Quasifission at extreme sub-barrier energies

With the quantum diffusion approach the behavior of the capture cross-section is investigated in the reactions $^{92,94}$Mo + $^{92,94}$Mo, $^{100}$Ru + $^{100}$Ru, $^{104}$Pd + $^{104}$Pd, and $^{78}$Kr + $^{112}$Sn at deep sub-barrier energies which are lower than the ground state energies of the compound nuclei. Because the capture cross section is the sum of the complete fusion and quasifission cross sections, and the complete fusion cross section is zero at these sub-barrier energies, one can study experimentally the unique quasifission process in these reactions after the capture.Comment: 3 pages, 3 figure

Distribucija vrsta roda pseudomonas u veštačkim jezerima regiona armavir u Jermeniji

Identification and isolation of bacteria from genus Pseudomonas has been carried out form ground water samples used for rainbow trout aquaculture. The comparative analysis of Pseudomonas species in inlet and outlet water samples has been done. 80 water samples were analyzed, 50 from which have been taken from five rainbow trout ponds from Armavir region. Examination of water has been performed by membrane filtration method, using high selective media particularly for genus Pseudomonas. The rapid biochemical identification kits were used to identify the species of the mentioned genus. The relationship between quantitative and qualitative composition of Pseudomonas species and physical-chemical properties of water have been studied. P. fluorescens, P. aeruginosa and P. diminuta had high frequency of occurrence in artesian water. P. fluorescens and P. aeruginosa have been isolated from water samples taken from ponds contaning fish without symptoms of illness. The following species P. anguilliseptica, P. putida, P. diminuta known as a causative agents of pseudomonades of rainbow trout were identified in water where ill fish with ulcers near caudal fins and on back side were present. Co-occurrence of P. anguilliseptica and P. alcaligenes has been noticed.Obavljena je identifikacija i izolacija bakterija roda Pseudomonas iz uzoraka podzemne vode koja se koristi za gajenje pastrmke. Urađena je komparativna analiza vrsta Pseudomonas u uzorcima dovodne i odvodne vode. Analizirano je 80 uzoraka od kojih je 50 uzorkovano iz 5 pastrmskih jezera regiona Armavir. Ispitivanje je obavljeno korišćenjem metode membranske filtracije upotrebom visoko selektivnih medija na rod Pseudomonas. Korišćeni su kitovi za brzu biohemijsku identifikaciju vrsta pomenutog roda. Ispitivan je odnos između kvantitativnog i kvalitativnog sastava vrsta Pseudomonas i fizičko hemijskih osobina vode. Vrste P. fluorescens, P. aeruginosa i P. diminuta su imale visoku frekvenciju pojavljivanja u arteškoj void. P. fluorescens i P. aeruginosa su izolovane iz uzoraka vode uzetih iz jezera koj su sadržala ribu bez znakova bolesti. Vrste P. anguilliseptica, P. putida, P. diminuta poznate kao izazivači pseudomonada kalifornijske pastrmke su identifikovane iz vode gde se nalazila bolesna riba sa ulceracijama u blizini repnog peraja i na leđnoj strain. Zapaženo je i istovremeno prisustvo P. anguilliseptica i P. alcaligenes

Peculiarities of sub-barrier fusion with quantum diffusion approach

With the quantum diffusion approach the unexpected behavior of fusion cross section, angular momentum, and astrophysical S-factor at sub-barrier energies has been revealed. Out of the region of short-range nuclear interaction and action of friction at turning point the decrease rate of the cross section under the barrier becomes smaller. The calculated results for the reactions with spherical nuclei are in a good agreement with the existing experimental data.Comment: 11 pages, 5 figure

Sub-barrier capture with quantum diffusion approach: actinide-based reactions

With the quantum diffusion approach the behavior of capture cross sections and mean-square angular momenta of captured systems are revealed in the reactions with deformed nuclei at subbarrier energies. The calculated results are in a good agreement with existing experimental data. With decreasing bombarding energy under the barrier the external turning point of the nucleusnucleus potential leaves the region of short-range nuclear interaction and action of friction. Because of this change of the regime of interaction, an unexpected enhancement of the capture cross section is expected at bombarding energies far below the Coulomb barrier. This effect is shown its worth in the dependence of mean-square angular momentum of captured system on the bombarding energy. From the comparison of calculated and experimental capture cross sections, the importance of quasifission near the entrance channel is shown for the actinide-based reactions leading to superheavy nuclei.Comment: 11 pages, 16 figures, Regular Articl

Color Transparency Effects in Electron Deuteron Interactions at Intermediate Q^2

High momentum transfer electrodisintegration of polarized and unpolarized deuterium targets, $d(e,e'p)n$ is studied. We show that the importance of final state interactions-FSI, occuring when a knocked out nucleon interacts with the other nucleon, depends strongly on the momentum of the spectator nucleon. In particular, these FSI occur when the essential contributions to the scattering amplitude arise from internucleon distances $\sim 1.5~fm$. But the absorption of the high momentum $\gamma^*$ may produce a point like configuration, which evolves with time. In this case, the final state interactions probe the point like configuration at the early stage of its evolution. The result is that significant color transparency effects, which can either enhance or suppress computed cross sections, are predicted to occur for $\sim 4 GeV^2 \ge Q^2\leq~10~(GeV/c)^2$.Comment: 37 pages LaTex, 12 uuencoded PostScript Figures as separate file, to be published in Z.Phys.

Recent experimental results in sub- and near-barrier heavy ion fusion reactions

Recent advances obtained in the field of near and sub-barrier heavy-ion fusion reactions are reviewed. Emphasis is given to the results obtained in the last decade, and focus will be mainly on the experimental work performed concerning the influence of transfer channels on fusion cross sections and the hindrance phenomenon far below the barrier. Indeed, early data of sub-barrier fusion taught us that cross sections may strongly depend on the low-energy collective modes of the colliding nuclei, and, possibly, on couplings to transfer channels. The coupled-channels (CC) model has been quite successful in the interpretation of the experimental evidences. Fusion barrier distributions often yield the fingerprint of the relevant coupled channels. Recent results obtained by using radioactive beams are reported. At deep sub-barrier energies, the slope of the excitation function in a semi-logarithmic plot keeps increasing in many cases and standard CC calculations over-predict the cross sections. This was named a hindrance phenomenon, and its physical origin is still a matter of debate. Recent theoretical developments suggest that this effect, at least partially, may be a consequence of the Pauli exclusion principle. The hindrance may have far-reaching consequences in astrophysics where fusion of light systems determines stellar evolution during the carbon and oxygen burning stages, and yields important information for exotic reactions that take place in the inner crust of accreting neutron stars.Comment: 40 pages, 63 figures, review paper accepted for EPJ