962 research outputs found
Unitary Isobar Model - MAID2007
The unitary isobar model MAID2007 has been developed to analyze the world
data of pion photo- and electroproduction. The model contains both a common
background and several resonance terms. The background is unitarized according
to the K-matrix prescription, and the 13 four-star resonances with masses below
2 GeV are described by appropriately unitarized Breit-Wigner forms. The data
have been analyzed by both single-energy and global fits, and the transverse
and longitudinal helicity amplitudes have been extracted for the four-star
resonances below 2 GeV. Because of its inherent simplicity, MAID2007 is well
adopted for predictions and analysis of the observables in pion photo- and
electroproduction.Comment: 32 pages including 13 tables and 24 figure
Overview of nucleon structure studies
A brief overview of the recent activity in the measurement of the elastic
electromagnetic proton and neutron form factors is presented. It is discussed
how the quality of the data has been greatly improved by performing double
polarization experiments, and the role of two-photon exchange processes will be
highlighted. The spatial information on the quark charge distribibutions in the
nucleon resulting from the form factors measurements will be discussed, as well
as the steady rate of improvements made in the lattice QCD calculations. It is
discussed how generalized parton distributions have emerged as a unifying theme
in hadron physics linking the spatial densities extracted from form factors
with the quark momentum distribution information residing in quark structure
functions. The recent progress in the electromagnetic excitation of the
resonance will also briefly be discussed.Comment: prepared for Proceedings of International Nuclear Physics Conference
(INPC07), typos corrected + references adde
Baryon magnetic moments in the background field method
We present a calculation of the magnetic moments for the baryon octet and
decuplet using the background-field method and standard Wilson gauge and
fermion actions in the quenched approximation of lattice QCD. Progressively
smaller static magnetic fields are introduced on a lattice at beta=6.0
and the pion mass is probed down to about 500 MeV. Magnetic moments are
extracted from the linear response of the masses to the background field.Comment: 15 pages, 7 figures, 1 table, to appear in Phys. Lett.
Invariant Amplitudes for Pion Electroproduction
The invariant amplitudes for pion electroproduction on the nucleon are
evaluated by dispersion relations at constant t with MAID as input for the
imaginary parts of these amplitudes. In the threshold region these amplitudes
are confronted with the predictions of several low-energy theorems derived in
the soft-pion limit. In general agreement with Chiral Perturbation Theory, the
dispersive approach yields large corrections to these theorems because of the
finite pion mass.Comment: 18 pages, 8 figure
Study of nucleon resonances with electromagnetic interactions
Recent developments in using electromagnetic meson production reactions to
study the structure of nucleon resonances are reviewed. Possible future works
are discussed.Comment: 25 pages, 19 figure
A novel telomere biology disease-associated gastritis identified through a whole exome sequencing-driven approach
A whole exome sequencing (WES)-driven approach to uncover the etiology of unexplained inflammatory gastritides has been underutilized by surgical pathologists. Here, we discovered the pathobiology of an unusual chronic atrophic gastritis in two unrelated patients using this approach. The gastric biopsies were notable for an unusual pattern of gastritis with persistent dense inflammation, loss of both parietal and neuroendocrine cells in the oxyntic mucosa, and sparing of the antral mucosa. The patients were found to harbor pathogenic variants in telomeropathic genes (POT1 and DCLRE1B). Clonality testing for one of the patients showed evidence of evolving clonality of TCR-gene rearrangement. Both patients showed significantly decreased numbers of stem/progenitor cells by immunohistochemistry, which appears to be responsible for the development of mucosal atrophy. No such cases of unusual chronic atrophic gastritis in the setting of telomeropathy have been previously reported. The loss of stem/progenitor cells suggests that stem/progenitor cell exhaustion in the setting of telomere dysfunction is the likely mechanism for development of this unusual chronic atrophic gastritis. The results underscore the need for close monitoring of these gastric lesions, with special regard to their neoplastic potential. This combined WES-driven approach has promise to identify the cause and mechanism of other uncharacterized gastrointestinal inflammatory disorders
Nonequilibrium Dynamics in Low Dimensional Systems
In these lectures we give an overview of nonequilibrium stochastic systems.
In particular we discuss in detail two models, the asymmetric exclusion process
and a ballistic reaction model, that illustrate many general features of
nonequilibrium dynamics: for example coarsening dynamics and nonequilibrium
phase transitions. As a secondary theme we shall show how a common mathematical
structure, the q-deformed harmonic oscillator algebra, serves to furnish exact
results for both systems. Thus the lectures also serve as a gentle introduction
to things q-deformed.Comment: 48 pages LaTeX2e with 9 figures and using elsart.cls (included);
Lectures at the International Summer School on Fundamental Problems in
Statistical Physics X, August-September 2001, Altenberg, Germany. v2 corrects
some errors and includes further discussion/reference
Electroexcitation of nucleon resonances
We review recent progress in the investigation of the electroexcitation of
nucleon resonances, both in experiment and in theory. The most accurate results
have been obtained for the electroexcitation amplitudes of the four lowest
excited states, which have been measured in a range of Q2 up to 8 and 4.5 GeV2
for the Delta(1232)P33, N(1535)S11 and N(1440)P11, N(1520)D13}, respectively.
These results have been confronted with calculations based on lattice QCD,
large-Nc relations, perturbative QCD (pQCD), and QCD-inspired models. The
amplitudes for the Delta(1232) indicate large pion-cloud contributions at low
Q2 and don't show any sign of approaching the pQCD regime for Q2<7 GeV2.
Measured for the first time, the electroexcitation amplitudes of the Roper
resonance, N(1440)P11, provide strong evidence for this state as a
predominantly radial excitation of a three-quark (3q) ground state, with
additional non-3-quark contributions needed to describe the low Q2 behavior of
the amplitudes. The longitudinal transition amplitude for the N(1535)S11 was
determined and has become a challenge for quark models. Explanations may
require large meson-cloud contributions or alternative representations of this
state. The N(1520)D13 clearly shows the rapid changeover from helicity-3/2
dominance at the real photon point to helicity-1/2 dominance at Q2 > 0.5 GeV2,
confirming a long-standing prediction of the constituent quark model. The
interpretation of the moments of resonance transition form factors in terms of
transition transverse charge distributions in infinite momentum frame is
presented.Comment: 70 pages, 46 figures, will appear in Progress in Particle and Nuclear
Physics, v.67, p.1, 201
Copy number analysis of NIPBL in a cohort of 510 patients reveals rare copy number variants and a mosaic deletion
Funding Information No funding information provided. aThese authors contributed equally to this work
Pennsylvania Folklife Vol. 24, Folk Festival Supplement
• Folk Images of Rural Pennsylvania • Old Hymns in the Country Church • The Kutztown Folk Festival is for Children Too • A Forgotten Art Becoming Popular: Leathercraft • In the Country Kitchen: Pennsylvania Dutch Dishes are Created by Instinct • Visible but Unseen: The Festival Service Crews • Festival Highlights • Folk Festival Program • Three Times - And Sold! • Basketmaking at the Festival • The Christmas House • Music on the Main Stage • Metal Casting in Sand at the Festival • Windmills and Farm Water Supply: Folk-Cultural Questionnaire No. 40https://digitalcommons.ursinus.edu/pafolklifemag/1064/thumbnail.jp
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