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排序方式: 共有147条查询结果,搜索用时 15 毫秒
31.
Elina Siirola Francesco G. Mutti Barbara Grischek Sebastian F. Hoefler Walter M. F. Fabian Gideon Grogan Wolfgang Kroutil 《Advanced Synthesis \u0026amp; Catalysis》2013,355(9):1703-1708
Prochiral bicyclic diketones were transformed to a single diastereomer of 3‐substituted cyclohexylamine derivatives via three consecutive biocatalytic steps. The two chiral centres were set up by a C C hydrolase (6‐oxocamphor hydrolase) in the first step and by an ω‐transaminase in the last step. The esterification of the intermediate keto acid was catalysed by a lipase in the second step if possible. For two substrates the C C hydrolytic step as well as the esterification could be run simultaneously in a one‐pot cascade in an organic solvent. In one example, the reaction mixture of the first two steps could be directly subjected to bio‐amination in an organic solvent without the need to change the reaction medium. Depending on the choice of the ω‐transaminase employed and the substrate the cis‐ as well as the trans‐diastereomers could be obtained in optically pure forms. 相似文献
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Lack of male teachers: a problem for students or teachers? 总被引:5,自引:0,他引:5
Elina Lahelma 《Pedagogy, Culture & Society》2000,8(2):173-186
This article explores young people's perspectives on males and females as teachers, contrasting these with teachers' perceptions. It builds on 90 interviews of school students aged 13-14 and 60 follow-up interviews 4 years later. The first interviews were conducted in ethnographic context in two secondary schools in the mid-1990s in Helsinki, Finland. Whilst lack of male teachers is a recurrent theme in educational discussion, widely agreed among teachers, gender did not appear to be relevant when young persons talked about teachers. They appreciate teachers, irrespective of gender, who can teach and are friendly and relaxed, but who nevertheless keep order and make sure that students work. Male teachers who teach popular, non-academic subjects were often favoured by boys, but so were female teachers of academic subjects and increasingly as time went on. The interviews suggest that students do not need male teachers to act as 'male models'. They also suggest that male teachers should be sensitive in relationships with female students. When questioned explicitly, most of the interviewees did not regard lack of male teachers as a major problem 相似文献
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Elina Mäntylä Sven Kleier Carita Lindstedt Silke Kipper Monika Hilker 《Journal of chemical ecology》2018,44(12):1127-1138
Insectivorous birds feed upon all developmental stages of herbivorous insects, including insect eggs if larvae and adults are unavailable. Insect egg deposition on plants can induce plant traits that are subsequently exploited by egg parasitoids searching for hosts. However, it is unknown whether avian predators can also use egg-induced plant changes for prey localization. Here, we studied whether great tits (Parus major) and blue tits (Cyanistes caeruleus) are attracted by traits of the Scots pine (Pinus sylvestris) induced by pine sawfly (Diprion pini) egg deposition. We chose this plant – insect system because sawfly egg deposition on pine needles is known to locally and systemically induce a change in pine volatile organic compounds (VOCs), and tits are known to prey upon sawfly eggs. In dual choice laboratory experiments, we simultaneously offered the birds an egg-free control branch and a systemically egg-induced branch. Significantly more birds visited the egg-induced branch first. We confirmed by GC-MS analyses that systemically egg-induced branches released more (E)-β-farnesene compared to control branches. Spectrophotometric analyses showed that control branches reflected more light than egg-induced branches throughout the avian visual range. Although a discrimination threshold model for blue tits suggests that the birds are poor at discriminating this visual difference, the role of visual stimuli in attracting the birds to egg-induced pines cannot be discounted. Our study shows, for the first time, that egg-induced odorous and/or visual plant traits can help birds to locate insect eggs without smelling or seeing those eggs. 相似文献
36.
Elina Eskelä 《住房,理论和社会》2018,35(4):474-494
AbstractAlthough relatively understudied, the role of affordable and acceptable housing in the accelerating global competition for talent is of utmost importance, especially if highly skilled migrants are to be absorbed into the permanent labour force. This paper concerns the housing of skilled Indian migrants in the Helsinki metropolitan area in Finland, and contributes to the literature on international migration and the housing of ethnic minorities. It presents a case study on how to analyse migrants’ housing pathways, examining the meaning of housing in the transnational lives of this relatively affluent migrant group. The results show that homeownership is a not a simple indicator of commitment to the host society, and that those responsible for national housing policy need to ensure the supply, quality and reasonable price of accommodation in order to fulfil the housing needs of skilled migrants. 相似文献
37.
Scientists and engineers need computational power to satisfy the increasing resource intensive nature of their simulations. For example, running Parameter Sweep Experiments (PSE) involve processing many independent jobs, given by multiple initial configurations (input parameter values) against the same program code. Hence, paradigms like Grid Computing and Cloud Computing are employed for gaining scalability. However, job scheduling in Grid and Cloud environments represents a difficult issue since it is basically NP-complete. Thus, many variants based on approximation techniques, specially those from Swarm Intelligence (SI), have been proposed. These techniques have the ability of searching for problem solutions in a very efficient way. This paper surveys SI-based job scheduling algorithms for bag-of-tasks applications (such as PSEs) on distributed computing environments, and uniformly compares them based on a derived comparison framework. We also discuss open problems and future research in the area. 相似文献
38.
Gohar Tsakanova Aida Avetisyan Elena Karalova Liana Abroyan Lina Hakobyan Anna Semerjyan Naira Karalyan Elina Arakelova Violetta Ayvazyan Lusine Matevosyan Arpine Navasardyan Anna Ayvazyan Hakob Davtyan Bagrat Grigoryan Arsen Arakelyan Zaven Karalyan 《International journal of molecular sciences》2022,23(12)
Anemia is a commonly observed consequence of whole-body exposure to a dose of X-ray or gamma irradiation of the order of the mean lethal dose in mammals, and it is an important factor for the determination of the survival of animals. The aim of this study was to unravel the effect of laser-driven ultrashort pulsed electron beam (UPEB) irradiation on the process of erythropoiesis and the redox state in the organism. Wistar rats were exposed to laser-driven UPEB irradiation, after which the level of oxidative stress and the activities of different antioxidant enzymes, as well as blood smears, bone marrow imprints and sections, erythroblastic islets, hemoglobin and hematocrit, hepatic iron, DNA, and erythropoietin levels, were assessed on the 1st, 3rd, 7th, 14th, and 28th days after irradiation. Despite the fact that laser-driven UPEB irradiation requires quite low doses and repetition rates to achieve the LD50 in rats, our findings suggest that whole-body exposure with this new type of irradiation causes relatively mild anemia in rats, with subsequent fast recovery up to the 28th day. Moreover, this novel type of irradiation causes highly intense processes of oxidative stress, which, despite being relatively extinguished, did not reach the physiologically stable level even at the 28th day after irradiation due to the violations in the antioxidant system of the organism. 相似文献
39.
Pii Elina Berghäll 《Industry and innovation》2012,19(2):127-153
According to knowledge-based growth theories, catch-up with the global technology frontier calls for a shift from physical investment to innovation. This prevailing premise in Finland is tested with an unbalanced panel of firms in Finnish information and communications technology (ICT) manufacturing, over a period of rapid growth, 1990–2003. Stochastic frontier model estimation results are overwhelmed by scale elasticity associated productivity growth. Contrary to beliefs, R&D productivity was relatively low, regardless if measured by efficiency impacts of R&D intensity, technical change or R&D elasticity of output. Results are consistent with industry outcomes and reveal internal causes to the subsequent downfall of ICT manufacturing in Finland. 相似文献
40.
In this paper, the optimal process parameters of a wave soldering process were defined. The optimization was performed in respect to soldering quality by minimizing a cost function describing the total repairing cost of a wave-soldered printed circuit board (PCB). The data analysis stages were as follows. First, the process data were coded into inputs for a self-organizing map (SOM). Next, a function for the repairing cost was constructed and used to find the optimal map neurons. At the last phase, the optimal parameters were approximated on the basis of the reference vectors of the optimal neurons. The results showed clearly potential in the optimization of the wave soldering process, especially in the visualization of the optimal process conditions. Therefore, it would be useful to exploit the method more widely in the electronics industry. 相似文献