Elucidating Individual Magnetic Contributions in Bi-Magnetic Fe3 O4 /Mn3 O4 Core/Shell Nanoparticles by Polarized Powder Neutron Diffraction.

Heterogeneous bi-magnetic nanostructured systems have had a sustained interest during the last decades owing to their unique magnetic properties and the wide range of derived potential applications. However, elucidating the details of their magnetic properties can be rather complex. Here, a comprehensive study of Fe3 O4 /Mn3 O4 core/shell nanoparticles using polarized neutron powder diffraction, which allows disentangling the magnetic contributions of each of the components, is presented. The results show that while at low fields the Fe3 O4 and Mn3 O4 magnetic moments averaged over the unit cell are antiferromagnetically coupled, at high fields, they orient parallel to each other. This magnetic reorientation of the Mn3 O4 shell moments is associated with a gradual evolution with the applied field of the local magnetic susceptibility from anisotropic to isotropic. Additionally, the magnetic coherence length of the Fe3 O4 cores shows some unusual field dependence due to the competition between the antiferromagnetic interface interaction and the Zeeman energies. The results demonstrate the great potential of the quantitative analysis of polarized neutron powder diffraction for the study of complex multiphase magnetic materials.

The potential role of imaging techniques in avoiding neck dissection during salvage surgery after head and neck carcinoma treated with bioradiotherapy.

OBJECTIVE: This study aimed to evaluate the effectiveness of computed tomography and positron emission tomography-computed tomography prior to salvage surgery after head and neck carcinoma treated with bioradiotherapy and to look at the role of neck dissection in this setting. METHOD: This study was a retrospective chart review of a series of consecutive patients with locally advanced head and neck squamous cell carcinoma treated with bioradiotherapy. Radiological and pathological stages were compared to evaluate the accuracy of computed tomography and positron emission tomography-computed tomography in detecting occult neck metastasis in the context of recurrence of primary tumour. In order to assess the impact of neck dissection on survival, Kaplan-Meier survival curves after salvage surgery with and without neck dissection were derived. RESULTS: A total of 268 patients were identified, of which 22 underwent salvage surgery. The negative predictive value of computed tomography and positron emission tomography-computed tomography was excellent. Neck dissection did not represent an improvement on overall, disease specific and regional recurrence free survival (p = 0.67, p = 0.91 and p = 0.62, respectively) amongst clinically and radiologically negative necks. CONCLUSION: Conservative treatment of the neck should be considered when dealing with patients with primary site recurrence or persistent disease after bioradiotherapy without evidence of neck disease.

Novel Ba-hexaferrite structural variations stabilized on the nanoscale as building blocks for epitaxial bi-magnetic hard/soft sandwiched maghemite/hexaferrite/maghemite nanoplatelets with out-of-plane easy axis and enhanced magnetization.

Atomic-resolution scanning-transmission electron microscopy showed that barium hexaferrite (BHF) nanoplatelets display a distinct structure, which represents a novel structural variation of hexaferrites stabilized on the nanoscale. The structure can be presented in terms of two alternating structural blocks stacked across the nanoplatelet: a hexagonal (BaFe6O11)2- R block and a cubic (Fe6O8)2+ spinel S block. The structure of the BHF nanoplatelets comprises only two, or rarely three, R blocks and always terminates at the basal surfaces with the full S blocks. The structure of a vast majority of the nanoplatelets can be described with a SR*S*RS stacking order, corresponding to a BaFe15O23 composition. The nanoplatelets display a large, uniaxial magnetic anisotropy with the easy axis perpendicular to the platelet, which is a crucial property enabling different novel applications based on aligning the nanoplatelets with applied magnetic fields. However, the BHF nanoplatelets exhibit a modest saturation magnetization, MS, of just over 30 emu g-1. Given the cubic S block termination of the platelets, layers of maghemite, γ-Fe2O3, (M), with a cubic spinel structure, can be easily grown epitaxially on the surfaces of the platelets, forming a sandwiched M/BHF/M platelet structure. The exchange-coupled composite nanoplatelets exhibit a remarkably uniform structure, with an enhanced MS of more than 50 emu g-1 while essentially maintaining the out-of-plane easy axis. The enhanced MS could pave the way for their use in diverse platelet-based magnetic applications.

Residual neck disease management in squamous-cell carcinoma of the head and neck treated with radiotherapy plus cetuximab

Purpose. Management of residual neck disease (RND) is one of the unsolved points after bio-radiotherapy (BRT) in loco-regional advanced squamous-cell carcinoma of the head and neck (SCCHN). The aims of the study were to characterize the radiological pattern of response by computed tomography (CT) and to assess the role of positron-emission tomography (PET)/CT in this setting for a better decision-making in the indication of neck dissection (ND). Methods. We retrospectively reviewed 202 patients consecutively diagnosed with node-positive SCCHN (N1: 24; N2: 152; N3: 26) who had been treated with concomitant radiotherapy and cetuximab with or without previous induction chemotherapy between 2006 and 2013. Radiological evaluation after treatment was assessed by standard criteria using CT and in addition by PET/CT when RND was suspected in cases from 2010. Results. There were 42 (21 %) patients who achieved complete response of the primary tumor persisting RND by CT. From this group, 24 patients were managed without PET/CT, leading to the performance of ND in 22 (92 %). On the other hand, 18 patients underwent PET/CT and ND was performed in only 6 (33 %). The overall survival was not different between both groups (p = 0.32). After histological examination and follow-up, PET/CT obtained a positive predictive value of 56 % and a negative predictive value of 89 %. Conclusions. Radiological response after BRT is similar to that after treatment with chemo-radiotherapy, thereby validating in this scenario the accepted CT criteria to define complete response of the neck. However, when RND is suspected by CT, PET/CT is useful to prevent unnecessary ND (AU)

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[Percutaneous coronary intervention in Navarre. Outcomes of a low volume centre]. / Intervencionismo coronario percutáneo en Navarra. Resultados de un centro de bajo volumen intervencionista.

BACKGROUND: Percutaneous coronary intervention (PCI)is currently a basic therapeutic option in patients with coronary artery disease. To carry this out specialists must be trained and accredited. It is known that the number of procedures performed each year influences results. We suggest that some low volume centres may also get good results. METHODS: Prospective analysis of clinical features and immediate results obtained in our centre following PCI performed between 2006 and 2012 and retrospective analysis of overall survival, outcome-free survival and restenosis in patients treated between 2006 and 2009.The clinical features, acute and long-term events (complications,survival and mortality) of our group were compared with other published studies. RESULTS: In our centre the likelihood of complications ina PCI was 9% with an overall mortality of 2%. PCI mortality in stable coronary disease was 0.43% and in acute coronary syndrome 6.25%. Complications at the vascular access site was 1.44% and restenosis at nine months, inpatients undergoing PCI for the first time, was 5.2%. CONCLUSIONS: Although a high interventionist volume has been shown to reduce the rate of complications and improve long-term evolution, some low volume interventional centres can obtain similar results to those of high volume interventional centres.

Intervencionismo coronario percutáneo en Navarra. Resultados de un centro de bajo volumen intervencionista / Percutaneous coronary intervention in Navarre. Outcomes of a low volume centre

Fundamento: El intervencionismo coronario percutáneo (PCI) es una opción terapéutica fundamental en pacientes con enfermedad coronaria. Para realizarla los especialistas deben formarse y acreditarse. Se sabe que el número de procedimientos realizados al año influye en los resultados. Pretendemos mostrar que con un bajo volumen de PCI algunos centros obtienen buenos resultados. Método: Análisis prospectivo de las características clínicas y resultados inmediatos obtenidos en nuestro centro con el PCI entre 2006 y 2012 y análisis retrospectivo de la supervivencia global, supervivencia libre de eventos y reestenosis de los PCI realizados entre 2006 y 2009. Se compararon las características clínicas, los eventos agudos y a largo plazo (complicaciones, supervivencia y mortalidad) entre nuestros pacientes y los de algunos trabajos publicados. Resultados: Nuestra probabilidad de tener cualquier complicación en un PCI fue del 9% con una mortalidad global del 2%. La mortalidad del PCI en situación estable fue del 0,43% y en el síndrome coronario agudo del 6,25%. Las complicaciones en el lugar del acceso vascular fueron del 1,44% y la incidencia de reestenosis a los nueve meses, en pacientes sometidos por primera vez a PCI, fue del 5,2%. Conclusiones: Aunque el alto volumen intervencionista ha demostrado ser importante para tener una baja tasa de complicaciones y una buena evolución a largo plazo, hay centros con bajo volumen intervencionista que por sus características pueden obtener resultados equiparables a los de alto volumen (AU)

Background: Percutaneous coronary intervention (PCI) is currently a basic therapeutic option in patients with coronary artery disease. To carry this out specialists must be trained and accredited. It is known that the number of procedures performed each year influences results. We suggest that some low volume centres may also get good results. Methods: Prospective analysis of clinical features and immediate results obtained in our centre following PCI performed between 2006 and 2012 and retrospective analysis of overall survival, outcome-free survival and restenosis in patients treated between 2006 and 2009. The clinical features, acute and long-term events (complications, survival and mortality) of our group were compared with other published studies. Results: In our centre the likelihood of complications in a PCI was 9% with an overall mortality of 2%. PCI mortality in stable coronary disease was 0.43% and in acute coronary syndrome 6.25%. Complications at the vascular access site was 1.44% and restenosis at nine months, in patients undergoing PCI for the first time, was 5.2%. Conclusions: Although a high interventionist volume has been shown to reduce the rate of complications and improve long-term evolution, some low volume interventional centres can obtain similar results to those of high volume interventional centres (AU)

Residual neck disease management in squamous-cell carcinoma of the head and neck treated with radiotherapy plus cetuximab.

PURPOSE: Management of residual neck disease (RND) is one of the unsolved points after bio-radiotherapy (BRT) in loco-regional advanced squamous-cell carcinoma of the head and neck (SCCHN). The aims of the study were to characterize the radiological pattern of response by computed tomography (CT) and to assess the role of positron-emission tomography (PET)/CT in this setting for a better decision-making in the indication of neck dissection (ND). METHODS: We retrospectively reviewed 202 patients consecutively diagnosed with node-positive SCCHN (N1: 24; N2: 152; N3: 26) who had been treated with concomitant radiotherapy and cetuximab with or without previous induction chemotherapy between 2006 and 2013. Radiological evaluation after treatment was assessed by standard criteria using CT and in addition by PET/CT when RND was suspected in cases from 2010. RESULTS: There were 42 (21 %) patients who achieved complete response of the primary tumor persisting RND by CT. From this group, 24 patients were managed without PET/CT, leading to the performance of ND in 22 (92 %). On the other hand, 18 patients underwent PET/CT and ND was performed in only 6 (33 %). The overall survival was not different between both groups (p = 0.32). After histological examination and follow-up, PET/CT obtained a positive predictive value of 56 % and a negative predictive value of 89 %. CONCLUSIONS: Radiological response after BRT is similar to that after treatment with chemo-radiotherapy, thereby validating in this scenario the accepted CT criteria to define complete response of the neck. However, when RND is suspected by CT, PET/CT is useful to prevent unnecessary ND.

Electrochemically synthesized amorphous and crystalline nanowires: dissimilar nanomechanical behavior in comparison with homologous flat films.

The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (ϕ ≈ 100 nm) with films (3 µm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires requires taking the curved geometry of the indented surface and sink-in effects into account. These findings are of high relevance for optimizing the performance of new, mechanically-robust, nanoscale materials for increasingly complex miniaturized devices.

One-pot electrosynthesis of multi-layered magnetic metallopolymer nanocomposites.

Researchers have been investigating various methodologies for fabricating well-defined, homogenous composites consisting of nanoparticles (NPs) dispersed in a matrix. The main challenges are to prevent particle agglomerations during fabrication and to obtain nanoparticles whose size distribution could be tuned on demand. One of the methods that can provide these features is electrodeposition. We report for the first time the fabrication of a thin magnetic multilayer nanocomposite film by electrodeposition from one bath containing both a monomer and metal salts. Cobalt and cobalt-nickel NPs were deposited on conductive polymer polypyrrole thin films using different electrodeposition potentials and times. Multilayer nanocomposite films were fabricated by subsequent electrodeposition of polymer and nanoparticle layers. Scanning electron microscopy analysis showed that a wide range of NPs (70-230 nm) could be synthesized by manipulating growth potentials and times. The cobalt-nickel NPs were found to contain hexagonal close-packed (hcp) and face-centered cubic (fcc) phases based on X-ray diffraction and selected area electron diffraction. Magnetic measurements proved that both the single and the multi-layered nanocomposites were magnetic at room temperature.

Robust antiferromagnetic coupling in hard-soft bi-magnetic core/shell nanoparticles.

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.

Mesoscopic model for the simulation of large arrays of bi-magnetic core/shell nanoparticles.

A mesoscopic approach to simulate large arrays of core/shell nanoparticles based on the reduction of the number of simulated spins is presented. The model is used to simulate arrays of Co/CoO nanoparticles with different nanoparticle densities.

Strongly exchange coupled inverse ferrimagnetic soft/hard, Mn(x)Fe(3-x)O4/Fe(x)Mn(3-x)O4, core/shell heterostructured nanoparticles.

Inverted soft/hard, in contrast to conventional hard/soft, bi-magnetic core/shell nanoparticles of Mn(x)Fe(3-x)O(4)/Fe(x)Mn(3-x)O(4) with two different core sizes (7.5 and 11.5 nm) and fixed shell thickness (∼0.6 nm) have been synthesized. The structural characterization suggests that the particles have an interface with a graded composition. The magnetic characterization confirms the inverted soft/hard structure and evidences a strong exchange coupling between the core and the shell. Moreover, larger soft core sizes exhibit smaller coercivities and loop shifts, but larger blocking temperatures, as expected from spring-magnet or graded anisotropy structures. The results indicate that, similar to thin film systems, the magnetic properties of soft/hard core/shell nanoparticles can be fine tuned to match specific applications.

Distinguishing the core from the shell in MnO(x)/MnO(y) and FeO(x)/MnO(x) core/shell nanoparticles through quantitative electron energy loss spectroscopy (EELS) analysis.

The structural and chemical characterization of inverted bi-magnetic MnO(x)(antiferromagnetic)/MnO(y)(ferrimagnetic) and FeO(x)(soft-ferrimagnetic)/MnO(x)(hard-ferrimagnetic) core/shell nanoparticles has been carried out by means of scanning transmission electron microscopy with electron energy loss spectroscopy analysis, (S)TEM-EELS. Quantitative EELS was applied to assess the local composition of the nanoparticles by evaluating the local Mn oxidation state based on the Mn L3/L2 peak intensity ratio and the Mn L3 peak onset. The analysis allows to unambiguously distinguish the core from the shell and to determine the nature of the involved manganese oxides in both cases. The results evidence that the structure of the nanoparticles is, in fact, more complex than the one designed by the synthesis parameters.

Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates.

Nanostructured biological materials inspire the creation of materials with tunable mechanical properties. Strong cellulose nanofibrils derived from bacteria or wood can form ductile or tough networks that are suitable as functional materials. Here, we show that freeze-dried bacterial cellulose nanofibril aerogels can be used as templates for making lightweight porous magnetic aerogels, which can be compacted into a stiff magnetic nanopaper. The 20-70-nm-thick cellulose nanofibrils act as templates for the non-agglomerated growth of ferromagnetic cobalt ferrite nanoparticles (diameter, 40-120 nm). Unlike solvent-swollen gels and ferrogels, our magnetic aerogel is dry, lightweight, porous (98%), flexible, and can be actuated by a small household magnet. Moreover, it can absorb water and release it upon compression. Owing to their flexibility, high porosity and surface area, these aerogels are expected to be useful in microfluidics devices and as electronic actuators.

Magnetic proximity effect features in antiferromagnetic/ferrimagnetic core-shell nanoparticles.

A study of "inverted" core-shell, MnO/gamma-Mn(2)O(3), nanoparticles is presented. Crystal and magnetic structures and characteristic sizes have been determined by neutron diffraction for the antiferromagnetic core (MnO) and the ferrimagnetic shell (gamma-Mn(2)O(3)). Remarkably, while the MnO core is found to have a T_{N} not far from its bulk value, the magnetic order of the gamma-Mn(2)O(3) shell is stable far above T_{C}, exhibiting two characteristic temperatures, at T approximately 40 K [T_{C}(gamma-Mn(2)O(3))] and at T approximately 120 K [ approximately T_{N}(MnO)]. Magnetization measurements are consistent with these results. The stabilization of the shell moment up to T_{N} of the core can be tentatively attributed to core-shell exchange interactions, hinting at a possible magnetic proximity effect.

Cubic versus spherical magnetic nanoparticles: the role of surface anisotropy.

The magnetic properties of maghemite (gamma-Fe2O3) cubic and spherical nanoparticles of similar sizes have been experimentally and theoretically studied. The blocking temperature, T(B), of the nanoparticles depends on their shape, with the spherical ones exhibiting larger T(B). Other low temperature properties such as saturation magnetization, coercivity, loop shift or spin canting are rather similar. The experimental effective anisotropy and the Monte Carlo simulations indicate that the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of gamma-Fe2O3 is the origin of these effects.

Magnetic properties of Ni-NiO (ferromagnetic-antiferromagnetic) nanocomposites obtained from a partial mechanochemical reduction of NiO.

The magnetic properties of ferromagnetic (FM)-antiferromagnetic (AFM), Ni-NiO, nanocomposites obtained from a reactive ball milling reduction of NiO in H2 atmosphere have been studied. The formation of ferromagnetic Ni from antiferromagnetic NiO can be accurately followed by the increase of the saturation magnetization. The microstructure of the nanocomposite, consisting of FM Ni nanoparticles embedded in an AFM NiO matrix leads to exchange bias effects, i.e., loop shifts and coercivity enhancement, after field cooling from above the Néel temperature of NiO.

Acoustic barriers obtained from industrial wastes.

Acoustic pollution is an environmental problem that is becoming increasingly more important in our society. Likewise, the accumulation of generated waste and the need for waste management are also becoming more and more pressing. In this study we describe a new material--called PROUSO--obtained from industrial wastes. PROUSO has a variety of commercial and engineering, as well as building, applications. The main raw materials used for this environmentally friendly material come from slag from the aluminium recycling process, dust from the marble industry, foundry sands, and recycled expanded polystyrene from recycled packaging. Some natural materials, such as plastic clays, are also used. To obtain PROUSO we used a conventional ceramic process, forming new mineral phases and incorporating polluted elements into the structure. Its physical properties make PROUSO an excellent acoustic and thermal insulation material. It absorbs 95% of the sound in the frequency band of the 500 Hz. Its compressive strength makes it ideal for use in ceramic wall building.

Magnetic instability regions in patterned structures: influence of element shape on magnetization reversal dynamics.

We report a time-resolved imaging study of the influence of shape on magnetic instabilities in patterned magnetic structures. We find that in rectangular structures magnetization reversal initiates at the ends and interior simultaneously, while in structures with tapered ends the reversal begins in the middle of the structures and spreads out to the ends. The degree of tapering is important for both the switching field and the time required for full reversal. A model based on the concept of local instability regions yields good agreement with the observed location of the reversal onsets.

Heavy metal-rich wastes sequester in mineral phases through a glass-ceramic process.

Certain sludges generated by industry are rich in contaminating elements and are a major environmental problem. In this study, we determine the ability of these contaminating elements to be incorporated into a glass-matrix and in various mineral phases after a crystallization process. The contaminating elements studied were obtained from sewage sludges (SS) and galvanic sludges (GS), our raw materials. The sludge samples were taken from urban wastewater treatment plant in Catalonia (NE Spain) with high levels of phosphorus oxide (P(2)O(5)). In silica glasses, P(2)O(5) acts as a network former. We determined the chemical composition of both the SS and GS, as well as their thermal behaviour by differential thermal analysis and thermal gravimetric analysis (DTA-TG) to obtain their melting curves. The vitreous transition temperature of the obtained glass was established by dilatometer technique at 725 degrees C. The DTA-TG curve of the glass obtained has an exothermal wide peak at 860 degrees C corresponding to crystallization of the two phases: a spinel phase and a phosphate phase. A second exothermal wide peak at 960 degrees C was attributed to the crystallization of aluminium pyroxene, anorthite and fluor-apatite, with two exothermal phenomena attributed to the evolution of these phases. An exothermal peak at 1100 degrees C was attributed to gehlenite crystallization. Scanning electron microscope observations and energy-dispersed X-ray spectroscopy microanalyses of glass-ceramic showed that the contaminating elements were concentrated in the spinel phases, which are the first phases to crystallize during the cooling of glass. Finally, the spinel structure permits the incorporation of all the contaminating elements into it.