Enhancing teager energy operator based on a novel and appealing concept: Signal mass     

Rodrigo Capobianco Guido 《Journal of The Franklin Institute》2019,356(4):2346-2352

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Using matrix norms to estimate the direction of arrival of planar waves on an ULA     

Rodrigo P. Lemos  Jonas A. Kunzler  Diego F. Burgos B.  Mário J. de Souza  Hugo V. L. e Silva  Yroá R. Ferreira  Edna L. Flôres  Oliver Sander 《Journal of The Franklin Institute》2019,356(6):3781-3796

SEAD method estimates the direction-of-arrival angles on an uniformly linear array based on the difference between the two largest singular values, what is called differential spectrum. Although it presented an outstanding performance, the ability to indicate the source positions was not elucidated yet. Inspired by the differential spectrum formulation we derived a total differential spectrum and found out that the matrix norm induced by the vector 2-norm of a modified spatial covariance matrix can be used to estimate the direction-of-arrival of multiple plane waves. Indeed we show that matrix norms are estimators and we propose their use instead of the singular value decomposition in SEAD-based methods. We present a general mathematical expression in order to explicit the operating principles of the proposed methods. Consequently, we were able to explain how the relation between the arriving and the search angles produces the larger peaks on the differential spectrum. To evaluate the important role played by matrix norms, a thousand experiments were carried out. They showed that the proposed approach proved to be as accurate as the previous SEAD-based methods, while providing a significant reduction on runtime. It also outperformed well-established methods like MODEX regarding the estimation error.  相似文献   

Effects of mild running on substantia nigra during early neurodegeneration     

Michael F. Almeida  Carolliny M. Silva  Rodrigo S. Chaves  Nathan C. R. Lima  Renato S. Almeida  Karla P. Melo 《Journal of sports sciences》2018,36(12):1363-1370

Moderate physical exercise acts at molecular and behavioural levels, such as interfering in neuroplasticity, cell death, neurogenesis, cognition and motor functions. Therefore, the aim of this study is to analyse the cellular effects of moderate treadmill running upon substantia nigra during early neurodegeneration. Aged male Lewis rats (9-month-old) were exposed to rotenone 1mg/kg/day (8 weeks) and 6 weeks of moderate treadmill running, beginning 4 weeks after rotenone exposure. Substantia nigra was extracted and submitted to proteasome and antioxidant enzymes activities, hydrogen peroxide levels and Western blot to evaluate tyrosine hydroxylase (TH), alpha-synuclein, Tom-20, PINK1, TrkB, SLP1, CRMP-2, Rab-27b, LC3II and Beclin-1 level. It was demonstrated that moderate treadmill running, practiced during early neurodegeneration, prevented the increase of alpha-synuclein and maintained the levels of TH unaltered in substantia nigra of aged rats. Physical exercise also stimulated autophagy and prevented impairment of mitophagy, but decreased proteasome activity in rotenone-exposed aged rats. Physical activity also prevented H₂O₂ increase during early neurodegeneration, although the involved mechanism remains to be elucidated. TrkB levels and its anterograde trafficking seem not to be influenced by moderate treadmill running. In conclusion, moderate physical training could prevent early neurodegeneration in substantia nigra through the improvement of autophagy and mitophagy.  相似文献   

Eccentric flywheel post-activation potentiation influences swimming start performance kinetics     

Francisco Cuenca-Fernández  Gracia López-Contreras  Luis Mourão  Karla de Jesus  Kelly de Jesus  Rodrigo Zacca 《Journal of sports sciences》2019,37(4):443-451

This study aimed to assess the effects of post-activation potentiation in the strength related variables of a kick start. Thirteen competitive swimmers performed three kick starts after a standardized warm up (denoted USUAL) and another after inducing post-activation through five isotonic repetitions on an eccentric flywheel (denoted PAP). A T-test was used to quantify differences between USUAL and PAP warm up. The best trial of each subject achieved by natural conditions (denoted PEAK) was compared with data obtained after PAP. An instrumented starting block with independent triaxial force plates, collected the strength variables related with the impulse at take off. Improvements in the vertical components of force were observed after PAP compared with USUAL, meanwhile no differences were detected on the horizontal components of it. The velocity at take off was higher after PAP compared with USUAL (4.32 ± 0.88 vs 3.93 ± 0.60 m*s-1; p = 0.02). No differences in force or velocity were detected comparing PAP with PEAK (4.13 ± 0.62 m*s-1, p = 0.11). The PAP warm-up increased vertical force and it was transferred to a higher resultant velocity at take-off. This improvement would equal the best result possible obtained in natural conditions after some trials.  相似文献   

Effects of detraining in age-group swimmers performance,energetics and kinematics     

Rodrigo Zacca  Argyris Toubekis  Laura Freitas  Ana Filipa Silva  Rui Azevedo  João Paulo Vilas-Boas 《Journal of sports sciences》2019,37(13):1490-1498

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“ʿAlā fūr Tuṭīla”: Jews and Muslims in the Administrative Culture of Post-Conquest Tudela,c.1118–1220     

Rodrigo García-Velasco Bernal 《Al-Masaq: Islam & the Medieval Mediterranean》2017,29(3):235-257

The early history of the Jewish and Muslim communities living under Christian rule in the Ebro Valleys tends to be overlooked in favour of the source-rich thirteenth and fourteenth centuries. However, the nature and organisation of these groups should not be taken as a constant, as they underwent a significant transformation over the course of the twelfth century. Through the case study of Tudela, this article proposes to re-examine the dynamics of administration and judicial practice that developed in the immediate aftermath of the Navarro-Aragonese conquest. This town has a rich corpus of charters that allows us to contrast the administrative layout enshrined in the franchise charters known as fueros with the legal practice reflected in some particular bilingual interlineated purchase-sale contracts. A comparison of both sets of documents emphasises the use of the fuero in inter-communal negotiation, both in framing encounters and in guaranteeing each group's autonomy, during a key period in the gestation of Jewish and Muslim administrative and judicial practices under Christian rule.

Abbreviations: DAr = Mercedes García-Arenal, “Documentos árabes de Tudela Y Tarazona”, Al-Qan?ara: Revista de Estudios Árabes 3 (1982): 27–72; FdN = Luis Javier Fortún Pérez de Ciriza, “Colección de ‘fueros menores’ de Navarra y otros privilegios locales (I)”, Príncipe de Viana 165 (1982): 273–348  相似文献   

Effects of distinct practice conditions on the learning of the o soto gari throwing technique of judo     

Fábio Rodrigo Ferreira Gomes  Flavio Henrique Bastos  Cássio de Miranda Meira Jr.  Jaqueline Freitas de Oliveira Neiva  Go Tani 《Journal of sports sciences》2017,35(6):572-578

The aim of this study was to investigate the effects of different types of practice on learning the o soto gari, focusing on the kuzushi (unbalancing the opponent). A total of 64 children (mean age 9.19 ± 1.41 years) were assigned to one of four groups: (1) static traditional practice, i.e., uchikomi – repetition of the moving pattern that characterises the technique up to the point of throwing; (2) in motion traditional practice – uchikomi with the tori (player executing the technique) moving/walking; (3) whole practice with pre-kuzushi – full technique with a preparatory component for kuzushi; (4) progressive parts practice with pre-kuzushi – progressively introducing kuzushi, tsukuri (set-up to execute the technique) and kake (final part of the technique; projection) with pre-kuzushi. Pre-test, acquisition, post-test and retention test were carried out. Movements were video recorded and analysed regarding three aspects: global technique of the tori, occurrence of a movement pattern performed by the tori to unbalance the uke (player receiving the “attack”), and occurrence of actual unbalance (kuzushi). Results showed no significant differences between-groups. However, different within-groups improvements suggest that using a uchikomi with pre-kuzushi can help learners deal with the motor actions of pulling and pushing in order to unbalance the opponent.  相似文献   

Effectiveness of pedalling retraining in reducing bilateral pedal force asymmetries     

Rodrigo R. Bini  Tiago C. Jacques  Felipe P. Carpes  Marco A. Vaz 《Journal of sports sciences》2017,35(14):1336-1341

ABSTRACT

Previous studies have been limited to describe asymmetries during pedalling and suggest possible repercussion on performance and/or injury risks. However, few studies have presented strategies to mitigate asymmetries. The purpose of this study was to assess the effectiveness of a pedalling retraining intervention to reduce bilateral pedal force asymmetries. Twenty cyclists were assessed and 10 enrolled in a pedalling retraining method receiving visual and verbal feedback of pedal forces. The asymmetry index was computed for comparison of bilateral peak pedal forces and used during retraining (12 trials at 70% of peak power). Significantly larger asymmetry was observed for asymmetrical cyclists at the first three trials (P < 0.01 and ES = 1.39), which was reduced when post-retraining was compared to measures from symmetrical cyclists (P = 0.69 and ES = 0.18). Cyclists with larger asymmetry (>20%) in bilateral pedal forces reduce their asymmetries using sessions of pedalling retraining and achieve asymmetry indices similar to symmetrical cyclists.  相似文献   

Exploring an activist approach of working with boys from socially vulnerable backgrounds in a sport context     

Carla Luguetti  Kimberly L. Oliver  David Kirk  Luiz Dantas 《Sport, Education and Society》2017,22(4):493-510

This study explores an activist approach for co-creating a prototype pedagogical model of sport for working with boys from socially vulnerable backgrounds. This paper addresses the key features that emerged when we identified what facilitated and hindered the boys’ engagement in sport. This study was an activist research project that was conducted between July 2013 and December 2013 in a soccer program in a socially and economically disadvantaged neighborhood in Brazil. The lead author, supervised by the second author, worked with a soccer class of 17 boys between ages 13 and 15, 4 coaches, a pedagogical coordinator and a social worker. Multiple sources of data were collected, including 38 field journal/observations and audio records of: 18 youth work sessions, 16 coaches’ work sessions and 3 combined coaches and youth work sessions. In addition, the first and second author had 36 90-minute debriefing and planning sessions. By using an activist approach, three features were identified as being essential: an ethic of care, an attentiveness to the community and a community of sport. Findings suggest that it is possible to use sport as a cultural asset to benefit youth from socially vulnerable backgrounds by offering them a place where they can feel protected and dream about possible futures.  相似文献   

Effects of antagonist pre-load on knee extensor isokinetic muscle performance     

Carregaro RL  Gentil P  Brown LE  Pinto RS  Bottaro M 《Journal of sports sciences》2011,29(3):271-278

The aim of this study was to evaluate and compare acute effects of a reciprocal action protocol and a super-set protocol on knee extensor performance during concentric isokinetic exercise. Fourteen men aged 29.4 ± 6.1 years were tested on three different protocols, with 1 min of rest between sets: control (3 sets of 10 isokinetic knee extension repetitions), reciprocal action protocol (3 sets of 10 repetitions of reciprocal isokinetic concentric knee flexion and knee extension repetitions), and super-set protocol (3 sets of a combination of 10 repetitions of knee flexion immediately followed by 10 repetitions of knee extension repetitions). Tests were performed at 60° · s(-1) and 180° · s(-1), randomized across 3 days and separated by at least 72 h. There were no significant differences between protocols for peak torque at 60° · s(-1) or 180° · s(-1). Total work was significantly higher during the reciprocal action protocol compared with the super-set protocol at 60° · s(-1). There was a significant decline in peak torque (from 240.6 to 212.9 N · m) and total work (from 2294 to 1899 J) for the control condition at 60° · s(-1). Also, total work declined significantly across sets for the super-set protocol at 60° · s(-1) (from 2157 to 1707 J). Results indicate that a reciprocal action protocol provides torque maintenance during multiple sets of isokinetic training, both at slow and high velocities.  相似文献