a monte dell’area di analisi, dove è ubicata la stazione idrometrica in telemisura Ponte Parco dell’Autorità di Bacino. Il sistema è basato sull’utilizzo in tempo reale di soglie pluviometriche numeriche precedentemente definite per il bacino in analisi [2]; tali soglie, per fissate condizioni iniziali di saturazione del bacino e ietotipo, forniscono una famiglia di curve a isoportata critica, dalle quali, note l’altezza cumulata di pioggia e la durata dell’evento previsto, è possibile stimare la portata al picco del corrispondente idrogramma di piena. Una volta stimata la massima portata attesa, il sistema è in grado di associare un corrispondente scenario di evento, sfruttando una libreria precostruita di scenari di eventi preliminarmente sviluppata offline attraverso una modellazione idrologica ed idraulica ad alto livello di dettaglio e considerando diversi idrogrammi di progetto