P_(507)萃取分离Gd、Tb、Dy三出口工艺及多元稀土萃取分离数学模拟的研究

溶剂分馏萃取是分离、提纯、富集物质的有效方法之一，由于它具有分离效果好，易于操作等优点。因此，在稀土萃取分离工艺中得到了广泛的应用。但是，每个分馏萃取工艺只能分离两个组份，若要分离所有稀土元素，流程较长。为改进生产，本工作提出了一种三出口萃取分离工艺流程。这种工艺流程可视为由两个萃取段和两个洗涤段组成，由于在两个洗涤段中，两相稀土浓度较高、稀土交换量较大，故可使级数减少。采用此工艺流程进行了P_(507)萃取分离Gd、Tb、Dy三组元素的串级模拟实验，得到了纯度大于99.99％的La－Gd，纯度大于99.8％的Dy－Lu和含量高于65％的Tb_4O_2富集物。Tb的收率大于95％。串级总级数为38级。通过对P_(507)萃取实际体系中稀土元素行为的研究，建立了多元体系中稀土在两相分配的经验模型。Z＝C_1H~(C2)×T~(C_3)e~(c_4X(Tb)+C_5X(Dy))和具有一定物理意义的半热力学半经验模型。YT=(Z/H)~3[Σ from i=1 to m of CiXi + Co]根据氨化P_(507)萃取工艺中稀土总浓度在两相的分布规律，提出了一种适合氨化P_(507)萃取分离多元混合稀土工艺的串级计算方法，并用FORTRAN语言编写 了计算程序。使用自编的计算程序进行了氨化P_(507)萃取分离Gd、Tb、Dy三出口工艺的串级模拟计算，计算结果与实验值基本一致。同时，对文献中报导的中间某级开设出口的一分三工艺也进行了串级计算，根据计算结果讨论了两种工艺的优缺点。对恒定混合萃取比的多元稀土萃取分离工艺，进行了在不同串级条件下分界元素在各级的积累及易萃组份和难萃取份的有效分离系数在各级变化规律的计算。结果表明，有效分离系数在级体中出现一极小值β~*，并且β~*值的大小与其出现在级体中的位置随条件不同而改变。对同一萃取体系，当出口产品较纯时，用线性回归分析法关联计算数据得到了β~*与出口产品组成和总萃取比的经验关系式，在萃取段有（A、B与C分离的工艺）β~*/β_B~C=C1+C2EM+C_3ln (A1)/(B1)引入有效分离系数后，进行了环烷酸萃取分离钇与镧系元素的串级模拟计算，计算结果与实验值基本吻合。

CaS:M (M=Ce~(3+), Dy~(3+), Eu~(2+), Cu)和Cas:Ce~(3+), M (M=Dy~(3+), Cu)的合成及其光致发光和热释发光性质研究

本文研究了Ce~(3+), Dy~(3+), Eu~(3+), Cu离子以及它们的共掺杂在硫化钙基质中的光致发光和热释发光性质，并用顺磁共振方法研究了磷光体中缺陷的性质及其对磷光体光致发光的影响。在CaS:Ce~(3＋)磷光体的稳定性影响因素，并经包膜后稳定性有所提高。计算了新的热释发光峰的陷阱参数。确定了热释发光的动力学级数。在Cas: Dy~(3+)磷光体中，研究了合成条件对磷光体发光性质的影响，讨论了新的热释发光峰的陷阱参数，确定了热释发光的动力学级数。在CaS:Dy~(3+)磷光体中，发现基质对Dy~(3+)离子具有敏化作用，讨论了黄兰比随Dy~(3+)离子浓度变化出现最大值的原因。计算了热释发光峰的陷阱参数，确定了热释发光的动力学级数。在CaS:Ce~(3+)，Dy~(3+)磷光体中，研究了Ce~(3+)离子的发光随Dy~(3+)离子浓度的变化，可能具有Dy~(3+) → Ce~(3+)的能量传递。计算了热释发光峰的陷阱参数，确定了热释发光的动力学级数。在CaS:Cu磷光体中，确定了不同Cu~+离子格位所产生的发射峰。根据磷光体中缺陷的转化过程解释了光致发光和热释发光性质随Cu离子浓度增加所呈现的规律性变化。通过实验证明磷光体有可能用作紫外剂量材料。本文还首次研究了CaS:Cu磷光体在UV（3bb nm)辐照下，发生Cu~+→Cu~(2+)的光氧化反应，通过EPR实验证明在Cu'_(Ca)→Cu_i~+处发生光氧化反应。在CaS:Ce~(3+),Cu磷光体中，观察到了Cu离子对Ce~(3+)离子的能量传递现象。在CaS:Eu~(2+)光体中，发光强度随Eu~(2+)离子浓度变化，显示浓度猝灭特性。本文还研究了CaS:Ce~(3+), CaS:Dy~(3+), CaS:Cu以及CaS:Ce~(3+), Cu磷光体中缺陷的性质，在CaS:Ce~(3+)中存在V_S~(2+)空位，并根据这一空位的性质，解释了发光光谱，并且选择适当的助熔剂使发光效率提高。在CaS:Dy~(3+)磷光体中，存在V_S~(2+)-V_(Ca)~(2-)空位对；在CaS:Cu和CaS:Ce~(3+), Cu磷光体中，存在V_S~(2+)空位和Cu'_(Ca)缺陷。

Fe-57 Mossbauer spectroscopic and magnetic studies of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Mossbauer spectra for Fe atoms in the series of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds were collected at 4.2 K. The ratio of 14.5 T/mu(B) between the average hyperfine field B-hf and the average Fe magnetic moment mu(Fe)(MS), obtained from our data, in Y3Fe29-xVx is in agreement with that deduced from the RxTy alloys by Gubbens et al. The average Fe magnetic moments mu(Fe)(MS) in these compounds at 4.2 K, deduced from our Mossbauer spectroscopic studies, are in accord with the results of magnetization measurement. The average hyperfine field of the Fe sites for R3Fe29-xVx at 4.2 K increases with increasing values of the rare earth effective spin (g(J) - 1) J, which indicates that there exists a transferred spin polarization induced by the neighboring rare earth atom.

Mossbauer spectroscopy study of Fe-57 in R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

Fe-57 Mossbauer spectra for the Fe atoms in the R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb, Dy; T=V, Cr) compounds were collected at 4.2 K. The analysis of Mossbauer spectra was based on the results of magnetization and neutron powder diffraction measurements. The average Fe magnetic moments at 4.2 K, deduced from our data, are in accord with magnetization measurements. The average hyperfine field of Tb3Fe29-xCrx (x=1.0, 1.5, 2.0, and 3.0) decreases with increasing Cr concentration, which is also in accordance with the variation of the average Fe magnetic moment in the Tb3Fe29-xCrx compounds.

Crystallographic and magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

The crystallographic and intrinsic magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) have been investigated. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Regular anisotropic expansions, mainly along the a- and b-axis rather than along the c-axis, are observed for all the compounds upon hydrogenation. Hydrogenation leads to an increase in Curie temperature. First-order magnetization processes (FOMP) occur in magnetic fields of around 1.5 T and 4.0 T at 4.2 K for Nd3Fe24.5Cr4.5H5.0 and Tb(3)Fc(27.0)Cr(2.0)H(2.8), and around 1.4 T at room temperature for Gd3Fe28.0Cr1.0H4.2 Abnormal crystallographic and magnetic properties of Ce3Fe29-xTxHy suggest that the Ce ion is non-triply ionized.

~(143)Dy和~(141)Dy的β缓发质子衰变与自旋指认

分析了143Dy和141Dy的β缓发质子衰变的数据,对比计算了这两种核的核位能面。从中看到了143Dy的衰变包括有1/2+基态和11/2-同核异能态的两种衰变成分,并且确定了它们的半衰期分别为(6.0±1.5)s和(3.0±0.5)s。同时也测定了141Dy的半衰期为(0.9±0.2)s,并指认了它的自旋宇称为9/2-。

~(140)Tb和~(141)Dy的β缓发质子衰变以及~(143)Dy的自旋宇称

利用40Ca+106Cd融合蒸发反应产生了近质子滴线核140Tb和141Dy,配合氦喷嘴带传输系统采用“质子-γ”符合方法观测了它们的β缓发质子衰变,其中包括半衰期、质子能谱和衰变到第二代子核不同低位态的分支比．通过统计理论拟合提取了140Tb和141Dy的基态自旋宇称分别为7±和9／2±．另一方面,用Woods-Saxon Strutinsky方法计算了这两种核限制组态的势能面,由此得到140Tb和141Dy的基态自旋宇称分别为7+和9／2-．此外用同一方法还计算了143Dy的核势能面,从中看出143Dy存在有自旋宇称为1／2+的基态和一个激发能为198keV的11／2-的同质异能态．该结果与2003年Eur．Phys．J． A16:347-351中的143Dy衰变实验数据相符．

Possible magnetic and antimagnetic rotations in Dy-144

High spin states of Dy-144 have been studied through in-beam gamma-ray spectroscopy by using the reaction Mo-92(Fe-56,2p2n). It has been found that the continuation of the ground-state band forks into three Delta I=2 bands above the 8(+) state. This forking has been attributed to the alignments of pi h(11/2)(2) or nu h(11/2)(-2) configurations with the help of the systematics in neighboring nuclei. Additionally a negative-parity sideband of Delta I=2 cascades has been observed to start from the 5((-)) state and continue to a dipole band above the (13(-)) state through another negative-parity sideband of Delta I=2 cascades in between. These structures have been discussed from the viewpoint of a competition between "Magnetic Rotation" and "Anti-magnetic Rotation" based on a classical particles-plus-rotor model.

Alterations of immune functions induced by 12C6+ion irradiation in mice

Purpose: To estimate the biological risks to the immune system of the type of space radiation, 12C6+, encountered by cosmonauts during long-term travel in space. Materials and methods: The Kun-Ming strain mice were whole-body irradiated by 12C6+ ion with 0, 0.01, 0.05, 0.075, 0.2, 0.3, 0.5, 0.75, 1 or 2 Gy, at a dose rate of 1 Gy/min. At 35 days after irradiation, the thymus and spleen weights were measured, the natural killer (NK) cells activity of spleen was determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT), and the interferon-gamma (IFN-gamma) levels in serum and thymus were detected with enzyme-linked immunosorbent assays (ELISA). Results: The results showed that the thymus weight, IFN-gamma levels in serum and the activity of splenic NK-cells had significantly increased at a dose of 0.05 Gy. With further dose increase, the weight of spleen continued to increase but the weight of thymus, IFN-gamma level and NK-cells activity declined. Conclusions: These results suggest that the dose of 0.05 Gy irradiation has a stimulatory effect on mouse immunity; this effect declined with increasing dose.

Antioxidant N-acetylcysteine attenuates the acute liver injury caused by X-ray in mice

The aim of this study was to evaluate the protective effects of different doses and administration modes of N-acetylcysteine (NAC) against X-ray-induced liver damage in mice. Kun-Ming mice were divided into four groups, each composed of six animals: two control groups and two NAC-treated groups. An acute study was carried out to determine alterations in lipid peroxidation (determined by measuring malondiadehyde (MDA) level), glutathione (GSH) content and superoxide dismutase (SOD) activity (assayed by colorimetric method), and DNA damage (characterized by DNA-single strand break using with comet assay) as well as cell apoptosis (measured by flow cytometry) at 12 h after irradiation. The results showed that there were dose-related decreases in MDA level, DNA damage and cell apoptosis, and dose-dependent increases in GSH content and SOD activity in all NAC-treated groups compared to control groups, indicating that pre-treatment or post-treatment with NAC significantly attenuates the acute liver damage caused by X-ray. In addition, significant positive correlations were observed between MDA level and DNA damage or cell apoptosis, implying that lipid peroxidation plays a major role in X-ray-induced liver injury. The data suggest that NAC exerts its radioprotective effect by counteracting accumulated reactive oxygen species in the liver through its properties as a direct antioxidant and a GSH precursor, when administered before or after X-ray irradiation.

Germ cell loss induced by C-12(6+) ion irradiation in young female mice

The ovaries of Kun-Ming strain mice (3 weeks) were irradiated with different doses of C-12(6+) ion in the Bragg peak or the plateau region. At 10th day after irradiation, ovarian and uterine weights were measured: normal and atretic (identified with the oocyte to be degenerating or absent) primordial, primary and preantral follicles were identified in the largest cross-section of each ovary. Percentage (%) of normal follicles of each developmental stage of oogenesis was calculated. The data showed that compared to controls, there was a dose-related decrease in percentage of normal follicles in each developmental stage. And the weights of ovary and uterus were also reduced with doses of irradiation. Moreover, these effects were much more significant in the Bragg peak region and the region close to the Bragg peak than in the beam's entrance (the plateau region). Radiosensitivity varied in different follicle maturation stages. Primordial follicles, which are thought to be extremely sensitive to ionizing irradiation, were reduced by 86.6%, while primary and preantral follicles reduced only by 72.5% and 61.8% respectively, by exposure with 6 Gy of C-12(6+) ion in the Bragg peak region and the region close to the Bragg peak. The data suggested that due to their optimal depth-dose distribution in the Bragg peak region, heavy ions are ones of the best particles for radiotherapy of tumors located next of vital organs or/and surrounded by normal tissues, especially radiosensitive tissues such as gonads.

beta-delayed proton decays of Tb-140 and Dy-140 as well as the spin and parity of Dy-143

Tb-140 and Dy-141 were produced via fusion evaporation in the reaction Ca-40+Cd-106. Their beta-delayed proton decays were studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of Tb-140 and Dy-141 were extracted as 7(+/-) and 9/2(+/-), respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of Tb-140 and Dy-147 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 was also calculated by using the same method. From the NPES a 1/2(+) ground state and a 11/2(-) isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of Dy-143 reported in Eur. Phys. J., 2003, A16: 347-351.