Trade-off modeling of superconducting levitation machines: theory and experiment

Based on the critical state model for the superconducting components, we develop a set of theoretical tools that allow to extract relevant engineering parameters of a superconducting levitation machine. We provide a number of analytical and numerical expressions for the evaluation of the electromagnetic quantities, energies and forces in 2D problems. This assumption includes: (i) rotational symmetric systems as those in bearings and motors, and also the case of (ii) translational symmetry as in long transportation lines. The theory, that trades off simplicity and predictive power builds on the vector potential/current density formulation of the Maxwell equations (A, J) and is validated by comparison against experimental tension-compression data in our universal test machine. As shown, very simple computer coding is required to implement the method.Funding of this research by Spanish MINECO and the European FEDER Program (Projects MAT2011-22719 and ENE2011-29741) and by Gobierno de Aragon (Research group T12) is gratefully acknowledged.Peer Reviewe

DFT calculation of the intermolecular exchange interaction in the magnetic Mn4_4 dimer

The dimeric form of the single-molecule magnet [Mn$_4$O$_3$Cl$_4$(O$_2$CEt)$_3$(py)$_3$]$_2$ recently revealed interesting phenomena: no quantum tunneling at zero field and tunneling before magnetic field reversal. This is attributed to substantial antiferromagnetic exchange interaction between different monomers. The intermolecular exchange interaction, electronic structure and magnetic properties of this molecular magnet are calculated using density-functional theory within generalized-gradient approximation. Calculations are in good agreement with experiment.Comment: 4 page

Supramolecular Hydrogels Consisting of Nanofibers Increase the Bioavailability of Curcuminoids in Inflammatory Skin Diseases

The low bioavailability of curcuminoids (CCMoids) limits their use in the treatment of inflammatory skin diseases. Our work shows that this constraint can be overcome upon their incorporation into supramolecular hydrogels assembled from a gemini-imidazolium amphiphilic gelator. Three structural CCMoid analogues were used to prepare supramolecular hydrogels, and it was observed that the concentration of both the gelator and CCMoid and the proportion of solvents influence the self-assembly process. Moreover, the mechanical properties of the nanostructured gels were studied to find the optimum gels, which were then further characterized microscopically, and their ability to release the CCMoid was evaluated. The physicochemical properties of the CCMoids play a fundamental role in the interaction with the gelator, influencing not only the gelation but also the morphology at the microscopic level, the mechanical properties, and the biopharmaceutical behavior such as the amount of CCMoid released from the gels. The nanostructured supramolecular hydrogels, which contain the CCMoids at much lower concentrations (μg/mL) in comparison to other products, promote the penetration of the CCMoids within the skin, but not their transdermal permeation, thus preventing any possible systemic effects and representing a safer option for topical administration. As a result, the CCMoid-containing hydrogels can effectively reduce skin inflammation in vivo, proving that these supramolecular systems are excellent alternatives in the treatment of inflammatory skin diseases.This work was supported by the projects PID2020-115663GB-C3-2, PID2019-108794GB-I00, and PID2020–115631GB-I00 funded by MCIN/AEI/10.13039/501100011033 from the Ministerio de Ciencia e Innovación. We thank AGAUR for a grant to consolidated research groups 2017SGR1277. A.G.-C. and N.A.-A. acknowledge the financial support from the Spanish Ministry Science, through the “Severo Ochoa” Programme for Centres of Excellence (FUNFUTURE) (2020-2023). A.G.-C. also acknowledges a Ramon y Cajal Grant (RYC-2017-22910).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

European Research Council (ERC) funding opportunities ¿ a 360° overview: Efficient electronic transport at room temperature by T-shaped molecules in graphene-based chemically modified three-terminal nanodevices

https://youtu.be/BOYyIILEFY

Spin-Phonon Coupling and Slow-Magnetic Relaxation in Pristine Ferrocenium

We report the spin dynamic properties of non-substituted ferrocenium complexes. Ferrocenium shows a field-induced single-molecule magnet behaviour in DMF solution while cobaltocene lacks slow spin relaxation neither in powder nor in solution. Multireference quantum mechanical calculations give a non-Aufbau orbital occupation for ferrocenium with small first excitation energy that agrees with the relatively large measured magnetic anisotropy for a transition metal S=1/2 system. The analysis of the spin relaxation shows an important participation of quantum tunnelling, Raman, direct and local-mode mechanisms which depend on temperature and the external field conditions. The calculation of spin-phonon coupling constants for the vibrational modes shows that the first vibrational mode, despite having a low spin-phonon constant, is the most efficient process for the spin relaxation at low temperatures. In such conditions, vibrational modes with higher spin-phonon coupling constants are not populated. Additionally, the vibrational energy of this first mode is in excellent agreement with the experimental fitted value obtained from the local-mode mechanism.The research reported here was supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (grants PGC2018-093863-B-C21, PID2019-108794GB-I00 and centres of excellence MDM-2017-0767 and Severo Ochoa FUNFUTURE (CEX2019-000917-S). E.R. thanks Generalitat de Catalunya for an ICREA Academia award and for the SGR2017-1289 and -1277 grants. S.G.-C. thanks the Generalitat de Catalunya for a Beatriu de Pinòs grant. M.A. acknowledges the Ministerio de Educación, Cultura y Deporte for an FPU predoctoral grant. Authors acknowledge computer resources, technical expertise and assistance provided by the CSUC. We want to thank Prof. Santiago Alvarez for his help with the Shape code.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Hetero-bimetallic paddlewheel clusters in coordination polymers formed by a water-induced single-crystal-to-single-crystal transformation

Herein we report a water-induced single-crystal to single-crystal transformation that involves the formation of hetero-bimetallic paddlewheel clusters in coordination polymers. Through this transformation, which involves the cleavage and formation of different coordination bonds, two different Cu(II)-Zn(II) and Cu(II)-Ni(II) paddle-wheel units exhibiting a 1 : 1 metal ratio were created.This work was supported by the Spanish MINECO (projects PN MAT2015-65354-C2-1-R and MAT2013-47869-C4-2-P), DGI grant BeWell (CTQ2013-40480-R), the Catalan AGAUR (project 2014-SGR-80 and 2014-SGR-17), and the ERC under the EU FP7 (ERC-Co 615954). J. A. thanks the Generalitat de Catalunya for a FI fellowship (2016FI B 00449). ICN2 and ICMAB acknowledge the support of the Spanish MINECO through the Severo Ochoa Centres of Excellence Programme, under Grants SEV-2013-0295 and SEV-2015-0496. The authors thank Dr N. Clos from the Serveis Cientifíco-Tècnics of the University of Barcelona for her assistance.Peer reviewe

Comparative Magnetic Studies in the Solid State and Solution of Two Isostructural 1D Coordination Polymers Containing CoII/NiII-Curcuminoid Moieties

Two novel 1D coordination chains containing the curcuminoid (CCMoid) ligand 9Accm have been characterized: [CoII(9Accm)2(4,4´-bpy)]n (1) and [NiII(9Accm)2(4,4´-bpy)]n (2). The two compounds were synthesized by solvothermal and microwave (MW) assisted techniques, respectively, and crystals of both systems were directly obtained from the mother solutions. Crystal structures of 1 and 2 prove that both systems are isostructural, with the ligands in a trans configuration. The two chains have been magnetically characterized in solution by paramagnetic 1H NMR, where 1 displayed typical features from CoII systems, with spread out signals; meanwhile, 2 showed diamagnetic behaviour. The dissociation of the latest in solution and the stability of the “[Ni(9Accm)2]” unit were proved by further experiments in C5D5N. Additional UV-Vis absorption and fluorescence studies in solution were performed using exclusively 1. In the solid state χMT vs. T and M/NµB vs. H/T data were collected and fitted for 1 and 2; both systems display Ising plane anisotropy, with significant D values. System 1 presented slow relaxation of the magnetization, displaying frequency dependence in the in-phase/out-phase ac magnetic susceptibility data, when an external dc field of 0.2 T was applied. Finally, 1 was deposited on a HOPG (highly oriented pyrolytic graphite) substrate by spin-coating and analysed by AFM.The authors thank N. Clos from the Serveis Científicotècnics de la UB for her great assistance regarding the magnetic data and are grateful to O. Roubeau (ICMA, CSIC and Universidad de Zaragoza) for his help in the data acquisition and refinement of the structure of compound 1. This work was supported by the MINECO (Spain) (Projects CTQ2012-32247, and MAT2013-47869-C4-2-P) and from the FONDECYT REGULAR grant 1110206. N.A.-A. acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2015-0496. The Advanced Light Source (S.J.T.) is supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under Contract DE-AC0205CH11231.Peer reviewe

The geometric and electronic structure of [(cyclam-acetato)Fe(N)+]: A genuine iron(V) species with a ground-state spin S = 1/2

Low‐spin, high‐valent iron centers: A high‐valent iron–nitrido species containing a FeV center is accessible by the photolysis of [(cyclam‐ac)FeIIIN3]+. The identity of the resulting [(cyclam‐ac)FeV(N)]+ species was verified by spectroscopic methods, magnetic susceptibility data, and DFT calculations (see picture). Unexpectedly, the analysis provides strong evidence for a low‐spin d3 (S=1/2) ground‐state electron configuration at the FeV center