Antiferromagnetic textures in BiFeO3 controlled by strain and electric field.

Antiferromagnetic thin films are currently generating considerable excitement for low dissipation magnonics and spintronics. However, while tuneable antiferromagnetic textures form the backbone of functional devices, they are virtually unknown at the submicron scale. Here we image a wide variety of antiferromagnetic spin textures in multiferroic BiFeO3 thin films that can be tuned by strain and manipulated by electric fields through room-temperature magnetoelectric coupling. Using piezoresponse force microscopy and scanning NV magnetometry in self-organized ferroelectric patterns of BiFeO3, we reveal how strain stabilizes different types of non-collinear antiferromagnetic states (bulk-like and exotic spin cycloids) as well as collinear antiferromagnetic textures. Beyond these local-scale observations, resonant elastic X-ray scattering confirms the existence of both types of spin cycloids. Finally, we show that electric-field control of the ferroelectric landscape induces transitions either between collinear and non-collinear states or between different cycloids, offering perspectives for the design of reconfigurable antiferromagnetic spin textures on demand.

Inverse transition of labyrinthine domain patterns in ferroelectric thin films.

Phase separation is a cooperative process, the kinetics of which underpin the orderly morphogenesis of domain patterns on mesoscopic scales1,2. Systems of highly degenerate frozen states may exhibit the rare and counterintuitive inverse-symmetry-breaking phenomenon3. Proposed a century ago4, inverse transitions have been found experimentally in disparate materials, ranging from polymeric and colloidal compounds to high-transition-temperature superconductors, proteins, ultrathin magnetic films, liquid crystals and metallic alloys5,6, with the notable exception of ferroelectric oxides, despite extensive theoretical and experimental work on the latter. Here we show that following a subcritical quench, the non-equilibrium self-assembly of ferroelectric domains in ultrathin films of Pb(Zr0.4Ti0.6)O3 results in a maze, or labyrinthine pattern, featuring meandering stripe domains. Furthermore, upon increasing the temperature, this highly degenerate labyrinthine phase undergoes an inverse transition whereby it transforms into the less-symmetric parallel-stripe domain structure, before the onset of paraelectricity at higher temperatures. We find that this phase sequence can be ascribed to an enhanced entropic contribution of domain walls, and that domain straightening and coarsening is predominantly driven by the relaxation and diffusion of topological defects. Computational modelling and experimental observation of the inverse dipolar transition in BiFeO3 suggest the universality of the phenomenon in ferroelectric oxides. The multitude of self-patterned states and the various topological defects that they embody may be used beyond current domain and domain-wall-based7 technologies by enabling fundamentally new design principles and topologically enhanced functionalities within ferroelectric films.

Real-space imaging of non-collinear antiferromagnetic order with a single-spin magnetometer.

Although ferromagnets have many applications, their large magnetization and the resulting energy cost for switching magnetic moments bring into question their suitability for reliable low-power spintronic devices. Non-collinear antiferromagnetic systems do not suffer from this problem, and often have extra functionalities: non-collinear spin order may break space-inversion symmetry and thus allow electric-field control of magnetism, or may produce emergent spin-orbit effects that enable efficient spin-charge interconversion. To harness these traits for next-generation spintronics, the nanoscale control and imaging capabilities that are now routine for ferromagnets must be developed for antiferromagnetic systems. Here, using a non-invasive, scanning single-spin magnetometer based on a nitrogen-vacancy defect in diamond, we demonstrate real-space visualization of non-collinear antiferromagnetic order in a magnetic thin film at room temperature. We image the spin cycloid of a multiferroic bismuth ferrite (BiFeO3) thin film and extract a period of about 70 nanometres, consistent with values determined by macroscopic diffraction. In addition, we take advantage of the magnetoelectric coupling present in BiFeO3 to manipulate the cycloid propagation direction by an electric field. Besides highlighting the potential of nitrogen-vacancy magnetometry for imaging complex antiferromagnetic orders at the nanoscale, these results demonstrate how BiFeO3 can be used in the design of reconfigurable nanoscale spin textures.

Multi-stimuli manipulation of antiferromagnetic domains assessed by second-harmonic imaging.

Among the variety of magnetic textures available in nature, antiferromagnetism is one of the most 'discrete' because of the exact cancellation of its staggered internal magnetization. It is therefore very challenging to probe. However, its insensitivity to external magnetic perturbations, together with the intrinsic sub-picosecond dynamics, make it very appealing for tomorrow's information technologies. Thus, it is essential to understand the microscopic mechanisms governing antiferromagnetic domains to achieve accurate manipulation and control. Using optical second-harmonic generation, a unique and laboratory-available tool, we succeeded in imaging with sub-micrometre resolution both electric and antiferromagnetic orders in the model multiferroic BiFeO3. We show here that antiferromagnetic domains can be manipulated with low power consumption, using sub-coercive electric fields and sub-picosecond light pulses. Interestingly, we also show that antiferromagnetic and ferroelectric domains can behave independently, thus revealing that magneto-electric coupling can lead to various arrangements of the two orders.

ABO incompatibility does not influence transfusion requirements in patients undergoing single-unit umbilical cord blood transplantation.

Hematopoietic stem cell transplantation is usually performed without considering the ABO compatibility between donor and recipient. There are few studies analyzing ABO matching impact on transfusion outcome of umbilical cord blood transplantation (UCBT) recipients. The aim of this study was to analyze factors influencing transfusion outcome, highlighting the ABO matching between donor and recipient. This study has reviewed data from 318 patients who underwent single unit UCBT at la Fe University Hospital from January 2000 to December 2014. There were no differences between RBC and platelet (PLT) requirements or RBC and PLT transfusion independence according to ABO matching between donor and recipient. RBC and PLT requirements were statistically correlated (ρ=0,841, P<0.001). A total of 170 and 188 patients achieved RBC and PLT independence, respectively, within 180 days after UCBT. Persistence of recipient isoagglutinins was detected in 6.8% of patients with major ABO incompatibility at median of 176 days (103-269) after UCBT. Autoimmune haemolytic anemia was diagnosed in 15 patients, 12 of them due to cold antibodies. In conclusion, ABO matching has not influenced transfusion requirements of patients undergoing UCBT.

Strain and Magnetic Field Induced Spin-Structure Transitions in Multiferroic BiFeO3.

The magnetic-field-dependent spin ordering of strained BiFeO3 films is determined using nuclear resonant scattering and Raman spectroscopy. The critical field required to destroy the cycloidal modulation of the Fe spins is found to be significantly lower than in the bulk, with appealing implications for field-controlled spintronic and magnonic devices.

Identification of a novel HLA-B*50 allele, HLA-B*50:01:08, in a Spanish hematological patient.

HLA-B*50:01:08 differs from B*50:01:01 at nucleotides g.1206T>A (intron 3) and g.1658G>A (exon 4).

Large elasto-optic effect and reversible electrochromism in multiferroic BiFeO3.

The control of optical fields is usually achieved through the electro-optic or acousto-optic effect in single-crystal ferroelectric or polar compounds such as LiNbO3 or quartz. In recent years, tremendous progress has been made in ferroelectric oxide thin film technology-a field which is now a strong driving force in areas such as electronics, spintronics and photovoltaics. Here, we apply epitaxial strain engineering to tune the optical response of BiFeO3 thin films, and find a very large variation of the optical index with strain, corresponding to an effective elasto-optic coefficient larger than that of quartz. We observe a concomitant strain-driven variation in light absorption--reminiscent of piezochromism--which we show can be manipulated by an electric field. This constitutes an electrochromic effect that is reversible, remanent and not driven by defects. These findings broaden the potential of multiferroics towards photonics and thin film acousto-optic devices, and suggest exciting device opportunities arising from the coupling of ferroic, piezoelectric and optical responses.

[Nutritional composition of infant milk formulas. Level of compliance in their manufacture and adequacy of nutritional needs]. / Composición nutricional de las leches infantiles. Nivel de cumplimiento en su fabricación y adecuación a las necesidades nutricionales.

INTRODUCTION: A high percentage of infants are fed with infant formulas. The aim of this study was to assess compliance with the Technical and Safety Regulations in the manufacture of Spanish infant formulas, analyse their adequacy to the recommendations of nutritional composition and the Dietary References Intakes for infants. MATERIALS AND METHODS: A total of 31 infant formulas were analysed, of which 18 were infant formulas, 10 follow-on formulas, and 3 growing-up milks. The European Technical and Safety Regulations, the Spanish Dietary Reference Intakes and the Institute of Medicine of the United States and Canada, were used for the assessment of compliance and adequacy. RESULTS: The energy and macronutrient content of analysed infant formulas is placed in the middle of the range indicated in the Technical and Safety Regulations, and meets the recommended amounts. However, most micronutrients such as phosphorus, calcium, retinol, vitamin D, E, C, B6, B12, thiamin, riboflavin, and folate are at the lower limit of the Technical and Safety Regulations. However, the recommended consumption of infant formulas exceeded the Dietary References Intakes for vitamin E, C, retinol, vitamin B and folate, and vitamin B12 for follow-on formulas. CONCLUSIONS: Infant formulas are within the reference values of the European Technical and Safety Regulations in energy and macronutrients, but we believe that the level of micronutrients should be reviewed, based on current scientific data on infant requirements and possible adverse effects.

Heat-induced gelation mechanism of blood plasma modulated by cysteine.

This work aims to determine changes at molecular level of plasma proteins provoked by adding cysteine (Cys, 0.025% to 0.35% w/v) as a reducing agent and their relationship with the heat-induced gel properties obtained when subsequently the solutions were submitted to a thermal treatment. Results show that adding Cys to plasma solutions at concentrations ≥0.15% actually entails modifications in the secondary structure of their main proteins, that is, serum albumin-α-helix rich-and globulin fraction-ß-sheet rich. Basically, a reduction of the intensity of the infrared (IR) bands assigned to both structures takes place concomitant to an increase of extended structures that seem to act as intermediates for the subsequent protein aggregation process through nonnative intermolecular ß-sheets. Cleavage of disulfide bonds is also evidenced at Cys concentrations ≥0.15% by nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), with the effects being directly proportional to Cys concentration. However, beneficial effects on gel hardness are gradually obtained at Cys concentrations ≤0.15%, that is, when the effects at molecular level are at most just budding, while not more improvements on this textural parameter are obtained at higher Cys concentrations. By contrast, water retention capacity is gradually diminishing as Cys concentration increases, but with a significant reduction only obtained at the highest tested concentration. These results suggest a negative effect of Cys on gel microstructure at high concentrations, which probably can be attributed to protein aggregation taking place at room temperature.

Control of ferroelectricity and magnetism in multi-ferroic BiFeO3 by epitaxial strain.

Recently, strain engineering has been shown to be a powerful and flexible means of tailoring the properties of ABO3 perovskite thin films. The effect of epitaxial strain on the structure of the perovskite unit cell can induce a host of interesting effects, these arising from either polar cation shifts or rotation of the oxygen octahedra, or both. In the multi-ferroic perovskite bismuth ferrite (BiFeO3-BFO), both degrees of freedom exist, and thus a complex behaviour may be expected as one plays with epitaxial strain. In this paper, we review our results on the role of strain on the ferroic transition temperatures and ferroic order parameters. We find that, while the Néel temperature is almost unchanged by strain, the ferroelectric Curie temperature strongly decreases as strain increases in both the tensile and compressive ranges. Also unexpected is the very weak influence of strain on the ferroelectric polarization value. Using effective Hamiltonian calculations, we show that these peculiar behaviours arise from the competition between antiferrodistortive and polar instabilities. Finally, we present results on the magnetic order: while the cycloidal spin modulation present in the bulk survives in weakly strained films, it is destroyed at large strain and replaced by pseudo-collinear antiferromagnetic ordering. We discuss the origin of this effect and give perspectives for devices based on strain-engineered BiFeO3.

Crafting the magnonic and spintronic response of BiFeO3 films by epitaxial strain.

Multiferroics are compounds that show ferroelectricity and magnetism. BiFeO3, by far the most studied, has outstanding ferroelectric properties, a cycloidal magnetic order in the bulk, and many unexpected virtues such as conductive domain walls or a low bandgap of interest for photovoltaics. Although this flurry of properties makes BiFeO3 a paradigmatic multifunctional material, most are related to its ferroelectric character, and its other ferroic property--antiferromagnetism--has not been investigated extensively, especially in thin films. Here we bring insight into the rich spin physics of BiFeO3 in a detailed study of the static and dynamic magnetic response of strain-engineered films. Using Mössbauer and Raman spectroscopies combined with Landau-Ginzburg theory and effective Hamiltonian calculations, we show that the bulk-like cycloidal spin modulation that exists at low compressive strain is driven towards pseudo-collinear antiferromagnetism at high strain, both tensile and compressive. For moderate tensile strain we also predict and observe indications of a new cycloid. Accordingly, we find that the magnonic response is entirely modified, with low-energy magnon modes being suppressed as strain increases. Finally, we reveal that strain progressively drives the average spin angle from in-plane to out-of-plane, a property we use to tune the exchange bias and giant-magnetoresistive response of spin valves.

Strain dependence of polarization and piezoelectric response in epitaxial BiFeO3 thin films.

Epitaxial strain has recently emerged as a powerful means to engineer the properties of ferroelectric thin films, for instance to enhance the ferroelectric Curie temperature (T(C)) in BaTiO(3). However, in multiferroic BiFeO(3) thin films an unanticipated strain-driven decrease of T(C) was reported and ascribed to the peculiar competition between polar and antiferrodistortive instabilities. Here, we report a systematic characterization of the room-temperature ferroelectric and piezoelectric properties for strain levels ranging between -2.5% and +1%. We find that polarization and the piezoelectric coefficient increase by about 20% and 250%, respectively, in this strain range. These trends are well reproduced by first-principles-based techniques.

Foaming and emulsifying properties of porcine red cell protein concentrate.

This work focuses on studying the effects of pH (7.0 and 4.5) and protein concentration on the foaming and emulsifying properties of fresh (F) and spray-dried (SD) porcine red cell protein (RCP) concentrates in order to evaluate the proper use of this blood protein as a functional food ingredient. Also, protein solubility is measured through the pH range from 3.0 to 8.0. In each case, all concentrates show a high solubility, although this is significantly affected by pH. Spray drying slightly reduces the solubility at mild acid and neutral conditions. The foaming capacity is found to be dependent on pH as well as on the drying treatment. SD-RCP concentrates show better foaming capacity than F-RCP. The minimum protein concentration required to attain the highest foaming capacity is found under acid pH for the spray-dried concentrates. Although F-RCP shows low foam stability at acid and neutral pH, spray drying and protein content enhance the stability of foams. Emulsifying properties show dependence on pH as well as on protein content. Furthermore, spray drying affects the emulsifying properties but in different ways, depending on pH and protein concentration.

Towards two-dimensional metallic behavior at LaAlO3/SrTiO3 interfaces.

Using a low-temperature conductive-tip atomic force microscope in cross-section geometry we have characterized the local transport properties of the metallic electron gas that forms at the interface between LaAlO3 and SrTiO3. At low temperature, we find that the carriers do not spread away from the interface but are confined within approximately 10 nm, just like at room temperature. Simulations taking into account both the large temperature and electric-field dependence of the permittivity of SrTiO3 predict a confinement over a few nm for sheet carrier densities larger than approximately 6x10(13) cm(-2). We discuss the experimental and simulations results in terms of a multiband carrier system. Remarkably, the Fermi wavelength estimated from Hall measurements is approximately 16 nm, indicating that the electron gas in on the verge of two dimensionality.

Color stabilization of porcine hemoglobin during spray-drying and powder storage by combining chelating and reducing agents.

This work focuses on the effects of adding a chelating agent - such as nicotinic acid (NA, 2% w/v) or nicotinamide (Nam, 2.5% w/v) - along with glucose as a reducing agent (G, 10% w/v) to fresh porcine hemoglobin in order to stabilize its red color during spray-drying and powder storage at room temperature. Correlations between the CIELAB color parameters and the relative percentages of the different hemoglobin derivatives (liganded and deliganded ferrohemoglobin, and methemoglobin) were analyzed. The results indicate that, although little effects could be observed for any of the combined treatments on fresh hemoglobin, they were effective against pigment autoxidation during dehydration and subsequent storage. From the results, it can also be concluded that glucose was the main contributor to the color stabilization of the hemoglobin powder, probably due to its high water retention capacity.

[Study of colorectal metachronous neoplastic lesions]. / Estudio de las lesiones neoplásicas metacrónicas en el carcinoma colorrectal.

BACKGROUND: To analyse the frequency and characteristics of metachronous neoplastic lesions, carcinomas and adenomas, following resection of colorectal cancer. PATIENTS AND METHODS: We reviewed 382 patients subjected to RCC operations and followed up through complete colonoscopies in two hospitals in our province. We analysed the metachronous lesions registered, evaluating their localisation, time of diagnosis, histology, number and size. We studied the frequency of early adenomas (12 months), comparing their size with the rest of the lesions. RESULTS: The average follow-up was 48 months (12-112), with 2.74+/-1.47 colonoscopies/case. We diagnosed 7 metachronous cancers (1.8%), 4 of them in stage I. The average time until their diagnosis was 24 months (13-54). We registered metachronous adenomas in 162 cases (42.4%), without differences between the two hospitals: 42.1% vs. 43.8% (p=0.88). Six point three percent of the patients presented advanced adenomas. In 164 cases where the control was carried out after 12 months, the incidence of adenomas was 24%. In the majority of cases, the adenomas were sole (60.8%) and smaller than 5 mm (68.5%). In 55.5% of the cases with polyps, some had a proximal localisation. Diagnosis was made on the 1st exploration (56.2%), the 2nd (27.8%) or the 3rd (9%). Average time until diagnosis was 21 months (12-112) for simple adenoma and 35 (12-112) for advanced adenoma. CONCLUSIONS: Our follow up made it possible to apply a theoretically curative treatment in the majority of the metachronous carcinomas diagnosed. The high incidence of adenomas and the frequent proximal localisation make a follow up with complete colonoscopies necessary, which must be started one year after the operation and can become less strict following three consecutive explorations without polyps.

Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures.

At the interface between complex insulating oxides, novel phases with interesting properties may occur, such as the metallic state reported in the LaAlO(3)/SrTiO(3) system . Although this state has been predicted and reported to be confined at the interface, some studies indicate a much broader spatial extension, thereby questioning its origin. Here, we provide for the first time a direct determination of the carrier density profile of this system through resistance profile mappings collected in cross-section LaAlO(3)/SrTiO(3) samples with a conducting-tip atomic force microscope (CT-AFM). We find that, depending on specific growth protocols, the spatial extension of the high-mobility electron gas can be varied from hundreds of micrometres into SrTiO(3) to a few nanometres next to the LaAlO(3)/SrTiO(3) interface. Our results emphasize the potential of CT-AFM as a novel tool to characterize complex oxide interfaces and provide us with a definitive and conclusive way to reconcile the body of experimental data in this system.

[Capsule endoscopy interpretation: the role of physician extenders]. / Interpretación de la cápsula endoscópica: el papel del personal no especializado.

BACKGROUND AND AIMS: capsule endoscopy (CE) allows for a new era in small-bowel examination. Nevertheless, physicians time for CE-interpretation remains longer than desirable. Alternative strategies to physicians have not been widely investigated. The aim of this study was to evaluate the accuracy of physician extenders in CE-interpretation. MATERIAL AND METHODS: one CE-experienced gastroenterologist and two physician extenders reviewed independently 20 CE-procedures. Each reader was blinded to the findings of their colleagues. A consensus formed by the readers and a second CE-experienced gastroenterologist was used as gold standard. Number, type and location of images selected, character of CE-exams and their relationship with indications were recorded. Gastric emptying time (GEt), small-bowel transit time (SBTt) and time spent by readers were also noted. RESULTS: sensitivity and specificity for "overall" lesions was 79 and 99% for the gastroenterologist; 86 and 43% for the nurse; and 80 and 57% for the resident. All 34 "major" lesions considered by consensus were found by the readers. Agreement between consensus and readers for images classification and procedures interpretation was good to excellent (? from 0.55 to 1). No significant differences were found in the GEt and SBTt obtained by consensus and readers. The gastroenterologist was faster than physician extenders (mean time spent was 51.9 +/- 13.5 minutes versus 62.2 +/- 19 and 60.9 +/- 17.1 for nurse and resident, respectively; p < 0.05). CONCLUSIONS: physician extenders could be the perfect complement to gastroenterologists for CE-interpretation but gastroenterologists should supervise their findings. Future cost-efficacy analyses are required to assess the benefits of this alternative.