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61.
Venture capital financing and the growth of high-tech start-ups: Disentangling treatment from selection effects 总被引:3,自引:0,他引:3
The financial and innovation literature generally claims that venture capital (VC) investments spur the growth of new technology-based firms (NTBFs). However, it has proved difficult so far to separate the “treatment” effect of the VC investment from the “selection” effect attributable to the ability of the VC investor to screen high growth NTBFs. The aim of this work is to test whether VC investments have a positive treatment effect on the growth of employment and sales of NTBFs. For this purpose we consider a 10-year longitudinal data set for 538 Italian NTBFs, most of which are privately held. The sample includes both VC-backed and non-VC-backed firms. We estimate Gibrat-law-type dynamic panel-data models augmented with time-varying variables that capture the VC status of firms. To control for the endogeneity of VC investments we use several GMM estimators. The econometric results strongly support the view that VC investments positively influence firm growth. The treatment effect of VC investments is of large economic magnitude, especially on growth of employment. Most of it is obtained immediately after the first round of VC finance. Conversely, the selection effect of VC appears to be negligible in the Italian context. 相似文献
62.
Collection selection is a crucial function, central to the effectiveness and efficiency of a federated information retrieval
system. A variety of solutions have been proposed for collection selection adapting proven techniques used in centralised
retrieval. This paper defines a new approach to collection selection that models the topical distribution in each collection.
We describe an extended version of latent Dirichlet allocation that uses a hierarchical hyperprior to enable the different
topical distributions found in each collection to be modelled. Under the model, resources are ranked based on the topical
relationship between query and collection. By modelling collections in a low dimensional topic space, we can implicitly smooth
their term-based characterisation with appropriate terms from topically related samples, thereby dealing with the problem
of missing vocabulary within the samples. An important advantage of adopting this hierarchical model over current approaches
is that the model generalises well to unseen documents given small samples of each collection. The latent structure of each
collection can therefore be estimated well despite imperfect information for each collection such as sampled documents obtained
through query-based sampling. Experiments demonstrate that this new, fully integrated topical model is more robust than current
state of the art collection selection algorithms. 相似文献
63.
Biscarini A Benvenuti P Botti F Mastrandrea F Zanuso S 《Journal of sports sciences》2011,29(5):457-469
An analytical biomechanical model was developed to establish the relevant properties of the Smith squat exercise, and the main differences from the free barbell squat. The Smith squat may be largely patterned to modulate the distributions of muscle activities and joint loadings. For a given value of the included knee angle (θ(knee)), bending the trunk forward, moving the feet forward in front of the knees, and displacing the weight distribution towards the forefoot emphasizes hip and lumbosacral torques, while also reducing knee torque and compressive tibiofemoral and patellofemoral forces (and vice versa). The tibiofemoral shear force φ(t) displays more complex trends that strongly depend on θ(knee). Notably, for 180° ≥ θ(knee) ≥ 130°, φ(t) and cruciate ligament strain forces can be suppressed by selecting proper pairs of ankle and hip angles. Loading of the posterior cruciate ligament increases (decreases) in the range 180° ≥ θ(knee) ≥ 150° (θ(knee) ≤ 130°) with knee extension, bending the trunk forward, and moving the feet forward in front of the knees. In the range 150° > θ(knee) > 130°, the behaviour changes depending on the foot weight distribution. The conditions for the development of anterior cruciate ligament strain forces are explained. This work enables careful use of the Smith squat in strengthening and rehabilitation programmes. 相似文献
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Fabio Alivernini Elisa Cavicchiolo Laura Girelli Valeria Biasi Fabio Lucidi 《The Journal of educational research》2018,111(5):603-611
In the study, based on a representative sample of 26,670 Italian fifth-grade students, the authors examine the academic motivational profiles of immigrant and native students, as well as of boys and girls. To reliably estimate mean differences, the measurement invariance of a short version of the Academic Self-Regulation Questionnaire was first established across the groups. Boys reported less autonomous motives for studying than girls while first-generation immigrant pupils showed higher levels of intrinsic motivation, identified regulation, and external regulation for studying than natives did. Also, second-generation immigrants had higher levels of academic motivation than natives did, although they were less motivated and reported less autonomous reasons for studying than first generations. While confirming the immigrant paradox in a country with a rapidly increasing level of immigrant students, findings show that second-generation immigrants not only report a lower quantity of motivation than first-generations, but also appear to have a different quality of motivation. 相似文献
68.
This paper addresses the blog distillation problem, that is, given a user query find the blogs that are most related to the query topic. We model each post as evidence of the relevance of a blog to the query, and use aggregation methods like Ordered Weighted Averaging (OWA) operators to combine the evidence. We show that using only highly relevant evidence (posts) for each blog can result in an effective retrieval system. We also take into account the importance of the posts in a query-based cluster and investigate its effect in the aggregation results. We use prioritized OWA operators and show that considering the importance is effective when the number of aggregated posts from each blog is high. We carry out our experiments on three different data sets (TREC07, TREC08 and TREC09) and show statistically significant improvements over state of the art model called voting model. 相似文献
69.
Nasrin Mohammadhasani Hashem Fardanesh Javad Hatami Naser Mozayani Rosa Angela Fabio 《Education and Information Technologies》2018,23(6):2299-2308
Gaining the attention is the first key step to enhance learning. In Attention-Deficit/Hyperactivity Disorder (ADHD) as the most prevalent deficit in school age, the learners face some impairment in attention that requires appropriate intervention. An environment that embedded Pedagogical Agent in computer-assisted instruction (CAI) has been designed to support learning through gaining and guiding attention to relevant information for these students. This study investigated how much the presence of pedagogical agent can improve learning in ADHD students. The learning environment was integrated with a pedagogical agent, named Koosha, as a tutor and motivator. This study employed a pretest and posttest experimental design with a control group. The statistical population was 30 boy students with ADHD in primary school from the North of Iran. The participants were randomly assigned to work with either an agent presenting a multimedia program or without an agent in mathematics. The results (Analysis of covariance -ANCOVA) suggested that experimental and control groups show a significant difference in mathematics achievement. According to this research, using the pedagogical agent can enhance the learning of ADHD students; so it can be considered as a valid school-base intervention for these students. 相似文献
70.
In Italy, the Regular Grant is the most important subsidy to private cultural institutions. Since 1996, law 534/96 has regulated its provision. This law greatly improves on the previous legislation, as it redefines the prerequisites to become a recipient and specifies performance indicators to which the size of the grant must be tied. This paper examines the effects of the introduction of the new law, the characteristics of the government choice process and the redistribution profile of these grants using a variety of estimating techniques on official data gathered for the purpose. 相似文献