1,455 research outputs found
Differential cross section analysis in kaon photoproduction using associated legendre polynomials
Angular distributions of differential cross sections from the latest CLAS
data sets \cite{bradford}, for the reaction have been analyzed using associated Legendre polynomials. This
analysis is based upon theoretical calculations in Ref. \cite{fasano} where all
sixteen observables in kaon photoproduction can be classified into four
Legendre classes. Each observable can be described by an expansion of
associated Legendre polynomial functions. One of the questions to be addressed
is how many associated Legendre polynomials are required to describe the data.
In this preliminary analysis, we used data models with different numbers of
associated Legendre polynomials. We then compared these models by calculating
posterior probabilities of the models. We found that the CLAS data set needs no
more than four associated Legendre polynomials to describe the differential
cross section data. In addition, we also show the extracted coefficients of the
best model.Comment: Talk given at APFB08, Depok, Indonesia, August, 19-23, 200
Strong-coupling analysis of scanning tunneling spectra in BiSrCaCuO
We study a series of spectra measured in the superconducting state of
optimally-doped Bi-2223 by scanning tunneling spectroscopy. Each spectrum, as
well as the average of spectra presenting the same gap, is fitted using a
strong-coupling model taking into account the band structure, the BCS gap, and
the interaction of electrons with the spin resonance. After describing our
measurements and the main characteristics of the strong-coupling model, we
report the whole set of parameters determined from the fits, and we discuss
trends as a function of the gap magnitude. We also simulate angle-resolved
photoemission spectra, and compare with recent experimental results.Comment: Published versio
The WINGS Survey: a progress report
A two-band (B and V) wide-field imaging survey of a complete, all-sky X-ray
selected sample of 78 clusters in the redshift range z=0.04-0.07 is presented.
The aim of this survey is to provide the astronomical community with a complete
set of homogeneous, CCD-based surface photometry and morphological data of
nearby cluster galaxies located within 1.5 Mpc from the cluster center. The
data collection has been completed in seven observing runs at the INT and
ESO-2.2m telescopes. For each cluster, photometric data of about 2500 galaxies
(down to V~23) and detailed morphological information of about 600 galaxies
(down to V~21) are obtained by using specially designed automatic tools.
As a natural follow up of the photometric survey, we also illustrate a long
term spectroscopic program we are carrying out with the WHT-WYFFOS and AAT-2dF
multifiber spectrographs. Star formation rates and histories, as well as
metallicity estimates will be derived for about 350 galaxies per cluster from
the line indices and equivalent widths measurements, allowing us to explore the
link between the spectral properties and the morphological evolution in high-
to low-density environments, and across a wide range in cluster X-ray
luminosities and optical properties.Comment: 12 pages, 10 eps figures, Proceedings of the SAIt Conference 200
Role of the IL-23/IL-17 Pathway in Rheumatic Diseases: An Overview
Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, IL-23A (p19) and IL-12/23B (p40), the latter shared with Interleukin-12 (IL-12). IL-23 is mainly produced by macrophages and dendritic cells, in response to exogenous or endogenous signals, and drives the differentiation and activation of T helper 17 (Th17) cells with subsequent production of IL-17A, IL-17F, IL-6, IL-22, and tumor necrosis factor \u3b1 (TNF-\u3b1). Although IL-23 plays a pivotal role in the protective immune response to bacterial and fungal infections, its dysregulation has been shown to exacerbate chronic immune-mediated inflammation. Well-established experimental data support the concept that IL-23/IL-17 axis activation contributes to the development of several inflammatory diseases, such as PsA, Psoriasis, Psoriatic Arthritis; AS, Ankylosing Spondylitis; IBD, Inflammatory Bowel Disease; RA, Rheumatoid Arthritis; SS, Sjogren Syndrome; MS, Multiple Sclerosis. As a result, emerging clinical studies have focused on the blockade of this pathogenic axis as a promising therapeutic target in several autoimmune disorders; nevertheless, a greater understanding of its contribution still requires further investigation. This review aims to elucidate the most recent studies and literature data on the pathogenetic role of IL-23 and Th17 cells in inflammatory rheumatic diseases
Imaging the essential role of spin-fluctuations in high-Tc superconductivity
We have used scanning tunneling spectroscopy to investigate short-length
electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+d) (Bi-2223). We show
that the superconducting gap and the energy Omega_dip, defined as the
difference between the dip minimum and the gap, are both modulated in space
following the lattice superstructure, and are locally anti-correlated. Based on
fits of our data to a microscopic strong-coupling model we show that Omega_dip
is an accurate measure of the collective mode energy in Bi-2223. We conclude
that the collective mode responsible for the dip is a local excitation with a
doping dependent energy, and is most likely the (pi,pi) spin resonance.Comment: 4 pages, 4 figure
Multipole analysis of spin observables in vector meson photoproduction
A multipole analysis of vector meson photoproduction is formulated as a
generalization of the pseudoscalar meson case. Expansion of spin observables in
the multipole basis and behavior of these observables near threshold and
resonances are examined.Comment: 15 pages, latex, 2 figure
Dynamic centrifuge testing to assess liquefaction potential
A set of centrifuge tests has been carried out at ISMGEO (Italy) laboratory on models of a liquefiable soil. A natural sand from the Emilia-Romagna region in Italy was used in the tests, in order to reproduce typical ground conditions where liquefaction occurred during the seismic sequence of 2012. The models were instrumented with miniaturised accelerometers and with pore pressure and displacement transducers. Spectrum-compatible acceleration time histories were applied at the base of the model. In this way triggering of the liquefaction was detected and post-liquefaction settlements were evaluated. The paper describes with the tests carried out on free-field models. Further tests are currently ongoing to assess the seismic response of simple model structures lying on liquefiable ground. The testing programme, funded within the H2020 research project LIQUEFACT, is aimed at an experimental verification of ground improvement techniques used to mitigate the liquefaction susceptibility of fully saturated loose sands
Superclustering at Redshift Z=0.54
We present strong evidence for the existence of a supercluster at a redshift
of z=0.54 in the direction of Selected Area 68. From the distribution of
galaxies with spectroscopic redshifts we find that there is a large
over-density of galaxies (a factor of four over the number expected in an
unclustered universe) within the redshift range 0.530 < z < 0.555. By
considering the spatial distribution of galaxies within this redshift range
(using spectroscopic and photometric redshifts) we show that the galaxies in
SA68 form a linear structure passing from the South-West of the survey field
through to the North-East (with a position angle of approximately 35 deg East
of North). This position angle is coincident with the positions of the X-ray
clusters CL0016+16, RX J0018.3+1618 and a new X-ray cluster, RX J0018.8+1602,
centered near the radio source 54W084. All three of these sources are at a
redshift of approximately z=0.54 and have position angles, derived from their
X-ray photon distributions, consistent with that measured for the supercluster.
Assuming a redshift of 0.54 for the distribution of galaxies and a FWHM
dispersion in redshift of 0.020 this represents a coherent structure with a
radial extent of 31 Mpc, transverse dimension of 12 Mpc, and a thickness of
approximately 4 Mpc. The detection of this possible supercluster demonstrates
the power of using X-ray observations, combined with multicolor observations,
to map the large scale distribution of galaxies at intermediate redshifts.Comment: 12 pages, 3 figures, Latex, aaspp4.sty, accepted for publication in
Ap J Letters. Figure 3 and followup observations can be found at
http://tarkus.pha.jhu.edu/~ajc/papers/supercluster
Molecular Gas in Elliptical Galaxies: Distribution and Kinematics
I present interferometric images (approx. 7" resolution) of CO emission in
five elliptical galaxies and nondetections in two others. These data double the
number of elliptical galaxies whose CO emission has been fully mapped. The
sample galaxies have 10^8 to 5x10^9 solar masses of molecular gas distributed
in mostly symmetric rotating disks with diameters of 2 to 12 kpc. Four out of
the five molecular disks show remarkable alignment with the optical major axes
of their host galaxies. The molecular masses are a few percent of the total
dynamical masses which are implied if the gas is on circular orbits. If the
molecular gas forms stars, it will make rotationally supported stellar disks
which will be very similar in character to the stellar disks now known to be
present in many ellipticals. Comparison of stellar kinematics to gas kinematics
in NGC 4476 implies that the molecular gas did not come from internal stellar
mass loss because the specific angular momentum of the gas is about three times
larger than that of the stars.Comment: 47 pages, 6 tables, 27 figures. Accepted by AJ, scheduled for August
200
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