1,408 research outputs found
Stochastic expansions using continuous dictionaries: L\'{e}vy adaptive regression kernels
This article describes a new class of prior distributions for nonparametric
function estimation. The unknown function is modeled as a limit of weighted
sums of kernels or generator functions indexed by continuous parameters that
control local and global features such as their translation, dilation,
modulation and shape. L\'{e}vy random fields and their stochastic integrals are
employed to induce prior distributions for the unknown functions or,
equivalently, for the number of kernels and for the parameters governing their
features. Scaling, shape, and other features of the generating functions are
location-specific to allow quite different function properties in different
parts of the space, as with wavelet bases and other methods employing
overcomplete dictionaries. We provide conditions under which the stochastic
expansions converge in specified Besov or Sobolev norms. Under a Gaussian error
model, this may be viewed as a sparse regression problem, with regularization
induced via the L\'{e}vy random field prior distribution. Posterior inference
for the unknown functions is based on a reversible jump Markov chain Monte
Carlo algorithm. We compare the L\'{e}vy Adaptive Regression Kernel (LARK)
method to wavelet-based methods using some of the standard test functions, and
illustrate its flexibility and adaptability in nonstationary applications.Comment: Published in at http://dx.doi.org/10.1214/11-AOS889 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Irrigation externalities: pricing and charges
Irrigation externalities: pricing and charges by Gavan Dwyer, Robert Douglas, Deb Peterson, Jo Chong and Kate Maddern was released on 14 March 2006. The paper discusses the nature and causes of environmental change related to rural water use, and provides a taxonomy of the many diverse types. It also examines the issues surrounding possible charges on water use for water related externalities. There have been few attempts by water utilities to incorporate externalities into full cost pricing of irrigation water. The aim of this Staff Working Paper was to: examine the extent to which charges imposed by irrigation water utilities could address externalities from irrigation water supply and use; and to develop a framework to identify and characterise changes in environmental conditions from the supply and use of irrigation water that may lead to environmental externalities. The authors found that many factors influence the extent to which charging for water would change water use. These include the volume of water available to irrigators, the extent to which trade can occur, the size of the charge or tax, the price responsiveness for irrigation water and the existing mechanisms to address externalities. A tax on water use may increase economic efficiency where external costs are related only to the level of water use. However, such a tax is an unsuitable instrument if the Government's policy objective is to reduce environmental damage to a predetermined level or to raise a target level of revenue to address the externalities. The views expressed in this paper are those of the staff involved and do not necessarily reflect those of the Productivity Commission.Resource /Energy Economics and Policy,
Threshold Resummation Effects in the Associated Production of Chargino and Neutralino at Hadron Colliders
We investigate the QCD effects in the associated production of the chargino
and the neutralino, and , in the Minimal
Supersymmetric Standard Model (MSSM) at both the Fermilab Tevatron and the CERN
Large Hadron Collider (LHC). We include the next-to-leading order (NLO) QCD
corrections (including supersymmetric QCD) and the threshold resummation
effects. Our results show that, compared to the NLO predictions, the threshold
resummation effects can increase the total cross sections by 3.6% and 3.9% for
the associated production of and
at the LHC, respectively, and by 4.7% for
those of at the Tevatron. In the invariant
mass distributions the resummation effects are significant for large invariant
mass. The threshold resummation reduces the dependence of the total cross
sections at the LHC (Tevatron) on the renormalization/factorization scales to
5% (4%) from up to 7% (11%) at NLO.Comment: revised version with midifications, several references adde
Efficient Photometric Selection of Quasars from the Sloan Digital Sky Survey: 100,000 z<3 Quasars from Data Release One
We present a catalog of 100,563 unresolved, UV-excess (UVX) quasar candidates
to g=21 from 2099 deg^2 of the Sloan Digital Sky Survey (SDSS) Data Release One
(DR1) imaging data. Existing spectra of 22,737 sources reveals that 22,191
(97.6%) are quasars; accounting for the magnitude dependence of this
efficiency, we estimate that 95,502 (95.0%) of the objects in the catalog are
quasars. Such a high efficiency is unprecedented in broad-band surveys of
quasars. This ``proof-of-concept'' sample is designed to be maximally
efficient, but still has 94.7% completeness to unresolved, g<~19.5, UVX quasars
from the DR1 quasar catalog. This efficient and complete selection is the
result of our application of a probability density type analysis to training
sets that describe the 4-D color distribution of stars and spectroscopically
confirmed quasars in the SDSS. Specifically, we use a non-parametric Bayesian
classification, based on kernel density estimation, to parameterize the color
distribution of astronomical sources -- allowing for fast and robust
classification. We further supplement the catalog by providing photometric
redshifts and matches to FIRST/VLA, ROSAT, and USNO-B sources. Future work
needed to extend the this selection algorithm to larger redshifts, fainter
magnitudes, and resolved sources is discussed. Finally, we examine some science
applications of the catalog, particularly a tentative quasar number counts
distribution covering the largest range in magnitude (14.2<g<21.0) ever made
within the framework of a single quasar survey.Comment: 35 pages, 11 figures (3 color), 2 tables, accepted by ApJS; higher
resolution paper and ASCII version of catalog available at
http://sdss.ncsa.uiuc.edu/qso/nbckde
Picosecond X-ray Absorption Spectroscopy of Photochemical Transient Species in Solution
A photoinduced Fe(II) spin crossover reaction in solution is studied with ultrafast x-ray absorption spectroscopy. The iron-nitrogen bond lengthens by 0.21+-0.03 Angstrom in the high-spin transient excited state relative to the ground state
Impact of oral meloxicam administered alone or in combination with gabapentin on experimentally induced lameness in beef calves
This study examined the pharmacokinetics and analgesic effect of oral meloxicam (MEL) administered alone or in combination with gabapentin (GABA) in an experimental bovine lameness model. Eighteen male British × Continental beef calves aged 4 to 6 mo and weighing 297 to 392 kg were randomly assigned to receive either 1) 0.5 mg/kg lactose monohydrate placebo (PLBO; n = 6), 2) 0.5 mg/kg MEL (n = 6), or 3) 0.5 mg/kg MEL combined with 15 mg/kg GABA (MEL-GABA; n = 6) once daily for 4 d. The first treatment was administered 4 h after a chemical synovitis/arthritis was induced with injection of 15 mg amphotericin B into the left hind lateral distal interphalangeal joint. Changes in activity were evaluated continuously with pedometers. Contact force, contact area, contact pressure, impulse, and stride length were recorded once daily with a pressure mat and visual lameness scores were determined by a masked observer using a 5-point scale. Cortisol and drug concentrations were determined daily by immunoassay and HPLC-mass spectrometry, respectively. Outcomes were compared statistically using a random effects mixed model and analysis of covariance. There was a positive association between lameness scores and serum cortisol concentrations (P = 0.02) and a negative association between lameness score and step count (P \u3c 0.0001), total force (P = 0.001), force applied to the lateral claw (P= 0.02), contact pressure (P = 0.005), and impulse of the lateral claw (P = 0.01). Step count was greater in MEL calves compared with PLBO (P = 0.008) and MEL-GABA (P = 0.04) calves. Impulse was greater in the MEL-GABA calves compared with the PLBO calves (P = 0.03). There was an inverse relationship between plasma MEL concentrations and lameness score (P = 0.02) and a positive association between MEL concentrations and force applied to the lateral claw (P = 0.03), total contact pressure (P = 0.03), and impulse on the lateral claw (P = 0.02). There was a tendency towards a positive association between GABA concentrations, total impulse, and impulse on the lateral claw (P = 0.08) and a negative associate between GABA concentrations and step count (P = 0.08). The results of this study suggest that MEL administered alone or in combination with GABA reduced the severity of lameness in calves following induction of lameness with amphotericin B. These findings have implications for developing analgesic protocols in lame calves that address both production and welfare concerns
m-Azipropofol (AziPm) a Photoactive Analogue of the Intravenous General Anesthetic Propofol
Propofol is the most commonly used sedative-hypnotic drug for noxious procedures, yet the molecular targets underlying either its beneficial or toxic effects remain uncertain. In order to determine targets and thereby mechanisms of propofol, we have synthesized a photoactivateable analogue by substituting an alkyldiazirinyl moiety for one of the isopropyl arms but in the meta position. m-Azipropofol retains the physical, biochemical, GABAA receptor modulatory, and in vivo activity of propofol and photoadducts to amino acid residues in known propofol binding sites in natural proteins. Using either mass spectrometry or radiolabeling, this reagent may be used to reveal sites and targets that underlie the mechanism of both the desirable and undesirable actions of this important clinical compound
A transcriptome-wide association study of Alzheimer's disease using prediction models of relevant tissues identifies novel candidate susceptibility genes.
Funder: University of Hawai'i at MānoaBACKGROUND: Genome-wide association studies (GWAS) have identified over 56 susceptibility loci associated with Alzheimer's disease (AD), but the genes responsible for these associations remain largely unknown. METHODS: We performed a large transcriptome-wide association study (TWAS) leveraging modified UTMOST (Unified Test for MOlecular SignaTures) prediction models of ten brain tissues that are potentially related to AD to discover novel AD genetic loci and putative target genes in 71,880 (proxy) cases and 383,378 (proxy) controls of European ancestry. RESULTS: We identified 53 genes with predicted expression associations with AD risk at Bonferroni correction threshold (P value < 3.38 × 10-6). Based on fine-mapping analyses, 21 genes at nine loci showed strong support for being causal. CONCLUSIONS: Our study provides new insights into the etiology and underlying genetic architecture of AD
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