332 research outputs found
When Can You Fold a Map?
We explore the following problem: given a collection of creases on a piece of
paper, each assigned a folding direction of mountain or valley, is there a flat
folding by a sequence of simple folds? There are several models of simple
folds; the simplest one-layer simple fold rotates a portion of paper about a
crease in the paper by +-180 degrees. We first consider the analogous questions
in one dimension lower -- bending a segment into a flat object -- which lead to
interesting problems on strings. We develop efficient algorithms for the
recognition of simply foldable 1D crease patterns, and reconstruction of a
sequence of simple folds. Indeed, we prove that a 1D crease pattern is
flat-foldable by any means precisely if it is by a sequence of one-layer simple
folds.
Next we explore simple foldability in two dimensions, and find a surprising
contrast: ``map'' folding and variants are polynomial, but slight
generalizations are NP-complete. Specifically, we develop a linear-time
algorithm for deciding foldability of an orthogonal crease pattern on a
rectangular piece of paper, and prove that it is (weakly) NP-complete to decide
foldability of (1) an orthogonal crease pattern on a orthogonal piece of paper,
(2) a crease pattern of axis-parallel and diagonal (45-degree) creases on a
square piece of paper, and (3) crease patterns without a mountain/valley
assignment.Comment: 24 pages, 19 figures. Version 3 includes several improvements thanks
to referees, including formal definitions of simple folds, more figures,
table summarizing results, new open problems, and additional reference
Demonstration of Bias-Controlled Algorithmic Tuning of Quantum Dots in a Well (DWELL) MidIR Detectors
The quantum-confined Stark effect in intersublevel transitions present in quantum-dots-in-a-well (DWELL) detectors gives rise to a midIR spectral response that is dependent upon the detector\u27s operational bias. The spectral responses resulting from different biases exhibit spectral shifts, albeit with significant spectral overlap. A postprocessing algorithm was developed by Sakoglu that exploited this bias-dependent spectral diversity to predict the continuous and arbitrary tunability of the DWELL detector within certain limits. This paper focuses on the experimental demonstration of the DWELL-based spectral tuning algorithm. It is shown experimentally that it is possible to reconstruct the spectral content of a target electronically without using any dispersive optical elements for tuning, thereby demonstrating a DWELL-based algorithmic spectrometer. The effects of dark current, detector temperature, and bias selection on the tuning capability are also investigated experimentally
Deep CCD Surface Photometry of Galaxy Clusters I: Methods and Initial Studies of Intracluster Starlight
We report the initial results of a deep imaging survey of galaxy clusters.
The primary goals of this survey are to quantify the amount of intracluster
light as a function of cluster properties, and to quantify the frequency of
tidal debris. We outline the techniques needed to perform such a survey, and we
report findings for the first two galaxy clusters in the survey: Abell 1413,
and MKW 7 . These clusters vary greatly in richness and structure. We show that
our surface photometry reliably reaches to a surface brightness of \mu_v = 26.5
mags per arcsec. We find that both clusters show clear excesses over a
best-fitting r^{1/4} profile: this was expected for Abell 1413, but not for MKW
7. Both clusters also show evidence of tidal debris in the form of plumes and
arc-like structures, but no long tidal arcs were detected. We also find that
the central cD galaxy in Abell 1413 is flattened at large radii, with an
ellipticity of , the largest measured ellipticity of any cD galaxy
to date.Comment: 58 pages, 24 figures, accepted for publication in the Astrophysical
Journal. Version has extremely low resolution figures to comply with 650k
limit. High resolution version is available at
http://burro.astr.cwru.edu/johnf/icl1.ps.gz Obtaining high resolution version
is strongly reccomende
Elemental Abundances of Kepler Objects of Interest in APOGEE. I. Two Distinct Orbital Period Regimes Inferred from Host Star Iron Abundances
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has
observed 600 transiting exoplanets and exoplanet candidates from
\textit{Kepler} (Kepler Objects of Interest, KOIs), most with 18 epochs.
The combined multi-epoch spectra are of high signal-to-noise (typically
100) and yield precise stellar parameters and chemical abundances. We
first confirm the ability of the APOGEE abundance pipeline, ASPCAP, to derive
reliable [Fe/H] and effective temperatures for FGK dwarf stars -- the primary
\textit{Kepler} host stellar type -- by comparing the ASPCAP-derived stellar
parameters to those from independent high-resolution spectroscopic
characterizations for 221 dwarf stars in the literature. With a sample of 282
close-in ( days) KOIs observed in the APOGEE KOI goal program, we find a
correlation between orbital period and host star [Fe/H] characterized by a
critical period, = days, below which small
exoplanets orbit statistically more metal-enriched host stars. This effect may
trace a metallicity dependence of the protoplanetary disk inner-radius at the
time of planet formation or may be a result of rocky planet ingestion driven by
inward planetary migration. We also consider that this may trace a metallicity
dependence of the dust sublimation radius, but find no statistically
significant correlation with host and orbital period to
support such a claim.Comment: 18 Pages, Accepted to A
Perspective on gravitational self-force analyses
A point particle of mass moving on a geodesic creates a perturbation
, of the spacetime metric , that diverges at the particle.
Simple expressions are given for the singular part of and its
distortion caused by the spacetime. This singular part h^\SS_{ab} is
described in different coordinate systems and in different gauges. Subtracting
h^\SS_{ab} from leaves a regular remainder . The
self-force on the particle from its own gravitational field adjusts the world
line at \Or(\mu) to be a geodesic of ; this adjustment
includes all of the effects of radiation reaction. For the case that the
particle is a small non-rotating black hole, we give a uniformly valid
approximation to a solution of the Einstein equations, with a remainder of
\Or(\mu^2) as .
An example presents the actual steps involved in a self-force calculation.
Gauge freedom introduces ambiguity in perturbation analysis. However,
physically interesting problems avoid this ambiguity.Comment: 40 pages, to appear in a special issue of CQG on radiation reaction,
contains additional references, improved notation for tensor harmonic
Trigger Point Injections for Headache Disorders: Expert Consensus Methodology and Narrative Review
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109332/1/head12442.pd
Development, Operation, and Results From the Texas Automated Buoy System
The Texas Automated Buoy System (TABS) is a coastal network of moored buoys that report near-real-time observations about currents and winds along the Texas coast. Established in 1995, the primary mission of TABS is ocean observations in the service of oil spill preparedness and response. The state of Texas funded the system with the intent of improving the data available to oil spill trajectory modelers. In its 12 years of operation, TABS has proven its usefulness during realistic oil spill drills and actual spills. The original capabilities of TABS, i.e., measurement of surface currents and temperatures, have been extended to the marine surface layer, the entire water column, and the sea floor. In addition to observations, a modeling component has been integrated into the TABS program. The goal is to form the core of a complete ocean observing system for Texas waters. As the nation embarks on the development of an integrated ocean observing system, TABS will continue to be an active participant of the Gulf of Mexico Coastal Ocean Observing System (GCOOS) regional association and the primary source of near-surface current measurements in the northwestern Gulf of Mexico. This article describes the origin of TABS, the philosophy behind the operation and development of the system, the resulting modifications to improve the system, the expansion of the system to include new sensors, the development of TABS forecasting models and real-time analysis tools, and how TABS has met many of the societal goals envisioned for GCOOS
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A quantitative approach for measuring the reservoir of latent HIV-1 proviruses.
A stable latent reservoir for HIV-1 in resting CD4+ T cells is the principal barrier to a cure1-3. Curative strategies that target the reservoir are being tested4,5 and require accurate, scalable reservoir assays. The reservoir was defined with quantitative viral outgrowth assays for cells that release infectious virus after one round of T cell activation1. However, these quantitative outgrowth assays and newer assays for cells that produce viral RNA after activation6 may underestimate the reservoir size because one round of activation does not induce all proviruses7. Many studies rely on simple assays based on polymerase chain reaction to detect proviral DNA regardless of transcriptional status, but the clinical relevance of these assays is unclear, as the vast majority of proviruses are defective7-9. Here we describe a more accurate method of measuring the HIV-1 reservoir that separately quantifies intact and defective proviruses. We show that the dynamics of cells that carry intact and defective proviruses are different in vitro and in vivo. These findings have implications for targeting the intact proviruses that are a barrier to curing HIV infection
TOI-150: A transiting hot Jupiter in the TESS southern CVZ
We report the detection of a hot Jupiter ($M_{p}=1.75_{-0.17}^{+0.14}\
M_{J}R_{p}=1.38\pm0.04\ R_{J}\log
g=4.152^{+0.030}_{-0.043}\beta=-79.59^{\circ}$). We confirm the
planetary nature of the candidate TOI-150.01 using radial velocity observations
from the APOGEE-2 South spectrograph and the Carnegie Planet Finder
Spectrograph, ground-based photometric observations from the robotic
Three-hundred MilliMeter Telescope at Las Campanas Observatory, and Gaia
distance estimates. Large-scale spectroscopic surveys, such as APOGEE/APOGEE-2,
now have sufficient radial velocity precision to directly confirm the signature
of giant exoplanets, making such data sets valuable tools in the TESS era.
Continual monitoring of TOI-150 by TESS can reveal additional planets and
subsequent observations can provide insights into planetary system
architectures involving a hot Jupiter around a star about halfway through its
main-sequence life.Comment: 13 pages, 3 figures, 2 tables, accepted to ApJ
The Hot Interstellar Medium of Normal Elliptical Galaxies. I. A Chandra Gas Gallery and Comparison of X-ray and Optical Morphology
We present an X-ray analysis of 54 normal elliptical galaxies in the Chandra
archive and isolate their hot gas component from the contaminating point source
emission, allowing us to conduct, for the first time, a morphological analysis
on the gas alone. A comparison with optical images and photometry shows that
the hot gas morphology has surprisingly little in common with the shape of the
stellar distribution. We observe no correlation between optical and X-ray
ellipticities in the inner regions where stellar mass dominates over dark
matter. A shallow correlation would be expected if the gas had settled into
hydrostatic equilibrium with the gravitational potential. Instead, observed
X-ray ellipticities exceed optical ellipticities in many cases. We exclude
rotation as the dominant factor to produce the gas ellipticities. The gas
appears disturbed, and hydrostatic equilibrium is the exception rather than the
rule. Nearly all hydrostatic models can be ruled out at 99% confidence, based
of their inability to reproduce the optical-X-ray correlation and large X-ray
ellipticities. Hydrostatic models not excluded are those in which dark matter
either dominates over stellar mass inside the inner half-light radius or has a
prominently cigar-shaped distribution, both of which can be ruled out on other
grounds. We conclude that, even for rather X-ray faint elliptical galaxies, the
gas is at least so far out of equilibrium that it does not retain any
information about the shape of the potential, and that X-ray derived radial
mass profiles may be in error by factors of order unity.Comment: 20 Pages, 8 Figures (3 new), extended discussion, accepted to ApJ,
high-resolution version with additional online-only figures available at
http://www.phy.ohiou.edu/~diehl/Publications
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