Role of the target orientation angle and orbital angular momentum in the evaporation residue production

The influence of the orientation angles of the target nucleus symmetry axis relative to the beam direction on the production of the evaporation residues is investigated for the $^{48}$Ca+$^{154}$Sm reaction as a function of the beam energy. At low energies ($E_{\rm c.m.}<$137 MeV), the yield of evaporation residues is observed only for collisions with small orientation angles ($\alpha_T<45^0$). At large energies (about $E_{\rm c.m.}=$140--180 MeV) all the orientation angles $\alpha_T$ can contribute to the evaporation residue cross section $\sigma_{ER}$ in the 10--100 mb range, and at $E_{c.m.}>$180 MeV $\sigma_{ER}$ ranges around 0.1--10 mb because the fission barrier for a compound nucleus decreases by increasing its excitation energy and angular momentum.Comment: 20 pages, 10 figures, submitted to JPS

Quasifission and fusion-fission in massive nuclei reactions. Comparison of reactions leading to the Z=120 element

The yields of evaporation residues, fusion-fission and quasifission fragments in the $^{48}$Ca+$^{144,154}$Sm and $^{16}$O+$^{186}$W reactions are analyzed in the framework of the combined theoretical method based on the dinuclear system concept and advanced statistical model. The measured yields of evaporation residues for the $^{48}$Ca+$^{154}$Sm reaction can be well reproduced. The measured yields of fission fragments are decomposed into contributions coming from fusion-fission, quasifission, and fast-fission. The decrease in the measured yield of quasifission fragments in $^{48}$Ca+$^{154}$Sm at the large collision energies and the lack of quasifission fragments in the $^{48}$Ca+$^{144}$Sm reaction are explained by the overlap in mass-angle distributions of the quasifission and fusion-fission fragments. The investigation of the optimal conditions for the synthesis of the new element $Z$=120 ($A$=302) show that the $^{54}$Cr+$^{248}$Cm reaction is preferable in comparison with the $^{58}$Fe+$^{244}$Pu and $^{64}$Ni+$^{238}$U reactions because the excitation function of the evaporation residues of the former reaction is some orders of magnitude larger than that for the last two reactions.Comment: 27 pages, 12 figures, submitted to Phys. Rev.

South caucasus and a ‘New Great Game’: the communication of competition in securitised international relations

This article seeks to compare and analyse the historical and contemporary arguments concerning the existence of the brand the ‘Great Game’ in Central Asia with that of a ‘new’ Great Game in the South Caucasus, while assessing the validity and problems of using this term. The article analyses the regional state of affairs and possible impacts of the Russian factor in forging close relations between South Caucasus states and NATO. It is argued that Russia’s and NATO’s vested interests in the region rhetorically contribute to European security system in the context of the security environment after the Georgian-Russian War of 2008 and its repercussions. NATO’s presence may be interpreted as counterbalancing the Russian military presence in the region, but there are also clear limits to the alliance’s willingness to actively engage in the region, not least the reluctance to antagonize Moscow. The context of geopolitical competition may be interpreted as a ‘new’ Great Game sharing similarities with nineteenth century competition of great powers, yet a number of clear differences also exist relative to the traditional Great Game. © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group

Collinear cluster tripartition as sequential binary fission in the 235^{235}U(nth_{\rm th},f) reaction

The mechanism leading to the formation of the observed products of the collinear cluster tripartition is carried out within the framework of the model based on the dinuclear system concept. The yield of fission products is calculated using the statistical model based on the driving potentials for the fissionable system. The minima of potential energy of the decaying system correspond to the charge numbers of the products which are produced with large probabilities in the sequential fission (partial case of the collinear cluster tripartition) of the compound nucleus. The realization of this mechanism supposes the asymmetric fission channel as the first stage of sequential mechanism. It is shown that only the use of the driving potential calculated by the binding energies with the shell correction allows us to explain the yield of the true ternary fission products. The theoretical model is applied to research collinear cluster tripartition in the reaction $^{235}$U(n$_{\rm th}$,f). Calculations showed that in the first stage of this fission reaction, the isotopes $^{82}$Ge and $^{154}$Nd are formed with relatively large probabilities and in the second stage of sequential fission of the isotope Nd mainly Ni and Ge are formed. This is in agreement with the yield of the isotope $^{68}$Ni which is observed as the product of the collinear cluster tripartition in the experiment.Comment: 20 pages, 9 figure

Measurements of evaporation residue cross-sections and evaporation residue-gated γ\gamma-ray fold distributions for 32^{32}S+154^{154}Sm system

Evaporation Residue (ER) cross-sections and ER-gated $\gamma$-ray fold distributions are measured for the $^{32}$S + $^{154}$Sm nuclear reaction above the Coulomb barrier at six different beam energies from 148 to 191 MeV. $\gamma$-ray multiplicities and spin distributions are extracted from the ER-gated fold distributions. The ER cross-sections measured in the present work are found to be much higher than what was reported in a previous work using a very different target-projectile ($^{48}$Ti + $^{138}$Ba) combination, leading to the same compound nucleus $^{186}$Pt, with much less mass asymmetry in the entrance channel than the present reaction. This clearly demonstrates the effect of the entrance channel on ER production cross-section. The ER cross-sections measured in the present work are compared with the results of both the statistical model calculations and the dynamical model calculations. Statistical model calculations have been performed to generate a range of parameter space for both the barrier height and Kramers' viscosity parameter over which the ER cross-section data can be reproduced. The calculations performed using the dinuclear system (DNS) model reproduce the data considering both complete and incomplete fusion processes. DNS calculations indicate the need for the inclusion of incomplete fusion channel at higher energies to reproduce the ER cross-sections.Comment: 13 pages, 18 figure

Случай редкого метастазирования рака толстой кишки. Случай из практики

Metastatic lesions in muscles appear to be a rare manifestation of malignant neoplasms with an unfavorable prognosis. To date, due to the low incidence of metastases to the ileo‑lumbar muscle, a definite concept of its treatment does not exist. The article describes the clinical case of a 33‑year‑old patient after a combined treatment of colon cancer in 2017 who progressed 5 months after the end of chemotherapy. Pathomorphological examination after ileo‑lumbar muscle lesion removal revealed metastasis of colon cancer adenocarcinoma. The patient underwent IMRT-SIB radiation therapy and chemotherapy with 5‑FU with no signs of progression for 4 months.Метастатическое поражение мышц является редким проявлением злокачественных новообразований, в том числе, рака толстой кишки. До настоящего времени, в связи с низкой встречаемостью метастазирования в илео-люмбальную мышцу, единой концепции лечения данных отдаленных проявлений болезни не существует. В статье представлено клиническое наблюдение: пациент 33 лет, состояние после комбинированного лечения по поводу рака толстой кишки от 2017 г. в анамнезе. Прогрессирование заболевания спустя 5 месяцев после окончания химиотерапии. По данным морфологического заключения биоптата из илео-люмбальной мышцы — метастаз аденокарциномы толстой кишки. Пациенту выполнено хирургическое удаление метастаза, IMRT-SIB лучевая терапия на аппарате Elekta Synergy на фоне химиотерапии 5-фторурацилом. В настоящее время — без признаков прогрессирования 4 месяца