Separation of pectin methylesterase isoenzymes from tomato fruits using short monolithic columns

One of the main forms of tomato pectin methylesterase (PME; EC 3.1.1.1.1) that is applicable to the food industry was isolated from fresh tomato fruit. The extraction of the PME isoenzymes involved washing the fresh tomato flesh with water in order to remove sugars and than solubilizing the enzymes with a diluted HCl solution at pH 1.6. The extract was then neutralized to pH 7.4 using buffer solution. After filtration, the solution was directly fractioned using Convective Interaction Media (CIM) short monolithic disk column bearing sulfonyl (SO3) groups and using a linear gradient from 0 to 700 mM NaCl. The injection volume was 3 ml and the diameter of the column was 12 mm and length 3 mm. The isolated fractions were monitored for protein content and PME activity. The fraction with the targeted enzyme, which showed NaCl independent activity, was further purified and concentrated by ultrafiltration and finally purified by a second semi-preparative cation-exchange chromatography step using a CIM carboxymethyl (CM) disk monolithic column consisting of two disks and applying a step gradient. From 1 kg of fresh tomato fruits, 7.5 mg of purified PME with molecular mass estimated to be 26 000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was obtained. A fraction with mixed PME and polygalacturonase activity was also obtained. Compared to the published procedures for the isolation and purification of PME from plant materials, this new procedure is much faster and more efficient. The potential application of CIM disk short monolithic columns in the analysis and semi-preparative extraction and isolation of the PME isoenzyme is presented.     

Detection of PAH of molecular weight between 300 and 402 in airborne particulate matter by fused silica capillary GC and GC/MS

Gas chromatography (GC), low-voltage mass spectrometry (LV MS), and gas chromatography/mass spectrometry (GC/MS) have been used for detecting polycyclic aromatic hydrocarbons (PAH) of molecular weight between 300 and 402 in airborne particulate matter. Nearly 200 high molecular PAH separated by fused silica capillary columns could be characterized by their El mass spectra. The lack of reference substances precluded further structure elucidation.     

Micro- and mesoporous silicas synthesized in acidic water-ethanol solution of equimolar catanionic surfactant

Porous silicas with combined micro- and mesoporosity are synthesized in acidic water-ethanol solution of equimolar catanionic mixture, where the mesopores are narrowly and uniformly distributed, and the micropores generate due to the addition of ethanol. To vary the pH value of the synthetic mixture can also change the ratio of micro-/mesopores volume in the resulting samples. Compared with other amorphous silica gels and ordered mesoporous silicas including MCM-41, MCM-48 and SBA-15, these micro- and mesoporous silicas show much improved adsorptive capacity for volatile nitrosamines.     

Structural and physical properties of cobalt nanocluster composite glasses

Composite systems with metallic nanoparticles embedded in dielectrics present peculiar physical properties which are attractive in several application fields. In the case of transition elements, the magnetic properties of the metal clusters embedded in a dielectric matrix mainly depend on the particle size and structure. In this work, silica films containing cobalt atoms were synthesized by RF magnetron co-sputtering deposition technique, with cobalt concentration of a few atomic percent. X-ray diffraction and transmission electron microscopy showed the presence of hcp cobalt nanoclusters in the as-deposited sample with the highest cobalt concentration. After deposition, thermal treatments were performed to promote cobalt compounds or nanoparticle formation. The thermal treatments were able to change the oxidation state of cobalt atoms, as well as the structure of metallic cobalt nanoclusters (from hcp to fcc), their final size depending on both the preparation parameters and the subsequent annealing atmospheres.     

AMS-02超导磁体300K-80K受控冷却系统的工艺流程设计

300K-80K受控冷却系统是AMS-02探测器的低温地面支持设备(CGSE)系统中的重要子系统,其主要作用是实现AMS-02磁体从常温(约300K)到接近液氮温度(约80K)的冷却。对该系统进行了工艺流程设计,在恒温器内设置多个调节阀和温度、压力、流量检测元件,通过自动调节手段控制经该系统冷却后前往磁体的氦气的温度和流量。同时介绍了该系统的组成及低温恒温器、HX1、HX2和HX3的结构和特点。     

Elastic scattering of electrons by benzene

Relative differential cross-sections for the elastic scattering of electrons from benzene have been measured at incident energies 300, 500, 700 and 900eV and for scattering angles between 30° and 120°. The results are discussed and compared with the independent atom model (IAM) calculations. Two different sets of scattering amplitudes for the constituent atoms of benzene were used in these calculations, one obtained from first Born approximation and the other from partial wave analysis of the Dirac equation. Only the static interaction was taken into account in the calculations. The higher the incident energy, the better is the observed agreement between experiment and theory. This indicates that at higher energies, absorption, exchange and polarization effects are not significant as compared to the static interaction and that the IAM satisfactorily predicts the interference of scattering from the individual atoms of C₆H₆.     

On Some Generalizations and Refinements of a Ky Fan Inequality

In this paper, a Ky Fan inequality and an inequality by Wu and Wang [10] will be generalized. Some new and improved refinements of the Ky Fan inequality will be put forward.AMS Subject Classification (2000) 26D15     

Polyethylene Glycol (PEG 300) and Water–Ethanol as Benign Solvent Systems for the Synthesis of a Novel Series of 2-Hydroxynaphthalen-1(4H)-Ones

An improved, clean, simple, and efficient method for the synthesis of new series of 2-hydroxy-4-methylenenaphthalen-1(4H)-one is described. This new process involves a domino Michael addition of various methylene acid compounds with the sodium salt of 1,2-naphthoquinone-4-sulfonate either in basic (tBuOK) polyethylene glycol (PEG300) at room temperature or in a basic (NaOH) water–ethanol medium at 40 °C by a crushing in a mortar or a traditional heating.     

HL-2M 装置的 300MVA 发电机组保护装置

为保证 HL-2M 装置的 300MVA 立式发电机组的安全运行,需要对其设置保护装置。针对机组自身 特性,保护装置为发电机的多分支绕组采用了完全裂相横差保护、完全纵差保护和零序电流型横差保护。基于机 组脉冲工作模式,保护装置采用了快速频率跟踪算法实现频率变化时对发电机组的电压电流快速跟踪测量。实验 证明该保护装置满足机组的安全运行要求。      

高温热裂解电催化剂Ketjen Black EC300J碳黑负载钴卟啉的氧还原性能

选用具有高介孔表面积和高导电性能的碳黑Ketjen Black EC 300J(简称KB)作为载体,制备了碳黑负载钴卟啉(CoTMPP/KB),经过900℃热处理后得到电催化剂,用于燃料电池阴极氧还原反应.利用循环伏安法(CV)研究了碳载体不同预处理方法以及高温热处理对碳黑负载钴卟啉电催化剂的氧还原催化性能的影响.结果表明,6 mol/L HNO3预处理可以很好地改善KB性能,碳黑负载钴卟啉经过900℃热处理得到的电催化剂,虽然其中钴卟啉的结构发生了裂解,但催化剂具有较好的氧还原催化性能,阴极峰值电位(Ep)及最大电容电流(Ip)均为最佳.采用IR、XRD、TEM和氮吸附/脱附等手段对KB碳黑以及电催化剂表面性质及微观结构进行了分析,经6 mol/L HNO3预处理的KB碳黑表面羟基(—OH)等含氧基团增多,团聚不明显,平均粒径约30 nm;孔结构主要由孔径分布较窄的中孔组成,是一种较好的电催化剂载体;经900℃热处理后,电催化剂结构中有CoC3(101)和金属态Co(111)结构出现,钴离子在碳黑表面的分散较好,平均孔径为8.2 nm,比表面积为463.4 m2/g.