Ferroelectric polarization switching with a remarkably high activation energy in orthorhombic GaFeO3 thin films

This work was supported by the National Research Foundation (NRF) Grants funded by the Korea Government (MSIP) (Grant No. 2012R 1A1A2041628 and 2013R 1A2A2A01068274). The work at Cambridge was supported by the Engineering and Physical Sciences Research Council (EPSRC). AG and RG thank the Department of Science and Technology for the financial support (Grant No. SB/S3/ME/29/2013).Orthorhombic GaFeO3 (o-GFO) with the polar Pna21 space group is a prominent ferrite owing to its piezoelectricity and ferrimagnetism, coupled with magnetoelectric effects. Herein, we demonstrate large ferroelectric remanent polarization in undoped o-GFO thin films by adopting either a hexagonal strontium titanate (STO) or a cubic yttrium-stabilized zirconia (YSZ) substrate. The polarization-electric-field hysteresis curves of the polar c-axis-grown o-GFO film on a SrRuO3/STO substrate show the net switching polarization of ~35 μC cm−2 with an unusually high coercive field (Ec) of ±1400 kV cm−1 at room temperature. The positive-up and negative-down measurement also demonstrates the switching polarization of ~26 μC cm−2. The activation energy for the polarization switching, as obtained by density-functional theory calculations, is remarkably high, 1.05 eV per formula unit. We have theoretically shown that this high value accounts for the extraordinary high Ec and the stability of the polar Pna21 phase over a wide range of temperatures up to 1368 K.Publisher PDFPeer reviewe

Uncovering Suitable Reference Proteins for Expression Studies in Human Adipose Tissue with Relevance to Obesity

Protein expression studies based on the two major intra-abdominal human fat depots, the subcutaneous and the omental fat, can shed light into the mechanisms involved in obesity and its co-morbidities. Here we address, for the first time, the identification and validation of reference proteins for data standardization, which are essential for accurate comparison of protein levels in expression studies based on fat from obese and non-obese individuals.To uncover adipose tissue proteins equally expressed either in omental and subcutaneous fat depots (study 1) or in omental fat from non-obese and obese individuals (study 2), we have reanalyzed our previously published data based on two-dimensional fluorescence difference gel electrophoresis. Twenty-four proteins (12 in study 1 and 12 in study 2) with similar expression levels in all conditions tested were selected and identified by mass spectrometry. Immunoblotting analysis was used to confirm in adipose tissue the expression pattern of the potential reference proteins and three proteins were validated: PARK7, ENOA and FAA. Western Blot analysis was also used to test customary loading control proteins. ENOA, PARK7 and the customary loading control protein Beta-actin showed steady expression profiles in fat from non-obese and obese individuals, whilst FAA maintained steady expression levels across paired omental and subcutaneous fat samples.ENOA, PARK7 and Beta-actin are proper reference standards in obesity studies based on omental fat, whilst FAA is the best loading control for the comparative analysis of omental and subcutaneous adipose tissues either in obese and non-obese subjects. Neither customary loading control proteins GAPDH and TBB5 nor CALX are adequate standards in differential expression studies on adipose tissue. The use of the proposed reference proteins will facilitate the adequate analysis of proteins differentially expressed in the context of obesity, an aim difficult to achieve before this study

Electrical half-wave rectification at ferroelectric domain walls

Ferroelectric domain walls represent multifunctional 2D-elements with great potential for novel device paradigms at the nanoscale. Improper ferroelectrics display particularly promising types of domain walls, which, due to their unique robustness, are the ideal template for imposing specific electronic behavior. Chemical doping, for instance, induces p- or n-type characteristics and electric fields reversibly switch between resistive and conductive domain-wall states. Here, we demonstrate diode-like conversion of alternating-current (AC) into direct-current (DC) output based on neutral 180$^{\circ}$ domain walls in improper ferroelectric ErMnO$_3$. By combining scanning probe and dielectric spectroscopy, we show that the rectification occurs for frequencies at which the domain walls are fixed to their equilibrium position. The practical frequency regime and magnitude of the output is controlled by the bulk conductivity. Using density functional theory we attribute the transport behavior at the neutral walls to an accumulation of oxygen defects. Our study reveals domain walls acting as 2D half-wave rectifiers, extending domain-wall-based nanoelectronic applications into the realm of AC technology

Stepped care for depression and anxiety: from primary care to specialized mental health care: a randomised controlled trial testing the effectiveness of a stepped care program among primary care patients with mood or anxiety disorders

ABSTRACT: BACKGROUND: Mood and anxiety disorders are highly prevalent and have a large impact on the lives of the affected individuals. Therefore, optimal treatment of these disorders is highly important. In this study we will examine the effectiveness of a stepped care program for primary care patients with mood and anxiety disorders. A stepped care program is characterized by different treatment steps that are arranged in order of increasing intensity. METHODS: This study is a randomised controlled trial with two conditions: stepped care and care as usual, whereby the latter forms the control group. The stepped care program consists of four evidence based interventions: (1) Watchful waiting, (2) Guided self-help, (3) Problem Solving Treatment and (4) Medication and/or specialized mental health care. The study population consists of primary care attendees aged 18-65 years. Screeners are sent to all patients of the participating general practitioners. Individuals with a Diagnostic and Statistical Manual of mental disorders (DSM) diagnosis of major depression, dysthymia, panic disorder (with or without agoraphobia), generalized anxiety disorder, or social phobia are included as well as individuals with minor depression and anxiety disorders. Primary focus is the reduction of depressive and anxiety symptoms. Both conditions are monitored at 8, 16 and 24 weeks. DISCUSSION: This study evaluates the effectiveness of a stepped care program for patients with depressive and anxiety disorder. If effective, a stepped care program can form a worthwhile alternative for care as usual. Strengths and limitations of this study are discussed. Trial registration: Current Controlled Trails: ISRCTN1783161

Trophic Ecology of Atlantic Bluefin Tuna (Thunnus thynnus) Larvae from the Gulf of Mexico and NW Mediterranean Spawning Grounds: A Comparative Stable Isotope Study

The present study uses stable isotopes of nitrogen and carbon (δ15Nandδ13C) as trophic indicators for Atlantic bluefin tuna larvae (BFT) (6–10mm standard length) in the highly contrasting environmental conditions of the Gulf of Mexico (GOM) and the Balearic Sea (MED). These regions are differentiated by their temperature regime and relative productivity, with the GOM being significantly warmer and more productive. MED BFT larvae showed the highest δ15N signatures, implying an elevated trophic position above the underlyingmicrozooplankton baseline. Ontogenetic dietary shifts were observed in the BFT larvae from the GOM and MED which indicates early life trophodynamics differences between these spawning habitats. Significant trophic differences between the GOM and MED larvae were observed in relation to δ15N signatures in favour of the MED larvae, which may have important implications in their growth during their early life stages. These low δ15N levels in the zooplankton from the GOM may be an indication of a shifting isotopic baseline in pelagic food webs due to diatrophic inputs by cyanobacteria. Lack of enrichment for δ15N in BFT larvae compared to zooplankton implies an alternative grazing pathway from the traditional food chain of phytoplankton— zooplankton—larval fish. Results provide insight for a comparative characterization of the trophic pathways variability of the two main spawning grounds for BFT larvaeVersión del editor4,411

Are ribosomal DNA clusters rearrangement hotspots? A case study in the genus Mus (Rodentia, Muridae)

<p>Abstract</p> <p>Background</p> <p>Recent advances in comparative genomics have considerably improved our knowledge of the evolution of mammalian karyotype architecture. One of the breakthroughs was the preferential localization of evolutionary breakpoints in regions enriched in repetitive sequences (segmental duplications, telomeres and centromeres). In this context, we investigated the contribution of ribosomal genes to genome reshuffling since they are generally located in pericentromeric or subtelomeric regions, and form repeat clusters on different chromosomes. The target model was the genus <it>Mus </it>which exhibits a high rate of karyotypic change, a large fraction of which involves centromeres.</p> <p>Results</p> <p>The chromosomal distribution of rDNA clusters was determined by <it>in situ </it>hybridization of mouse probes in 19 species. Using a molecular-based reference tree, the phylogenetic distribution of clusters within the genus was reconstructed, and the temporal association between rDNA clusters, breakpoints and centromeres was tested by maximum likelihood analyses. Our results highlighted the following features of rDNA cluster dynamics in the genus <it>Mus</it>: i) rDNA clusters showed extensive diversity in number between species and an almost exclusive pericentromeric location, ii) a strong association between rDNA sites and centromeres was retrieved which may be related to their shared constraint of concerted evolution, iii) 24% of the observed breakpoints mapped near an rDNA cluster, and iv) a substantial rate of rDNA cluster change (insertion, deletion) also occurred in the absence of chromosomal rearrangements.</p> <p>Conclusions</p> <p>This study on the dynamics of rDNA clusters within the genus <it>Mus </it>has revealed a strong evolutionary relationship between rDNA clusters and centromeres. Both of these genomic structures coincide with breakpoints in the genus <it>Mus</it>, suggesting that the accumulation of a large number of repeats in the centromeric region may contribute to the high level of chromosome repatterning observed in this group. However, the elevated rate of rDNA change observed in the chromosomally invariant clade indicates that the presence of these sequences is insufficient to lead to genome instability. In agreement with recent studies, these results suggest that additional factors such as modifications of the epigenetic state of DNA may be required to trigger evolutionary plasticity.</p