Cerebral gene expression in response to single or combined gestational exposure to methylmercury and selenium through the maternal diet

Controversy remains regarding the safety of consuming certain types of seafood, particularly during pregnancy. While seafood is rich in vital nutrients, it may also be an important source of environmental contaminants such as methylmercury (MeHg). Selenium (Se) is one essential element present in seafood, hypothesised to ameliorate MeHg toxicity. The aim of the present study was to ascertain the impact of Se on MeHg-induced cerebral gene expression in a mammalian model. Microarray analysis was performed on brain tissue from 15-day-old mice that had been exposed to MeHg throughout development via the maternal diet. The results from the microarray analysis were validated using qPCR. The exposure groups included: MeHg alone (2.6 mg kg−1), Se alone (1.3 mg kg−1), and MeHg + Se. MeHg was presented in a cysteinate form, and Se as Se–methionine, one of the elemental species occurring naturally in seafood. Eight genes responded to Se exposure alone, five were specific to MeHg, and 63 were regulated under the concurrent exposure of MeHg and Se. Significantly enriched functional classes relating to the immune system and cell adhesion were identified, highlighting potential ameliorating mechanisms of Se on MeHg toxicity. Key developmental genes, such as Wnt3 and Sparcl1, were also identified as putative ameliorative targets. This study, utilising environmentally realistic forms of toxicants, delivered through the natural route of exposure, in association with the power of transcriptomics, highlights significant novel information regarding putative pathways of selenium and MeHg interaction in the mammalian brain

Enhanced magnetic signal along edges of embedded epitaxial La0.7Sr0.3MnO3 nanostructures

When thin films are patterned to realize nanoscale device geometries, maintaining their structural integrity is key to the quality of their functional properties. The introduction of new surfaces and interfaces by lateral modifications may alter material properties as well as the expected device functionality. In this study, two different techniques for nanoscale patterning of epitaxial thin films of La0.7Sr0.3MnO3 are used to investigate the effects on their ferromagnetic properties and film crystalline structure. Nanomagnets are realized as free-standing structures and embedded ferromagnets in a paramagnetic matrix, respectively. We find that the magnetic dichroism signal in x-ray spectomicroscopy is stronger along the edges of the embedded magnets close to TC. X-ray-diffraction measurements reveal a reduction of their in-plane lattice parameters. We discuss how in-plane stress from the nanomagnet surroundings can affect the magnetic properties in these structures

Shape-imposed anisotropy in antiferromagnetic complex oxide nanostructures

In this study, we report on a shape-imposed magnetic anisotropy in micro- and nanostructures defined in antiferromagnetic (AF) LaFeO3 (LFO) thin films. Two distinct types of structures are investigated: embedded magnets created via ion implantation and free-standing magnets created via ion milling. Using a combination of x-ray photoemission electron microscopy and x-ray absorption spectroscopy, we examine the impact of the structure type, AF layer thickness, and crystal geometry on the Néel vector orientation in these structures. We demonstrate a distinct shape-imposed anisotropy in embedded and free-standing structures alike and show that both parallel and perpendicular alignments of the AF spin axis with respect to structure edges can be achieved by variation of the AF layer thickness and the orientation of the structure edges with respect to the LFO crystalline axes. This work demonstrates how the fabrication procedure affects the magnetic order in thin film AF nanostructures and shows how nanoscale patterning can be used to control the orientation of the Néel vector in epitaxial oxide thin films

Enhanced magnetic signal along edges of embedded epitaxial La0.7Sr0.3MnO3 nanostructures

When thin films are patterned to realize nanoscale device geometries, maintaining their structural integrity is key to the quality of their functional properties. The introduction of new surfaces and interfaces by lateral modifications may alter material properties as well as the expected device functionality. In this study, two different techniques for nanoscale patterning of epitaxial thin films of La0.7Sr0.3MnO3 are used to investigate the effects on their ferromagnetic properties and film crystalline structure. Nanomagnets are realized as free-standing structures and embedded ferromagnets in a paramagnetic matrix, respectively. We find that the magnetic dichroism signal in x-ray spectomicroscopy is stronger along the edges of the embedded magnets close to TC. X-ray-diffraction measurements reveal a reduction of their in-plane lattice parameters. We discuss how in-plane stress from the nanomagnet surroundings can affect the magnetic properties in these structures

Effects of array shape and disk ellipticity in dipolar-coupled magnetic metamaterials

Two-dimensional lattices of dipolar-coupled thin film ferromagnetic nanodisks give rise to emergent superferromagnetic (SFM) order when the spacing between dots becomes sufficiently small. In this paper, we define micron-sized arrays of permalloy nanodisks arranged on a hexagonal lattice. The arrays were shaped as hexagons, squares, and rectangles to investigate finite-size effects in the SFM domain structure for such arrays. The resulting domain patterns were examined using x-ray magnetic circular dichroism photoemission electron microscopy. At room temperature, we find these SFM metamaterials to be below their blocking temperature. Distinct differences were found in the magnetic switching characteristics of horizontally and vertically oriented rectangular arrays. The results are corroborated by micromagnetic simulations

Temperature dependence of ferromagnet-antiferromagnet spin alignment and coercivity in epitaxial micromagnet bilayers

Soft x-ray photoemission electron microscopy with an in situ magnetic field has been used to study the relationship between ferromagnetic and antiferromagnetic spin alignment and the switching/reversal field of epitaxial micromagnetic structures. We investigated a model system consisting of a bilayer of ferromagnetic La0.7Sr0.3MnO3 and antiferromagnetic LaFeO3 where the spin axes in each layer can be driven from mutually perpendicular (spin-flop) to parallel alignment by varying the temperature between 30 and 300 K. Results show that not only does this spin alignment noticeably influence the bilayer micromagnet coercivity compared to La0.7Sr0.3MnO3 single-layer micromagnets, but the coercivity within this materials system can be tuned over a wide range by careful balance of material properties

Magnetic domain configuration of (111)-oriented LaFeO3 epitaxial thin films

In antiferromagnetic spintronics control of the domains and corresponding spin axis orientation is crucial for devices. Here we investigate the antiferromagnetic axis in (111)-oriented LaFeO3/SrTiO3, which is coupled to structural twin domains. The structural domains have either the orthorhombic a- or b-axis along the in-plane ⟨11⎯⎯⎯0⟩ cubic directions of the substrate, and the corresponding magnetic domains have the antiferromagnetic axis in the sample plane. Six degenerate antiferromagnetic axes are found corresponding to the ⟨11⎯⎯⎯0⟩ and ⟨112⎯⎯⎯⟩ in-plane directions. This is in contrast to the biaxial anisotropy in (001)-oriented films and reflects how crystal orientation can be used to control magnetic anisotropy in antiferromagnets.publishedVersio