Regulatory networks play a central role in the modulation of gene expression, the control of cellular differentiation, and the emergence of complex phenotypes. Regulatory networks could constrain or ...facilitate evolutionary adaptation in gene expression levels. Here, we model the adaptation of regulatory networks and gene expression levels to a shift in the environment that alters the optimal expression level of a single gene. Our analyses show signatures of natural selection on regulatory networks that both constrain and facilitate rapid evolution of gene expression level towards new optima. The analyses are interpreted from the standpoint of neutral expectations and illustrate the challenge to making inferences about network adaptation. Furthermore, we examine the consequence of variable stabilizing selection across genes on the strength and direction of interactions in regulatory networks and in their subsequent adaptation. We observe that directional selection on a highly constrained gene previously under strong stabilizing selection was more efficient when the gene was embedded within a network of partners under relaxed stabilizing selection pressure. The observation leads to the expectation that evolutionarily resilient regulatory networks will contain optimal ratios of genes whose expression is under weak and strong stabilizing selection. Altogether, our results suggest that the variable strengths of stabilizing selection across genes within regulatory networks might itself contribute to the long‐term adaptation of complex phenotypes.
We present a new measurement of $J/\psi$ production in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental ...conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that the ($J/\psi$)/Drell-Yan cross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that the ($J/\psi$)/Drell-Yan cross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions.
Particle identification with COMPASS RICH-1 Abbon, P.; Alexeev, M.; Angerer, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2011, Letnik:
631, Številka:
1
Journal Article
Recenzirano
RICH-1 is a large size RICH detector in operation at the COMPASS experiment since 2001 and recently upgraded implementing a new photon detection system with increased performance.
A dedicated ...software package has been developed to perform RICH-1 data reduction, pattern recognition and particle identification as well as a number of accessory tasks for detector studies.
The software package, the algorithms implemented and the detector characterisation and performance are reported in detail.
We report a new measurement of J/ψ, ψ′ and Drell–Yan cross-sections, in the kinematical domain -0.425<ycm<0.575 and -0.5<cosθCS<0.5, performed at the CERN-SPS using 400 GeV/c incident protons on Be, ...Al, Cu, Ag, W and Pb targets. The dependence of the charmonia production cross-sections on the size of the target nucleus allows to quantify the so-called normal nuclear absorption. In the framework of the Glauber model, this new measurement is combined with results previously obtained with the same apparatus, under different experimental conditions, and leads to a precise determination of the J/ψ and ψ′ absorption cross-sections in the surrounding nuclear matter.
ψ′ production is studied in Pb–Pb collisions at 158 GeV/c per nucleon incident momentum. Absolute cross-sections are measured and production rates are investigated as a function of the centrality of ...the collision. The results are compared with those obtained for lighter colliding systems and also for the J/ψ meson produced under identical conditions.
The experience of building and operating COMPASS RICH-1 Abbon, P.; Alexeev, M.; Angerer, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2011, Letnik:
639, Številka:
1
Journal Article
Recenzirano
COMPASS RICH-1 is a large size gaseous Imaging Cherenkov Detector providing hadron identification in the range from 3 to 55
GeV/
c, in the wide acceptance spectrometer of the COMPASS Experiment at ...CERN SPS.
It uses a 3
m long C
4F
10 radiator, a 21
m
2 large VUV mirror surface and two kinds of photon detectors: MAPMTs and MWPCs with CsI photocathodes, covering a total of 5.5
m
2. It is in operation since 2002 and its performance has increased in time thanks to progressive optimization and mostly to a major upgrade which was implemented in 2006.
The main characteristics of COMPASS RICH-1 components are described and some specific aspects related to the radiator gas system, the mirror alignment, the MWPC electrical stability and the readout electronics are discussed.
Some key features of the event reconstruction and the PID analysis are presented together with results from the COMPASS RICH-1 performance characterization study.
Flow coefficients vn of the orders n = 1 – 6 are measured with the High-Acceptance Spectrometer (HADES) at GSI for protons, deuterons, and tritons as a function of centrality, transverse momentum, ...and rapidity in Au + Au collisions at √sNN = 2.4 GeV. Combining the information from the flow coefficients of all orders allows us to construct for the first time, at collision energies of a few GeV, a multidifferential picture of the angular emission pattern of these particles. It reflects the complicated interplay between the effect of the central fireball pressure on the emission of particles and their subsequent interaction with spectator matter. The high precision information on higher order flow coefficients is a major step forward in constraining the equation of state of dense baryonic matter.
Particle identification with the fast COMPASS RICH-1 detector Abbon, P.; Alexeev, M.; Angerer, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2010, Letnik:
623, Številka:
1
Journal Article
Recenzirano
A new photon detection system for the COMPASS RICH-1 detector has been designed and installed. In the central region, the project is based on multi-anode photo-multiplier technology accompanied by ...charge sensitive, high resolution and dead-time free time digitization. In the outer area, only the readout electronics for the existing photon detectors has been replaced. Details on the detector upgrade and its performance are presented.