10,223 research outputs found
Characterization of cells of amniotic fluids by immunological identification of intermediate-sized filaments: Presence of cells of different tissue origin
Antibodies against intermediate-sized filaments, of the prekeratin or vimentin type, were used to investigate the presence of these filaments by indirect immunofluorescence microscopy in cultured and non-cultured amniotic fluid cells, in frozen sections of the placenta and in isolated cells of the amniotic epithelium. Two major classes of cells can be cultured from amniotic fluids, namely cells of epithelial origin containing filaments of the prekeratin type and cells of different origin which contain filaments of the vimentin type but are negative when tested with antibodies to epidermal prekeratin. The presence of prekeratin type filaments correlates with the morphology of colonies of amniotic fluid cell cultures in vitro as classified by Hoehn et al. (1974). Cells of E-type colonies are shown to be of epithelial origin. In contrast our data indicate a different origin of almost all cells of F-type colonies and of the large majority of cells of AF-type colonies. Cells of epithelial origin and positively stained with antibodies to epidermal prekeratin are occasionally scattered in F-type colonies and in variable percentages (up to 30%) in AF-type colonies. Surprisingly, cryostat sections of the amniotic epithelium and isolated groups of amniotic cells showed positive reactions with both antibodies to vimentin and prekeratin. The possibility that amniotic cells may be different from other epithelial cells in that they contain both types of filaments simultaneously already in situ is presently under investigation
Single magnetic adsorbates on s-wave superconductors
In superconductors, magnetic impurities induce a pair-breaking potential for
Cooper pairs, which locally affects the Bogoliubov quasiparticles and gives
rise to Yu-Shiba-Rusinov (YSR or Shiba, in short) bound states in the density
of states (DoS). These states carry information on the magnetic coupling
strength of the impurity with the superconductor, which determines the
many-body ground state properties of the system. Recently, the interest in
Shiba physics was boosted by the prediction of topological superconductivity
and Majorana modes in magnetically coupled chains and arrays of Shiba
impurities. Here, we review the physical insights obtained by scanning
tunneling microscopy into single magnetic adsorbates on the -wave
superconductor lead (Pb). We explore the tunneling processes into Shiba states,
show how magnetic anisotropy affects many-body excitations, and determine the
crossing of the many-body groundstate through a quantum phase transition.
Finally, we discuss the coupling of impurities into dimers and chains and their
relation to Majorana physics.Comment: 18 pages, 17 figures, revie
Exploiting boundary states of imperfect spin chains for high-fidelity state transfer
We study transfer of a quantum state through XX spin chains with static
imperfections. We combine the two standard approaches for state transfer based
on (i) modulated couplings between neighboring spins throughout the spin chain
and (ii) weak coupling of the outermost spins to an unmodulated spin chain. The
combined approach allows us to design spin chains with modulated couplings and
localized boundary states, permitting high-fidelity state transfer in the
presence of random static imperfections of the couplings. The modulated
couplings are explicitly obtained from an exact algorithm using the close
relation between tridiagonal matrices and orthogonal polynomials [Linear
Algebr. Appl. 21, 245 (1978)]. The implemented algorithm and a graphical user
interface for constructing spin chains with boundary states (spinGUIn) are
provided as Supplemental Material.Comment: 7 pages, 3 figures + spinGUIn description and Matlab files
iepsolve.m, spinGUIn.fig, spinGUIn.
Tuning the magnetic anisotropy of single molecules
The magnetism of single atoms and molecules is governed by the atomic scale
environment. In general, the reduced symmetry of the surrounding splits the
states and aligns the magnetic moment along certain favorable directions. Here,
we show that we can reversibly modify the magnetocrystalline anisotropy by
manipulating the environment of single iron(II) porphyrin molecules adsorbed on
Pb(111) with the tip of a scanning tunneling microscope. When we decrease the
tip--molecule distance, we first observe a small increase followed by an
exponential decrease of the axial anisotropy on the molecules. This is in
contrast to the monotonous increase observed earlier for the same molecule with
an additional axial Cl ligand. We ascribe the changes in the anisotropy of both
species to a deformation of the molecules in the presence of the attractive
force of the tip, which leads to a change in the level alignment. These
experiments demonstrate the feasibility of a precise tuning of the magnetic
anisotropy of an individual molecule by mechanical control.Comment: 16 pages, 5 figures; online at Nano Letters (2015
Visualizing intramolecular distortions as the origin of transverse magnetic anisotropy
The magnetic properties of metal–organic complexes are strongly influenced by conformational changes in the ligand. The flexibility of Fe-tetra-pyridyl-porphyrin molecules leads to different adsorption configurations on a Au(111) surface. By combining low-temperature scanning tunneling spectroscopy and atomic force microscopy, we resolve a correlation of the molecular configuration with different spin states and magnitudes of magnetic anisotropy. When the macrocycle exhibits a laterally undistorted saddle shape, the molecules lie in a S = 1 state with axial anisotropy arising from a square-planar ligand field. If the symmetry in the molecular ligand field is reduced by a lateral distortion of the molecule, we find a finite contribution of transverse anisotropy. Some of the distorted molecules lie in a S = 2 state, again exhibiting substantial transverse anisotropy
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