504 research outputs found
The barium iron ruthenium oxide system
In the system BaFe(1-x)Ru(x)O(3-y), three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0 to 0.75) with hexagonal BaTiO3 structure (6H; sequence (hcc)2), a Ru-rich phase (x = 0.9) of hexagonal 4H-type (sequence (hc)2), and the pure Ru compounds BaRuO3 with rhombohedral 9R structure (sequence (hhc)3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich compounds with complete O lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors. The lattice parameters are given
Combined chips for atom-optics
We present experiments with Bose-Einstein condensates on a combined atom
chip. The combined structure consists of a large-scale "carrier chip" and
smaller "atom-optics chips", containing micron-sized elements. This allows us
to work with condensates very close to chip surfaces without suffering from
fragmentation or losses due to thermally driven spin flips. Precise
three-dimensional positioning and transport with constant trap frequencies are
described. Bose-Einstein condensates were manipulated with submicron accuracy
above atom-optics chips. As an application of atom chips, a direction sensitive
magnetic field microscope is demonstrated.Comment: 9 pages, 9 figure
Diffraction of a Bose-Einstein condensate from a Magnetic Lattice on a Micro Chip
We experimentally study the diffraction of a Bose-Einstein condensate from a
magnetic lattice, realized by a set of 372 parallel gold conductors which are
micro fabricated on a silicon substrate. The conductors generate a periodic
potential for the atoms with a lattice constant of 4 microns. After exposing
the condensate to the lattice for several milliseconds we observe diffraction
up to 5th order by standard time of flight imaging techniques. The experimental
data can be quantitatively interpreted with a simple phase imprinting model.
The demonstrated diffraction grating offers promising perspectives for the
construction of an integrated atom interferometer.Comment: 4 pages, 4 figure
High quality ferromagnetic 0 and pi Josephson tunnel junctions
We fabricated high quality \Nb/\Al_2\O_3/\Ni_{0.6}\Cu_{0.4}/\Nb
superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions.
Depending on the thickness of the ferromagnetic \Ni_{0.6}\Cu_{0.4} layer and
on the ambient temperature, the junctions were in the 0 or ground state.
All junctions have homogeneous interfaces showing almost perfect Fraunhofer
patterns. The \Al_2\O_3 tunnel barrier allows to achieve rather low damping,
which is desired for many experiments especially in the quantum domain. The
McCumber parameter increases exponentially with decreasing
temperature and reaches at . The critical
current density in the state was up to at , resulting in a Josephson penetration depth as low as
. Experimentally determined junction parameters are well
described by theory taking into account spin-flip scattering in the
\Ni_{0.6}\Cu_{0.4} layer and different transparencies of the interfaces.Comment: Changed content and Corrected typo
Commensurability effects in superconducting Nb films with quasiperiodic pinning arrays
We study experimentally the critical depinning current Ic versus applied
magnetic field B in Nb thin films which contain 2D arrays of circular antidots
placed on the nodes of quasiperiodic (QP) fivefold Penrose lattices. Close to
the transition temperature Tc we observe matching of the vortex lattice with
the QP pinning array, confirming essential features in the Ic(B) patterns as
predicted by Misko et al. [Phys. Rev. Lett, vol.95, 177007 (2005)]. We find a
significant enhancement in Ic(B) for QP pinning arrays in comparison to Ic in
samples with randomly distributed antidots or no antidots.Comment: 4 pages, 3 figure
Localization of superconductivity in superconductor-electromagnet hybrids
We investigate the nucleation of superconductivity in a superconducting Al
strip under the influence of the magnetic field generated by a current-carrying
Nb wire, perpendicularly oriented and located underneath the strip. The
inhomogeneous magnetic field, induced by the Nb wire, produces a spatial
modulation of the critical temperature T_c, leading to a controllable
localization of the superconducting order parameter (OP) wave function. We
demonstrate that close to the phase boundary T_c(B_ext) the localized OP
solution can be displaced reversibly by either applying an external
perpendicular magnetic field B_ext or by changing the amplitude of the
inhomogeneous field.Comment: 10 pages, 6 figure
Magnetic interference patterns in 0-Pi SIFS Josephson junctions: effects of asymmetry between 0 and Pi regions
We present a detailed analysis of the dependence of the critical current I_c
on the magnetic field B of 0, Pi, and 0-Pi
superconductor-insulator-ferromagnet-superconductor Josephson junctions. I_c(B)
of the 0 and Pi junction closely follows a Fraunhofer pattern, indicating a
homogeneous critical current density j_c(x). The maximum of I_c(B) is slightly
shifted along the field axis, pointing to a small remanent in-plane
magnetization of the F-layer along the field axis. I_c(B) of the 0-Pi junction
exhibits the characteristic central minimum. I_c however has a finite value
here, due to an asymmetry of j_c in the 0 and Pi part. In addition, this I_c(B)
exhibits asymmetric maxima and bumped minima. To explain these features in
detail, flux penetration being different in the 0 part and the Pi part needs to
be taken into account. We discuss this asymmetry in relation to the magnetic
properties of the F-layer and the fabrication technique used to produce the
0-Pi junctions
Mesoscopic cross-film cryotrons: Vortex trapping and dc-Josephson-like oscillations of the critical current
We investigate theoretically and experimentally the transport properties of a
plain Al superconducting strip in the presence of a single straight
current-carrying wire, oriented perpendicular to the superconducting strip. It
is well known that the critical current of the superconducting strip, Ic, in
such cryotron--like system can be tuned by changing the current in the control
wire, Iw. We demonstrated that the discrete change in the number of the pinned
vortices/antivortices inside the narrow and long strip nearby the
current-carrying wire results in a peculiar oscillatory dependence of Ic on Iw.Comment: 8 pages, 8 figure
Two Blood Monocytic Biomarkers (CCL15 and p21) Combined with the Mini-Mental State Examination Discriminate Alzheimer's Disease Patients from Healthy Subjects
Background: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. In AD, monocytes migrate across the blood-brain barrier and differentiate into microglia, are linked to inflammatory responses and display age-dependent decreases in telomere lengths. Methods: Six monocyte-specific chemokines and the (telomere-associated) tumor suppressor proteins p53 and p21 were determined by multiplex immunoassay in plasma and monocyte extracts of patients with AD or mild cognitive impairment, and levels were compared between patients and controls (without cognitive impairment). Results: CCL15 (macrophage inflammatory protein-1δ), CXCL9 (monokine-induced by interferon-γ) and p21 levels were decreased in monocytes of AD patients compared with controls. Conclusion: The combination of monocytic CCL15 and p21 together with the Mini-Mental State Examination enables to differentiate AD patients from controls with high specificity and sensitivity
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