13,216 research outputs found
Analysis of Particle Transport in a Magnetophoretic Microsystem
An analytical analysis is presented of the transport and capture of magnetic
micro/nano-particles in a magnetophoretic microsystem that consists of an array
of integrated soft-magnetic elements embedded beneath a microfluidic channel.
The elements, which are polarized by a bias field, produce a nonuniform field
distribution that gives rise to a force on magnetic particles within the
microchannel. The equations governing particle motion are derived using
analytical expressions for the dominant magnetic and fluidic forces. The
magnetic force is obtained using an analytical expression for the field
distribution in the microchannel combined with a linear magnetization model for
the magnetic response of particles. The theory takes into account particle size
and material properties, the bias field, the dimensions of the microchannel,
the fluid properties, and the flow velocity. The equations of motion are solved
to study particle transport and capture. The analysis indicates that the
particles exhibit an oscillatory motion as they traverse the microsystem, and
that a high capture efficiency can be obtained in practice
Inflammatory Airway Disease of Horses - Revised Consensus Statement
The purpose of this manuscript is to revise and update the previous consensus statement on inflammatory airway disease (IAD) in horses. Since 2007, a large number of scientific articles have been published on the topic and these new findings have led to a significant evolution of our understanding of IAD
Star Formation Across the Taffy Bridge: UGC 12914/15
We present BIMA two-field mosaic CO(1-0) images of the Taffy galaxies (UGC
12914/15), which show the distinct taffy-like radio continuum emission bridging
the two spiral disks. Large amounts of molecular gas (1.4 x 10^{10} Msun, using
the standard Galactic CO-to-H conversion applicable to Galactic disk giant
molecular clouds [GMCs]) were clearly detected throughout the taffy bridge
between the two galaxies, which, as in the more extreme case of HI, presumably
results from a head-on collision between the two galaxies. The highest CO
concentration between the two galaxies corresponds to the H_alpha source in the
taffy bridge near the intruder galaxy UGC 12915. This HII region is also
associated with the strongest source of radio continuum in the bridge, and
shows both morphological and kinematic connections to UGC 12915. The overall CO
distribution of the entire system agrees well with that of the radio continuum
emission, particularly in the taffy bridge. This argues for the star formation
origin of a significant portion of the radio continuum emission. Compared to
the HI morphology and kinematics, which are strongly distorted owing to the
high-speed collision, CO better defines the orbital geometry and impact
parameter of the interaction, as well as the disk properties (e.g., rotation,
orientation) of the progenitor galaxies. Based on the 20cm-to-CO ratio maps, we
conclude that the starburst sites are primarily located in UGC 12915 and the
H_alpha source in the bridge and show that the molecular gas in the taffy
bridge is forming into stars with star formation efficiency comparable to that
of the target galaxy UGC 12914 and similar to that in the Galactic disk.Comment: Minor typo/style corrections to match with the published version (AJ,
Nov. issue). A single .ps.gz file of the entire paper can be downloaded from
http://spider.ipac.caltech.edu/staff/gao/Taffy/all.ps.g
Recommended from our members
Stratospheric Influence on the Tropospheric Circulation Revealed by Idealized Ensemble Forecasts
The coupling between the stratosphere and troposphere following Stratospheric Sudden Warming (SSW) events is investigated in an idealized atmospheric General Circulation Model, with focus on the influence of stratospheric memory on the troposphere. Ensemble forecasts are performed to confirm the role of the stratosphere in the observed equatorward shift of the tropospheric midlatitude jet following an SSW. It is demonstrated that the tropospheric response to the weakening of the lower stratospheric vortex is robust, but weak in amplitude and thus easily masked by tropospheric variability. The amplitude of the response in the troposphere is crucially sensitive to the depth of the SSW. The persistence of the response in the troposphere is attributed to both the increased predictability of the stratosphere following an SSW, and the dynamical coupling between the tropospheric jet and lower stratosphere. These results suggest value in resolving the stratosphere and assimilating upper atmospheric data in forecast models
Orientational phase transitions in anisotropic rare-earth magnets at low temperatures
Orientational phase transitions are investigated within the Heisenberg model
with single-site anisotropy. The temperature dependence of the cone angle is
calculated within the spin-wave theory. The role of the quantum
renormalizations of anisotropy constants is discussed. A comparison with the
experimental data on the cone-plane orientational transition in holmium is
performed.Comment: 9 pages, LaTeX, 3 figure
On parameter estimation with the Wasserstein distance
Statistical inference can be performed by minimizing, over the parameter
space, the Wasserstein distance between model distributions and the empirical
distribution of the data. We study asymptotic properties of such minimum
Wasserstein distance estimators, complementing results derived by Bassetti,
Bodini and Regazzini in 2006. In particular, our results cover the misspecified
setting, in which the data-generating process is not assumed to be part of the
family of distributions described by the model. Our results are motivated by
recent applications of minimum Wasserstein estimators to complex generative
models. We discuss some difficulties arising in the approximation of these
estimators and illustrate their behavior in several numerical experiments. Two
of our examples are taken from the literature on approximate Bayesian
computation and have likelihood functions that are not analytically tractable.
Two other examples involve misspecified models.Comment: 29 pages (+18 pages of appendices), 6 figures. To appear in
Information and Inference: A Journal of the IMA. A previous version of this
paper contained work on approximate Bayesian computation with the Wasserstein
distance, which can now be found at arxiv:1905.0374
A note on the topological order of noncommutative Hall fluids
We evaluate the ground state degeneracy of noncommutative Chern-Simons models
on the two-torus, a quantity that is interpreted as the "topological order" of
associated phases of Hall fluids. We define the noncommutative theory via
T-duality from an ordinary Chern-Simons model with non-abelian 't Hooft
magnetic fluxes. Motivated by this T-duality, we propose a discrete family of
noncommutative, non-abelian fluid models, arising as a natural generalization
of the standard noncommutative Chern-Simons effective models. We compute the
topological order for these universality classes, and comment on their possible
microscopic interpretation.Comment: 14 page
Quantifying the variability of the annular modes: reanalysis uncertainty vs. sampling uncertainty
The annular modes characterize the dominant variability of the extratropical
circulation in each hemisphere, quantifying vacillations in the position of
the tropospheric jet streams and the strength of the stratospheric polar
vortices. Their representation in all available reanalysis products is
assessed. Reanalysis uncertainty associated with limitations in the
ability to constrain the circulation with available observations, i.e., the
inter-reanalysis spread, is contrasted with sampling uncertainty
associated with the finite length of the reanalysis records.It is shown that the annular modes are extremely consistent across all modern
reanalyses during the satellite era (ca. 1979 onward). Consequently,
uncertainty in annular mode variability, e.g., the coupling between the
stratosphere and troposphere and the variation in the amplitude and timescale of jet variations throughout the annual cycle, is dominated by sampling
uncertainty. Comparison of reanalyses based on conventional (i.e.,
nonsatellite) or surface observations alone with those using all available
observations indicates that there is limited ability to characterize the
Southern Annular Mode (SAM) in the presatellite era. Notably, prior to 1979,
surface-input reanalyses better capture the SAM at near-surface levels than
full-input reanalyses. For the Northern Annular Mode, however, there is
evidence that conventional observations are sufficient, at least from 1958
onward. The addition of 2 additional decades of records substantially
reduces sampling uncertainty in several key measures of annular mode
variability, demonstrating the value of more historic reanalyses.
Implications for the assessment of atmospheric models and the strength of
coupling between the surface and upper atmosphere are
discussed.</p
Pion gas viscosity at low temperature and density
By using Chiral Perturbation Theory and the Uehling-Uhlenbeck equation we
compute the viscosity of a pion gas, in the low temperature and low density
regime, in terms of the temperature, and the pion fugacity. The viscosity turns
out to be proportional to the squared root of the temperature over the pion
mass. Next to leading corrections are proportional to the temperature over the
pion mass to the 3/2.Comment: 15 pages, 4 figures. RevTeX
Correlation between the Extraordinary Hall Effect and Resistivity
We study the contribution of different types of scattering sources to the
extraordinary Hall effect. Scattering by magnetic nano-particles embedded in
normal-metal matrix, insulating impurities in magnetic matrix, surface
scattering and temperature dependent scattering are experimentally tested. Our
new data, as well as previously published results on a variety of materials,
are fairly interpreted by a simple modification of the skew scattering model
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