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101.
The thermoreversible gelation of semi-diluted atactic polyacrylnitrile (PAN)/dimethylformamide (DMF)-solutions has been studied. The structural features of PAN/DMF-gels, formed by supercooling have been investigated by DSC-, x-ray- and swelling measurements. A new structural model has been introduced to describe the morphology of the junction zones of PAN/DMF-gels and to also explain the gelation behavior of PAN/DMF-solutions as the structural features of PAN/DMF-gels. The junction zones of a PAN/DMF-gel have been defined as ordered junction zones.A gelation enthalpy of about H=–6 kJ/mol supports the idea that an ordered junction zone is formed by intermolecularly neighboring stereoregular parts of atactic PAN chains due to a nucleation process in the solution. It can be defined as a strongly distributed fringed micelle. 相似文献
102.
103.
具有优良NLO性质的芪唑盐(记为S)已被用于制备LB薄膜,但其成膜性不好,稳定性差;S和花生酸镉(记为A)的混合系虽可改善成膜性,但在此混合膜系中,S相的稳定性仍然不佳。应用SAXS和微机模型拟合(MCMI)研究了上述两类LB薄膜的凝聚态结构,结果指出:在LB薄膜的二维类晶系结构中,S分子中呈哑铃形的芪唑基倾向于作倾斜状的密堆砌,S分子中的丙条脂肪链则倾向于采取全反式燕尾式构象,而且脂肪链只占S分子长的2/3,这就导致了S分子在二维类晶系结构中凝聚力的下降,以及造成LB薄膜层状超分子结构的破坏和崩塌。 相似文献
104.
As the application of a dielectric theory proposed previously (J Membrane Sci 64:153–161 (1991)), theoretical formulation and the practical procedure of dielectric analysis are developed to calculate the structural parameters such as the conductivity gradient and the thickness of the concentration polarization layer, the capacitances and the conductances of the two adjoining aqueous phases from the observed dielectric parameters. The procedure of calculation consequent upon the theoretical formulation was applied to double relaxation data observed for cation-exchange membrane systems under application of d.c. bias voltage. As a consequence, the structural parameters of concentration polarization were readily obtained with accuracy. 相似文献
105.
106.
Maria?NowakowskaEmail author Krzysztof?Szczubia?ka Miros?aw?Gr?bosz 《Colloid and polymer science》2004,283(3):291-298
The interactions between copolymers of sodium styrene sulfonate (SSS) and N-isopropylacrylamide (NIPAM), anionic polyelectrolytes, and dodecyltrimethylammonium chloride (DTAC), a cationic surfactant, were studied in aqueous solutions of various ionic strengths. The copolymers were found to be thermoresponsive, showing a lower critical solution temperature (LCST). The influence of the polymer composition, the surfactant concentration, and the ionic strength on the LCST was studied. The surfactant was found to interact strongly with the polymer, forming mixed polymer-surfactant micelles. The critical aggregation concentration (cac) of the polymer-surfactant system was found from fluorescence spectroscopy using pyrene as a fluorescent probe. A strong dependence of the anionic polyelectrolyte-cationic surfactant interactions on the structure of the ionic comonomer was observed. 相似文献
107.
Traceability of the measurement of analytical parameters capable of evaluating the performance of methods is an important
concept for the assessment of quality for the routine control, especially for residue monitoring of non-authorized medicinal
substances in food from animal origin. The European Decision no. 657/2002/EC recommends to calculate two statistical limits,
CCα and CCβ, which allow to evaluate the critical concentrations above which the method reliably distinguish and quantify
a substance taking into account the variability of the method and the statistical risk to take a wrong decision. The calculation,
which can be derived from the ISO standard no. 11843 is applied on a routine basis. An example displays a very simple way
for evaluating the performance of an LC-MSMS method which has been validated a few years ago and is qualified onto a Micromass
Quattro LCZ tandem mass spectrometer to monitor and confirm the nitrofuran metabolite residues in food from animal origin.
Community Reference Laboratory for Antimicrobial Veterinary Drug Residue Control in Food from Animal Origin 相似文献
108.
Hong JW Benmansour H Bazan GC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(14):3186-3192
Conjugated polymers and oligomers can serve as highly responsive fluorescent reporters for biosensor applications. However, their optical properties in aqueous media are highly dependent upon environmental conditions. The structure of the paracyclophane framework provides a platform for designing optical reporters that show little sensitivity to surfactants, and thus is well-suited for fluorescent assays. The permanent intramolecular delocalization through the paracyclophane core dominates intermolecular perturbations in spontaneously formed aggregates. 相似文献
109.
本文从商品化的间溴苯甲醚和对甲氧基苯甲醛出发,通过傅-克酰基化反应、串联的羟醛缩合及1,4-迈克尔加成反应,得到三芳基取代的1,5-二酮,然后用查尔酮(Chalcone)作氧化剂,二酮与BF3.Et2O 反应形成吡喃鎓盐,再与苯基乙酸钠盐缩合得到芳香二溴代衍生物,产物的DMA溶液在DBU和钯催化剂的作用下,160°C 加热12 h进行脱卤化氢环化反应, 生成四甲氧基取代的二苯并并四苯(DBN)类衍生物。并报道了产物的晶体结构和在溶液中的聚集效应。 相似文献
110.
Pierre Parisot 《商业与工业应用随机模型》1985,1(1):35-54
We studied a population of paraplegic patients in order to give prominence to a possible relationship between the topography of their spinal lesion and the occurrence of special articular diseases (P.O.A.). According to the motor and sensory state of their spinal cord, we first tried to obtain a classification of these lesions (the usual one schematically separates ‘flaccid’ and ‘rigid’ paraplegics). We mainly put the emphasis on this clustering step of the study:
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