Search results for "periodicity"
showing 10 items of 63 documents
Periodicity, morphisms, and matrices
2003
In 1965, Fine and Wilf proved the following theorem: if (fn)n≥0 and (gn)n≥0 are periodic sequences of real numbers, of period lengths h and k, respectively, and fn = gn for 0 ≤ n > h + k - gcd(h,k), then fn = gn for all n ≥ 0. Furthermore, the constant h + k - gcd(h,k) is best possible. In this paper, we consider some variations on this theorem. In particular, we study the case where fn ≤ gn, instead of fn = gn. We also obtain generalizations to more than two periods.We apply our methods to a previously unsolved conjecture on iterated morphisms, the decreasing length conjecture: if h : Σ* → Σ* is a morphism with |Σ|= n, and w is a word with |w| < |h(w)| < |h2(w)| < ... < |hk(w)|, then k ≤ n.
Comparison of the 45-Second/15-Second Intermittent Running Field Test and the Continuous Treadmill Test
2012
Purposes:To compare the physiological responses and maximal aerobic running velocity (MAV) during an incremental intermittent (45-s run/15-s rest) field test (45-15FIT) vs an incremental continuous treadmill test (TR) and to demonstrate that the MAV obtained during 45-15FIT (MAV45-15) was relevant to elicit a high percentage of maximal oxygen uptake (VO2max) during a 30-s/30-s intermittent training session.Methods:Oxygen uptake (VO2), heart rate (HR), and lactate concentration ([La]) were measured in 20 subjects during 2 maximal incremental tests and four 15-min intermittent tests. The time spent above 90% and 95% VO2max (t90% and t95% VO2max, respectively) was determined.Results:Maximal ph…
Perceived Frequency of Domestic Violence against Women and Neighbourhood Social Disorder
2005
Regression analyses from a nationally representative sample of 10,235 adult Spaniards, provided in 1995 from the Spanish Demands of Security and Victimization Survey, showed a small and positive relationship between high neighbourhood social disorder and perceived frequency of domestic violence against women in Spanish families, after controlling for sociodemographic variables and size of city. Among sociodemographic variables, sex had the strongest association with neighbourhood social disorder, being more than twice as large as neighbourhood social disorder.
A NEW COMPLEXITY FUNCTION FOR WORDS BASED ON PERIODICITY
2013
Motivated by the extension of the critical factorization theorem to infinite words, we study the (local) periodicity function, i.e. the function that, for any position in a word, gives the size of the shortest square centered in that position. We prove that this function characterizes any binary word up to exchange of letters. We then introduce a new complexity function for words (the periodicity complexity) that, for any position in the word, gives the average value of the periodicity function up to that position. The new complexity function is independent from the other commonly used complexity measures as, for instance, the factor complexity. Indeed, whereas any infinite word with bound…
Sequential effects in the lexical decision task: the role of the item frequency of the previous trial.
2003
Two lexical decision experiments were conducted to determine whether there is a specific, localized influence of the item frequency of consecutive trials (i.e., first-order sequential effects) when the trials are not related to each other. Both low-frequency words and nonwords were influenced by the frequency of the precursor word (Experiment 1). In contrast, high-frequency words showed little sensitivity to the frequency of the precursor word (Experiment 2), although they showed longer reaction times for word trials preceded by a nonword trial. The presence of sequential effects in the lexical decision task suggests that participants shift their response criteria on a trial-by-trial basis.
Day/night changes of pineal gland volume and pinealocyte nuclear size assessed over 10 consecutive days
1984
Previous studies aimed at elucidating day/night changes of pineal gland size and pinealocyte nuclear volume have yielded contradictory results. The aim of the present investigation was to examine the above parameters over a period of 10 successive days, at 6-hour intervals under a lighting regimen of LD 12:12 (7 a.m. to 7 p.m.). It was found that changes in pineal gland volume could not be correlated with the light/dark phases; instead, a rhythm with a two-day period was encountered. Pinealocyte nuclear volume, by contrast, showed clear circadian changes, exhibiting troughs during photophase and peaks during scotophase. In this experimental series, the karyometric results conformed to the m…
Early patterns of electrical activity in the developing cerebral cortex of humans and rodents.
2006
International audience; During prenatal and early postnatal development, the cerebral cortex exhibits synchronized oscillatory network activity that is believed to be essential for the generation of neuronal cortical circuits. The nature and functional role of these early activity patterns are of central interest in neuroscience. Much of the research is performed in rodents and in vitro, but how closely do these model systems relate to the human fetal brain? In this review, we compare observations in humans with in vivo and in vitro rodent data, focusing on particular oscillatory activity patterns that share many common features: delta brushes, spindle bursts and spindle-like oscillations. …
The frequency effect for pseudowords in the lexical decision task
2005
Four experiments were designed to investigate whether the frequency of words used to create pseudowords plays an important role in lexical decision. Computational models of the lexical decision task (e.g., the dual route cascaded model and the multiple read-out model) predict that latencies to low-frequency pseudowords should be faster than latencies to high-frequency pseudowords. Consistent with this prediction, results showed that when the pseudowords were created by replacing one internal letter of the base word (Experiments 1 and 3), high-frequency pseudowords yielded slower latencies than low-frequency pseudowords. However, this effect occurred only in the leading edge of the response …
Frequency format facilitates reasoning in simple numerical tasks.
2005
This study examined whether it is easier to reason in terms of frequencies or with percentages for simple numerical tasks. Research on probabilistic reasoning has shown that humans can draw correct inferences when problems are presented in terms of natural frequencies but not when in percentages. Whether the same effect can be observed in other numerically simple tasks which are not probabilistic was studied with 40 undergraduate students who volunteered for the experiment (13 men, 27 women; M age of 23 yr.). In a simple numerical task involving frequencies or percentages ( N = 20), their performance showed representation in frequencies facilitates the task.
An intrinsic neuronal-like network in the rat pineal gland
1999
Recent studies have shown that in rat pineal glands kept in vitro action potential-producing cell clusters are demonstrable. To test whether the clusters interact, multiple-unit recordings were carried out simultaneously from different clusters, with or without electrical stimulation. Clusters with rhythmic burst activity exhibit highly synchronized firing and electrical stimulation of one cluster elicits an immediate response in another one, apparently involving synapses but not gap junctions. It is hypothesized that the interacting clusters form a network. As the firing is affected by norepinephrine, acetylcholine and Ca2+, the network may monitor the interstitial concentrations of these …