Origin of Polarization in Bismuth Sodium Titanate-Based Ceramics.

The classical view of the structural changes that occur at the ferroelectric transition in perovskite-structured systems, such as BaTiO3, is that polarization occurs due to the off-center displacement of the B-site cations. Here, we show that in the bismuth sodium titanate (BNT)-based composition 0.2(Ba0.4Sr0.6TiO3)-0.8(Bi0.5Na0.5TiO3), this model does not accurately describe the structural situation. Such BNT-based systems are of interest as lead-free alternatives to currently used materials in a variety of piezo-/ferroelectric applications. A combination of high-resolution powder neutron diffraction, impedance spectroscopy, and ab initio calculations reveals that Ti4+ contributes less than a third in magnitude to the overall polarization and that the displacements of the O2- ions and the A-site cations, particularly Bi3+, are very significant. The detailed examination of the ferroelectric transition in this system offers insights applicable to the understanding of such transitions in other ferroelectric perovskites, particularly those containing lone pair elements

Utilización de agroinsumos en Paspalum atratum cv. Cambá FCA

The aim of this work was to assess the effect of agro-inputs in biomass production of Paspalum atratum cv. Cambá and in soil biological activity. The sowing of pasture was carried out in pots with sandy soil. Seven treatments and five repetitions were applied; Control (T), Mineral Fertilizer (FM) 100 kg.ha1 , Vermicompost (LC) 40 tn.ha-1 , Vermicompost + Basalt (LC + B) 40 tn.ha-1 and 2.5 tn.ha-1 respectively, Compost (C) 40 tn.ha-1 , Compost + Basalt (C + B) 40 tn.ha-1 and 2.5 tn.ha-1 respectively and basalt powder (B) 2.5 tn.ha-1 . The plants were cut three times after that they were extracted. Height, amount of tillers, dry weight of the aerial part of the plants, radical dry weight and global biological activity were measured. ANOVA and means comparison by Tukey (α <0.05) were performed. When the first cut was carried out, the variable height obtained was the lowest in B treatment and after that measurement no other treatment denoted meaningful differences. The amount of tillers showed no meaningful differences among treatments until the first cut was performed. In the following measurements the LC treatment obtained the highest values and B the lowest ones. Regarding biomass aerial weight in the first cut, there were no meaningful differences between treatments and in the following cuts the LC treatment reached the highest value. On the other hand, the highest value of root dry weight was obtained by FM treatment, differing statistically only from B. The Global Biological Activity was similar among treatments.El objetivo del trabajo fue evaluar el efecto del uso de agroinsumos sobre la producción de biomasa de Paspalum atratum cv. Cambá y en la actividad biológica del suelo. El ensayo se realizó en macetas conteniendo suelo arenoso. Se aplicaron siete tratamientos con cinco repeticiones cada uno en un diseño completo al azar. Los tratamientos aplicados fueron: Testigo (T): suelo solo, Fertilizante Mineral (FM) 100 kg.ha-1, Lombricompost (LC) 40 tn.ha-1, Lombricompost + Basalto (LC + B) 40 tn.ha-1 y 2,5 tn.ha-1 respectivamente, Compost (C) 40 tn.ha-1, Compost + Basalto (C+B) 40 tn.ha-1 y 2,5 tn.ha-1 respectivamente y polvo de basalto (B) 2,5 tn.ha-1. Se realizaron 3 cortes, y en el último se extrajeron las plantas. Se midió altura, número de macollos, peso seco de parte aérea, peso seco radical y actividad biológica global. Se realizó ANAVA y comparación de medias por Tukey (α<0,05) observándose que para altura previo al primer corte B arrojó el menor valor, posterior al primer corte ningún tratamiento tuvo diferencias significativas. Para número de macollos no se encontraron diferencias significativas entre tratamientos hasta el primer corte, en las siguientes mediciones el tratamiento LC obtuvo los mayores valores y B los menores. Respecto a Peso Seco Aéreo en el primer corte no hubo diferencias significativas entre tratamientos y en los siguientes cortes el mayor valor lo tuvo el tratamiento LC. Para Peso Seco Radical el mayor valor lo obtuvo el tratamiento FM diferenciándose estadísticamente solo de B. Para Actividad Biológica Global no se encontraron diferencias estadísticamente significativas entre tratamientos

Nuclear dynamics of singlet exciton fission: a direct observation in pentacene single crystals

Singlet exciton fission (SEF) is a key process in the development of efficient opto-electronic devices. An aspect that is rarely probed directly, and yet has a tremendous impact on SEF properties, is the nuclear structure and dynamics involved in this process. Here we directly observe the nuclear dynamics accompanying the SEF process in single crystal pentacene using femtosecond electron diffraction. The data reveal coherent atomic motions at 1 THz, incoherent motions, and an anisotropic lattice distortion representing the polaronic character of the triplet excitons. Combining molecular dynamics simulations, time-dependent density functional theory and experimental structure factor analysis, the coherent motions are identified as collective sliding motions of the pentacene molecules along their long axis. Such motions modify the excitonic coupling between adjacent molecules. Our findings reveal that long-range motions play a decisive part in the disintegration of the electronically correlated triplet pairs, and shed light on why SEF occurs on ultrafast timescales

CubeSat Single-Photon Detector Module for Performing In-Orbit Laser Annealing to Heal Radiation Damage

Silicon-based single-photon avalanche photodiodes (SPADs), widely considered for satellite-based quantum communications, suffer a constant increase of dark count rate (DCR) from radiation-induced proton displacement damage in their active areas. When this accumulated damage causes the DCR to exceed a certain threshold (for example, 10,000 counts per second), the SPADs become unreliable for quantum communications, limiting mission lifetime. Previous ground experiments showed that radiation-induced DCR of synthetically irradiated SPADs could be significantly improved by high-power laser annealing, a localized heating of SPADs’ active areas using a focused laser beam. The next step is therefore to demonstrate realtime laser annealing on constantly irradiated SPADs in actual low-Earth-orbit is viable. To facilitate this study, the University of Waterloo team built a miniaturized software controllable SPAD module as part of the annealing payload on CAPSat (Cool Annealing Payload Satellite), a 3U CubeSat satellite developed by a team from the University of Illinois Urbana-Champaign. We present the concept of in-orbit laser annealing and the electronic platform of the SPAD module containing four detectors supporting thermal and laser annealing and detector characterization. The CAPSat, launched and deployed in a low-Earth orbit at 400 km altitude from the International Space Station in October 2021, was intended to assess the viability of this approach before incorporating SPADs in future quantum satellite missions, especially in quantum receivers

An ab initio study of oxide ion dynamics in type-II Bi3NbO7

Oxide ion dynamics in the type-II phase of Bi3NbO7have been studied using a series of DFT molecular dynamics calculations.</p

The significance of the amorphous potential energy landscape for dictating glassy dynamics and driving solid-state crystallisation

Contains fulltext : 180674.pdf (publisher's version ) (Open Access

Structural and electrical behaviour in Bi14YO22.5

National Science Centre Poland for project grant numbers 2012/05/E/ ST3/02767 and 2013/09/N/ST3/0432

Structural mapping in statistical word problems: A relational reasoning approach to Bayesian inference

Presenting natural frequencies facilitates Bayesian inferences relative to using percentages. Nevertheless, many people, including highly educated and skilled reasoners, still fail to provide Bayesian responses to these computationally simple problems. We show that the complexity of relational reasoning (e.g., the structural mapping between the presented and requested relations) can help explain the remaining difficulties. With a non-Bayesian inference that required identical arithmetic but afforded a more direct structural mapping, performance was universally high. Furthermore, reducing the relational demands of the task through questions that directed reasoners to use the presented statistics, as compared with questions that prompted the representation of a second, similar sample, also significantly improved reasoning. Distinct error patterns were also observed between these presented- and similar-sample scenarios, which suggested differences in relational-reasoning strategies. On the other hand, while higher numeracy was associated with better Bayesian reasoning, higher-numerate reasoners were not immune to the relational complexity of the task. Together, these findings validate the relational-reasoning view of Bayesian problem solving and highlight the importance of considering not only the presented task structure, but also the complexity of the structural alignment between the presented and requested relations