基于FPGA的小型光纤光谱仪系统设计

设计了一种小型光纤光谱仪,以FPGA为控制核心,通过CCD实现光电转换,利用USB接口实现光谱仪的供电以及与计算机之间的通讯,采用C++Builder开发计算机软件同时用汞灯谱线进行标定,最后以低压汞灯作为光源对光纤光谱仪进行了性能测试。测试数据表明:该光纤光谱仪在400nm—800nm的有效范围内光谱仪波长扫描精度可达到1nm、像元分辨率可以达到0.12nm/pixel。     

Microstructure and morphology of amine-cured epoxy coatings before and after outdoor exposures—An AFM study

Atomic force microscopy (AFM) has been used to study the morphology and microstructure of an amine-cured epoxy before and after outdoor exposure. Measurements were made from samples prepared in an essentially CO₂-free, H₂O-free glove box and from samples prepared in ambient conditions. For those prepared in a CO₂-free glove box, AFM imaging was conducted on (1) an unexposed air/coating surface, (2) an unexposed coating bulk, (3) an unexposed coating/substrate interface, and (4) a field exposed air/coating surface. For samples prepared in ambient conditions, only the unexposed air/coating surface was investigated. The same regions of the exposed samples were scanned periodically by the AFM to monitor changes in the surface morphology of the coating as UV exposure progressed. Small angle neutron scattering and Fourier transform infrared spectroscopy (FTIR) studies were performed to verify the microstructure and to follow chemical changes during outdoor exposure, respectively. The results have shown that amine blushing, which occurs only under ambient conditions, had a significant effect on the surface morphology and microstructure of the epoxy. The surface morphology of the samples prepared under CO₂-free, dry conditions was generally smooth and homogeneous. However, the interface and the bulk samples clearly revealed a two-phase structure consisting of bright nodular domains and dark interstitial regions, indicating an inhomogeneous microstructure. Such heterogeneous structure of the bulk was in good agreement with results obtained by small angle neutron scattering of unexposed samples and by AFM phase imaging of the degraded sample surface. The relationship between submicrometer physical changes and molecular chemical degradation is discussed. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.     

氟橡胶-金属粘接用环氧胶固化动力学研究

采用具有高热变形温度的砜类聚合物制备的增粘剂,配制了可用于氟橡胶与金属粘接的环氧胶粘剂,通过凝胶时间的测定、差式扫描量热法(DSC)和傅立叶变换红外光谱(FTIR)研究了胶粘剂的固化反应过程及动力学。结果表明,胶粘剂在固化反应过程中有一个宽广且平缓的放热峰,对固化十分有利。胶粘剂固化反应表观活化能为63.8 kJ/mol,固化反应级数为0.891。     

Oxidation of Branched Chain Fatty Acids by Chromic Acid

The kinetics of oxidation of isobutyric and isovaleric acids by chromic acid in sulphuric acid medium have been studied. The end product acetic acid is supposed to be derived from the ketones which are the initial oxidation products of the corresponding branched chain fatty acids. The influence of acetic acid on the oxidation velocity has been examined and a marked effect on the rate constants with increasing acetic acid concentration has been observed. A mechanism involving the electrophilic attack of the oxidant on the tertiary carbon atom of the fatty acid to yield a carbonium ion has been postulated.     

Relationship between chemical degradation and thickness loss of an amine-cured epoxy coating exposed to different UV environments

The relationship between chemical degradation and thickness loss of an unpigmented, non UV-stabilized, crosslinked amine-cured epoxy coating exposed to three UV conditions was investigated. Spin-coated samples having a thickness of approximately 7 μm on an Si substrate were prepared from a stochiometric mixture of a bisphenol A epoxy resin and a tetra-functional amine curing agent. Samples were exposed outdoors and to two accelerated laboratory UV environments. Chemical degradation and thickness loss were measured by transmission Fourier transform infrared spectroscopy (FTIRS) and laser scanning confocal microscopy (LSCM), respectively. In addition, surface roughness and morphological changes were measured by atomic forcemicrosocopy (AFM) and LSCM. Substantial chemical degradation, thickness loss, and morpholocal changes occurred in the exposed films, and the rate of chemical degradation was greater than that due to the thickness loss. This additional chemical loss was attributed to an inhomogeneous degradation process in which nanoscale localized depressions initiate at certain sites on the surface, which then enlarge and deepen with exposure time. The results of this study provide a better understanding of the degradation mechanism and should lead to the development of scientific-based models for predicting the service life of crosslinked amine-cured epoxy coatings. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL     

羧甲基淀粉的应用与合成

综述了羧甲基淀粉的发展、合成方法、合成过程中的影响因素以及应用现状。羧甲基淀粉的合成主要分三种类型 :干法、半干法、湿法。综合了反应过程中的影响因素 ,例如醚化剂和催化剂的影响 ,反应时间和温度的关系 ,溶剂、设备对反应的影响 ,以及在食品、医药、钻井、纺织、日化工业中的应用前景     

Trans FA and solid fat contents of margarines marketed in Turkey

Trans FA (TFA), solid fat contents (SFC), and slip melting points of 12 different tub and stick margarines marketed in Turkey were examined in this study. No trans isomers were found in four margarines, which suggests they were formulated from interesterified or blended fats and oils. The products with no TFA generally had more short-chain saturated FA, which suggests coconut oil-based oil components. TFA content of the other 10 products varied from 7.7 to 37.8%. Compared to the products formulated in North America, Turkish margarines contain more TFA and have higher SFC.     

Purification and characterization of a fatty acid binding protein from human prostatic tissue

Epidemiological studies suggest the existence of a strong relationship between the incidence of prostatic cancer and the intake of dietary lipids in humans. However, very little information is available on intracellular fatty acid metabolism in human prostatic tissue. The objective of this study was to identify and subsequently characterize a fatty acid binding protein of human prostatic tissue. A fatty acid binding protein (FABP) was purified and characterized from human prostatic tissue. The purified FABP had an apparent molecular mass of 15.0±1.0 kDa as averaged from three different methods, sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), gel filtration and amino acid analysis. The pI value of the protein was determined to be 6.8. Scatchard analysis of fatty acid binding to the purified FABP from malignant prostatic tissue showed a Kd value of 0.53±0.02 μM for arachidonic acid (n=5). The Kd values of FABP purified from benign prostatic tissue were 0.57±0.02 μM for oleic acid and 0.51±0.04 μM for arachidonic acid (n=5). Fatty acid analysis revealed that the level of endogenously bound arachidonic acid was about 2.5-fold higher in FABP from malignant than from benign tissue. In addition, both malignant and benign tissues contained the same concentration of FABP. The concentrations of FABP in malignant and benign tissues were 19.2±1.8 and 21.4±2.1 μg per mg of total cytosolic protein, respectively. Characterization based on amino acid composition, isoelectric point and fluorescence with dansyl undecanoic acid suggests that the FABP may not be of the heart type, but is rather more closely related to the liver type. As malignant prostatic tissue produces more PGE₂ compared to benign tissue, our data suggest that FABP may help enhancing the synthesis of the prostaglandin in malignant tissue by facilitating arachidonic acid transport. A preliminary account of this work was presented at the Biochemical Society Meeting, London, December 16–18, 1991, and published as an abstract (Ref. 1).     

KP-Rank: a semantic-based unsupervised approach for keyphrase extraction from text data

Automatic key concept identification from text is the main challenging task in information extraction, information retrieval, digital libraries, ontology learning, and text analysis. The main difficulty lies in the issues with the text data itself, such as noise in text, diversity, scale of data, context dependency and word sense ambiguity. To cope with this challenge, numerous supervised and unsupervised approaches have been devised. The existing topical clustering-based approaches for keyphrase extraction are domain dependent and overlooks semantic similarity between candidate features while extracting the topical phrases. In this paper, a semantic based unsupervised approach (KP-Rank) is proposed for keyphrase extraction. In the proposed approach, we exploited Latent Semantic Analysis (LSA) and clustering techniques and a novel frequency-based algorithm for candidate ranking is introduced which considers locality-based sentence, paragraph and section frequencies. To evaluate the performance of the proposed method, three benchmark datasets (i.e. Inspec, 500N-KPCrowed and SemEval-2010) from different domains are used. The experimental results show that overall, the KP-Rank achieved significant improvements over the existing approaches on the selected performance measures.