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1.
P. R. J. M. Smits P. H. Van Lieshout A. A. F. Van De Ven 《Journal of Engineering Mathematics》1989,23(2):157-186
A variational principle for the magnetoelastic stability problem of superconductors is constructed. Independently, a pair of integral equations is derived, from which the initial and the perturbed field can be computed. The integral equations are solved for in-plane buckling of a slender pair of concentric tori, and out-of-plane buckling of a slender pair of equal coaxial tori. By using the variational principle, it is shown that both cases can become unstable when the currents on the two tori are equally directed, and the pertinent buckling values are calculated. The thus obtained buckling values are compared with the results of an alternative, mathematically less rigorous, method. A good correspondence between the two methods is found (at least as long as the two tori are not too near). 相似文献
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In a placebo-controlled, double-blind randomized design, we investigated the cardiovascular interaction between caffeine (250 mg intravenously) and nicotine (4 mg chewing gum) in 10 healthy volunteers, both under baseline conditions and during physical and mental stress (standing up and mental arithmetic). Caffeine alone induced a significant increase in blood pressure associated with a decrease in heart rate, whereas nicotine alone increased both blood pressure and heart rate. The combination of caffeine and nicotine increased systolic and diastolic blood pressure by 10.8 +/- 2.0 and 12.4 +/- 1.9 mm Hg, respectively. This pressor response did not differ significantly from the calculated additive effects of caffeine and nicotine on blood pressure, measuring 12.9 +/- 2.0 and 14.2 +/- 2.1 mm Hg, respectively. Heart rate and forearm blood flow also showed a similar response when the combination of caffeine and nicotine was compared with the calculated sum. During physical stress (standing up), blood pressure, heart rate, and plasma catecholamines increased in the placebo test. The pressor response to standing up was less pronounced after the combination of caffeine and nicotine compared with the sum of the separate effects (combination versus sum: delta diastolic blood pressure, 24.7 +/- 1.9 versus 35.2 +/- 2.6 mm Hg [p < 0.01]; delta mean arterial pressure, 22.1 +/- 2.0 mm Hg versus 28.6 +/- 1.6 mm Hg [p < 0.05]). The plasma catecholamine response did not differ between the combination and the sum of both drugs. During mental arithmetic, blood pressure, heart rate, and forearm blood flow increased in the placebo test. The forearm vasodilator response to mental stress was attenuated by the combination of caffeine and nicotine compared with the sum of both drugs (combination versus sum: delta forearm blood flow, -0.1 +/- 0.3 versus 1.4 +/- 0.5 ml/100 ml/min [p < 0.05]). We conclude that the combined administration of caffeine and nicotine shows additive effects on cardiovascular parameters during baseline conditions but less than additive effects during sympathoadrenal stimulation. 相似文献
3.
Taming monsters: The cultural domestication of new technology 总被引:1,自引:0,他引:1
Central to public discomfort about new technologies is the notion that they are unnatural. Experts often suppose that better knowledge of technology and risks would help overcome public aversion. This assumption turns out to be fairly fruitless, often even increasing social polarization. The pattern of diverging risk assessments about technology might be improved by a better understanding of the moral gut feelings at stake. However, current technology ethics does not seem to be equipped for elaborating theories to explain public discomfort. Either public fear is not taken seriously, or ethical–theoretical rationalizations of moral intuitions lead to unsatisfactory, naturalist constructions, such as the intrinsic value of nature.For a better understanding of current risk controversies, a detour is made to the cultural anthropology of Mary Douglas on pre-modern ideas regarding danger. This offers some clarifying insights into modern perceptions of technological risks. Departing from anthropological observations, a so-called monster theory is sketched, which gives an explanation for the fascination with and aversion towards new technology, leaving aside ‘naturalist’ and ‘nature-skeptic’ explanations of technology ethics. Monster theory offers a point of departure for a new, pragmatic approach to controversies about new technology, the approach being named a pragmatist monster-ethics. It tells us we have to reflect on and shift cultural categories as well as to adapt technologies in order to domesticate our technological ‘monsters’. 相似文献
4.
Alkema WB Hensgens CM Snijder HJ Keizer E Dijkstra BW Janssen DB 《Protein engineering, design & selection : PEDS》2004,17(5):473-480
Penicillin acylase catalyses the condensation of Calpha-substituted phenylacetic acids with beta-lactam nucleophiles, producing semi-synthetic beta-lactam antibiotics. For efficient synthesis a low affinity for phenylacetic acid and a high affinity for Calpha-substituted phenylacetic acid derivatives is desirable. We made three active site mutants, alphaF146Y, betaF24A and alphaF146Y/betaF24A, which all had a 2- to 10-fold higher affinity for Calpha-substituted compounds than wild-type enzyme. In addition, betaF24A had a 20-fold reduced affinity for phenylacetic acid. The molecular basis of the improved properties was investigated by X-ray crystallography. These studies showed that the higher affinity of alphaF146Y for (R)-alpha-methylphenylacetic acid can be explained by van der Waals interactions between alphaY146:OH and the Calpha-substituent. The betaF24A mutation causes an opening of the phenylacetic acid binding site. Only (R)-alpha-methylphenylacetic acid, but not phenylacetic acid, induces a conformation with the ligand tightly bound, explaining the weak binding of phenylacetic acid. A comparison of the betaF24A structure with other open conformations of penicillin acylase showed that betaF24 has a fixed position, whereas alphaF146 acts as a flexible lid on the binding site and reorients its position to achieve optimal substrate binding. 相似文献
5.
Marketing Activities to Support ‘Moderately Novel’ Product Innovation: Insights from the Chemical Industry 下载免费PDF全文
Scholars often follow a contingency approach to study which marketing activities are suitable for a particular type of product innovation project, thereby making a distinction between incremental and radical innovation only. ‘Moderately novel’ projects, which have intermediate levels of newness, have therefore not been given due attention. This paper focuses on market intelligence generation and the creation of cross‐functional linkages as marketing activities that are important in the context of moderately novel product innovation. In addition, the organizational position of the marketers involved in these activities is dealt with. Based on the analysis of four successful projects in the chemical industry, we argue, firstly, that moderately novel innovation projects have their own particular sets of marketing practices and, secondly, that differences exist between projects aiming at a new market segment and projects in which novelty is not related to market segment but to other market dimensions. These differences are especially salient in early project phases. These findings are pertinent to research on the role of marketers in product innovation, and to the study of organizational ambidexterity. 相似文献
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8.
Bellemans Inge De Wilde Evelien Blanpain Bart Moelans Nele Verbeken Kim 《Metallurgical and Materials Transactions B》2017,48(6):3058-3073
Metallurgical and Materials Transactions B - This study investigates the origin of mechanically entrained metal droplets in liquid slag due to their interaction with solid spinel particles. Two... 相似文献
9.
Origin and Processing Methods Slightly Affect Allergenic Characteristics of Cashew Nuts (Anacardium occidentale) 下载免费PDF全文
Marit Reitsma Shanna Bastiaan‐Net Lutske Sijbrandij Evelien de Weert Stefano Sforza Roy Gerth van Wijk Huub F. J. Savelkoul Nicolette W. de Jong Harry J. Wichers 《Journal of food science》2018,83(4):1153-1164
The protein content and allergen composition was studied of cashews from 8 different origins (Benin, Brazil, Ghana, India, Ivory Coast, Mozambique, Tanzania, Vietnam), subjected to different in‐shell heat treatments (steamed, fried, drum‐roasted). On 2D electrophoresis, 9 isoforms of Ana o 1, 29 isoforms of Ana o 2 (11 of the acidic subunit, 18 of the basic subunit), and 8 isoforms of the large subunit of Ana o 3 were tentatively identified. Based on 1D and 2D electrophoresis, no difference in allergen content (Ana o 1, 2, 3) was detected between the cashews of different origins (P > 0.5), some small but significant differences were detected in allergen solubility between differently heated cashews. No major differences in N‐ and C‐terminal microheterogeneity of Ana o 3 were detected between cashews of different origins. Between the different heat treatments, no difference was detected in glycation, pepsin digestibility, or IgE binding of the cashew proteins. 相似文献
10.
Home-ownership is transmitted between generations. Parental gifts form one of the mechanisms through which the intergenerational transmission of home-ownership takes place. Using the Netherlands Kinship Panel Study, we investigated the influence of parental and children’s resources and other characteristics on financial support from parents to children. A major independent variable was parental home-ownership. As dependent variables, we distinguished between financial support towards buying a home, and financial support in the form of gifts of € 5,000 or more ever received. By making this distinction, we could test whether homeowner parents were particularly likely to help their children become homeowners rather than giving other types of financial help. The results did not indicate such specific gift-giving: parental home-ownership was just as important to other types of monetary support as to home-ownership support. However, the distance to the place where the adult child had grown up was negatively associated with receiving home-ownership support but not with receiving other financial transfers. 相似文献