9,573 research outputs found
Likelihood-based statistical estimation from quantized data
Most standard statistical methods treat numerical data as if they were real (infinitenumber- of-decimal-places) observations. The issue of quantization or digital resolution is recognized by engineers and metrologists, but is largely ignored by statisticians and can render standard statistical methods inappropriate and misleading. This article discusses some of the difficulties of interpretation and corresponding difficulties of inference arising in even very simple measurement contexts, once the presence of quantization is admitted. It then argues (using the simple case of confidence interval estimation based on a quantized random sample from a normal distribution as a vehicle) for the use of statistical methods based on rounded data likelihood functions as an effective way of dealing with the issue. --
INTEGRATED ASSESSMENT OF ENVIRONMENTAL EFFECTS FROM AGRICULTURAL PRODUCTION
Agriculture's impact on the environment is a complex research problem. A challenge to future economic research is to account for the interrelationship between agricultural production activities, soil productivity, erosion, and water quality. It will become increasingly important to determine not only the economic consequences, but also the environmental effectiveness of alternative policies aimed at improving resource use and quality. The application of biophysical simulation models to environmental quality problems provides a means to better understand the complex interaction between agricultural production and environmental quality.Environmental Economics and Policy,
"GREEN TAXES": IMPACTS ON NATIONAL INCOME, SOCIAL WELFARE, AND ENVIRONMENTAL QUALITY
Two taxation schemes were designed to be included in a multi-regional multi-sectoral General Equilibrium model for reducing the use of commercial fertilizers, with the goal of alleviating surface water pollution. Under the 500% tax rate, results showed that 0.1% of the national income was given up in order to exchange for a 3% reduction in the fertilizer application used as an intermediate input. Furthermore environmental quality would be improved by 3%, if a linear relationship existed between the changes in intermediate fertilizer use and the improvement in environmental quality.Environmental Economics and Policy,
Likelihood-Based Statistical Estimation from Quantized Data
Most standard statistical methods treat numerical data as if they were real (infinite-number-of-decimal-places) observations. The issue of quantization or digital resolution is recognized by engineers and metrologists, but is largely ignored by statisticians and can render standard statistical methods inappropriate and misleading. This article discusses some of the difficulties of interpretation and corresponding difficulties of inference arising in even very simple measurement contexts, once the presence of quantization is admitted. It then argues (using the simple case of confidence interval estimation based on a quantized random sample from a normal distribution as a vehicle) for the use of statistical methods based on “rounded data likelihood functions” as an effective way of dealing with the issue
Cooperative gas adsorption without a phase transition in metal-organic frameworks
Cooperative adsorption of gases by porous frameworks permits more efficient
uptake and removal than does the more usual non-cooperative (Langmuir-type)
adsorption. Cooperativity, signaled by a step-like isotherm, is usually
attributed to a phase transition of the framework. However, the class of
metal-organic frameworks mmen-M(dobpdc) exhibit cooperative adsorption of
CO2 but show no evidence of a phase transition. Here we show how cooperativity
emerges in these frameworks in the absence of a phase transition. We use a
combination of quantum and statistical mechanics to show that cooperativity
results from a sharp but finite increase, with pressure, of the mean length of
chains of CO2 molecules that polymerize within the framework. Our study
provides microscopic understanding of the emergent features of cooperative
binding, including the position, slope and height of the isotherm step, and
indicates how to optimize gas storage and separation in these materials.Comment: 18 pages, 11 figure
Tuning oxo formation energies using spectator ligands in the MIL-100 metal organic framework
https://tigerprints.clemson.edu/csrp/1008/thumbnail.jp
Observations of X-rays and Thermal Dust Emission from the Supernova Remnant Kes 75
We present Spitzer Space Telescope and Chandra X-ray Observatory observations
of the composite Galactic supernova remnant Kes 75 (G29.7-0.3). We use the
detected flux at 24 microns and hot gas parameters from fitting spectra from
new, deep X-ray observations to constrain models of dust emission, obtaining a
dust-to-gas mass ratio M_dust/M_gas ~0.001. We find that a two-component
thermal model, nominally representing shocked swept-up interstellar or
circumstellar material and reverse-shocked ejecta, adequately fits the X-ray
spectrum, albeit with somewhat high implied densities for both components. We
surmise that this model implies a Wolf-Rayet progenitor for the remnant. We
also present infrared flux upper limits for the central pulsar wind nebula.Comment: 7 pages, 2 tables, 4 figures, uses emulateapj. Accepted for
publication in Ap
Structural and functional brain changes following four weeks of unimanual motor training: evidence from fMRI-guided diffusion MRI tractography
We have reported reliable changes in behaviour, brain structure and function in 24 healthy right-handed adults who practiced a finger-thumb opposition sequence task with their left hand for 10 mins daily, over four weeks. Here we extend these findings by employing diffusion MRI to investigate white-matter changes in the corticospinal tract, basal-ganglia, and connections of the dorsolateral prefrontal cortex. Twenty-three participant datasets were available with pre-training and post-training scans. Task performance improved in all participants (mean: 52.8%, SD: 20.0%; group
Identification of a novel retroviral gene unique to human immunodeficiency virus type 2 and simian immunodeficiency virus SIVMAC
Human and simian immunodeficiency-associated retroviruses are extraordinarily complex, containing at least five genes, tat, art, sor, R, and 3' orf, in addition to the structural genes gag, pol, and env. Recently, nucleotide sequence analysis of human immunodeficiency virus type 2 (HIV-2) and simian immunodeficiency virus SIVMAC revealed the existence of still another open reading frame, termed X, which is highly conserved between these two viruses but absent from HIV-1. In this report, we demonstrate for the first time that the X open reading frame represents a functional retroviral gene in both HIV-2 and SIVMAC and that it encodes a virion-associated protein of 14 and 12 kilodaltons, respectively. We also describe the production of recombinant TrpE/X fusion proteins in Escherichia coli and show that sera from some HIV-2-infected individuals specifically recognize these proteins
Using the Rosat Catalogue to find Counterparts for Unidentified Objects in the 1st Fermi/LAT Catalogue
There are a total of 1451 gamma-ray emitting objects in the Fermi Large Area
Telescope First Source Catalogue. The point source location accuracy of
typically a few arcminutes has allowed the counterparts for many of these
sources to be found at other wavelengths, but even so there are 630 which are
described as having no plausible counterpart at 80% confidence. In order to
help identify the unknown objects, we have cross-correlated the positions of
these sources with the Rosat All Sky Survey Bright Source Catalogue. In this
way, for Fermi sources which have a possible counterpart in soft X-rays, we can
use the, much smaller, Rosat error box to search for identifications. We find a
strong correlation between the two samples and calculate that there are about
60 sources with a Rosat counterpart. Using the Rosat error boxes we provide
tentative associations for half of them, demonstrate that the majority of these
are either blazars or blazar candidates and give evidence that most belong to
the BL Lac class. Given that they are X-ray selected and most are high
synchrotron peaked objects, which indicates the presence of high energy
electrons, these sources are also good candidates for TeV emission, and
therefore good probes of the extragalactic background light.Comment: 9 pages, 1 figure; Accepted for publication in MNRA
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