固定化紫草细胞生产紫草宁衍生物

用海藻胶包埋紫草细胞,在紫草色素生产培养基M_9中,常温、黑暗下培养不同时间,收集培养液并提取色素,进行紫外—可见全波长分光光度扫描和TLC分析。结果表明:固定化紫草细胞可连续分泌紫草色素,其主要成分与天然成分基本相同,产量已达到一定水平。此外对海藻胶包埋条件、固定化珠粒的稳定性以及1L固定化植物细胞反应器生产紫草色素工艺进行了讨论。     

Prediction of Experimental Methanol Decomposition Rates on Platinum from First Principles

A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT) calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004) 3910]. Results from reaction kinetics experiments show that the rate of H₂ production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by the presence of CO or H₂ with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH₃OH→H₂COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species.     

Visual learning and classification of human epithelial type 2 cell images through spontaneous activity patterns

Identifying the presence of anti-nuclear antibody (ANA) in human epithelial type 2 (HEp-2) cells via the indirect immunofluorescence (IIF) protocol is commonly used to diagnose various connective tissue diseases in clinical pathology tests. As it is a labour and time intensive diagnostic process, several computer aided diagnostic (CAD) systems have been proposed. However, the existing CAD systems suffer from numerous shortcomings due to the selection of features, which is commonly based on expert experience. Such a choice of features may not work well when the CAD systems are retasked to another dataset. To address this, in our previous work, we proposed a novel approach that learns a set of filters from HEp-2 cell images. It is inspired by the receptive fields in the mammalian's vision system, since the receptive fields can be thought as a set of filters for similar shapes. We obtain robust filters for HEp-2 cell classification by employing the independent component analysis (ICA) framework. Although, this approach may be held back due to one particular problem; ICA learning requires a sufficiently large volume of training data which is not always available. In this paper, we demonstrate a biologically inspired solution to address this issue via the use of spontaneous activity patterns (SAP). The spontaneous activity patterns, which are related to the spontaneous neural activities initialised by the chemical release in the brain, are found as the typical stimuli for the visual cell development of newborn animals. In the classification system for HEp-2 cells, we propose to model SAP as a set of small image patches containing randomly positioned Gaussian spots. The SAP image patches are generated and mixed with the training images in order to learn filters via the ICA framework. The obtained filters are adopted to extract the set of responses from a HEp-2 cell image. We then employ regions from this set of responses and stack them into “cubic regions”, and apply a classification based on the correlation information of the features. We show that applying the additional SAP leads to a better classification performance on HEp-2 cell images compared to using only the existing patterns for training ICA filters. The improvement on classification is particularly significant when there are not enough specimen images available in the training set, as SAP adds more variations to the existing data that makes the learned ICA model more robust. We show that the proposed approach consistently outperforms three recently proposed CAD systems on two publicly available datasets: ICPR HEp-2 contest and SNPHEp-2.     

Regeneration of zinc particles for zinc–air fuel cells in a spouted-bed electrode

Fuel cells wherein zinc particles form a negative electrode and a gas-diffusion electrode (air electrode) is the positive electrode, are under development. Such cells are dependent on the regeneration of the zinc particles (and electrolyte). This paper describes experiments on electrolytic cells equipped with spouted bed cathodes for use in this application. Experiments have been carried out on laboratory scale cells to determine the operability of cells for growing 'seed particles in the range from 0.4 to 1 mm to measure cell voltage and current efficiency (and thereby energy consumption rate), and to identify a suitable material that could be used as a diaphragm (separating the spouted bed from the oxygen evolving anode). A larger cell, capable of producing up to 10 kg Zn per day, was designed and built. The larger cell was run successfully fifteen times and showed cell voltages and energy consumption rates comparable with those of smaller cells.     

A study of PtRuO2 catalysts thermally formed on titanium mesh for methanol oxidation

Platinum-based catalysts, for the electro-oxidation of methanol, have been made by thermal decomposition of chloride precursors onto titanium mesh. The catalysed electrodes were successfully operated in acidic methanol electrolytes. Electrochemical characterisation has been carried out using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic polarisations. A complete analysis of the electrochemical results showed that the preliminary performance of the catalysed titanium mesh was comparable to that achieved with carbon-supported PtRu catalysts. The catalysts formed on titanium mesh by thermal decomposition also exhibited dimensional stability. Catalysed titanium mesh therefore appears to be a promising alternative to carbon-supported catalysts for certain fuel cell applications.     

Performance of Methanol Oxidation Catalysts with Varying Pt:Ru Ratio as a Function of Temperature

This paper describes the effects of varying the Pt to Ru ratio in carbon-supported catalysts for methanol oxidation as a function of temperature. Previously these effects were studied in isolation, but now it is shown that the composition of a given catalyst as a function of temperature is extremely important for its activity towards methanol oxidation. Platinum rich 3:2 atomic ratio catalysts perform better than a 1:1 catalyst at 25 °C, where only Pt is believed to be active towards methanol dehydrogenation, since this process is a highly thermally activated process on Ru sites. This result is reversed at 65 °C, where the 1:1 catalyst displays much higher currents across the entire range of polarization. This may result from methanol dehydrogenation occurring on both Ru and Pt sites at higher temperatures. At an intermediate temperature, 45 °C, the 3:2 catalyst is seen to perform better at lower current values, while the 1:1 catalyst is superior at higher current densities, with the crossover occurring at 62 A g^–1. As a consequence, when designing fuel cell catalysts, the composition of the catalyst employed should be tailored with respect to the exact operating conditions, in order to promote optimum fuel cell performance.     

Performance and stability of Pt-based ternary alloy catalysts for PEMFC

Carbon-supported Pt-based ternary alloy electrocatalysts were prepared by incipient wetness method in order to elucidate the origin of the enhanced activity of oxygen reduction reaction in PEMFC. To measure the catalytic activity and stability of the cathode alloy catalysts (electrodes containing Pt loading of 0.3 mg/cm², 20 wt.% Pt/C, E-TEK), the I-V polarization curves were obtained. All alloy catalysts showed higher performances than Pt/C. It can be concluded that as platinum formed alloys with transition metals, the electronic state of Pt and the nearest neighbor Pt-Pt distance changes, which significantly influence the electrocatalytic activity for oxygen reduction.Long-term stability test was performed with the Pt₆Co₁Cr₁/C alloy catalyst for 500 h. According to XPS analysis, the lower oxide component with Pt₆Co₁Cr₁/C electrocatalyst provides a large portion of platinum in metallic species in the electrocatalyst and it seems to be mainly responsible for its enhanced activity towards oxygen reduction.     

ASSESSMENT OF RED BLOOD CELL DEFORMABILITY BY CENTRIFUGAL SEDIMENTATION

A centrifugal sedimentation method (CSM) is proposed for the assessment of deformability of red blood cells. The method is based on the premise that a red blood cell (RBC) should deform in a centrifugal field due to the variation of the centrifugal acceleration with the distance from the center of rotation. This change in shape of the RBC leads to a change in the rate of sedimentation in the centrifugal field. The rate of sedimentation, which serves as a measure of deformability, is characterized by an apparent sedimentation coefficient (ASC) and its normalized value (NASC), which is calculated by comparison with a control group of normal RBCs. It has been shown that the NASC is sensitive to the speed of rotation, to treatments with glutaraldehyde, diamide, or chlorpromazine, to heat treatment and to osmotic pressure variations.     

Fabrication and characterization of PFSI/ePTFE composite proton exchange membranes of polymer electrolyte fuel cells

PFSI/ePTFE composite proton exchange membranes were fabricated by impregnating perfluorosulfonic acid resin (PFSI resin, Nafion) into chemically modified expanded PTFE (ePTFE) matrix. Chemical modification of sodium-naphthalene treatment and N-methylol acrylamide (NMA) grafting decreased the contact angle of the as-received ePTFE from 125 ± 0.5° to 67 ± 0.5°, effectively converting the as-received hydrophobic ePTFE to a hydrophilic ePTFE matrix. The composite membrane fabricated with the hydrophilic ePTFE have higher impregnated PFSI loading, much lower porosity and better PTFE/PFSI interface contact, as compared to the composite membranes with the as-received ePTFE. This leads to much lower gas permeability and significantly improves the durability under an accelerated dry/wet cycle test. The fuel cell made from the PFSI/ePTFE composite membranes with hydrophilic ePTFE showed superior performance as compared to that with the composite membrane made from the as-received ePTFE and Nafion 211 membrane.     

直接甲醇燃料电池用碳气凝胶载铂催化剂的研究

利用溶胶—疑胶方法制备了高比表面积的碳气凝胶,利用浸渍还原法制备了Pt/碳气凝胶和Pt/C催化剂。采用BJH和TEM考察碳气凝胶的孔径分布和金属粒子的大小与分布,循环伏安曲线测试考察Pt/碳气凝胶对甲醇催化氧化性能的影响。结果表明,碳气凝胶的比表面积达到480 m2/g,孔径分布良好,催化剂金属颗粒较小,分散较好,循环伏安曲线图显示出Pt/碳气凝胶比传统的Pt/C对甲醇催化氧化性能高。