Interaction of inositol phosphate with calcite

The interaction of myo-inositol hexaphosphate with calcite was studied to evaluate the adsorption mechanisms and the electrochemical modifications induced by interaction of a molecule at such a high-charge density. In addition to quantitative information through the construction of adsorption isotherms, FT-IR and Laser Doppler Velocimetry - Photon Correlation Spectroscopy (LDV-PCS) were employed to investigate the nature of the adsorbent-adsorbate bonds and to determine the electrophoretic mobility and size of the particles before and after sorption. The experiments were also run with orthophosphate (Pi) for comparison. The amount of sorbed P increased to reach a plateau at 17.8 mol m^-2 for inositol hexaphosphate (IHP) while for Pi rose 1.4 mol m^-2 but at C_e > 610^-4 M it had a sharp increase reaching 155 mol m^-2. As expected, for Pi, adsorption predominated up Ce 610^-4 M by covering about 20% of total surface. The adsorption occurred at sites that behaved as nucleus of formation of the clustering of Ca- and PO₄-ions with the ending formation of calcium phosphate precipitates at C_e higher than 610^-4 M. The reaction of inositol hexaphosphate with calcite involves, besides adsorption, precipitation of Ca salts and hence calcite dissolution also at the lowest added IHP concentrations, accounting for the large amount retained by calcite. Sorption of IHP on calcite caused aggregation of particles at low concentrations followed by an increase of their negative charge and hence re-dispersion at higher concentrations. These results indicate a great IHP-fixing capacity of calcite that can affect its accumulation in soils and P bioavailability, and a considerable change of calcite electrochemical properties and particle size distribution that can modify aggregate stability.     

采用复合分散剂制备高表观密度聚氯乙烯树脂

介绍了高醇解度、高粘度聚乙烯醇 6 35与分散能力较强的其它分散剂按一定配比复合后的使用情况 ,结果表明 :采用复合分散剂 ,可在保持PVC树脂具有适当孔隙率的前提下 ,提高其表观密度 ;采用KH2 0 /6 0SH5 0复合分散剂在 10L釜中制得的PVC树脂表观密度约为 0 .4 6g/mL ;采用 6 35 /B72或 6 35 /F5 0复合分散剂制得PVC树脂的表观密度可比采用通用分散体系提高 10 %～ 15 % ,且水油比减少 ,增塑剂吸收量提高。分析了影响树脂表观密度和颗粒形态的主要因素     

流行性出血热病毒在地鼠肾细胞中增殖动态的形态学及形态发生学研究

用普通电镜及免疫电镜对流行性出血热病毒(EHFV)不同毒株感染地鼠肾细胞(GHKC)的形态及形态发生学特点、其特征性包含体的形态及感染细胞超微结构的改变,以及感染后不同天数的病毒增殖动态进行了观察。     

PARTICLE FLOW PATTERNS IN THE RISER AND DOWNER OF CIRCULATING FLUIDIZED BED

This paper presents an experimental study on the flow patterns of FCC particles in a 140 mm ID Circulating Fluidized Bed with concurrent upflow and downflow gas-solid suspension. Based on the distribution of local particle velocity and particle concentration measured by a Fiber-Optical Probe Laser Doppler Velocimeter and a Fiber Optical Probe System respectively, the different flow patterns of local particls concentration, local particle velocity, local particle fluctuating velocity and sectionally average particle velocity in concurrent upflow and downflow gas-solid system have been investigated. It is found that the particle flow in the concurrent downflow is much more uniform radially than that in the concurrent upflow riser. The investigation of flow patterns in different flow systems is of significance to the development of a new gas-solid reactor.     

Development of the meshless finite volume particle method with exact and efficient calculation of interparticle area

The Finite Volume Particle Method (FVPM) is a meshless method based on a definition of interparticle area which is closely analogous to cell face area in the classical finite volume method. In previous work, the interparticle area has been computed by numerical integration, which is a source of error and is extremely expensive. We show that if the particle weight or kernel function is defined as a discontinuous top-hat function, the particle interaction vectors may be evaluated exactly and efficiently. The new formulation reduces overall computational time by a factor between 6.4 and 8.2. In numerical experiments on a viscous flow with an analytical solution, the method converges under all conditions. Significantly, in contrast with standard FVPM and SPH, error depends on particle size but not on particle overlap (as long as the computational domain is completely covered by particles). The new method is shown to be superior to standard FVPM for shock tube flow and inviscid steady transonic flow. In benchmarking on a viscous multiphase flow application, FVPM with exact interparticle area is shown to be competitive with a mesh-based volume-of-fluid solver in terms of computational time required to resolve the structure of an interface.     

An analysis method for atomistic abrasion simulations featuring rough surfaces and multiple abrasive particles

We present a molecular dynamics (MD) model system to quantitatively study nanoscopic wear of rough surfaces under two-body and three-body contact conditions with multiple abrasive particles. We describe how to generate a surface with a pseudo-random Gaussian topography which is periodically replicable, and we discuss the constraints on the abrasive particles that lead to certain wear conditions. We propose a post-processing scheme which, based on advection velocity, dynamically identifies the atoms in the simulation as either part of a wear particle, the substrate, or the sheared zone in-between. This scheme is then justified from a crystallographic order point of view. We apply a distance-based contact zone identification scheme and outline a clustering algorithm which can associate each contact atom with the abrasive particle causing the respective contact zone. Finally, we show how the knowledge of each atom’s zone affiliation and a time-resolved evaluation of the substrate topography leads to a break-down of the asperity volume reduction into its components: the pit fill-up volume, the individual wear particles, the shear zone, and the sub-surface substrate compression. As an example, we analyze the time and pressure dependence of the wear volume contributions for two-body and three-body wear processes of a rough iron surface with rigid spherical and cubic abrasive particles.     

粒径对膨胀土无荷膨胀率的影响研究

为了研究粒径大小对重塑土无荷膨胀率试验结果的影响,在符合现有规范的试验条件下,将某地基泥岩碾碎成1~2 mm、0.1~1 mm、0.1 mm的三种不同粒径,进行不同比例组合搭配的重塑土无荷膨胀率试验。试验结果表明:不同粒径大小的膨胀土样的无荷膨胀率试验结果有很大差异,并且不同粒径组合下的无荷膨胀率试验结果呈正态分布趋势,且峰值处的无荷膨胀率值为该重塑土稳定、可靠的无荷膨胀率值,无荷膨胀率试验结果接近峰值处无荷膨胀率值的粒径级配为该重塑土的最佳级配。经过分析得到使重塑土无荷膨胀率结果稳定、可靠的粒径级配是1~2 mm、0.1~1 mm、0.1 mm的土粒质量比为0∶100∶0,即使重塑土无荷膨胀率试验结果稳定可靠的粒径范围为0.1~1 mm。在该粒径范围内的重塑土无荷膨胀率试验结果最为真实、准确。     

Reactive rock phosphate fertilizers and soil testing for phosphorus: The effect of particle size of the rock phosphate

North Carolina rock phosphate (NCRP) (highly carbonate—substituted apatite) was ground to produce three samples with different particle size distributions. The effectiveness of these fertilizers was compared with the effectiveness of superphosphate in a field experiment and three glasshouse experiments using lateritic soils from south-western Australia. Non-reactive Queensland rock phosphate (low carbonate-substituted apatite from the Duchess deposit) was also used in the pot experiments. Bicarbonate-soluble phosphorus extracted from the soil is widely used in Western Australia to predict plant yields from previously-applied fertilizer dressings. For both field and pot experiments bicarbonate-extractable phosphorus (soil test value) was measured and related to subsequent plant yields.As calculated from the initial slope of the relationship between yield and the level of P applied, finely powdered NCRP was about 5–32% as effective as freshly-applied superphosphate in the year of application and also for two years after application in the field experiment, and for two successive crops in the three pot experiments. For both field and pot experiments, finely powdered NCRP, was at best, 1.5–2.0 times as effective as granular NCRP. Relative to freshly-applied superphosphate, the effectiveness of rock phosphates usually decreased with increasing level of application.For each of the crops in the field experiment, the relationships between yield and phosphorus content of plants (i.e. internal efficiency curves) were similar for all fertilizers. Thus the low effectiveness of the rock phosphates relative to superphosphate was solely due to much less phosphorus being taken up by plants. By contrast, in the pot experiments internal efficiency curves differed for different fertilizers. This is attributed to differences in the rate of phosphorus uptake by plant roots during the early stages of plant growth.For both field and pot experiments, soil test calibrations (the relationship between yield and soil test value) differed for rock phosphates and superphosphate. For superphosphate, soil test calibrations also differed for the three different years after the initial application of this fertilizer in the field experiment. For the second crop in the pot experiment, soil test calibrations differed for superphosphate applied at different times (before the first and the second crop). These results point out the difficulty of applying soil testing procedures to soils that have experienced different histories of fertilizer application.     

Measurement of the particle movement in the fountain region of a Wurster type bed

A non-intrusive technique to follow single particles in the fountain region of a spouted bed with draft tube, the Wurster coater, is developed and tested. Compared to other techniques found in literature, the measurement technique presented here is easy to handle, inexpensive and suitable for particles with a diameter down to 500 μm. The measurements are performed in a laboratory scale Wurster bed constructed of Plexiglas to allow optical access to the flow. A small quantity of the particles in the bed are marked with fluorescence. A UV lamp is used to excite the fluorescence and the marked particles are followed with a high-speed video camera equipped with an optical filter. A single marked particle in the fountain can be followed in 5-30 images in sequence at a frame rate of 125 fps. The particle position and velocity are calculated. The distribution of the particle trajectories maximum height is studied for different particle loading, jet air velocity and position of the Wurster tube. The technique can be used for the characterization of differences in process dynamics due to different operating conditions.     

Particle-Substrate Collisions, Particle Rebound and Removal

Recent progress in particle capture and rebound and its effect on the adhesion force is reviewed in this paper. Particles rebound when the incident velocity is greater than a characteristic critical velocity. Lower impaction velocity particles experience elastic and plastic deformation. Recent models for particle rebound and capture are discussed and evaluated in terms of their restrictive assumptions and results. Recent experimental data of particle rebound and capture is also discussed, as is the hydrodynamic removal of captured particles. The removal of particles occurs when the applied hydrodynamic removal force overcomes the adhesion force. The effect of adhesion-induced deformation on the removal of particles is introduced and discussed.