新银盐光度法测定磷酸氢钙中的微量砷

以硝酸银－乙酸－聚忆烯醇－乙醇作为砷化氢吸收液,Ｚｎ－ＫＩ－ＳｎＣｌ２为还原体系的新银盐光度法测定了磷酸氢钼中的微量砷。Ａｓ＾２－含量在０－７．５μｇ／５ｍＬ范围内服从比耳定律。应用于磷酸氢钙样品中Ａｓ呈测定,回收率９６－１０３％,方法检出限为２．８８×１０＾－６ｇ／Ｌ,ＲＳＤ为０．９４－５．５０％,测定结果与标准方法基本一致。     

Seismic gyrotropy as a result of rock-microstructure dissymmetry

Seismic investigations show that rocks exhibit not only anisotropic properties but also gyrotropic ones. Recently, the phenomenological theory has been developed to describe the phenomenon ‘seismic gyrotropy'. The paper gives a possible explanation of the gyrotropic properties of rocks on a microlevel. A gyrotropic model of grainy rock with dissymetry in its microstructure is presented. The model is built on a principle ‘azimuthal turn plus translation'. The mathematical and physical formulations of the problem are discussed. An algorithm is constructed to find the displacements, their first and second derivatives with respect to spatial coordinates as well as stresses inside a grain, an element of the model. Mathematical modelling of elastic-wave propagation in the model considered enabled to demonstrate that the model possesses gyrotropic properties, i.e., it rotates on a polarization vector. Gyration constants are determined.     

Infrared Absorption Intensity Analysis as a New Tool for Investigation of Salt Effect on Proteins

通过观测红外光谱的强度变化研究了在不同温度下盐离子对谷氨酸和三种水溶性蛋白质(细胞色素C、DsbC和DsbC-G49R)的影响. 证实了Onsager反应场理论. 区分并且定义了随温度变化的蛋白质盐效应盐溶过程和解离过程. 同时利用Van't Hoff关系式对实验结果进行线性拟合,获得了蛋白质及其二级结构在上述两个过程中的热力学常数.     

酸性品红褪色光度法直接测定食盐中的碘

在HCl-KBr的介质中,碘酸钾氧化酸性品红褪色的程度与碘酸根含量在一定范围内呈线性关系,从而建立了褪色光度法测定碘的新方法。试验结果表明,酸性品红的最大吸收波长为545nm,碘的含量在0.4—2μg·mL-1范围内时,符合比耳定律,表观摩尔吸光系数为3.7×104L·mol-1·cm-1。用于测定食盐中的碘,结果满意。     

Anti-Hofmeister series properties found for a polymer having a π electron system and acidic protons

Anti-Hofmeister series properties have been found for a polymer (PVA-T) having a π electron system and acidic protons, which were prepared by introducing trimellitic anhydride to poly(vinyl alcohol) (PVA). Aqueous dispersion of PVA-T became clear in the presence of 1 M Na₂SO₄, a typical kosmotrope, due to dissolution of the solid polymer sample, while the turbidity in the presence of 1 M KSCN, a typical chaotrope, hardly changed. Being consistent to the salt effects, PVA-T hydrogel, which was prepared by chemical cross-linking, showed marked swelling in sulfate solutions, whereas the swelling degree was only marginal in thiocyanates.     

Prediction of solubilities of salts,osmotic coefficients and vapor–liquid equilibria for single and mixed solvent electrolyte systems using the LIQUAC model

The electrolyte model LIQUAC has been used up till now to predict osmotic coefficients, mean ion activity coefficients, the vapor–liquid equilibrium (VLE) behavior, the solubility of gases in single and mixed solvent electrolyte systems, and solubilities of salts in aqueous solutions. In this paper, the required expressions for the calculation of salt solubilities not only in aqueous systems, but also in organic solvents and water–solvent electrolyte systems were deduced in detail based on the LIQUAC model with a fixed reference state and thermodynamic relations. Four salts (NaCl, KCl, NH₄Cl and NaF) and two solvent (water and methanol) were selected to test the derived expressions. The results show that the LIQUAC model with a fixed reference state can be used to predict osmotic coefficients, solubilities of salts in aqueous solutions, vapor–liquid equilibria, and the solubilities of salts in water–organic solvent systems with strong electrolytes.     

Bioprocess for solubilization of rock phosphate on starch based medium by Paecilomyces marquandii immobilized on polyurethane foam

Paecilomyces marquandii, a phosphate-solubilizing, starch-utilizing filamentous fungus, was immobilized on polyurethane foam (PUF). The immobilized fungus was applied in a repeated batch (six batches) fermentation process to solubilize Hirapur rock phosphate. The fungus was immobilized on PUF cubes and was used for phosphate solubilization in shake flask repeated batch cultivations. The fungus was also immobilized on PUF sheet and utilized in an airlift bioreactor in a repeated batch process. Maximum soluble phosphate (370 μg/ml) was recorded after third batch with 8 g rock phosphate/l. After 12 days of fermentation, a total production of 1,643 μg phosphate/ml was achieved.     

Modeling rock failure using the numerical manifold method followed by the discontinuous deformation analysis

A complete rock failure process usually involvesopening/sliding of preexisting discontinuities as well as fracturing in intact rock bridges to form persistent failure surfaces and subsequent motions of the generated rock blocksThe recently developed numerical manifold method(NMM)has potential for modelling such a complete failure processHowever,the NMM suffers one limitation,i.e.,unexpectedmaterial domain area change occurs in rotation modellingThis problem can not be easily solved because the rigidbody rotation is not represented explicitly in the NMM.Thediscontinuous deformation analysis(DDA) is specially developed for modelling discrete block systems.The rotationinduced material area change in the DDA modelling canbe avoided conveniently because the rigid body rotation isrepresented in an explicit form.In this paper,a transitiontechnique is proposed and implemented to convert a NMMmodelling to a DDA modelling so as to simulate a completerock failure process entirely by means of the two methods,in which the NMM is adopted to model the early fracturingas well as the transition from continua to discontinua,whilethe DDA is adopted to model the subsequent motion of thegenerated rock blocks.Such a numerical approach also improves the simulation efficiency greatly as compared with acomplete NMM modelling approach.The fracturing of arock slab with pre-existing non-persistent joints located ona slope crest and the induced rockfall process are simulated.The validity of the modelling transition from the NMM tothe DDA is verified and the applicability of the proposed numerical approach is investigated.     

DEM analysis of the effect of joint geometry on the shear behavior of rocks

In order to comprehensively investigate the effect of different joint geometries on the shear behavior of rocks, the Distinct Element Method (DEM) was utilized with a new bond contact model. A series of direct shear tests on coplanar and non-coplanar jointed rocks was simulated using the PFC2D software, which incorporates our bond contact model. Both coplanar jointed rocks with different joint persistence and non-coplanar ones with different joint inclinations were simulated and investigated numerically. The numerical results were compared and discussed with relevant laboratory tests as well as some reported numerical works. The results show that for coplanar jointed rocks, the peak shear stress decreases nonlinearly with the joint persistence, and the failure process can be divided into four stages: elastic shearing phase, crack propagation, failure of rock bridges, and residual phase. For non-coplanar jointed rocks, as the absolute value of the inclination angle of the rock joints increases, its shear strength increases, changing the failure patterns and the length of new fractures between existing cracks. When the absolute value increases from 15° to 30°, the average shear capacity increases the most as 39%, while the shear capacity increases the least as 2.9% when the absolute value changes from 45° to 60°. There is a good consistency of the failure patterns obtained from experiments and numerical tests. All these demonstrate that the DEM can be further applied to rock mechanics and practical rock engineering with confidence in the future.