Search results for "Periodicity"
showing 10 items of 63 documents
Synchronized rotation in swarms of magnetotactic bacteria.
2017
Self-organizing behavior has been widely reported in both natural and artificial systems, typically distinguishing between temporal organization (synchronization) and spatial organization (swarming). Swarming has been experimentally observed in systems of magnetotactic bacteria under the action of external magnetic fields. Here we present a model of ensembles of magnetotactic bacteria in which hydrodynamic interactions lead to temporal synchronization in addition to the swarming. After a period of stabilization during which the bacteria form a quasiregular hexagonal lattice structure, the entire swarm begins to rotate in a direction opposite to the direction of the rotation of the magnetic …
Billiards in magnetic fields: A molecular dynamics approach
2009
We present a computational scheme based on classical molecular dynamics to study chaotic billiards in static external magnetic fields. The method allows to treat arbitrary geometries and several interacting particles. We test the scheme for rectangular single-particle billiards in magnetic fields and find a sequence of regularity islands at integer aspect ratios. In the case of two Coulomb-interacting particles the dynamics is dominated by chaotic behavior. However, signatures of quasiperiodicity can be identified at weak interactions, as well as regular trajectories at strong magnetic fields. Our scheme provides a promising tool to monitor the classical limit of many-electron semiconductor…
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.
Stability under influence of noise with regulated periodicity
2008
A very simple stochastic differential equation with quasi-periodical multiplicative noise is investigated analytically. For fixed noise intensity the system can be stable at high noise periodicity and unstable at low noise periodicity.
Dynamics of the Selkov oscillator.
2018
A classical example of a mathematical model for oscillations in a biological system is the Selkov oscillator, which is a simple description of glycolysis. It is a system of two ordinary differential equations which, when expressed in dimensionless variables, depends on two parameters. Surprisingly it appears that no complete rigorous analysis of the dynamics of this model has ever been given. In this paper several properties of the dynamics of solutions of the model are established. With a view to studying unbounded solutions a thorough analysis of the Poincar\'e compactification of the system is given. It is proved that for any values of the parameters there are solutions which tend to inf…
Translocation time of periodically forced polymer chains.
2010
6 páginas, 11 figuras.-- PACS number(s): 36.20.-r, 05.40.-a, 87.15.A-, 87.10.-e
Distinctive amino acid residue periodicities in terminal sequences of type III and type I secreted proteins from proteobacteria
2007
AbstractThe Fourier transform (FT) method was applied to specify the distribution of 14 predefined groups of amino acids (64 residues) at both termini of annotated type III and type I secreted proteins from proteobacteria. Type I proteins displayed a higher occurrence of significant periodicities at both C-and N-termini, indicating potent features to discriminate between secretion types, particularly by the use of variables selected from the full periodicity profiles at 19 orders of FT. The Fishers linear discriminant analysis, together with the stepwise selection of variables throughout equal pairs of combinations for all predefined groups of residues, revealed the C-terminal harmonics of …
Prevalence and factors associated with circadian blood pressure patterns in hypertensive patients.
2009
Comment in Timing of antihypertensive therapy and circadian blood pressure pattern. [Hypertension. 2009] Timing of antihypertensive therapy and circadian blood pressure pattern. Almirall J, Martínez-Ocaña JC, Comas L. Hypertension. 2009 Jun; 53(6):e41; author reply e42. Epub 2009 May 4. Dipping comes of age: the importance of nocturnal blood pressure. [Hypertension. 2009]. Dipping comes of age: the importance of nocturnal blood pressure. O'Brien E. Hypertension. 2009 Mar; 53(3):446-7. Epub 2009 Jan 26.Nondipping in patients with hypertension. [Hypertension. 2009] Ambulatory blood pressure (BP) monitoring has become useful in the diagnosis and management of hypertensive individuals. In addit…
Evidence for a link between the Atlantic Multidecadal Oscillation and annual asthma mortality rates in the US
2019
AbstractAn association between climatic conditions and asthma mortality has been widely assumed. However, it is unclear whether climatic variations have a fingerprint on asthma dynamics over long time intervals. The aim of this study is to detect a possible correlation between climatic indices, namely the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation, and asthma mortality rates over the period from 1950 to 2015 in the contiguous US. To this aim, an analysis of non-stationary and non-linear signals was performed on time series of US annual asthma mortality rates, AMO and PDO indices to search for characteristic periodicities. Results revealed that asthma death rates evalu…
Complex dynamics, hidden attractors and continuous approximation of a fractional-order hyperchaotic PWC system
2018
In this paper, a continuous approximation to studying a class of PWC systems of fractionalorder is presented. Some known results of set-valued analysis and differential inclusions are utilized. The example of a hyperchaotic PWC system of fractional order is analyzed. It is found that without equilibria, the system has hidden attractors.