9,882 research outputs found
Design of two-dimensional particle assemblies using isotropic pair interactions with an attractive well
Using ground-state and relative-entropy based inverse design strategies,
isotropic interactions with an attractive well are determined to stabilize and
promote as- sembly of particles into two-dimensional square, honeycomb, and
kagome lattices. The design rules inferred from these results are discussed and
validated in the dis- covery of interactions that favor assembly of the highly
open truncated-square and truncated-hexagonal lattices.Comment: 11 pages, 5 figures and supplemental materia
Where\u27s the Beef? Mad Cows and the Blight of the SPS Agreement
This Note will first outline the SPS Agreement itself--specifically, Part II attempts to present the relevant articles in a manner providing the necessary background for understanding the WTO dispute panel and Appellate Body decisions. Next, Part III discuss and critique, the dispute panel and Appellate Body decisions, specifically, noting the shortcomings of these decisions in the context of the SPS Agreement and its utility as a precedent of international dispute resolution in the area of international regulation of drugs and feedstuffs. Next, I will addresses the likely effect of these decisions upon a possible WTO resolution of the SRM dispute (should it proceed that far). Finally, Part V offers conclusions and recommendations to help guide future decisions to be more pragmatic and to better promote the goals of the SPS Agreement
Social work, independent realities & the circle of moral considerability: Respect for humans, animals & the natural world
Social work\u27s conceptualization as to what it is that entitles an individual or entity to moral consideration, or as having moral status, is thoroughly anthropocentric, and is articulated in complete disregard of the context of our fundamental evolutionary continuity and our embeddedness within an evolving natural world, and flies in the face of the reality that we already inhabit mixed communities and a wider household. It is deemed to be obvious that we are islands of moral value in an otherwise valueless natural world
Slow dynamics at the smeared phase transition of randomly layered magnets
We investigate a model for randomly layered magnets, viz. a three-dimensional
Ising model with planar defects. The magnetic phase transition in this system
is smeared because static long-range order can develop on isolated rare spatial
regions. Here, we report large-scale kinetic Monte Carlo simulations of the
dynamical behavior close to the smeared phase transition which we characterize
by the spin (time) autocorrelation function. In the paramagnetic phase, its
behavior is dominated by Griffiths effects similar to those in magnets with
point defects. In the tail region of the smeared transition the dynamics is
even slower: the autocorrelation function decays like a stretched exponential
at intermediate times before approaching the exponentially small asymptotic
value following a power law at late times. Our Monte-Carlo results are in good
agreement with recent theoretical predictions based on optimal fluctuation
theory.Comment: 7 pages, 6 eps figures, final version as publishe
The MASSIVE Survey - I. A Volume-Limited Integral-Field Spectroscopic Study of the Most Massive Early-Type Galaxies within 108 Mpc
Massive early-type galaxies represent the modern-day remnants of the earliest
major star formation episodes in the history of the universe. These galaxies
are central to our understanding of the evolution of cosmic structure, stellar
populations, and supermassive black holes, but the details of their complex
formation histories remain uncertain. To address this situation, we have
initiated the MASSIVE Survey, a volume-limited, multi-wavelength,
integral-field spectroscopic (IFS) and photometric survey of the structure and
dynamics of the ~100 most massive early-type galaxies within a distance of 108
Mpc. This survey probes a stellar mass range M* > 10^{11.5} Msun and diverse
galaxy environments that have not been systematically studied to date. Our
wide-field IFS data cover about two effective radii of individual galaxies, and
for a subset of them, we are acquiring additional IFS observations on
sub-arcsecond scales with adaptive optics. We are also acquiring deep K-band
imaging to trace the extended halos of the galaxies and measure accurate total
magnitudes. Dynamical orbit modeling of the combined data will allow us to
simultaneously determine the stellar, black hole, and dark matter halo masses.
The primary goals of the project are to constrain the black hole scaling
relations at high masses, investigate systematically the stellar initial mass
function and dark matter distribution in massive galaxies, and probe the
late-time assembly of ellipticals through stellar population and kinematical
gradients. In this paper, we describe the MASSIVE sample selection, discuss the
distinct demographics and structural and environmental properties of the
selected galaxies, and provide an overview of our basic observational program,
science goals and early survey results.Comment: 19 pages, 14 figures. ApJ (2014) vol. 795, in pres
The MASSIVE Survey II: Stellar Population Trends Out to Large Radius in Massive Early Type Galaxies
We examine stellar population gradients in ~100 massive early type galaxies
spanning 180 < sigma* < 370 km/s and M_K of -22.5 to -26.5 mag, observed as
part of the MASSIVE survey (Ma et al. 2014). Using integral-field spectroscopy
from the Mitchell Spectrograph on the 2.7m telescope at McDonald Observatory,
we create stacked spectra as a function of radius for galaxies binned by their
stellar velocity dispersion, stellar mass, and group richness. With excellent
sampling at the highest stellar mass, we examine radial trends in stellar
population properties extending to beyond twice the effective radius (~2.5
R_e). Specifically, we examine trends in age, metallicity, and abundance ratios
of Mg, C, N, and Ca, and discuss the implications for star formation histories
and elemental yields. At a fixed physical radius of 3-6 kpc (the likely size of
the galaxy cores formed at high redshift) stellar age and [alpha/Fe] increase
with increasing sigma* and depend only weakly on stellar mass, as we might
expect if denser galaxies form their central cores earlier and faster. If we
instead focus on 1-1.5 R_e, the trends in abundance and abundance ratio are
washed out, as might be expected if the stars at large radius were accreted by
smaller galaxies. Finally, we show that when controlling for \sigmastar, there
are only very subtle differences in stellar population properties or gradients
as a function of group richness; even at large radius internal properties
matter more than environment in determining star formation history.Comment: 17 pages, 9 figures, accepted by ApJ; resubmitted with updated
reference
Probing hyperbolic polaritons using infrared attenuated total reflectance micro-spectroscopy
Hyperbolic polariton modes are highly appealing for a broad range of
applications in nanophotonics, including surfaced enhanced sensing,
sub-diffractional imaging and reconfigurable metasurfaces. Here we show that
attenuated total reflectance micro-spectroscopy (ATR) using standard
spectroscopic tools can launch hyperbolic polaritons in a Kretschmann-Raether
configuration. We measure multiple hyperbolic and dielectric modes within the
naturally hyperbolic material hexagonal boron nitride as a function of
different isotopic enrichments and flake thickness. This overcomes the
technical challenges of measurement approaches based on nanostructuring, or
scattering scanning nearfield optical microscopy. Ultimately, our ATR approach
allows us to compare the optical properties of small-scale materials prepared
by different techniques systematicallyComment: 13 pages 4 figure
Variable Hard X-ray Emission from the Candidate Accreting Black Hole in Dwarf Galaxy Henize 2-10
We present an analysis of the X-ray spectrum and long-term variability of the
nearby dwarf starburst galaxy Henize 2-10. Recent observations suggest that
this galaxy hosts an actively accreting black hole with mass ~10^6 M_sun. The
presence of an AGN in a low-mass starburst galaxy marks a new environment for
active galactic nuclei (AGNs), with implications for the processes by which
"seed" black holes may form in the early Universe. In this paper, we analyze
four epochs of X-ray observations of Henize 2-10, to characterize the long-term
behavior of its hard nuclear emission. We analyze observations with Chandra
from 2001 and XMM-Newton from 2004 and 2011, as well as an earlier, less
sensitive observation with ASCA from 1997. Based on detailed analysis of the
source and background, we find that the hard (2-10 keV) flux of the putative
AGN has decreased by approximately an order of magnitude between the 2001
Chandra observation and exposures with XMM-Newton in 2004 and 2011. The
observed variability confirms that the emission is due to a single source. It
is unlikely that the variable flux is due to a supernova or ultraluminous X-ray
source, based on the observed long-term behavior of the X-ray and radio
emission, while the observed X-ray variability is consistent with the behavior
of well-studied AGNs.Comment: 7 pages, 4 figures, 2 tables; accepted for publication in Ap
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