Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Development and assessment of new exchange-correlation functionals (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6264-6271 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We recently presented a new method for developing generalized gradient approximation (GGA) exchange-correlation energy functionals, using a least-squares procedure involving numerical exchange-correlation potentials and experimental energetics and nuclear gradients. In this paper we use the same method to develop a new GGA functional, denoted HCTH, based on an expansion recently suggested by Becke [J. Chem. Phys. 107, 8554 (1997)]. For our extensive training set, the new functional yields improved energetics compared to both the BLYP and B3LYP functionals [Phys. Rev. A 38, 3098 (1988); Phys. Rev. B 37, 785 (1988); J. Chem. Phys. 98, 5648 (1993); J. Phys. Chem. 98, 11623 (1994)]. The geometries of these systems, together with those of a set of transition metal compounds, are shown to be an improvement over the BLYP functional, while the reaction barriers for six hydrogen abstraction reactions are comparable to those of B3LYP. These improvements are achieved without introducing any fraction of exact orbital exchange into the new functional. We have also re-optimized the functional of Becke—which does involve exact exchange—for use in self-consistent calculations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477267
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The specificity of strength training: the effect of posture (1996)
    Springer
    European journal of applied physiology 73 (1996), S. 346-352 
    Details
    ISSN: 1439-6327
    Keywords: Resistance training ; Performance enhancement ; Exercise selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is a paucity of research into the importance of performing strength training exercises in postures specific to the movements they are attempting to facilitate. In addressing this question, 27 previously trained subjects were randomly allocated into heavy weight training and control groups. The weight training group performed 4–6 sets of 6–10 repetitions of the squat and bench press lifts twice a week for 8 weeks. Prior to and after the training period the following tests were conducted: bench press throw at 30% of maximal load, vertical jump, maximal squat and bench press lifts, push-up test performed over a force platform, 40-m sprint, 6-s cycle, and isokinetic tests assessing upper and lower body musculature in varying actions. The results supported the concept that posture is important in training as those exercises conducted in similar postures to the training recorded the greatest improvement in performance. For example, after completion of the training the weight training subjects significantly increased by approximately 12% the maximal load lifted in the bench press exercise and the peak torque in the isokinetic bench press test. However, performance in the isokinetic horizontal arm adduction test was not significantly changed. We speculate that the phenomenon of posture specificity may, at least in part, be caused by the differing postures altering the neural input to the musculature. The results stress the importance of selecting exercises in which the posture closely resembles that of the movements they are attempting to facilitate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02425497
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Poor correlations between isometric tests and dynamic performance: relationship to muscle activation (1996)
    Springer
    European journal of applied physiology 73 (1996), S. 353-357 
    Details
    ISSN: 1439-6327
    Keywords: Upper body ; Muscle function ; Median frequency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this research was to perform isometric tests at two joint angles and examine their relationship to dynamic performance. In addition, electromyograph data were collected from the triceps brachii and pectoralis major muscles to compare underlying neural characteristics between the isometric tests and dynamic movement. A group of 24 healthy male subjects performed two isometric tests in a bench press position, at elbow angles of 90 and 120°. From these data, the maximal force and rate of force development were determined. In addition, each subject performed a seated medicine ball throw as a measure of dynamic upper body performance. Correlations showed that isometric measurements of force (r = 0.47–0.55) and rate of force development (r = 0.08–0.31) were poor predictors of dynamic performance. The angle of isometric assessment had little effect on the relationship between the tests and measurements of performance. The myo-electric data was processed in terms of the integrated electromyogram and the Fourier transformed frequency spectrum. These data demonstrated differences in the neural activation patterns of the musculature, between the isometric 90° test and the medicine ball throw. The poor relationship between isometric tests and medicine ball performance was consequently, at least partially, attributed to differing motor unit activation patterns between isometric and dynamic movement. The results of this research strongly suggest that isometric tests have limited value when assessing dynamic upper body performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02425498
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Influence of load and stretch shortening cycle on the kinematics, kinetics and muscle activation that occurs during explosive upper-body movements (1997)
    Springer
    European journal of applied physiology 75 (1997), S. 333-342 
    Details
    ISSN: 1439-6327
    Keywords: Key words  Force velocity relationship  ;  Muscle power  ;  Electromyography  ;  Bench press
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Although explosive power in lower-body movements has been extensively studied, there is a paucity of research examining such movements in the upper body. This study aimed to investigate the influence of load and the stretch shortening cycle (SSC) on the kinematics, kinetics, and muscle activation that occurs during maximal effort throws. A total of 17 male subjects performed SSC and concentric only (CO) bench throws using loads of 15%, 30%, 45%, 60%, 75%, 90% and 100% of their previously determined one repetition maximum bench press. The displacement, velocity, acceleration, force and power output as well as the electromyogram (EMG) from pectoralis major, anterior deltoid, and triceps brachii were recorded for each throw. The results were compared using multivariate analysis of variance with repeated measures. A criterion alpha level of P ≤ 0.05 was used. Similar force velocity power relationships were determined for this multijoint upper-body movement as has been found for isolated muscles, single joint movements, and vertical jumping. The highest power output was produced at the 30% [563 (104) W] and 45% [560 (86) W] loads during the SSC throws. Force output increased as a function of load; however, even the lighter loads resulted in considerable force due to the high accelerations produced. Average velocity, average and peak force, and average and peak power output were significantly higher for the SSC throws compared to the CO throws. However, peak velocity and height thrown were not potentiated by performing the pre-stretch because the duration and range of movement allowed the ability of the muscle to generate force at high shortening velocities to dominate the resulting throw. As such, explosive movements involving longer concentric actions than experienced during brief SSC movements may be limited by the ability of the muscle to produce force during fast contraction velocities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050169
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...