Tailoring Dielectric Properties of Multilayer Composites Using Spark Plasma Sintering

A straightforward and simple way to produce well-densified ferroelectric ceramic composites with a full control of both architecture and properties using spark plasma sintering (SPS) is proposed. SPS main outcome is indeed to obtain high densification at relatively low temperatures and short treatment times thus limiting interdiffusion in multimaterials. Ferroelectric/dielectric (BST64/MgO/BST64) multilayer ceramic densified at 97% was obtained, with unmodified Curie temperature, a stack dielectric constant reaching 600, and dielectric losses dropping down to 0.5%, at room-temperature. This result ascertains SPS as a relevant tool for the design of functional materials with tailored properties

Improved local-constant-field approximation for strong-field QED codes

The local-constant-field approximation (LCFA) is an essential theoretical tool for investigating strong-field QED phenomena in background electromagnetic fields with complex spacetime structure. In our previous work [Phys.~Rev.~A~\textbf{98}, 012134 (2018)] we have analyzed the shortcomings of the LCFA in nonlinear Compton scattering at low emitted photon energies for the case of a background plane-wave field. Here, we generalize that analysis to background fields, which can feature a virtually arbitrary spacetime structure. In addition, we provide an explicit and simple implementation of an improved expression of the nonlinear Compton scattering differential probability that solves the main shortcomings of the standard LCFA in the infrared region, and is suitable for background electromagnetic fields with arbitrary spacetime structure such as those occurring in particle-in-cell simulations. Finally, we carry out a systematic procedure to calculate the probability of nonlinear Compton scattering per unit of emitted photon light-cone energy and of nonlinear Breit-Wheeler pair production per unit of produced positron light-cone energy beyond the LCFA in a plane-wave background field, which allows us to identify the limits of validity of this approximation quantitatively.Comment: 15 pages, 3 figure

Implementing nonlinear Compton scattering beyond the local constant field approximation

In the calculation of probabilities of physical processes occurring in a background classical field, the local constant field approximation (LCFA) relies on the possibility of neglecting the space-time variation of the external field within the region of formation of the process. This approximation is widely employed in strong-field QED as it allows to evaluate probabilities of processes occurring in arbitrary electromagnetic fields starting from the corresponding quantities computed in a constant electromagnetic field. Here, we demonstrate in the case of nonlinear single Compton scattering that the LCFA is quantitatively and qualitatively insufficient for describing the low-energy part of the emitted photon probability. In addition, we provide a simple recipe to implement an improved expression of the photon emission probability beyond the LCFA in numerical codes, which are an essential tool to interpret present and upcoming experiments in strong-field QED.Comment: 12 pages, 3 figur

Physics of traffic and the crowds theory: a multidisciplinary approach to mobility education

Crowding is a reality in which we find ourselves involved daily. The crowd produced in a traffic jam is a dynamic entity in which the application of physics, mathematics and biology can provide practical help to understand how and why this problematic situation occurs and what solutions can be found to resolve it. In the mobility education project \u201cSicuraMENTE\u201d, we carried out an experiment on the conduct of a crowd by simulating a situation of intense city traffic. Taking a cue from an experimental situation proposed in traffic physics, we have verified that a route with limited access can generate a traffic jam and the crowd of pedestrians can be mitigated by forcing the crowd to use dedicated streets. Taking the outgoing time of the student crowd from the outlet road, with and without the presence of an obstacle in the middle of the roadway, it was found that the traffic jam is resolved more quickly in the situation with an obstacle because the flow of people is divided into two separate channels, reducing the probability that two individuals are close and that this creates an obstruction (example of counter-intuitive physical principle). We also verified that the speed of the elements of the crowd influences the formation of traffic jams, which are on average more likely in the case of higher speed. These important aspects in the design of road networks and transport infrastructure have made students reason on physics\u2019 topics, but also on the correct conduct in traffic. The multidisciplinary approach in education for safe and sustainable mobility, so innovative in Italy, turned out to be effective in terms of teaching in the frame of a mix of academic disciplines, in which road safety education has become the context and the goal

Paleodepth variations on the Eratosthenes Seamount (Eastern Mediterranean): sea-level changes or subsidence?

International audienceThe Eratosthenes Seamount (Eastern Mediterranean) is interpreted as a crustal block in process of break up in response to subduction and incipient collision of the African and Eurasian Plates. Subsidence is considered to be the mechanism triggering the Messinian to Pleistocene water deepening above this unique structure. However, the application of a recently developed transfer equation of depth range distribution of benthic foraminifera indicates that sea-level changes may also have played a role, although it was generally minor. In particular, we suggest that across the Miocene/Pliocene boundary and during the Pliocene-Pleistocene, the eustatic signal is frequently coupled with uplifts and subsidence. The uplift of Cyprus across the Pliocene-Pleistocene transition is clearly recorded in the paleodepth curve. Micropaleontological studies and the use of this transfer equation based on the distribution of benthic foraminifera proves to be useful when studying the paleodepth history of complex sites, where tectonic and eustatic signals combine. We also show that marginal seas record global sea-level changes that can be identified even in tectonically active settings

Advanced Techniques for the Decipherment of Ancient Scripts

This contribution explores modern and traditional approaches to the decipherment of ancient writing systems. It surveys methods used by paleographers and epigraphers and state-of-the art applications of computational linguistics, such as models based on neural networks. It frames the contextual problems scholars encounter in dealing with ancient codes, the situations and preconditions of the unknown codes, their idiosyncrasies and peculiarities, and the potential solutions afforded by both traditional and novel methods of investigation

Buprestis splendens (Fabricius, 1774) (Coleoptera Buprestidae) on the Calabrian side of the "Parco Nazionale del Pollino" (Calabria, Italy): distribution and ecological observation

Buprestis splendens (Fabricius, 1774) (Coleoptera Buprestidae) is a rare European chorotype species, threatened throughout its distribution by global climate change, forest fires and the capture of specimens by collectors. To date, in Italy, its presence was only known in a few areas on the Lucanian side of the massif of Pollino. This report records the first, reliable sightings of its presence on the Calabrian side of the Pollino and in the mountains of Orsomarso. It also makes observations on its environment and the factors that put its survival at risk

Automatic induction of framenet lexical units in Italian

In this paper we investigate the applicability of automatic methods for frame induction to improve the coverage of IFrameNet, a novel lexical resource based on Frame Semantics in Italian. The experimental evaluations show that the adopted methods based on neural word embeddings pave the way for the assisted development of a large scale lexical resource for our language

A dual isotopic approach using radioactive phosphorus and the isotopic composition of oxygen associated to phosphorus to understand plant reaction to a change in P nutrition

Abstract Background Changing the phosphorus (P) nutrition leads to changes in plant metabolism. The aim of this study was to investigate how these changes are reflected in the distribution of 33P and the isotopic composition of oxygen associated to P (δ18OP) in different plant parts of soybean (Glycine max cv. Toliman). Two P pools were extracted sequentially with 0.3 M trichloroacetic acid (TCA P) and 10 M nitric acid (HNO3; residual P). Results The δ18OP of TCA P in the old leaves of the − P plants (23.8‰) significantly decreased compared to the + P plants (27.4‰). The 33P data point to an enhanced mobilisation of P from residual P in the old leaves of the − P plants compared to the + P plants. Conclusions Omitting P for 10 days lead to a translocation of P from source to sink organs in soybeans. This was accompanied by a significant lowering of the δ18OP of TCA P in the source organs due to the enzymatic hydrolysis of organic P. Combining 33P and δ18OP can provide useful insights in plant responses to P omission at an early stage