X-ray absorption spectroscopy on iron oxide nanoparticles

Funktionalisierte Fe-Oxid-Nanopartikel in wässriger Lösung sind bei medizinischen Anwendungen weit verbreitet. Für einen erfolgreichen Einsatz dieser Partikel ist eine hohe Sättigungsmagnetisierung erforderlich. Diese ist reduziert, wenn verkantete Oberflächenspins in den Partikeln vorhanden sind oder Oxidationseffekte auftreten. Bezüglich dieser Eigenschaften wurden Fe3O4 -Nanopartikel mit Durchmessern zwischen 3 nm und 9 nm in dieser Arbeit untersucht. Die Partikel wurden nasschemisch synthetisiert und sind in Ethanol dispergierbar. In ferrimagnetischem Fe3O4 (Magnetit) unterscheiden sich die Fe-Ionen in ihrer Valenz und und in ihrem Gitterplatz. XMCD-Spektroskopie an den Fe L 3,2 -Absorptionskanten ermöglicht eine Trennung der Beiträge der Fe 2+ - und Fe 3+ -Ionen auf den tetraedrischen bzw. oktaedrischen Plätzen. Somit kann durch feldabhängige Messungen der XMCD-Asymmetrie das Verkantungsverhalten nicht nur größenabhängig, sondern auch in Abhängigkeit von ihrem Gitterplatz untersucht werden. Die Spinverkantung der 6-nm-Partikel ist an den drei inäquivalenten Gitterplätzen gering und ändert sich auch durch die Beschichtung mit SiO2 nicht. Die Messergebnisse zeigen weiter, dass die Spinverkantung der 3 nm großen Partikel am deutlichsten ist. Zudem fanden wir Hinweise, dass die Verkantung überwiegend an dem Gitterplatz der Fe 2+ -Ionen auftritt. XAS-Messungen an den Partikeln direkt in Dispersion zeigten, dass die unbeschichteten Partikel nicht über mehrere Tage in Lösung stabil sind, sondern weiter oxidieren. Dagegen bleibt bei einer Umhüllung mit einer 3 nm dicken SiO2 -Schicht ein hoher Magnetitanteil erhalten. Neben dem medizinischen Anwendungsbereich sind die Magnetit-Nanopartikel auch für die Grundlagenforschung interessant. In volumenartigem Magnetit tritt bei ungefähr 120 K ein Phasenübergang auf, der als Verwey-Übergang bekannt ist. Temperaturabhängige XAS- und XMCD-Messungen deuten darauf hin, dass der Übergang in Nanopartikeln mit 6 nm Durchmesser bei einer reduzierten kritischen Temperatur auftritt. Bei Partikeln mit einer SiO2 -Hülle traten die charakteristischen Sprünge in den Signalamplituden nicht mehr auf.Functionalized Fe oxide nanoparticles in aqueous solution are widely used for medical applications. For a successful use of these particles a high saturation magnetization is required. However, canted surface spins and effects of further oxidation reduce the saturation magnetization. In this thesis Fe3O4 (magnetite) nanoparticles of diameters between 3 nm and 9 nm have been analyzed with respect to canting and oxidation effects. The particles have been wet-chemically synthesized and dispersed in ethanol. In ferrimagnetic magnetite the Fe ions differ in charge and coordination symmetry. XMCD-spectroscopy at the Fe L 3,2 absorption edges allows to separate the contributions of the Fe 2+ ions and the Fe 3+ ions on their tetrahedral and octahedral lattice sites. By field-dependent XMCD measurements the canting behavior of the Fe spins has been studied site- and size-selectively. In case of 6 nm particles a small canting was observed at the three inequivalent lattice sites. This small canting was not affected even when the particles were coated by silica. The 3 nm particles exhibited the strongest canting. Our measurements indicated, that the canting is mainly due to the Fe 2+ ions at octahedral sites. XAS measurements of bare nanoparticles kept in dispersion showed further oxidation over a period of several days. In contrast, by coating with 3 nm silica the high amount of magnetite can be maintained. Beside the wide range of medical use, the characteristic features of magnetite nanoparticles are very interesting for basic research. The Verwey transition, a phase tran- sition at about 120 K, is well known in bulk magnetite. Our temperature-dependent XAS and XMCD measurements indicated that this transition is present also in bare nanoparticles of 6 nm. A supression of the phase transition can be achieved by a silica shell

Leadership In Learning And Teaching In Higher Education: Perspectives Of Academics In Non-Formal Leadership Roles

Developing leaders and leadership are key factors to improve learning and teaching in higher education. Despite the abundance of literature concerning developing formal leadership, fewer studies have been conducted with academics in non-formal leadership roles that focus on how they develop their leadership in learning and teaching. Publication and funding metrics are evidence of leadership and success in research. Metrics in learning and teaching exist, but are less well accepted and valued. We undertook a qualitative descriptive study to examine how academics in non-formal leadership roles at an Australian university understood leadership and described their leadership in teaching. Following ethical approval, eight participants were interviewed using a semi-structured format. Thematic analysis revealed four themes: leadership is the ability to influence direction; all about the culture; becoming visible and speaking up; and learning leadership together. Participants said leading teaching teams effectively and influencing quality learning experiences for students and colleagues is ‘evidence’ of leadership in learning and teaching. Some said a few research colleagues and formal leaders did not accept such ‘evidence’ and continued to favour leadership of research teams. This paper contributes new strategies as possible ways forward to facilitate cultural change in higher education institutions that include: a need for formal leaders and academics to reach agreement about evidence of effective leadership in learning and teaching; academics sharing innovations to effectively lead teaching teams and to promote quality teaching experiences for students; and mentoring colleagues in learning and teachin

Leadership In Learning And Teaching In Higher Education: Perspectives Of Academics In Non-Formal Leadership Roles

Developing leaders and leadership are key factors to improve learning and teaching in higher education. Despite the abundance of literature concerning developing formal leadership, fewer studies have been conducted with academics in non-formal leadership roles that focus on how they develop their leadership in learning and teaching. Publication and funding metrics are evidence of leadership and success in research. Metrics in learning and teaching exist, but are less well accepted and valued. We undertook a qualitative descriptive study to examine how academics in non-formal leadership roles at an Australian university understood leadership and described their leadership in teaching. Following ethical approval, eight participants were interviewed using a semi-structured format. Thematic analysis revealed four themes: leadership is the ability to influence direction; all about the culture; becoming visible and speaking up; and learning leadership together. Participants said leading teaching teams effectively and influencing quality learning experiences for students and colleagues is ‘evidence’ of leadership in learning and teaching. Some said a few research colleagues and formal leaders did not accept such ‘evidence’ and continued to favour leadership of research teams. This paper contributes new strategies as possible ways forward to facilitate cultural change in higher education institutions that include: a need for formal leaders and academics to reach agreement about evidence of effective leadership in learning and teaching; academics sharing innovations to effectively lead teaching teams and to promote quality teaching experiences for students; and mentoring colleagues in learning and teaching

Розвиток суспільно-політичного процесу на Волині в період незалежності

У статті розглянуто основні етапи розвитку суспільно-політичного процесу на Волині в період незалежності України. Трансформаційні процеси, що проходять в області, попри свою місцеву особливість, виходять із чергового етапу розвитку політичної системи України, а отже, розвиток суспільно-політичного процесу на Волині прямо залежний від всеукраїнського процесу трансформації.In the article the basic stages of the development of social and political process are considered in Volyn region during the period of independence of Ukraine. The transformation processes, which pass in this region, without regard to the local feature go out from the regular stage of the development of the political system of Ukraine, and consequently, the development of social and political process in Volyn region depend directly upon the all-Ukrainian process of transformation

Reversed ageing of Fe3_3O4_4 nanoparticles by hydrogen plasma

Magnetite (Fe3O4) nanoparticles suffer from severe ageing effects when exposed to air even when they are dispersed in a solvent limiting their applications. In this work, we show that this ageing can be fully reversed by a hydrogen plasma treatment. By x-ray absorption spectroscopy and its associated magnetic circular dichroism, the electronic structure and magnetic properties were studied before and after the plasma treatment and compared to results of freshly prepared magnetite nanoparticles. While aged magnetite nanoparticles exhibit a more γ-Fe2O3 like behaviour, the hydrogen plasma yields pure Fe3O4 nanoparticles. Monitoring the temperature dependence of the intra-atomic spin dipole contribution to the dichroic spectra gives evidence that the structural, electronic and magnetic properties of plasma treated magnetite nanoparticles can outperform the ones of the freshly prepared batch

Nurses Providing End-of-Life Care for Infants and Their Families in the NICU

Background: Nurses working in the neonatal intensive care unit (NICU) who care for dying infants and their families say they do not necessarily have the expertise or the specific training to provide quality end-of-life-care (EOLC). Purpose: The purpose of this review was to critically appraise the existing qualitative literature regarding nurses' experiences when caring for infants during end of life in the NICU and to identify barriers and enablers to provide quality EOLC. Search Strategy: A literature search was conducted using CINAHL and OVID databases. Studies that explored nurses' experiences when caring for infants who were dying or when lifesaving care was withdrawn were retrieved and 15 studies were thematically analyzed. Results: Five major themes emerged: advocating for the dying infant, building close relationships with the family, providing an appropriate care environment, nurses' emotional responses to dying or death, and professional inadequacy in EOLC. Implications for Practice: Nurses face multiple challenges when providing EOLC including moral dilemmas and feelings of professional inadequacy. Avoidance was a common strategy used by nurses to cope with the stress associated with EOLC. Managers can foster quality EOLC by implementing education sessions about infant mortality, EOLC, advocacy, team communication, and self-care practices

How the surface affects the electronic and magnetic properties of magnetite nanoparticles

Magnetite (Fe3O4) nanoparticles are objects of intense research activities due to their broad range of applications covering technological, medical, and environmental applications. They are used e.g. for rotary shaft sealing, oscillation damping, position sensing, magnetic inks for jet printing, as contrast agents in magnetic resonance imaging, and to remove heavy metals from wastewater. In addition, magnetite is a half-metal with a predicted negative spin polarisation making magnetite interesting for spintronics. For all applications, a high quality of magnetite is crucial to obtain the desired properties. In this work, we studied the influence of the surface on the electronic and magnetic properties of magnetite nanoparticles by means of x-ray absorption near-edge spectroscopy (XANES) and its associated magnetic circular dichroism (XMCD). In particular, we investigated ensembles of magnetite nanoparticles with a mean diameter of 3nm, 6nm or 9nm and the influence of capping the particles with a 3nm thick silica shell or organic ligands. XANES and XMCD gives the unique possibility to distinguish between the three different Fe species in magnetite, i.e. tetrahedrally coordinated Fe3+ ions, octahedrally coordinated Fe3+, and octahedrally coordinated Fe2+, by using different photon energies for hysteresis measurements. Besides changes in the electronic structure, i.e. in the density of unoccupied 3d states monitored by XANES, and the effective spin magnetic moments, we obtained a different spin canting behaviour of Fe ions in magnetite at different lattice sites from the magnetic field dependent XMCD as shown in the figure below. The results are discussed regarding different exchange mechanisms and possible advantages and drawbacks for applications. Measurements were performed at beamline UE46-PGM1, HZB – BESSY II synchrotron radiation facility. We thank the BESSY II staff for kind support during beamtimes. Financially supported by BMBF (05 ES3XBA/5) and DFG (WE2623/3-1)

Il y a 70 ans, Auschwitz. Retour sur Primo Levi

27 janvier 1945. Il y a 70 ans les premiers soldats de l’Armée rouge pénétraient dans le camp d’Auschwitz marquant définitivement ce que l’on pourrait appeler sa « libération », bien qu’Auschwitz n’ait été, pas plus qu’aucun autre camp nazi, un objectif prioritaire pour aucune des forces alliées. Primo Levi faisait partie des quelques rescapés qui, échappant aux évacuations forcées, étaient restés cachés à Auschwitz. Juif, déporté, chimiste, témoin, écrivain, retour sur cette personnalité complexe, sur son ascension vers ce qu’il a appelé le « rescapé professionnel », sur son œuvre. Sur ce que les mots « résistance », « engagement » ont signifié pour lui. 27 januari 1945. Zeventig jaar geleden wandelden de eerste soldaten van het Rode Leger Auschwitz binnen. Men zou kunnen zeggen dat het kamp toen werd ‘bevrijd’, hoewel Auschwitz, en geen enkel ander nazikamp, ooit een prioriteit vormden voor de Geallieerden. Primo Levi was een van de weinige overlevenden die zich wisten te verbergen en zo ontsnapten aan de gedwongen evacuaties. Jood, gedeporteerde, chemicus, getuige, schrijver: we blikken terug op deze complexe figuur, op zijn evolutie tot wat hij zelf een ‘professionele overlevende’ noemde, op zijn oeuvre. En op de betekenis die hij aan de woorden ‘verzet’ en ‘engagement’ gaf. 27 January 1945. Seventy years ago the first soldiers of the Red Army marched into Auschwitz. One might argue that the camp was “liberated” then, but the truth is that neither Auschwitz, nor any of the other Nazi camps, was ever a priority to the Allied Powers. Primo Levi was one of the few survivors who knew how to hide and escape the enforced evacuation of the camps. With this dossier, we want to cast light on the complex figure that Levi was: a Jew, a deportee, a chemists, a witness, and a writer. It sets out to study his oeuvre and his interpretation of the notions of “resistance” and “engagement”, in order to understand how he eventually became a “professional survivor”, as he once described himself