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排序方式: 共有286条查询结果,搜索用时 15 毫秒
1.
2.
Poly(ethylene aspartate) [PEA] was synthesized by the melt condensation of D,L-aspartic acid and ethylene glycol. PEA containing pendent amino and carbonyl groups in its repeating chain was used as the polymeric ligand for complexation with transition metal ions, viz. Co(II), Ni(II), Cu(II), Mn(II), Zn(II), Cd(II), Ca(II), Mg(II), Pb(II) and Hg(II). Complexation was found to be most effective in DMSO. The resulting polyester-metal complexes were solid coloured materials which have been characterized by IR spectroscopy, elemental analysis and magnetic susceptibility measurements. The thermal stability of the polyester-metal complexes was investigated by thermogravimetric analysis (TGA). On the basis of the physico-chemical studies, an oxygen and nitrogen coordinated structure for the polyester-metal complexes is proposed. 相似文献
3.
Microhardness measurements have been performed on untreated (virgin) and electrically stressed, solvent‐cast laboratory‐prepared samples of pure poly(phenylene oxide) (PPO), pure polystyrene (PS), and PPO : PS polyblends with different weight proportions. Results of such measurement on untreated polyblend sample show that microhardness (Hv) increases with increase in the content of PS up to 10 wt %, which attributed to the existence of homogeneous phase morphology. However, this feature is not observable in samples containing higher content of PS. Electrical stress is found to modify considerably the mechanical property of polymer. The effect of electric field on the microhardness of such samples (PPO : PS :: 90 : 10) has been characterized by the existence of a peak. Trapping of charge carriers in electrically stressed samples imparts hardening to the polyblend up to an applied step field of 190 kV/cm. However, the excessive charging beyond this step field value destroys this characteristic. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
4.
Summary Coordination polymers were synthesized using N,N'-Bis (carboxymethyl) dithiooxamide (NN' CMDTO) and Zinc(II) salts. The complexes were characterized by elemental analyses, IR spectral studies, TGA and viscosity measurements. In the proposed structures the ligand was supposed to be coordinated to metal through sulphur and oxygen. 相似文献
5.
A hydrogel incorporating the hydrophilic polymer poly(ethylene glycol) and a copolymer of acrylamide and styrene was synthesized, and the dynamics of the water‐sorption process were studied. The effects of the composition of the hydrogel and the temperature of the swelling medium were investigated with respect to the water‐sorption characteristics of the hydrogel, and the kinetic parameters, including the swelling exponent and diffusion constant, were evaluated. The hydrogel was also judged for the antithrombogenic property of its surface. The experimental findings were explained on the basis of the core–shell polymeric structure of the hydrogel. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1419–1428, 2002 相似文献
6.
The present paper reports the preparation of full IPNs of gelatin and polyacrylonitrile. Various compositions of gluteraldehyde
crosslinked gelatin and N,N′-methylene-bis-acrylamide crosslinked PAN were characterized by SEM and DSC techniques. The IPNs were also thermally pretreated by the annealing
process. The effects of annealing temperature on the microhardness of IPNs were studied using the Vickers method. SEM indicates
the homogeneous morphological features for IPN. The role of gelatin, AN and crosslinker on the developed hard biopolymer has
been described with the help of DSC thermograms and microhardness measurements of annealed specimens and good correlation
is observed. 相似文献
7.
The aim of this study was to examine the chemical composition of the essential oil isolated from the floral parts of Nandina domestica Thunb. by hydrodistillation, and to test the efficacy of essential oil and various organic extracts against a panel of food-borne pathogenic and spoilage bacteria such as Bacillus subtilis ATCC6633, Listeria monocytogenes ATCC19166, Staphylococcus aureus KCTC1916, S. aureus ATCC6538, Pseudomonas aeruginosa KCTC2004, Salmonella typhimurium KCTC2515, Salmonella enteridis KCCM12021, Escherichia coli 0157-Human, E. coli ATCC8739, E. coli 057:H7 ATCC43888 and Enterobacter aerognes KCTC2190. The chemical composition of essential oil was analysed by GC-MS. It was determined that 79 compounds, which represented 87.06% of total oil, were present in the oil. The oil contained mainly 1-indolizino carbazole (19.65%), 2-pentanone (16.4%), mono phenol (12.1%), aziridine (9.01%), methylcarbinol (4.6%), ethanone (3.3%), furfural (2.96%), 3,5-dimethylpyrazole (1.29%) and 2(5H)-furanone (1.32%). The oil (1000 ppm/disc), and various organic extracts of hexane, chloroform, ethyl acetate and methanol (1500 ppm/disc) exhibited promising antibacterial effect as a diameter of zones of inhibition (9-18 and 7-13 mm) and MIC values (62.5 to 1000 and 250 to 2000 microg/ml), respectively against the tested bacteria. Also the oil had strong detrimental effect on the viable count of the tested bacteria. These results indicate the potential efficacy of plant-based natural products such as essential oil and organic extracts of N. domestica to control food-borne pathogenic and spoilage bacteria. 相似文献
8.
一株具有转化油酸羟基化的微生物Bacillus pum ilus BD-12(记作BP BD-12),在摇瓶条件下分批深层培养,研究了菌株在以胰蛋白胨为主要氮源、葡萄糖为基本碳源的条件下对油酸(OA)的代谢特性,并对转化OA生成羟基脂肪酸的规律及产物进行了分析测定。结果表明:在只有葡萄糖作碳源条件下,细胞生长良好,且无羟基脂肪酸生成,OA对菌株BP BD-12细胞生长有抑制作用;用40 h细胞菌龄添加OA条件下其转化产物为ω-1、ω-2和ω-3-羟基脂肪酸,其转化率和羟基脂肪酸得率最大值分别达到63%和12.3%;通过气质联用方法对产物组分分析,其ω-1-羟基脂肪酸占总羟基脂肪酸的70%,细胞培养过程中未有其它羟基脂肪酸检出。因此,菌株BP BD-12是一株较理想的ω-1-羟基脂肪酸工业化生产菌株。 相似文献
9.
Kanchan Lata Kashyap Manish Kumar Bajpai Pritee Khanna 《Multimedia Tools and Applications》2018,77(8):9249-9269
The present study introduces an efficient algorithm for automatic segmentation and detection of mass present in the mammograms. The problem of over and under-segmentation of low-contrast mammographic images has been solved by applying preprocessing on original mammograms. Subtraction operation performed between enhanced and enhanced inverted mammogram significantly highlights the suspicious mass region in mammograms. The segmentation accuracy of suspicious region has been improved by combining wavelet transform and fast fuzzy c-means clustering algorithm. The accuracy of mass segmentation has been quantified by means of Jaccard coefficients. Better sensitivity, specificity, accuracy, and area under the curve (AUC) are observed with support vector machine using radial basis kernel function. The proposed algorithm is validated on Mini-Mammographic Image Analysis Society (MIAS) and Digital Database for Screening Mammography (DDSM) datasets. Highest 91.76% sensitivity, 96.26% specificity, 95.46% accuracy, and 96.29% AUC on DDSM dataset and 94.63% sensitivity, 92.74% specificity, 92.02% accuracy, and 95.33% AUC on MIAS dataset are observed. Also, shape analysis of mass is performed by using moment invariant and Radon transform based features. The best results are obtained with Radon based features and achieved accuracies for round, oval, lobulated, and irregular shape of mass are 100%, 70%, 64%, and 96%, respectively. 相似文献
10.
Abstract Surfactant-based fracturing gels are considered as clean gels due to the absence of insoluble residues after hydraulic fracturing of tight reservoir. Conventionally used highly viscous polymer gels damage the formation by blocking the fluid path in a fractured formation. The present work has been accomplished with the purpose of evaluating an anionic surfactant-based gel for hydraulic fracturing. Rheological properties and proppant carrying capacity of the synthesized gel were studied as a function of shear rate, temperature, and pH, which affect the gel behavior at the downhole. Proppant carrying capacity was also reported with varying proppant loadings. Rheological properties and proppant carrying capacity of synthesized gel were compared with conventionally used guar gel. 相似文献