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The development of services provided by the National Library of Medicine (NLM), which dates back to 1836, is described. MEDLINE, a database of 10-plus million references and abstracts to the world's biomedical literature, was put on the World Wide Web for free searching in 1997 as a system called PubMed, whose use has grown to over 250 million searches per year. PubMed features a variety of links between MEDLINE references and related information – full-text journal articles, DNA sequence data, medical knowledge bases, etc. – at websites within and outside NLM. PubMed is a major component of a larger NLM system, Entrez, which integrates access to a number of genome-related databases with linking features similar to those of PubMed. The newest linked service, which became a reality in February 2000, is PubMed Central, the National Institutes of Health's free repository for primary research reports in all the life sciences. 相似文献
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Goktug T. Cinar Pedro M.N. Sequeira Jose C. Principe 《Journal of The Franklin Institute》2018,355(4):1638-1662
In this paper we develop a new framework for time series segmentation based on a Hierarchical Linear Dynamical System (HLDS), and test its performance on monophonic and polyphonic musical note recognition. The center piece of our approach is the inclusion of constraints in the filter topology, instead of on the cost function as normally done in machine learning. Just by slowing down the dynamics of the top layer of an augmented (multilayer) state model, which is still compatible with the recursive update equation proposed originally by Kalman, the system learns directly from data all the musical notes, without labels, effectively creating a time series clustering algorithm that does not require segmentation. We analyze the HLDS properties and show that it provides better classification accuracy compared to current state-of-the-art approaches. 相似文献
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The production of knowledge was subjected to quantitative analysis in the second half of the twentieth century, following Arrow (1962). The determinants of knowledge and the externalities present in the innovation process were discussed with immediate policy influence. In particular, the presence and strength of the spillover of the pool of past knowledge has encouraged high subsidization of R&D in the most developed countries. We survey the empirical literature on the spillover effect in the production of knowledge and implement a meta-analytic regression. We discover that the average spillover effect is less than but close to one and is highly significant. We also find that the spillover effect tends to be greater when the estimation of knowledge production accounts for foreign inputs, and it tends to be lower when the estimation includes only rich economies, regional data are used, and the pool of knowledge is not the patent stock. 相似文献
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In paper conservation ethanol is used as an antifungal agent. However, information on the antifungal efficacy of this alcohol is scarce and often inconsistent. In this study, we clarify if ethanol is effective and safe to use in paper conservation in the short as well as in the long term. None of the tested ethanol concentrations (5–100%) promoted conidia germination, but rather delayed or entirely inhibited it, depending on alcohol concentration and contact time. In a simulation of an interventive treatment of samples colonized by fungi, all the tested ethanolic solutions (30, 70, and 100%) revealed antifungal activity. The best results were obtained with 70% ethanol, showing fungicidal properties on four of the five-tested fungal species (Aspergillus niger, Cladosporium cladosporioides, Penicillium chrysogenum, and Penicillium corylophilum). No deleterious effects of 70% ethanol on the tested paper were observed either in the short or in the long term. 相似文献
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Leanne Lavina 《Journal of Early Childhood Teacher Education》2020,41(3):241-261
ABSTRACT Given that identity continually evolves within socio-cultural contexts of meaning, is there any perceived connectedness between place-based identity and the development of teacher identity? How might shifting personal and professional stories of experience influence teachers’ sense of place, whereby place is conceptualized through interconnected ways of living and working in time and place with others in early childhood contexts? In this ongoing Sydney-based project, six teachers working in prior-to-school (long day care) settings critically reflected on and represented their identity journeys across the professional experience. Using a new place-based framework for exploring identity development, teachers traced their encounters with the place(s), with multi-modal forms of representation and reflection supporting teachers’ re-examination of significant biography events and social-cultural locatedness. Using aesthetic ways of thinking and representing, this article provides insight into the place-based nature of early childhood teachers’ lives and work, illustrating the interwoven nature of teacher identity often formed “out of view”. Challenges associated with shifting personal and professional terrains are clarified, opening possibilities for renewal of pedagogies and transformation of identity understandings. 相似文献
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Many studies have shown that students of all school levels hold alternative conceptions that differ from the scientific conceptions transmitted by the school. These results raise some questions about the efficacy of traditional teaching and stress the need for using teaching strategies that explicitly take into account the alternative conceptions that students bring to the science classes. This issue has recently been raised and widely discussed throughout Portugal and the proposals for the new science syllabuses advise teachers to take it into account. However, the number of studies investigating both the teachers' attitudes towards this issue and the use of teaching strategies based on students' alternative conceptions is very limited. This article aims to present the results obtained from science teachers about their attitudes towards students' alternative conceptions and the use of teaching strategies based on these conceptions. The results may contribute to the planning of in-service courses. 相似文献
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The efficiency of a recently described non-aqueous method for paper deacidification using Ca(OH)2 nanoparticles in isopropanol was evaluated by pH and colorimetric measurements and by the analysis of the degree of polymerization (DP). Samples of plain paper and paper with iron gall ink were tested. The results were compared with non treated samples and samples submitted to the traditional treatment with saturated aqueous Ca(OH)2 solution. By comparing the two conservation methods, the aqueous one shows higher neutralization reaction kinetics than the non-aqueous one. The iron gall ink samples maintain their coloration closer to the original after the non-aqueous Ca(OH)2 nanoparticles treatment, in contrary to the aqueous treatment that changes the ink aesthetics considerably. Artificial aging tests revealed a general increase in the aging stability of deacidified paper samples. The Ca(OH)2 nanoparticles treatment can be an alternative for papers who can not be treated by the classical aqueous treatment, e.g. papers with water soluble components. 相似文献
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Research has shown that students’ alternative conceptions in science are quite resistent to change, which indicates that the teaching strategies used are not appropriate and that new strategies should be implemented in order to promote conceptual change. This pilot study was carried out with 100 Portuguese 5th grade students and aims: (a) to investigate a teaching strategy geared to the students’ conceptual change, taking into account their misconceptions about scientific ideas; (b) to promote a better attitude towards science. The results of this study indicate that the teaching approach based on the pupils’ alternative ideas and that makes them reflect on their own work and ideas, seemed to increase learning of scientific concepts related to the topic ‘properties and corpuscular model of the air’ and consequently favoured conceptual change better than a ‘traditional’ approach. 相似文献
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