151 research outputs found
Lessening the hazards of Florida red tides: a common sense approach
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hoagland, P., Kirkpatrick, B., Jin, D., Kirkpatrick, G., Fleming, L. E., Ullmann, S. G., Beet, A., Hitchcock, G., Harrison, K. K., Li, Z. C., Garrison, B., Diaz, R. E., & Lovko, V. Lessening the hazards of Florida red tides: a common sense approach. Frontiers in Marine Science, 7, (2020): 538, doi:10.3389/fmars.2020.00538.In the Gulf of Mexico, especially along the southwest Florida coast, blooms of the dinoflagellate Karenia brevis are a coastal natural hazard. The organism produces a potent class of toxins, known as brevetoxins, which are released following cell lysis into ocean or estuarine waters or, upon aerosolization, into the atmosphere. When exposed to sufficient levels of brevetoxins, humans may suffer from respiratory, gastrointestinal, or neurological illnesses. The hazard has been exacerbated by the geometric growth of human populations, including both residents and tourists, along Florida’s southwest coast. Impacts to marine organisms or ecosystems also may occur, such as fish kills or deaths of protected mammals, turtles, or birds. Since the occurrence of a severe Karenia brevis bloom off the southwest Florida coast three-quarters of a century ago, there has been an ongoing debate about the best way for humans to mitigate the impacts of this hazard. Because of the importance of tourism to coastal Florida, there are incentives for businesses and governments alike to obfuscate descriptions of these blooms, leading to the social amplification of risk. We argue that policies to improve the public’s ability to understand the physical attributes of blooms, specifically risk communication policies, are to be preferred over physical, chemical, or biological controls. In particular, we argue that responses to this type of hazard must emphasize maintaining the continuity of programs of scientific research, environmental monitoring, public education, and notification. We propose a common-sense approach to risk communication, comprising a simplification of the public provision of existing sources of information to be made available on a mobile website.The research leading to these results was supported by the US National Science Foundation (NSF) under NSF Grant No. CNH 1009106. PH and DJ acknowledge the complementary support under NSF Grant No. PFI/BIC 1534054
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Surface-Enforced Alignment of Reprogrammable Liquid Crystalline Elastomers
Liquid crystalline elastomers (LCEs) are stimuli-responsive materials capable of undergoing large deformations. The thermomechanical response of LCEs is attributable to the coupling of polymer network properties and disruption of order between liquid crystalline mesogens. Complex deformations have been realized in LCEs by either programming the nematic director via surface-enforced alignment or localized mechanical deformation in materials incorporating dynamic covalent chemistries. Here, the preparation of LCEs via thiol-Michael addition reaction is reported that are amenable to surface-enforced alignment. Afforded by the thiol-Michael addition reaction, dynamic covalent bonds are uniquely incorporated in chemistries subject to surface-enforce alignment. Accordingly, LCEs prepared with complex director profiles are able to be programmed and reprogrammed by (re)activating the dynamic covalent chemistry to realize distinctive shape transformations.
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Simple, Fast and Accurate Implementation of the Diffusion Approximation Algorithm for Stochastic Ion Channels with Multiple States
The phenomena that emerge from the interaction of the stochastic opening and
closing of ion channels (channel noise) with the non-linear neural dynamics are
essential to our understanding of the operation of the nervous system. The
effects that channel noise can have on neural dynamics are generally studied
using numerical simulations of stochastic models. Algorithms based on discrete
Markov Chains (MC) seem to be the most reliable and trustworthy, but even
optimized algorithms come with a non-negligible computational cost. Diffusion
Approximation (DA) methods use Stochastic Differential Equations (SDE) to
approximate the behavior of a number of MCs, considerably speeding up
simulation times. However, model comparisons have suggested that DA methods did
not lead to the same results as in MC modeling in terms of channel noise
statistics and effects on excitability. Recently, it was shown that the
difference arose because MCs were modeled with coupled activation subunits,
while the DA was modeled using uncoupled activation subunits. Implementations
of DA with coupled subunits, in the context of a specific kinetic scheme,
yielded similar results to MC. However, it remained unclear how to generalize
these implementations to different kinetic schemes, or whether they were faster
than MC algorithms. Additionally, a steady state approximation was used for the
stochastic terms, which, as we show here, can introduce significant
inaccuracies. We derived the SDE explicitly for any given ion channel kinetic
scheme. The resulting generic equations were surprisingly simple and
interpretable - allowing an easy and efficient DA implementation. The algorithm
was tested in a voltage clamp simulation and in two different current clamp
simulations, yielding the same results as MC modeling. Also, the simulation
efficiency of this DA method demonstrated considerable superiority over MC
methods.Comment: 32 text pages, 10 figures, 1 supplementary text + figur
Correlations and Renormalization in Lattice Gases
A complete formulation is given of an exact kinetic theory for lattice gases.
This kinetic theory makes possible the calculation of corrections to the usual
Boltzmann / Chapman-Enskog analysis of lattice gases due to the buildup of
correlations. It is shown that renormalized transport coefficients can be
calculated perturbatively by summing terms in an infinite series. A
diagrammatic notation for the terms in this series is given, in analogy with
the diagrammatic expansions of continuum kinetic theory and quantum field
theory. A closed-form expression for the coefficients associated with the
vertices of these diagrams is given. This method is applied to several standard
lattice gases, and the results are shown to correctly predict experimentally
observed deviations from the Boltzmann analysis.Comment: 94 pages, pure LaTeX including all figure
CHANS : the characteristics of cost-effective policy responses for harmful algal blooms [poster]
Presented at CERF 2015: Grand Challenges in Coastal & Estuarine Science, Portland, Oregon, November 8 - 12, 2015 and at the Eighth Symposium on Harmful Algae in the U.S., Long Beach, California, November 15 – 19, 2015A growing concern for coastal management is the choice of appropriate public or private responses to
HABs as a natural hazard. Considerable efforts have been devoted to understanding the scientific
aspects of HABs, including their distributions in space and time, their ecological roles, and the nature of
their toxic effects, among others. Much energy also has been directed at exploring socio-economic
impacts and identifying potential management actions, including actions to prevent, control, or mitigate
blooms. Using blooms of Florida red tide (Karenia brevis) as a case study, we develop an approach to the
choice of policy responses to K. brevis blooms. Importantly, several new types of public health,
environmental, and socio-economic impacts now are beginning to be revealed, including human gastrointestinal
and potential neurological illnesses; morbidities and mortalities of protected species, including
manatees, cetaceans, and sea turtles; increased numbers of hospital emergency room visits for the
elderly; increased respiratory morbidities in workers, such as beach lifeguards; and potential reduced K-
12 school attendance. Optimal policy responses to this hazard are likely to depend critically upon why
and where a bloom occurs, its spatial and temporal scales and toxicity, and the nature of its impacts. In
the face of significant ongoing scientific uncertainties, and given estimates of impacts, we find that
policies to expand and stabilize scientific research programs and environmental monitoring efforts, to
develop and implement education programs for both residents and tourists, and to communicate the
physical aspects of blooms to the public in a timely fashion are likely optimal.This research was sponsored by the National Science Foundation under NSF/CNH Grant No. 1009106
CHANS : modeling the dynamics of HABs, human communities, and policy choices along the Florida Gulf Coast
Presented at the Eighth Symposium on
Harmful Algae in the U.S.,
Long Beach, California,
November 15 – 19, 2015Coupled human-nature systems (CHANS) involve dynamic interactions between humans and nature,
often influenced by and affecting the distinct dynamic characteristics of each component. We present
an overview of an ongoing interdisciplinary research program focused on a specific type of systems that
couple expanding and fluctuating human coastal populations to episodic blooms of toxic marine algae,
drawing examples primarily from human interactions with blooms of the toxic dinoflagellate Karenia
brevis from the eastern Gulf of Mexico (“Florida red tides”). We introduce a set of HAB Symposium
“speed” presentations and associated posters based on multi-disciplinary research. Using extant, but
extraordinary, data to specify empirical models, this program of research has focused on characterizing
the influence of anthropogenic sources on K. brevis blooms, assessing the public health and economic
impacts of these blooms in an exposure-response framework, and defining the choice of appropriate
human policy responses to the hazard. We present examples of the generic aspects of CHANS systems in
the context of Florida red tides, and we discuss also some of the challenges involved in compiling and
analyzing the relevant data to support our positive and normative analytical efforts.NSF/CNH NO.100910
Detection of brown dwarf-like objects in the core of NGC3603
We use near-infrared data obtained with the Wide Field Camera 3 (WFC3) on the
Hubble Space Telescope to identify objects having the colors of brown dwarfs
(BDs) in the field of the massive galactic cluster NGC 3603. These are
identified through use of a combination of narrow and medium band filters
spanning the J and H bands, and which are particularly sensitive to the
presence of the 1.3-1.5{\mu}m H2O molecular band - unique to BDs. We provide a
calibration of the relationship between effective temperature and color for
both field stars and for BDs. This photometric method provides effective
temperatures for BDs to an accuracy of {\pm}350K relative to spectroscopic
techniques. This accuracy is shown to be not significantly affected by either
stellar surface gravity or uncertainties in the interstellar extinction. We
identify nine objects having effective temperature between 1700 and 2200 K,
typical of BDs, observed J-band magnitudes in the range 19.5-21.5, and that are
strongly clustered towards the luminous core of NGC 3603. However, if these are
located at the distance of the cluster, they are far too luminous to be normal
BDs. We argue that it is unlikely that these objects are either artifacts of
our dataset, normal field BDs/M-type giants or extra-galactic contaminants and,
therefore, might represent a new class of stars having the effective
temperatures of BDs but with luminosities of more massive stars. We explore the
interesting scenario in which these objects would be normal stars that have
recently tidally ingested a Hot Jupiter, the remnants of which are providing a
short-lived extended photosphere to the central star. In this case, we would
expect them to show the signature of fast rotation.Comment: 26 Pages, 8 Figures, Accepted for publication on Ap
Cluster Hybrid Monte Carlo Simulation Algorithms
We show that addition of Metropolis single spin-flips to the Wolff cluster
flipping Monte Carlo procedure leads to a dramatic {\bf increase} in
performance for the spin-1/2 Ising model. We also show that adding Wolff
cluster flipping to the Metropolis or heat bath algorithms in systems where
just cluster flipping is not immediately obvious (such as the spin-3/2 Ising
model) can substantially {\bf reduce} the statistical errors of the
simulations. A further advantage of these methods is that systematic errors
introduced by the use of imperfect random number generation may be largely
healed by hybridizing single spin-flips with cluster flipping.Comment: 16 pages, 10 figure
The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic
data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data
release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median
z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar
spectra, along with the data presented in previous data releases. These spectra
were obtained with the new BOSS spectrograph and were taken between 2009
December and 2011 July. In addition, the stellar parameters pipeline, which
determines radial velocities, surface temperatures, surface gravities, and
metallicities of stars, has been updated and refined with improvements in
temperature estimates for stars with T_eff<5000 K and in metallicity estimates
for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars
presented in DR8, including stars from SDSS-I and II, as well as those observed
as part of the SDSS-III Sloan Extension for Galactic Understanding and
Exploration-2 (SEGUE-2).
The astrometry error introduced in the DR8 imaging catalogs has been
corrected in the DR9 data products. The next data release for SDSS-III will be
in Summer 2013, which will present the first data from the Apache Point
Observatory Galactic Evolution Experiment (APOGEE) along with another year of
data from BOSS, followed by the final SDSS-III data release in December 2014.Comment: 9 figures; 2 tables. Submitted to ApJS. DR9 is available at
http://www.sdss3.org/dr
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