160 research outputs found

    Treatment of competition between complete fusion and quasifission in collisions of heavy nuclei

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    A model of competition between complete fusion and quasifission channels in fusion of two massive nuclei is extended to include the influence of dissipative effects on the dynamics of nuclear fusion. By using the multidimensional Kramers-type stationary solution of the Fokker-Planck equation, the fusion rate through the inner fusion barrier in mass asymmetry is studied. Fusion probabilities in symmetric 90Zr+90Zr, 100Mo+100Mo, 110Pd+110Pd, 136Xe+136Xe, almost symmetric 86Kr+136Xe and 110Pd+136Xe reactions are calculated. An estimation of the fusion probabilities is given for asymmetrical 62Ni+208Pb, 70Zn+208Pb, 82Se+208Pb, and 48Ca+244Pu reactions used for the synthesis of new superheavy elements.Comment: 29 pages, LaTeX, including 7 postscript figures, to appear in Nucl. Phys.

    Fusion cross sections for superheavy nuclei in the dinuclear system concept

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    Using the dinuclear system concept we present calculations of production cross sections for the heaviest nuclei. The obtained results are in a good agreement with the experimental data. The experimentally observed rapid fall-off of the cross sections of the cold fusion with increasing charge number ZZ of the compound nucleus is explained. Optimal experimental conditions for the synthesis of the superheavy nuclei are suggested.Comment: 16 pages, LaTeX, including 3 postscript figure

    Dynamical restriction for a growing neck due to mass parameters in a dinuclear system

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    Mass parameters for collective variables of a dinuclear system and strongly deformed mononucleus are microscopically formulated with the linear response theory making use of the width of single particle states and the fluctuation-dissipation theorem. For the relative motion of the nuclei and for the degree of freedom describing the neck between the nuclei, we calculate mass parameters with basis states of the adiabatic and diabatic two-center shell model. Microscopical mass parameters are found larger than the ones obtained with the hydrodynamical model and give a strong hindrance for a melting of the dinuclear system along the internuclear distance into a compound system. Therefore, the dinuclear system lives a long time enough comparable to the reaction time for fusion by nucleon transfer. Consequences of this effect for the complete fusion process are discussed.Comment: 22 pages, 7 figures, submitted to Nucl.Phys.

    Гематологічні та біохімічні показники крові спортивних коней української верхової та тракененської порід

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    The article presents the results of studies of the morphological composition and biochemical indices of the blood of sports horses of the Ukrainian riding and trakehner breed. The aim of the work was to study the physical loads on the hematologic indices, by which it is possible to judge the level of training and, accordingly, the loads performed on the clinical and physiological condition of horses. The research task consisted of determining the effect of training (before and after) on the morphological composition of the blood, clarifying the changes in the biochemical composition of the serum (glucose, reserve alkalinity and lactic acid) in horses of these breeds of 6 years of age. The horses were kept in the same conditions of microclimate, feeding and maintenance. Evaluation of the clinical state of animals was carried out according to the composition of the leukocyte formula: the number of erythrocytes, leukocytes, lymphocytes, monocytes, neutrophils, platelets and hemoglobin content, and biochemical parameters according to methods of research common in veterinary medicine.The results of the studies showed that after intensive training in horses, the level of hemoglobin increases by – 12.5%, in traken - by 3.8% (P < 0.05), what causes the response of the body to hypoxia, due to less adaptation to stressful Impacts. This is confirmed by an increase in the number of red blood cells after loading – 13.1%, neutrophils by 3.3%, lymphocytes by 7.8% (P < 0.05). The level of glucose provides 55% of the energy requirement of the body, in the case of the trakehner breed, after the load, it decreased by 4.5%, in the OHR by 17.2% (P < 0.05), which indicates the absence of negative effects on the physiological condition of the horses.В статье приведены результаты исследований морфологического состава и биохимических показателей крови спортивных лошадей украинской верховой и тракененской породы. Целью работы было изучение физических нагрузок на гематологические показатели, по которым можно судить об уровне тренированости и соответственно выполненных нагрузок на клинико-физологическое состояние лошадей. В задачу исследований входило установление влияния тренировок (до и после) на морфологический состав крови, выяснения изменений биохимического состава сыворотки (глюкозы, резервной щелочности и молочной кислоты) у лошадей указанных пород 4–6 летнего возраста. Кони содержались в одинаковых условиях микроклимата, кормления и обслуживания. Оценку клинического состояния животных проводили по составу лейкоцитарной формулы: количества эритроцитов, лейкоцитов, лимфоцитов, моноцитов, нейтрофилов, тромбоцитов, а также содержания гемоглобина, биохимическим показателям по общепринятым в ветеринарии методами.Результаты исследований показали, что после интенсивных тренировок у лошадей УВП повышается концентрация гемоглобина на – 12,5%, у тракенов – на 3,8% (Р < 0,05), чем вызвана ответная реакция организма на гипоксию, обусловленной меньшей адаптацией к стрессовым воздействиям. Это подтверждается увеличением после нагрузок количества эритроцитов на – 13,1%, нейтрофилов на – 3,3%, лимфоцитов на – 7,8% (Р <0,05). Уровень глюкозы, обеспечивает на 55% энергетической потребности организма, у животных тракененской породы после нагрузок снизился на 4,5%, в УВП на 17,2% (Р < 0,05), что свидетельствует отсутствием негативных воздействий на физиологическое состояние лошадей.В статті наведені результати досліджень морфологічного складу і біохімічних показників крові спортивних коней української верхової та тракененської пород. Метою роботи було вивчення фізичних навантажень на гематологічні показники, за якими можно судити про рівень тринованості і відповідно виконаних навантажень на клініко-фізологічний стан коней. В завдання досліджень входило встановлення впливу тренувань (до і після) на морфологічний склад крові, з’ясування змін біохімічного складу сироватки (глюкози, резервної лужності і молочної кислоти) у коней вказаних порід 4–6 річного віку. Коні утримувалися в однакових умовах мікроклімату, годування і обслуговування. Оцінку клінічного стану тварин проводили за складом лейкоцитарної формули: кількості еритроцитів, лейкоцитів, лімфоцитів, моноцитів, нейтрофілів, тромбоцитів, а також вмісту гемоглобіну, біохімічні показники - за загальноприйнятими у ветеринарії методами.Результати досліджень показали, що після інтенсивних тренувань у коней УВП підвищується концентрація гемоглобіну на – 12,5%, у тракенів – на 3,8% (Р < 0,05), чим викликана відповідна реакція організму на гіпоксію, обумовленою меншою адаптацією до стресових впливів. Це підтверджується збільшенням після навантажень кількості еритроцитів на – 13,1%, нейтрофілів на – 3,3%, лімфоцитів на – 7,8%, (Р < 0,05). Рівень глюкози, забезпечує на 55% енергетичну потребу організму, у тварин тракененської породи після навантажень знизився на 4,5%, у УВП на 17,2% (Р < 0,05), що свідчить про відсутність негативних впливів на фізіологічний стан коней

    Melting or nucleon transfer in fusion of heavy nuclei?

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    The time-dependent transition between a diabatic interaction potential in the entrance channel and an adiabatic potential during the fusion process is investigated within the two-center shell model. A large hindrance is obtained for the motion to smaller elongations of near symmetric dinuclear systems. The comparison of the calculated energy thresholds for the complete fusion in different relevant collective variables shows that the dinuclear system prefers to evolve in the mass asymmetry coordinate by nucleon transfer to the compound nucleus.Comment: 14 pages, 3 figures, submitted to Phys.Lett.

    Isotopic dependence of fusion cross sections in reactions with heavy nuclei

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    The dependence of fusion cross section on the isotopic composition of colliding nuclei is analysed within the dinuclear system concept for compound nucleus formation. Probabilities of fusion and surviving probabilities, ingredients of the evaporation residue cross sections, depend decisively on the neutron numbers of the dinuclear system. Evaporation residue cross sections for the production of actinides and superheavy nuclei, listed in table form, are discussed and compared with existing experimental data. Neutron-rich radioactive projectiles are shown to lead to similar fusion cross sections as stable projectiles.Comment: 13 pages, 10 figure

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

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    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^{235}U(nth_{\rm th},f). Calculations showed that in the first stage of this fission reaction, the isotopes 82^{82}Ge and 154^{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^{68}Ni which is observed as the product of the collinear cluster tripartition in the experiment.Comment: 20 pages, 9 figure

    Search for the Production of Element 112 in the 48Ca + 238U Reaction

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    We have searched for the production of element 112 in the reaction of 231 MeV 48Ca with 238U. We have not observed any events with a "one event" upper limit cross section of 1.6 pb for EVR-fission events and 1.8 pb for EVR-alpha events.Comment: 6 pages, 3 figures, submitted to Phys. Rev.

    Cluster Interpretation of Properties of Alternating Parity Bands in Heavy Nuclei

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    The properties of the states of the alternating parity bands in actinides, Ba, Ce and Nd isotopes are analyzed within a cluster model. The model is based on the assumption that cluster type shapes are produced by the collective motion of the nuclear system in the mass asymmetry coordinate. The calculated spin dependences of the parity splitting and of the electric multipole transition moments are in agreement with the experimental data.Comment: 29 pages, 10 figure
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