6,053 research outputs found
Calculating Kaon Fragmentation Functions from NJL-Jet Model
The Nambu--Jona-Lasinio (NJL) - Jet model provides a sound framework for
calculating the fragmentation functions in an effective chiral quark theory,
where the momentum and isospin sum rules are satisfied without the introduction
of ad hoc parameters. Earlier studies of the pion fragmentation functions using
the NJL model within this framework showed qualitative agreement with the
empirical parameterizations. Here we extend the NJL-Jet model by including the
strange quark. The corrections to the pion fragmentation functions and
corresponding kaon fragmentation functions are calculated using the elementary
quark to quark-meson fragmentation functions from NJL. The results for the kaon
fragmentation functions exhibit a qualitative agreement with the empirical
parameterizations, while the unfavored strange quark fragmentation to pions is
shown to be of the same order of magnitude as the unfavored light quark's. The
results of these studies are expected to provide important guidance for the
analysis of a large variety of semi-inclusive data.Comment: 9 pages, 14 figure
Asymptotic Level Density of the Elastic Net Self-Organizing Feature Map
Whileas the Kohonen Self Organizing Map shows an asymptotic level density
following a power law with a magnification exponent 2/3, it would be desired to
have an exponent 1 in order to provide optimal mapping in the sense of
information theory. In this paper, we study analytically and numerically the
magnification behaviour of the Elastic Net algorithm as a model for
self-organizing feature maps. In contrast to the Kohonen map the Elastic Net
shows no power law, but for onedimensional maps nevertheless the density
follows an universal magnification law, i.e. depends on the local stimulus
density only and is independent on position and decouples from the stimulus
density at other positions.Comment: 8 pages, 10 figures. Link to publisher under
http://link.springer.de/link/service/series/0558/bibs/2415/24150939.ht
Second Year Results from Razor C.O.A.C.H.
In this paper, we present the results of a random assignment evaluation on the Razor C.O.A.C.H. (Creating Opportunities for Arkansan’s Career Hopes) program. As the program started in the 2012-13 school year, this evaluation analyzes the impact of the program in its second year of operation and includes two cohorts of students. The focus of the comprehensive evaluation is the impacts of the program on students’ academic outcomes, short-term noncognitive outcomes, short-term college and career readiness outcomes, and post-secondary outcomes
Precise measurement of HFS of positronium
The ground state hyperfine splitting in positronium, , is sensitive to high order corrections of QED. A new
calculation up to has revealed a discrepancy
between the QED prediction and the experimental results. This discrepancy might
either be due to systematic problems in the previous experiments or to
contributions beyond the Standard Model. We propose an experiment to measure
employing new methods designed to remedy the systematic
errors which may have affected the previous experiments. Our experiment will
provide an independent check of the discrepancy. The measurement is in progress
and a preliminary result of has been obtained. A measurement with a
precision of O(1) ppm is expected within a few years.Comment: 5 pages, 6 figures, contributed to POSMOL 2009, will be published in
J. Phys.: Conf. Serie
Mutations of the ret protooncogene in German multiple endocrine neoplasia families: Relation between genotype and phenotype.
It has been suggested that not only the position but also the nature of the mutations of the ret protooncogene strongly correlate with the clinical manifestation of the multiple endocrine neoplasm type 2 (MEN 2) syndrome. In particular, individuals with a Cys634-Arg substitution should have a greater risk of developing parathyroid disease. We, therefore, analyzed 94 unrelated families from Germany with inherited medullary thyroid carcinoma (MTC) for mutation of the ret protooncogene. In all but 1 of 59 families with MEN 2A, germline mutations in the extracellular domain of the ret protein were found. Some 81% of the MEN 2A mutations affected codon 634. Phenotype-genotype correlations suggested that the prevalence of pheochromocytoma and hyperparathyroidism is significantly higher in families with codon 634 mutations, but there was no correlation with the nature of the mutation. In all but 1 of 27 familial MTC (FMTC) families, mutations were detected in 1 of 4 cysteines in the extracellular domain of the ret protooncogene. Half of the FMTC mutations affected codon 634. Mutations outside of codon 634 occurred more often in FMTC families than in MEN 2A families. In all but 1 of 8 MEN 2B patients, de novo mutations in codon 918 were found. These data confirm the preferential localization of MEN 2-associated mutations and the correlation between disease phenotype and the position of the ret mutation, but there was no correlation between the occurrence of hyperparathyroidism or pheochromocytoma and the nature of the mutation
Experimental and computational analyses reveal that environmental restrictions shape HIV-1 spread in 3D cultures
Here, using an integrative experimental and computational approach, Imle et al. show how cell motility and density affect HIV cell-associated transmission in a three-dimensional tissue-like culture system of CD4+ T cells and collagen, and how different collagen matrices restrict infection by cell-free virions
Preceding rule induction with instance reduction methods
A new prepruning technique for rule induction is presented which applies instance reduction before rule induction. An empirical evaluation records the predictive accuracy and size of rule-sets generated from 24 datasets from the UCI Machine Learning Repository. Three instance reduction algorithms (Edited Nearest Neighbour, AllKnn and DROP5) are compared. Each one is used to reduce the size of the training set, prior to inducing a set of rules using Clark and Boswell's modification of CN2. A hybrid instance reduction algorithm (comprised of AllKnn and DROP5) is also tested. For most of the datasets, pruning the training set using ENN, AllKnn or the hybrid significantly reduces the number of rules generated by CN2, without adversely affecting the predictive performance. The hybrid achieves the highest average predictive accuracy
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