1,379 research outputs found
Covariation of Pluripotency Markers and Biomechanical Properties in Mouse Embryonic Stem Cells
Hole-depletion of ladders in SrCuO induced by correlation effects
The hole distribution in SrCuO is studied by low
temperature polarization dependent O K Near-Edge X-ray Absorption Fine
Structure measurements and state of the art electronic structure calculations
that include core-hole and correlation effects in a mean-field approach.
Contrary to all previous analysis, based on semi-empirical models, we show that
correlations and antiferromagnetic ordering favor the strong chain
hole-attraction. For the remaining small number of holes accommodated on
ladders, leg-sites are preferred to rung-sites. The small hole affinity of
rung-sites explains naturally the 1D - 2D cross-over in the phase diagram of
(La,Y,Sr,Ca)CuOComment: 6 pages, 8 figure
Single 3 transition metal atoms on multi-layer graphene systems: electronic configurations, bonding mechanisms and role of the substrate
The electronic configurations of Fe, Co, Ni, and Cu adatoms on graphene and
graphite have been studied by x-ray magnetic circular dichroism and charge
transfer multiplet theory. A delicate interplay between long-range interactions
and local chemical bonding is found to influence the adatom equilibrium
distance and magnetic moment. The results for Fe and Co are consistent with
purely physisorbed species having, however, different 3-shell occupancies on
graphene and graphite ( and , respectively). On the other hand,
for the late 3 metals Ni and Cu a trend towards chemisorption is found,
which strongly quenches the magnetic moment on both substrates.Comment: 7 pages, 4 figure
Subfractions of enamel matrix derivative differentially influence cytokine secretion from human oral fibroblasts.
Enamel matrix derivative is used to promote periodontal regeneration during the corrective phase of the treatment of periodontal defects. Our main goal was to analyze the bioactivity of different molecular weight fractions of enamel matrix derivative. Enamel matrix derivative, a complex mixture of proteins, was separated into 13 fractions using size-exclusion chromatography and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and liquid chromatography-electrospray ionization-tandem mass spectrometry. Human periodontal ligament fibroblasts were treated with either enamel matrix derivative or the different fractions. Proliferation and cytokine secretion to the cell culture medium were measured and compared to untreated cells. The liquid chromatography-electrospray ionization-tandem mass spectrometry analyses revealed that the most abundant peptides were amelogenin and leucine-rich amelogenin peptide related. The fractions containing proteins above 20 kDa induced an increase in vascular endothelial growth factor and interleukin-6 secretion, whereas lower molecular weight fractions enhanced proliferation and secretion of interleukin-8 and monocyte chemoattractant protein-1 and reduced interleukin-4 release. The various molecular components in the enamel matrix derivative formulation might contribute to reported effects on tissue regeneration through their influence on vascularization, the immune response, and chemotaxis
Charge localization at the interface between La1-xSrxMnO3 and the infinite layers cuprate CaCuO2
(CaCuO2)m/(La0.7Sr0.3MnO3)n superlattices, consisting of the infinite layers
cuprate CaCuO2 and the optimally doped manganite La1-xSrxMnO3, were grown by
pulsed laser deposition. The transport properties are dominated by the
manganite block. X-Ray Absorption spectroscopy measurements show a clear
evidence of an orbital reconstruction at the interface, ascribed to the
hybridization between the Cu 3d3z2-r2 and the Mn 3d3z2-r2 orbitals via
interface apical oxygen ions. Such a mechanism localizes holes at the
interfaces, thus preventing charge transfer to the CaCuO2 block. Some charge
(holes) transfer occurs toward the La0.7Sr0.3MnO3 block in strongly oxidized
superlattices, contributing to the suppression of the magnetotransport
properties.Comment: 20 pages, 6 figure
Orbital order in La0.5Sr1.5MnO4: beyond a common local Jahn-Teller picture
The standard way to find the orbital occupation of Jahn-Teller (JT) ions is
to use structural data, with the assumption of a one-to-one correspondence
between the orbital occupation and the associated JT distortion, e.g. in O6
octahedron. We show, however, that this approach in principle does not work for
layered systems. Specifically, using the layered manganite La0.5Sr1.5MnO4 as an
example, we found from our x-ray absorption measurements and theoretical
calculations, that the type of orbital ordering strongly contradicts the
standard local distortion approach for the Mn3+O6 octahedra, and that the
generally ignored long-range crystal field effect and anisotropic hopping
integrals are actually crucial to determine the orbital occupation. Our
findings may open a pathway to control of the orbital state in multilayer
systems and thus of their physical properties.Comment: 4+ pages, 4 figure
In-plane magnetic anisotropy of Fe atoms on BiSe(111)
The robustness of the gapless topological surface state hosted by a 3D
topological insulator against perturbations of magnetic origin has been the
focus of recent investigations. We present a comprehensive study of the
magnetic properties of Fe impurities on a prototypical 3D topological insulator
BiSe using local low temperature scanning tunneling microscopy and
integral x-ray magnetic circular dichroism techniques. Single Fe adatoms on the
BiSe surface, in the coverage range are heavily relaxed
into the surface and exhibit a magnetic easy axis within the surface-plane,
contrary to what was assumed in recent investigations on the opening of a gap.
Using \textit{ab initio} approaches, we demonstrate that an in-plane easy axis
arises from the combination of the crystal field and dynamic hybridization
effects.Comment: 5 pages, 3 figures, typos correcte
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Panel data or pseudo panels for longitudinal research? Cross-national comparisons using the example of firms’ training spend
This paper applies a pseudo panel methodology to investigate the evolution of financial investments in training at the firm level over time. This approach enables a more meaningful exploration of inter-temporal changes in situations where longitudinal data does not exist
Systematics of electronic and magnetic properties in the transition metal doped SbTe quantum anomalous Hall platform
The quantum anomalous Hall effect (QAHE) has recently been reported to emerge
in magnetically-doped topological insulators. Although its general
phenomenology is well established, the microscopic origin is far from being
properly understood and controlled. Here we report on a detailed and systematic
investigation of transition-metal (TM)-doped SbTe. By combining density
functional theory (DFT) calculations with complementary experimental
techniques, i.e., scanning tunneling microscopy (STM), resonant photoemission
(resPES), and x-ray magnetic circular dichroism (XMCD), we provide a complete
spectroscopic characterization of both electronic and magnetic properties. Our
results reveal that the TM dopants not only affect the magnetic state of the
host material, but also significantly alter the electronic structure by
generating impurity-derived energy bands. Our findings demonstrate the
existence of a delicate interplay between electronic and magnetic properties in
TM-doped TIs. In particular, we find that the fate of the topological surface
states critically depends on the specific character of the TM impurity: while
V- and Fe-doped SbTe display resonant impurity states in the vicinity
of the Dirac point, Cr and Mn impurities leave the energy gap unaffected. The
single-ion magnetic anisotropy energy and easy axis, which control the magnetic
gap opening and its stability, are also found to be strongly TM
impurity-dependent and can vary from in-plane to out-of-plane depending on the
impurity and its distance from the surface. Overall, our results provide
general guidelines for the realization of a robust QAHE in TM-doped
SbTe in the ferromagnetic state.Comment: 40 pages, 13 figure
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