Epitaxial Iron Oxide Growth on Vicinal Pt(111): Well-defined defective model systems?

Heterogeneous catalysts consist often of metals in contact with oxides and the activity depends on the interaction between them. In addition, the defect structure of the surface is of high importance for the catalytic activity. The common electron-based surface science techniques allow the characterization of model catalyst surfaces with atomic precision. Studied model catalyst systems include single crystal surfaces, epitaxial compound films, or well-defined particles deposited on single-crystalline supports. However, real catalysts contains a defect structure which is difficult to model in a well-defined manner. In order to study the controlled introduction of defects into iron oxide model catalysts for the dehydrogenation of ethylbenzene to styrene, we have grown different iron oxide phases on a stepped Pt(9 11 11) single crystal surface. The hope was that this may provide a way to introduce well-defined step defects into the epitaxially grown films. For coverages below 1 ML, FeO(111) films wet the vicinal Pt substrate. The step structure changes under formation of doubled and triplicated terrace widths and step heights. Further cycles of iron deposition and oxidation lead to a Stranski-Krastanov-type growth of Fe3O4(111) islands which initially are elongated along the edge direction. However, the morphology of a coalesced closed film is almost unaffected by the underlying substrate step morphology. High pressure oxidation of Fe3O4 films results in poorly defined Fe2O3(0001). Although FeO films grown on the vicinal Pt surface may serve as model systems for systematic studies of well-defined defective oxide surfaces, the catalytically more relevant Fe3O4 and Fe2O3 phases could not be obtained reproducibly with a well-defined defect structure

Interface-dependence of Nucleation and Self-Assembly of Ultrathin Iron Oxide Films

The interface-dependence of heteroepitaxial growth of iron oxide films is investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). We show that the different chemical affinity to the metal substrate (Ru vs. Pt) and the step density (basal vs. vicinal Pt) significantly influence nucleation, heteroepitaxial crystal growth, and adhesion. Repeated Fe deposition-oxidation cycles lead to a Stranski-Krastanov growth mode on all substrates. On Ru(0001), metastable FeO(111) layers with strongly expanded lattice constants with a thickness up to 4 monolayers (ML) can be obtained by one-minute oxidation of the corresponding amount of Fe. Homogeneous nucleation of self-assembled, periodic Fe3O4(111) nanodomains embedded in an ultrathin FeO(111) film occurs on Ru(0001) in ~4 ML thick FeO(111) films. Nucleation of Fe3O4(111) islands below 4 ML on Ru(0001) occurs preferentially at substrate step edges while on Pt(111), no influence of surface defects was observed. On a vicinal Pt substrate, the terrace width and step height triplicates under influence of the wetting FeO(111) film. Differences in the growth behavior are discussed in terms of the involved surface and interface free energies

Drama education in New Zealand schools: the practice of six experienced drama teachers

This research investigates drama teaching practice in New Zealand primary and secondary schools, through a case-based qualitative inquiry into the practice of six experienced drama teachers. The study reveals that whilst drama education is couched within the Arts learning area of the national curriculum, the educational philosophy enacted by participants encompasses a broad vision for drama education, which extends learning beyond a technical knowledge of theatre and theatre-making towards the domains of social and personal meaning-making and emancipatory knowledge. Explored through the lenses of Artist and Co-artist, the study identifies the socio-cultural nature of the practice of these teachers. Teachers’ artistry is revealed through creative use of drama tools and processes to create aesthetically-rich learning experiences. The significance of relational pedagogy to teaching and learning in these drama classrooms is also examined within the study. Teachers’ accounts reveal the ways they seek to develop interpersonal relationships with and between students, and establish ensemble-based approaches to learning in drama. As co-artists, participants employ pedagogies that empower students to actively participate in a community of drama practice, intentionally developing students’ capacities for collaboration, creativity and critical thinking, while discovering and developing their artistic-aesthetic capabilities. These teachers share power with students through acts of negotiation, creating dialogic learning opportunities in order to develop student agency as artists and citizens. Attempts to navigate tensions that arise due to increased performativity pressures on teachers and to avoid prescriptive and technocratic delivery of drama curriculum are also explored. In-depth interviews were conducted with participants to discover the complexities of their teaching practice, the philosophy of drama education they hold, and the decisions they make in curriculum content and pedagogy. Observations of classroom practice were also undertaken, along with an analysis of planning documents and an interview with their students. The study provides six rich case studies of drama practice in New Zealand schools, contributing to local and international understandings of enacted drama education within school settings. Implications for educational policy, curriculum design, classroom practice and teacher education arise from this investigation

Oxide nanotemplates for self-assembling "solid" building blocks

It is widely accepted that self-assembling building blocks is one of the promising ways for engineering new materials. Recent years reveal substantial progress in fabricating colloidal particles, polymer blocks and supramolecular aggregates of organic molecules. Despite of substantial progress in molecular self-assembly there is still a lack of simple blocks made of "solid matter" (e.g. metals, oxides etc.) with well-defined crystal structure and spatial order. Here we demonstrate that ordered arrays of metal nanoclusters can be fabricated by self-assembly on a wide range of oxide templates. These nano-templates are produced either by depositing an alien oxide film or by oxidizing a metal/metal oxide substrate.Comment: 11 pages, 2 figures added DFT calculations and Fig.

Identification and functional validation of FDA-approved positive and negative modulators of the mitochondrial calcium uniporter

The mitochondrial calcium uniporter (MCU), the highly selective channel responsible for mitochondrial Ca2+ entry, plays important roles in physiology and pathology. However, only few pharmacological compounds directly and selectively modulate its activity. Here, we perform high-throughput screening on a US Food and Drug Administration (FDA)-approved drug library comprising 1,600 compounds to identify molecules modulating mitochondrial Ca2+ uptake. We find amorolfine and benzethonium to be positive and negative MCU modulators, respectively. In agreement with the positive effect of MCU in muscle trophism, amorolfine increases muscle size, and MCU silencing is sufficient to blunt amorolfine-induced hypertrophy. Conversely, in the triple-negative breast cancer cell line MDA-MB-231, benzethonium delays cell growth and migration in an MCU-dependent manner and protects from ceramide-induced apoptosis, in line with the role of mitochondrial Ca2+ uptake in cancer progression. Overall, we identify amorolfine and benzethonium as effective MCU-targeting drugs applicable to a wide array of experimental and disease conditions

Transcriptional co-activators YAP1-TAZ of Hippo signalling in doxorubicin-induced cardiomyopathy

Aims Hippo signalling is an evolutionarily conserved pathway that controls organ size by regulating apoptosis, cell proliferation, and stem cell self-renewal. Recently, the pathway has been shown to exert powerful growth regulatory activity in cardiomyocytes. However, the functional role of this stress-related and cell death-related pathway in the human heart and cardiomyocytes is not known. In this study, we investigated the role of the transcriptional co-activators of Hippo signalling, YAP and TAZ, in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in response to cardiotoxic agents and investigated the effects of modulating the pathway on cardiomyocyte function and survival. Methods and results RNA-sequencing analysis of human heart samples with doxorubicin-induced end-stage heart failure and healthy controls showed that YAP and ERBB2 (HER2) as upstream regulators of differentially expressed genes correlated with doxorubicin treatment. Thus, we tested the effects of doxorubicin on hiPSC-CMs in vitro. Using an automated high-content screen of 96 clinically relevant antineoplastic and cardiotherapeutic drugs, we showed that doxorubicin induced the highest activation of YAP/TAZ nuclear translocation in both hiPSC-CMs and control MCF7 breast cancer cells. The overexpression of YAP rescued doxorubicin-induced cell loss in hiPSC-CMs by inhibiting apoptosis and inducing proliferation. In contrast, silencing of YAP and TAZ by siRNAs resulted in elevated mitochondrial membrane potential loss in response to doxorubicin. hiPSC-CM calcium transients did not change in response to YAP/TAZ silencing. Conclusions Our results suggest that Hippo signalling is involved in clinical anthracycline-induced cardiomyopathy. Modelling with hiPSC-CMs in vitro showed similar responses to doxorubicin as adult cardiomyocytes and revealed a potential cardioprotective effect of YAP in doxorubicin-induced cardiotoxicity