ABSTRACT
We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.
ABSTRACT
We have studied the magnetic layer thickness dependence of the orbital magnetic moment in magnetic heterostructures to identify contributions from interfaces. Three different heterostructures, Ta/CoFeB/MgO, Pt/Co/AlOx and Pt/Co/Pt, which possess significant interface contribution to the perpendicular magnetic anisotropy, are studied as model systems. X-ray magnetic circular dichroism spectroscopy is used to evaluate the relative orbital moment, i.e. the ratio of the orbital to spin moments, of the magnetic elements constituting the heterostructures. We find that the relative orbital moment of Co in Pt/Co/Pt remains constant against its thickness whereas the moment increases with decreasing Co layer thickness for Pt/Co/AlOx, suggesting that a non-zero interface orbital moment exists for the latter system. For Ta/CoFeB/MgO, a non-zero interface orbital moment is found only for Fe. X-ray absorption spectra shows that a particular oxidized Co state in Pt/Co/AlOx, absent in other heterosturctures, may give rise to the interface orbital moment in this system. These results show element specific contributions to the interface orbital magnetic moments in ultrathin magnetic heterostructures.
ABSTRACT
We have constructed an end station for nanoscale magnetic materials study at the soft X-ray beamline HiSOR BL-14 at Hiroshima Synchrotron Radiation Center. An ultrahigh-vacuum scanning tunneling microscope (STM) was installed for an in situ characterization of nanoscale magnetic materials in combination with soft X-ray magnetic circular dichroism (XMCD) spectroscopy experiment. The STM was connected to the XMCD experimental station via damper bellows to isolate it from environmental vibrations, thus achieving efficient spatial resolution for observing Si(111) surface at atomic resolution. We performed an in situ experiment with STM and XMCD spectroscopy on Co nanoclusters on an Au(111) surface and explored its practical application to investigate magnetic properties for well-characterized nanoscale magnetic materials.
ABSTRACT
Choriogenins (chg-H, chg-L) are precursor proteins of egg envelope of medaka and synthesized in the spawning female liver in response to estrogen. We linked a gene construct chg-L1.5 kb/GFP (a 1.5 kb 5'-upstream region of the chg-L gene fused with a green fluorescence protein (GFP) gene) to another construct emgb/RFP (a cis-regulatory region of embryonic globin gene fused with an RFP gene), injected the double fusion gene construct into 1- or 2-cell-stage embryos, and selected embryos expressing the RFP in erythroid cells. From the embryos, we established two lines of chg-L1.5 kb/GFP-emgb/RFP-transgenic medaka. The 3-month-old spawning females and estradiol-17beta (E2)-exposed males displayed the liver-specific GFP expression. The E2-dependent GFP expression was detected in the differentiating liver of the stage 37-38 embryos. In addition, RT-PCR and whole-mount in situ hybridization showed that the E2-dependent chg expression was found in the liver of the stage 34 embryos of wild medaka, suggesting that such E2-dependency is achieved shortly after differentiation of the liver. Analysis using serial deletion mutants fused with GFP showed that the region -426 to -284 of the chg-L gene or the region -364 to -265 of the chg-H gene had the ability to promote the E2-dependent liver-specific GFP expression of its downstream gene. Further analyses suggested that an estrogen response element (ERE) at -309, an ERE half-site at -330 and a binding site for C/EBP at -363 of the chg-L gene played important roles in its downstream chg-L gene expression. In addition, this transgenic medaka may be useful as one of the test animals for detecting environmental estrogenic steroids.
Subject(s)
Egg Proteins/genetics , Estrogens/metabolism , Fish Proteins/genetics , Genes, Regulator , Liver/metabolism , Oryzias/genetics , Protein Precursors/genetics , Animals , Animals, Genetically Modified , Female , Male , Molecular Sequence Data , Oryzias/embryology , Promoter Regions, Genetic , Sequence Analysis, DNAABSTRACT
Cell adhesion was studied during primary embryonic induction. The disaggregation rate and reaggregation patterns were analysed in the ectoderm cells of various developing Cynopus gastrulae and neurulae. The neurectoderm cells disaggregated more slowly with gastrulation, and the neural plate cells of early neurula showed a lesser capacity for disaggregation. Although no differences in reaggregation were found between dorsal and ventral ectoderm at the early gastrula stage, there were significant differences between the induced neurectoderm and the non-induced ventral epidermal cells at the late gastrula stage. Neural plate cells of the early neurula stage were seen to form a chain-like reaggregate, but the ventral epidermal cells of the same embryo formed a cluster-like spherical reaggregate. Scanning electron microscope observations of reaggregates also showed significant differences in adhesive properties between induced neurectoderm and non-induced epidermal cells. The adhesion field of the induced neurectoderm cells was smooth, differing from the distinct ridges of the non-induced epidermal cells. These results suggest that changes in the cell adhesion system, resulting in the formation of a columnar cell shape, may occur immediately after a neural-inducing action.
