Effect of band-filling and structural distortions on the Curie temperature of Fe-Mo double perovkites

By means of high resolution neutron powder diffraction at low temperature we have characterized the structural details of $\rm La_{x}Sr_{2-x}FeMoO_6$ ($0\leq {\rm x}\leq 0.5$) and $\rm Ca_{x}Sr_{2-x}FeMoO_6$ ($0\leq {\rm x}\leq 0.6$) series of compounds. This study reveals a similar variation of the mean bond-angle \FeOMo in both series. In contrast, the mean bond-distance \FeMoO\ increases with La but not with Ca substitution. Both series also present a different evolution of the Curie temperature ($T_C$), which raises in the La series and slightly decreases in the Ca one. We thus conclude that the enhancement of $T_C$ in the La series is due to the electron filling of the conduction band and a concomitant rising of the density of states at the Fermi level.Comment: Revtex, 4 Journal pages, 2 figures, 1 tabl

Structural response to O*-O' and magnetic transitions in orthorhombic perovskites

We present a temperature dependent single crystal x-ray diffraction study of twinned orthorhombic perovskites La1-xCaxMnO3, for x=0.16 and x=0.25. These data show the evolution of the crystal structure from the ferromagnetic insulating state to the ferromagnetic metallic state. The data are modelled in space group Pnma with twin relations based on a distribution of the b axis over three perpendicular cubic axes. The twin model allows full structure determination in the presence of up to six twin fractions using the single crystal x-ray diffraction data.Comment: 13 pages, including 13 figures and 2 table

Evidence for a Low-Spin to Intermediate-Spin State Transition in LaCoO3

We present measurements of the magnetic susceptibility and of the thermal expansion of a LaCoO$_3$ single crystal. Both quantities show a strongly anomalous temperature dependence. Our data are consistently described in terms of a spin-state transition of the Co$^{3+}$ ions with increasing temperature from a low-spin ground state to an intermediate-spin state without (100K - 500K) and with (>500K) orbital degeneracy. We attribute the lack of orbital degeneracy up to 500K to (probably local) Jahn-Teller distortions of the CoO$_6$ octahedra. A strong reduction or disappearance of the Jahn-Teller distortions seems to arise from the insulator-to-metal transition around 500 K.Comment: an error in the scaling factor of Eq.(4) and consequently 2 values of table I have been corrected. The conclusions of the paper remain unchanged. See also: C. Zobel et al. Phys. Rev. B 71, 019902 (2005) and J. Baier et al. Phys. Rev. B 71, 014443 (2005

Magnetic hyperthermia experiments with magnetic nanoparticles in clarified butter oil and paraffin: A thermodynamic analysis

In specific power absorption models for magnetic fluid hyperthermia (MFH) experiments, the magnetic relaxation time of nanoparticles (NPs) is known to be a fundamental descriptor of the heating mechanisms. The relaxation time is mainly determined by the interplay between the magnetic properties of NPs and the rheological properties of NPs’ environment. Although the role of magnetism in MFH has been extensively studied, the thermal properties of the NP medium and their changes during MFH experiments have been underrated so far. Herein, we show that ZnxFe3-xO4 NPs dispersed through different media with phase transition in the temperature range of experiment as clarified butter oil (CBO) and paraffin. These systems show nonlinear behavior of the heating rate within the temperature range of MFH experiments. For CBO, a fast increase at ~306 K is associated with changes in the viscosity (¿(T)) and specific heat (cp(T)) of the medium at its melting temperature. This increment in the heating rate takes place around 318 K for paraffin. The magnetic and morphological characterization of NPs together with the observed agglomeration of NPs above 306 and 318 K for CBO and paraffin, respectively, indicate that the fast increase in MFH curves could not be associated with the change in the magnetic relaxation mechanism, with Neél relaxation being dominant. In fact, successive experimental runs performed up to temperatures below and above the CBO and paraffin melting points resulted in different MFH curves due to agglomeration of NPs driven by magnetic field inhomogeneity during the experiments. Our results highlight the relevance of the thermodynamic properties of the system NP-medium for an accurate measurement of the heating efficiency for in vitro and in vivo environments, where the thermal properties are largely variable within the temperature window of MFH experiments

Effects of Zn Substitution in the Magnetic and Morphological Properties of Fe-Oxide-Based Core-Shell Nanoparticles Produced in a Single Chemical Synthesis

Magnetic, compositional, and morphological properties of Zn-Fe-oxide core-shell bimagnetic nanoparticles were studied for three samples with 0.00, 0.06, and 0.10 Zn/Fe ratios, as obtained from particle-induced X-ray emission analysis. The bimagnetic nanoparticles were produced in a one-step synthesis by the thermal decomposition of the respective acetylacetonates. The nanoparticles present an average particle size between 25 and 30 nm as inferred from transmission electron microscopy (TEM). High-resolution TEM images clearly show core-shell morphology for the particles in all samples. The core is composed by an antiferromagnetic (AFM) phase with a Wüstite (Fe1-yO) structure, whereas the shell is composed by a ZnxFe3-xO4 ferrimagnetic (FiM) spinel phase. Despite the low solubility of Zn in the Wüstite, electron energy-loss spectroscopy analysis indicates that Zn is distributed almost homogeneously in the whole nanoparticle. This result gives information on the formation mechanisms of the particle, indicating that the Wüstite is formed first, and the superficial oxidation results in the FiM ferrite phase with similar Zn concentration than the core. Magnetization and in-field Mössbauer spectroscopy of the Zn-richest nanoparticles indicate that the AFM phase is strongly coupled to the FiM structure of the ferrite shell, resulting in a bias field (HEB) appearing below TNFeO, with HEB values that depend on the core-shell relative proportion. Magnetic characterization also indicates a strong magnetic frustration for the samples with higher Zn concentration, even at low temperatures

Controller-observer design and dynamic parameter identification for model-based control of an electromechanical lower-limb rehabilitation system

[EN] Rehabilitation is a hazardous task for a mechanical system, since the device has to interact with the human extremities without the hands-on experience the physiotherapist acquires over time. A gap needs to be filled in terms of designing effective controllers for this type of devices. In this respect, the paper describes the design of a model-based control for an electromechanical lower-limb rehabilitation system based on a parallel kinematic mechanism. A controller-observer was designed for estimating joint velocities, which are then used in a hybrid position/force control scheme. The model parameters are identified by customising an approach based on identifying only the relevant system dynamics parameters. Findings obtained through simulations show evidence of improvement in tracking performance compared with those where the velocity was estimated by numerical differentiation. The controller is also implemented in an actual electromechanical system for lower-limb rehabilitation tasks. Findings based on rehabilitation tasks confirm the findings from simulations.This work was partially financed by the Plan Nacional de I+D, Comision Interministerial de Ciencia y Tecnologia (FEDERCICYT) under the project DPI2013-44227-R and by the Instituto U. de Automatica e Informatica Industrial (ai2) of the Universitat Politecnica de Valencia.Valera Fernández, Á.; Díaz-Rodríguez, M.; Vallés Miquel, M.; Oliver, E.; Mata Amela, V.; Page Del Pozo, AF. (2017). Controller-observer design and dynamic parameter identification for model-based control of an electromechanical lower-limb rehabilitation system. International Journal of Control. 90(4):702-714. https://doi.org/10.1080/00207179.2016.1215529S702714904Åström, K. J., & Murray, R. M. (2010). Feedback Systems. doi:10.2307/j.ctvcm4gdkAtkeson, C. G., An, C. H., & Hollerbach, J. M. (1986). 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IEEE Transactions on Automatic Control, 36(12), 1497-1501. doi:10.1109/9.106170Canudas de Wit, C., & Slotine, J.-J. E. (1991). Sliding observers for robot manipulators. Automatica, 27(5), 859-864. doi:10.1016/0005-1098(91)90041-yCao, J., Xie, S. Q., Das, R., & Zhu, G. L. (2014). Control strategies for effective robot assisted gait rehabilitation: The state of art and future prospects. Medical Engineering & Physics, 36(12), 1555-1566. doi:10.1016/j.medengphy.2014.08.005Carretero, J. A., Podhorodeski, R. P., Nahon, M. A., & Gosselin, C. M. (1999). Kinematic Analysis and Optimization of a New Three Degree-of-Freedom Spatial Parallel Manipulator. Journal of Mechanical Design, 122(1), 17-24. doi:10.1115/1.533542Cazalilla, J., Vallés, M., Mata, V., Díaz-Rodríguez, M., & Valera, A. (2014). Adaptive control of a 3-DOF parallel manipulator considering payload handling and relevant parameter models. Robotics and Computer-Integrated Manufacturing, 30(5), 468-477. doi:10.1016/j.rcim.2014.02.003De Jalon, J.G. & Bayo, E. (1994). Kinematic and dynamic simulation of multibody systems: the real-time challenge. New York: Springer Verlag.Díaz, I., Gil, J. J., & Sánchez, E. (2011). Lower-Limb Robotic Rehabilitation: Literature Review and Challenges. Journal of Robotics, 2011, 1-11. doi:10.1155/2011/759764Díaz-Rodríguez, M., Iriarte, X., Mata, V., & Ros, J. (2009). On the Experiment Design for Direct Dynamic Parameter Identification of Parallel Robots. Advanced Robotics, 23(3), 329-348. doi:10.1163/156855308x397550Díaz-Rodríguez, M., Mata, V., Valera, Á., & Page, Á. (2010). A methodology for dynamic parameters identification of 3-DOF parallel robots in terms of relevant parameters. Mechanism and Machine Theory, 45(9), 1337-1356. doi:10.1016/j.mechmachtheory.2010.04.007Gautier, M. (1991). Numerical calculation of the base inertial parameters of robots. Journal of Robotic Systems, 8(4), 485-506. doi:10.1002/rob.4620080405Gautier, M., & Khalil, W. (s. f.). On the identification of the inertial parameters of robots. Proceedings of the 27th IEEE Conference on Decision and Control. doi:10.1109/cdc.1988.194738Jamwal, P. K., Hussain, S., & Xie, S. Q. (2013). Review on design and control aspects of ankle rehabilitation robots. Disability and Rehabilitation: Assistive Technology, 10(2), 93-101. doi:10.3109/17483107.2013.866986Janabi-Sharifi, F., Hayward, V., & Chen, C.-S. J. (2000). Discrete-time adaptive windowing for velocity estimation. IEEE Transactions on Control Systems Technology, 8(6), 1003-1009. doi:10.1109/87.880606Janot, A., Gautier, M., Jubien, A., & Vandanjon, P. O. (2014). Comparison Between the CLOE Method and the DIDIM Method for Robots Identification. IEEE Transactions on Control Systems Technology, 22(5), 1935-1941. doi:10.1109/tcst.2014.2299544Janot, A., Vandanjon, P.-O., & Gautier, M. (2016). A revised Durbin-Wu-Hausman test for industrial robot identification. Control Engineering Practice, 48, 52-62. doi:10.1016/j.conengprac.2015.12.017Jiménez-Fabián, R., & Verlinden, O. (2012). Review of control algorithms for robotic ankle systems in lower-limb orthoses, prostheses, and exoskeletons. Medical Engineering & Physics, 34(4), 397-408. doi:10.1016/j.medengphy.2011.11.018Khalil, W., Vijayalingam, A., Khomutenko, B., Mukhanov, I., Lemoine, P., & Ecorchard, G. (2014). OpenSYMORO: An open-source software package for symbolic modelling of robots. 2014 IEEE/ASME International Conference on Advanced Intelligent Mechatronics. doi:10.1109/aim.2014.6878246Marchal-Crespo, L., & Reinkensmeyer, D. J. (2009). Review of control strategies for robotic movement training after neurologic injury. Journal of NeuroEngineering and Rehabilitation, 6(1). doi:10.1186/1743-0003-6-20Meng, W., Liu, Q., Zhou, Z., Ai, Q., Sheng, B., & Xie, S. (Shane). (2015). Recent development of mechanisms and control strategies for robot-assisted lower limb rehabilitation. Mechatronics, 31, 132-145. doi:10.1016/j.mechatronics.2015.04.005Page, A., Candelas, P., & Belmar, F. (2006). On the use of local fitting techniques for the analysis of physical dynamic systems. European Journal of Physics, 27(2), 273-279. doi:10.1088/0143-0807/27/2/010Raibert, M. H., & Craig, J. J. (1981). Hybrid Position/Force Control of Manipulators. Journal of Dynamic Systems, Measurement, and Control, 103(2), 126-133. doi:10.1115/1.3139652Ramsay, J. O., & Silverman, B. W. (2005). Functional Data Analysis. Springer Series in Statistics. doi:10.1007/b98888Saglia, J. A., Tsagarakis, N. G., Dai, J. S., & Caldwell, D. G. (2013). Control Strategies for Patient-Assisted Training Using the Ankle Rehabilitation Robot (ARBOT). 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The Physics of turbulent and dynamically unstable Herbig-Haro jets

The overall properties of the Herbig-Haro objects such as centerline velocity, transversal profile of velocity, flow of mass and energy are explained adopting two models for the turbulent jet. The complex shapes of the Herbig-Haro objects, such as the arc in HH34 can be explained introducing the combination of different kinematic effects such as velocity behavior along the main direction of the jet and the velocity of the star in the interstellar medium. The behavior of the intensity or brightness of the line of emission is explored in three different cases : transversal 1D cut, longitudinal 1D cut and 2D map. An analytical explanation for the enhancement in intensity or brightness such as usually modeled by the bow shock is given by a careful analysis of the geometrical properties of the torus.Comment: 17 pages, 10 figures. Accepted for publication in Astrophysics & Spac

Limits to the muon flux from WIMP annihilation in the center of the Earth with the AMANDA detector

A search for nearly vertical up-going muon-neutrinos from neutralino annihilations in the center of the Earth has been performed with the AMANDA-B10 neutrino detector. The data sample collected in 130.1 days of live-time in 1997, ~10^9 events, has been analyzed for this search. No excess over the expected atmospheric neutrino background is oberved. An upper limit at 90% confidence level on the annihilation rate of neutralinos in the center of the Earth is obtained as a function of the neutralino mass in the range 100 GeV-5000 GeV, as well as the corresponding muon flux limit.Comment: 14 pages, 11 figures. Version accepted for publication in Physical Review

Tratamiento de regeneración endodóntica en pulpa vital y necrótica, utilizando fibrina rica en plaquetas y Biodentine: reporte de caso

Endodontic regeneration is an inductive and reparative biological treatment indicated to replace cell damage at the level of the dentinopulp complex. The objective of this study is to report a case of Endodontic Regenerative Therapy, in young permanent first molars, in a 10-year-old patient, using platelet-rich fibrin and Biodentine, applying two different protocols for combined diagnoses of irreversible pulpitis and pulp necrosis. The patient attended consultation due to extensive carious lesions. Clinical and imaging evaluations (X-rays and Cone Beam) were performed. The protocol in the necrotic canal consisted of disinfection with a bi-antibiotic paste and placement of a second-generation autologous scaffold matrix, made of biodegradable platelet-rich fibrin which is also , biocompatible and therefore without risk of immune rejection. The protocol in the canals with irreversible pulpitis consisted in a complete pulpotomy and placement of Biodentine calcium silicate cement, a material considered as first choice for pulp-conserving treatments, with properties similar to dentin. Eight weeks after the end of the treatment, a clinical control was conducted revealing an asymptomatic chart and negative palpation without the presence of fistula or abscess. This result indicated regeneration of the pulp tissues and success of the applied protocols. Controls will be carried out at 6, 12 and 18 months. Conclusion: The application of endodontic regenerative treatments, as performed in this reported case, is a favorable and innovative option to preserve, restore or replace the dental pulp. In comparison with conventional treatments, this procedure allows to return pulp functionality, complete development of the root, thickening of the dentinal walls and closure of the apical foramen of young permanent teeth affected by pulp pathologies. It is important that regenerative therapies are publicized and applied by dental professionalsLa regeneración endodóntica es un tratamiento inductivo y reparativo con bases biológicas, indicado para reemplazar los daños celulares a nivel del complejo dentinopulpar. El objetivo de este estudio es reportar un caso de Terapia Regenerativa Endodóntica, en primeros molares permanentes jóvenes, en un paciente de 10 años, a través del uso de fibrina rica en plaquetas y Biodentine, se aplicaron dos protocolos diferentes por diagnósticos combinados de pulpitis irreversible y necrosis pulpar. El paciente acude a consulta por presentar lesiones cariosas extensas; se realizaron evaluaciones clínicas e imagenológicas (radiografías y Cone Beam), el protocolo en el conducto necrótico consistió en la desinfección con pasta biantibiótica y la colocación de una matriz de andamiaje autóloga de segunda generación, elaborada de fibrina rica en plaquetas que es biodegradable, biocompatible y no existe riesgo de rechazo inmunológico. El protocolo en los conductos con pulpitis irreversibles consistió en pulpotomía total y colocación de cemento de silicato de calcio Biodentine, el cual se considera el material de primera elección para los tratamientos conservadores de la pulpa, con propiedades similares a la dentina. A 8 semanas de finalizado el tratamiento se realizó control clínico y el paciente mostró un cuadro asintomático, palpación negativa sin presencia de fístula o absceso lo que podría indicar regeneración de los tejidos pulpares y éxito de los protocolos aplicados. Los siguientes controles se realizán a los 6, 12 y 18 meses. Conclusión: la aplicación de los tratamientos regenerativos endodónticos como se realizó en el caso reportado, es una opción favorable e innovadora para preservar, restaurar o sustituir la pulpa dental, que en comparación con los tratamientos convencionales nos permiten devolver la funcionalidad pulpar, finalizar el desarrollo radicular, engrosamiento de las paredes dentinales y cierre del foramen apical de dientes permanentes jóvenes que han sido afectados por patologías pulpares. Es importante que las terapias regenerativas sean divulgadas y aplicadas por los profesionale

Mixed marriages and transnational families in the intercultural context : a case study of African-Spanish couples in Catalonia, Spain

Premi a l'excel·lència investigadora. Àmbit de les Ciències Socials. 2008One of the consequences of international migration and the permanent settlement of immigrants in southern EU countries is the growing number of inter-country marriages and the formation of transnational families. Using both quantitative and qualitative data, this article examines patterns of endogamy and exogamy (i.e. marriage within/outside a particular group or category) among African immigrants in Catalonia, focusing on bi-national Senegalese- and Gambian-Spanish couples. Socio-demographic profiles, transnationality, the dynamics of cultural change or retention, and the formation of transcultural identities are explored. The evidence presented suggests that social-class factors are more important than cultural origins in patterns of endogamy and exogamy, in the dynamics of living together and in the bringing-up of children of mixed unions. Such a conclusion negates culturalists' explanations of endogamy and exogamy while, at the same time, emphasising the role of social actors as active subjects in these processes. I further argue that mixed couples and their offspring deal-to a greater or lesser extent-with multiple localisations and cultural backgrounds (i.e. here and there), rather than experiencing a 'clash between two cultures'. Therefore, it would be a mistake to pretend that multicultural links do not exist and that they cannot be revitalised and functional. The paper starts and ends by addressing the complexities of processes of interculturalism, resisting an interpretation of hybridity and segregation as contradictory or exclusive realities