978 research outputs found
Induced Ge Spin Polarization at the Fe/Ge Interface
We report direct experimental evidence showing induced magnetic moments on Ge
at the interface in an Fe/Ge system. Details of the x-ray magnetic circular
dichroism and resonant magnetic scattering at the Ge L edge demonstrate the
presence of spin-polarized {\it s} states at the Fermi level, as well as {\it
d} character moments at higher energy, which are both oriented antiparallel to
the moment of the Fe layer. Use of the sum rules enables extraction of the L/S
ratio, which is zero for the {\it s} part and for the {\it d}
component. These results are consistent with layer-resolved electronic
structure calculations, which estimate the {\it s} and {\it d} components of
the Ge moment are anti-parallel to the Fe {\it 3d} moment and have a magnitude
of .Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Context dependent substitution biases vary within the human genome
Background:
Models of sequence evolution typically assume that different nucleotide positions evolve independently. This assumption is widely appreciated to be an over-simplification. The best known violations involve biases due to adjacent nucleotides. There have also been suggestions that biases exist at larger scales, however this possibility has not been systematically explored.
Results:
To address this we have developed a method which identifies over- and under-represented substitution patterns and assesses their overall impact on the evolution of genome composition. Our method is designed to account for biases at smaller pattern sizes, removing their effects. We used this method to investigate context bias in the human lineage after the divergence from chimpanzee. We examined bias effects in substitution patterns between 2 and 5 bp long and found significant effects at all sizes. This included some individual three and four base pair patterns with relatively large biases. We also found that bias effects vary across the genome, differing between transposons and non-transposons, between different classes of transposons, and also near and far from genes.
Conclusions:
We found that nucleotides beyond the immediately adjacent one are responsible for substantial context effects, and that these biases vary across the genome
Heliophysics Event Knowledgebase for the Solar Dynamics Observatory and Beyond
The immense volume of data generated by the suite of instruments on SDO
requires new tools for efficient identifying and accessing data that is most
relevant to research investigations. We have developed the Heliophysics Events
Knowledgebase (HEK) to fill this need. The HEK system combines automated data
mining using feature-detection methods and high-performance visualization
systems for data markup. In addition, web services and clients are provided for
searching the resulting metadata, reviewing results, and efficiently accessing
the data. We review these components and present examples of their use with SDO
data.Comment: 17 pages, 4 figure
Origin and Suppression of Magnetic Flux Noise
Magnetic flux noise is a dominant source of dephasing and energy relaxation
in superconducting qubits. The noise power spectral density varies with
frequency as with and spans 13 orders of
magnitude. Recent work indicates that the noise is from unpaired magnetic
defects on the surfaces of the superconducting devices. Here, we demonstrate
that adsorbed molecular O is the dominant contributor to magnetism in
superconducting thin films. We show that this magnetism can be suppressed by
appropriate surface treatment or improvement in the sample vacuum environment.
We observe a suppression of static spin susceptibility by more than an order of
magnitude and a suppression of magnetic flux noise power spectral density
by more than a factor of 5. These advances open the door to realization of
superconducting qubits with improved quantum coherence.Comment: Main text: 5 pages, 4 figures. Supplement: 8 pages, 6 figure
Tuning Fermilab Heavy Quarks in 2+1 Flavor Lattice QCD with Application to Hyperfine Splittings
We report the non-perturbative tuning of parameters--- kappa_c, kappa_b, and
kappa_crit ---that determine the heavy-quark mass in the Fermilab action. This
requires the computation of the masses of Ds^(*) and Bs^(*) mesons comprised of
a Fermilab heavy quark and a staggered light quark. Additionally, we report the
hyperfine splittings for Ds and Bs mesons as a cross-check of our simulation
and analysis methods. We find a splitting of 145 +/- 15 MeV for the Ds system
and 40 +/- 9 MeV for the Bs system. These are in good agreement with the
Particle Data Group average values of 143.9 +/- 0.4 MeV and 46.1 +/- 1.5 MeV,
respectively. The calculations are carried out with the MILC 2+1 flavor gauge
configurations at three lattice spacings approximately 0.15, 0.12, and 0.09
fm.Comment: 34 pages, 8 figures, 26 tables; some sections rearranged for clarity;
conclusions unchanged; version accepted by Phys. Rev.
Probing gas and dust in the tidal tail of NGC 5221 with the type Ia supernova iPTF16abc
Context. Type Ia supernovae (SNe Ia) can be used to address numerous
questions in astrophysics and cosmology. Due to their well known spectral and
photometric properties, SNe Ia are well suited to study gas and dust along the
lines-of-sight to the explosions. For example, narrow Na I D and Ca II H&K
absorption lines can be studied easily, because of the well-defined spectral
continuum of SNe Ia around these features. Aims. We study the gas and dust
along the line-of-sight to iPTF16abc, which occurred in an unusual location, in
a tidal arm, 80 kpc from centre of the galaxy NGC 5221. Methods. Using a
time-series of high-resolution spectra, we examine narrow Na I D and Ca II H&K
absorption features for variations in time, which would be indicative for
circumstellar (CS) matter. Furthermore, we take advantage of the well known
photometric properties of SNe Ia to determine reddening due to dust along the
line-of-sight. Results. From the lack of variations in Na I D and Ca II H&K, we
determine that none of the detected absorption features originate from the CS
medium of iPTF16abc. While the Na I D and Ca II H&K absorption is found to be
optically thick, a negligible amount of reddening points to a small column of
interstellar dust. Conclusions. We find that the gas along the line-of-sight to
iPTF16abc is typical of what might be found in the interstellar medium (ISM)
within a galaxy. It suggests that we are observing gas that has been tidally
stripped during an interaction of NGC 5221 with one of its neighbouring
galaxies in the past years. In the future, the gas clouds could
become the locations of star formation. On a longer time scale, the clouds
might diffuse, enriching the circum-galactic medium (CGM) with metals. The gas
profile along the line-of-sight should be useful for future studies of the
dynamics of the galaxy group containing NGC 5221.Comment: 8 pages, 6 figure
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