399 research outputs found
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
Enhancing the critical current in quasiperiodic pinning arrays below and above the matching magnetic flux
Quasiperiodic pinning arrays, as recently demonstrated theoretically and
experimentally using a five-fold Penrose tiling, can lead to a significant
enhancement of the critical current Ic as compared to "traditional" regular
pinning arrays. However, while regular arrays showed only a sharp peak in
Ic(Phi) at the matching flux Phi1 and quasiperiodic arrays provided a much
broader maximum at Phi<Phi1, both types of pinning arrays turned out to be
inefficient for fluxes larger than Phi1. We demonstrate theoretically and
experimentally the enhancement of Ic(Phi) for Phi>Phi1 by using non-Penrose
quasiperiodic pinning arrays. This result is based on a qualitatively different
mechanism of flux pinning by quasiperiodic pinning arrays and could be
potentially useful for applications in superconducting micro-electronic devices
operating in a broad range of magnetic fields.Comment: 7 pages, 4 figure
0-pi Josephson tunnel junctions with ferromagnetic barrier
We fabricated high quality Nb/Al_2O_3/Ni_{0.6}Cu_{0.4}/Nb
superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions.
Using a ferromagnetic layer with a step-like thickness, we obtain a 0-pi
junction, with equal lengths and critical currents of 0 and pi parts. The
ground state of our 330 microns (1.3 lambda_J) long junction corresponds to a
spontaneous vortex of supercurrent pinned at the 0-pi step and carrying ~6.7%
of the magnetic flux quantum Phi_0. The dependence of the critical current on
the applied magnetic field shows a clear minimum in the vicinity of zero field.Comment: submitted to PR
Critical current diffraction pattern of SIFS Josephson junctions with step-like F-layer
We present the latest generation of
superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions
with a step-like thickness of the ferromagnetic (F) layer. The F-layer
thicknesses and in both halves were varied to obtain different
combinations of positive and negative critical current densities and
. The measured dependences of the critical current on applied magnetic
field can be well described by a model which takes into account different
critical current densities (obtained from reference junctions) and different
net magnetization of the multidomain ferromagnetic layer in both halves.Comment: 7 pages, 3 figure
Suppression of dissipation in Nb thin films with triangular antidot arrays by random removal of pinning sites
The depinning current Ic versus applied magnetic field B close to the
transition temperature Tc of Nb thin films with randomly diluted triangular
arrays of antidots is investigated. % Our experiments confirm essential
features in Ic(B) as predicted by Reichhardt and Olson Reichhardt [Phys.Rev. B
76, 094512 (2007)]. % We show that, by introducing disorder into periodic
pinning arrays, Ic can be enhanced. % In particular, for arrays with fixed
density n_p of antidots, an increase in dilution Pd induces an increase in Ic
and decrease of the flux-flow voltage for B>Bp=n_p Phi_0.Comment: 5 pages, 4 figure
Direct current superconducting quantum interferometers with asymmetric shunt resistors
We have investigated asymmetrically shunted Nb/Al-AlO/Nb direct current
(dc) superconducting quantum interference devices (SQUIDs). While keeping the
total resistance identical to a comparable symmetric SQUID with , we shunted only one of the two Josephson junctions with
. Simulations predict that the optimum energy resolution
and thus also the noise performance of such an asymmetric SQUID can
be 3--4 times better than that of its symmetric counterpart. Experiments at a
temperature of 4.2\,K yielded for an asymmetric
SQUID with an inductance of . For a comparable symmetric device
was achieved, confirming our simulation results.Comment: 5 pages, 4 figure
SuperCYPsPred - a web server for the prediction of cytochrome activity
Cytochrome P450 enzymes (CYPs)-mediated drug metabolism influences drug pharmacokinetics and results in adverse outcomes in patients through drug-drug interactions (DDIs). Absorption, distribution, metabolism, excretion and toxicity (ADMET) issues are the leading causes for the failure of a drug in the clinical trials. As details on their metabolism are known for just half of the approved drugs, a tool for reliable prediction of CYPs specificity is needed. The SuperCYPsPred web server is currently focused on five major CYPs isoenzymes, which includes CYP1A2, CYP2C19, CYP2D6, CYP2C9 and CYP3A4 that are responsible for more than 80% of the metabolism of clinical drugs. The prediction models for classification of the CYPs inhibition are based on well-established machine learning methods. The models were validated both on cross-validation and external validation sets and achieved good performance. The web server takes a 2D chemical structure as input and reports the CYP inhibition profile of the chemical for 10 models using different molecular fingerprints, along with confidence scores, similar compounds, known CYPs information of drugs-published in literature, detailed interaction profile of individual cytochromes including a DDIs table and an overall CYPs prediction radar chart (http://insilico-cyp.charite.de/SuperCYPsPred/).The web server does not require log in or registration and is free to use
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