The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Nikita Chernetsov - One of the best experts on this subject based on the ideXlab platform.
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Further evidence of a time-independent stellar compass in a night-migrating songbird
Behavioral Ecology and Sociobiology, 2017Co-Authors: Alexander Pakhomov, Anna Anashina, Nikita ChernetsovAbstract:We tested whether European robins Erithacus rubecula have a time-independent stellar compass, i.e. whether they can use the stellar pattern for finding the seasonally appropriate migratory direction without reference to their Internal Clock. It has been claimed earlier on the basis of experiments with other nocturnal migrants, indigo buntings Passerina cyanea , pied flycatchers Ficedula hypoleuca and blackcaps Sylvia atricapilla , but none of the previous experiments was performed in the vertical magnetic field, which rules out the use of the magnetic compass, and under the natural nocturnal sky. We argue that pervious experiments allow alternative interpretations, albeit unlikely. Our data independently confirm that European robins, like other nocturnal passerine migrants hitherto studied, use their stellar compass independently of their Internal Clock. Significance statement It is generally assumed since the classic experiments of Stephen Emlen performed in the 1960s that star compass of migrating songbirds is time-independent, i.e. that the birds use the pattern of constellations and not the angle of rotation of the starry sky. However, it has not been shown unequivocally, because early experiments did not consider the possibility that the birds relied on magnetic compass rather than on time-independent stellar compass system. Here, we show that stellar compass of European robins tested in the vertical magnetic field that did not provide compass information is indeed independent of the birds’ Internal Clock and cannot be manipulated by resetting this Clock. Cognitive challenges of learning the pattern of constellations, which is necessary to use time-independent star compass, are most fascinating and deserve detailed behavioural and neurobiological study.
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Further evidence of a time-independent stellar compass in a night-migrating songbird
Behavioral Ecology and Sociobiology, 2017Co-Authors: Alexander Pakhomov, Anna Anashina, Nikita ChernetsovAbstract:We tested whether European robins Erithacus rubecula have a time-independent stellar compass, i.e. whether they can use the stellar pattern for finding the seasonally appropriate migratory direction without reference to their Internal Clock. It has been claimed earlier on the basis of experiments with other nocturnal migrants, indigo buntings Passerina cyanea, pied flycatchers Ficedula hypoleuca and blackcaps Sylvia atricapilla, but none of the previous experiments was performed in the vertical magnetic field, which rules out the use of the magnetic compass, and under the natural nocturnal sky. We argue that pervious experiments allow alternative interpretations, albeit unlikely. Our data independently confirm that European robins, like other nocturnal passerine migrants hitherto studied, use their stellar compass independently of their Internal Clock. It is generally assumed since the classic experiments of Stephen Emlen performed in the 1960s that star compass of migrating songbirds is time-independent, i.e. that the birds use the pattern of constellations and not the angle of rotation of the starry sky. However, it has not been shown unequivocally, because early experiments did not consider the possibility that the birds relied on magnetic compass rather than on time-independent stellar compass system. Here, we show that stellar compass of European robins tested in the vertical magnetic field that did not provide compass information is indeed independent of the birds’ Internal Clock and cannot be manipulated by resetting this Clock. Cognitive challenges of learning the pattern of constellations, which is necessary to use time-independent star compass, are most fascinating and deserve detailed behavioural and neurobiological study.
Christof Fetzer - One of the best experts on this subject based on the ideXlab platform.
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SRDS - Adaptive Internal Clock Synchronization
2008 Symposium on Reliable Distributed Systems, 2008Co-Authors: Zbigniew Jerzak, R. Fach, Christof FetzerAbstract:Existing Clock synchronization algorithms assume a bounded Clock reading error. This, in turn, results in an inflexible design that typically requires node crashes whenever the given bound might be violated. We propose a novel, adaptive Internal Clock synchronization algorithm which allows to compute the deviation between the Clocks during runtime. The computed deviation can be propagated to the application layer to allow it to adapt its behavior according to the current Clock deviation. The contributions of this paper are: (1) a new specification of a relaxed Clock synchronization problem, and (2) a new Clock synchronization algorithm with a novel approach to dealing with crash failures.
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Integrating External and Internal Clock Synchronization
Real-Time Systems, 1997Co-Authors: Christof Fetzer, Flaviu CristianAbstract:We address the problem of how to integrate fault-tolerant external and Internal Clock synchronization. In this paper we propose a new external/Internal Clock synchronization algorithm which provides both external and Internal Clock synchronization for as long as a majority of the reference time servers (servers with access to reference time) stay correct. When half or more of the reference time servers are faulty, the algorithm degrades to a fault-tolerant Internal Clock synchronization algorithm. We prove that at least 2 F+1 reference time servers are necessary for achieving external Clock synchronization when up to F reference time servers can suffer arbitrary failures, thus the proposed algorithm provides maximum fault-tolerance. In this paper we also derive lower bounds for the best maximum external deviation achievable in standard mode and the best drift rate achievable in degraded mode. Our algorithm is optimal with respect to these two bounds: (1) the maximum external deviation is optimal in standard mode, and (2) the drift rate of the Clocks is optimal in standard and degraded mode.
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probabilistic Internal Clock synchronization
Symposium on Reliable Distributed Systems, 1994Co-Authors: Flaviu Cristian, Christof FetzerAbstract:We propose an improved probabilistic method for reading remote Clocks in systems subject to unbounded communication delays and use this method to design a fault-tolerant probabilistic Internal Clock synchronization protocol. This protocol masks Clock reading failures and arbitrary failures of processes. Because of probabilistic reading, our protocol achieves better synchronization precisions than those achievable by previously known deterministic algorithms. Another advantage of the proposed protocol is that it uses a linear, instead of quadratic, number of messages, and that message exchanges are staggered in time instead of all happening in narrow synchronization intervals. The drift rate of the synchronized Clocks is optimal. >
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An optimal Internal Clock synchronization algorithm
COMPASS '95 Proceedings of the Tenth Annual Conference on Computer Assurance Systems Integrity Software Safety and Process Security', 1Co-Authors: Christof Fetzer, Flaviu CristianAbstract:We propose an optimal convergence function for achieving fault-tolerant, Internal Clock synchronization in the presence of arbitrary process and Clock failures. The differential fault-tolerant midpoint convergence function guarantees an optimal maximum correction, an optimal maximum drift rate, and an optimal maximum deviation. The proposed convergence function is simple and easy to compute. It bounds the maximum drift rate of correct Clocks by the maximum drift rate of a correct hardware Clock. The maximum correction is limited by the maximum drift between two correct hardware Clocks during one round. The maximum deviation is approximately 4/spl Lambda/+4/spl rho/r/sub max/, where /spl Lambda/ is the maximum remote Clock reading error, /spl rho/ is the maximum drift rate of a correct hardware Clock and r/sub max/ is the maximum duration of a synchronization round.
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SRDS - Probabilistic Internal Clock synchronization
Proceedings of IEEE 13th Symposium on Reliable Distributed Systems, 1Co-Authors: Flaviu Cristian, Christof FetzerAbstract:We propose an improved probabilistic method for reading remote Clocks in systems subject to unbounded communication delays and use this method to design a fault-tolerant probabilistic Internal Clock synchronization protocol. This protocol masks Clock reading failures and arbitrary failures of processes. Because of probabilistic reading, our protocol achieves better synchronization precisions than those achievable by previously known deterministic algorithms. Another advantage of the proposed protocol is that it uses a linear, instead of quadratic, number of messages, and that message exchanges are staggered in time instead of all happening in narrow synchronization intervals. The drift rate of the synchronized Clocks is optimal. >
Alexander Pakhomov - One of the best experts on this subject based on the ideXlab platform.
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Further evidence of a time-independent stellar compass in a night-migrating songbird
Behavioral Ecology and Sociobiology, 2017Co-Authors: Alexander Pakhomov, Anna Anashina, Nikita ChernetsovAbstract:We tested whether European robins Erithacus rubecula have a time-independent stellar compass, i.e. whether they can use the stellar pattern for finding the seasonally appropriate migratory direction without reference to their Internal Clock. It has been claimed earlier on the basis of experiments with other nocturnal migrants, indigo buntings Passerina cyanea , pied flycatchers Ficedula hypoleuca and blackcaps Sylvia atricapilla , but none of the previous experiments was performed in the vertical magnetic field, which rules out the use of the magnetic compass, and under the natural nocturnal sky. We argue that pervious experiments allow alternative interpretations, albeit unlikely. Our data independently confirm that European robins, like other nocturnal passerine migrants hitherto studied, use their stellar compass independently of their Internal Clock. Significance statement It is generally assumed since the classic experiments of Stephen Emlen performed in the 1960s that star compass of migrating songbirds is time-independent, i.e. that the birds use the pattern of constellations and not the angle of rotation of the starry sky. However, it has not been shown unequivocally, because early experiments did not consider the possibility that the birds relied on magnetic compass rather than on time-independent stellar compass system. Here, we show that stellar compass of European robins tested in the vertical magnetic field that did not provide compass information is indeed independent of the birds’ Internal Clock and cannot be manipulated by resetting this Clock. Cognitive challenges of learning the pattern of constellations, which is necessary to use time-independent star compass, are most fascinating and deserve detailed behavioural and neurobiological study.
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Further evidence of a time-independent stellar compass in a night-migrating songbird
Behavioral Ecology and Sociobiology, 2017Co-Authors: Alexander Pakhomov, Anna Anashina, Nikita ChernetsovAbstract:We tested whether European robins Erithacus rubecula have a time-independent stellar compass, i.e. whether they can use the stellar pattern for finding the seasonally appropriate migratory direction without reference to their Internal Clock. It has been claimed earlier on the basis of experiments with other nocturnal migrants, indigo buntings Passerina cyanea, pied flycatchers Ficedula hypoleuca and blackcaps Sylvia atricapilla, but none of the previous experiments was performed in the vertical magnetic field, which rules out the use of the magnetic compass, and under the natural nocturnal sky. We argue that pervious experiments allow alternative interpretations, albeit unlikely. Our data independently confirm that European robins, like other nocturnal passerine migrants hitherto studied, use their stellar compass independently of their Internal Clock. It is generally assumed since the classic experiments of Stephen Emlen performed in the 1960s that star compass of migrating songbirds is time-independent, i.e. that the birds use the pattern of constellations and not the angle of rotation of the starry sky. However, it has not been shown unequivocally, because early experiments did not consider the possibility that the birds relied on magnetic compass rather than on time-independent stellar compass system. Here, we show that stellar compass of European robins tested in the vertical magnetic field that did not provide compass information is indeed independent of the birds’ Internal Clock and cannot be manipulated by resetting this Clock. Cognitive challenges of learning the pattern of constellations, which is necessary to use time-independent star compass, are most fascinating and deserve detailed behavioural and neurobiological study.
John H. Wearden - One of the best experts on this subject based on the ideXlab platform.
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What speeds up the Internal Clock? Effects of clicks and flicker on duration judgements and reaction time.
Quarterly journal of experimental psychology (2006), 2016Co-Authors: John H. Wearden, Emily A Williams, Luke JonesAbstract:Four experiments investigated the effect of pre-stimulus events on judgements of the subjective duration of tones that they preceded. Experiments 1 to 4 used click trains, flickering squares, expanding circles, and white noise as pre-stimulus events and showed that (a) periodic clicks appeared to “speed up” the pacemaker of an Internal Clock but that the effect wore off over a click-free delay, (b) aperiodic click trains, and visual stimuli in the form of flickering squares and expanding circles, also produced similar increases in estimated tone duration, as did white noise, although its effect was weaker. A fifth experiment examined the effects of periodic flicker on reaction time and showed that, as with periodic clicks in a previous experiment, reaction times were shorter when preceded by flicker than without.
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Slowing down an Internal Clock: implications for accounts of performance on four timing tasks.
Quarterly journal of experimental psychology (2006), 2008Co-Authors: John H. WeardenAbstract:An experiment investigated the potential effects of lowering arousal on performance on time perception tasks. Four participant groups received different tasks: Normal and episodic temporal generalization, bisection, and verbal estimation, all involving judgements of the duration of visual stimuli. Self-rated arousal during the experimental session was lowered by spacing experimental trials approximately 10 s apart. Between the early and late blocks of the experiment, performance changed on normal temporal generalization and verbal estimation, but not on episodic temporal generalization and bisection. The changes were consistent with the idea that the pacemaker of the participant's Internal Clock had been slowed down by the slow trial spacing. Results suggested that bisection was based on a criterion that adjusted during the experiment, whereas verbal estimation was based on preexisting standards, or those established early in the experiment.
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Speeding up an Internal Clock in children? Effects of visual flicker on subjective duration.
The Quarterly journal of experimental psychology. B Comparative and physiological psychology, 2002Co-Authors: Sylvie Droit-volet, John H. WeardenAbstract:Children of 3, 5, and 8 years of age were trained on a temporal bisection task where visual stimuli in the form of blue circles of 200 and 800 ms or 400 and 1600 ms duration, preceded by a 5-s white circle, served as the short and long standards. Following discrimination training between the standards, stimuli in the ranges 200-800 ms or 400-1600 ms were presented with the white circle either constant or flickering. Relative to the constant white circle, the flicker (1) increased the proportion of “long” responses (responses appropriate to the long standard), (2) shifted the psychophysical functions to the left, (3) decreased bisection point values, at all ages, and (4) did not systematically affect measures of temporal sensitivity, such as difference limen and Weber ratio. The results were consistent with the idea that the repetitive flicker had increased the speed of the pacemaker of an Internal Clock in children as young as 3 years. The “pacemaker speed” interpretation of the results was further streng...
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Speeding up and (…relatively…) slowing down an Internal Clock in humans
Behavioural processes, 1999Co-Authors: John H. Wearden, K Philpott, T WinAbstract:Two experiments used click-trains to manipulate the subjective duration of stimuli they preceded, in attempts to demonstrate relative slowing down of the pacemaker of a hypothesized Internal Clock. Experiment 1 used a pair comparison procedure, where two tones presented on each trial in fact had the same duration. In the conditions of particular interest, the first tone was preceded by clicks (thus putatively timed with a faster Clock), the other presented without (thus timed normally). The reverse condition (no-clicks/clicks) was also used. Judgements of the relative duration of the stimuli were shifted in both directions (i.e. first tone longer than second and vice versa) by the manipulation, consistent with relative speeding up and slowing down of the pacemaker. Experiment 2 used the popular bisection method, with 200- and 800-ms tones used as the Short and Long standards for the task. After standard presentations, subjects were required to classify a range of comparison stimuli (from 200 to 800 ms in 100-ms steps) in terms of their similarity to one or the other of the standards. In one condition the comparison stimuli were preceded by clicks (thus timed 'fast') and the standards were presented without clicks (thus timed 'normally'); in another condition the clicks preceded the standards but not the comparisons. The psychophysical function obtained from the bisection procedure shifted in opposite directions with the different manipulations, consistent with both relative 'speeding up' and 'slowing down' of the pacemaker of the Internal Clock.
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Speeding up an Internal Clock in humans? Effects of click trains on subjective duration
Journal of experimental psychology. Animal behavior processes, 1996Co-Authors: Ian S. Penton-voak, Helen Edwards, Andrew Percival, John H. WeardenAbstract:Four experiments investigated the effect of trains of clicks (usually 5 s long and at 5 or 25 Hz) on subjective duration in humans, as previous research had suggested that such a manipulation would speed up the pacemaker of an Internal Clock by increasing participants' arousal. The four experiments used temporal generalization, pair comparison of duration, verbal estimation, and production of short durations. In all cases, preceding the durations to be judged by clicks changed their subjective length in a manner broadly consistent with the idea that pacemaker speed was increased, by an average of about 10%.
Anna Anashina - One of the best experts on this subject based on the ideXlab platform.
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Further evidence of a time-independent stellar compass in a night-migrating songbird
Behavioral Ecology and Sociobiology, 2017Co-Authors: Alexander Pakhomov, Anna Anashina, Nikita ChernetsovAbstract:We tested whether European robins Erithacus rubecula have a time-independent stellar compass, i.e. whether they can use the stellar pattern for finding the seasonally appropriate migratory direction without reference to their Internal Clock. It has been claimed earlier on the basis of experiments with other nocturnal migrants, indigo buntings Passerina cyanea , pied flycatchers Ficedula hypoleuca and blackcaps Sylvia atricapilla , but none of the previous experiments was performed in the vertical magnetic field, which rules out the use of the magnetic compass, and under the natural nocturnal sky. We argue that pervious experiments allow alternative interpretations, albeit unlikely. Our data independently confirm that European robins, like other nocturnal passerine migrants hitherto studied, use their stellar compass independently of their Internal Clock. Significance statement It is generally assumed since the classic experiments of Stephen Emlen performed in the 1960s that star compass of migrating songbirds is time-independent, i.e. that the birds use the pattern of constellations and not the angle of rotation of the starry sky. However, it has not been shown unequivocally, because early experiments did not consider the possibility that the birds relied on magnetic compass rather than on time-independent stellar compass system. Here, we show that stellar compass of European robins tested in the vertical magnetic field that did not provide compass information is indeed independent of the birds’ Internal Clock and cannot be manipulated by resetting this Clock. Cognitive challenges of learning the pattern of constellations, which is necessary to use time-independent star compass, are most fascinating and deserve detailed behavioural and neurobiological study.
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Further evidence of a time-independent stellar compass in a night-migrating songbird
Behavioral Ecology and Sociobiology, 2017Co-Authors: Alexander Pakhomov, Anna Anashina, Nikita ChernetsovAbstract:We tested whether European robins Erithacus rubecula have a time-independent stellar compass, i.e. whether they can use the stellar pattern for finding the seasonally appropriate migratory direction without reference to their Internal Clock. It has been claimed earlier on the basis of experiments with other nocturnal migrants, indigo buntings Passerina cyanea, pied flycatchers Ficedula hypoleuca and blackcaps Sylvia atricapilla, but none of the previous experiments was performed in the vertical magnetic field, which rules out the use of the magnetic compass, and under the natural nocturnal sky. We argue that pervious experiments allow alternative interpretations, albeit unlikely. Our data independently confirm that European robins, like other nocturnal passerine migrants hitherto studied, use their stellar compass independently of their Internal Clock. It is generally assumed since the classic experiments of Stephen Emlen performed in the 1960s that star compass of migrating songbirds is time-independent, i.e. that the birds use the pattern of constellations and not the angle of rotation of the starry sky. However, it has not been shown unequivocally, because early experiments did not consider the possibility that the birds relied on magnetic compass rather than on time-independent stellar compass system. Here, we show that stellar compass of European robins tested in the vertical magnetic field that did not provide compass information is indeed independent of the birds’ Internal Clock and cannot be manipulated by resetting this Clock. Cognitive challenges of learning the pattern of constellations, which is necessary to use time-independent star compass, are most fascinating and deserve detailed behavioural and neurobiological study.