Topology of "white" stars in relativistic fragmentation of light nuclei

In the present paper, experimental observations of the multifragmentation processes of light relativistic nuclei carried out by means of emulsions are reviewed. Events of the type of "white" stars in which the dissociation of relativistic nuclei is not accompanied by the production of mesons and the target-nucleus fragments are considered. A distinctive feature of the charge topology in the dissociation of the Ne, Mg, Si, and S nuclei is an almost total suppression of the binary splitting of nuclei to fragments with charges higher than 2. The growth of the nuclear fragmentation degree is revealed in an increase in the multiplicity of singly and doubly charged fragments with decreasing charge of the non-excited part of the fragmenting nucleus. The processes of dissociation of stable Li, Be, B, C, N, and O isotopes to charged fragments were used to study special features of the formation of systems consisting of the lightest $\alpha$, d, and t nuclei. Clustering in form of the $^3$He nucleus can be detected in "white" stars via the dissociation of neutron-deficient Be, B, C, and N isotopes.Comment: 20 pages, 3 figures, 9 tables, conference: Conference on Physics of Fundamental Interactions, Moscow, Russia, 1-5 Mar 2004.(Author's translation

Enabling comparison of UrQMD with Geant4 hadronic models

Geant4 has an abundant set of physics models that handle the diverse interaction of particles with matter across a wide energy range. However, there are also many well established reaction codes currently used in the same fields where Geant4 is applied. One such code is the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. In order to take advantage of the UrQMD code, we create a tool to enable comparisons among UrQMD and Geant4 hadronic models. This tool allows a user to process the output file of UrQMD through Geant4 toolkit, while at the same time, can choose among different Geant4 hadronic model generators. As an example, the UrQMD model is compared with the HARP-CDP experimental data and with the Binary and FRITIOF generators, in the framework of Geant4. It is shown that the UrQMD model can better reproduce charged pion production for p+Cu and Pb interactions at 3, 8 and 15 GeV/c, and is a good candidate for Geant4 hadronic models.Comment: 17 pages, 5 Figure

Fragmentation channels of relativistic 7^7Be nuclei in peripheral interactions

Nuclei of $^7$Li were accelerated at the JINR Nuclotron. After the charge-exchange reaction involving these nuclei at an external target a second $^7$Be beam of energy 1.23A GeV was formed. This beam was used to expose photo-emulsion chambers. The mean free path for inelastic $^7$Be interactions in emulsion $\lambda$=14.0$\pm$0.8 cm coincides within the errors with those for $^6$Li and $^7$Li nuclei. More than 10% of the $^7$Be events are associated with the peripheral interactions in which the total charge of the relativistic fragments is equal to the charge of the $^7$Be and in which charged mesons are not produced. An unusual ratio of the isotopes is revealed in the composition of the doubly charged $^7$Be fragments: the number of $^3$He fragments is twice as large as that of $^4$He fragments. In 50% of peripheral interactions, a $^7$Be nucleus decays to two doubly charged fragments. The present paper gives the channels of the $^7$Be fragmentation to charged fragments. In 50% of events, the $^7$Be fragmentation proceeds only to charged fragments involving no emission of neutrons. Of them, the $^3$He+$^4$He channel dominates, the $^4$He+d+p and $^6$Li+pchannels constitute 10% each. Two events involving no emission of neutrons are registered in the 3-body $^3$He+t+p and $^3$He+d+d channels. The mean free path for the coherent dissociation of relativistic $^7$Be nuclei to $^3$He+$^4$He is 7$\pm$1 m. The particular features of the relativistic $^7$Be fragmentation in such peripheral interactions are explained by the $^3$He+$^4$He 2-cluster structure of the $^7$Be nucleus.Comment: 10 pages, 3 figures, 3 tables, conference: Conference on Physics of Fundamental Interactions, Moscow, Russia, 5-9 Dec 200

Promene trofičkog stanja u reci Dnjepar i njihov uticaj na zajednicu riba

Ispitivane su promene structure zajednica fitoplanktona i riba, kao i koncentracije azota i fosfora u međugraničnoj reci Dnjepar. Konstatovano je da je koncentracija mineralnog azota najvažniji factor akumulacije antropogenog zagađenja nizvodno u ispitivanim delovima reke Dnjepar. Ukupna količina riba se povecala nizvodno sa povećanjem trofičkog statusa reke. U isto vreme prosečna individualne težina se nizvodno smanjivala

Clustering in light nuclei in fragmentation above 1 A GeV

The relativistic invariant approach is applied to analyzing the 3.3 A GeV $^{22}$Ne fragmentation in a nuclear track emulsion. New results on few-body dissociations have been obtained from the emulsion exposures to 2.1 A GeV $^{14}$N and 1.2 A GeV $^{9}$Be nuclei. It can be asserted that the use of the invariant approach is an effective means of obtaining conclusions about the behavior of systems involving a few He nuclei at a relative energy close to 1 MeV per nucleon. The first observations of fragmentation of 1.2 A GeV $^{8}$B and $^{9}$C nuclei in emulsion are described. The presented results allow one to justify the development of few-body aspects of nuclear astrophysics.Comment: 7 pages, 8 figures, 3 tables, Nuclear Physics in Astrophysics-2, 16-20 May, 2005 (ATOMKI), Debrecen, Hungar

Reduction of airborne particulate matter emissions associated with petroleum coke production

This article presents the results of studies on production based on products of secondary oil refining processes of agents for dust suppression and reduction of losses from blowing out of wet bulk carbon-containing materials, in particular petroleum coke, as well as against freezing and adhesion during their transportation at low temperatures. The use of the developed dust suppression-antifreeze agent will reduce exposure to dust of the employees at the delayed coking unit in the course of petroleum coke production and improve its freeze resistance. It will have a positive impact on the solution of the problem of petroleum coke transportation at subzero temperatures, and will also allow expanding the range of marketable products, and increasing production efficiency