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71.
Ethylene/1-olefin copolymerization using vanadium and titanium complexes bearing tetradentate [O,N,N,O]-type ligand and EtAlCl2 or MAO as a cocatalyst is carried out. In the presence of the vanadium complex activated with EtAlCl2 is observed (a) negative “comonomer effect”, (b) high comonomer incorporation and narrow chemical composition distribution (CCD), (c) unexpected copolymer microstructure, and (d) increased molecular weight of copolymers when compared with the homopolymer. In contrast, titanium catalyst gives copolymers with lower 1-olefin content and broad CCD. Supported complexes show higher activity, lower 1-olefins incorporation and give copolymers with ultra high molecular weights. 相似文献
72.
Anna Lebiedzińska Marcin L. Marszałł Małgorzata Grembecka Jakub Czaja Piotr Szefer Jadwiga Kuta Brady D. Garabato Pawel M. Kozlowski 《Food Analytical Methods》2018,11(3):725-732
A reversed phase high-performance liquid chromatography method (HPLC) with coulometric electrochemical detection has been applied and validated for the simultaneous analysis of pyridoxamine (PM), pyridoxal (PL), and pyridoxine (PN) in cereal products. Isocratic separation was achieved using a C18 column with a mobile phase consisting of methanol-phosphate buffer (10:90) and 0.018 M trimethylamine adjusted to pH 3.55 with 85% orthophosphoric acid. The limits of detection for PM, PL, and PN were 0.28, 0.36, and 0.43 ng mL?1, respectively, with vitamins recoveries ranging from 90.4 to 98.1%. The applied method for the analysis of B6 vitamins naturally present in grain products, offers a simple and fast sample preparation without derivatization. To understand vitamer separation further, methods of computational chemistry were employed. Specifically, density functional theory (DFT) was used to determine electrostatic potentials, as well as the charges of each vitamer. A number of correlations were established between these properties and elution order. 相似文献
73.
Zusammenfassung Für Soja- und Süßlupinenmehl aus geschälten Sojabohnen bzw. geschälten Süß-lupinen (Züchtung aus gelben Lupinen) wird je ein polarisationsmikroskopischer Nachweis im Einschlußmittel Nelkenöl oder anderen nichtwäßrigen Mitteln und mit dem Gipskompensator Rot I.O. angegeben, welcher sich auf charakteristische unterschiedliche Kristalle in den Cotyledonarzellen beider Leguminosensamen stützt. 相似文献
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76.
A methodology for assessing perceptions of a product through cost-benefit analysis is demonstrated in an experimental study involving use of one of two products for supporting interaction with telephone voice menu systems. The method emphasizes ratings of constructs related to costs and benefits considered relevant to decisions regarding product adoption, and the use of the analytic hierarchy process technique to derive subjective importance weights associated with those constructs. Twenty-five younger subjects (18-39 years of age) and 27 older subjects (60-82 years of age) interacted with simulated telephone voice menu systems supported by either a screen phone or a graphical device. Although analysis of the benefit-cost ratios revealed that benefits were perceived as more important than costs, the analysis of the constituent item ratings and importance weights provided potentially more useful information for predicting product adoption. 相似文献
77.
Age differences in the use of telephone menu systems were investigated in two experiments. Participants from three age groups (younger: 18-39; middle-aged: 40-59; older: 60+ years) were required to obtain specified information or perform some action using simulated voice menu systems. Measures reflecting task performance, menu navigation, and subjective responses were collected. The focus in Experiment 1 was on examining the effect of speech rate. Data from 196 participants indicated age differences in performance, especially for complex problems. There was no effect of speech rate on any of the performance measures. Experiment 2 examined two types of support devices: a screen phone and a graphical aid. Data from 114 participants indicated that the screen phone provided some benefits in navigational efficiency. In terms of performance, the older participants benefited more from the graphical aid and the younger participants performed better with the screen phone. Actual or potential applications of this research include guidance in the use of support devices that can reduce memory demands and the identification of appropriate speech rates. 相似文献
78.
Anna Czaja Anna Czubaszek Dorota Wyspiańska Anna Sokół-Łętowska Alicja Z. Kucharska 《International Journal of Food Science & Technology》2020,55(4):1725-1734
We determined the effect of onion skin extract (OE) on the quality of wheat bread: contents of total polyphenols and flavonols, antioxidative activity and their changes during storage. With increasing doses of OE to bread, contents of total polyphenols and flavonols and the antioxidative activity were observed to increase. A higher total flavonol content was found in bread with 1% OE stored at 24 °C than in bread stored at 4 °C. There was no such relationship in the bread with 0.5% OE. Changes in flavonols content during storage for 72 h were insignificant. No clear trends of change in the antioxidant activity could be found at storage of breads. The addition of OE caused no changes in the yield and volume of bread and contributed to a decreasing value of L* parameter and to increasing values of ΔE, a* and b* parameters of bread crumb colour. Consumers accepted the smell and taste of bread with the addition of OE to a lesser extent than the control bread. Bread with 1% OE the taste was rated very low. Consumers rated the taste of bread with 1% OE low because it was bitter. Breads enriched with OE had a proper external appearance as well as crumb and crust features. Roasted onion aroma and taste were perceptible in the obtained breads. A bitterness was perceptible in breads baked with the addition of 1% of OE. 相似文献
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80.
The impact of aging on access to technology 总被引:3,自引:0,他引:3
The number of people over the age of 65 is increasing worldwide with the fastest growing subgroup those aged 80+ years. Computer
and information technologies hold promise in terms of increasing the quality of life for older people. However, successful
use of technology by older adults is predicated on systems that are designed to accommodate the needs and preferences of this
user group. This paper discusses the implications of age-related changes in cognition for system design. Generally, the existing
literature shows that, although older adults are willing to use technology, many report usability problems with existing systems
and these problems may in part be due to the cognitive and perceptual demands placed on the user. These findings are discussed
in terms of guidelines for system design. 相似文献