159,163 research outputs found
Studying the Interstellar Medium and the inner region of NPS/Loop 1 with shadow observations toward MBM36
We analyzed data from a shadow observation of the high density molecular
cloud MBM36 (l~4{\deg}, b~35{\deg}) with Suzaku. MBM36 is located in a region
that emits relatively weakly in the 3/4~keV band, compared to the surrounding
NPS/Loop 1 structure and the Galactic Bulge. The contrast between a high and
low density targets in the MBM36 area allows one to separate the local and
distant contributors to the Soft Diffuse X-ray Background, providing a much
better characterization of the individual components compared to single
pointing observations. We identify two non-local thermal components, one at
kT~0.12 keV and one at kT~0.29keV. The colder component matches well with
models of emission from the higher latitude region of the Galactic Bulge. The
emission of the warmer component is in agreement with models predicting that
the NPS is due to a hypershell from the center of the Milky Way. Geometrical
and pressure calculations rule out a nearby bubble as responsible for the
emission associate with the NPS. Any Galactic Halo/CircumGalactic Halo
emission, if present, is outshined by the other components. We also report an
excess emission around 0.9~keV, likely due to an overabundance of NeIX.Comment: 8 pages, 3 figures, approved for publication on Ap
Quantum Manifestation of Elastic Constants in Nanostructures
Generally, there are two distinct effects in modifying the properties of
low-dimensional nanostructures: surface effect (SS) due to increased
surface-volume ratio and quantum size effect (QSE) due to quantum confinement
in reduced dimension. The SS has been widely shown to affect the elastic
constants and mechanical properties of nanostructures. Here, using Pb nanofilm
and graphene nanoribbon as model systems, we demonstrate the QSE on the elastic
constants of nanostructures by first-principles calculations. We show that
generally QSE is dominant in affecting the elastic constants of metallic
nanostructures while SS is more pronounced in semiconductor and insulator
nanostructures. Our findings have broad implications in quantum aspects of
nanomechanics
Descreening of Field Effect in Electrically Gated Nanopores
This modeling work investigates the electrical modulation characteristics of
field-effect gated nanopores. Highly nonlinear current modulations are observed
in nanopores with non-overlapping electric double layers, including those with
pore diameters 100 times the Debye screening length. We attribute this extended
field-effect gating to a descreening effect, i.e. the counter-ions do not fully
relax to screen the gating potential due to the presence of strong ionic
transport
Invalidation of the Kelvin Force in Ferrofluids
Direct and unambiguous experimental evidence for the magnetic force density
being of the form in a certain geometry - rather than being the
Kelvin force - is provided for the first time. (M is the
magnetization, H the field, and B the flux density.)Comment: 4 pages, 4 figure
Shot noise in magnetic tunnel junctions from first principles
We compute the shot noise in ballistic and disordered Fe/MgO/Fe tunnel
junctions by a wave function-matching method. For tunnel barriers with no more
than 5 atomic layers we find a suppression of the Fano factor as a function of
the magnetic configuration. For thicker MgO barriers the shot noise is
suppressed up to a threshold bias indicating the onset of resonant tunneling.
We find excellent agreement with recent experiments when interface disorder is
taken into accountComment: 5 pages,5 figure
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