3D magnetic induction maps of nanoscale materials revealed by electron holographic tomography

This is an open access article published under a Creative Commons Attribution (CC-BY) License.-- et al.The investigation of three-dimensional (3D) ferromagnetic nanoscale materials constitutes one of the key research areas of the current magnetism roadmap and carries great potential to impact areas such as data storage, sensing, and biomagnetism. The properties of such nanostructures are closely connected with their 3D magnetic nanostructure, making their determination highly valuable. Up to now, quantitative 3D maps providing both the internal magnetic and electric configuration of the same specimen with high spatial resolution are missing. Here, we demonstrate the quantitative 3D reconstruction of the dominant axial component of the magnetic induction and electrostatic potential within a cobalt nanowire (NW) of 100 nm in diameter with spatial resolution below 10 nm by applying electron holographic tomography. The tomogram was obtained using a dedicated TEM sample holder for acquisition, in combination with advanced alignment and tomographic reconstruction routines. The powerful approach presented here is widely applicable to a broad range of 3D magnetic nanostructures and may trigger the progress of novel spintronic nonplanar nanodevices.This work was supported by the European Union under the Seventh Framework Program under a contract for an Integrated Infrastructure Initiative Reference 312483-ESTEEM2. S.B. and A.B. gratefully acknowledge funding by ERC Starting grants number 335078 COLOURATOMS and number 278510 VORTEX. A.F.-P. acknowledges an EPSRC Early Career fellowship and support from the Winton Foundation. E.S., C.G., and L.A.R. acknowledge the French ANR program for support though the project EMMA. J.M.D.T. and C. M. acknowledge the Spanish MINECO projects MAT2014-51982- C2-1-R and MAT2014-51982-C2-2-R, respectively.Peer Reviewe

Selective growth of PbSe on one or both tips of colloidal semiconductor nanorods.

PbSe nanocrystals with rock-salt structure are grown on the tips of colloidal CdS and CdSe nanorods. The facets of wurtzite rods provide a substrate with various degrees of reactivity for the growth of PbSe. The presence of dangling Cd bonds may explain subtle differences between nonequivalent facets resulting in the selective nucleation of PbSe only on one of the two tips of each CdS rod. This approach has the potential to facilitate the fabrication of heterostructures with tailored optical and electronic properties

Colloidal semiconductor/magnetic heterostructures based on iron-oxide-functionalized brookite TiO2 nanorods

A flexible colloidal seeded-growth strategy has been developed to synthesize all-oxide semiconductor/magnetic hybrid nanocrystals (HNCs) in various topological arrangements, for which the dimensions of the constituent material domains can be controlled independently over a wide range. Our approach relies on driving preferential heterogeneous nucleation and growth of spinel cubic iron oxide (IO) domains onto brookite TiO2 nanorods (b-TiO2) with tailored geometric parameters, by means of time-programmed delivery of organometallic precursors into a suitable TiO2-loaded surfactant environment. The b-TiO2 seeds exhibit size-dependent accessibility towards IO under diffusion-controlled growth regime, which allows attainment of HNCs individually made of a single b-TiO2 section functionalized with either one or multiple nearly spherical IO domains. In spite of the dissimilarity of the respective crystal-phases, the two materials share large interfacial junctions without significant lattice strain being induced across the heterostructures. The synthetic achievements have been supported by a systematic morphological, compositional and structural characterization of the as-prepared HNCs, offering a mechanistic insight into the specific role of the seeds in the control of heterostructure formation in liquid media. In addition, the impact of the formed b-TiO2/IO heterojunctions on the magnetic properties of IO has also been assessed

Customized MFM probes based on magnetic nanorods

International audienc

Colloidal Synthesis and Characterization of Tetrapod-Shaped Magnetic Nanocrystals

Tetrapod-shaped maghemite nanocrystals are synthesized by manipulating the decomposition of iron pentacarbonyl in a ternary surfactant mixture under mild thermal conditions. Adjustment of the reaction parameters allows for the systematic tuning of both the width and the length of the tetrapod arms, which grow preferentially along the 〈111〉 easy axis direction. Such degree of control leads to modulation of the magnetic behavior of the nanocrystals, which evolves systematically as their surface magnetization phase and shape anisotropy are progressively increased

Magnetic field strength and orientation effects on co-fe discontinuous multilayers close to percolation

International audienceMagnetization and magnetoresistance in function of the magnitude and orientation of applied magnetic field were studied in Co-Fe discontinuous multilayers close to their structural percolation. The high pulsed magnetic fields up to 33 T were used in the 120–310 K temperature range. Comparison between longitudinal and transverse with respect to the film plane field configurations was made in the low-field and high-field regimes in order to clarify the nature of the measured negative magnetoresistance. Coexistence of two distinct magnetic fractions, superparamagnetic SPM, consisting of small spherical Co-Fe granules and superferromagnetic SFM, by bigger Co-Fe clusters, was established in this system. These fractions were shown to have different relevance for the system magnetization and magnetotransport. While the magnetization is almost completely up to 97% defined by the SFM contribution and practically independent of temperature in this range, the magnetoresistance experiences a crossover from a regime dominated by Langevin correlations suppressed with temperature between neighbor SPM and SFM moments at low fields, to that dominated by spin scattering enhanced with temperature of charge carriers within SFM clusters at high fields. Also, the demagnetizing effects, sensitive to the field orientation, were found to essentially define the low-field behavior and characteristic crossover field

Microstructure and electrical properties of (Ba0.6Sr0.4)0.85Bi0.1TiO3 ceramics prepared by single-step, liquid-phase, solid-state reactive sintering

(Ba0.6Sr0.4)0.85Bi0.1TiO3 ceramics have been obtained by single-step, liquid-phase, solid-state reactive sintering in the temperature range 1250–1350 °C using stoichiometric amounts of BaTiO3, SrTiO3 and Bi4Ti3O12. Their microstructure and electrical properties have been studied by X-Ray diffraction and fluorescence, scanning and transmission electron microscopy and impedance spectroscopy. The relative density, Dr, relative permittivity, ε′r, and dissipation factor, tan δ, at room temperature and the bulk and grain boundary resistivity, Rb and Rgb, and activation energies, Eba and Egba, are approximately independent of the sintering temperature with values around e.g. Dr ~97.5 %, ε′r ~1790, tan δ ~0.06 %, R500oCb ~26 kΩ cm, Egba ~1.03 eV, R500oCgb ~217 kΩ cm and Egba ~1.41 eV. By contrast, the temperature coefficient of capacitance, TCC, increases linearly from ~10 ppm oC−1 to ~21 ppm oC−1 on increasing sintering temperature. Comments on the influence of the sintering temperature on the chemical composition of the ceramics are made

Serum 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D in dogs with sinonasal aspergillosis

peer reviewedSinonasal aspergillosis (SNA) is a common cause of chronic nasal disease with a still poorly understood pathophysiology and which remains a challenge to treat. There is increasing evidence that vitamin D plays a role in both innate and adaptative immunity. A preliminary retrospective study showed that serum 25-hydroxyvitamin D concentration, measured by high performance liquid chromatography (HPLC), was significantly lower in dogs affected with SNA compared to healthy dogs. Objectives of this prospective study were 1) to compare serum 25(OH)D and 24,25(OH)2D concentrations in dogs with SNA to healthy control dogs and dogs with lymphoplasmacytic rhinitis (LPR) or nasal neoplasia; and 2) to determine if serum 25(OH)D and 24,25(OH)2D concentrations in dogs with SNA change from the time of diagnosis to when a cure is achieved. Twenty dogs with a novel diagnosis of SNA, 12 healthy control dogs, 9 dogs with LPR, 10 dogs with nasal neoplasia were included. Nine dogs with SNA were available for follow up until cure. Serum vitamin D concentrations were measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) and compared: 1) among the different groups using a One-way ANOVA and 2) from diagnosis to cure with a paired t-test (significant p-value <0,05 for both tests). The vitamin D metabolite ratio (VMR) was calculated by dividing the 25(OH)D by the 24,25(OH)2D concentration. Serum 25(OH)D and 24,25(OH)2D were lower in dogs with SNA at the time of diagnosis (mean ± standard deviation = 23.5 ± 7,1 ng/ml – 10,5 ± 4,2 ng/ml, respectively) than in healthy dogs (34,1 ± 7,5 ng/ml; p=0,017 - 18,2 ± 5.4 ng/ml; p = 0,005) while there was no difference between healthy and dogs with tumor (27,8 ± 10,9 ng/ml – 15,4 ± 6,5 ng/ml) or LPR (27,4 ± 13,7 ng/ml – 14,3 ± 8,7 ng/ml). There was no significant difference in serum 25(OH)D and 24,25(OH)2D between dogs with SNA at the time of diagnosis and dogs achieving cure. The VMR was higher in SNA dogs (2,4 ± 0,7) than in control dogs (1,9 ± 0,3; p=0,031 t-test), indicating a decreased catabolic clearance of vitamin D in SNA dogs. These results further support the rationale that vitamin D could play a role in dogs with SNA as it does in human with aspergillosis. Whether hypovitaminosis D could contribute to the development of SNA or if oral supplementation could be a beneficial adjunctive therapy in affected dogs is unknown and warrants future investigations

Performance of Coffea arabica F1 hybrids in agroforestry and full-sun cropping systems in comparison with American pure line cultivars

Coffea arabica F1 hybrids derived from crosses between wild Sudan-Ethiopian and American cultivars and propagated by somatic embryogenesis have been obtained in Central America. These new hybrids considerably enhanced the genetic diversity of coffee in the region. We conducted 15 trials to assess whether using hybrids represents substantial genetic progress in terms of productivity in agroforestry and full-sun cropping systems. The new germplasm was grown in the same conditions as the best American cultivar (homozygous pure lines). The results showed that yields of hybrids were earlier and superior to those of American cultivars. The hybrids were also more stable than the American cultivars in all environments. In the agroforestry system, the mean yield of hybrids was 58% higher than that of the American cultivars, while the mean yield of hybrids in the full-sun system was 34% higher. Coffee-based agroforestry systems (AS) are considered effective in protecting the environment in the volcanic cordilleras of Central America. We found that introducing hybrids in coffee-based AS can considerably increase productivity. This finding could be a convincing argument to encourage coffee growers who have adopted the full-sun cropping system to return to agroforestry cropping systems. Finally, the conditions for large-scale dissemination of those new hybrids—which represent a major innovation for C. arabica cropping—was analysed

Desafíos de la caficultura en Centroamérica

Contiene: 1 Trayectoria y viabilidad de las caficulturas centroamericanas (Mario Samper). 2 Aspectos de la sostenibilidad de los sistemas de cultivo de café en América Central (Carlos E. Fernández y Reinhold G. Muschler). 3 Los suelos cafetaleros en América Central y su fertilización (Elemer Bornemisza, Jean Collinet y Alvaro Segura). 4 Hacia un manejo sostenible de la materia orgánica y de la fertilidad biológica de los suelos cafetaleros (Philippe Vaast y Didier Snoeck). 5 El beneficiado ecológico del café (Rolando Vásquez). 6 La roya anaranjada del cafeto: mito y realidad (Jacques Avelino, Raoul Muller, Albertus Eskes, Rodney Santacreo y Francisco Holguín). 7 El ojo de gallo del cafeto (Mycena citricolor) (Amy Wang y Jacques Avelino). 8 La Anthracnosis de los frutos: un grave peligro para la caficultura centroamericana (Raoul A. Müller, Dominique Berry y Daniel Bieysse). 9 La broca de los frutos del cafeto: +la lucha biológica como solución? (Bernard Dufour, Juan Francisco Barrera y Bernard Decazy). 10 Los Nematodos Parásitos del cafeto (Luc Villain, Francisco Anzueto, Adám Hernández y Jean Louis Sarah). 11 Los recursos genéticos: las bases de una solución genética a los problemas de la caficultura latinoamericana (Franéois Anthony, Carlos Astorga y Julien Berthaud). 12 El mejoramiento genético en América Central (Beno¯t Bertrand, Germán Aguilar, Rodney Santacreo y Francisco Anzueto. 13 Aportes de la biotecnología al mejoramiento genético del café: el ejemplo de la multiplicación por embriogénesis somática de híbridos F1 en América Central (Hervé Etienne, Dominique Barry-Etienne, Nelly Vásquez y Marc Berthouly).2 fig. Cuenta con un glosario.Este documento es una recopilación de información realizada por varias autores y autoras. El libro intenta contribuir al debate y desafíos de la investigación cafetalera, presentando los grandes problemas ecológicos, Agronómicos y biológicos que acechan a la caficultura centroamericana, o que la afectarán probablemente en un futuro cercano. El libro comienza por una resena hist6rica que permite tanto entender la diversidad de situaciones de producci6n coma interpretar los debates actuales en un contexto mas amplio de una historia bisecular. Luego, se estudian los principales avances y limitaciones de los sistemas de cultivo con una atención particular del manejo deI suelo con el afán de proponer soluciones, o de identificar campos prioritarios de investigación. También se repasan los grandes desafios deI beneficiado dei café que son principalmente ecológicos. Un gran espacio es dedicado al estudio de las principales enfermedades y plagas deI café, cuyo desarrollo y agravamiento repercute en costos de control muy elevados. La lucha biológica o integrada puede (o podrá) ofrecer soluciones alentadoras. En fin, se presentan las posibilidades de creaci6n de nuevas variedades de café a partir de los recursos genéticos introducidos de Africa, con las esperanzas que despiertan las nuevas biotecnologias