Solvent extraction study of protactinium(V) with methyl-iso-butyl carbinol and methyl-iso-butyl ketone

In order to study the extraction pattern of protactinium in different types of extracting agents and compare the similarity of patterns of extraction with dubnium and thereby unraveling its chemistry, solvent extraction of protactinium(V) with methyl-iso-butyl carbinol (MIBC) and methyl-iso-butyl ketone (MIBK) was studied using Pa-233 as a radiotracer. The extraction efficiencies of Pa were determined as a function of shaking time, concentrations of mineral acids, and extractant concentrations using the two extractants. The results show that MIBK is more suitable for the extraction of protactinium than MIBC in benzene. Furthermore, the effect of the F anion is also discussed.

V5+-doped Bi3.4Yb0.6Ti3O12 fatigue resistant ferroelectric thin films

In this paper, a serial of Bi3.4Yb0.6Ti3-xVxO12 (BYTV) thin film with different V5+ contents were deposited on Pt/Ti/SiO2/Si substrates by chemical solution deposition (CSD). The crystallized phase and electrical properties of the films were investigated using X-ray diffraction, polarization hysteresis loops, leakage current-voltage, and fatigue test. From our experimental results, it can be found that the ferroelectric properties can be improved greatly using V5+-doped in Bi3.4Yb0.6Ti3O12 (BYT) thin film, compared with the reported BYT thin film. The remanent polarization was enhanced and excellent leakage current characteristic with 10(-11)A at the bias voltage of 4V, which is much lower than the BYT thin film or some reported bismuth layer-structure ferroelectric films. Fatigue test shows that the fabricated films have good anti-fatigue characteristic after 10(10) switching cycles. (c) 2008 Published by Elsevier B.V.

beta-delayed fission of Ac-228

The basic process of an exotic decay mode namely P-delayed fission is simply introduced. The progress status of the study in the world is essentialized. The observation of P-delayed fission of Ac-228 is reported. The radium was radiochemically separated from natural thorium. Thin Ra sources in which Ac-228 was got through Ra-228 ->(beta-) Ac-228 were prepared for observing fission fragments from beta-delayed fission Ac-228. They exposed to the mica fission track detectors, and measured by an HPGe gamma-ray detector. The beta-delayed fission events of Ac-228 were observed and its beta-delayed fission probability was found to be (5 +/- 2) x 10(-12).

Production cross-section of Ra-230 in the reaction of 60 MeV/u O-18 ions with U-238

A thick natural uranium target was bombarded with a 60 MeV/u O-18 beam. The neutron-rich isotope Ra-230 as the target residue was produced through the multinucleon transfer reaction (U-238-4p-4n). The barium and radium fraction as BaCl2 precipitate were radiochemically separated first from the mixture of uranium and reaction products. Then, the radium fraction was separated from BaCl2 precipitate by using cation exchange technique. The gamma-ray spectra of the Ra fraction were measured using an HPGe detector. The production cross sections of Ra-230 were obtained by a combination of the radiochemical separation technique and off-line gamma-ray spectroscopy. The cross section of Ra-230 has been determined to be 66 +/- 20 mu b.

Production cross section of Th-236 in the interaction of U-238 with 60 MeV/u O-18 ions

The neutron-rich target-like isotope Th-236 has been produced in the U-238-2p multinucleon transfer reaction between a 60 MeV/u O-18 beam and natural U-238 targets. The activities of thorium were determined after radiochemical separation of Th from the mixture of uranium and reaction products. The Th-236 isotope was identified by the characteristic gamma-rays of 642.2, 687.6 and 229.6 keV. The production cross section of Th-236 was determined to be 250 +/- 50 mu b.

Liquid-liquid extraction of protactinium(V) using tri-iso-octylamine

Solvent extraction of protactinium with tri-iso-octyl-amine (TIOA) in xylene, benzene, carbon tetrachloride and chloroform from HCl, HF, HNO3, HClO4 and H2SO4 media was studied using Pa-233 as a radiotracer. The extraction efficiencies of protactinium were determined as a function of shaking time, concentrations of mineral acids in aqueous phase, extractant concentrations and diluents in organic phase. The extraction mechanism was discussed. The results show that the extracted species in the organic phase is [(R3N-H)(n)Pa(OH)(x)Cl-y(5-x-y)].

Production cross-section of Th-236 in the interaction of U-238 with 60MeV/u O-18 Ions

The neutron-rich target-like isotope Th-236 was produced in U-238-2p multinucleon transfer reaction between a 60MeV/u O-18 beam and nature U-238 targets. The thorium activities were radiochemically separated from the mixture of uranium and reaction products. The isotope Th-236 was identified by 642.2keV, 687.6keV and 229.6keV characteristic gamma-rays. The production cross section of Th-236 has been determined to be 250 +/- 50 mu b.

Pa-239 may influence astrophysics study

The estimation method of the universe age using the nuclear cosmochronology by the heavy chronometers is essentialized. The influence of the novel long half-life of Pa-239 on the universe age estimation is simply mentioned.

Search for beta-delayed fission of Ac-228

Radium was radiochemically separated from natural thorium. Thin Ra-228 ->beta Ac-228 sources were prepared and exposed to mica fission track detectors, and measured by an HPGe gamma-ray detector. The beta-delayed fission events of Ac-228 were observed and its beta-delayed fission probability was found to be (5 +/- 2)x10(-12).

Particle transfer and fusion cross-section for super-heavy nuclei in dinuclear system

Within the dinuclear system (DNS) conception, instead of solving the Fokker-Planck equation (FPE) analytically, the master equation is solved numerically to calculate the fusion probability of super-heavy nuclei, so that the harmonic oscillator approximation to the potential energy of the DNS is avoided. The relative motion concerning the energy, the angular momentum and the fragment deformation relaxations is explicitly treated to couple with the diffusion process. The nucleon transition probabilities, which are derived microscopically, are related with the energy dissipation of the relative motion. Thus they are time dependent. Comparing with the analytical solution of FPE at the equilibrium, our time-dependent results preserve more dynamical effects. The calculated evaporation residue cross-sections for one-neutron emission channel of Pb-based reactions are basically in agreement with the known experimental data within one order of magnitude.

Monte Carlo simulation of the neutron detection wall at RIBLL II in HIRFL-CSR

With the construction of the new Radioactive Ion Beam Line in Lanzhou (RIBLL II) which connects the CSRm and the CSRe, an experimental setup for physics research is highly required. A large area neutron detection wall is the main part of the setup. This paper introduced the detection principle of the neutron detection wall and the Monte-Carlo simulation of its design under the environment of the Geant4 toolkit. We presented the final design with the optimized parameters and the performance of the wall.

长白山北坡水甲虫多样性与环境因子的关系

为了解水甲虫多样性与环境的关系,于2004—2006年每年6—10月在长白山北坡采集不同环境条件下水甲虫标本,共发现水甲虫8科38属70种。研究发现不同的环境,水甲虫的种类、数量、个体大小明显不同。通过多元回归分析发现:水甲虫Shannon-Wiener多样性指数与海拔(r=0.507)、底泥有机质含量(r=0.638)和全磷含量(r=0.668)成明显正相关,与水电导率(r=-0.470)、水深度(r=-0.461)和水pH值(r=-0.470)负相关显著;均匀度指数与底泥有机质含量(r=0.542)和全磷含量(r=0.489)正相关显著;物种数与海拔(r=0.590)、底泥有机质含量(r=0.593)和全磷含量(r=0.618)成正相关,与水深度(r=-0.636)、水电导率(r=-0.558)、水pH值(r=-0.535)成显著负相关。环境因子影响水甲虫的分布,但人类是最终决定因素,了解水甲虫多样性与环境的关系,有助于揭示生物-环境-人类三者之间的关系,为生态系统和生物多样性的修复和保护提供服务。

城市环境的一大课题——污水处理厂污泥处置浅析

１概况随着我国城市经济的发展和人口的增加，我国水污染日益严重，建设城市污水处理厂已成为治理水污染的不可中缺少的举措．特别是国务院关于淮河、辽河、海河三河限期治理的通知下达后，三河沿岸城市都在按要求建不同规模的污水处理厂，并将其纳入城市环境质量考核的重...