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61.
Rika E. Anderson Alexis D. Ostrowski Danielle E. Gran Jesse D. Fowler Alan R. Hopkins Randy M. Villahermosa 《Polymer Bulletin》2008,61(5):563-568
Summary Various diameters of polyaniline (PANI) nanofibers were easily made by varying the sweep rate in the
electrochemical polymerization of the aniline monomer. At a sweep rate of 5 mV/s, the PANI nanofibers have
an average diameter of 450 nm with a median of 440 nm. The fibers are short, on the order of a few microns
in length, and exhibit a branched geometry. Increasing the sweep rate to 50 mV/s produced longer nanofibers
with a smaller average diameter of 200 nm. Nanofibers synthesized at 100 mV/s were noted to be smaller
with an average and median diameter of 100 nm. These results illustrate the ease in which the morphology
of nanostructured PANI can be altered and indicate that the method has the potential to create multi-diameter
fibers or mixed-morphology materials. 相似文献
62.
The C2 products formed over Ru during Fischer-Tropsch synthesis often lie well below the Anderson-Schulz-Flory line describing the C4+ products. This has led to speculation that either the surface precursor to C2 hydrocarbons is exceptionally long lived, or that the ethylene formed by CO hydrogenation readsorbs and thereby reenters the chain growth process. In this study, the role of ethylene readsorption on the dynamics of chain initiation and growth is investigated using13CO/H2 and12C2H4 to differentiate between the carbon sources. Ethylene addition is found to suppress the rate of methanation and increase the rates of formation of C3+ hydrocarbons. Ethylene serves as an effective chain initiator, as well as a source of C1 monomer species which participate in chain propagation. No evidence is seen, though, for the participation of C2 species in chain propagation. 相似文献
63.
Manolis D. Tzirakis Ioannis N. Lykakis George D. Panagiotou Kyriakos Bourikas Alexis Lycourghiotis Christos Kordulis Michael Orfanopoulos 《Journal of Catalysis》2007,252(2):178-189
Four supported catalysts with the same tungsten loading were prepared by depositing decatungstate species W10O4−32, through wet impregnation, on the surface of γ-alumina and silica at different pH values. The prepared samples were characterized using BET measurements as well as XRD, UV–vis DR, and XP spectroscopies. Higher dispersion of W(VI) oxo-species was obtained in the silica-supported catalysts compared with the corresponding alumina-supported ones. Within the same support, the dispersion was higher when the impregnation pH is lower than the point of zero charge (pzc) of the support. The decatungstate anions were present mainly on the silica surface without any modification, whereas these underwent a partial depolymerization on their deposition on the γ-alumina surface. The extent of depolymerization was less in the sample prepared at pH above pzc. These findings were explained in terms of the mode of deposition of the W(VI) species from the solution onto the support surface. The photocatalytic activity of the aforementioned catalysts, concerning the photooxidation of 1-phenylethanol, depends on the fraction of the W10O4−32 supported species rather than on the W(VI) dispersion. Thus, extremely high conversions have been obtained over the silica-based catalysts and also over the γ-alumina-based catalyst prepared at relatively high pH. These catalysts also are very effective in the photooxidation of a series of secondary and primary benzyl alcohols, in which benzyl ketones and benzoic acids were formed as the only or major products, respectively. The easy separation of the solid catalyst from the reaction mixture, the high activity, selectivity, and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis. Based on product analysis and kinetic data on the heterogeneous oxidation of benzyl alcohols, we suggest that a hydrogen abstraction transfer (HAT) mechanism predominates with respect to an electron transfer (ET) one in these reactions. 相似文献
64.
65.
66.
G. K. Alexis 《国际能源研究杂志》2005,29(2):95-105
Exergy is based on the second law of thermodynamics and is the only rational basis for evaluating the system performance. The aim of this paper is to study in detail the irreversibilities in the steam‐ejector refrigeration system. The influence of the cycle parameters is analysed on the basis of the first and second law and the results indicated the components with the greater irreversibility. A better quality of the ejector has more effect on the system performance than the better quality of other components, because the ejector at first and the condenser at second have the greater exergy loss of the system. For the refrigeration system the maximum coefficient of performance varying between 0.4 to 0.6 and the second law efficiency remains close to 0.17 for generator pressure 6 bar, condenser temperature 44–50°C and evaporator temperature 4–8°C. Also the study showed that the second law analysis quantitatively visualizes losses within a system and gives clear trends for optimization. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
67.
Roisman Glenn I.; Holland Ashley; Fortuna Keren; Fraley R. Chris; Clausell Eric; Clarke Alexis 《Canadian Metallurgical Quarterly》2007,92(4):678
Although 10 studies have been published on the empirical overlap of the Adult Attachment Interview (AAI) and measures of self-reported attachment style, results in this literature have been inconsistently interpreted in narrative reviews. This report was designed as a rapprochement of the AAI and attachment style literatures and includes 3 studies. Study 1 (combined N = 961) is a meta-analytic review showing that by J. Cohen's (1992) criteria (mean r = .09), the association between AAI security and attachment style dimensions is trivial to small. Study 2 (N = 160) confirms meta-analytic results with state-of-the-art assessments of attachment security and also examines attachment dimensions in relation to the Big 5 personality traits. Finally, Study 3 is an investigation of 50 engaged couples that shows that developmental and social psychological measures of attachment security predict somewhat distinct--though theoretically anticipated--aspects of functioning in adult relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
D Caparros-Lefebvre A Lannuzel C Alexis M Strobel E Janky 《Canadian Metallurgical Quarterly》1997,26(33):1574-1577
BACKGROUND: In Guadeloupe, cases of neurocysticercosis have been rarely observed in people recently immigrated from Haiti. We followed 2 women with seizures, associated with meningitis or encephalitis. CASE REPORT: Computed tomography scan and muscle X-ray have displayed specific features of cysticercosis with small diffuse calcifications. This was associated with positive antibodies for cysticercosis. After respectively 5 and 17 years, these patients developed recurrent manifestations of neurocysticercosis with subacute, quite silent meningitis after pregnancy, with CSF increased cells count (180 lymphocytes/mm3), raised protein level (0.6 g/l) and positive antibodies for cysticercosis in the first case, and cortical granuloma with fever and repetitive seizures in the second. DISCUSSION: These observations suggest that the patients were chronically infested, for more than 5 years. Although the brain lesions were quiescent for many years, new lesions responsible for inflammatory cysts occurred while they still lived outside her native endemic area. In such cases, treatment would benefit to the patient by breaking down the auto-infestation cycle. 相似文献
69.
70.
Walter H. Johnson Alexis A. Gilliland 《Journal of research of the National Institute of Standards and Technology》1961,(1):63-65
The heat of decomposition of potassium perchlorate into potassium chloride and oxygen has been determined in a bomb calorimeter. The process may be represented by the equation: Combination of this datum with the heat of formation of KCl(c) gives −103.22 ±0.15 kcal/mole for the standard heat of formation of KClO4(c) at 25 °C. 相似文献