201 research outputs found
Rapidity gaps at HERA and the Tevatron from soft colour exchanges
Models based on soft colour exchanges to rearrange colour strings in the
final state provide a general framework for both diffractive and
non-diffractive events in ep and hadron-hadron collisions. We study two such
models and find that they can reproduce rapidity gap data from both HERA and
the Tevatron. We also discuss the influence of parton cascades and multiple
interactions on the results.Comment: 4 pages, 4 EPS figures, presented at UK Phenomenology Workshop on
Collider Physics, Durham. Uses iopart.cl
Outstanding problems in the phenomenology of hard diffractive scattering
This paper is a summary of the discussion within the Diffractive and Low-x
Physics Working Group at the 1999 Durham Collider Workshop of the
interpretation of the Tevatron and HERA measurements of inclusive hard
diffraction.Comment: 5 pages, 1 figure. Talks and discussions from the UK Phenomenology
Workshop on Collider Physics, Durham, September 199
Nuclear effects in at small in deep inelastic scattering on Li and He
We suggest to use polarized nuclear targets of Li and He to study
nuclear effects in the spin dependent structure functions .
These effects are expected to be enhanced by a factor of two as compared to the
unpolarized targets.
We predict a significant dependence at of due to nuclear shadowing and nuclear
enhancement. The effect of nuclear shadowing at is of an
order of 16% for and 10% for
. By imposing the requirement that
the Bjorken sum rule is satisfied we model the effect of enhancement.
We find the effect of enhancement at to be of an
order of for and
for , if enhancement
occupies the region (). We predict
a 2% effect in the difference of the scattering cross sections of deep
inelastic scattering of an unpolarized projectile off Li with =3/2
and =1/2. We also show explicitly that the many-nucleon description of
deep inelastic scattering off Li becomes invalid in the enhancement region
.Comment: 29 pages, 5 figures, RevTe
Concurrent and Construct Validity of Methods to Estimate Fat-Free Mass in Children, Adolescents, and Young Adults
INTRODUCTION: Indirect methodologies are available to estimate fat-free mass (FFM) as a skeletal muscle mass surrogate in field settings at low cost. However, there is a lack of knowledge related with the FMM estimations variability introduced by the available methods and its correlations with performance constructs. The association between repeated measures of FFM by different methodologies and strength tests must provide a valuable construct validity analysis, which allows us to select the best method to assess the functional body composition.
PURPOSE: To analyze validity and agreement between laboratory and field methods to estimate FFM in children, adolescents, and young adults, and their relationships with strength.
METHODS: We studied a dataset of participants aged 6-21y (531 assessments, 287 boys). FFM was evaluated by isotope dilution method (REF), dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA) and anthropometry (ANT). Isometric strength was assessed by limb dynamometry and dynamic strength as sprinting and jumping. Concurrent validity was analyzed by differences between methods and concordance correlation coefficient (CCC), agreement by Bland-Altman analysis, and construct validity by individual associations.
RESULTS: FFM from ANT had the lowest bias in girls (-2.33±4.41kg, P≤0.0001) and from BIA in boys (-1.79±4.51kg, P≤0.0001). The best CCC was found for FFM-BIA (girls, 0.764; boys, 0.926). The highest correlation with constructs was found for handgrip and FFM-BIA in girls (r=-0.743) and FFM-REF in boys (r=0.812; both P≤0.001).
CONCLUSION: Our results showed BIA was the best method to estimate FFM. Nonetheless, there was not a single method which correlated the best with all strength constructs. The low coordinative requirement of isometric strength test could be one of the reasons to find a better correlation with FFM than explosive dynamic tests, and this leads us to speculate that isometric strength is more dependent of body composition than dynamic tests. These findings needed to be refuted with additional constructs
Probing small-x parton densities in proton- proton (-nucleus) collisions in the very forward direction
We present calculations of several pp scattering cross sections with
potential applications at the LHC. Significantly large rates for momentum
fraction, x, as low as 10^-7 are obtained, allowing for possible extraction of
quark and gluon densities in the proton and nuclei down to these small x values
provided a detector with good acceptance at maximal rapidities is used.Comment: 14 pages, LaTeX, 12 figures, uses revtex.st
A new gamma*-p / pbar-p factorization test in diffraction, valid below Q^2 about 6 GeV^2
One of the key experimental issues in high energy hadron physics is the
extent to which data from the diffractive interaction mechanism may be
described by a factorized formula which is the product of a universal term
describing the probability of finding a Pomeron in a proton (loosely referred
to as the "Pomeron flux-factor") and a term decribing the Pomeron's interaction
with the other incident proton. In the present paper, after demonstrating that
existing data on diffractive gamma*-p and pbar-p interactions show that the
Pomeron flux-factor is not universal, we present the results of a new test of
factorization in these interactions which does not rely on universality of the
flux-factor. The test is satisfied to within ~20% for 1 < Q^2 ~ 6 GeV^2 and
beta < 0.2 in the gamma*-p interactions, suggesting that the resons for
non-universality of the flux-factor have a limited effect on the factorization
itself. However, a clear breakdown of this test is observed at larger Q^2.
Kharzeev and Levin suggest that this can be attributed to the onset of QCD
evolution effects in the Pomeron's structure. The breakdown occurs in a Q^2
region which agrees with their estimates of a small Pomeron size.Comment: 20 pages, 7 Encapsulated Postscript figures, LaTex, submitted to
European Phisical Journal
Differentially expressed genes in platinum-resistant high-grade serous ovarian cancer
Objectives: The purpose of this study was to identify genes and pathways differentially expressed in platinum resistant high grade serous ovarian cancer (HGSOC) when compared to sensitive HGSOC.
Methods: A total of 37 patients with HGSOC tissue samples underwent RNA sequencing performed by TEMPUS (N=37, 21 platinum sensitive, 16 resistant; 85% Stage III-IV; 58% received neoadjuvant chemotherapy). RNA gene expression data and significantly impacted pathways were analyzed using Advaita Bio\u27s iPathwayGuide. Differentially expressed (DE) genes were identified using FDR of 0.05 and fold-change of 1.5. Genes from several impacted canonical metabolic pathways were validated by PCR against external data sets in a separate ovarian cancer sample group (n=15), platinum resistant ovarian cancer mouse tumor model, and wild-type sensitive and platinum resistant ovarian cancer cell lines. Relative gene expression was calculated using the comparative Ct method, also referred to as the “2 DDCT”, using L27 as internal control gene.
Results: We identified 177 differentially expressed (DE) genes out of a total of 16,607 genes (1.1%) with measured expression. 15 pathways were found to be significantly impacted. Of the 15 canonical pathways, all were up regulated in the resistant HGSOC and the majority of the most significantly altered (5/10) were related to metabolism (Retinol metabolism (p-value = 0.002); Tyrosine Metabolism (p-value = 0.005); Tryptophan Metabolism (p-value = 0.009); and Phenylalanine Metabolism (p-value = 0.012); CYP Drug Metabolism (p-value = 0.022)). A total of 3 separate genes from the CYP family and two from the Dopa Decarboxylase family of genes were validated against an external data set of human ovarian tissue samples, cell lines, mouse ovarian tumor model, and found to have similarly increased gene expression in the genes tested in the platinum resistant groups. Compilation of KEGG analysis and the common network genes revealed pathways associated with amino acid metabolism to be most significantly altered.
Conclusions: We describe the identification of a unique transcriptomic profile associated with platinum resistance. Interestingly, the main pathways identified are related to metabolism, suggesting that the survival to chemotherapy demands a major metabolic adaptation. These findings also represent a first step towards the identification of biomarkers for the detection of chemo-resistant disease and metabolism-based drug targets specific for chemo-resistant tumors. Further validation of this model is required in order to determine its clinical value
Fading out of J/psi color transparency in high energy heavy ion peripheral collisions
We provide predictions for the J/psi coherent production in the peripheral
heavy ion collisions at LHC and at RHIC using the leading twist model of
nuclear shadowing based on the QCD factorization theorem for diffraction and
the HERA hard diffraction data. We demonstrate that for the LHC kinematics this
model leads to a bump-shape distribution in rapidity which is suppressed
overall as compared to the expectations of the color transparency regime by a
factor 6. This is significantly larger suppression than that expected within
the impact parameter eikonal model. Thus we show that the interaction of
spatially small wave package for which the total cross section of interaction
with nucleons is small is still strongly shadowed by nuclear medium in high
energy processes.Comment: 13 pages, 7 figure
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