274 research outputs found
Letter from R. Wash to George Sibley, June 30, 1816
Transcript of Letter from R. Wash to George Sibley, June 30, 1816. Wash discusses the dispute between the Osage and Cherokee tribes, and that it has been made known to the President; discusses how to settle the dispute
Occupancy Modeling of Hunter Sightings for Monitoring Moose in Montana
Moose (Alces alces) are widely distributed across >100,000 km2 of Montana yet occur at low densities and garner minimal funding. Traditional monitoring methods present challenges of low precision and high cost. During 2012–2015, we tested the efficacy of applying patch occupancy modeling to moose sightings made by hunters of other cervids for cost-effective statewide monitoring. We used phone surveys to collect sightings and allocated each spatially to grid cells and temporally to 1-week sessions within a 5-week hunting season. For each cell we estimated covariates with hypothesized relevance to occupancy by moose or detectability by hunters, including characterization of vegetation, topography, accessibility by humans, hunter effort, and spatial correlation. We sampled ?45,500 hunters per year at a cost of 15,000. Of responding hunters, 14% reported ?1 moose sighting which accumulated to 4,800–6,800 sightings annually. Statewide occupancy estimates were robust and consistent across years of sampling, averaging ? = 0.30 (SE=0.005, range=0.30–0.31). Forested vegetation types reduced the probability of detection but increased the probability of occupancy, while shrub and riparian vegetation types increased both detection and occupancy rates. The amount of sampling effort expended affected detection rates but did not affect occupancy estimates. We expect occupancy estimates to be less sensitive to population changes in areas with higher abundance, making this approach better suited for monitoring change at the range periphery. Alternate count-based analysis techniques such as n-mixture models may offer an alternative to make best use of hunter sightings for monitoring statewide moose populations
Classical and Quantum Consistency of the DGP Model
We study the Dvali-Gabadadze-Porrati model by the method of the boundary
effective action. The truncation of this action to the bending mode \pi
consistently describes physics in a wide range of regimes both at the classical
and at the quantum level. The Vainshtein effect, which restores agreement with
precise tests of general relativity, follows straightforwardly. We give a
simple and general proof of stability, i.e. absence of ghosts in the
fluctuations, valid for most of the relevant cases, like for instance the
spherical source in asymptotically flat space. However we confirm that around
certain interesting self-accelerating cosmological solutions there is a ghost.
We consider the issue of quantum corrections. Around flat space \pi becomes
strongly coupled below a macroscopic length of 1000 km, thus impairing the
predictivity of the model. Indeed the tower of higher dimensional operators
which is expected by a generic UV completion of the model limits predictivity
at even larger length scales. We outline a non-generic but consistent choice of
counterterms for which this disaster does not happen and for which the model
remains calculable and successful in all the astrophysical situations of
interest. By this choice, the extrinsic curvature K_{\mu\nu} acts roughly like
a dilaton field controlling the strength of the interaction and the cut-off
scale at each space-time point. At the surface of Earth the cutoff is \sim 1 cm
but it is unlikely that the associated quantum effects be observable in table
top experiments.Comment: 26 pages, 1 eps figur
Graviton production with 2 jets at the LHC in large extra dimensions
We study Kaluza-Klein (KK) graviton production in the large extra dimensions
model via 2 jets plus missing transverse momentum signatures at the LHC. We
make predictions for both the signal and the dominant Zjj and Wjj backgrounds,
where we introduce missing P_T-dependent jet selection cuts that ensure the
smallness of the 2-jet rate over the 1-jet rate. With the same jet selection
cuts, the distributions of the two jets and their correlation with the missing
transverse momentum provide additional evidence for the production of an
invisible massive object.Comment: 8 pages, 10 figures, 1 table; Version to be printed in JHE
Will we observe black holes at LHC?
The generalized uncertainty principle, motivated by string theory and
non-commutative quantum mechanics, suggests significant modifications to the
Hawking temperature and evaporation process of black holes. For
extra-dimensional gravity with Planck scale O(TeV), this leads to important
changes in the formation and detection of black holes at the the Large Hadron
Collider. The number of particles produced in Hawking evaporation decreases
substantially. The evaporation ends when the black hole mass is Planck scale,
leaving a remnant and a consequent missing energy of order TeV. Furthermore,
the minimum energy for black hole formation in collisions is increased, and
could even be increased to such an extent that no black holes are formed at LHC
energies.Comment: 5 pages, 2 figures. Minor changes to match version to appear in
Class. Quant. Gra
Black Hole Astrophysics in AdS Braneworlds
We consider astrophysics of large black holes localized on the brane in the
infinite Randall-Sundrum model. Using their description in terms of a conformal
field theory (CFT) coupled to gravity, deduced in Ref. [1], we show that they
undergo a period of rapid decay via Hawking radiation of CFT modes. For
example, a black hole of mass would shed most of its
mass in years if the AdS radius is mm,
currently the upper bound from table-top experiments. Since this is within the
mass range of X-ray binary systems containing a black hole, the evaporation
enhanced by the hidden sector CFT modes could cause the disappearance of X-ray
sources on the sky. This would be a striking signature of RS2 with a large AdS
radius. Alternatively, for shorter AdS radii, the evaporation would be slower.
In such cases, the persistence of X-ray binaries with black holes already
implies an upper bound on the AdS radius of L \la 10^{-2} mm, an order of
magnitude better than the bounds from table-top experiments. The observation of
primordial black holes with a mass in the MACHO range and an age comparable to the age of the universe would further
strengthen the bound on the AdS radius to L \la {\rm few} \times 10^{-6} mm.Comment: 14 pages, latex, no figures v2: added reference
Chameleon Gravity, Electrostatics, and Kinematics in the Outer Galaxy
Light scalar fields are expected to arise in theories of high energy physics
(such as string theory), and find phenomenological motivations in dark energy,
dark matter, or neutrino physics. However, the coupling of light scalar fields
to ordinary (or dark) matter is strongly constrained from laboratory, solar
system, and astrophysical tests of fifth force. One way to evade these
constraints in dense environments is through the chameleon mechanism, where the
field's mass steeply increases with ambient density. Consequently, the
chameleonic force is only sourced by a thin shell near the surface of dense
objects, which significantly reduces its magnitude.
In this paper, we argue that thin-shell conditions are equivalent to
"conducting" boundary conditions in electrostatics. As an application, we use
the analogue of the method of images to calculate the back-reaction (or
self-force) of an object around a spherical gravitational source. Using this
method, we can explicitly compute the violation of equivalence principle in the
outskirts of galactic haloes (assuming an NFW dark matter profile):
Intermediate mass satellites can be slower than their larger/smaller
counterparts by as much as 10% close to a thin shell.Comment: 17 pages, 3 figure
Comparison of Magnetic Resonance Feature Tracking for Strain Calculation With Harmonic Phase Imaging Analysis
ObjectivesTo compare a steady-state free precession cine sequence–based technique (feature tracking [FT]) to tagged harmonic phase (HARP) analysis for peak average circumferential myocardial strain (εcc) analysis in a large and heterogeneous population of boys with Duchenne muscular dystrophy (DMD).BackgroundCurrent εcc assessment techniques require cardiac magnetic resonance–tagged imaging sequences, and their analysis is complex. The FT method can readily be performed on standard cine (steady-state free precession) sequences.MethodsWe compared mid-left ventricular whole-slice εcc by the 2 techniques in 191 DMD patients grouped according to age and severity of cardiac dysfunction: group B: DMD patients 10 years and younger with normal ejection fraction (EF); group C: DMD patients older than 10 years with normal EF; group D: DMD patients older than 10 years with reduced EF but negative myocardial delayed enhancement (MDE); group E: DMD patients older than 10 years with reduced EF and positive MDE; and group A: 42 control subjects. Retrospective, offline analysis was performed on matched tagged and steady-state free precession slices.ResultsFor the entire study population (N = 233), mean FT εcc values (−13.3 ± 3.8%) were highly correlated with HARP εcc values (−13.6 ± 3.4%), with a Pearson correlation coefficient of 0.899. The mean εcc of DMD patients determined by HARP (−12.52 ± 2.69%) and FT (−12.16 ± 3.12%) was not significantly different (p = NS). Similarly, the mean εcc of the control subjects by determined HARP (−18.85 ± 1.86) and FT (−18.81 ± 1.83) was not significantly different (p = NS). Excellent correlation between the 2 methods was found among subgroups A through E, except there was no significant difference in strain between groups B and C with FT analysis.ConclusionsFT-based assessment of εcc correlates highly with εcc derived from tagged images in a large DMD patient population with a wide range of cardiac dysfunction and can be performed without additional imaging
Kepler constraints on planets near hot Jupiters
We present the results of a search for planetary companions orbiting near hot Jupiter planet candidates (Jupiter-size candidates with orbital periods near 3 d) identified in the Kepler data through its sixth quarter of science operations. Special emphasis is given to companions between the 2∶1 interior and exterior mean-motion resonances. A photometric transit search excludes companions with sizes ranging from roughly two-thirds to five times the size of the Earth, depending upon the noise properties of the target
star. A search for dynamically induced deviations from a constant period (transit timing variations) also shows no significant signals. In contrast, comparison studies of warm Jupiters (with slightly larger orbits) and hot Neptune-size candidates do exhibit signatures of additional companions with these same tests. These differences
between hot Jupiters and other planetary systems denote a distinctly different formation or dynamical history
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