New representation of orbital motion with arbitrary angular momenta

A new formulation is presented for a variational calculation of $N$-body systems on a correlated Gaussian basis with arbitrary angular momenta. The rotational motion of the system is described with a single spherical harmonic of the total angular momentum $L$, and thereby needs no explicit coupling of partial waves between particles. A simple generating function for the correlated Gaussian is exploited to derive the matrix elements. The formulation is applied to various Coulomb three-body systems such as $e^-e^-e^+, tt\mu, td\mu$, and $\alpha e^-e^-$ up to $L=4$ in order to show its usefulness and versatility. A stochastic selection of the basis functions gives good results for various angular momentum states.Comment: Revte

Competition of fusion and quasi-fission in the reactions leading to production of the superheavy elements

The mechanism of fusion hindrance, an effect observed in the reactions of cold, warm and hot fusion leading to production of the superheavy elements, is investigated. A systematics of transfermium production cross sections is used to determine fusion probabilities. Mechanism of fusion hindrance is described as a competition of fusion and quasi-fission. Available evaporation residue cross sections in the superheavy region are reproduced satisfactorily. Analysis of the measured capture cross sections is performed and a sudden disappearance of the capture cross sections is observed at low fusion probabilities. A dependence of the fusion hindrance on the asymmetry of the projectile-target system is investigated using the available data. The most promising pathways for further experiments are suggested.Comment: 8 pages, 7 figures, talk presented at 7th International School-Seminar on Heavy-Ion Physics, May 27 - June 1, 2002, Dubna, Russi

Precise solution of few-body problems with stochastic variational method on correlated Gaussian basis

Precise variational solutions are given for problems involving diverse fermionic and bosonic $N=2-7$-body systems. The trial wave functions are chosen to be combinations of correlated Gaussians, which are constructed from products of the single-particle Gaussian wave packets through an integral transformation, thereby facilitating fully analytical calculations of the matrix elements. The nonlinear parameters of the trial function are chosen by a stochastic technique. The method has proved very efficient, virtually exact, and it seems feasible for any few-body bound-state problems emerging in nuclear or atomic physics.Comment: 39 pages (revtex) + 3 figures (appended as compressed uuencoded .ps files

ИСПОЛЬЗОВАНИЕ СИСТЕМЫ УПРАВЛЕНИЯ РИСКАМИ ДЛЯ СОВЕРШЕНСТВОВАНИЯ САНИТАРНО-ЭПИДЕМИОЛОГИЧЕСКОГО КОНТРОЛЯ И НАДЗОРА

The article reviewsthe possibility to work out and introduce risk-oriented model for control and surveillance in the field of the sanitary-epidemiological well-being of the population in the Russian Federation. In implementation of risk-oriented approaches, choice of a model is of importance. If the static model is the starting one, then in the future, the dynamic model will be the most promising allowing for assessment of stability of the sanitary-epidemiologic situation in time. Introduction and development of risk-oriented models for control and surveillance is the actual objective at realization of sanitary-epidemiological control (surveillance) . It is necessary to work out and harmonize concept, procedural apparatus, and scientific and methodological support of risk-oriented control and surveillance on the base of the best world patterns and standards.Приведен анализ возможности применения системы оценки рисков для здоровья при осуществлении мероприятий по контролю (надзору) и внедрении этого опыта в Российской Федерации. При внедрении риск-ориентированных подходов важным является выбор модели. При этом если стартовой будет статическая модель, то в дальнейшем наиболее перспективной будет динамическая модель, позволяющая оценить устойчивость санитарно-эпидемиологической ситуации во времени. Внедрение и совершенствование риск-ориентированных моделей контроля и надзора является актуальной задачей при проведении санитарно-эпидемиологического надзора (контроля). Необходима разработка и гармонизация понятийного, процедурного аппарата и научно-методического обеспечения риск-ориентированной контрольно-надзорной деятельности на базе лучших мировых образцов и стандартов

Chemical Identification of a Long-Lived Isotope of Dubnium, a Descendant of Element 115

The recognition criterion for discovery of a new chemical element includes two aspects, the characterization properties and the assignment properties. In this paper, we will discuss the status of element 115 experiments that have been performed in Dubna, Russia, highlighting the characterization and assignment properties as they specifically relate to a recent experiment. After discussing the status of what is known about the decay properties of element 115 [1], observed previously using the Dubna Gas-Filled Recoil Separator, we will discuss the prior chemical studies that have been performed on the Db descendant of element 115 [2]. Following the success of that experiment, some additional chemical information was desired. Two separation chemistries were then developed at LLNL and JINR. LLNL utilized reversed phase chromatography and JINR utilized anion exchange chromatography to perform not only +4/+5 separations, but also intra-group separations, where Nb-like and Ta-like fractions were eluted. The results from an experiment using these chemistries for the first time during December 2005 in Dubna, Russia, will be compared with prior chemical results. We will conclude with a discussion of possible enhancements to the work already performed and the current status of the future experimental plans

Ceramic Plutonium Target Development for the MASHA Separator for the Synthesis of Element 114

We are currently developing a Pu ceramic target for the MASHA mass separator. MASHA will use a Pu ceramic target capable of tolerating temperatures up to 2000 C. Reaction products will diffuse out of the target into an ion source, and transported through the separator to a position-sensitive focal-plane detector array for mass identification. Experiments on MASHA will allow us to make measurements that will cement our identification of element 114 and provide data for future experiments on chemical properties of the heaviest elements. In this study (Sm,Zr)O{sub 2-x} ceramics are produced and evaluated for studies on the production of Pb (homolog of element 114) by the reaction of Ca on Sm. This work will provide an initial analysis on the feasibility of using a ZrO{sub 2}-PuO{sub 2} as a target for the production of element 114