The relationship of anxiety in children to performance in a complex learning task     

CASTANEDA A  MCCANDLESS BR  PALERMO DS 《Child development》1956,27(3):333-337

  相似文献   

Research Policy In Emerging Economies: Brazil’s Sector Funds     

Creso?SáEmail author 《Minerva》2005,43(3):245-263

This paper examines Brazil’s Sector Funds, an emerging research and development policy that seeks to increase public-private research collaboration. The first section sets the context of the ‘policy problem’. The second section discusses the policy’s implementation, and discusses its likely implications for Brazil and beyond.  相似文献   

Rank-Stability and Rank-Similarity of Link-Based Web Ranking Algorithms in Authority-Connected Graphs     

R.?Lempel  S.?MoranEmail author 《Information Retrieval》2005,8(2):245-264

Web search algorithms that rank Web pages by examining the link structure of the Web are attractive from both theoretical and practical aspects. Todays prevailing link-based ranking algorithms rank Web pages by using the dominant eigenvector of certain matrices—like the co-citation matrix or variations thereof. Recent analyses of ranking algorithms have focused attention on the case where the corresponding matrices are irreducible, thus avoiding singularities of reducible matrices. Consequently, rank analysis has been concentrated on authority connected graphs, which are graphs whose co-citation matrix is irreducible (after deleting zero rows and columns). Such graphs conceptually correspond to thematically related collections, in which most pages pertain to a single, dominant topic of interest.A link-based search algorithm A is rank-stable if minor changes in the link structure of the input graph, which is usually a subgraph of the Web, do not affect the ranking it produces; algorithms A,B are rank-similar if they produce similar rankings. These concepts were introduced and studied recently for various existing search algorithms.This paper studies the rank-stability and rank-similarity of three link-based ranking algorithms—PageRank, HITS and SALSA—in authority connected graphs. For this class of graphs, we show that neither HITS nor PageRank is rank stable. We then show that HITS and PageRank are not rank similar on this class, nor is any of them rank similar to SALSA.This research was supported by the Fund for the Promotion of Research at the Technion, and by the Barnard Elkin Chair in Computer Science.  相似文献   

Guest Editorial: Spaces,Logic, and Link Analysis in IR: Recent Advances From A Mathematical and Logical Perspective   总被引：1，自引：0，他引：1  

Sándor?DominichEmail author  Mounia?Lalmas  Cornelius?Joost ?van?Rijsbergen 《Information Retrieval》2005,8(2):175-179

  相似文献   

Communications to the editor     

Brodman E  Cohen GS 《Bulletin of the Medical Library Association》1966,54(3):259-260

  相似文献   

Modulation of an activity response with associative and nonassociative fear in the rat: A lighting differential influences the form of defensive behavior evoked after fear conditioning     

Godsil BP  Blackmore MA  Fanselow MS 《Learning & behavior》2005,33(4):454-463

Rats confronted with the onset of a light gradient display a transient increase in locomotion called theactivity response (AR) and a dark preference (Godsil & Fanselow, 2004). These experiments demonstrate that the magnitude of the AR can be blunted with Pavlovian fear-conditioning procedures via associative and nonassociative fear. Although manifested in decreased locomotion, the blunted AR effect was not due to increased freezing or immobility behaviors. Instead, rats displayed reduced rearing and an increase in a class of behaviors calledstationary activity. These results suggest that the lighting differential supplied by the cue influences the topography of defensive behavior and reduces the expression of freezing. This procedure provides a means by which to examine learned and unlearned defensive responses to the same stimulus.  相似文献   

The relationship between qualified personnel and self-reported implementation of recommended physical education practices and programs in U.S. schools     

Davis KS  Burgeson CR  Brener ND  McManus T  Wechsler H 《Research quarterly for exercise and sport》2005,76(2):202-211

The authors analyzed data from the School Health Policies and Programs Study 2000 to assess the associations between the presence of a district physical education coordinator and district-level physical education policies and practices recommended by federal government agencies and national organizations. The authors also examined the relationship between teacher qualifications and staff development related to physical education and self-reported implementation of recommended teachingpractices. District-level data were collected by self-administered mail questionnaires from a nationally representative sample of school districts. Classroom-level data were collected by computer-assisted personal interviews with teachers of randomly selected classes in elementary schools and randomly selected required physical education courses in middle/junior high and senior high schools. Nearly two thirds (62.2%) of districts had a physical education coordinator, and those were generally more likely than other districts to report having policies and practices that corresponded with national recommendations for high-quality physical education programs. More than two thirds of teachers (66.9%) met the criteria for teacher qualifications based on their education and certification. These teachers were more likely than others to report use of certain recommended physical education teaching practices. Teachers who participated in staff development also were more likely to use recommended teaching practices in their classrooms. Using a district physical education coordinator and teachers with appropriate qualifications as well as offering staff development opportunities on physical education may enhance school physical education programs.  相似文献   

Timing of ball release in overarm throws affects ball speed in unskilled but not skilled individuals     

Jegede E  Watts S  Stitt L  Hore J 《Journal of sports sciences》2005,23(8):805-816

We tested the hypothesis that variability in the timing of ball release in overarm throws affects ball speed. Nine unskilled and six skilled throwers made 30 throws fast and accurately from a sitting and standing position. Angular positions of finger and arm segments were recorded with search-coils at 1000 Hz; ball speed was measured with a radar gun. The time of ball release from the fingertips was measured with respect to seven arm kinematic reference points. Mean timing windows for ball release were 28 ms for unskilled throwers and 7 ms for skilled throwers. Mixed-model analyses of variance showed that a there was a statistically significant relationship between ball speed and the timing of ball release in unskilled throwers, but not in skilled throwers. This was presumably due to the difference in variability of the timing of ball release between the two groups. In contrast, skilled throwers showed a relationship between ball speed and peak forearm angular velocity (one measure of arm speed). We conclude that although variability in the timing of ball release can affect ball speed, this is only a major factor in unskilled throwers. When skilled throwers throw fast, variability in ball speed is due to variability in arm speed.  相似文献   

Effects of adding a preceding run-up on performance, blood lactate concentration and heart rate during maximal intermittent vertical jumping     

Hertogh C  Chamari K  Damiani M  Martin R  Hachana Y  Blonc S  Hue O 《Journal of sports sciences》2005,23(9):937-942

In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( +/- ) jump performance (64.7 +/- 2.3 cm) increased significantly (P = 0.02) over the course of the jump condition and was significantly higher (P < 0.001) than for the run-up plus jump condition (58.0 +/- 3.2 cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 +/- 0.24 mmol . l(-1)) than in the jump (2.61 +/- 0.26 mmol . l(-1), P = 0.02) and run-up (2.86 +/- 0.18 mmol . l(-1), P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 +/- 6 beats . min(-1), P = 0.05) and run-up condition (33 +/- 4 beats . min(-1), P = 0.02) than in the jump condition (21 +/- 3 beats . min(-1)). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps.  相似文献   

Optimum take-off angle in the long jump     

Linthorne NP  Guzman MS  Bridgett LA 《Journal of sports sciences》2005,23(7):703-712

In this study, we found that the optimum take-off angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the measured relations between take-off speed, take-off height and take-off angle for the athlete. The prediction method was evaluated using video measurements of three experienced male long jumpers who performed maximum-effort jumps over a wide range of take-off angles. To produce low take-off angles the athletes used a long and fast run-up, whereas higher take-off angles were produced using a progressively shorter and slower run-up. For all three athletes, the take-off speed decreased and the take-off height increased as the athlete jumped with a higher take-off angle. The calculated optimum take-off angles were in good agreement with the athletes' competition take-off angles.  相似文献