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Pesquera D, Scigaj M, Gargiani P, Barla A, Herrero-Martín J, Pellegrin E, Valvidares SM, Gázquez J, Varela M, Dix N, Fontcuberta J, Sánchez F, Herranz G. Two-dimensional electron gases at LaAlO3/SrTiO3 interfaces: orbital symmetry and hierarchy engineered by crystal orientation. PHYSICAL REVIEW LETTERS 2014; 113:156802. [PMID: 25375731 DOI: 10.1103/physrevlett.113.156802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Indexed: 06/04/2023]
Abstract
Recent findings show the emergence of two-dimensional electron gases (2DEGs) at LaAlO(3)/SrTiO(3) interfaces along different orientations; yet details on band reconstructions have remained so far unknown. Via x-ray linear dichroism spectroscopy, we demonstrate that crystal symmetry imposes distinctive 2DEG orbital hierarchies on (001)-and (110)-oriented quantum wells, allowing selective occupancy of states of different symmetry. Such orientational tuning expands the possibilities for electronic engineering of 2DEGs and opens up enticing opportunities to understand the link between orbital symmetry and complex correlated states at LaAlO(3)/SrTiO(3) quantum wells.
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Varela M, García-Camba P, Gutiérrez Mosquera B, García Rosas S, Lorda I. Desarrollo tardío de múltiples dientes supernumerarios en una paciente con miastenia gravis juvenil tratada con azatioprina. An Pediatr (Barc) 2014; 81:200-1. [DOI: 10.1016/j.anpedi.2013.10.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 10/31/2013] [Indexed: 10/25/2022] Open
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Seehusen F, Hahn K, Herder V, Weigand M, Habierski A, Gerhauser I, Wohlsein P, Peters M, Varela M, Palmarini M, Baumgärtner W. Skeletal Muscle Hypoplasia Represents the Only Significant Lesion in Peripheral Organs of Ruminants Infected with Schmallenberg Virus during Gestation. J Comp Pathol 2014; 151:148-52. [DOI: 10.1016/j.jcpa.2014.04.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/06/2014] [Accepted: 04/14/2014] [Indexed: 11/26/2022]
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Estrader M, López-Ortega A, Estradé S, Golosovsky IV, Salazar-Alvarez G, Vasilakaki M, Trohidou KN, Varela M, Stanley DC, Sinko M, Pechan MJ, Keavney DJ, Peiró F, Suriñach S, Baró MD, Nogués J. Robust antiferromagnetic coupling in hard-soft bi-magnetic core/shell nanoparticles. Nat Commun 2014; 4:2960. [PMID: 24343382 DOI: 10.1038/ncomms3960] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 11/19/2013] [Indexed: 11/10/2022] Open
Abstract
The growing miniaturization demand of magnetic devices is fuelling the recent interest in bi-magnetic nanoparticles as ultimate small components. One of the main goals has been to reproduce practical magnetic properties observed so far in layered systems. In this context, although useful effects such as exchange bias or spring magnets have been demonstrated in core/shell nanoparticles, other interesting key properties for devices remain elusive. Here we show a robust antiferromagnetic (AFM) coupling in core/shell nanoparticles which, in turn, leads to the foremost elucidation of positive exchange bias in bi-magnetic hard-soft systems and the remarkable regulation of the resonance field and amplitude. The AFM coupling in iron oxide-manganese oxide based, soft/hard and hard/soft, core/shell nanoparticles is demonstrated by magnetometry, ferromagnetic resonance and X-ray magnetic circular dichroism. Monte Carlo simulations prove the consistency of the AFM coupling. This unique coupling could give rise to more advanced applications of bi-magnetic core/shell nanoparticles.
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Cuellar FA, Liu YH, Salafranca J, Nemes N, Iborra E, Sanchez-Santolino G, Varela M, Garcia Hernandez M, Freeland JW, Zhernenkov M, Fitzsimmons MR, Okamoto S, Pennycook SJ, Bibes M, Barthélémy A, te Velthuis SGE, Sefrioui Z, Leon C, Santamaria J. Reversible electric-field control of magnetization at oxide interfaces. Nat Commun 2014; 5:4215. [PMID: 24953219 DOI: 10.1038/ncomms5215] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 05/27/2014] [Indexed: 11/09/2022] Open
Abstract
Electric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field.
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Radaelli G, Petti D, Plekhanov E, Fina I, Torelli P, Salles BR, Cantoni M, Rinaldi C, Gutiérrez D, Panaccione G, Varela M, Picozzi S, Fontcuberta J, Bertacco R. Electric control of magnetism at the Fe/BaTiO₃ interface. Nat Commun 2014; 5:3404. [PMID: 24584546 PMCID: PMC3942656 DOI: 10.1038/ncomms4404] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 02/07/2014] [Indexed: 11/30/2022] Open
Abstract
Interfacial magnetoelectric coupling is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO3 system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BaTiO3 dielectric polarization have been predicted so far. Here, by using X-ray magnetic circular dichroism in combination with high resolution electron microscopy and first principles calculations, we report on an undisclosed physical mechanism for interfacial magnetoelectric coupling in the Fe/BaTiO3 system. At this interface, an ultrathin oxidized iron layer exists, whose magnetization can be electrically and reversibly switched on-off at room-temperature by reversing the BaTiO3 polarization. The suppression / recovery of interfacial ferromagnetism results from the asymmetric effect that ionic displacements in BaTiO3 produces on the exchange coupling constants in the interfacial oxidized Fe layer. The observed giant magnetoelectric response holds potential for optimizing interfacial magnetoelectric coupling in view of efficient, low-power spintronic devices.
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Varela M, Colman M, Zhang H, Aslanidi O. Realistic heterogeneous and anisotropic canine atrial model for the study of atrial arrhythmias. J Electrocardiol 2013. [DOI: 10.1016/j.jelectrocard.2013.05.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Fioretti C, Galán A, Moine R, Varela M, Varela P, Mouguelar H, Gigena S, Bonino F, Quinteros R, Natali J. Características Mecánicas Dinámicas de la Tibia Aislada de Perro Sometida a Prueba de Impacto. INT J MORPHOL 2013. [DOI: 10.4067/s0717-95022013000200033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Sánchez-Santolino G, Tornos J, Bruno F, Cuellar F, Leon C, Santamaría J, Pennycook S, Varela M. Characterization of surface metallic states in SrTiO3 by means of aberration corrected electron microscopy. Ultramicroscopy 2013; 127:109-13. [DOI: 10.1016/j.ultramic.2012.07.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Prange MP, Oxley MP, Varela M, Pennycook SJ, Pantelides ST. Simulation of spatially resolved electron energy loss near-edge structure for scanning transmission electron microscopy. PHYSICAL REVIEW LETTERS 2012; 109:246101. [PMID: 23368348 DOI: 10.1103/physrevlett.109.246101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 11/09/2012] [Indexed: 06/01/2023]
Abstract
Aberration-corrected scanning transmission electron microscopy yields probe-position-dependent energy-loss near-edge structure (ELNES) measurements, potentially providing spatial mapping of the underlying electronic states. ELNES calculations, however, typically describe excitations by a plane wave traveling in vacuum, neglecting the interaction of the electron probe with the local electronic environment as it propagates through the specimen. Here, we report a methodology that combines a full electronic-structure calculation with propagation of a focused beam in a thin film. The results demonstrate that only a detailed calculation using this approach can provide quantitative agreement with observed variations in probe-position-dependent ELNES.
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García-Hoyos F, Barbería E, García-Camba P, Varela M. Renal fluoride excretion in children following topical application of fluoride varnish. EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 2012; 13:280-284. [PMID: 23270283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
AIM To demonstrate that the application of dental fluoride varnishes in children increases urinary fluoride excretion. MATERIALS AND METHODS From a randomly assembled group of 42 children aged between 5 and 8 years, residing in a community with non-fluoridated water, spot urinary samples were taken before the topical application of dental fluoride varnish and 2 hours afterwards. In an age-matched control group of 16 children from the same community, who received no treatment, samples were taken the same way. The urinary excretion of fluoride was analysed by determining fluoride ion (F-) level and fluoride/creatinine (F/Cr) ratio in the urine. RESULTS In the study group, the average pre- and post-treatment F/Cr ratios were 0.42 and 1.38 mg/g, respectively (p < .001). No significant changes were observed in the control group, which received no treatment. The average 2 hours afterward F/Cr ratios were 0.29 and 0.27 respectively (p = 0.426). CONCLUSION The topical application of dental fluoride varnish leads to a significant increase in urine F-, which is attributable to the application of the product.
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Varela M, Dios S, Novoa B, Figueras A. Characterisation, expression and ontogeny of interleukin-6 and its receptors in zebrafish (Danio rerio). DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2012; 37:97-106. [PMID: 22107841 DOI: 10.1016/j.dci.2011.11.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Revised: 10/28/2011] [Accepted: 11/04/2011] [Indexed: 05/31/2023]
Abstract
Interleukin-6 (IL-6) is one of the most pleiotropic cytokines due to its importance in both innate and adaptive immune responses and other physiological processes. In this study, we identified the zebrafish (Danio rerio) IL-6 homologue by investigating the synteny between the human (Homo sapiens), the fugu (Takifugu rubripes) and the zebrafish genome. Although zebrafish IL-6 showed a low sequence homology with other IL-6 sequences in other species, it presented a high structural similarity to human IL-6. We also analysed IL-6 expression in several different tissues, along with analysis of the expression of the genes that form the IL-6 receptor complex, IL-6R and gp130. After treatment with bacterial or viral stimuli, zebrafish IL-6 expression was modulated in a manner similar to that of other proinflammatory molecules, such as IL-1β and TNF-α. The expression of IL-6, IL-6R and gp130 was also studied during the ontogeny of zebrafish larvae using quantitative PCR and in situ hybridisation. Our results indicated that the transcripts were detected very early, increased during the first week of life and were predominantly expressed in the head, epidermis and neuromasts of the anterior and posterior lateral line system, suggesting their involvement in the normal development of these tissues.
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Singh S, Fitzsimmons MR, Lookman T, Thompson JD, Jeen H, Biswas A, Roldan MA, Varela M. Magnetic nonuniformity and thermal hysteresis of magnetism in a manganite thin film. PHYSICAL REVIEW LETTERS 2012; 108:077207. [PMID: 22401251 DOI: 10.1103/physrevlett.108.077207] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 12/14/2011] [Indexed: 05/31/2023]
Abstract
We measured the chemical and magnetic depth profiles of a single crystalline (La(1-x)Pr(x))(1-y)Ca(y)MnO(3-δ) (x=0.52±0.05, y=0.23±0.04, δ=0.14±0.10) film grown on a NdGaO(3) substrate using x-ray reflectometry, electron microscopy, electron energy-loss spectroscopy, and polarized neutron reflectometry. Our data indicate that the film exhibits coexistence of different magnetic phases as a function of depth. The magnetic depth profile is correlated with a variation of chemical composition with depth. The thermal hysteresis of ferromagnetic order in the film suggests a first-order ferromagnetic transition at low temperatures.
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Llordés A, Palau A, Gázquez J, Coll M, Vlad R, Pomar A, Arbiol J, Guzmán R, Ye S, Rouco V, Sandiumenge F, Ricart S, Puig T, Varela M, Chateigner D, Vanacken J, Gutiérrez J, Moshchalkov V, Deutscher G, Magen C, Obradors X. Nanoscale strain-induced pair suppression as a vortex-pinning mechanism in high-temperature superconductors. NATURE MATERIALS 2012; 11:329-336. [PMID: 22327747 DOI: 10.1038/nmat3247] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 01/11/2012] [Indexed: 05/31/2023]
Abstract
Boosting large-scale superconductor applications require nanostructured conductors with artificial pinning centres immobilizing quantized vortices at high temperature and magnetic fields. Here we demonstrate a highly effective mechanism of artificial pinning centres in solution-derived high-temperature superconductor nanocomposites through generation of nanostrained regions where Cooper pair formation is suppressed. The nanostrained regions identified from transmission electron microscopy devise a very high concentration of partial dislocations associated with intergrowths generated between the randomly oriented nanodots and the epitaxial YBa(2)Cu(3)O(7) matrix. Consequently, an outstanding vortex-pinning enhancement correlated to the nanostrain is demonstrated for four types of randomly oriented nanodot, and a unique evolution towards an isotropic vortex-pinning behaviour, even in the effective anisotropy, is achieved as the nanostrain turns isotropic. We suggest a new vortex-pinning mechanism based on the bond-contraction pairing model, where pair formation is quenched under tensile strain, forming new and effective core-pinning regions.
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Varela M, Trujillo-Tiebas MJ, Garcia-Camba P. Case report: identical twins revealing discordant hypodontia. The rationale of dental arch differences in monozygotic twins. Eur Arch Paediatr Dent 2012; 12:318-22. [PMID: 22122852 DOI: 10.1007/bf03262831] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND While it is generally accepted that monozygotic (MZ) twins are identical with respect to inherited traits, because they share 100% of their genetic material, clinical findings and scientific evidence does not support this belief. In addition to environmental factors and stochastic developmental events, a number of genetic mechanisms, detectable by new techniques in molecular genetics, explain the differences frequently observed in MZ twins. CASE REPORT Nine-year-old twin girls requested treatment for a dental malocclusion. Their facial and occlusal features were very similar. Panoramic radiographs revealed hypodontia of two permanent teeth in one twin (35 and 45) and of only one tooth in the other (45). An incorrect diagnosis of dizygosity (DZ) had been made at birth based on the presence of two amniotic sacs. Despite discordance in the dental complement of both girls their orthodontist suspected that the twins might be identical. A genetic study performed by quantitative fluorescence-polymerase chain reaction (QFPCR) analysis of chromosomes 13, 15, 16, 18, 21, 22, and X confirmed that the twins were MZ. CONCLUSION Discordances in dental complement between MZ twins are not uncommon and do not exclude monozygosity.
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Vilar M, Rodríguez-Otero J, Sanjuán M, Diéguez F, Varela M, Yus E. Implementation of HACCP to control the influence of milking equipment and cooling tank on the milk quality. Trends Food Sci Technol 2012. [DOI: 10.1016/j.tifs.2011.08.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Varela M, Ruiz-Esteban R, Martinez-Nicolas A, Cuervo-Arango JA, Barros C, Delgado EG. 'Catching the spike and tracking the flow': Holter-temperature monitoring in patients admitted in a general internal medicine ward. Int J Clin Pract 2011; 65:1283-8. [PMID: 22093535 DOI: 10.1111/j.1742-1241.2011.02794.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
OBJECTIVE To study if a 24-h continuous monitoring of temperature reveals information not accessible through conventional care. This included omitted fever peaks and circadian and complexity characteristics that may correlate with specific aetiologies. DESIGN Ours was a prospective, observational study. A total of 62 patients, admitted to a general internal medicine ward, in whom a temperature > 38 °C had been observed the day before inclusion underwent a 24-h long continuous monitoring of both central and peripheral temperatures. The time series were recorded in a file, while they otherwise followed conventional care. Time series were analysed for standard statistics, chronobiological analysis (amplitude, mesor, acrophase, intra-daily variability) and complexity analysis (Approximate Entropy of both central and peripheral temperature, cross-ApEn). A month after discharge, the clinical reports were reviewed and a definitive diagnosis of the febrile syndrome was established. RESULTS A total of 62 patients were initially included. In six cases, no time series could be obtained because of technical problems, leaving 56 patients accessible for analysis. In 10 cases, no definitive diagnosis was established. Continuous monitoring detected a mean of 0.7 (CI = 0.27-1.33) peaks of fever (central temperature > 38.0 °C) unobserved by conventional care per patient. A proportion of 16% (CI = 6-26) of patients considered afebrile by conventional care had at least one fever peak detected by continuous monitoring. Circadian rhythm persisted or was exacerbated in febrile patients. Circadian amplitude was increased in patients with tuberculosis. Complexity analysis did not differ among different diagnostic groups, although in subgroup analysis, viral infections had a higher complexity than other infectious diseases. CONCLUSIONS Temperature Holter monitoring reveals fever peaks that pass otherwise unobserved. Furthermore, chronobiological and complexity analysis of the temperature profile may provide quick and easy 'hidden information', not available to conventional care.
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Rivera-Calzada A, Diaz-Guillen MR, Dura OJ, Sanchez-Santolino G, Pennycook TJ, Schmidt R, Bruno FY, Garcia- Barriocanal J, Sefrioui Z, Nemes NM, Garcia-Hernandez M, Varela M, Leon C, Pantelides ST, Pennycook SJ, Santamaria J. Tailoring interface structure in highly strained YSZ/STO heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2011; 23:5268-5274. [PMID: 22299141 DOI: 10.1002/adma.201102106] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Chakhalian J, Rondinelli JM, Liu J, Gray BA, Kareev M, Moon EJ, Prasai N, Cohn JL, Varela M, Tung IC, Bedzyk MJ, Altendorf SG, Strigari F, Dabrowski B, Tjeng LH, Ryan PJ, Freeland JW. Asymmetric orbital-lattice interactions in ultrathin correlated oxide films. PHYSICAL REVIEW LETTERS 2011; 107:116805. [PMID: 22026694 DOI: 10.1103/physrevlett.107.116805] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Indexed: 05/23/2023]
Abstract
Using resonant x-ray spectroscopies combined with density functional calculations, we find an asymmetric biaxial strain-induced d-orbital response in ultrathin films of the correlated metal LaNiO3 which are not accessible in the bulk. The sign of the misfit strain governs the stability of an octahedral "breathing" distortion, which, in turn, produces an emergent charge-ordered ground state with an altered ligand-hole density and bond covalency. Control of this new mechanism opens a pathway to rational orbital engineering, providing a platform for artificially designed Mott materials.
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Fioretti C, Natali J, Galán A, Rivera MC, Moine R, Varela P, Varela M, Bonino F, Quinteros R. Características Mecánicas Dinámicas del Fémur Aislado de Perro, Sometido a Prueba de Impacto. INT J MORPHOL 2011. [DOI: 10.4067/s0717-95022011000300009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Kreisel J, Jadhav P, Chaix-Pluchery O, Varela M, Dix N, Sánchez F, Fontcuberta J. A phase transition close to room temperature in BiFeO3 thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:342202. [PMID: 21841238 DOI: 10.1088/0953-8984/23/34/342202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BiFeO3 (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 °C, and thus close to room temperature.
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Pennycook SJ, Varela M. New views of materials through aberration-corrected scanning transmission electron microscopy. Microscopy (Oxf) 2011; 60 Suppl 1:S213-23. [DOI: 10.1093/jmicro/dfr030] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Bruno FY, Garcia-Barriocanal J, Varela M, Nemes NM, Thakur P, Cezar JC, Brookes NB, Rivera-Calzada A, Garcia-Hernandez M, Leon C, Okamoto S, Pennycook SJ, Santamaria J. Electronic and magnetic reconstructions in La0.7Sr0.3MnO3/SrTiO3 heterostructures: a case of enhanced interlayer coupling controlled by the interface. PHYSICAL REVIEW LETTERS 2011; 106:147205. [PMID: 21561220 DOI: 10.1103/physrevlett.106.147205] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Indexed: 05/30/2023]
Abstract
We report on the magnetic coupling of La0.7Sr0.3MnO3 layers through SrTiO3 spacers in La0.7Sr0.3MnO3/SrTiO3 epitaxial heterostructures. Combined aberration-corrected microscopy and electron-energy-loss spectroscopy evidence charge transfer to the empty conduction band of the titanate. Ti d electrons interact via superexchange with Mn, giving rise to a Ti magnetic moment as demonstrated by x-ray magnetic circular dichroism. This induced magnetic moment in the SrTiO3 controls the bulk magnetic and transport properties of the superlattices when the titanate layer thickness is below 1 nm.
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Sala R, Dodyk P, Varela M, Lerzo G, Blajman C, Zarba J, Lacava J, Alvarez A, Richardet E, Fein L. P280 Identification of factors associated with the participation in an adjuvant treatment clinical study for patients with breast cancer. Breast 2011. [DOI: 10.1016/s0960-9776(11)70222-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Pennycook S, Lupini AR, Varela M, Borisevich A, Chisholm MF, Abe E, Dellby N, Krivanek O, Nellist PD, Wang LG, Buczko R, Fan X, Pantelides ST. Nanoscale Structure/Property Correlation Through Aberration-Corrected Stem And Theory. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-738-g1.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The combination of atomic-resolution Z-contrast microscopy, electron energy loss spectroscopy and first-principles theory has proved to be a powerful means for structure property correlations at interfaces and nanostructures. The scanning transmission electron microscope (STEM) now routinely provides atomic-sized electron beams, allowing simultaneous Z-contrast imaging and EELS as shown in Fig. 1. The feasiblity of correcting the inherently large spherical aberration of microscope objective lenses promises to at least double the achievable resolution. The potential benefits for the STEM, however, may turn out to be much greater than those for the conventional TEM because it is very much less sensitive to chromatic instabilities. The 100 kV VG Microscopes HB501UX at Oak Ridge National Laboratory (ORNL) is now fitted with an aberration corrector constructed by Nion Co., which improved its resolution from 2.2 Å (full-width-half-maximum probe intensity) to around 1.3 Å. It is now very comparable in performance to the uncorrected 300 kV HB603U STEM at ORNL which, before correction, also had a directly interpretable resolution of 1.3 Å, although information transfer had been demonstrated down to 0.78 Å8. Initial results after installing an aberration corrector on the 300 kV STEM indicate a resolution of 0.84 Å. The theoretically achievable probe size in the absence of instabilities is predicted to be 0.5 Å.
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