Home About us Contact
|
Home About us Contact | ||
|
|
||
Slow Speeds (slow + speed)
Selected AbstractsThe characteristics of young and adult dyslexics readers on reading and reading related cognitive tasks as compared to normal readersDYSLEXIA, Issue 2 2005Shelley Miller-Shaul Abstract Most of the research into dyslexia has been carried out among children and has raised the question whether the characteristics of young dyslexics are similar to those of adult dyslexics. The aim of this research was, therefore, to confirm whether the cognitive deficits, which appear among young dyslexics on reading and reading related tasks, are similar among adult dyslexics. Four groups of subjects were tested in this study: two groups of fourth graders, dyslexic and normal readers, and two groups of students, compensated dyslexics and normal readers. A comparison of the differences in research measures between the young dyslexics and their control group, and between the adult dyslexics and their control group, clearly indicates that the difference between regular readers and dyslexics is significantly smaller in the adult group on orthographic tasks, and this difference increases in adults on phonological tasks. The findings of this study reinforce the assumption that dyslexics have particular difficulty with the phonological-auditory channel. Another main finding is the slow speed of processing in verbal and non-verbal tasks. It can be assumed that these problems start at a young age and persist in compensated adult dyslexics. Copyright © 2005 John Wiley & Sons, Ltd. [source] Procrastination as self-regulation failure of performance: effects of cognitive load, self-awareness, and time limits on ,working best under pressure'EUROPEAN JOURNAL OF PERSONALITY, Issue 5 2001Joseph R. Ferrari Effects of cognitive load, objective self-awareness and time limits on the self-regulation of performance speed and accuracy were investigated between procrastinators and non-procrastinators. In experiment 1 chronic procrastinators completed fewer items (slow speed) and made more errors (less accuracy) than non-procrastinators under high but not low cognitive load conditions when the time span was limited and brief. In experiment 2 chronic procrastinators performed slower than non-procrastinators under a 2 second, but not under no limit, 1 second, or 4 second time limit conditions. Chronic procrastinators compared to non-procrastinators also performed more slowly and made more performance errors under objective self-awareness conditions regardless of the length of time. These experiments indicate that chronic procrastinators regulate ineffectively their performance speed and accuracy when they ,work under pressure' (defined by high cognitive load, objective self-awareness, and imposed time limitations). Copyright © 2001 John Wiley & Sons, Ltd. [source] Spherical sliding isolation bearings with adaptive behavior: Experimental verificationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2008Daniel M. Fenz Abstract This paper describes an experimental program to examine the force,displacement behavior of a class of multi-spherical sliding bearings. The primary goal of the experiments is to test the validity of the theory developed in a companion paper that describes the behavior of these devices. Experimental work consisted of testing the three primary variations of these bearings in several configurations of different friction and displacement capacities. Most tests were carried out at slow speeds; however, some testing was also conducted at high speed (up to approximately 400,mm/s) to examine the behavior under dynamic conditions. The results of experimental testing were generally found to be in very good agreement with the analytical results. It is shown that the forces and displacements at which transitions in stiffness occur are predictable and therefore controllable in design. Furthermore, the underlying principles of operation were confirmed by the fact that starting and stopping of sliding on the different surfaces occurred as expected from theory. Copyright © 2007 John Wiley & Sons, Ltd. [source] Mapping responses to frequency sweeps and tones in the inferior colliculus of house miceEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2003Steffen R. Hage Abstract In auditory maps of the primary auditory cortex, neural response properties are arranged in a systematic way over the cortical surface. As in the visual system, such maps may play a critical role in the representation of sounds for perception and cognition. By recording from single neurons in the central nucleus of the inferior colliculus (ICC) of the mouse, we present the first evidence for spatial organizations of parameters of frequency sweeps (sweep speed, upward/downward sweep direction) and of whole-field tone response patterns together with a map of frequency tuning curve shape. The maps of sweep speed, tone response patterns and tuning curve shape are concentrically arranged on frequency band laminae of the ICC with the representation of slow speeds, build up response types and sharp tuning mainly in the centre of a lamina, and all (including high) speeds, phasic response types and broad tuning mainly in the periphery. Representation of sweep direction shows preferences for upward sweeps medially and laterally and downward sweeps mainly centrally in the ICC (either striped or concentric map). These maps are compatible with the idea of a gradient of decreasing inhibition from the centre to the periphery of the ICC and by gradients of intrinsic neuronal properties (onset or sustained responding). The maps in the inferior colliculus compare favourably with corresponding maps in the primary auditory cortex, and we show how the maps of sweep speed and direction selectivity of the primary auditory cortex could be derived from the here-found maps of the inferior colliculus. [source] Ontogenetic change in novel functions: waterfall climbing in adult Hawaiian gobiid fishesJOURNAL OF ZOOLOGY, Issue 2 2007R. W. Blob Abstract Juveniles from three species of Hawaiian gobiid fishes climb waterfalls as part of an amphidromous life cycle, allowing them to re-penetrate adult upstream habitats after being swept out to the ocean upon hatching. The importance of climbing for juvenile stream gobies is well established, but adult fish in upstream island habitats also face potential downstream displacement by periodic disturbances. Thus, retention of climbing ability could be advantageous for adult stream gobies. Climbing performance might be expected to decline among adults, however, due to the tendency for mass-specific muscular power production to decrease with body size, and a lack of positively allometric growth among structures like the pelvic sucker that support body weight against gravity. To evaluate changes in waterfall-climbing ability with body size in Hawaiian stream gobies, we compared climbing performance and kinematics between adults and juveniles from three species: Awaous guamensis, Sicyopterus stimpsoni and Lentipes concolor. For species in which juveniles climbed using ,powerbursts' of axial undulation, adult performance and kinematics showed marked changes: adult A. guamensis failed to climb, and adult L. concolor used multiple pectoral fin adductions to crutch up surfaces at slow speeds, rather than rapid powerbursts. Adult S. stimpsoni, like juveniles, still used oral and pelvic suckers to ,inch' up surfaces and climbed at speeds comparable to those of juveniles. However, unlike juveniles, adult S. stimpsoni also add pectoral fin crutching to every climbing cycle. Thus, although powerburst species appear to be particularly susceptible to size-related declines in waterfall-climbing performance, the addition of compensatory mechanisms prevents the loss of this novel function in some species. [source] Detection of subsurface permafrost features with ground-penetrating radar, Barrow, AlaskaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2001K. M. Hinkel Abstract A ground-penetrating radar (GPR) survey was conducted in May 1999 on the 1 km2 Circumpolar Active Layer Monitoring (CALM) grid 5 km east of Barrow, Alaska. Spatially continuous measurements were collected along established transects while the active layer remained frozen. The primary objectives were to determine the ,long-term' position of the permafrost table, to recognize ice wedges and ice lenses, and to locate the organic,mineral soil interface. GPR signal and core collection were performed in tandem to verify signal interpretation, to calibrate the instrument, and to determine optimal GPR data-collection parameters. Two-way travel times from the antenna to subsurface reflectors were compared with measured depths obtained from soil cores to estimate an average pulse propagation velocity of 0.13 m/ns through the frozen soil. The most conspicuous subsurface reflectors were ice wedges, which gave high-amplitude hyperbolic reflections. Owing to its higher ice content, the approximate long-term position of the permafrost table could be traced laterally across the profile. Radar interpretations were obscured by the effects of cryoturbation, and because some horizons lack sufficient contrast in electrical properties. Highly detailed information can be obtained by collecting radar data at relatively slow speeds of advance, by using faster scanning rates (>32 scans/s), and by employing high-frequency antennas (>400 MHz). Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ Un levé réalisé avec un radar dont les ondes pénètrent dans le sol a été réalisé en mai 1999 sur un km2 appartenant à la grille établie pour suivre l'évolution de la couche active circumpolaire (CALM), 5 km a l'est de Barrow, Alaska. Des mesures ont été réalisées le long de transects alors que la couche active était gelée. Les premiers objectifs étaient de déterminer la position à long terme de la table du pergélisol, de reconnaître les coins et les lentilles de glace, et de localiser le contact entre les sols organiques et minéraux. Les données radar et des carottes de sondages ont été recueillies au même moment pour vérifier l'interprétation des données radar, calibrer l'instrument et déterminer les meilleurs paramètres d'enregistrement. Deux facons de calculer les temps de parcours depuis l'antenne jusqu'aux réflecteurs souterrains ont été comparés avec des mesures obtenues par sondages, pour estimer une vitesse moyenne de propagation de 0.13 m/ns à travers le sol gelé. Les réflecteurs les plus apparents ont été les coins de glace qui donnent des réflexions hyperboliques de grande amplitude. En raison de leur haute teneur en glace, la position approximative à long terme de la table du pergélisol a pu être reconnue le long des profils. Les interprétations sont obscurcies par les effects des cryoturbations et aussi, parce que certains horizons n'ont pas un contraste suffisant dans leurs propriétés électriques. Une information hautement détaillée peut être obtenue par la méthode radar en utilisant des vitesses lentes d'avancée, de rapides vitesses de scannages (>32 scans/s) et en utilisant des antennes de hautes fréquence (>400 MHz). Copyright © 2001 John Wiley & Sons, Ltd. [source] The interplay between speed, kinetics, and hand postures during primate terrestrial locomotionAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Biren A. Patel Abstract Nonprimate terrestrial mammals may use digitigrade postures to help moderate distal limb joint moments and metapodial stresses that may arise during high-speed locomotion with high-ground reaction forces (GRF). This study evaluates the relationships between speed, GRFs, and distal forelimb kinematics in order to evaluate if primates also adopt digitigrade hand postures during terrestrial locomotion for these same reasons. Three cercopithecine monkey species (Papio anubis, Macaca mulatta, Erythrocebus patas) were videotaped moving unrestrained along a horizontal runway instrumented with a force platform. Three-dimensional forelimb kinematics and GRFs were measured when the vertical force component reached its peak. Hand posture was measured as the angle between the metacarpal segment and the ground (MGA). As predicted, digitigrade hand postures (larger MGA) are associated with shorter GRF moment arms and lower wrist joint moments. Contrary to expectations, individuals used more palmigrade-like (i.e. less digitigrade) hand postures (smaller MGA) when the forelimb was subjected to higher forces (at faster speeds) resulting in potentially larger wrist joint moments. Accordingly, these primates may not use their ability to alter their hand postures to reduce rising joint moments at faster speeds. Digitigrady at slow speeds may improve the mechanical advantage of antigravity muscles crossing the wrist joint. At faster speeds, greater palmigrady is likely caused by joint collapse, but this posture may be suited to distribute higher GRFs over a larger surface area to lower stresses throughout the hand. Thus, a digitigrade hand posture is not a cursorial (i.e. high speed) adaptation in primates and differs from that of other mammals. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Visual guidance of the human foot during a stepTHE JOURNAL OF PHYSIOLOGY, Issue 2 2005Raymond F. Reynolds When the intended foot placement changes during a step, either due to an obstacle appearing in our path or the sudden shift of a target, visual input can rapidly alter foot trajectory. However, previous studies suggest that when intended foot placement does not change, the path of the foot is fixed after it leaves the floor and vision has no further influence. Here we ask whether visual feedback can be used to improve the accuracy of foot placement during a normal, unperturbed step. To investigate this we measured foot trajectory when subjects made accurate steps, at fast and slow speeds, to stationary floor-mounted targets. Vision was randomly occluded in 50% of trials at the point of foot-off. This caused an increase in foot placement error, reflecting lower accuracy and higher variability. This effect was greatest for slow steps. Trajectory heading analysis revealed that visually guided corrections occurred as the foot neared the target (on average 64 mm away). They occurred closer to the target for the faster movements thus allowing less time and space to execute corrections. However, allowing for a fixed reaction time of 120 ms, movement errors were detected when the foot was approximately halfway to the target. These results suggest that visual information can be used to adjust foot trajectory during the swing phase of a step when stepping onto a stationary target, even for fast movements. Such fine control would be advantageous when environmental constraints place limitations on foot placement, for example when hiking over rough terrain. [source] | |||||||||||||