1,180 research outputs found
Recommended from our members
Reaustenitisation from Bainite in Steels
SIGLEAvailable from British Library Document Supply Centre- DSC:D062865 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
An ab initio study of 3s core-level x-ray photoemission spectra in transition metals
We calculate the - and -core-level x-ray photoemission spectroscopy
(XPS) spectra in the ferromagnetic and nonmagnetic transition metals by
developing an \emph{ab initio} method. We obtain the spectra exhibiting the
characteristic shapes as a function of binding energy in good agreement with
experimental observations. The spectral shapes are strikingly different between
the majority spin channel and the minority spin channel for ferromagnetic
metals Ni, Co, and Fe, that is, large intensities appear in the higher binding
energy side of the main peak (satellite) in the majority spin channel. Such
satellite or shoulder intensities are also obtained for nonmagnetic metals V
and Ru. These behaviors are elucidated in terms of the change of the
one-electron states induced by the core-hole potential.Comment: 11 pages, 12 figures, to appear in Phys. Rev.
Theory of resonant inelastic x-ray scattering at the K edge in LaCuO - Multiple scattering effects -
We develop a theory of resonant inelastic x-ray scattering (RIXS) at the
edge in LaCuO on the basis of the Keldysh Green's function formalism.
In our previous analysis (Phys. Rev. B 71, 035110 (2005)), the scattering by
the core-hole potential was treated within the Born approximation, and a
crude-model density of states was used for the band. We improve the
analysis by taking account of the multiple scattering in Cu3d-O bands and
by using a realistic DOS obtained from a band calculation. The multiple
scattering effect is evaluated with the use of the time representation
developed by Nozi\`eres and De Dominicis. It is found that the multiple
scattering effect makes the -edge peak in the absorption coefficient shift
to the lower energy region as a function of photon energy, that is, the photon
energy required to excite the electron to the -edge peak reduces. It is
also found that the multiple-scattering effect does not change the two-peak
structure in the RIXS spectra but modifies slightly the shape as a function of
energy loss. These findings suggests that the multiple scattering effect could
mainly be included into a renormalization of the core-level energy and partly
justify the Born approximation, leading to a future application to the RIXS in
three-dimensional systems.Comment: revised version with extended discussion, 24 pages, 12 figures,
accepted for PR
The Influence of Polyploidy and Genome Composition on Genomic Imprinting in Mice
Genomic imprinting is an epigenetic mechanism that switches the expression of imprinted genes involved in normal embryonic growth and development in a parent-of-origin-specific manner. Changes inDNAmethylation statuses from polyploidization are a well characterized epigenetic modification in plants. However, how changes in ploidy affect both imprinted gene expression and methylation status in mammals remains unclear. To address this, we used quantitative real time PCR to analyze expression levels of imprinted genes in mouse tetraploid fetuses. We used bisulfite sequencing to assess the methylation statuses of differentially methylated regions (DMRs) that regulate imprinted gene expression in triploid and tetraploid fetuses. The nine imprinted genes H19, Gtl2, Dlk1, Igf2r, Grb10, Zim1, Peg3, Ndn, and Ipw were all unregulated; in particular, the expression of Zim1 was more than 10-fold higher, and the expression of Ipw was repressed in tetraploid fetuses. The methylation statuses of four DMRs H19, intergenic (IG), Igf2r, and Snrpn in tetraploid and triploid fetuses were similar to those in diploid fetuses. We also performed allele-specific RT-PCR sequencing to determine the alleles expressing the three imprinted genes Igf2, Gtl2, and Dlk1 in tetraploid fetuses. These three imprinted genes showed monoallelic expression in a parent-of-origin-specific manner. Expression of non-imprinted genes regulating neural cell development significantly decreased in tetraploid fetuses, which might have been associated with unregulated imprinted gene expression. This study provides the first detailed analysis of genomic imprinting in tetraploid fetuses, suggesting that imprinted gene expression is disrupted, but DNA methylation statuses of DMRs are stable following changes in ploidy in mammals
- …