2,393 research outputs found
A Note in the Skyrme Model with Higher Derivative Terms
Another stabilizer term is used in the classical Hamiltonian of the Skyrme
Model that permits in a much simple way the generalization of the higher-order
terms in the pion derivative field. Improved numerical results are obtained.Comment: Latex. Figure not include; available upon request. 7 pages, report
Diffractive Phenomena and Shadowing in Deep-Inelastic Scattering
Shadowing effects in deep-inelastic lepton-nucleus scattering probe the mass
spectrum of diffractive leptoproduction from individual nucleons. We explore
this relationship using current experimental information on both processes. In
recent data from the NMC and E665 collaboration, taken at small x << 0.1 and
Q^2 < 1 GeV^2, shadowing is dominated by the diffractive excitation and
coherent interaction of low mass vector mesons. If shadowing is explored at
small x > 1 GeV^2 as discussed at HERA, the situation is
different. Here dominant contributions come from the coherent interaction of
diffractively produced heavy mass states. Furthermore we observe that the
energy dependence of shadowing is directly related to the mass dependence of
the diffractive production cross section for free nucleon targets.Comment: 12 pages Latex, 8 figure
Identification of altered protein abundances in cholesteatoma matrix via mass spectrometry-based proteomic analysis
An Alternative to the MVU Estimator to Estimate the Level of DC in AWGN
In statistics, Maximum Likelihood Estimation (MLE) is a method of estimating the parameters of a particular statistical model, finding parameter values that maximize probability, observations, and the parameters are specified. The MLE can be seen as a special case of maximum post-positive estimation (MAP), which includes a uniform preventive distribution of parameters, or as a variant of the MAP that ignores the above and is therefore unregulated. Now let's look at an alternative to the MVU estimator, which is desirable in situations where the minimum variance unbiased (MVU) estimator does not exist or cannot be found, even if it exists. This estimator, which relies on the principle of maximum likelihood, is primarily the common method for obtaining a practical estimator. It has the clear advantage of being a crank turning procedure, which allows you to implement it for complicated estimation problems. A clear advantage of MLE is that it can be found numerically for a given data-set. The safest way to find the MLE is to search the grid, as long as the space between the searches are small enough, we are sure to find the MLE. Keywords: Maximum Likelihood Estimation, minimum variance unbiased, Estimator, Probability Distribution Function. DOI: 10.7176/ISDE/11-3-05 Publication date: June 30th 202
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Using formal methods to support testing
Formal methods and testing are two important approaches that assist in the development of high quality software. While traditionally these approaches have been seen as rivals, in recent
years a new consensus has developed in which they are seen as complementary. This article reviews the state of the art regarding ways in which the presence of a formal specification can be used to assist testing
Systematics of Leading Particle Production
Using a QCD inspired model developed by our group for particle production,
the Interacting Gluon Model (IGM), we have made a systematic analysis of all
available data on leading particle spectra. These data include diffractive
collisions and photoproduction at HERA. With a small number of parameters
(essentially only the non-perturbative gluon-gluon cross section and the
fraction of diffractive events) good agreement with data is found. We show that
the difference between pion and proton leading spectra is due to their
different gluon distributions. We predict a universality in the diffractive
leading particle spectra in the large momentum region, which turns out to be
independent of the incident energy and of the projectile type.Comment: 13 pages, Latex, 4 ps figures. To appear in Phys. Rev.
Exclusive diffractive processes and the quark substructure of mesons
Exclusive diffractive processes on the nucleon are investigated within a
model in which the quark-nucleon interaction is mediated by Pomeron exchange
and the quark substructure of mesons is described within a framework based on
the Dyson-Schwinger equations of QCD. The model quark-nucleon interaction has
four parameters which are completely determined by high-energy and elastic scattering data. The model is then used to predict vector-meson
electroproduction observables. The obtained - and -meson
electroproduction cross sections are in excellent agreement with experimental
data. The predicted dependence of -meson electroproduction also
agrees with experimental data. It is shown that confined-quark dynamics play a
central role in determining the behavior of the diffractive, vector-meson
electroproduction cross section. In particular, the onset of the asymptotic
behavior of the cross section is determined by a momentum scale that is
set by the current-quark masses of the quark and antiquark inside the vector
meson. This is the origin of the striking differences between the
dependence of -, - and -meson electroproduction cross
sections observed in recent experiments.Comment: 53 pages, 23 figures, revtex and epsfig. Minor additions to tex
Covalent Post-assembly Modification Triggers Multiple Structural Transformations of a Tetrazine-Edged Fe4L6 Tetrahedron
Covalent post-assembly modification (PAM) reactions are useful synthetic tools for functionalizing and stabilizing self-assembled metal-organic complexes. Recently, PAM reactions have also been explored as stimuli for triggering supramolecular structural transformations. Herein we demonstrate the use of inverse electron-demand Diels-Alder (IEDDA) PAM reactions to induce supramolecular structural transformations starting from a tetrazine-edged FeII4L6 tetrahedral precursor. Following PAM, this tetrahedron rearranged to form three different architectures depending on the addition of other stimuli: an electron-rich aniline or a templating anion. By tracing the stimulus-response relationships within the system, we deciphered a network of transformations that mapped different combinations of stimuli onto specific transformation products. Given the many functions being developed for self-assembled three-dimensional architectures, this newly established ability to control the interconversion between structures using combinations of different stimulus types may serve as the basis for switching the functions expressed within a system.D.A.R. acknowledges the Gates Cambridge Trust. B.S.P. acknowledges
the Royal Commission for the Exhibition of 1851 Fellowship and Corpus
Christi College, Cambridge. This work was supported by the UK
Engineering and Physical Sciences Research Council (EP/M01083X/1)
Observable jets from the BFKL chain
We derive a modified form of the BFKL equation which enables the structure of
the gluon emissions to be studied in small deep inelastic scattering. The
equation incorporates the resummation of the virtual and unresolved real gluon
emissions. We solve the equation to calculate the number of small
deep-inelastic events containing 0,1,2 ...resolved gluon jets, that is jets
with transverse momenta . We study the jet decomposition for
different choices of the jet resolution parameter .Comment: 14 pages, Latex, 13 ps figure
Moments of the Proton F2 Structure Function at Low Q2
The Q^2 dependence of inclusive electron-proton scattering F_2 structure
function data in both the nucleon resonance region and the deep inelastic
region, at momentum transfers below 5 (GeV/c)^2, is investigated. Moments of
F_2 are constructed, down to momentum transfers of Q^2 ~ 0.1 (GeV/c)^2. The
second moment is only slowly varying with Q^2 down to Q^2 ~ 1 (GeV/c)^2, which
is a reflection of duality. Below Q^2 of 1 (GeV/c)^2, the Q^2 dependence of the
moments is predominantly governed by the elastic contribution, whereas the
inelastic channels still seem governed by local duality.Comment: 11 page paper, 1 LaTeX file, 10 postscript figure file
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