42 research outputs found
Total Hadronic Cross Section and the Elastic Slope: An Almost Model-Independent Connection
An almost model-independent parametrization for the ratio of the total cross
section to the elastic slope, as function of the center of mass energy, is
introduced. The analytical result is based on the approximate relation of this
quantity with the ratio of the elastic to total cross section and empirical
fits to the data from proton-proton scattering above 10 GeV, under the
conditions of asymptotic unitarity and the black-disk limit. This
parametrization may be useful in studies of extensive air showers and the
determination of the proton-proton total cross section from proton-air
production cross section in cosmic-ray experiments.Comment: 15 pages, 4 figures, v4: few typos corrected, final version to be
published in Nucl. Phys.
Non-linear regression models for Approximate Bayesian Computation
Approximate Bayesian inference on the basis of summary statistics is
well-suited to complex problems for which the likelihood is either
mathematically or computationally intractable. However the methods that use
rejection suffer from the curse of dimensionality when the number of summary
statistics is increased. Here we propose a machine-learning approach to the
estimation of the posterior density by introducing two innovations. The new
method fits a nonlinear conditional heteroscedastic regression of the parameter
on the summary statistics, and then adaptively improves estimation using
importance sampling. The new algorithm is compared to the state-of-the-art
approximate Bayesian methods, and achieves considerable reduction of the
computational burden in two examples of inference in statistical genetics and
in a queueing model.Comment: 4 figures; version 3 minor changes; to appear in Statistics and
Computin
Reduced SLIT2 is associated with increased cell proliferation and arsenic trioxide resistance in acute promyelocytic Leukemia
The SLIT-ROBO axis plays an important role in normal stem-cell biology, with possible
repercussions on cancer stem cell emergence. Although the Promyelocytic Leukemia (PML) protein
can regulate SLIT2 expression in the central nervous system, little is known about SLIT2 in acute
promyelocytic leukemia. Hence, we aimed to investigate the levels of SLIT2 in acute promyelocytic
leukemia (APL) and assess its biological activity in vitro and in vivo. Our analysis indicated that
blasts with SLIT2high transcript levels were associated with cell cycle arrest, while SLIT2low APL
blasts displayed a more stem-cell like phenotype. In a retrospective analysis using a cohort of
patients treated with all-trans retinoic acid (ATRA) and anthracyclines, high SLIT2 expression was
correlated with reduced leukocyte count (p = 0.024), and independently associated with improved
overall survival (hazard ratio: 0.94; 95% confidence interval: 0.92–0.97; p < 0.001). Functionally,
SLIT2-knockdown in primary APL blasts and cell lines led to increased cell proliferation and resistance
to arsenic trioxide induced apoptosis. Finally, in vivo transplant of Slit2-silenced primary APL blasts
promoted increased leukocyte count (p = 0.001) and decreased overall survival (p = 0.002) compared
with the control. In summary, our data highlight the tumor suppressive function of SLIT2 in APL and
its deteriorating effects on disease progression when downregulated
Transpiration and leaf growth of potato clones in response to soil water deficit
Potato (Solanum tuberosum ssp. Tuberosum) crop is particularly susceptible to water deficit because of its small and shallow root system. The fraction of transpirable soil water (FTSW) approach has been widely used in the evaluation of plant responses to water deficit in different crops. The FTSW 34 threshold (when stomatal closure starts) is a trait of particular interest because it is an indicator of tolerance to water deficit. The FTSW threshold for decline in transpiration and leaf growth was evaluated in a drying soil to identify potato clones tolerant to water deficit. Two greenhouse experiments were carried out in pots, with three advanced clones and the cultivar Asterix. The FTSW, transpiration and leaf growth were measured on a daily basis, during the period of soil drying. FTSW was an efficient method to separate potato clones with regard to their response to water deficit. The advancedclones SMINIA 02106-11 and SMINIA 00017-6 are more tolerant to soil water deficit than the cultivar Asterix, and the clone SMINIA 793101-3 is more tolerant only under high solar radiation