1,870 research outputs found
When Push Comes to Shove: How Qualified Immunity Shuts the Door to Constitutional Claims Against Law Enforcement
Sometimes lawyers get pushed around—both literally and figuratively. However, it is not every day that a Netflix camera crew might capture such an altercation on camera. While filming a Netflix documentary about the experiences of undocumented persons in the United States, Andrea Martinez found herself in a precarious situation that resulted in her suing two United States Immigration and Customs Enforcement agents for allegedly violating her Fourth Amendment rights. Plaintiffs like Martinez often struggle to overcome the strenuous legal doctrine of qualified immunity when filing suit against government officials. Several circuits across the country are clarifying legal guidelines and applying them to claims similar to those of Martinez. The Eighth Circuit should follow suit by clarifying its guidelines in the context of Fourth Amendment claims and qualified immunity
The Non-homogeneous Poisson Process for Fast Radio Burst Rates
This paper presents the non-homogeneous Poisson process (NHPP) for modeling
the rate of fast radio bursts (FRBs) and other infrequently observed
astronomical events. The NHPP, well-known in statistics, can model changes in
the rate as a function of both astronomical features and the details of an
observing campaign. This is particularly helpful for rare events like FRBs
because the NHPP can combine information across surveys, making the most of all
available information. The goal of the paper is two-fold. First, it is intended
to be a tutorial on the use of the NHPP. Second, we build an NHPP model that
incorporates beam patterns and a power law flux distribution for the rate of
FRBs. Using information from 12 surveys including 15 detections, we find an
all-sky FRB rate of 586.88 events per sky per day above a flux of 1 Jy (95\%
CI: 271.86, 923.72) and a flux power-law index of 0.91 (95\% CI: 0.57, 1.25).
Our rate is lower than other published rates, but consistent with the rate
given in Champion et al. 2016.Comment: 19 pages, 2 figure
The History and Influence of Black Baseball in the United States and Indianapolis
When Americans discuss the history of baseball, names like Lou Gehrig, Babe Ruth, Ty Cobb, Connie Mack, and Walter Johnson are mentioned. But what about men like Rube Foster, Buck Leonard, C. I. Taylor, Josh Gibson, and Oscar Charleston? Most American baseball fans know little about black baseball and the lives of black players. A study of black baseball, focusing on the Negro leagues, answers some of the questions baseball fans and historians might ask out of ignorance. How did baseball become segregated? How did the Negro leagues evolve? What was life like for black baseball players? How was the game in the Negro leagues really played? And did black baseball really have a measurable effect on black society? The last question can be answered with an emphatic yes
Galactic Center Pulsars with the ngVLA
Pulsars in the Galactic Center (GC) are important probes of General
Relativity, star formation, stellar dynamics, stellar evolution, and the
interstellar medium. Despite years of searching, only a handful of pulsars in
the central 0.5 deg are known. The high-frequency sensitivity of ngVLA will
open a new window for discovery and characterization of pulsars in the GC. A
pulsar in orbit around the GC black hole, Sgr A*, will provide an unprecedented
probe of black hole physics and General Relativity.Comment: To be published in the ASP Monograph Series, "Science with a
Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA
A Millisecond Interferometric Search for Fast Radio Bursts with the Very Large Array
We report on the first millisecond timescale radio interferometric search for
the new class of transient known as fast radio bursts (FRBs). We used the Very
Large Array (VLA) for a 166-hour, millisecond imaging campaign to detect and
precisely localize an FRB. We observed at 1.4 GHz and produced visibilities
with 5 ms time resolution over 256 MHz of bandwidth. Dedispersed images were
searched for transients with dispersion measures from 0 to 3000 pc/cm3. No
transients were detected in observations of high Galactic latitude fields taken
from September 2013 though October 2014. Observations of a known pulsar show
that images typically had a thermal-noise limited sensitivity of 120 mJy/beam
(8 sigma; Stokes I) in 5 ms and could detect and localize transients over a
wide field of view. Our nondetection limits the FRB rate to less than
7e4/sky/day (95% confidence) above a fluence limit of 1.2 Jy-ms. Assuming a
Euclidean flux distribution, the VLA rate limit is inconsistent with the
published rate of Thornton et al. We recalculate previously published rates
with a homogeneous consideration of the effects of primary beam attenuation,
dispersion, pulse width, and sky brightness. This revises the FRB rate downward
and shows that the VLA observations had a roughly 60% chance of detecting a
typical FRB and that a 95% confidence constraint would require roughly 500
hours of similar VLA observing. Our survey also limits the repetition rate of
an FRB to 2 times less than any known repeating millisecond radio transient.Comment: Submitted to ApJ. 13 pages, 9 figure
The Black Hole Mass and Extreme Orbital Structure in NGC1399
The largest galaxies, and in particular central galaxies in clusters, offer
unique insight into understanding the mechanism for the growth of nuclear black
holes. We present Hubble Space Telescope kinematics for NGC1399, the central
galaxy in Fornax. We find the best-fit model contains a black hole of 5.1 +-0.7
x 10^8 Msun (at a distance of 21.1 Mpc), a factor of over 2 below the
correlation of black hole mass and velocity dispersion. We also find a dramatic
signature for central tangential anisotropy. The velocity profiles on adjacent
sides 0.5" away from the nucleus show strong bimodality, and the central
spectrum shows a large drop in the dispersion. Both of these observations point
to an orbital distribution that is tangentially biased. The best-fit orbital
model suggests a ratio of the tangential to radial internal velocity
dispersions of three. This ratio is the largest seen in any galaxy to date and
will provide an important measure for the mode by which the central black hole
has grown.Comment: 9 pages, accepted for publication in the Astrophysical Journa
Evolution of X-ray cluster scaling relations in simulations with radiative cooling and non-gravitational heating
We investigate the redshift dependence of X-ray cluster scaling relations
drawn from three hydrodynamic simulations of the LCDM cosmology: a Radiative
model that incorporates radiative cooling of the gas, a Preheating model that
additionally heats the gas uniformly at high redshift, and a Feedback model
that self-consistently heats cold gas in proportion to its local star-formation
rate. While all three models are capable of reproducing the observed local
Lx-Tx relation, they predict substantially different results at high redshift
(to z=1.5), with the Radiative, Preheating and Feedback models predicting
strongly positive, mildly positive and mildly negative evolution, respectively.
The physical explanation for these differences lies in the structure of the
intracluster medium. All three models predict significant temperature
fluctuations at any given radius due to the presence of cool subclumps and, in
the case of the Feedback simulation, reheated gas. The mean gas temperature
lies above the dynamical temperature of the halo for all models at z=0, but
differs between models at higher redshift with the Radiative model having the
lowest mean gas temperature at z=1.5.
We have not attempted to model the scaling relations in a manner that mimics
the observational selection effects, nor has a consistent observational picture
yet emerged. Nevertheless, evolution of the scaling relations promises to be a
powerful probe of the physics of entropy generation in clusters. First
indications are that early, widespread heating is favored over an extended
period of heating that is associated with galaxy formation.Comment: Accepted for publication in ApJ. Minor changes following referee's
comment
The slope of the black-hole mass versus velocity dispersion correlation
Observations of nearby galaxies reveal a strong correlation between the mass
of the central dark object M and the velocity dispersion sigma of the host
galaxy, of the form log(M/M_sun) = a + b*log(sigma/sigma_0); however, published
estimates of the slope b span a wide range (3.75 to 5.3). Merritt & Ferrarese
have argued that low slopes (<4) arise because of neglect of random measurement
errors in the dispersions and an incorrect choice for the dispersion of the
Milky Way Galaxy. We show that these explanations account for at most a small
part of the slope range. Instead, the range of slopes arises mostly because of
systematic differences in the velocity dispersions used by different groups for
the same galaxies. The origin of these differences remains unclear, but we
suggest that one significant component of the difference results from Ferrarese
& Merritt's extrapolation of central velocity dispersions to r_e/8 (r_e is the
effective radius) using an empirical formula. Another component may arise from
dispersion-dependent systematic errors in the measurements. A new determination
of the slope using 31 galaxies yields b=4.02 +/- 0.32, a=8.13 +/- 0.06, for
sigma_0=200 km/s. The M-sigma relation has an intrinsic dispersion in log M
that is no larger than 0.3 dex. In an Appendix, we present a simple model for
the velocity-dispersion profile of the Galactic bulge.Comment: 37 pages, 9 figure
Enantioselective Narasaka-Heck Cyclizations:Synthesis of Tetrasubstituted Nitrogen-Bearing Stereocenters
A SPINOL-derived P,N-ligand system enables Pd-catalyzed 5-exo cyclization of oxime esters with trisubstituted alkenes to generate dihydropyrroles in up to 86% yield and 95 : 5 e.r.</p
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