Competition between Polar and Antiferrodistortive Modes and Correlated Dynamics of the Methylammonium Molecules in MAPbI3_3 from Anelastic and Dielectric Measurements

The mechanisms behind the exceptional photovoltaic properties of the metallorganic perovskites are still debated, and include a ferroelectric (FE) state from the ordering of the electric dipoles of the organic molecules. We present the first anelastic (complex Young's modulus) and new dielectric measurements on CH$_{3}$NH$_{3}$PbI$_3$, which provide new insight on the reorientation dynamics of the organic molecules, and the reason why they do not form a FE state. The permittivity is fitted within the tetragonal phase with an expression that includes the coupling between FE and octahedral tilt modes, indicating that the coupling is competitive and prevents FE ordering. The onset of the orthorhombic phase is accompanied by sharp stiffening, analogous to the drop of permittivity, due to the hindered molecular dynamics. On further cooling, an intense anelastic relaxation process without a dielectric counterpart suggests the reorientation of clusters of molecules with strong antiferroelectric correlations.Comment: accepted in J. Phys. Chem. Let

Stability of Cubic FAPbI3_3 from X-ray Diffraction, Anelastic, and Dielectric Measurements

Among the hybrid metal-organic perovskites for photovoltaic applications FAPbI_3 (FAPI) has the best performance regarding efficiency and the worst regarding stability, even though the reports on its stability are highly contradictory. In particular, since at room temperature the cubic alpha phase, black and with high photovoltaic efficiency, is metastable against the yellow hexagonal delta phase, it is believed that alpha-FAPI spontaneously transform into delta-FAPI within a relatively short time. We performed X-ray diffraction and thermogravimetric measurements on loose powder of FAPI, and present the first complete dielectric and anelastic spectra of compacted FAPI samples under various conditions. We found that alpha-FAPI is perfectly stable for at least 100 days, the duration of the experiments, unless extrinsic factors induce its degradation. In our tests, degradation was detected after exposure to humidity, strongly accelerated by grain boundaries and the presence of delta phase, but it was not noticeable on the loose powder kept in air under normal laboratory illumination. These findings have strong implications on the strategies for improving the stability of FAPI without diminishing its photovoltaic efficiency through modifications of its composition

In Defense of Irreducible Relations

At least since Russell, mainstream analytic philosophy has distinguished internal and external relations and acknowledged the existence of both. This seems in line with both the manifest and scientific images of the world. However, there is a recent deflationary trend about relations, which focuses on the truthmakers of relational statements in order to show that putative external relations are in fact internal, and that internal relations do not really exist. Lowe’s posthumous 2016 paper is a thorough presentation of this line of thought. This article critically analyzes Lowe’s arguments in that paper, and some related arguments in recent works. It finds them wanting and thus reaffirms the irreducible reality of relations

Case Histories Paper: Jackup Rig Spud Can Penetration: A 6,000 Ton Load Test

One of the most exciting geotechnical problems for the offshore engineer is the prediction of mobile jack-up rig spud can penetration. Jack-up drilling rigs are used to drill offshore oil and gas wells in water depths up to about 100 m. The rigs are supported by circular “spud can” foundations fitted at the end of extendable platform legs. Upon arrival to the site the jack-up extends the legs to the sea floor and self-elevates out of the water. This action forces the spud cans into the seabed until soil capacity is attained. Prior to jacking the rig out of the water, a geotechnical borehole is made from the rig to verify soil conditions and estimate bearing capacity and leg penetration. The geotechnical engineer makes predictions of foundation capacity in real time; the predictions are then verified by the actual behavior of the footing under the 6,000 ton preload. This paper presents experience with bearing capacity predictions versus field measurements from over 15 offshore sites. Relatively simple closed form bearing capacity formulas are shown to provide good predictions for real behavior of these large scale foundations

A time tracking system for EU-funded INFN projects

The aim of this work is to describe the structure of a web application to support EU-funded INFN projects in the process of time tracking and reporting. The system has been designed in the early 2010s, following the growth of the EU-funded projects and the need for a framework to handle consistent reports according to the EU guidelines. One objective of this project is to guarantee and certify a valid distribution of hours declared on EU projects by INFN personnel in consistency with the official INFN clocking system, the scientific project management system and, overall, any signed agreements between the INFN and the founding bodies. The system allows the project participants to declare the hours worked on their projects, detailing their distribution across days, work packages and tasks. Interfaces are provided for Project Managers and Financial Officers to manage a project and monitor its trend. This activity is also supported by the INFN Business Intelligence Service, integrated with this system, to provide comprehensive reports for the upper management

Ethylenediurea (EDU) Affects the Growth of Ozone-Sensitive and Tolerant Ash ( Fraxinus excelsior

Adult ash trees (Fraxinus excelsior L.), known to be sensitive or tolerant to ozone, determined by presence or absence of foliar symptoms in previous years, were treated with ethylenediurea (EDU) at 450 ppm by gravitational trunk infusion over the 2005 growing season (32.5 ppm h AOT40). Tree and shoot growth were recorded in May and September. Leaf area, ectomycorrhizal infection, and leaf and fine root biomass were determined in September. EDU enhanced shoot length and diameter, and the number and area of leaves, in both O3-sensitive and tolerant trees. However, no EDU effects were recorded at the fine root and tree level. Therefore, a potential for EDU protection against O3-caused growth losses of forest trees should be evaluated during longer-term experiments

Open University vs. Consorzio Nettuno: An Institutional Analysis of Two Technology Enabled Higher Educational Systems

Assuming a rational perspective, the adoption and development of a new organisational technology can be viewed as a way to achieve an higher level of efficiency by finding the best way to fully exploit its potential. In other words, one might sustain that since organisations do initially ignore how to best deal with an innovative technology, they engage in a trial and error learning process that finally leads to the x-efficiency frontier. Once this knowledge is achieved, it will probably be spread around by external agents (e.g. consultants) enabling an imitative process. Thus in the long run all organisations will make almost the same efficient use of a mature organisational technology. In this paper we tried to explore how the same technology (eLearning) has been adopted by two diverse educational organisations. The patterns of development have been studied across time to verify if a progressive convergence has occurred. Results are providing some useful insights on what variables must be paid attention to when transferring a technological organisational innovation in a different settin

Nuovi tool della Direzione Sistemi Informativi

Area Ricerca: Obiettivi e motivazioni Svecchiamento parco applicativo (> 15 y !) Criticità tecnologiche, infrastrutturali e di sicurezza Requisiti e contesto profondamente diversi Software obsoleto non più manutenibile (effort non investito) Pianificare una formazione efficace sugli strumenti rilasciati Conoscenza dei tool e dei processi basata su passaparola e memoria storica Impossibile strutturare una formazione su tool vecchi Costituzione di un parco applicativo omogeneo (FOE vs FE