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31.
Previous studies with macrophages that had been prelabeled with [14C]arachidonic acid (20∶4) have shown that condensed tannin is a potent agonist for the release of arachidonic acid. However,
it has not been demonstrated that the percentage release of [14C]20∶4 accurately reflects the metabolic activity of the endogenous 20∶4 pool. In order to measure the 20∶4 mass release relative
to the total cellular 20∶4 pool, the free fatty acids of freshly isolated alveolar macrophages were derivatized with a fluorescent
reagent, and then separated and quantified by high-performance liquid chromatography. The amounts of esterified fatty acids
were measured by gas chromatography of the methyl esters. Free fatty acid levels were compared to those of the total esterified
plus unesterified fatty acids to determine the actual percentage released of each fatty acid. Tannin-stimulated release of
20∶4 mass reflected that previously reported for the release of [14C]20∶4 label but at a slower rate and at a much lower percentage indicating that [14C]20∶4 had been incorporated into part of a more reactive pool. The specificity of the fatty acid release induced by tannin
and β-1,3-glucan, a known agonist for 20∶4 release, was also examined. Both agonists promoted an increase in the levels of
free 20∶4 and of other fatty acids. A comparison of the absolute increases of each of the fatty acids indicated that tannin
caused a preferential increase in the mass of free 20∶4, whereas β-1,3-glucan evoked a selective increase in the mass of 16∶0.
Deceased. 相似文献
32.
33.
Gordon D. Gemmell Nicholas J. Grant 《JOM Journal of the Minerals, Metals and Materials Society》1957,9(4):417-423
The effects of solid solution alloying on the creep-rupture properties, deformation characteristics, ductility, and fracture of pure aluminum were studied by means of creep-rupture tests on polished specimens of three alloys each of Al-Cu (0.24, 0.79, and 2.05 pct Cu), Al-Zn (4.93, 9.89, and 19.78 pct Zn), and Al-Mg (0.94, 1.92, and 5.10 pct Mg) at 500°, 700°, and 900°F. 相似文献
34.
Nicholas J. Grant Earl C. Roberts John Chipman 《JOM Journal of the Minerals, Metals and Materials Society》1954,6(2):145-149
An equilibrium study was made of the distribution of chromium and oxygen between liquid iron, containing less than 1 pct Cr, and simple slags of the CaO(MgO)-SiO2-FeO-Cr2O3 type in the temperature range 1526° to 1734°C The effects of slag oxidation, temperature, and basicity were observed. 相似文献
35.
Frank E. Curtis Nicholas I.M. Gould Hao Jiang Daniel P. Robinson 《Optimization methods & software》2016,31(1):157-186
In this paper, we consider augmented Lagrangian (AL) algorithms for solving large-scale nonlinear optimization problems that execute adaptive strategies for updating the penalty parameter. Our work is motivated by the recently proposed adaptive AL trust region method by Curtis et al. [An adaptive augmented Lagrangian method for large-scale constrained optimization, Math. Program. 152 (2015), pp. 201–245.]. The first focal point of this paper is a new variant of the approach that employs a line search rather than a trust region strategy, where a critical algorithmic feature for the line search strategy is the use of convexified piecewise quadratic models of the AL function for computing the search directions. We prove global convergence guarantees for our line search algorithm that are on par with those for the previously proposed trust region method. A second focal point of this paper is the practical performance of the line search and trust region algorithm variants in Matlab software, as well as that of an adaptive penalty parameter updating strategy incorporated into the Lancelot software. We test these methods on problems from the CUTEst and COPS collections, as well as on challenging test problems related to optimal power flow. Our numerical experience suggests that the adaptive algorithms outperform traditional AL methods in terms of efficiency and reliability. As with traditional AL algorithms, the adaptive methods are matrix-free and thus represent a viable option for solving large-scale problems. 相似文献
36.
Nicholas Evangelopoulos 《Information Systems Journal》2016,26(1):39-46
This study examines research published in the first 24 years of Information Systems Journal's (ISJ) publication history using a thematic space of all information systems (IS) research as the backdrop. To that end, abstracts from all contributing articles published in eight prominent IS journals in the period 1991–2014 were analysed to extract a latent semantic space of five broad research areas. A two‐dimensional projection of the results was used to create a two‐by‐two map, where one dimension represents the European vs. North American style of IS research and another dimension represents a micro vs. macro level of IS research. The ISJ is positioned in the ‘micro and European school’ quadrant. Over the course of the journal's first 24 years, research in the ISJ started with a relative focus on the IT artefact and IS development and gradually moved towards a more balanced position that includes a considerable amount of research on IT for teamwork and collaboration, as well as on IT and individuals. 相似文献
37.
Leyla Dogruel Sven Joeckel Nicholas D. Bowman 《Behaviour & Information Technology》2015,34(11):1052-1063
Research on elderly people's ICT acceptance and use often relies on the technology acceptance model (TAM) framework, but has been mostly limited to task-oriented uses. This article expands approaches in technology acceptance and use by developing a model to explain entertainment-related uses of new media technology by elderly people. On a theoretical level, we expand the TAM perspective by adding concepts that act as barriers and/or facilitators of technology acceptance, namely technophobia, self-efficacy and previous experience and expertise with technology. We develop an expanded TAM by testing the role of these concepts in two studies on entertainment media technology. In Study 1, we investigate behavioural intention to use 3D cinema among N?=?125 German elderly media users (Age 50+). In Study 2, we focus the actual use of a computer game simulation by N?=?115 German and US elderly media users (Age 50+). Findings in both studies point towards the central role of perceived usefulness, here modelled as enjoyment, as the reason for elderly people's use and acceptance of entertainment media technology. Perceived ease of use is seen as a precondition for enjoyment, particularly for interactive media. 相似文献
38.
39.
Coralia Cartis Nicholas I.M. Gould Philippe L. Toint 《Optimization methods & software》2013,28(3):451-457
This short note considers and resolves the apparent contradiction between known worst-case complexity results for first- and second-order methods for solving unconstrained smooth nonconvex optimization problems and a recent note by Jarre [On Nesterov's smooth Chebyshev–Rosenbrock function, Optim. Methods Softw. (2011)] implying a very large lower bound on the number of iterations required to reach the solution's neighbourhood for a specific problem with variable dimension. 相似文献
40.
A commonly used model for fault-tolerant computation is that of cellular automata. The essential difficulty of fault-tolerant computation is present in the special case of simply remembering a bit in the presence of faults, and that is the case we treat in this paper. We are concerned with the degree (the number of neighboring cells on which the state transition function depends) needed to achieve fault tolerance when the fault rate is high (nearly 1/2). We consider both the traditional transient fault model (where faults occur independently in time and space) and a recently introduced combined fault model which also includes manufacturing faults (which occur independently in space, but which affect cells for all time). We also consider both a purely probabilistic fault model (in which the states of cells are perturbed at exactly the fault rate) and an adversarial model (in which the occurrence of a fault gives control of the state to an omniscient adversary). We show that there are cellular automata that can tolerate a fault rate 1/2−ξ (with ξ>0) with degree O((1/ξ2)log(1/ξ)), even with adversarial combined faults. The simplest such automata are based on infinite regular trees, but our results also apply to other structures (such as hyperbolic tessellations) that contain infinite regular trees. We also obtain a lower bound of Ω(1/ξ2), even with only purely probabilistic transient faults. 相似文献