Slow Version Research Articles

“Flash” dance: How speed modulates perceived duration in dancers and non-dancers

Speed has been proposed as a modulating factor on duration estimation. However, the different measurement methodologies and experimental designs used have led to inconsistent results across studies, and, thus, the issue of how speed modulates time estimation remains unresolved. Additionally, no studies have looked into the role of expertise on spatiotemporal tasks (tasks requiring high temporal and spatial acuity; e.g., dancing) and susceptibility to modulations of speed in timing judgments. In the present study, therefore, using naturalistic, dynamic dance stimuli, we aimed at defining the role of speed and the interaction of speed and experience on time estimation. We presented videos of a dancer performing identical ballet steps in fast and slow versions, while controlling for the number of changes present. Professional dancers and non-dancers performed duration judgments through a production and a reproduction task. Analysis revealed a significantly larger underestimation of fast videos as compared to slow ones during reproduction. The exact opposite result was true for the production task. Dancers were significantly less variable in their time estimations as compared to non-dancers. Speed and experience, therefore, affect the participants' estimates of time. Results are discussed in association to the theoretical framework of current models by focusing on the role of attention.

Fast Channel Switching Based on SVC in IPTV Environments

In Internet Protocol TeleVision (IPTV) systems, the use of video compression results in a trade-off between random access and bandwidth consumption. Most of the time, priority is given to compression efficiency, resulting in low channel switching performance. In this paper, a Scalable Video Coding (SVC) configuration is proposed, wherein base and enhancement layer are coded in such a way that fast channel switching can be offered without impacting the access network bandwidth consumption. This is achieved by encoding a full quality slow channel switching version of the video stream in the base layer extended with a reduced quality fast switching enhancement layer. Additionally, this configuration offers backward compatibility with H.264/AVC, enabling a gradual upgrade of the IPTV system from H.264/AVC to SVC. When comparing this technique to single layer H.264/AVC, 25.0% bandwidth reduction on the access network is obtained without impacting channel switching speed, but only at the cost of a slightly reduced quality ( -1 dB PSNR) during a short transition period (maximum 48 frames). If a comparison is made with a regular SVC configuration, 39.4% bandwidth reduction on the access network during steady state is obtained. Compared to simulcast H.264/AVC, 32.0% bandwidth reduction on the core network is observed.

Look-Up Table Implementation of a Slow Envelope Dependent Digital Predistorter for Envelope Tracking Power Amplifiers

This letter presents a dynamic slow envelope dependent digital predistorter (SED-DPD) capable of compensating for the nonlinear distortion and memory effects that arise in envelope tracking (ET) power amplifiers (PAs) when using a slow version of the signal's envelope to dynamically supply the PA drain voltage. Moreover, a new DPD architecture based on the combination of several basic predistortion cells (BPCs) is presented to allow the FPGA implementation of the proposed SED-DPD. Finally, results showing the necessity and linearization performance of the proposed dynamic SED-DPD are provided.

Are the anticipatory pathways in lecithotrophic larvae that delay metamorphosis adaptations? (A review)

During anticipatory development in lecithotrophic larvae that delay metamorphosis, the growth and differentiation of features of the adult action system continue to develop at a slow pace even though they do not become functional. After metamorphosis occurs, the larger size and advanced development of these components may allow juveniles to initially grow at a faster rate than they normally would. Anticipatory development has been demonstrated in archeogastropods, some solitary ascidians and a hydrozoan. In the gastropod Haliotis and the hydrozoan Phialidium anticipatory development increases the initial growth rate of juveniles. In Haliotis and ascidians all of the larvae of a given female that live long enough exhibit anticipatory development. In Phialidium, the ability of a given female to produce larvae that can exhibit anticipatory development is a maternal polymorphic character. In Haliotis and solitary ascidians that exhibit anticipatory development, it appears to be a slower version of the rapid developmental changes that occur in parts of the adult action system at metamorphosis. In Phialidium, developmental changes in relative sizes of the different presumptive regions of the polyp are slowly altered prior to and independently of metamorphosis. Anticipatory development is not linked to the decrease in the size or nutrient reserves of older larvae but to the length of their larval period. From an evolutionary perspective, the mechanisms that operate during anticipatory development are probably of adaptive significance for lecithotrophic larvae of species that spend variable amounts of time in the water column because of a patchy distribution of appropriate settlement cues. The developmental mechanisms that underlie anticipatory development may have been used during the transition from lecithotrophy to planktotrophy.

Myosin V as a Point-to-Point Organelle Transporter

Mice that lack myosin Va (dilute mice) exhibit two striking phenotypes- a dilution of coat color and severe ataxia. Regarding the first phenotype, we previously demonstrated that the myosin cooperates with long-range, bidirectional, microtubule-based transport to position melanosomes at the melanocyte's dentritic tips, the site of melanosome transfer from the melanocyte to the keratinocyte (the Cooperative-Capture Model) (J. Cell Biol. 1998, 143:1899). These and other results have contributed to the current debate as to whether type V myosins in higher eukaryotes function as vesicle transporters or as dynamic vesicle tethers. Regarding the second phenotype, we have now demonstrated that myosin Va serves as a point-to-point transporter to carry the ER into the dendritic spines of cerebellar Purkinje neurons following its long-range transport out dendrites via microtubule motors (Nature Cell Biol. 2011, 13:40). That the myosin actually moves the ER in vivo is supported by several results, the most convincing of which is that in dilute Purkinje neurons rescued with slow versions of myosin Va (lever arm truncations, a switch 1 mutant), the speed of ER tubule transport into spines is slowed correspondingly. Moreover, we show that this myosin Va-dependent ER targeting is required for the local calcium transient downstream of strong spine activation that underlies synaptic plasticity/learning and, hence, normal coordination. These results, together with another recent study from our lab demonstrating that the Dictyostelium type V myosin MyoJ drives the cortical translocation of contractile vacuole membrane tubules (J. Cell Biol. 2009, 186:555), argue that, as in yeast, type V myosins in higher eukaryotes can serve as point-to-point organelle transporters.

Equivalence of Human Odometry by Walk and Run Is Indifferent to Self-Selected Speed

ABSTRACT Humans and other animals can measure distances nonvisually by legged locomotion. Experiments typically employ an outbound measure (M) and an inbound report (R) phase. Previous research has found distance reproduction to be maximally accurate, when gait symmetry and speed of M and R are of like kind: Successful human odometry manifests at the level of the M-R system. In the present work, M was an experimenter-set distance produced by a blindfolded participant using a primary gait (walk, run). R was always by walk. Fast and slow versions of walk and run were adopted by participants, such that when M was fast R was slow, and vice versa. Distance was underestimated when M was slower than R and overestimated when M was faster than R. However, the pattern of participant-adopted velocities indicated that it was the instructions, not the speed as such, that yielded the pattern of results. The results are interpretable through a dynamical perspective and indicate speed is an imperfection parameter acting on the attractors of the M-R system.

A comparative study of slow and fast suryanamaskar on physiological function

Background:Numerous scientific studies have reported beneficial physiological changes after short- and long-term yoga training. Suryanamaskar (SN) is an integral part of modern yoga training and may be performed either in a slow or rapid manner. As there are few studies on SN, we conducted this study to determine the differential effect of 6 months training in the fast and slow versions.Materials and Methods:42 school children in the age group of 12–16 years were randomly divided into two groups of 21 each. Group I and Group II received 6 months training in performance of slow suryanamaskar (SSN) and fast suryanamaskar (FSN), respectively.Results:Training in SSN produced a significant decrease in diastolic pressure. In contrast, training in FSN produced a significant increase in systolic pressure. Although there was a highly significant increase in isometric hand grip (IHG) strength and hand grip endurance (HGE) in both the groups, the increase in HGE in FSN group was significantly more than in SSN group. Pulmonary function tests showed improvements in both the groups though intergroup comparison showed no significance difference. Maximum inspiratory pressure (MIP) and maximum expiratory pressure increased significantly in both the groups with increase of MIP in FSN group being more significant than in SSN.Conclusion:The present study reports that SN has positive physiological benefits as evidenced by improvement of pulmonary function, respiratory pressures, hand grip strength and endurance, and resting cardiovascular parameters. It also demonstrates the differences between SN training when performed in a slow and fast manner, concluding that the effects of FSN are similar to physical aerobic exercises, whereas the effects of SSN are similar to those of yoga training.

High-speed crystal detection and characterization using a fast-readout detector

A novel raster-scanning method combining continuous sample translation with the fast readout of a Pilatus P6M detector has been developed on microfocus beamline I24 at Diamond Light Source. This fast grid-scan tool allows the rapid evaluation of large sample volumes without the need to increase the beam size at the sample through changes in beamline hardware. A slow version is available for slow-readout detectors. Examples of grid-scan use in centring optically invisible samples and in detecting and characterizing numerous microcrystals on a mesh-like holder illustrate the most common applications of the grid scan now in routine use on I24.

Electrophilic Activation of Alkenes by Platinum(II): So Much More Than a Slow Version of Palladium(II)

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Electrophilic Activation of Alkenes by Platinum(II): So Much More Than a Slow Version of Palladium(II)

The electrophilic activation of alkenes by transition-metal catalysts is a fundamental step in a rapidly growing number of catalytic processes. Although palladium is the best known metal for this purpose, the special properties of its third-row cousin platinum (strong metal-ligand bonds and slow substitution kinetics) have enabled the development of transformations that are initiated by addition to the C=C bonds by protic carbon, nitrogen, oxygen, and phosphorus nucleophiles, as well as alkene or arene nucleophiles. Additionally, reactivity profiles, which are often unique to platinum, provide wholly new reaction products. This Review concerns platinum-catalyzed electrophilic alkene activation reactions, with a special emphasis on the mechanistic properties of known systems, on the differences between platinum and palladium catalysts, and on the prospects for the development of new systems.

Simultaneous B-M-mode scanning method for real-time full-range Fourier domain optical coherence tomography

High-speed complex full-range Fourier domain optical coherence tomography (FD-OCT) is demonstrated. In this FD-OCT, the phase modulation of a reference beam (M scan) and transversal scanning (B scan) are simultaneously performed. The Fourier transform method is applied along the direction of the B scan to reconstruct complex spectra, and the complex spectra comprise a full-range OCT image. Because of this simultaneous B-M-mode scan, the FD-OCT requires only a single A scan for each single transversal position to obtain a full-range FD-OCT image. A simple but slow version of the FD-OCT visualizes the cross section of a plastic plate. A modified fast version of this FD-OCT investigates a sweat duct in a finger pad in vivo and visualizes it with an acquisition time of 27 ms.

Separating fast and slow modes in coupled chaotic systems

Abstract. We test a simple technique based on breeding to separate fast and slow unstable modes in coupled systems with different time scales of evolution and variable amplitudes. The technique takes advantage of the earlier saturation of error growth rate of the fastest mode and of the lower value of the saturation amplitude of perturbation of either the fast or the slow modes. These properties of the coupled system allow a physically-based selection of the rescaling time interval and the amplitude of initial perturbations in the "breeding" of unstable modes (Toth and Kalnay, 1993, 1996, 1997; Aurell et al., 1997; Boffetta et al., 1998) to isolate the desired mode. We perform tests in coupled models composed of fast and slow versions of the Lorenz (1963) model with different strengths of coupling. As examples we present first a coupled system which we denote "weather with convection", with a slow, large amplitude model coupled with a fast, small amplitude model, second an "ENSO" system with a "tropical atmosphere" strongly coupled with a "tropical ocean", and finally a triply coupled system denoted "tropical-extratropical" in which a fast model (representing the "extratropical atmosphere") is loosely coupled to the "ENSO" system. We find that it is always possible to isolate the fast modes by taking the limit of small amplitudes and short rescaling intervals, in which case, as expected, the results are the same as the local Lyapunov growth obtained with the linear tangent model. In contrast, slow modes cannot be isolated with either Lyapunov or Singular vectors, since the linear tangent and adjoint models are dominated by the fast modes. Breeding is successful in isolating slow modes if rescaling intervals and amplitudes are chosen from physically appropriate scales.

Audiovisual integration in the absence of a McGurk effect

The McGurk effect, a change in perceived place of articulation due to an incongruent visual stimulus (e.g., auditory /pi/ with visual /ti/ perceived as /ti/), demonstrates the contribution of vision to speech perception. Interestingly, in a given experiment the McGurk effect typically does not occur on every trial. We investigated whether non-McGurk trials result from a failure to perceptually integrate auditory and visual information by simultaneously manipulating visual place of articulation and visual speaking rate. Previous work [Green and Miller, Percept. Psychophys. 38, 269–276 (1985)] has shown that the boundary along an auditory /bi/–/pi/ voice-onset-time (VOT) continuum occurs at a longer VOT when the auditory stimulus is paired with a slow rather than a fast visual /pi/. We paired stimuli from an auditory /bi/–/pi/ continuum with fast and slow versions of a visual /ti/, and subjects identified each item as /b/, /p/, /d/, or /t/. We found a rate effect on McGurk trials, with the /d/–/t/ boundary occurring at a longer VOT when the visual stimulus was slow rather than fast. Importantly, we found a comparable rate effect for the /b/–/p/ boundary on non-McGurk trials. This indicates that audiovisual integration occurs even in the absence of a McGurk effect. [Work supported by NIH/NIDCD.]

Predicting the output from a complex computer code when fast approximations are available

S We consider prediction and uncertainty analysis for complex computer codes which can be run at different levels of sophistication. In particular, we wish to improve efficiency by combining expensive runs of the most complex versions of the code with relatively cheap runs from one or more simpler approximations. A Bayesian approach is described in which prior beliefs about the codes are represented in terms of Gaussian processes. An example is presented using two versions of an oil reservoir simulator. 1. C  Complex mathematical models, implemented in large computer codes, have been used to study real systems in many areas of scientific research (Sacks et al., 1989), usually because physical experimentation is too costly and sometimes impossible, as in the case of large environmental systems. A ‘computer experiment’ involves running the code with various input values for the purpose of learning something about the real system. Often a simulator can be run at different levels of complexity, with versions ranging from the most sophisticated high level code to the most basic. For example, in § 4 we consider two codes which simulate oil pressure at a well of a hydrocarbon reservoir. Both codes use finite element analysis, in which the rocks comprising the reservoir are represented by small interacting grid blocks. The flow of oil within the reservoir can be simulated by considering the interaction between the blocks. The two codes differ in the resolution of the grid, so that we have a very accurate, slow version using many small blocks and a crude approximation using large blocks which runs much faster. Alternatively, a mathematical model could be expanded to include more of the scientific laws underlying the physical processes. Simple, fast versions of the code may well include the most important features, and are useful for preliminary investigations. In real-time applications the number of runs from a high level simulator may be limited by expense. Then there is a need to trade-off the complexity of the expensive code with the availability of the simpler approximations. The purpose of the current paper is to explore ways in which runs from several levels of a code can be used to make inference about the output from the most complex code. We may also have uncertainty about values for the input parameters which apply in any given application. Uncertainty analysis of computer codes describes how this uncertainty on the inputs affects our uncertainty about the output.

Evidence for separate control of slow version and vergence eye movements: support for Hering's Law.

When a visual stimulus changes direction and distance simultaneously, Hering's Law argues that the resulting eye movements are the result of combined version and vergence control processes. Recently, it has been suggested that slow asymmetrical eye movements might be guided by monocular control processes wherein each eye is driven by its own retinal image. Experimental results presented here show behavioral differences between slow version and slow vergence eye movements, indicating that different control processes drive the two "pure" responses. Specifically, version tracking of constant velocity stimuli (i.e., smooth pursuit) is more precise, showing less variation in tracking velocity than movements of equal velocity produced by vergence stimuli. When the two stimuli are combined, the variability in tracking is consistent with the addition of the two components in proportion to their respective stimuli. These results provide support for Hering's Law, at least for low velocity, smooth tracking movements (i.e., slow version and slow vergence.

The influence of sentence articulation rate on the internal structure of phonetic categories

Numerous experiments have shown that listeners perceive phonetic distinctions in a rate-dependent manner. A case in point is the /b/–/p/ voicing distinction, specified by voice onset time (VOT). One standard rate effect is a shift in the/b/–/p/ boundary toward longer VOT values as speech becomes slower. Both a slowing of the target syllable itself and a slowing of the sentence containing the target syllable produce the effect. A recent investigation [J. L. Miller and L. E. Volaitis, Percept. Psychophys. 46, 505–512 (1989)] demonstrated that when speaking rate is specified by the target syllable, it alters not only the location of the category boundary, but also which stimuli within a category are judged to be the best exemplars of that category. In the present investigation, it was asked whether the rate at which a sentence is articulated can have the same comprehensive effect. A series of 215-ms syllables were created that ranged from /bi/ through /pi/ to a breathy, exaggerated version of /pi/; VOT varied from 10 to 205 ms. Each syllable was inserted into a fast and slow version of the sentence frame ‘‘She said she heard −− here.’’ A preliminary two-choice study (with VOT values between 0 and 60 ms), confirmed the standard effect of sentence rate at the /b/–/p/ category boundary. In the main experiment, listeners heard sentences of the same rate in random order. They rated each target syllable for its goodness as /pi/ on a scale of 1 to 10; the higher the number, the better the exemplar. It was expected that for each sentence rate, only a limited range of target stimuli would be given high ratings. At issue was the location of this range of best exemplars. If sentence rate, like target syllable rate, alters the internal structure of the category, then as the sentence becomes slower, the best-exemplar range should shift toward longer VOT values. This is precisely what happened. This finding underscores the comprehensive nature of the listener’s adjustment for speaking rate during phonetic perception. [Work supported by NIH.]

Articulatory-rate context effects in phoneme identification.

Three experiments demonstrated that the pattern of changes in articulatory rate in a precursor phrase can affect the perception of voicing in a syllable-initial prestress velar stop consonant. Fast and slow versions of a 10-word precursor phrase were recorded, and sections from each version were combined to produce several precursors with different patterns of change in articulatory rate. Listeners judged the identity of a target syllable, selected from a 7-member /gi/-ki/ voice-onset-time (VOT) continuum, that followed each precursor phrase after a variable brief pause. The major results were: (a) articulatory-rate effects were not restricted to the target syllable's immediate context; (b) rate effects depended on the pattern of rate changes in the precursor and not the amount of fast or slow speech or the proximity of fast or slow speech to the target syllable: and (c) shortening of the pause (or closure) duration led to a shortening of VOT boundaries rather than a lengthening as previously found in this phonetic context. Results are explained in terms of the role of dynamic temporal expectancies in determining the response to temporal information in speech, and implications for theories of extrinsic vs. intrinsic timing are discussed.

Cytoplasmic streaming in giant algal cells: A historical survey of experimental approaches

Various methods have been used to study cytoplasmic streaming in giant algal cells during the past three decades. Simple techniques can be used with characean internodal cells to modify the cell constitution in various ways to gain insight into the mechanism of cytoplasmic streaming. Another method involves isolatingin vitro a huge drop of uninjured endoplasm, to examine its physical and dynamic properties. The motive force responsible for streaming has been measured by three different techniques with similar results. Subcortical fibrils consisting of bundles of F-actin with the same polarity are indispensable for streaming. Differential treatment of the endoplasm and ectoplasm has shown that putative characean myosin is localized in the endoplasm. Studies of the roles of ATP, Mg2+, Ca2+, H+ etc. in the streaming have been conducted by cellular perfusion, which allows removal of the tonoplast, or by techniques permeabilizing the protoplasmic membrane. A slow version of the movement can even be artificially reproduced by combining characean actinin situ and exogenous myosin in the presence of Mg-ATP. The findings thus far obtained support the hypothesis that cytoplasmic streaming in characean cells is caused by an active shearing force produced by interaction of the actin filament bundles on the cortex with myosin in the endoplasm.

Oscillator mechanisms in the human motor system: investigating their properties using the aftercontraction effect.

It is proposed that the human motor system is organized to use hardware and/or software non-linear oscillator mechanisms, the output of these oscillators being responsible for driving the limbs via signals to muscle groups. Following earlier theoretical development, it is argued that these muscle groupings act as a unit and themselves are likely to behave as a non-linear system. The attributes of non-linear oscillators are many, and they are potentially significant for the explanation of motor behavior. This paper reviews and presents recent experiments that investigated the properties of muscular aftercontraction. The basic finding shows that subsequent to a period of moderate strain against a fixed surface the treated limb exhibits prolonged involuntary molar oscillations in the plane of the treatment. These results provide for the presence of driving oscillator mechanisms in the human motor apparatus. The mechanisms show generality of action in that directed attention can lead to oscillation of untreated limbs. Overall, the experiments showed that the movements exhibited the mutual interaction, synchronization, and preservation of phase relationships that are fundamental properties of non-linear oscillators. the picture that emerges is that these mechanisms can drive involuntary movements that are richly patterned: like slow versions of voluntary movements. The aftercontraction phenomenon proves to be an excellent tool for research on the oscillatory substrate of human motor organization.