Is binary sequential decay compatible with the fragmentation of nuclei at high energy?

We use a binary sequential decay model in order to describe the fragmentation of a nucleus induced by the high energy collisions of protons with Au nuclei. Overall agreement between measured and calculated physical observables is obtained. We evaluate and analyse the decay times obtained with two different parametrisations of the decay rates and discuss the applicability of the model to high energy fragmentation.Comment: 6 pages, 4 eps figures. Small changes at the end of the text. More arguments are given in the discussion of the time scale of the proces

Multifragmentation in Collisions of 4.4gev-Deuterons with Gold Target

The relative velocity correlation function of pairs of intermediate mass fragments has been studied for d+Au collitions at 4.4 GeV. Experimental correlation functions are compared to that obtained by multibody Coulomb trajectory calculations under the assumption of various decay timees of the fragmenting system. The combined approach with the empirically modified intranuclear cascade code followed by the statistical multifragmentation model was used to generate the starting conditions for these calculations. The fragment emossion time is found to be less than 40 fm/c.Comment: Accepted for publication in Bulletin of the Russian Academy of Sciences. Physic

Multifragmentation and nuclear phase transitions (liquid-fog and liquid-gas)

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition. The charge distributions of the intermediate mass fragments produced in p(3.6 GeV) + Au and p(8.1 GeV) + Au collisions are analyzed within the statistical multifragmentation model with the critical temperature for the nuclear liquid-gas phase transition Tc as a free parameter. The analysis presented here provides strong support for a value of Tc > 15 MeV.Comment: 4 pages, 2 figures, Submittet to Proc. of NN2003 to be published in Nucl. Phys.

Critical Temperature for the Nuclear Liquid-Gas Phase Transition

The charge distribution of the intermediate mass fragments produced in p (8.1 GeV) + Au collisions is analyzed in the framework of the statistical multifragmentation model with the critical temperature for the nuclear liquid-gas phase transition $T_c$ as a free parameter. It is found that $T_c=20\pm3$ MeV (90% CL).Comment: 4 pages, 3 figures, published in Phys. Rev.

Critical temperature for the nuclear liquid-gas phase transition (from multifragmentation and fission)

Critical temperature Tc for the nuclear liquid-gas phase transition is stimated both from the multifragmentation and fission data. In the first case,the critical temperature is obtained by analysis of the IMF yields in p(8.1 GeV)+Au collisions within the statistical model of multifragmentation (SMM). In the second case, the experimental fission probability for excited 188Os is compared with the calculated one with Tc as a free parameter. It is concluded for both cases that the critical temperature is higher than 16 MeV.Comment: 15 pages, 8 figure

Statistical Multifragmentation of Non-Spherical Expanding Sources in Central Heavy-Ion Collisions

We study the anisotropy effects measured with INDRA at GSI in central collisions of Xe+Sn at 50 A.MeV and Au+Au at 60, 80, 100 A.MeV incident energy. The microcanonical multifragmentation model with non-spherical sources is used to simulate an incomplete shape relaxation of the multifragmenting system. This model is employed to interpret observed anisotropic distributions in the fragment size and mean kinetic energy. The data can be well reproduced if an expanding prolate source aligned along the beam direction is assumed. An either non-Hubblean or non-isotropic radial expansion is required to describe the fragment kinetic energies and their anisotropy. The qualitative similarity of the results for the studied reactions suggests that the concept of a longitudinally elongated freeze-out configuration is generally applicable for central collisions of heavy systems. The deformation decreases slightly with increasing beam energy.Comment: 35 pages, 19 figures, submitted to Nuclear Physics

Морфофункциональная характеристика отека-набухания коры головного мозга белых крыс после тяжелой черепно-мозговой травмы без и на фоне применения L-лизина эсцината

Aim of study The study is devoted to a morphometric assessment of the manifestations of edema-swelling of the somatosensory cortex (SSC) of the brain of white rats after severe traumatic brain injury (TBI) without using L-lysine escinate and when using it as a therapeutic effect.Material and methods We stained sections with hematoxylin-eosin and performed morphometric methods. On thin (4 μm) serial frontal sections of SSC, neurons and microvessels in the control (intact animals, n=5) were examined in 1 (n= 5), 3 (n=5), 5 (n=5), 7 (n=5) and 14 (n=5) days after injury without treatment (n=25, comparison group) and with treatment (n=25, main group). In color raster images (lens x100), using the plug-in filter “Find Maxima”, maximum brightness areas (MBA) were determined , which were then analyzed using the “Analyze Particles” program from ImageJ 1.52 s. MBA corresponded to SSC sites with a high degree of hydration of nerve tissue - edema-swelling. Statistical hypotheses were tested using nonparametric criteria.Results and discussion In control animals, a low degree of hydration of SSC tissue was noted (relative area 3-8%). In the comparison group, 1 and 3 days after STBI, foci of edema-swelling covered up to 30% of SSC, in 5 days - up to 15%, in 7 days - up to 20%, in 15 - up to 18%. Significant heteromorphism and heterogeneity of changes in the neuropil around neurons and blood vessels was noted. In the dynamics of the post-traumatic period, the proportion of large foci of edema-swelling (intra- and perineuronal, perivascular) decreased. In the main group, one day after STBI, there was a statistically significantly smaller number of foci of edema-swelling and their total relative area. The values range of these variables significantly decreased. L-lysine escinat affected the water balance most effectively in the acute post-traumatic period (day 1 and 3). The drug “smoothed out” the manifestation peaks (number, focal area) of edema-swelling: the values of the studied morphometric indicators were statistically significantly different. Consequently, morphometric signs of hydropic dystrophy after STBI were detected in both studied groups during the 15 days of observation.Conclusion The degree of SSC nervous tissue hydration increased after STBI. L-lysine escinate statistically significantly reduced manifestations of hydropic dystrophy. The drug significantly affected the degree of hydration of neural tissue observed in the early post-traumatic period.Цель Исследование посвящено морфометрической оценке проявлений отека-набухания соматосенсорной коры (ССК) головного мозга белых крыс после тяжелой черепно-мозговой травмы (ТЧМТ) на фоне использования в качестве лечебного воздействия L-лизина эсцината.Методы исследования Использована окраска срезов гематоксилином-иозином и методы морфометрии. На тонких (4 мкм) серийных фронтальных срезах ССК изучены нейроны и микрососуды в контроле (интактные животные, n=5), через 1 (n=5), 3 (n=5), 5 (n=5), 7 (n=5) и 14 (n=5) суток после травмы без лечения (n=25, группа сравнения) и с лечением (n=25, основная группа). На цветных растровых изображениях (объектив х100) с помощью плагин-фильтра “Find Maxima” определяли зоны максимальной яркости, которые затем анализировали с помощью “Analyze Particles” из программы ImageJ 1.52s. Зоны соответствовали участкам ССК с высокой степенью гидратации нервной ткани - отек-набухание. Статистические гипотезы проверяли с помощью непараметрических критериев.Результаты и обсуждение У контрольных животных отмечена низкая степень гидратации нервной ткани ССК (относительная площадь 3−8%). В группе сравнения через 1 и 3 суток после ТЧМТ очаги отека-набухания охватывали до 30% ССК, через 5 суток - до 15%, через 7 суток - до 20%, через 15 - до 18%. Отмечалась значительная гетероморфность и гетерогенность изменений в нейропиле, вокруг нейронов и сосудов. В динамике посттравматического периода доля крупных очагов отека-набухания (интра- и перинейрональных, периваскулярных) снижалась. В основной группе через одни сутки после ТЧМТ было статистически значимо меньшее количество очагов отека-набухания и их общая относительная площадь была меньше, чем в группе сравнения. Значительно уменьшался разброс значений данных переменных. Наиболее эффективно L-лизина эсцинат действовал на водный баланс в остром посттравматическом периоде (1-е и 3-и сутки). Препарат «сглаживал»  пики проявлений (количество, площадь очагов) отека-набухания: значения изученных морфометрических показателей статистически значимо отличались. Следовательно, морфометрическиепризнаки гидропической дистрофии после ТЧМТ выявлялись в обеих изученных группах на протяжении 15 суток наблюдения.Заключение После ТЧМТ увеличивалась степень гидратации нервной ткани ССК. L-лизин эсцинат статистически значимо уменьшал проявления гидропической дистрофии. Особенно выраженное влияние препарата на степень гидратации нервной ткани отмечено в раннем посттравматическом периоде