Are the new starting block facilities beneficial for backstroke start performance?     

Karla de Jesus  Kelly de Jesus  J. Arturo Abraldes  Alexandre Igor Araripe Medeiros  Ricardo J. Fernandes  João Paulo Vilas-Boas 《Journal of sports sciences》2016,34(9):871-877

We aimed to analyse the handgrip positioning and the wedge effects on the backstroke start performance and technique. Ten swimmers completed randomly eight 15 m backstroke starts (four with hands on highest horizontal and four on vertical handgrip) performed with and without wedge. One surface and one underwater camera recorded kinematic data. Standardised mean difference (SMD) and 95% confidence intervals (CI) were used. Handgrip positioning did not affect kinematics with and without wedge use. Handgrips horizontally positioned and feet over wedge displayed greater knee angular velocity than without it (SMD = ?0.82; 95% CI: ?1.56, ?0.08). Hands vertically positioned and feet over wedge presented greater take-off angle (SMD = ?0.81; 95% CI: ?1.55, ?0.07), centre of mass (CM) vertical positioning at first water contact (SMD = ?0.97; 95% CI: ?1.87, ?0.07) and CM vertical velocity at CM immersion (SMD = 1.03; 95% CI: 0.08, 1.98) when comparing without wedge use. Swimmers extended the hip previous to the knee and ankle joints, except for the variant with hands vertically positioned without wedge (SMD = 0.75; 95% CI: ?0.03, 1.53). Swimmers should preserve biomechanical advantages achieved during flight with variant with hands vertically positioned and wedge throughout entry and underwater phase.  相似文献   

Impact sports and bone fractures among adolescents     

Kyle R. Lynch  Han C. G. Kemper  Bruna Turi-Lynch  Ricardo R. Agostinete  Igor H. Ito  Rafael Luiz-De-Marco 《Journal of sports sciences》2017,35(24):2421-2426

The objective of the present study was to investigate the effects of different sports on stress fractures among adolescents during a 9-month follow-up period. The sample was composed of 184 adolescents divided into three groups (impact sports [n = 102]; swimming [n = 35]; non-sports [n = 47]). The occurrence of stress fracture was reported by participants and coaches. As potential confounders we considered age, sex, resistance training, body composition variables and age at peak of height velocity. There were 13 adolescents who reported fractures during the 9-month period. Bone mineral density values were higher in adolescents engaged in impact sports (P-value = 0.002). Independently of confounders, the risk of stress fracture was lower in adolescents engaged in impact sports than in non-active adolescents (hazard ratio [HR] = 0.23 [95% confidence interval (CI) = 0.05 to 0.98]), while swimming practice was not associated to lower risk of fracture (HR = 0.49 [95% CI = 0.09 to 2.55]). In conclusion, the findings from this study indicate the importance of sports participation among adolescents in the reduction of stress fracture risk, especially with impact sports. More importantly, these results could be relevant for recognising adolescents in danger of not reaching their potential for peak bone mass and later an increased risk of fractures.  相似文献   

Mathematics programmes: First aid     

Ricardo Losada Márquez  Mary Falk de Losada 《Prospects》1979,9(3):353-357

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An assessment of a social–cognitive model of academic performance in mathematics in Argentinean middle school students     

Marcos Cupani  María Cristina Richaud de Minzi  Edgardo Raúl Pérez  Ricardo Marcos Pautassi 《Learning and individual differences》2010,20(6):659-663

This study tested a set of hypotheses derived from the model of academic achievement in mathematics of the Social Cognitive Career Theory in a sample of Argentinean middle school students. To this aim, 277 students (male and female; age: 13–15 years) were assessed using the following instruments: logical–mathematical self-efficacy scale, mathematics outcome expectations, mathematics performance goals, and mathematics ability test. All of these instruments had been adapted for use in Argentinean students. Academic achievement in mathematics (i.e., grades obtained on regular school exams) was the variable to be modeled through the path analysis technique. The analysis allowed identification of interrelations among the variables and identification of direct and indirect effects. Academic achievement in mathematics was partially explained by the model. Overall, the results support the theoretical postulates of Social Cognitive Career Theory.  相似文献   

Adding Compression to Block Addressing Inverted Indexes   总被引：8，自引：1，他引：7  

Gonzalo Navarro  Edleno Silva de Moura  Marden Neubert  Nivio Ziviani  Ricardo Baeza-Yates 《Information Retrieval》2000,3(1):49-77

Inverted index compression, block addressing and sequential search on compressed text are three techniques that have been separately developed for efficient, low-overhead text retrieval. Modern text compression techniques can reduce the text to less than 30% of its size and allow searching it directly and faster than the uncompressed text. Inverted index compression obtains significant reduction of its original size at the same processing speed. Block addressing makes the inverted lists point to text blocks instead of exact positions and pay the reduction in space with some sequential text scanning.In this work we combine the three ideas in a single scheme. We present a compressed inverted file that indexes compressed text and uses block addressing. We consider different techniques to compress the index and study their performance with respect to the block size. We compare the index against three separate techniques for varying block sizes, showing that our index is superior to each isolated approach. For instance, with just 4% of extra space overhead the index has to scan less than 12% of the text for exact searches and about 20% allowing one error in the matches.  相似文献   

The Network Orientations of Highly Resilient Urban Minority Youth: A Network-Analytic Account of Minority Socialization and Its Educational Implications   总被引：1，自引：0，他引：1  

Ricardo D. Stanton-Salazar  Stephanie Urso Spina 《The Urban Review》2000,32(3):227-261

In this article the authors present a critical assessment of existing characterizations of resiliency and help-seeking behavior in light of their relevance to issues of minority youth socialization and schooling. In this effort, they reconceptualize the notion of resiliency within an analysis that highlights the more contextual aspects of how minority adolescent cope with structural forces that threaten healthy development. They show how key developmental transitions are thwarted by social forces that undermine the development of supportive relationships across multiple institutional sites (e.g., family, neighborhood, school). They also explain how resiliency is associated with egocentric networks that exhibit key structural characteristics. The authors conclude by discussing the implications of a critical network-analytic model of minority socialization in the development of future educational and youth mediations and reforms.  相似文献   

Validity of a portable force platform for assessing biomechanical parameters in three different tasks     

Ricardo Peterson Silveira  Pro Stergiou  Felipe P. Carpes  Flávio A. de S. Castro  Larry Katz  Darren J. Stefanyshyn 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(2):177-186

The aim of this study was to determine the precision and accuracy of the vertical and anterior–posterior force components of the portable PASCO PS-2142 force plate. Impulse, peak force, and time to peak force were assessed and compared to a gold standard force plate in three different tasks: vertical jump, forward jump, and sprint start. Two healthy male participants performed ten trials for each task, resulting in 60 trials. Data analyses revealed good precision and accuracy for the vertical component of the portable force plate, with relative bias and root mean square (RMS) error values nearly the same in all tasks for the impulse, time to peak force, and peak force parameters. Precision and accuracy of the anterior–posterior component were lower for the impulse and time to peak force, with relative bias and RMS error values nearly the same between tasks. Despite the lower precision and accuracy of the anterior–posterior component of the portable force plate, these errors were systematic, reflecting a good repeatability of the measure. In addition, all variables presented good agreement between the portable and gold standard platforms. Our results provide a good perspective for using the aforementioned portable force plate in sports and clinical biomechanics.  相似文献   

University Efficiency: Complementariness versus Trade‐off between Teaching,Research and Administrative Activities     

Ricardo Sellers‐Rubio  Francisco J. Mas‐Ruiz  Ana B. Casado‐Díaz 《Higher Education Quarterly》2010,64(4):373-391

University managers should be aware of the importance that efficiency has for their own universities, orientating their actions towards research and teaching excellence. This study estimates teaching and research efficiency of the different departments of a university and tests the complementariness versus trade‐off between them. The results obtained show high levels of efficiency for the departments analysed, which is important for budget allocation, as one of the main challenges faced by a university is the allocation of budgets to different departments. The results also support the trade‐off between teaching efficiency and research activity, the complementariness between teaching efficiency and research efficiency, between research efficiency and time deducted from teaching, as well as the complementariness between research efficiency and administration activity.  相似文献   

Design principles for creating digital transparency in government     

Ricardo Matheus  Marijn Janssen  Tomasz Janowski 《Government Information Quarterly》2021,38(1):101550

Under pressure to fight corruption, hold public officials accountable, and build trust with citizens, many governments pursue the quest for greater transparency. They publish data about their internal operations, externalize decision-making processes, establish digital inquiry lines to public officials, and employ other forms of transparency using digital means. Despite the presence of many transparency-enhancing digital tools, putting such tools together to achieve the desired level of digital transparency, to design entire government systems for digital transparency, remains challenging. Design principles and other design guides are lacking in this area. This article aims to fill this gap. We identify a set of barriers to digital transparency in government, define 16 design principles to overcome such barriers, and evaluate these principles using three case studies from different countries. Some principles apply to projects, others to systems, yet others to entire organizations. To achieve digital transparency, before building and deploying digital solutions, government organizations should build technological and institutional foundations and use such foundations to organize themselves for transparency. The proposed design principles can help develop and apply such foundations.  相似文献   

Providing knowledge recommendations: an approach for informal electronic mentoring     

Ricardo Colomo-Palacios  Cristina Casado-Lumbreras  Pedro Soto-Acosta  Sanjay Misra 《Interactive Learning Environments》2014,22(2):221-240

The use of Web 2.0 technologies for knowledge management is invading the corporate sphere. The Web 2.0 is the most adopted knowledge transfer tool within knowledge intensive firms and is starting to be used for mentoring. This paper presents IM-TAG, a Web 2.0 tool, based on semantic technologies, for informal mentoring. The tool offers recommendations of mentoring contents built upon personal competencies of the mentee, combined with content and opinion tagging. To validate the tool, a case study comparing recommendations from the IM-TAG and a group of experts was conducted. Results show that the accuracy of IM-TAG's recommendations is notable and satisfactory. The main conclusions of this research may be valuable to organizations immersed in mentoring programs.  相似文献