4,649 research outputs found
Betting and Belief: Prediction Markets and Attribution of Climate Change
Despite much scientific evidence, a large fraction of the American public
doubts that greenhouse gases are causing global warming. We present a
simulation model as a computational test-bed for climate prediction markets.
Traders adapt their beliefs about future temperatures based on the profits of
other traders in their social network. We simulate two alternative climate
futures, in which global temperatures are primarily driven either by carbon
dioxide or by solar irradiance. These represent, respectively, the scientific
consensus and a hypothesis advanced by prominent skeptics. We conduct
sensitivity analyses to determine how a variety of factors describing both the
market and the physical climate may affect traders' beliefs about the cause of
global climate change. Market participation causes most traders to converge
quickly toward believing the "true" climate model, suggesting that a climate
market could be useful for building public consensus.Comment: All code and data for the model is available at
http://johnjnay.com/predMarket/. Forthcoming in Proceedings of the 2016
Winter Simulation Conference. IEEE Pres
Development of a space stable thermal control coatings for use in large space vehicles
The preparation and evaluation of zinc orthotitanate and of several new pigments and the environmental testing and evaluation of these pigments and of coatings made from them constitute the bulk of the work accomplished. New pigments were prepared and EPR spectra of pigments and their precursor compounds studied. Results of extensive testing of commercially-available, strippable, protective coatings are reported; Owens-Illinois 650 glass resin has been stabilized against progressive mechanical failures; and definite improvements have been noted. A zinc oxide pigmented lithium silicate paint has demonstrated very good ultraviolet stability
Forks in the Road
This Essay outlines a simple heuristic that will enable public and private policymakers to focus on the most important climate change mitigation strategies. Policymakers face a dizzying array of information, pressure from advocacy groups, and policy options, and it is easy to lose sight of the forest for the trees. Many policy options are attractive on the surface but either fail to meaningfully address the problem or are unlikely to be adopted in the foreseeable future. If policymakers make the right decision when confronting three essential choices or forks in the road, though, the result will be 60% to 70% reductions in greenhouse gas emissions, an amount that will keep widely-adopted climate mitigation goals in reach. The three options are decarbonization of the electrical grid, electrification of the motor vehicle fleet, and electrification of buildings. International, national, and subnational officials, philanthropists, corporate executives, advocacy group leaders, and households all have the ability to prioritize these three options in their regulatory, purchasing, and other actions. If they choose these three decarbonatization options, many other mistakes can be made without jeopardizing the achievement of widely adopted emissions targets. If they make the wrong choice, however, few combinations of other viable options can achieve the necessary reductions. In the face of a growing consensus that immediate, major emissions reductions are required, the forks in the road heuristic can provide policymakers with the framework necessary to make smart decisions and ignore the noise surrounding climate law and policy
Development of space stable thermal control coatings for use on large space vehicles
The evaluation and environmental testing of zinc orthotitanate pigments for use as space stable thermal control coatings on large space vehicles are discussed. Electron paramagnetic resonance spectra of the pigments and their precursor compounds are examined. A continuing study of the spectral intensity of mercury-argon and mercury-xenon sources in reported. Results of long term environmental testing of commercially available, strippable, protective coatings are discussed
Epidemics in Networks of Spatially Correlated Three-dimensional Root Branching Structures
Using digitized images of the three-dimensional, branching structures for
root systems of bean seedlings, together with analytical and numerical methods
that map a common 'SIR' epidemiological model onto the bond percolation
problem, we show how the spatially-correlated branching structures of plant
roots affect transmission efficiencies, and hence the invasion criterion, for a
soil-borne pathogen as it spreads through ensembles of morphologically complex
hosts. We conclude that the inherent heterogeneities in transmissibilities
arising from correlations in the degrees of overlap between neighbouring
plants, render a population of root systems less susceptible to epidemic
invasion than a corresponding homogeneous system. Several components of
morphological complexity are analysed that contribute to disorder and
heterogeneities in transmissibility of infection. Anisotropy in root shape is
shown to increase resilience to epidemic invasion, while increasing the degree
of branching enhances the spread of epidemics in the population of roots. Some
extension of the methods for other epidemiological systems are discussed.Comment: 21 pages, 8 figure
The vacuum-ultraviolet degradation of salt-spray-contaminated thermal control coatings
An experimental program in which salt-spray-exposed coatings have been irradiated is described and discussed
Gels under stress: the origins of delayed collapse
Attractive colloidal particles can form a disordered elastic solid or gel
when quenched into a two-phase region, if the volume fraction is sufficiently
large. When the interactions are comparable to thermal energies the
stress-bearing network within the gel restructures over time as individual
particle bonds break and reform. Typically, under gravity such weak gels show a
prolonged period of either no or very slow settling, followed by a sudden and
rapid collapse - a phenomenon known as delayed collapse. The link between local
bond breaking events and the macroscopic process of delayed collapse is not
well understood. Here we summarize the main features of delayed collapse and
discuss the microscopic processes which cause it. We present a plausible model
which connects the kinetics of bond breaking to gel collapse and test the model
by exploring the effect of an applied external force on the stability of a gel.Comment: Accepted version: 10 pages, 7 figure
Prominent effect of soil network heterogeneity on microbial invasion
Using a network representation for real soil samples and mathematical models for microbial spread, we show that the structural heterogeneity of the soil habitat may have a very significant influence on the size of microbial invasions of the soil pore space. In particular, neglecting the soil structural heterogeneity may lead to a substantial underestimation of microbial invasion. Such effects are explained in terms of a crucial interplay between heterogeneity in microbial spread and heterogeneity in the topology of soil networks. The main influence of network topology on invasion is linked to the existence of long channels in soil networks that may act as bridges for transmission of microorganisms between distant parts of soil
Complexity and anisotropy in host morphology make populations safer against epidemic outbreaks
One of the challenges in epidemiology is to account for the complex
morphological structure of hosts such as plant roots, crop fields, farms,
cells, animal habitats and social networks, when the transmission of infection
occurs between contiguous hosts. Morphological complexity brings an inherent
heterogeneity in populations and affects the dynamics of pathogen spread in
such systems. We have analysed the influence of realistically complex host
morphology on the threshold for invasion and epidemic outbreak in an SIR
(susceptible-infected-recovered) epidemiological model. We show that disorder
expressed in the host morphology and anisotropy reduces the probability of
epidemic outbreak and thus makes the system more resistant to epidemic
outbreaks. We obtain general analytical estimates for minimally safe bounds for
an invasion threshold and then illustrate their validity by considering an
example of host data for branching hosts (salamander retinal ganglion cells).
Several spatial arrangements of hosts with different degrees of heterogeneity
have been considered in order to analyse separately the role of shape
complexity and anisotropy in the host population. The estimates for invasion
threshold are linked to morphological characteristics of the hosts that can be
used for determining the threshold for invasion in practical applications.Comment: 21 pages, 8 figure
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