酸雨胁迫及稀土农用条件下菠菜及其土壤中稀土元素的赋存

利用盆栽实验研究了酸雨胁迫、稀土农用条件下 ,菠菜及其土壤中稀土元素的含量及分布特征。结果表明 :菠菜地上部分的REE含量为 0 .5 2 7～ 0 .696μg·g- 1 之间 ,地下部 2 .668～ 3 .0 0 3 μg·g- 1 。土壤 2 2 9.0 9～ 2 5 0 .3 μg·g- 1 。酸雨明显地影响作物对REE的吸收和利用 ,酸度越大 ,影响越明显。随着酸雨酸度的增大、植株体内、土壤中的REE受淋洗的作用加强而表现出REE的总量随着pH的减小而逐渐减少。施用稀土后 ,植株的地上或地下部分及其土壤中的REE含量均与对照的土壤中的REE分配模式基本相同 ,遵循稀土元素分布丰度的奇偶 (Oddo Harkins)规则、轻稀土富集 ,Eu弱负异常 ,富铈配分型 ,表明稀土元素仍然主要来自土壤并受其影响。     

低温低内应力化学镀镍工艺的研究

化学镀广泛应用于非金属的电镀、电铸前的施加导电层。化学镀沉积层质量与其在零件上的附着力有着密切的关系 ,重视对化学镀沉积层内应力的研究 ,开发一个低温、低内应力的化学镀镍工艺 ,对于化学镀沉积层的推广应用有着十分重要的意义。本文采用正交实验方法对低温、低内应力化学镀镍工艺进行了系统研究 ,开发出了一个低温、低内应力的化学镀镍工艺。在实验过程中发现沉积层内应力同其在零件上的结合力具有密切关系并对其进行了初步探讨。1　实验方法1 1　正交实验根据探索性实验结果分析 ,影响化学镀镍层内应力σ和沉积层速率ｒ的主要因…     

Determination of Total Reduced Thiol Levels in Plasma Using a Bromide Substituted Quinone

The exploitation of 2‐bromo‐1,4‐naphthoquinone (NQBr) as a selective redox label for the determination of reduced thiol functionalities (RSH) has been investigated. The system is selective for RSH functionality, giving distinct voltammetric signals for glutathione and cysteine but can also be adapted for broad spectrum thiol detection. Ion chromatographic protocols based on conductimetric detection enable total RSH analysis (protein and monomolecular moieties) within human plasma. Bromide released through the reaction can be easily quantified and integrated within normal IC measurements. The efficacy of the approach has been assessed and the response validated through comparison with the standard colorimetric technique.     

Shear flow experiments in an assembly of gel beads and modelling of bingham behavior

In this paper, we present a rheological study of a compact layer of highly swollen gel beads. The flow regimes of these systems are modelled by an elastic sinusoid moving in a Newtonian fluid. This model predicts a yield stress varying with the square root of the elastic modulus of the gel bead. The slope at the origin (at zero velocity) of the flow curve is expected to depend only on geometrical parameters and on the solvent viscosity. The experimental data are in qualitative agreement with the theoretical predictions.     

The relationship between the linear (oscillatory) and nonlinear (steady-state) flow properties of a series of polymer and colloidal systems

The Cox-Merz empirical relationship between the linear (oscillatory) and nonlinear (steady-state) viscosities has been shown to be valid for many polymeric systems. Here, we present an equivalent expression to relate the linear (G) and nonlinear (N ₁) elastic properties of viscoelastic systems. Like the Cox-Merz relationship, it uses a combination of elastic and viscous parameters. The modified form of the storage modulus is then equivalent to the Cox-Merz complex viscosity. It can be used to correlate with (half) the normal force at numerically equal circular frequency and shear rate, respectively.This new expression and the Cox-Merz rule are tested for a range of polymeric and colloidal systems. It is found that both expression work for the polymeric systems considered, but fail for the colloidal systems. In the latter, the steady state values of viscosity and elasticity are consistently low, and replacing them by the complex viscosity and our new elastic expression only makes matters worse.For polymer systems, we suggest this is a general but not universal observation, since we are aware of exceptions to the rule that polymeric systems obey the Cox-Merz rule for viscosity and our rule for elasticity. For colloidal systems we find that neither rule is obeyed for any of our systems.     

A New Criterion for Brittle-Ductile Transition of Polymer Blends

The T_c criterion was first used by S. Wu for characterizing the brittleductile (B-D) transition of N6/EPDM blends. But in this paper, a new criterion which is based on the stress analysis of blends is proposed to characterize the B-D transitions of blends, namely, A criterionV_(fc) and d_c are the critical volume fractions and particle size of dispersed particles in blends, respectively. For given blends, A is independent of the morphology of dispersed phase and is only the characteristic parameter of matrix. The B-D transitions of different blends, including polar N6/EPDM blends, nonpolar PP/EPDM blends and PE/CaCO_3 composites, were manipulated with A criterion and satisfactory results were obtained. In addition, a new master curve for the impact strength of PP/EPDM blends versus V_f~2/d was obtained. The results showed that A criterion is more suitable than T_c criterion for characterizing the B-D transition of blends.     

ELECTRORHEOLOGICAL PROPERTIES OF POLYANILINE/PUMICE COMPOSITE SUSPENSIONS

Electrorheological （ER） properties of polyaniline （PAni）, pumice and polyaniline/pumice composites （PAPC） were investigated. Polyaniline and PAni/pumice composite were prepared by oxidative polymerization. PAni/pumice particlesbased ER suspensions were prepared in silicone oil （SO）, and their ER behavior was investigated as a function of shear rate, electric field strength, concentration and temperature. Sedimentation stabilities of suspensions were determined. It has been found that ER activity of all the suspensions increases with increasing electric field strength, concentration and decreasing shear rate. It has shown that the suspensions have a typical shear thinning non-Newtonian viscoelastic behavior. Yield stress of composite suspensions increased linearly with increasing applied electric field strength and with concentrations of the particles. The effect of high temperature on ER activity of purrfice/silicone oil systems was also investigated.     

Quantitative evaluation of stress distribution in bulk polymer samples through the comparison of mechanical behaviors between giant single‐crystal and semicrystalline samples of poly(trans‐1,4‐diethyl muconate)

The Raman shift and crystallite modulus were measured under the application of tensile force for a giant single crystal and a series of uniaxially oriented semicrystalline samples of poly(trans‐1,4‐diethyl muconate) (polyEMU). The apparent Raman shift factor α^app or a vibrational frequency shift per 1 GPa tensile stress was higher for the semicrystalline samples with lower crystallinity or lower bulk modulus. The apparent crystallite modulus E or Young's modulus along the chain axis in the crystalline region was not constant but varied remarkably between the giant single crystal and semicrystalline samples. A systematic change in α^app and E among the polyEMU samples with different preparation history could be interpreted quantitatively on the basis of a mechanical series parallel model consisting of crystalline and amorphous phases. The origin of different E and α^app was speculated to be a stress concentration on the taut‐tie chain contained as a parallel crystalline component in the mechanical model. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 444–453, 2003     

Investigation of Cd(II), Pb(II) and Cu(I) complexation by glutathione and its component amino acids by ESI-MS and size exclusion chromatography coupled to ICP-MS and ESI-MS

The elucidation of structures of glutathione (GSH) complexes play an important role in the fundamental understanding of biochemical pathways of metal ion deactivation in plants. This article attempts to feature key studies for stoichiometry of metal complexes with glutathione and its constituent amino acids to obtain a better understanding of the different metal affinities of the complexation sites of glutathione. The SEC-ICP-MS experiments have indicated that oxidation process of glutathione was accelerated by metal ion presence in following order Cu⁺, Pb²⁺ and Cd²⁺. The redox activity of metal ions was confirmed by ESI-MS experiments, which allowed to observe formation of glutathione disulphide (GSSG) in time. The stoichiometry of Cd²⁺, Cu⁺ and Pb²⁺ complexes with GSH was defined by observing the isotope pattern of investigated metals and hydrogen loss or transfer during binding. The complexes with metal bound to sulphur of 1:1 and 1:2 stoichiometry were found in case of cadmium and lead. The number of hydrogen atoms lost during metal binding and the SEC-ESI-MS results allowed to elucidate that copper is bound by GSSG in ratio 1:1 and 1:2. Additionally, size exclusion chromatography coupled to electrospray MS allowed to differentiate more stable complexes from weak ones that could be created in the gas phase.     

The effects of alternative stress on the cell membrane deformability of chrysanthemum callus cells

The effects of alternative stress, which was generated through a strong sound field apparatus set up in our lab, on cultured chrysanthemum callus cells were studied. Meanwhile we measured the deformability of chrysanthemum cell membranes and studied the influence of the cytoskeleton after the treatment of colchicine using micropipette aspiration technique. Based on our experimental results, we found that the deformability of cell membrane decreased in stress condition. However, the effect disappeared after the treatment of cytochalasin. Therefore, we thought that the reason on the deformability of cells decreasing was the microfilament rearranging and consequently the cells becoming more rigid under the alternative stress.