Probing the variability in oxidation states of magnetite nanoparticles by single-particle spectroscopy

We have studied the electronic and chemical properties of a variety of ensembles of size-and shape-selected Fe3O4 nanoparticles with single-particle sensitivity by means of synchrotron-based X-ray photoemission electron microscopy. The local X-ray absorption spectra reveal that the oxidation states and the amount and type of cations within the individual nanoparticles can show a striking local variability even when the average structural and magnetic parameters of the monodisperse ensembles appear to be compatible with those of conventional homogeneous magnetite nanoparticles. Our results show the key role played by oleic acid concentration in the reaction mixture on the formation and compositional homogeneity within individual nanoparticles. When the concentration of oleic acid is high enough, the nanoparticles are composed of a Fe3O4 core surrounded by a thin gamma-Fe2O3 shell. However, at a low concentration of the fatty acid, the Fe3O4 nanoparticles are likely inhomogeneous with small inclusions of FeO and Fe phases, as a result of an uncontrolled reduction of Fe3+ cations. All the foregoing underlines the importance of combining both advanced synthesis techniques and complementary single-particle investigations performed on a statistically significant number of particles so as to improve the understanding and control over electronic and magnetic phenomena at the nanoscale

Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes

Near-edge x-ray absorption fine structure investigation of graphene

We report the near-edge x-ray absorption fine structure (NEXAFS) spectrum of a single layer of graphite (graphene) obtained by micromechanical cleavage of Highly Ordered Pyrolytic Graphite (HOPG) on a SiO2 substrate. We utilized a PhotoEmission Electron Microscope (PEEM) to separately study single- double- and few-layers graphene (FLG) samples. In single-layer graphene we observe a splitting of the pi* resonance and a clear signature of the predicted interlayer state. The NEXAFS data illustrate the rapid evolution of the electronic structure with the increased number of layers.Comment: 5 pages, 4 figure

Investigación cualitativa en mujeres víctimas de violencia de género

ObjetivoAnalizar la experiencia de mujeres víctimas de la violencia de género atendidas en centros de atención primaria desde el punto de vista de las mujeres.DiseñoInvestigación cualitativa interpretativa. Perspectiva fenomenológica.EmplazamientoEstudio multicéntrico en centros de salud urbanos.ParticipantesMujeres víctimas de la violencia de género (física, psíquica, sexual)atendidas en los centros de salud. Muestreo intencional y teórico hasta el punto de saturación. Criterios de segmentación: edad (jóvenes-edad media-ancianas); maltrato actual o pasado; detección en urgencies-consultas.Mediciones principalesRelatos biográficos y análisis de contenido de la transcripción literal de las grabaciones. Codificación mediante programa NUD-IST. Utilización para la interpretación de la Teoría Fundamentada.LimitacionesComplejidad del fenómeno de estudio. Proyección de la perspectiva del investigador. Volumen ingente de datos. Se proponen estrategias para mejorar la credibilidad, la conformabilidad y la transferibilidad.Aplicabilidad prácticaMejorar el conocimiento de la situación de las mujeres víctimas de la violencia doméstica desde una perspectiva no directiva, lo que permitirá mejorar la calidad de las intervenciones.ObjectiveTo analyse, from the point of view of the women, the experience of women who are victims of male violence and attended at primary care centres.DesignInterpretative, qualitative research. Phenomenological perspective.SettingMulti-centre study in urban health centres.ParticipantsWomen victims of male violence (physical, psychological, or sexual) seen at health centres. Intention andtheoretical sampling to saturation point.Segmentation criteria: age (young/middle-aged/elderly); current or past ill-treatment; detection in casualty/consultations.Main measurementsBiographical accounts and content analysis of recordings’ literal transcription. Coding through the NUDIST programme. Use for interpreting Well-Founded Theory.LimitationsComplexity of the phenomenon under study. Projection of researcher’s perspective. Huge amount of data. Strategies are proposed for increasing credibility, conformity and transferability.Practical useTo improve understanding of the situation of women who are victims of domestic violence, from a non-directive perspective that enables the quality of interventions to be improved

A pilot study identifying a set of microRNAs as precise diagnostic biomarkers of acute kidney injury

In the last decade, Acute Kidney Injury (AKI) diagnosis and therapy have not notably improved probably due to delay in the diagnosis, among other issues. Precocity and accuracy should be critical parameters in novel AKI biomarker discovery. microRNAs are key regulators of cell responses to many stimuli and they can be secreted to the extracellular environment. Therefore, they can be detected in body fluids and are emerging as novel disease biomarkers. We aimed to identify and validate serum miRNAs useful for AKI diagnosis and management. Using qRT-PCR arrays in serum samples, we determined miRNAs differentially expressed between AKI patients and healthy controls. Statistical and target prediction analysis allowed us to identify a panel of 10 serum miRNAs. This set was further validated, by qRT-PCR, in two independent cohorts of patients with relevant morbi-mortality related to AKI: Intensive Care Units (ICU) and Cardiac Surgery (CS). Statistical correlations with patient clinical parameter were performed. Our results demonstrated that the 10 selected miRNAs (miR-101-3p, miR-127-3p, miR-210-3p, miR-126-3p, miR-26b-5p, miR-29a-3p, miR-146a-5p, miR-27a-3p, miR-93-3p and miR-10a-5p) were diagnostic biomarkers of AKI in ICU patients, exhibiting areas under the curve close to 1 in ROC analysis. Outstandingly, serum miRNAs estimated before CS predicted AKI development later on, thus becoming biomarkers to predict AKI predisposition. Moreover, after surgery, the expression of the miRNAs was modulated days before serum creatinine increased, demonstrating early diagnostic value. In summary, we have identified a set of serum miRNAs as AKI biomarkers useful in clinical practice, since they demonstrate early detection and high diagnostic value and they recognize patients at risk

Differences between 1999 and 2010 across the Falkland Plateau: fronts and water masses

Decadal differences in the Falkland Plateau are studied from the two full-depth hydrographic data collected during the ALBATROSS (April 1999) and MOC-Austral (February 2010) cruises. Differences in the upper 100 dbar are due to changes in the seasonal thermocline, as the ALBATROSS cruise took place in the austral fall and the MOCAustral cruise in summer. The intermediate water masses seem to be very sensitive to the wind conditions existing in their formation area, showing cooling and freshening for the decade as a consequence of a higher Antarctic Intermediate Water (AAIW) contribution and of a decrease in the Subantarctic Mode Water (SAMW) stratum. The deeper layers do not exhibit any significant change in the water mass properties. The Subantarctic Front (SAF) in 1999 is observed at 52.2–54.8 W with a relative mass transport of 32.6 Sv. In contrast, the SAF gets wider in 2010, stretching from 51.1 to 57.2 W (the Falkland Islands), and weakening to 17.9 Sv. Changes in the SAF can be linked with the westerly winds and mainly affect the northward flow of Subantarctic Surface Water (SASW), SAMW and AAIW/Antarctic Surface Water (AASW). The Polar Front (PF) carries 24.9 Sv in 1999 (49.8–44.4 W), while in 2010 (49.9–49.2 W) it narrows and strengthens to 37.3 Sv.En prens

Direct observation of enhanced magnetism in individual size- and shape-selected 3d transition metal nanoparticles

Magnetic nanoparticles are critical building blocks for future technologies ranging from nanomedicine to spintronics. Many related applications require nanoparticles with tailored magnetic properties. However, despite significant efforts undertaken towards this goal, a broad and poorly understood dispersion of magnetic properties is reported, even within monodisperse samples of the canonical ferromagnetic 3d transition metals. We address this issue by investigating the magnetism of a large number of size- and shape-selected, individual nanoparticles of Fe, Co, and Ni using a unique set of complementary characterization techniques. At room temperature, only superparamagnetic behavior is observed in our experiments for all Ni nanoparticles within the investigated sizes, which range from 8 to 20 nm. However, Fe and Co nanoparticles can exist in two distinct magnetic states at any size in this range: (i) a superparamagnetic state, as expected from the bulk and surface anisotropies known for the respective materials and as observed for Ni, and (ii) a state with unexpected stable magnetization at room temperature. This striking state is assigned to significant modifications of the magnetic properties arising from metastable lattice defects in the core of the nanoparticles, as concluded by calculations and atomic structural characterization. Also related with the structural defects, we find that the magnetic state of Fe and Co nanoparticles can be tuned by thermal treatment enabling one to tailor their magnetic properties for applications. This paper demonstrates the importance of complementary single particle investigations for a better understanding of nanoparticle magnetism and for full exploration of their potential for applications

Direct observation of transverse and vortex metastable magnetic domains in cylindrical nanowires

We present experimental evidence of transverse magnetic domains, previously observed only in nanostrips, in CoNi cylindrical nanowires with designed crystal symmetry and tailored magnetic anisotropy. The transverse domains are found together with more conventional vortex domains along the same cylindrical nanowire, denoting a bistable system with similar energies. The surface and the inner magnetization distribution in both types of domains are analyzed by photoemission electron microscopy with x-ray magnetic circular dichroism contrast, and hysteresis loop in individual nanowires are measured by magneto-optical Kerr effect. These experimental data are understood and compared with complementary micromagnetic simulations

Los socios de la RSEHN y el desarrollo de las colecciones científicas del MNCN

Valencia, del 8 al 11 de septiembre de 2021. El tema principal tuvo como lema: “La huella Humana en la Naturaleza”.Las colecciones científicas son una infraestructura de investigación única e irremplazable para numerosas áreas de la ciencia. En la actualidad, se estima que en el Museo Nacional de Ciencias Naturales se conservan 10 millones de especímenes, lo que suponen casi la mitad de todos los conservados en España. Esta infraestructura científica o este tesoro, como puede ser llamado, se ha reunido principalmente a lo largo del último siglo, y se debe al trabajo conjunto de muchos especialistas, estudiosos e interesados en diferentes disciplinas de las ciencias naturales. En esta ponencia se quiere poner en valor la aportación de los socios de la RSEHN en el incremento y desarrollo de las colecciones científicas del MNCN. Se ha realizado un análisis preliminar de los fondos de las diferentes colecciones del MNCN y de los ingresos efectuados por los socios de RSEHN desde su fundación (1871) hasta el momento en que abandona el MNCN (1971). Se realizó en cada una de ellas una consulta de los diferentes colectores y personas que aportaron especímenes y que aparecen en las bases de datos, cruzándola con la base de datos de socios durante dicho periodo. Se ha contabilizado el número de especímenes, número de tipos y taxones correspondientes a éstos. La cifra de socios total supera el centenar. El número de ejemplares ingresados por estos socios, entre esas fechas, se estima que superan el millón y medio, lo que supone al menos un 15% del total actual estimado. Hay que tener en cuenta que las colecciones no se encuentran informatizadas al 100%