КЛИНИКО-БИОХИМИЧЕСКАЯ ХАРАКТЕРИСТИКА НЕДОНОШЕННЫХ НОВОРОЖДЕННЫХ С ЭКСТРЕМАЛЬНО НИЗКОЙ И ОЧЕНЬ НИЗКОЙ МАССОЙ ТЕЛА ПРИ РОЖДЕНИИ

The purpose of this work was to study the levels of neurotrophic factor nerve growth of the brain, the levels of vascular endothelial growth factor, the levels of neurospecific enolase and the activity of endothelin-1 in the serum of blood in preterm infants with extremely low birth weight in association with the state of the cerebral circulation, and morphologic changes in the brain. We examined 60 preterm infants, which were divided into two groups depending on weight at birth. In neonates with extremely low birth weight the dysfunction of mechanism of autoregulation in cerebral blood flow was characterized by a decrease in blood flow velocities in the anterior cerebral and in the basilar arteries, in association with low levels of trophic factors in serum to month of life and the developments of degenerative changes in the brain. In neonates with very low birth weight infants in the early neonatal period the vasospasm of cerebral vessels with the activity of neurotrophic factors to month of life gave way to the stabilization of the cerebral hemodynamics.Целью работы стало изучение сывороточного содержания нейротрофического фактора роста нервов головного мозга, васкулоэндотелиального фактора роста, сывороточной концентрации нейроспецифической енолазы и сывороточной активности эндотелина-1 у недоношенных новорожденных с экстремально низкой массой тела в ассоциации с состоянием мозгового кровообращения и морфоструктурными изменениями головного мозга. Обследовано 60 недоношенных новорожденных, которые были разделены на две группы в зависимости от массы тела при рождении. У новорожденных с экстремально низкой массой тела дисфункция механизма ауторегуляции мозгового кровотока в раннем неонатальном периоде характеризовалась снижением показателей скоростей кровотока в передней мозговой и базилярной артериях в ассоциации с низким сывороточным содержанием трофических факторов роста, что к 1 мес жизни обусловливало развитие дистрофических изменений головного мозга. У новорожденных с очень низкой массой тела в раннем неонатальном периоде вазоспазм церебральных сосудов в сочетании с активностью нейротрофических факторов роста к 1 мес жизни сменялся стабилизацией мозговой гемодинамики

Systematics of Inclusive Photon Production in 158 AGeV Pb Induced Reactions on Ni, Nb, and Pb Targets

The multiplicity of inclusive photons has been measured on an event-by-event basis for 158 AGeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at midrapidity (rho_max) and the width of the pseudorapidity distributions have been studied for varying centralities for these collisions. A power law fit to the photon yield as a function of the number of participating nucleons gives a value of 1.13+-0.03 for the exponent. The mean transverse momentum, , of photons determined from the ratio of the measured electromagnetic transverse energy and photon multiplicity, remains almost constant with increasing rho_max. Results are compared with model predictions.Comment: 16 pages including 4 figure

Scaling of Particle and Transverse Energy Production in 208Pb+208Pb collisions at 158 A GeV

Transverse energy, charged particle pseudorapidity distributions and photon transverse momentum spectra have been studied as a function of the number of participants (N_{part}) and the number of binary nucleon-nucleon collisions (N_{coll}) in 158 A GeV Pb+Pb collisions over a wide impact parameter range. A scaling of the transverse energy pseudorapidity density at midrapidity as N_{part}^{1.08 \pm 0.06} and N_{coll}^{0.83 \pm 0.05} is observed. For the charged particle pseudorapidity density at midrapidity we find a scaling as N_{part}^{1.07 \pm 0.04} and N_{coll}^{0.82 \pm 0.03}. This faster than linear scaling with N_{part} indicates a violation of the naive Wounded Nucleon Model.Comment: 13 pages, 16 figures, submitted to European Physical Journal C (revised results for scaling exponents

Centrality Dependence of Neutral Pion Production in 158 A GeV Pb + Pb Collisions

The production of neutral pions in 158AGeV Pb+Pb collisions has been studied in the WA98 experiment at the CERN SPS. Transverse momentum spectra are studied for the range 0.3 GeV/c < mT-m0 < 4.0 GeV/c. The results for central collisions are compared to various models. The centrality dependence of the neutral pion spectral shape and yield is investigated. An invariance of the spectral shape and a simple scaling of the yield with the number of participating nucleons is observed for centralities with greater than about 30 participating nucleons which is most naturally explained by assuming an equilibrated system.Comment: 5 pages, Latex, including 3 eps figures, submitted to Phys.Rev.Lett; updated pQCD comparison due to new input from the author, updated references, corrected plotting error in figure

Search for DCC in 158A GeV Pb+Pb Collisions

A detailed analysis of the phase space distributions of charged particles and photons have been carried out using two independent methods. The results indicate the presence of nonstatistical fluctuations in localized regions of phase space.Comment: Talk at the PANIC99 Conference, June 9-16, 199

Central Pb+Pb Collisions at 158 A GeV/c Studied by Pion-Pion Interferometry

Two-particle correlations have been measured for identified negative pions from central 158 AGeV Pb+Pb collisions and fitted radii of about 7 fm in all dimensions have been obtained. A multi-dimensional study of the radii as a function of kT is presented, including a full correction for the resolution effects of the apparatus. The cross term Rout-long of the standard fit in the Longitudinally CoMoving System (LCMS) and the vl parameter of the generalised Yano-Koonin fit are compatible with 0, suggesting that the source undergoes a boost invariant expansion. The shapes of the correlation functions in Qinv and Qspace have been analyzed in detail. They are not Gaussian but better represented by exponentials. As a consequence, fitting Gaussians to these correlation functions may produce different radii depending on the acceptance of the experimental setup used for the measurement.Comment: 13 pages including 10 figure

Search for Disoriented Chiral Condensates in 158 AGeV Pb+Pb Collisions

The restoration of chiral symmetry and its subsequent breaking through a phase transition has been predicted to create regions of Disoriented Chiral Condensates (DCC). This phenomenon has been predicted to cause anomalous fluctuations in the relative production of charged and neutral pions in high-energy hadronic and nuclear collisions. The WA98 experiment has been used to measure charged and photon multiplicities in the central region of 158 AGeV Pb+Pb collisions at the CERN SPS. In a sample of 212646 events, no clear DCC signal can be distinguished. Using a simple DCC model, we have set a 90% C.L. upper limit on the maximum DCC production allowed by the data.Comment: 20 Pages, LaTeX, uses elsart.cls, 8 eps figures included, submitted to Physics Letters

Present Status and Future of DCC Analysis

Disoriented Chiral Condensates (DCC) have been predicted to form in high energy heavy ion collisions where the approximate chiral symmetry of QCD has been restored. This leads to large imbalances in the production of charged to neutral pions. Sophisticated analysis methods are being developed to disentangle DCC events out of the large background of events with conventionally produced particles. We present a short review of current analysis methods and future prospects.Comment: 12 pages, 5 figures. Invited talk presented at the 13th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 97), Tsukuba, Japan, 1-5 Dec 199

Multiplicity Distributions and Charged-neutral Fluctuations

Results from the multiplicity distributions of inclusive photons and charged particles, scaling of particle multiplicities, event-by-event multiplicity fluctuations, and charged-neutral fluctuations in 158$\cdot A$ GeV Pb+Pb collisions are presented and discussed. A scaling of charged particle multiplicity as $N_{part}^{1.07\pm 0.05}$ and photons as $N_{part}^{1.12\pm 0.03}$ have been observed, indicating violation of naive wounded nucleon model. The analysis of localized charged-neutral fluctuation indicates a model-independent demonstration of non-statistical fluctuations in both charged particles and photons in limited azimuthal regions. However, no correlated charged-neutral fluctuations are observed.Comment: Talk given at the International Symposium on Nuclear Physics (ISNP-2000), Mumbai, India, 18-22 Dec 2000, Proceedings to be published in Pramana, Journal of Physic