3,381 research outputs found
Explicit soliton-black hole correspondence for static configurations
We construct an explicit map that transforms static, generalized sine-Gordon
metrics to black hole type metrics. This, in particular, provides for a further
description of the Cadoni correspondence (which extends the
Gegenberg-Kunstatter correspondence) of soliton solutions and extremal black
hole solutions in 2D dilaton gravity.Comment: Submitted to Phys Rev D, 7 pages, no figure
Age grading \u3cem\u3eAn. gambiae\u3c/em\u3e and \u3cem\u3eAn. arabiensis\u3c/em\u3e using near infrared spectra and artificial neural networks
Background
Near infrared spectroscopy (NIRS) is currently complementing techniques to age-grade mosquitoes. NIRS classifies lab-reared and semi-field raised mosquitoes into \u3c or ≥ 7 days old with an average accuracy of 80%, achieved by training a regression model using partial least squares (PLS) and interpreted as a binary classifier. Methods and findings
We explore whether using an artificial neural network (ANN) analysis instead of PLS regression improves the current accuracy of NIRS models for age-grading malaria transmitting mosquitoes. We also explore if directly training a binary classifier instead of training a regression model and interpreting it as a binary classifier improves the accuracy. A total of 786 and 870 NIR spectra collected from laboratory reared An. gambiae and An. arabiensis, respectively, were used and pre-processed according to previously published protocols. The ANN regression model scored root mean squared error (RMSE) of 1.6 ± 0.2 for An. gambiae and 2.8 ± 0.2 for An. arabiensis; whereas the PLS regression model scored RMSE of 3.7 ± 0.2 for An. gambiae, and 4.5 ± 0.1 for An. arabiensis. When we interpreted regression models as binary classifiers, the accuracy of the ANN regression model was 93.7 ± 1.0% for An. gambiae, and 90.2 ± 1.7% for An. arabiensis; while PLS regression model scored the accuracy of 83.9 ± 2.3% for An. gambiae, and 80.3 ± 2.1% for An. arabiensis. We also find that a directly trained binary classifier yields higher age estimation accuracy than a regression model interpreted as a binary classifier. A directly trained ANN binary classifier scored an accuracy of 99.4 ± 1.0 for An. gambiae and 99.0 ± 0.6% for An. arabiensis; while a directly trained PLS binary classifier scored 93.6 ± 1.2% for An. gambiae and 88.7 ± 1.1% for An. arabiensis. We further tested the reproducibility of these results on different independent mosquito datasets. ANNs scored higher estimation accuracies than when the same age models are trained using PLS. Regardless of the model architecture, directly trained binary classifiers scored higher accuracies on classifying age of mosquitoes than regression models translated as binary classifiers. Conclusion
We recommend training models to estimate age of An. arabiensis and An. gambiae using ANN model architectures (especially for datasets with at least 70 mosquitoes per age group) and direct training of binary classifier instead of training a regression model and interpreting it as a binary classifier
Grassy Weeds
Grassy weeds are a problem in all field crops. They must be identified at early stages of growth so they can be controlled before crop yields are seriously threatened. Control measures are not the same for all grassy weeds, so accurate seedling identification is essential. Most grassy weeds and grain crops look very much alike in the seedling stages. However, if you look closely (a small hand lens helps) you can pick out the unique vegetative characteristics of each weed and crop seedling. Rudiments of the seed coat are helpful to distinguish crop seedlings from grassy weeds; however, seed coat is often absent. The vegetative characteristics that identify grasses are labeled in Fig 1. A summary of the unique characteristics of each species I given in Table 1
Evidence for Intergalactic Absorption in the TeV Gamma-Ray Spectrum of Mkn 501
The recent HEGRA observations of the blazar Mkn 501 show strong curvature in
the very high energy gamma-ray spectrum. Applying the gamma-ray opacity derived
from an empirically based model of the intergalactic infrared background
radiation field (IIRF), to these observations, we find that the intrinsic
spectrum of this source is consistent with a power-law: dN/dE~ E^-alpha with
alpha=2.00 +/- 0.03 over the range 500 GeV - 20 TeV. Within current synchrotron
self-Compton scenarios, the fact that the TeV spectral energy distribution of
Mkn 501 does not vary with luminosity, combined with the correlated, spectrally
variable emission in X-rays, as observed by the BeppoSAX and RXTE instruments,
also independently implies that the intrinsic spectrum must be close to
alpha=2. Thus, the observed curvature in the spectrum is most easily understood
as resulting from intergalactic absorption.Comment: 7 pages, 1 figure, accepted in ApJ Letters 1999 April
Neurotensin NTS1 and NTS2 receptor agonists produce anxiolytic-like effects in the 22-kHz ultrasonic vocalization model in rats
Neurotensin is a neuropeptide neurotransmitter that interacts with multiple neurotransmitter systems, including those regulating amygdalar function, via NTS1 and NTS2 receptors. Both receptors are expressed in the amygdala and agonists for NTS1 or NTS2 receptors have exhibited anxiolytic effects in animal models. Systemic adminstration of NTS1 receptor agonist PD149163 was recently shown to reduce footshock conditioned 22-kHz ultrasonic vocalizations in rats, suggesting that PD149163 produced an anxiolytic effect. The effects that neurotensin may have or a selective NTS2receptor agonist may have on 22-kHz vocalizations has yet to be examined. The current study evaluated the effects of intracerebroventricularly administered neurotensin (0.1–10.0 μg), PD149163 (0.1–10.0 ng), or the NTS2 receptor agonist JMV-431 (0.1–1.0 μg) on footshock conditioned 22-kHz vocalizations in male Wistar rats. Neurotensin, PD149163, and JMV-431 all significantly reduced the number 22-kHz calls. No changes in call duration were found, suggesting that non-specific drug effects do not account for the reductions in 22-kHz calls. These data support anxiolytic effects produced by activation of NTS1 or NTS2 receptors, and suggest that neurotensin plays a natural role in the expression of conditioned USVs. These data suggest that both receptor subtypes are putative pharmacologic targets
Documentation of a Gulf Sturgeon Spawning Site on the Yellow River, Alabama, USA
The Gulf Sturgeon Recovery Plan (USFWS, GSMFC and NMFS 1995) stressed the need to provide maximum protection to Gulf sturgeon spawning habitat. The approach employed by various Gulf sturgeon researchers, including ourselves, to document spawning has been to identify potential spawning habitat on the basis of physical characteristics and/or tracking data, collect eggs, and then raise the eggs in the laboratory until the point where the larval fish can be identified (e.g., Marchant and Shutters 1996, Sulak and Clugston 1998, 1999). However, collecting eggs in any appreciable number is usually difficult, and these eggs may not always be viable upon return to the laboratory. Molecular methods provide an alternative means of identifying the species represented by an egg. Notable examples related to sturgeon conservation include cases where molecular markers were used to verify the sources of commercially available caviar (DeSalle and Birstein 1996, Birstein et al. 1999).
Parauka and Giorgianni (2002) reported that potential Gulf sturgeon spawning habitat is present in the Yellow River; however, efforts to document spawning by the collection of eggs or larvae have been unsuccessful in the past. Herein, we report on the first successful collection of eggs from a potential spawning site on the Yellow River and the verification of their identity as Gulf sturgeon by using molecular methods
Parental preference for park attributes related to children’s use of parks in low-income, racial/ethnic diverse neighborhoods
HST/ACS Emission Line Imaging of Low Redshift 3CR Radio Galaxies I: The Data
We present 19 nearby (z<0.3) 3CR radio galaxies imaged at low- and
high-excitation as part of a Cycle 15 Hubble Space Telescope snapshot survey
with the Advanced Camera for Surveys. These images consist of exposures of the
H-alpha (6563 \AA, plus [NII] contamination) and [OIII] 5007 \AA emission lines
using narrow-band linear ramp filters adjusted according to the redshift of the
target. To facilitate continuum subtraction, a single-pointing 60 s line-free
exposure was taken with a medium-band filter appropriate for the target's
redshift. We discuss the steps taken to reduce these images independently of
the automated recalibration pipeline so as to use more recent ACS flat-field
data as well as to better reject cosmic rays. We describe the method used to
produce continuum-free (pure line-emission) images, and present these images
along with qualitative descriptions of the narrow-line region morphologies we
observe. We present H-alpha+[NII] and [OIII] line fluxes from aperture
photometry, finding the values to fall expectedly on the redshift-luminosity
trend from a past HST/WFPC2 emission line study of a larger, generally higher
redshift subset of the 3CR. We also find expected trends between emission line
luminosity and total radio power, as well as a positive correlation between the
size of the emission line region and redshift. We discuss the associated
interpretation of these results, and conclude with a summary of future work
enabled by this dataset.Comment: 18 pages, 12 figures, accepted for publication in ApJ
A microlensing measurement of dark matter fractions in three lensing galaxies
Direct measurements of dark matter distributions in galaxies are currently
only possible through the use of gravitational lensing observations.
Combinations of lens modelling and stellar velocity dispersion measurements
provide the best constraints on dark matter distributions in individual
galaxies, however they can be quite complex. In this paper, we use observations
and simulations of gravitational microlensing to measure the smooth (dark)
matter mass fraction at the position of lensed images in three lens galaxies:
MG 0414+0534, SDSS J0924+0219 and Q2237+0305. The first two systems consist of
early-type lens galaxies, and both display a flux ratio anomaly in their close
image pair. Anomalies such as these suggest a high smooth matter percentage is
likely, and indeed we prefer ~50 per cent smooth matter in MG 0414+0534, and
~80 per cent in SDSS J0924+0219 at the projected locations of the lensed
images. Q2237+0305 differs somewhat in that its lensed images lie in the
central kiloparsec of the barred spiral lens galaxy, where we expect stars to
dominate the mass distribution. In this system, we find a smooth matter
percentage that is consistent with zero.Comment: 7 pages, 4 figures. Accepted for publication in Ap
Which solar EUV indices are best for reconstructing the solar EUV irradiance ?
The solar EUV irradiance is of key importance for space weather. Most of the
time, however, surrogate quantities such as EUV indices have to be used by lack
of continuous and spectrally resolved measurements of the irradiance. The
ability of such proxies to reproduce the irradiance from different solar
atmospheric layers is usually investigated by comparing patterns of temporal
correlations. We consider instead a statistical approach. The TIMED/SEE
experiment, which has been continuously operating since Feb. 2002, allows for
the first time to compare in a statistical manner the EUV spectral irradiance
to five EUV proxies: the sunspot number, the f10.7, Ca K, and Mg II indices,
and the He I equivalent width.
Using multivariate statistical methods such as multidimensional scaling, we
represent in a single graph the measure of relatedness between these indices
and various strong spectral lines. The ability of each index to reproduce the
EUV irradiance is discussed; it is shown why so few lines can be effectively
reconstructed from them. All indices exhibit comparable performance, apart from
the sunspot number, which is the least appropriate. No single index can
satisfactorily describe both the level of variability on time scales beyond 27
days, and relative changes of irradiance on shorter time scales.Comment: 6 figures, to appear in Adv. Space. Re
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