Magnetic Domains and Surface Effects in Hollow Maghemite Nanoparticles

In the present work, we investigate the magnetic properties of ferrimagnetic and noninteracting maghemite (g-Fe2O3) hollow nanoparticles obtained by the Kirkendall effect. From the experimental characterization of their magnetic behavior, we find that polycrystalline hollow maghemite nanoparticles are characterized by low superparamagnetic-to-ferromagnetic transition temperatures, small magnetic moments, significant coercivities and irreversibility fields, and no magnetic saturation on external magnetic fields up to 5 T. These results are interpreted in terms of the microstructural parameters characterizing the maghemite shells by means of an atomistic Monte Carlo simulation of an individual spherical shell model. The model comprises strongly interacting crystallographic domains arranged in a spherical shell with random orientations and anisotropy axis. The Monte Carlo simulation allows discernment between the influence of the structure polycrystalline and its hollow geometry, while revealing the magnetic domain arrangement in the different temperature regimes.Comment: 26 pages, 8 figures. In press in Phys. Rev.

Grand challenges in model-driven engineering : an analysis of the state of the research

In 2017 and 2018, two events were held—in Marburg, Germany, and San Vigilio di Marebbe, Italy, respectively—focusing on an analysis of the state of research, state of practice, and state of the art in model-driven engineering (MDE). The events brought together experts from industry, academia, and the open-source community to assess what has changed in research in MDE over the last 10 years, what challenges remain, and what new challenges have arisen. This article reports on the results of those meetings, and presents a set of grand challenges that emerged from discussions and synthesis. These challenges could lead to research initiatives for the community going forward

Vorticity Budget of Weak Thermal Convection in Keplerian disks

By employing the equations of mean-square vorticity (enstrophy) fluctuations in strong shear flows, we demonstrate that unlike energy production of turbulent vorticity in nonrotating shear flows, the turbulent vorticity of weak convection in Keplerian disks cannot gain energy from vortex stretching/tilting by background shear unless the asscoiated Reynolds stresses are negative. This is because the epicyclic motion is an energy sink of the radial component of mean-square turbulent vorticity in Keplerian disks when Reynolds stresses are positive. Consequently, weak convection cannot be self-sustained in Keplerian flows. This agrees with the results implied from the equations of mean-square velocity fluctuations in strong shear flows. Our analysis also sheds light on the explanation of the simulation result in which positive kinetic helicity is produced by the Balbus-Hawley instability in a vertically stratified Keplerian disk. We also comment on the possibility of outward angular momentum transport by strong convection based on azimuthal pressure perturbations and directions of energy cascade.Comment: 8 pages, 1 figure, emulateapj.sty, revised version in response to referee's comments, accepted by Ap

SMOS-NEXT: A New Concept for Soil Moisture Retrieval from Passive Interferometric Observations

This book is a collection of 19 articles which reflect the courses given at the Collège de France/Summer school “Reconstruction d'images − Applications astrophysiques“ held in Nice and Fréjus, France, from June 18 to 22, 2012. The articles presented in this volume address emerging concepts and methods that are useful in the complex process of improving our knowledge of the celestial objects, including Earth

Measurements of UV aerosol optical depth in the French Southern Alps

Routine measurements of global and diffuse UV irradiances at Briançon station (1310 m a.s.l.) are used to retrieve the direct solar irradiance and the aerosol optical depth (AOD), for cloudless days. Data of three years (2003, 2004, 2005) are analyzed; the results confirm those of a preliminary analysis for 2001, 2002. <br><br> The atmosphere is very clear in winter, with AODs between 0.05 and 0.1. The turbidity increases slowly in spring, starting end of February, with AODs around 0.2–0.3 in mid summer, some values reaching 0.4. A similar behaviour is observed for all years, with somewhat higher values in late summer for the year 2003

Recent Developments in OCL and Textual Modelling

The panel session of the 16th OCL workshop featured a lightning talk session for discussing recent developments and open questions in the area of OCL and textual modelling. During this session, the OCL community discussed, stimulated through short presentations by OCL experts, tool support, potential future extensions, and suggested initiatives to make the textual modelling community even more successful. This collaborative paper, to which each OCL expert contributed one section, summarises the discussions as well as describes the recent developments and open questions presented in the lightning talks

Bimetallic FeCu-MOF derivatives as heterogeneous catalysts with enhanced stability for electro-Fenton degradation of lisinopril

A bimetallic FeCu/NC core-shell catalyst, consisting in nanoparticles where zero-valent Fe and Cu atoms, slightly oxidized on their surface, are encapsulated by carbon has been successfully prepared by modifying the synthesis route of MIL(Fe)-88B. FeCu/NC possessed well-balanced textural and electrochemical properties. According to voltammetric responses, in-situ Fe(III) reduction to Fe(II) by low-valent Cu was feasible, whereas the high double-layer capacitance confirmed the presence of a great number of electroactive sites that was essential for continuous H2O2 activation to •OH via Fenton's reaction. Electrochemical impedance and distribution of relaxation times (DRT) analysis informed about the strong leaching resistance of FeCu/NC. To validate the promising features of this catalyst, the advanced oxidation of the antihypertensive lisinopril (LSN) was investigated for the first time. The heterogeneous electro-Fenton (HEF) treatment of 16.1 mg L-1 LSN solutions was carried out in a DSA/air-diffusion cell. At pH 3, complete degradation was achieved within 6 min using only 0.05 g L-1 FeCu/NC; at near-neutral pH, 100 % removal was also feasible even in actual urban wastewater, requiring 60–75 min. The FeCu/NC catalyst demonstrated high stability, still maintaining 86.5 % of degradation efficiency after 5 cycles and undergoing low iron leaching. It outperformed the monometallic (Fe/NC and Cu/NC) catalysts, which is explained by the Cu(0)/Cu(I)-catalyzed Fe(II) regeneration mechanism that maintains the Fenton's cycle. LC-MS/MS analysis allowed the identification of two main primary LSN by-products. It can then be concluded that the FeCu/NC-based HEF process merits to be further scaled up for wastewater treatment.Peer ReviewedPostprint (published version