Effects of Pellet Characteristics on L-Lactic Acid Fermentation by R. oryzae: Pellet Morphology,Diameter, Density,and Interior Structure

The effects of pellet morphology, diameter, density, and interior structure on L-lactic acid fermentation by Rhizopus oryzae were characterized for different inoculum sizes and concentrations of peptone and CaCO₃. Inoculum size was the most important factor determining pellet formation and diameter. The diameter decreased with increasing inoculum size, and larger pellets were observed for lower inoculum sizes. Peptone concentration had the greatest effect on pellet density, which increased with increasing peptone concentration. L-lactic acid production depended heavily on pellet density but not on pellet diameter. Low-density pellets formed easily under conditions of low peptone concentration and often had a relatively hollow structure, with a thin condensed layer surrounding the pellet and an extraordinarily loose biomass or hollow center. As expected, this structure greatly decreased production. The production of L-lactic acid increased until the density reached a certain level (50–60 kg/m³), in which the compact part was distributed homogeneously in the thick outer layer of the pellet and loose in the central layer. Homogeneously structured, denser pellets had limited mass transfer, causing a lower overall turnover rate. However, the interior structure remained nearly constant throughout all fermentation phases for pellets with the same density. CaCO₃ concentration only had a slight influence on pellet diameter and density, probably because it increases spore germination and filamentous hypha extension. This work also provides a new analysis method to quantify the interior structure of pellets, thus giving insight into pellet structure and its relationship with productivity.     

Plasma-Induced Synthesis of CuO Nanofibers and ZnO Nanoflowers in Water

Fiber-shaped cupric oxide (CuO) nanoparticles and flower-shaped ZnO nanoparticles were facilely synthesized by plasma-induced technique directly from copper and zinc electrode pair in water, respectively. The phase composition, morphologies and optical property of nanoparticles have been investigated by energy dispersive X-ray analysis, X-ray powder diffraction, transmission electron microscopy and UV–vis. The in situ analysis by an optical emission spectroscopy clarified the formation mechanism. Plasma was generated from the discharge between a metal electrode pair in water by a pulse direct current power. CuO and ZnO nanoparticles were synthesized via almost the same formation mechanism, which were prepared via the rapid energetic radicals’ bombardment to electrodes’ surface, atom vapour diffusion, plasma expansion, solution medium condensation, and in situ oxygen reaction and further growth. This novel plasma-induced technique will become a potential application in nanomaterials synthesis.     

Facile synthesis of 4-vinylpyridine-based hydrogels via laser-ignited frontal polymerization and their performance on ion removal

We report herein the fabrication of poly(AAM-co-4VP) hydrogels (AAM?=?acrylamide, 4VP?=?4-vinylpyridine) by using laser-ignited frontal polymerization (LIFP) in an easy and rapid way. The appropriate amounts of AAM, 4VP, γ-methacryloxypropyltrimethoxysilane-modified nanosilica, and couple redox initiator of ammonium persulfate/N,N,N′,N′-tetramethylethylenediamine were mixed together in the presence of dimethylsulfoxide as solvent. LIFP was initiated by heating the upper side of the mixture with the laser. Once initiated, no further energy or treatment was required for the following polymerization to occur. A variety of features for the preparation of hydrogels, such as the initiator concentration and the ratio of different monomers, were thoroughly investigated. The morphology and swelling behavior of hydrogels were investigated. For comparison, the hydrogels prepared via traditional thermal frontal polymerization were also presented and discussed. Furthermore, the hydrogels possess absorption capacity towards copper ions, which can be applied to remove heavy metals.     

键合型铕-十一烯酸-硅橡胶复合材料的合成及其荧光性能

以铕-十一烯酸配合物和含氢硅油为原料,在铂催化剂作用下制备稀土有机硅加成产物。对产物进行红外光谱和核磁共振分析。结果表明,配合物键接在有机硅高分子主链上,加成产物为一种键合型的铕-十一烯酸-硅橡胶复合材料。荧光光谱分析确定复合材料的最佳激发波长为393 nm;最强发射波长为616 nm,为铕离子的特征发射。同时,随着铕离子浓度的增大,复合材料没有荧光猝灭现象。     

Band gap of carbon nanotubes under combined uniaxial–torsional strain

Within tight-binding model, the band gaps of armchair and zigzag carbon nanotubes (CNTs) under both uniaxial tensile and torsional strains have been studied. It is found that the changes in band gaps of CNTs depend strongly on the strain type. The torsional strain can induce a band gap for armchair CNTs, but it has little effect on band gap of the zigzag CNTs. While the tensile strain has great effect on band gap of zigzag CNTs, but it has no effect on that of the armchair CNTs. More importantly, when both the tensile and torsional strains are simultaneously applied to the CNTs, the band gap changes of armchair CNTs are not equal to a simple sum over those induced separately by uniaxial tensile and torsional strains. There exists a cooperative effect between two kinds of strains on band gap changes of armchair CNTs. But for zigzag CNTs, the cooperative effect was not found. Analytical expressions for the band gaps of armchair and zigzag CNTs under combined uniaxial–torsional strains have been derived, which agree well with the numerical results.     

2010年研究生数学建模竞赛A题综述

第七届全国研究生数学建模竞赛A题是生物信息学中的一个急需解决的问题.虽然有关问题的研究已经经历了十多年,但由于问题的复杂性,人们的认识还很局限,基本的结论大多还以定性的为主,定量的探讨正方兴未艾.对参赛队员来讲解决该问题是一个极大的挑战.研究生们在讨论该问题时,大多直接进行分类.然而对于一个小样本的学习问题,显然这样做是行不通的.所以问题的关键是从数学和生物学角度减少用于分类的特征数目.同时,对于获取的基因标签,需要从临床上或生物学角度找到验证.该问题的求解过程引导研究生们从数学建模走向解决实际问题.     

Generalized fractional L��vy random fields on Gel��fand triple: A white noise approach

In this paper, under the first-order moment condition of the infinitely divisible distribution on Gel’fand triple, we use Riesz potential to construct fractional Lévy random fields on Gel’fand triple by white noise approach. We investigate the distribution and sample properties of isotropic and anisotropic fractional Lévy random fields, respectively.     

Experimental study on the smoke temperature evolution in a polyethylene (PE)-lined compartment on fire

Smoke temperature evolution in the upper layer of compartment fire, which is critical for the prediction of potential flashover, was experimentally investigated in a real building. Three-millimeter polyethylene (PE) slabs attached on the internal walls were employed as the lining material to address the effect of the melting and combustion of the lining material on the smoke temperature. A corner gasoline pool fire was utilized as the fire source. Two thermocouple trees, mounted vertically at the center and the open door, and a high-definition camera were utilized to record the smoke temperature history and experimental video. Meanwhile, some furniture was loaded to study its enhancement feature on fire intensity. Heat release rates (HRRs) at different stages were analyzed based on MQH method (McCaffrey, Quintiere and Harkleroad) and pool fire theory. Smoke temperature was estimated through an improved MQH correlation considering the melting of the PE slabs and an empirical model, BFD curve (Barnett in Fire Saf J 37: 437–463, 2002) combined. The results show that both the maximum HRR and smoke temperature, 925.91 kW and 491.7 °C, are lower than the critical values of flashover. The PE lining greatly intensifies the fire power and the resulting smoke temperature compared with the ones in noncombustible wall scenario. Combustion of the molten PE flowing down from the walls would lead to a secondary peak in smoke temperature curve, which is rarely considered in previous work.

     

Thermal hazard assessment and ranking for organic peroxides using quantitative structure–property relationship approaches

Journal of Thermal Analysis and Calorimetry - Chemical reactivity hazards of organic peroxides are major concerns of the chemical industry due to many serious incidents every year. Thermal hazard...     

Recent progress in measurements of oscillatory forces and liquid properties under confinement

The present review paper focuses on direct measurements of oscillatory forces. Beside the surface forces apparatus (SFA), atomic force microscopy (AFM) has emerged as the most commonly used technique to measure surface forces. Recent instrumental advances of both methods are highlighted in the review. Different systems, showing oscillatory forces are classified. Principle distinction is made between 1-component liquids (water, organic liquids and liquid crystals), pseudo 1-component liquids (ionic liquids and microemulsions) and 2-component liquids (dispersions containing polyelectrolytes, micelles or nanoparticles). In the last few years, the oscillatory force studies address particle characterisation, synergistic effects in multicomponent systems, the introduction of ‘switchable’ forces, and resolving liquid properties under confinement. Last but not least, the ability of AFM and SFA to measure oscillatory forces is discussed.