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排序方式: 共有114条查询结果,搜索用时 15 毫秒
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Corrado De Francesco 《Higher Education》1978,7(2):193-212
The expansion of the Italian university system in the 1960s and 1970s is described with particular reference to the laws of 1961 and 1969 which liberalized access. The effects of these reforms are discussed and it is argued that despite the expansion the system remains an élite system. Admission to prestigious faculties and failure rates are correlated with social class to show that selection by failure within the university may to some extent have replaced selection at entry as a way of maintaining an élite system. Despite the increase in wastage there is a growing mismatch between the demand for and supply of graduate labour and this has given rise to social tensions. 相似文献
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While research outside economics has found that drinking has a negative effect on cognitive skills, some economists have failed to find any negative relationship between drinking and academic performance. This paper argues that the reason for this discrepancy is due to the way education is measured in the economic literature. Herein, binge drinking in the senior year of high school is found to reduce the probability of receiving a high school diploma and to increase the probability of graduating with a General Education Development (GED). Moreover, this study finds that alcohol policies do not affect the dropout rate measured at the age of 25, but they do affect the probability that a student will graduate on time. In conclusion, bingeing is found to be responsible for inducing individuals to temporarily drop out of school. Eventually, these individuals return to school to complete their education, most likely by obtaining a GED diploma. 相似文献
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Francesco Piraino ?eila Selimovi? Marco Adamo Alessandro Pero Sam Manoucheri Sang Bok Kim Danilo Demarchi Ali Khademhosseini 《Biomicrofluidics》2012,6(4)
The application of microfluidic technologies to stem cell research is of great interest to biologists and bioengineers. This is chiefly due to the intricate ability to control the cellular environment, the reduction of reagent volume, experimentation time and cost, and the high-throughput screening capabilities of microscale devices. Despite this importance, a simple-to-use microfluidic platform for studying the effects of growth factors on stem cell differentiation has not yet emerged. With this consideration, we have designed and characterized a microfluidic device that is easy to fabricate and operate, yet contains several functional elements. Our device is a simple polyester-based microfluidic chip capable of simultaneously screening multiple independent stem cell culture conditions. Generated by laser ablation and stacking of multiple layers of polyester film, this device integrates a 10 × 10 microwell array for cell culture with a continuous perfusion system and a non-linear concentration gradient generator. We performed numerical calculations to predict the gradient formation and calculate the shear stress acting on the cells inside the device. The device operation was validated by culturing murine embryonic stem cells inside the microwells for 5 days. Furthermore, we showed the ability to maintain the pluripotency of stem cell aggregates in response to concentrations of leukemia inhibitory factor ranging from 0 to ∼1000 U/ml. Given its simplicity, fast manufacturing method, scalability, and the cell-compatible nature of the device, it may be a useful platform for long-term stem cell culture and studies. 相似文献
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This study explores the channels through which technological investments affect productivity performance of industrialized economies. Using a Stochastic Frontier Model (SFM) we estimate the productivity effects of R&D and ICT for a large sample of OECD industries between 1973 and 2007, identifying four channels of transmission: input accumulation, technological change, technical efficiency and spillovers. Our results show that ICT has been particularly effective in reducing production inefficiency and in generating inter-industry spillovers, while R&D has raised the rate of technical change and favoured knowledge spillovers within sectors. We also quantify the contribution of technological investments to output and total factor productivity growth documenting that R&D and ICT accounted for almost 95% of productivity growth in the OECD area. 相似文献
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Query reformulation mining: models,patterns, and applications 总被引:1,自引:0,他引:1
Paolo Boldi Francesco Bonchi Carlos Castillo Sebastiano Vigna 《Information Retrieval》2011,14(3):257-289
Understanding query reformulation patterns is a key task towards next generation web search engines. If we can do that, then
we can build systems able to understand and possibly predict user intent, providing the needed assistance at the right time,
and thus helping users locate information more effectively and improving their web-search experience. As a step in this direction,
we build a very accurate model for classifying user query reformulations into broad classes (generalization, specialization,
error correction or parallel move), achieving 92% accuracy. We then apply the model to automatically label two very large
query logs sampled from different geographic areas, and containing a total of approximately 17 million query reformulations.
We study the resulting reformulation patterns, matching some results from previous studies performed on smaller manually annotated
datasets, and discovering new interesting reformulation patterns, including connections between reformulation types and topical
categories. We annotate two large query-flow graphs with reformulation type information, and run several graph-characterization
experiments on these graphs, extracting new insights about the relationships between the different query reformulation types.
Finally we study query recommendations based on short random walks on the query-flow graphs. Our experiments show that these
methods can match in precision, and often improve, recommendations based on query-click graphs, without the need of users’
clicks. Our experiments also show that it is important to consider transition-type labels on edges for having recommendations
of good quality. 相似文献
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