1,028 research outputs found
Population response of triploid grass carp to declining levels of hydrilla in the Santee Cooper Reservoirs, South Carolina
Approximately 768,500 triploid grass carp (
Ctenopharyngodon
idella
Valenciennes) were stocked into the Santee Cooper
reservoirs, South Carolina between 1989 and 1996 to
control hydrilla (
Hydrilla verticillata
(L.f.) Royle). Hydrilla
coverage was reduced from a high of 17,272 ha during 1994
to a few ha by 1998. During 1997, 1998 and 1999, at least 98
triploid grass carp were collected yearly for population monitoring.
Estimates of age, growth, and mortality, as well as
population models, were used in the study to monitor triploid
grass carp and predict population trends. Condition declined
from that measured during a previous study in 1994.
The annual mortality rate was estimated at 28% in 1997, 32%
in 1998 and 39% in 1999; however, only the 1999 mortality
rate was significantly different. Few (2 out of 98) of the triploid
grass carp collected during 1999 were older than age 9.
We expect increased mortality due to an aging population
and sparse hydrilla coverage. During 1999, we estimated about
63,000 triploid grass carp system wide and project less than
3,000 fish by 2004, assuming no future stocking.
management, population size
Ctenopharyngodon idella, Hydrill
Cross-calibration of atomic pressure sensors and deviation from quantum diffractive collision universality for light particles
The total room-temperature, velocity-averaged cross section for atom-atom and
atom-molecule collisions is well approximated by a universal function depending
only on the magnitude of the leading order dispersion coefficient, . This
feature of the total cross section together with the universal function for the
energy distribution transferred by glancing angle collisions ()
can be used to empirically determine the total collision cross section and
realize a self-calibrating, vacuum pressure standard. This was previously
validated for Rb+N and Rb+Rb collisions. However, the post-collision energy
distribution is expected to deviate from in the limit of small
and small reduced mass. Here we observe this deviation experimentally by
performing a direct cross-species loss rate comparison between Rb+H and
Li+H and using the \textit{ab initio} value of . We find a velocity averaged total collision cross
section ratio, . Based on an
\textit{ab initio} computation of m/s, we deduce m/s,
in agreement with a Rb+H \textit{ab initio} value of .By contrast, fitting the Rb+H loss rate as a
function of trap depth to the universal function we find
m/s. Finally, this work demonstrates how to perform a cross-calibration of
sensor atoms to extend and enhance the cold atom based pressure sensor.Comment: 14 pages, 9 figure
Self-reported cocaine use, emergency physician testing and outcomes in suspected acute coronary syndromes: a nested matched case–control study
A study of the centrally produced pi0pi0pi0 channel in pp interactions at 450 GeV/c
The reaction pp -> pf (pi0pi0pi0) ps has been studied at 450 GeV/c. The
pi0pi0pi0 effective mass spectrum shows clear eta(547) and pi2(1670) signals.
Branching ratios for the eta(547) and pi_2(1670) are given as well as upper
limits for the decays of the omega(782), a1(1260) and a2(1320) into 3pi0.Comment: 10 pages, Latex, 4 Figure
ACCESS: A Visual to Near-infrared Spectrum of the Hot Jupiter WASP-43b with Evidence of , but no evidence of Na or K
We present a new ground-based visual transmission spectrum of the hot Jupiter
WASP-43b, obtained as part of the ACCESS Survey. The spectrum was derived from
four transits observed between 2015 and 2018, with combined wavelength coverage
between 5,300 \r{A}-9,000 \r{A} and an average photometric precision of 708 ppm
in 230 \r{A} bins. We perform an atmospheric retrieval of our transmission
spectrum combined with literature HST/WFC3 observations to search for the
presence of clouds/hazes as well as Na, K, H, and planetary
absorption and stellar spot contamination over a combined spectral range of
5,318 \r{A}-16,420 \r{A}. We do not detect a statistically significant presence
of Na I or K I alkali lines, or H in the atmosphere of WASP-43b. We
find that the observed transmission spectrum can be best explained by a
combination of heterogeneities on the photosphere of the host star and a clear
planetary atmosphere with . This model yields a log-evidence of
higher than a flat (featureless) spectrum. In particular, the
observations marginally favor the presence of large, low-contrast spots over
the four ACCESS transit epochs with an average covering fraction and temperature contrast . Within the planet's atmosphere, we recover a log
volume mixing ratio of , which is consistent with
previous abundance determinations for this planet.Comment: 27 pages, 18 figures, 7 tables. Accepted for publication in AJ.
Updated affiliation
ACCESS: An optical transmission spectrum of the high-gravity, hot Jupiter HAT-P-23b
We present a new ground-based visible transmission spectrum of the
high-gravity, hot Jupiter HAT-P-23b, obtained as part of the ACCESS project. We
derive the spectrum from five transits observed between 2016 and 2018, with
combined wavelength coverage between 5200 {\AA} - 9269 {\AA} in 200 {\AA} bins,
and with a median precision of 247 ppm per bin. HAT-P-23b's relatively high
surface gravity (g ~ 30 m/s^2), combined with updated stellar and planetary
parameters from Gaia DR2, gives a 5-scale-height signal of 384 ppm for a
hydrogen-dominated atmosphere. Bayesian models favor a clear atmosphere for the
planet with the tentative presence of TiO, after simultaneously modeling
stellar contamination, using spots parameter constraints from photometry. If
confirmed, HAT-P-23b would be the first example of a high-gravity gas giant
with a clear atmosphere observed in transmission at optical/NIR wavelengths;
therefore, we recommend expanding observations to the UV and IR to confirm our
results and further characterize this planet. This result demonstrates how
combining transmission spectroscopy of exoplanet atmospheres with long-term
photometric monitoring of the host stars can help disentangle the exoplanet and
stellar activity signals.Comment: 28 pages, 18 Figures, accepted for publication in AJ. arXiv admin
note: text overlap with arXiv:1911.0335
ACCESS: Confirmation of a Clear Atmosphere for WASP-96b and a Comparison of Light Curve Detrending Techniques
One of the strongest features was observed in WASP-96b. To
confirm this novel detection, we provide a new 475-825nm transmission spectrum
obtained with Magellan/IMACS, which indeed confirms the presence of a broad
sodium absorption feature. We find the same result when reanalyzing the
400-825nm VLT/FORS2 data. We also utilize synthetic data to test the
effectiveness of two common detrending techniques: (1) a Gaussian processes
(GP) routine, and (2) common-mode correction followed by polynomial correction
(CMC+Poly). We find that both methods poorly reproduce the absolute transit
depths but maintain their true spectral shape. This emphasizes the importance
of fitting for offsets when combining spectra from different sources or epochs.
Additionally, we find that for our datasets both methods give consistent
results, but CMC+Poly is more accurate and precise. We combine the
Magellan/IMACS and VLT/FORS2 spectra with literature 800-1644nm HST/WFC3
spectra, yielding a global spectrum from 400-1644nm. We used the PLATON and
Exoretrievals retrieval codes to interpret this spectrum, and find that both
yield relatively deeper pressures where the atmosphere is optically thick at
log-pressures between and 0.29 bars,
respectively. Exoretrievals finds a solar to super-solar and log-mixing ratios of and ,
respectively, while PLATON finds an overall metallicity of
dex. Therefore, our findings are
in agreement with literature and support the inference that the terminator of
WASP-96b has few aerosols obscuring prominent features in the optical to
near-infrared (near-IR) spectrum.Comment: ACCEPT by AJ July 5th 202
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