Differential elliptic flow spectra v2(pT) of π−, KS0, p, Λ have been measured at sNN=17.3 GeV around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb+Au collisions (10% of σgeo). The ...pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow is derived as a constituent, besides π+ and K+, of the elliptic flow of positive pion candidates. This retrieval requires additional inputs: (i) of the particle composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios obtained by NA49 are adapted to CERES conditions; for (ii), the measured v2(pT) of negative pions is substituted, assuming π+ and π− elliptic flow magnitudes to be sufficiently close. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π−–KS0–p–Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (Tf=160 MeV) leaving not much time for hadronic evolution. The proton v2(pT) data show a downward swing towards low pT with excursions into negative v2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous hydrodynamics studies which focus on late hadronic stages.
Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that ...freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.
The CERES/NA45 radial drift Time Projection Chamber Adamová, D.; Agakichiev, G.; Antończyk, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2008, Letnik:
593, Številka:
3
Journal Article
Recenzirano
The design, calibration, and performance of the first radial drift Time Projection Chamber (TPC) are presented. The TPC was built and installed at the CERES/NA45 experiment at the CERN SPS in the ...late nineties, with the objective to improve the momentum resolution of the spectrometer. The upgraded experiment took data twice, in 1999 and in 2000. After a detailed study of residual distortions a spatial resolution of
340
μ
m
in the azimuthal and
640
μ
m
in the radial direction was achieved, corresponding to a momentum resolution of
Δ
p
/
p
=
(
1
%
·
p
/
GeV
)
2
+
(
2
%
)
2
.
We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of 40 AGeV. The observed pair yield integrated over the range of invariant masses ...0.2<m</=1 GeV/c(2) is enhanced over the expectation from neutral meson decays by a factor of 5.9+/-1.5(stat)+/-1.2(syst data)+/-1.8(syst meson decays), somewhat larger than previously observed at the higher energy of 158 AGeV. The results are discussed with reference to model calculations based on pi(+)pi(-)-->e(+)e(-) annihilation with a modified rho propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the rho are more driven by baryon density than by temperature.
Results are presented of a two-pion interferometry (HBT) analysis in Pb+Au collisions at 40, 80, and 158
A
GeV. A detailed study of the Bertsch–Pratt HBT radius parameters has been performed as ...function of the mean pair transverse momentum
k
t
and in bins of the centrality of the collision. From these results we extract model-dependent information about the space–time evolution of the reaction. An investigation of the effective volume of the pion emitting system provides an important tool to study the properties of thermal pion freeze-out.
It has been shown that GH excess is associated with decreased leptin levels and decreased body fat mass. Reports regarding the effect of GH on serum leptin levels are inconsistent. We studied leptin ...secretion in 20 acromegalics before and 2 months after trans-sphenoidal surgery and in 20 gender-, age-, and body mass index (BMI)-matched control subjects. The mean 8-h leptin concentration for each subject was measured from a pool formed of samples collected hourly beginning at 2200 h until 0600 h the next morning. In a subgroup of 10 acromegalics, leptin pulsatility was assessed for the same period of time in 10-min sampling intervals. Basal GH, insulin-like growth factor-I (IGF-I), insulin, glucose, and lipids levels were measured. Area under the curve for insulin (AUCins) during oral glucose tolerance test was calculated. Control subjects and acromegalics had similar BMI, but patients with active acromegaly had significantly lower mean leptin level (mean +/- SEM; in men, 2.6+/-0.4 vs. 7.1+/-1.1 microg/L, P = 0.003; in women, 16.0+/-3.4 vs. 23.5+/-3.1 microg/L; P = 0.036). Mean 8-h leptin correlated with BMI (r = 0.57, P = 0.007, in controls; r = 0.70, P = 0.001, in patients). In stepwise regression analysis with mean 8-h leptin as a dependent variable, BMI (P<0.001) and gender (P = 0.01) in acromegalics entered the equation, whereas in control subjects gender, free fatty acids, insulin, and age accounted for 99.3% in leptin variability. After surgery, BMI did not change significantly; and glucose (P = 0.014), GH (P<0.001), and IGF-I (P<0.001) levels together with AUCins (P = 0.002) decreased, whereas mean leptin concentration rose significantly and attained normal levels (4.1+/-0.8 microg/L, P = 0.028) in acromegalic men and (23.6+/-4.7 microg/L, P = 0.003) in acromegalic women. Correlation between leptin level and BMI was preserved after surgery (r = 0.62, P = 0.005). In stepwise regression analysis, free fatty acids (P = 0.04) contributed to 26.8% of the variance in corrected-leptin (for BMI and gender). Leptin concentration peak height and interpeak nadir level rose significantly (P = 0.033 and P = 0.037) after surgery by Cluster analysis, without significant changes in leptin pulse frequency and incremental peak amplitude. Nocturnal rise of leptin (mathematically described by a cubic curve) was characterized by an acrophase just after midnight, before and after surgery. The amplitude and the average leptin concentration of the cubic fit increased significantly after surgery (P = 0.028 and P< 0.001). In conclusion in acromegalic patients: 1) leptin secretion maintains the pulsatility and nocturnal rise; 2) the gender-based leptin differences are preserved; 3) GH-IGF-I normalization leads to a rise in leptin that is not related to changes in BMI; and 4) the possible role of rise in leptin levels when assessing clinical and metabolic outcome of therapy in acromegalic patients deserves additional studies.
Results of a two-particle correlation analysis of high-pt charged particles in Pb–Au collisions at 158A GeV/c are presented. The data have been recorded by the CERES experiment at the CERN-SPS. The ...correlations are studied as function of transverse momentum, particle charge and collision centrality. We observe a jet-like structure in the vicinity of a high-pt trigger particle and a broad back-to-back distribution. The yields of associated particles per trigger show a strong dependence on the trigger/associate charge combination. A comparison to PYTHIA confirms the jet-like pattern at the near-side but suggests a strong modification at the away-side, implying significant energy transfer of the hard-scattered parton to the medium.
Molecular mechanisms underlying pathophysiology of polycystic ovary syndrome (PCOS), especially those related to cortisol signaling, are poorly understood. We hypothesized that modulation of ...glucocorticoid receptor (GR) expression and function, may underlie possible PCOS-related impairment of feedback inhibition of hypothalamic-pituitary-adrenocortical (HPA) axis activity and thus contribute to increased adrenal androgen production in women with PCOS.
24 normal-weight and 31 obese women with PCOS were compared to 25 normal-weight controls. Fasting blood samples were collected for measurements of serum concentrations of dehydroepiandrosterone sulfate, testosterone, sex hormone-binding globulin, insulin, basal cortisol and cortisol after oral administration of 0.5 mg dexamethasone. Concentrations of GR mRNA, GR protein, mineralocorticoid receptor (MR) protein and heat shock proteins (Hsps), as well as the number of GR per cell (B(max)) and its equilibrium dissociation constant (K(D)) were measured in isolated peripheral blood mononuclear cells.
An increase in HPA axis sensitivity to dexamethasone, an elevation of the GR protein concentration, and unaltered receptor functional status were found in both normal-weight and obese women with PCOS vs. healthy controls. Lymphocyte MR, Hsp90 and Hsp70 concentrations, and MR/GR ratio were similar in all groups. Correlation between B(max) and K(D) was weaker in the group of obese women with PCOS than in the other 2 groups.
The results did not confirm the initial hypothesis, but imply that PCOS is associated with increased GR protein concentration and HPA axis sensitivity to dexamethasone.
Infant formulas are highly sensitive to the Maillard reaction during manufacturing, while this reaction induces significant loss in protein nutritional value and safety. The indicators mostly used to ...monitor the reaction during heat treatment are furosine, carboxymethyllysine and hydroxymethylfurfural, but analysis of these molecules is time-consuming and expensive. The FAST method, based on simple fluorescence measurements on clear milk supernatant, is a good alternative for Maillard reaction monitoring in milk products.
The aim of this study was to determine the respective sensitivity of the various indicators of heat damage to infant formula, including the FAST index. A realistic infant formula model was developed, to compare the reaction kinetics at different temperatures (80–110
°C) for lactulosyllysine, measured as furosine, hydroxymethylfurfural and carboxymethyllysine. By comparing the Arrhenius plots of the three Maillard products to that of the FAST index, the latter was identified as the most sensitive indicator for infant formula quality monitoring during heat treatment.
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