Microstructure of highly concentrated tomato suspensions on homogenisation and subsequent shearing

The changes in the microstructure of tomato paste suspensions have been investigated during homogenisation and subsequent shearing in suspensions with similar composition, at three tomato paste concentrations 10, 30 and 40%. The suspensions were characterised by the particle size distribution (PSD), volume fraction (ø), and dynamic rheological properties (G′, G″). All suspensions exhibit a solid-like behaviour with G′ > G″. Micrographs indicate that the process of homogenisation creates a smooth network of finer particles, that is easily disrupted by prolonged shearing, giving rise to the formation of densely packed flocs that become clearly oriented in the direction of the shearing. At high concentrations, these changes in the microstructure on homogenisation and subsequent shearing were better reflected by differences in ø than in G′. The rheological behaviour of the suspensions exhibits a power-law dependence on ø, over a large range of PSD and for 0.05 < ø < 0.55. Finally, an experimental equation, including ø and the size of the coarse particles in the surface-weighted PSD, is found to accurately estimate G′ (R² > 99.3%, p < 0.001).     

Aggregation of non-amphiphilic bathophenanthroline in the restricted geometry of Langmuir-Blodgett films with two different matrices

The behavior of binary mixed Langmuir monolayers from the mixture of non-amphiphilic bathophenanthroline (BPH) and behenic acid (BA)/poly(methyl methacrylate) (PMMA) spread on aqueous subphase was investigated on the basis of the analysis of surface pressure-average area per molecule (π-A) isotherms complemented with UV-vis absorption spectroscopy and scanning electron microscopy. In addition, the miscibility of the components in the two investigated mixed systems (BPH/BA and BPH/PMMA) was also tested by using additivity and surface phase rules. The plots of area per molecule versus mole fraction suggest that BPH and BA are immiscible, whereas BPH and PMMA mixtures show non-ideal behavior at low surface pressures and complete miscibility or immiscibility at higher surface pressures. Spectroscopic study reveals that J-type of aggregates is formed in the mixed films. Scanning electron microscopic study supports the presence of aggregates.     

多分散气溶胶凝聚粒子散射特性的数值计算

基于簇团-簇团(Cluster-Cluster Aggregation,CCA)模型,结合气溶胶谱分布函数,模拟了多分散气溶胶凝聚粒子.利用离散偶极子近似方法,数值计算了多分散气溶胶凝聚粒子散射强度的角分布,对比分析了多分散和单分散气溶胶凝聚粒子散射特性的差别,并讨论了散射强度随入射波波长和入射角变化的规律.结果显示:多分散和单分散气溶胶凝聚粒子的散射特性截然不同,凝聚粒子中原始微粒的粒径、入射波长、入射波的入射角等因素都将影响气溶胶粒子的散射特性.多分散凝聚粒子模型更接近实际气溶胶粒子,结果可为全面理解和研究气溶胶粒子散射特性提供参考和有效的计算方法.     

烟稻复种连作对河潮土团聚体的影响及相关因素分析

为明确烟稻复种连作对河潮土团聚体稳定性变化的影响及关键因素,研究了南方不同烟稻复种连作年限的河潮土团聚体分布及其稳定性变化,并采用相关及冗余分析等方法分析了有机质、机械组成等理化指标对土壤团聚体及其稳定性变化的影响。结果表明,在烟稻复种连作5~25年的河潮土中,>5 mm团聚体含量显著升高26.24%~64.41%,0.5~0.25和<0.25 mm团聚体含量分别显著降低19.45%~53.70%和18.99%~45.63%,团聚体重量平均直径和几何平均直径分别显著增加26.17%~57.01%和38.01%~104.33%,而分形维数降低,团聚体稳定性增加。相关及冗余分析表明,有机质、粗砂粒、中砂粒、细粉粒和黏粒是引起团聚体分布的关键指标,>5 mm、<0.25 mm及0.5~0.25 mm团聚体是引起团聚体稳定性变化的关键指标;烟稻复种连作引起河潮土有机质、粗砂粒、中砂粒、细粉粒和黏粒含量变化,主要导致>5 mm的团聚体的形成或破坏,进而导致团聚体分布及稳定性变化。因此,烟稻复种连作5~25年有利于改善河潮土结构和改良土壤质量。     

Surface Properties of Heat‐Induced Soluble Soy Protein Aggregates of Different Molecular Masses

Suspensions (2% and 5%, w/v) of soy protein isolate (SPI) were heated at 80, 90, or 100 °C for different time periods to produce soluble aggregates of different molecular sizes to investigate the relationship between particle size and surface properties (emulsions and foams). Soluble aggregates generated in these model systems were characterized by gel permeation chromatography and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. Heat treatment increased surface hydrophobicity, induced SPI aggregation via hydrophobic interaction and disulfide bonds, and formed soluble aggregates of different sizes. Heating of 5% SPI always promoted large‐size aggregate (LA; >1000 kDa) formation irrespective of temperature, whereas the aggregate size distribution in 2% SPI was temperature dependent: the LA fraction progressively rose with temperature (80→90→100 °C), corresponding to the attenuation of medium‐size aggregates (MA; 670 to 1000 kDa) initially abundant at 80 °C. Heated SPI with abundant LA (>50%) promoted foam stability. LA also exhibited excellent emulsifying activity and stabilized emulsions by promoting the formation of small oil droplets covered with a thick interfacial protein layer. However, despite a similar influence on emulsion stability, MA enhanced foaming capacity but were less capable of stabilizing emulsions than LA. The functionality variation between heated SPI samples is clearly related to the distribution of aggregates that differ in molecular size and surface activity. The findings may encourage further research to develop functional SPI aggregates for various commercial applications.     

Fluid motion around and through a porous cylinder

The flow-field and solute transport through and around a porous cylinder is investigated numerically. The range of Reynolds number (based on the cylinder diameter and the uniform sinking rate of the cylinder) considered here is between 1 and 40 with Darcy number (Da) in the range 10^-6?Da?1.5 and porosity in the range 0.629?ε?0.999. The motivation of the present study is the application of flow through porous cylinder extensively applied in nuclear biological chemical filters as well as reduction of carbon fines in filtered water. The influence of Da on the drag coefficient, separation angle, recirculation length, streamline and vorticity pattern are investigated. The drag ratio, defined as the ratio of drag coefficient of porous cylinder to that of solid cylinder, is found to approach zero from unity as Da is increased from 10^-6 to 1.5. The separation point shifts towards the rear stagnation point as Da is increased. The time evolution of the solutal field at different Reynolds number and Darcy number is presented. A long slender concentration plume is found to evolve from the cylinder with decreasing concentration at the outer edge.     

再生骨料混凝土基本特性的研究思路探讨

本文分析了再生骨料混凝土和天然骨料混凝土基本特性的差异 ,并结合我国实际情况 ,探讨了再生骨料和再生骨料混凝土改性的途径和方法 ,并提出了再生骨料混凝土工程特性试验的研究内容和方法。     

混合型集料优质轻混凝土的微观结构

本项研究用混合型集料配制出了表观密度等级为1800,抗压强度等级为CL50的优质轻混凝土。通过试验及检测分析,所研制的轻混凝土具有低容重、高密实度、高强度、抗渗等优良的理化性能。研究中采用X射线衍射(XRD)、扫描电镜(SEM)、差热(DTA)等手段,对所配混合型集料优质轻混凝土微观结构的具体类型及转化,微观结构与各项理化性能之间的关系,进行了全面的研究和测定。从微观的角度解释了其优良性能的根源,为进一步优化轻混凝土的理化性能提供了依据。     

Solubilization of methanol and triglycerides: Unsaturated long-chain fatty alcohol/medium-chain alkanol mixed amphiphile systems

This work examines the suitability of unsaturated C₁₈ fatty alcohol/1-alkanol mixed amphiphile systems as solubility enhancers for methanol in triglyceride solutions. Four fatty alcohols (all-cis monoene, diene and triene, and all-trans diene) and five alkanols (C₄−C₁₂) were investigated. Effects of the degree of unsaturation and configuration of the double bonds in the fatty alcohol tailgroup and the chainlength of the alkanol tailgroup were examined. Ternary equilibrium diagrams showed that addition of fatty alcohol/alkanol amphiphiles dramatically affect miscibility between methanol and triglyceride. Solubility, kinematic and relative viscosity, and refractive index data were analyzed to determine mechanisms responsible for the apparent solubilization effects. Under most experimental conditions, formation of large micellar aggregates of amphiphiles was unlikely, and the results were consistent with those expected for co-solvency. However, some viscosity and refractive index data showed that formation of large methanol-in-amphiphile aggregates resembling a nonaqueous microemulsion was feasible, but under limited conditions.