The importance of initial-final state correlations for the formation of fragments in heavy ion collisions

Using quantum molecular dynamics simulations, we investigate the formation of fragments in symmetric reactions between beam energies of E=30AMeV and 600AMeV. After a comparison with existing data we investigate some observables relevant to tackle equilibration: dsigma/dErat, the double differential cross section dsigma/pt.dpz.dpt,... Apart maybe from very energetic E>400AMeV and very central reactions, none of our simulations gives evidence that the system passes through a state of equilibrium. Later, we address the production mechanisms and find that, whatever the energy, nucleons finally entrained in a fragment exhibit strong initial-final state correlations, in coordinate as well as in momentum space. At high energy those correlations resemble the ones obtained in the participant-spectator model. At low energy the correlations are equally strong, but more complicated; they are a consequence of the Pauli blocking of the nucleon-nucleon collisions, the geometry, and the excitation energy. Studying a second set of time-dependent variables (radii, densities,...), we investigate in details how those correlations survive the reaction especially in central reactions where the nucleons have to pass through the whole system. It appears that some fragments are made of nucleons which were initially correlated, whereas others are formed by nucleons scattered during the reaction into the vicinity of a group of previously correlated nucleons.Comment: 45 pages text + 20 postscript figures Accepted for publication in Physical Review

Информационные технологии в управлении интеллектуальным капиталом организации

The report examines how organization can use information technologies for management of intellectual capital

The neurobiological characterization of distinct cognitive subtypes in early-phase schizophrenia-spectrum disorders

INTRODUCTION: Cognitive deficits are present in some, but not all patients with schizophrenia-spectrum disorders (SSD). We and others have demonstrated three cognitive clusters: cognitively intact patients, patients with deficits in a few domains and those with global cognitive deficits. This study aimed to identify cognitive subtypes of early-phase SSD with matched controls as a reference group, and evaluated cognitive subgroups regarding clinical and brain volumetric measures. METHODS: Eighty-six early-phase SSD patients were included. Hierarchical cluster analysis was conducted using global performance on the Brief Assessment of Cognition in Schizophrenia (BACS). Cognitive subgroups were subsequently related to clinical and brain volumetric measures (cortical, subcortical and cortical thickness) using ANCOVA. RESULTS: Three distinct cognitive clusters emerged: relative to controls we found one cluster of patients with preserved cognition (n = 25), one moderately impaired cluster (n = 38) and one severely impaired cluster (n = 23). Cognitive subgroups were characterized by differences in volume of the left postcentral gyrus, left middle caudal frontal gyrus and left insula, while differences in cortical thickness were predominantly found in fronto-parietal regions. No differences were demonstrated in subcortical brain volume. DISCUSSION: Current results replicate the existence of three distinct cognitive subgroups including one relatively large group with preserved cognitive function. Cognitive subgroups were characterized by differences in cortical regional brain volume and cortical thickness, suggesting associations with cortical, but not subcortical development and cognitive functioning such as attention, executive functions and speed of processing

Exploring wind-driving dust species in cool luminous giants I. Basic criteria and dynamical models of M-type AGB stars

This work is part of an ongoing effort aiming at identifying the actual wind-drivers among the dust species observed in circumstellar envelopes. In particular, we focus on the interplay between a strong stellar radiation field and the dust formation process. To identify critical properties of potential wind-driving dust species we use detailed radiation-hydrodynamical models which include a parameterized dust description, complemented by simple analytical estimates to help with the physical interpretation of the numerical results. The adopted dust description is constructed to mimic different chemical and optical dust properties in order to systematically study the effects of a realistic radiation field on the second stage of the mass loss mechanism. We see distinct trends in which combinations of optical and chemical dust properties are needed to trigger an outflow. Dust species with a low condensation temperature and a NIR absorption coefficient that decreases strongly with wavelength will not condense close enough to the stellar surface to be considered as potential wind-drivers. Our models confirm that metallic iron and Fe-bearing silicates are not viable as wind-drivers due to their near-infrared optical properties and resulting large condensation distances. TiO2 is also excluded as a wind-driver due to the low abundance of Ti. Other species, such a SiO2 and Al2O3, are less clear-cut cases due to uncertainties in the optical and chemical data and further work is needed. A strong candidate is Mg2SiO4 with grain sizes of 0.1-1 micron, where scattering contributes significantly to the radiative acceleration, as suggested by earlier theoretical work and supported by recent observations.Comment: 15 pages, 12 figure

Transport through a double quantum dot system with non-collinearly polarized leads

We investigate linear and non-linear transport in a double quantum dot system weakly coupled to spin-polarized leads. In the linear regime, the conductance as well as the non-equilibrium spin accumulation are evaluated in analytic form. The conductance as a function of the gate voltage exhibits four peaks of different height, with mirror symmetry with respect to the charge neutrality point. As the polarization angle is varied, the position and shape of the peaks changes in a characteristic way which preserves the electron-hole symmetry of the problem. In the nonlinear regime negative differential conductance features occur for non collinear magnetisations of the leads. In the considered sequential tunneling limit, the tunneling magneto resistance (TMR) is always positive with a characteristic gate voltage dependence for non-collinear magnetization. If a magnetic field is added to the system, the TMR can become negative.Comment: 18 pages, 13 figures, 5 tables; revised published versio

Break-up stage restoration in multifragmentation reactions

In the case of Xe+Sn at 32 MeV/nucleon multifragmentation reaction break-up fragments are built-up from the experimentally detected ones using evaluations of light particle evaporation multiplicities which thus settle fragment internal excitation. Freeze-out characteristics are extracted from experimental kinetic energy spectra under the assumption of full decoupling between fragment formation and energy dissipated in different degrees of freedom. Thermal kinetic energy is determined uniquely while for freeze-out volume - collective energy a multiple solution is obtained. Coherence between the solutions of the break-up restoration algorithm and the predictions of a multifragmentation model with identical definition of primary fragments is regarded as a way to select the true value. The broad kinetic energy spectrum of $^3$He is consistent with break-up genesis of this isotope.Comment: 17 pages, 5 figure

Lower fractional anisotropy without evidence for neuro-inflammation in patients with early-phase schizophrenia spectrum disorders

Various lines of research suggest immune dysregulation as a potential therapeutic target for negative and cognitive symptoms in schizophrenia spectrum disorders (SSD). Immune dysregulation would lead to higher extracellular free-water (EFW) in cerebral white matter (WM), which may partially underlie the frequently reported lower fractional anisotropy (FA) in SSD. We aim to investigate differences in EFW concentrations – a presumed proxy for neuro-inflammation – between early-phase SSD patients (n = 55) and healthy controls (HC; n = 37), and to explore immunological and cognitive correlates. To increase specificity for EFW, we study several complementary magnetic resonance imaging contrasts that are sensitive to EFW. FA, mean diffusivity (MD), magnetization transfer ratio (MTR), myelin water fraction (MWF) and quantitative T1 and T2 were calculated from diffusion-weighted imaging (DWI), magnetization transfer imaging (MTI) and multicomponent driven equilibrium single-pulse observation of T1/T2 (mcDESPOT). For each measure, WM skeletons were constructed with tract-based spatial statistics. Multivariate SSD-HC comparisons with WM skeletons and their average values (i.e. global WM) were not statistically significant. In voxel-wise analyses, FA was significantly lower in SSD in the genu of the corpus callosum and in the left superior longitudinal fasciculus (p < 0.04). Global WM measures did not correlate with immunological markers (i.e. IL1-RA, IL-6, IL-8, IL-10 and CRP) or cognition in HC and SSD after corrections for multiple comparisons. We confirmed lower FA in early-phase SSD patients. However, non–FA measures did not provide additional evidence for immune dysregulation or for higher EFW as the primary mechanism underlying the reported lower FA values in SSD

Breakup Density in Spectator Fragmentation

Proton-proton correlations and correlations of protons, deuterons and tritons with alpha particles from spectator decays following 197Au + 197Au collisions at 1000 MeV per nucleon have been measured with two highly efficient detector hodoscopes. The constructed correlation functions, interpreted within the approximation of a simultaneous volume decay, indicate a moderate expansion and low breakup densities, similar to assumptions made in statistical multifragmentation models. PACS numbers: 25.70.Pq, 21.65.+f, 25.70.Mn, 25.75.GzComment: 11 pages, LaTeX with 3 included figures; Also available from http://www-kp3.gsi.de/www/kp3/aladin_publications.htm

Condensation of MgS in outflows from carbon stars

The basic mechanism responsible for the widespread condensation of MgS in the outflows from carbon rich stars on the tip of the AGB is discussed with the aim of developing a condensation model that can be applied in model calculations of dust formation in stellar winds. The different possibilities how MgS may be formed in the chemical environment of outflows from carbon stars are explored by some thermochemical calculations and by a detailed analysis of the growth kinetics of grains in stellar winds. The optical properties of core-mantle grains with a MgS mantle are calculated to demonstrate that such grains reproduce the structure of the observed 30 $\mu$m feature. These considerations are complemented by model calculations of circumstellar dust shells around carbon stars. It is argued that MgS is formed via precipitation on silicon carbide grains. This formation mechanism explains some of the basic observed features of MgS condensation in dust shells around carbon stars. A weak secondary peak at about 33 ... 36 $\mu$m is shown to exist in certain cases if MgS forms a coating on SiC.Comment: 9 pages, 7 figure