2,463 research outputs found
Polarization Observables for Two-Pion Production off the Nucleon
We develop polarization observables for the processes
and , using both a helicity and hybrid helicity-transversity
basis. Such observables are crucial if processes that produce final states
consisting of a spin-1/2 baryon and two pseudoscalar mesons are to be fully
exploited for baryon spectroscopy. We derive relationships among the
observables, as well as inequalities that they must satisfy. We also discuss
the observables that must be measured in `complete' experiments, and briefly
examine the prospects for measurement of some of these observables in the near
future.Comment: 20 pages, using revtex
Parameter Estimation and Quantitative Parametric Linkage Analysis with GENEHUNTER-QMOD
Objective: We present a parametric method for linkage analysis of quantitative phenotypes. The method provides a test for linkage as well as an estimate of different phenotype parameters. We have implemented our new method in the program GENEHUNTER-QMOD and evaluated its properties by performing simulations. Methods: The phenotype is modeled as a normally distributed variable, with a separate distribution for each genotype. Parameter estimates are obtained by maximizing the LOD score over the normal distribution parameters with a gradient-based optimization called PGRAD method. Results: The PGRAD method has lower power to detect linkage than the variance components analysis (VCA) in case of a normal distribution and small pedigrees. However, it outperforms the VCA and Haseman-Elston regression for extended pedigrees, nonrandomly ascertained data and non-normally distributed phenotypes. Here, the higher power even goes along with conservativeness, while the VCA has an inflated type I error. Parameter estimation tends to underestimate residual variances but performs better for expectation values of the phenotype distributions. Conclusion: With GENEHUNTER-QMOD, a powerful new tool is provided to explicitly model quantitative phenotypes in the context of linkage analysis. It is freely available at http://www.helmholtz-muenchen.de/genepi/downloads. Copyright (C) 2012 S. Karger AG, Base
Monitoring spatial sustainable development: Semi-automated analysis of satellite and aerial images for energy transition and sustainability indicators
Solar panels are installed by a large and growing number of households due to
the convenience of having cheap and renewable energy to power house appliances.
In contrast to other energy sources solar installations are distributed very
decentralized and spread over hundred-thousands of locations. On a global level
more than 25% of solar photovoltaic (PV) installations were decentralized. The
effect of the quick energy transition from a carbon based economy to a green
economy is though still very difficult to quantify. As a matter of fact the
quick adoption of solar panels by households is difficult to track, with local
registries that miss a large number of the newly built solar panels. This makes
the task of assessing the impact of renewable energies an impossible task.
Although models of the output of a region exist, they are often black box
estimations. This project's aim is twofold: First automate the process to
extract the location of solar panels from aerial or satellite images and
second, produce a map of solar panels along with statistics on the number of
solar panels. Further, this project takes place in a wider framework which
investigates how official statistics can benefit from new digital data sources.
At project completion, a method for detecting solar panels from aerial images
via machine learning will be developed and the methodology initially developed
for BE, DE and NL will be standardized for application to other EU countries.
In practice, machine learning techniques are used to identify solar panels in
satellite and aerial images for the province of Limburg (NL), Flanders (BE) and
North Rhine-Westphalia (DE).Comment: This document provides the reader with an overview of the various
datasets which will be used throughout the project. The collection of
satellite and aerial images as well as auxiliary information such as the
location of buildings and roofs which is required to train, test and validate
the machine learning algorithm that is being develope
Limit theorem for a time-dependent coined quantum walk on the line
We study time-dependent discrete-time quantum walks on the one-dimensional
lattice. We compute the limit distribution of a two-period quantum walk defined
by two orthogonal matrices. For the symmetric case, the distribution is
determined by one of two matrices. Moreover, limit theorems for two special
cases are presented
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A procedure for rapid determination of the silicon content in plant materials
An efficient, reliable and low-cost procedure to determine the silicon content in plant material is presented which allows to monitor the agricultural aspects like growth and yield. The presented procedure consists of a hydrochloric acid pre-treatment and a subsequent thermal oxidation. The method is compared to other processes like dissolution in hydrofluoric acid combined with ICP OES, energy-dispersive X-ray fluorescence spectroscopy (EDXRF) or aqua regia treatment
Strong-field effects in the Rabi oscillations of the superconducting phase qubit
Rabi oscillations have been observed in many superconducting devices, and
represent prototypical logic operations for quantum bits (qubits) in a quantum
computer. We use a three-level multiphoton analysis to understand the behavior
of the superconducting phase qubit (current-biased Josephson junction) at high
microwave drive power. Analytical and numerical results for the ac Stark shift,
single-photon Rabi frequency, and two-photon Rabi frequency are compared to
measurements made on a dc SQUID phase qubit with Nb/AlOx/Nb tunnel junctions.
Good agreement is found between theory and experiment.Comment: 4 pages, 4 figures, accepted for publication in IEEE Trans. Appl.
Supercon
Quantum logic gates for coupled superconducting phase qubits
Based on a quantum analysis of two capacitively coupled current-biased
Josephson junctions, we propose two fundamental two-qubit quantum logic gates.
Each of these gates, when supplemented by single-qubit operations, is
sufficient for universal quantum computation. Numerical solutions of the
time-dependent Schroedinger equation demonstrate that these operations can be
performed with good fidelity.Comment: 4 pages, 5 figures, revised for publicatio
Magnetic moment of hyperons in nuclear matter by using quark-meson coupling models
We calculate the magnetic moments of hyperons in dense nuclear matter by
using relativistic quark models. Hyperons are treated as MIT bags, and the
interactions are considered to be mediated by the exchange of scalar and vector
mesons which are approximated as mean fields. Model dependence is investigated
by using the quark-meson coupling model and the modified quark-meson coupling
model; in the former the bag constant is independent of density and in the
latter it depends on density. Both models give us the magnitudes of the
magnetic moments increasing with density for most octet baryons. But there is a
considerable model dependence in the values of the magnetic moments in dense
medium. The magnetic moments at the nuclear saturation density calculated by
the quark meson coupling model are only a few percents larger than those in
free space, but the magnetic moments from the modified quark meson coupling
model increase more than 10% for most hyperons. The correlations between the
bag radius of hyperons and the magnetic moments of hyperons in dense matter are
discussed.Comment: substantial changes in the text, submitted to PL
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