The Market for Picasso Prints: A Hybrid Model Approach     

Marilena?Locatelli?BieyEmail author  Roberto?Zanola 《Journal of Cultural Economics》2005,29(2):127-136

Two basic approaches have been used by the literature focusing on the return to holding artistic works: the hedonic price model and the repeat-sales model. This paper provides a procedure for jointly estimating the two models in a way that take advantages of the unique information contained in each. A semiannual price index for Picasso prints is estimated by using a model derived from the basic framework of the hybrid models. The empirical results suggest that the hybrid model provides the most precisely estimated price index by reducing the level of price volatility.JEL Classification: C5, Z1p  相似文献   

Open and Non‐formal Education: new paths for education in a new Europe     

José Luis García Garrido 《比较教育学》1992,28(1):83-89

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A tapered channel microfluidic device for comprehensive cell adhesion analysis, using measurements of detachment kinetics and shear stress-dependent motion     

Rupprecht P  Golé L  Rieu JP  Vézy C  Ferrigno R  Mertani HC  Rivière C 《Biomicrofluidics》2012,6(1):14107-1410712

We have developed a method for studying cellular adhesion by using a custom-designed microfluidic device with parallel non-connected tapered channels. The design enables investigation of cellular responses to a large range of shear stress (ratio of 25) with a single input flow-rate. For each shear stress, a large number of cells are analyzed (500–1500 cells), providing statistically relevant data within a single experiment. Besides adhesion strength measurements, the microsystem presented in this paper enables in-depth analysis of cell detachment kinetics by real-time videomicroscopy. It offers the possibility to analyze adhesion-associated processes, such as migration or cell shape change, within the same experiment. To show the versatility of our device, we examined quantitatively cell adhesion by analyzing kinetics, adhesive strength and migration behaviour or cell shape modifications of the unicellular model cell organism Dictyostelium discoideum at 21 °C and of the human breast cancer cell line MDA-MB-231 at 37 °C. For both cell types, we found that the threshold stresses, which are necessary to detach the cells, follow lognormal distributions, and that the detachment process follows first order kinetics. In addition, for particular conditions’ cells are found to exhibit similar adhesion threshold stresses, but very different detachment kinetics, revealing the importance of dynamics analysis to fully describe cell adhesion. With its rapid implementation and potential for parallel sample processing, such microsystem offers a highly controllable platform for exploring cell adhesion characteristics in a large set of environmental conditions and cell types, and could have wide applications across cell biology, tissue engineering, and cell screening.  相似文献   

Influence of regression model and incremental test protocol on the relationship between lactate threshold using the maximal-deviation method and performance in female runners     

Machado FA  Nakamura FY  Moraes SM 《Journal of sports sciences》2012,30(12):1267-1274

This study examined the influence of the regression model and initial intensity of an incremental test on the relationship between the lactate threshold estimated by the maximal-deviation method and the endurance performance. Sixteen non-competitive, recreational female runners performed a discontinuous incremental treadmill test. The initial speed was set at 7 km · h?1, and increased every 3 min by 1 km · h?1 with a 30-s rest between the stages used for earlobe capillary blood sample collection. Lactate-speed data were fitted by an exponential-plus-constant and a third-order polynomial equation. The lactate threshold was determined for both regression equations, using all the coordinates, excluding the first and excluding the first and second initial points. Mean speed of a 10-km road race was the performance index (3.04 ± 0.22 m · s?1). The exponentially-derived lactate threshold had a higher correlation (0.98 ≤ r ≤ 0.99) and smaller standard error of estimate (SEE) (0.04 ≤ SEE ≤ 0.05 m · s?1) with performance than the polynomially-derived equivalent (0.83 ≤ r ≤ 0.89; 0.10 ≤ SEE ≤ 0.13 m · s?1). The exponential lactate threshold was greater than the polynomial equivalent (P < 0.05). The results suggest that the exponential lactate threshold is a valid performance index that is independent of the initial intensity of the incremental test and better than the polynomial equivalent.  相似文献   

Differences between web sessions according to the origin of their visits     

José Luis Ortega  Isidro Aguillo 《Journal of Informetrics》2010,4(3):331-337

The aim of this paper is to characterize the distribution of number of hits and spent time by web session. It also expects to find if there are significant differences between the length and the duration of a session with regard to the point of access–search engine, link or root. Web usage mining was used to analyse 17,174 web sessions that were identified from the webometrics.info web site. Results show that both distribution of length and duration follow an exponential decay. Significant differences between the different origins of the visits were also found, being the search engines’ users those who spent most time and did more clicks in their sessions. We conclude that a good SEO policy would be justified, because search engines are the principal intermediaries to this web site.  相似文献   

Training and psychosocial patterns during the early development of Portuguese national team athletes     

André Barreiros  Jean Côté  António Manuel Fonseca 《High Ability Studies》2013,24(1):49-61

This study explored the early development of expert athletes compared to a group of athletes that did not achieve an expert level of performance despite being involved in youth events with their national squads. In particular, the activities, training patterns, and psychosocial influences that characterized their paths in competitive sports were examined. Male and female participants (N?=?42) from different sports were interviewed. Overall, athletes showed several commonalities. However, experts were selected to national squads later and also started thinking about investing in becoming elite athletes later. Non-experts revealed more parental pressure and less individual training with coaches.  相似文献   

Mentoring Matters: An Exploratory Survey of Educational Leadership Doctoral Students’ Perspectives     

Anjalé D. Welton  Katherine Cumings Mansfield  Pei-Ling Lee 《Mentoring & Tutoring: Partnership in Learning》2013,21(5):481-509

There is limited research on quantitative differences between men and women’s experiences in doctoral programs. We aim to fill that gap by sharing findings from a web-based exploratory survey of perceived gender differences on quality mentoring in educational leadership doctoral programs. According to survey results, there is limited statistical significance in terms of gender differences in programmatic supports and scholarly progress. However, women experience feelings of self-doubt due to negative experiences with advising and mentoring, including difficulties making connections to a quality mentor. Furthermore, both female and male participants shared common definitions of what constitutes quality mentorship and believed mentorship was important, but lacking in varying degrees. Finally, all participants agreed that their educational leadership preparation programs should provide additional support in terms of writing and research development. Participants also shared important recommendations for strengthening mentoring experiences as well as future research methods and foci.  相似文献   

Effects of a Cooperative Learning Program on the Elaborations of Students Working in Dyads     

Karen Krol  Jeroen Janssen  Simon Veenman  Jos van der Linden 《Educational Research and Evaluation》2013,19(3):205-237

In this study, the effects of a school improvement program on cooperative learning (CL) with respect to the elaborations of 6th-grade students working in mixed-ability and mixed-sex dyads on 2 cooperative tasks were examined. A posttest-only design with a control group was used to investigate the provision and receipt of elaborations within the dyads and the performance of the dyads working on cooperative mathematics and language tasks. Treatment dyads were found to exchange significantly more high-level elaborations during the language task than the control dyads. The treatment dyads also tended to produce higher performance scores on the 2 tasks.  相似文献   

Responsive Instruction for Young Children: A Study of how teachers can help easily distracted children become more attentive     

Jos H. M. Castelijns 《Emotional and Behavioural Difficulties》2013,18(1):22-33

In a research and development project called ‘orthopedagogisch project Afstemming’, conducted at the Utrecht University, a programme for teachers in kindergarten is designed and evaluated. It's goal is enhancing children's motivation and attention for work and play by means of responsive Instruction.  相似文献   

Learning by starch potato growers: learning in small businesses with no employees     

Niels R. Faber  Laura Maruster  René J. Jorna  Rob J.F. van Haren 《Educational Research and Evaluation》2013,19(6):519-539

In small businesses with no employees, learning environments have a low learning readiness. Consequently, learners need to rely on their own agency to shape their learning experiences. Results from a study of agricultural entrepreneurs indicated that the components of motivation and self-regulated learning strategies shape learner's agency and explain learning environment configuration in small businesses with no employees. Configuration of the learning environment was found to be a weak determinant of the learning performance of these learners. However, results showed that prior performance of learners in small businesses with no employees dictates how their agency operates and what learning effect is achieved; higher prior performance results in higher learning effects. We conclude that mechanisms that underlie learning in traditional learning environments work similarly in learning environments in small businesses with no employees.  相似文献