17,807 research outputs found
One-parameter extension of the Doi-Peliti formalism and relation with orthogonal polynomials
An extension of the Doi-Peliti formalism for stochastic chemical kinetics is
proposed. Using the extension, path-integral expressions consistent with
previous studies are obtained. In addition, the extended formalism is naturally
connected to orthogonal polynomials. We show that two different orthogonal
polynomials, i.e., Charlier polynomials and Hermite polynomials, can be used to
express the Doi-Peliti formalism explicitly.Comment: 10 page
Doubly stochastic continuous-time hidden Markov approach for analyzing genome tiling arrays
Microarrays have been developed that tile the entire nonrepetitive genomes of
many different organisms, allowing for the unbiased mapping of active
transcription regions or protein binding sites across the entire genome. These
tiling array experiments produce massive correlated data sets that have many
experimental artifacts, presenting many challenges to researchers that require
innovative analysis methods and efficient computational algorithms. This paper
presents a doubly stochastic latent variable analysis method for transcript
discovery and protein binding region localization using tiling array data. This
model is unique in that it considers actual genomic distance between probes.
Additionally, the model is designed to be robust to cross-hybridized and
nonresponsive probes, which can often lead to false-positive results in
microarray experiments. We apply our model to a transcript finding data set to
illustrate the consistency of our method. Additionally, we apply our method to
a spike-in experiment that can be used as a benchmark data set for researchers
interested in developing and comparing future tiling array methods. The results
indicate that our method is very powerful, accurate and can be used on a single
sample and without control experiments, thus defraying some of the overhead
cost of conducting experiments on tiling arrays.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS248 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Linear density response function in the projector-augmented wave method: Applications to solids, surfaces, and interfaces
We present an implementation of the linear density response function within
the projector-augmented wave (PAW) method with applications to the linear
optical and dielectric properties of both solids, surfaces, and interfaces. The
response function is represented in plane waves while the single-particle
eigenstates can be expanded on a real space grid or in atomic orbital basis for
increased efficiency. The exchange-correlation kernel is treated at the level
of the adiabatic local density approximation (ALDA) and crystal local field
effects are included. The calculated static and dynamical dielectric functions
of Si, C, SiC, AlP and GaAs compare well with previous calculations. While
optical properties of semiconductors, in particular excitonic effects, are
generally not well described by ALDA, we obtain excellent agreement with
experiments for the surface loss function of the Mg(0001) surface with plasmon
energies deviating by less than 0.2 eV. Finally, we apply the method to study
the influence of substrates on the plasmon excitations in graphene. On
SiC(0001), the long wavelength plasmons are significantly damped although
their energies remain almost unaltered. On Al(111) the plasmon is
completely quenched due to the coupling to the metal surface plasmon.Comment: 11 pages, 8 figures, articl
Double resonance in the infinite-range quantum Ising model
We study quantum resonance behavior of the infinite-range kinetic Ising model
at zero temperature. Numerical integration of the time-dependent Schr\"odinger
equation in the presence of an external magnetic field in the direction is
performed at various transverse field strengths . It is revealed that two
resonance peaks occur when the energy gap matches the external driving
frequency at two distinct values of , one below and the other above the
quantum phase transition. From the similar observations already made in
classical systems with phase transitions, we propose that the double resonance
peaks should be a generic feature of continuous transitions, for both quantum
and classical many-body systems.Comment: 4 pages, 5 figure
Finite-volume Hamiltonian method for coupled channel interactions in lattice QCD
Within a multi-channel formulation of scattering, we investigate the
use of the finite-volume Hamiltonian approach to resolve scattering observables
from lattice QCD spectra. The asymptotic matching of the well-known L\"uscher
formalism encodes a unique finite-volume spectrum. Nevertheless, in many
practical situations, such as coupled-channel systems, it is advantageous to
interpolate isolated lattice spectra in order to extract physical scattering
parameters. Here we study the use of the Hamiltonian framework as a
parameterisation that can be fit directly to lattice spectra. We find that with
a modest amount of lattice data, the scattering parameters can be reproduced
rather well, with only a minor degree of model dependence.Comment: 25 pages, 16 figure
4p states and X-Ray Spectroscopy
The 4p states in transition metals and their compounds usually play minor
roles on their physical quantities. Recent development of resonant x-ray
scattering (RXS) at the K-edge of transition metals, however, casts light on
the 4p states, because the signals on orbital and magnetic superlattice spots
are brought about by the modulation in the 4p states. The 4p states are
extending in solids and thereby sensitive to electronic states at neighboring
sites. This characteristic determines the mechanism of RXS that the intensity
on the orbital superlattice spots are mainly generated by the lattice
distortion and those on magnetic superlattice spots by the coupling of the 4p
states with the orbital polarization in the 3d states at neighboring sites.
Taking up typical examples for orbital and magnetic RXS, we demonstrate these
mechanisms on the basis of the band structure calculation. Finally, we study
the MCD spectra at the K-edge, demonstrating that the same mechanism as the
magnetic RXS is working.Comment: 9 pages, 9 figures, submitted to Physica Scripta (comment
A key to room-temperature ferromagnetism in Fe-doped ZnO: Cu
Successful synthesis of room-temperature ferromagnetic semiconductors,
ZnFeO, is reported. The essential ingredient in achieving
room-temperature ferromagnetism in bulk ZnFeO was found to be
additional Cu doping. A transition temperature as high as 550 K was obtained in
ZnFeCuO; the saturation magnetization at room
temperature reached a value of per Fe. Large
magnetoresistance was also observed below K.Comment: 11 pages, 4 figures; to appear in Appl. Phys. Let
Value-Added Meat: Measuring Past Successes and Predicting Future Winners
Livestock industries are significantly affected by changes in consumer behaviour. In order to add value to meat and livestock production, many firms and farms are supporting the development of new products – these products can differ by credence attribute, by degree of processing and by marketing strategies. The literature suggests that one of the most important determinants of success in product innovation is an understanding of the market the product is introduced into. In this report consumer preferences for meat products, by animal species including minor meats, and by type of processing are examined. Responses to economic variables such as price, advertising and income are identified as are responses to food safety and meat related health issues. Interesting results include the fact that income elasticities of demand for meat products purchased at grocery stores are negative in this study and that own and cross price elasticities for certain meats, across processing levels for example, show strong substitutions. Thus introducing new meat products may not result in increased sales by animal species but may only result in substitution of one meat type product for another product of the same meat type. Successful new product introductions or changes in product quality are shown, in this report, to be accompanied by significant marketing/advertising investment and, either by design or by serendipity, to have credence attributes in line with consumer's changing concerns. An example of this is the response in branded chicken sales, at the time of BSE in Canada, for a brand that could advertise itself as being 100% grain fed. Marketing strategies, such as working with the Health Check™ program of the Heart and Stroke Foundation of Canada are shown to have an impact on firm level sales (as well as on sales at the individual product level), a halo effect, that may be of importance in the firm's development of other value-added products. Significant heterogeneity exists in consumer behaviour and it is important to recognize this heterogeneity in the development of value-added meat products. Added to the consumer heterogeneity, in general, is the heterogeneity in responses by meat type. What works for one sector, such as poultry, could be problematic in other sectors given differences in economic interrelationships reported in this study.meat, consumer behavior, value-added, strategic behaviour, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety, Livestock Production/Industries, Marketing, D12, Q18,
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ELAV links paused Pol II to alternative polyadenylation in the Drosophila nervious system
Alternative polyadenylation (APA) has been implicated in a variety of developmental and disease processes. A particularly dramatic form of APA occurs in the developing nervous system of flies and mammals, whereby various developmental genes undergo coordinate 3' UTR extension. In Drosophila, the RNA-binding protein ELAV inhibits RNA processing at proximal polyadenylation sites, thereby fostering the formation of exceptionally long 3' UTRs. Here, we present evidence that paused Pol II promotes recruitment of ELAV to extended genes. Replacing promoters of extended genes with heterologous promoters blocks normal 3' extension in the nervous system, while extension-associated promoters can induce 3' extension in ectopic tissues expressing ELAV. Computational analyses suggest that promoter regions of extended genes tend to contain paused Pol II and associated cis-regulatory elements such as GAGA. ChIP-seq assays identify ELAV in the promoter regions of extended genes. Our study provides evidence for a regulatory link between promoter-proximal pausing and APA
Comparison of Magnetic Flux Distribution between a Coronal Hole and a Quiet Region
Employing Big Bear Solar Observatory (BBSO) deep magnetograms and H
images in a quiet region and a coronal hole, observed on September 14 and 16,
2004, respectively, we have explored the magnetic flux emergence, disappearance
and distribution in the two regions. The following results are obtained: (1)
The evolution of magnetic flux in the quiet region is much faster than that in
the coronal hole, as the flux appeared in the form of ephemeral regions in the
quiet region is 4.3 times as large as that in the coronal hole, and the flux
disappeared in the form of flux cancellation, 2.9 times as fast as in the
coronal hole. (2) More magnetic elements with opposite polarities in the quiet
region are connected by arch filaments, estimating from magnetograms and
H images. (3) We measured the magnetic flux of about 1000 magnetic
elements in each observing region. The flux distribution of network and
intranetwork (IN) elements is similar in both polarities in the quiet region.
For network fields in the coronal hole, the number of negative elements is much
more than that of positive elements. However for the IN fields, the number of
positive elements is much more than that of negative elements. (4) In the
coronal hole, the fraction of negative flux change obviously with different
threshold flux density. 73% of the magnetic fields with flux density larger
than 2 Gauss is negative polarity, and 95% of the magnetic fields is negative,
if we only measure the fields with their flux density larger than 20 Gauss. Our
results display that in a coronal hole, stronger fields is occupied by one
predominant polarity; however the majority of weaker fields, occupied by the
other polarity
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