1,601 research outputs found
Data-adaptive harmonic spectra and multilayer Stuart-Landau models
Harmonic decompositions of multivariate time series are considered for which
we adopt an integral operator approach with periodic semigroup kernels.
Spectral decomposition theorems are derived that cover the important cases of
two-time statistics drawn from a mixing invariant measure.
The corresponding eigenvalues can be grouped per Fourier frequency, and are
actually given, at each frequency, as the singular values of a cross-spectral
matrix depending on the data. These eigenvalues obey furthermore a variational
principle that allows us to define naturally a multidimensional power spectrum.
The eigenmodes, as far as they are concerned, exhibit a data-adaptive character
manifested in their phase which allows us in turn to define a multidimensional
phase spectrum.
The resulting data-adaptive harmonic (DAH) modes allow for reducing the
data-driven modeling effort to elemental models stacked per frequency, only
coupled at different frequencies by the same noise realization. In particular,
the DAH decomposition extracts time-dependent coefficients stacked by Fourier
frequency which can be efficiently modeled---provided the decay of temporal
correlations is sufficiently well-resolved---within a class of multilayer
stochastic models (MSMs) tailored here on stochastic Stuart-Landau oscillators.
Applications to the Lorenz 96 model and to a stochastic heat equation driven
by a space-time white noise, are considered. In both cases, the DAH
decomposition allows for an extraction of spatio-temporal modes revealing key
features of the dynamics in the embedded phase space. The multilayer
Stuart-Landau models (MSLMs) are shown to successfully model the typical
patterns of the corresponding time-evolving fields, as well as their statistics
of occurrence.Comment: 26 pages, double columns; 15 figure
Genome Dynamics Are Influenced by Food Source in Allogromia laticollaris Strain CSH (Foraminifera)
Across the eukaryotic tree of life, genomes vary within populations and within individuals during their life cycle. Understanding intraspecific genome variation in diverse eukaryotes is key to elucidating the factors that underlie this variation. Here, we characterize genome dynamics during the life cycle of Allogromia laticollaris strain CSH, a member of the Foraminifera, using fluorescence microscopy and reveal extensive variation in nuclear size and DNA content. Both nuclear size and DNA content are tightly correlated across a 700-fold range in cell volume. In contrast to models in yeast where nuclear size is determined solely by cell size, the relationship in A. laticollaris CSH differs according to both life cycle stage and food source. Feeding A. laticollaris CSH a diet that includes algae results in a 2-fold increase in DNA content in reproductive cells compared with a diet of bacteria alone. This difference in DNA content likely corresponds to increased fecundity, as reproduction occurs through segregation of the polyploid nucleus into numerous daughter nuclei. Environmentally mediated variation in DNA content may be a widespread phenomenon, as it has been previously reported in the plant flax and the flagellate Euglena. We hypothesize that DNA content is influenced by food in other single-celled eukaryotes with ploidy cycles and that this genome flexibility may enable these eukaryotes to maximize fitness across changing environmental conditions
An Evolutionary Reduction Principle for Mutation Rates at Multiple Loci
A model of mutation rate evolution for multiple loci under arbitrary
selection is analyzed. Results are obtained using techniques from Karlin (1982)
that overcome the weak selection constraints needed for tractability in prior
studies of multilocus event models. A multivariate form of the reduction
principle is found: reduction results at individual loci combine topologically
to produce a surface of mutation rate alterations that are neutral for a new
modifier allele. New mutation rates survive if and only if they fall below this
surface - a generalization of the hyperplane found by Zhivotovsky et al. (1994)
for a multilocus recombination modifier. Increases in mutation rates at some
loci may evolve if compensated for by decreases at other loci. The strength of
selection on the modifier scales in proportion to the number of germline cell
divisions, and increases with the number of loci affected. Loci that do not
make a difference to marginal fitnesses at equilibrium are not subject to the
reduction principle, and under fine tuning of mutation rates would be expected
to have higher mutation rates than loci in mutation-selection balance. Other
results include the nonexistence of 'viability analogous, Hardy-Weinberg'
modifier polymorphisms under multiplicative mutation, and the sufficiency of
average transmission rates to encapsulate the effect of modifier polymorphisms
on the transmission of loci under selection. A conjecture is offered regarding
situations, like recombination in the presence of mutation, that exhibit
departures from the reduction principle. Constraints for tractability are:
tight linkage of all loci, initial fixation at the modifier locus, and mutation
distributions comprising transition probabilities of reversible Markov chains.Comment: v3: Final corrections. v2: Revised title, reworked and expanded
introductory and discussion sections, added corollaries, new results on
modifier polymorphisms, minor corrections. 49 pages, 64 reference
Quasispecies Theory for Horizontal Gene Transfer and Recombination
We introduce a generalization of the parallel, or Crow-Kimura, and Eigen
models of molecular evolution to represent the exchange of genetic information
between individuals in a population. We study the effect of different schemes
of genetic recombination on the steady-state mean fitness and distribution of
individuals in the population, through an analytic field theoretic mapping. We
investigate both horizontal gene transfer from a population and recombination
between pairs of individuals. Somewhat surprisingly, these nonlinear
generalizations of quasi-species theory to modern biology are analytically
solvable. For two-parent recombination, we find two selected phases, one of
which is spectrally rigid. We present exact analytical formulas for the
equilibrium mean fitness of the population, in terms of a maximum principle,
which are generally applicable to any permutation invariant replication rate
function. For smooth fitness landscapes, we show that when positive epistatic
interactions are present, recombination or horizontal gene transfer introduces
a mild load against selection. Conversely, if the fitness landscape exhibits
negative epistasis, horizontal gene transfer or recombination introduce an
advantage by enhancing selection towards the fittest genotypes. These results
prove that the mutational deterministic hypothesis holds for quasi-species
models. For the discontinuous single sharp peak fitness landscape, we show that
horizontal gene transfer has no effect on the fitness, while recombination
decreases the fitness, for both the parallel and the Eigen models. We present
numerical and analytical results as well as phase diagrams for the different
cases.Comment: 54 pages; 8 figures; 12 tables; some typos corrected; to appear in
Phys. Rev.
Algorithm of calculation of energy consumption on the basis of differential model of the production task performed on machines with computer numeric control (CNC)
© Published under licence by IOP Publishing Ltd. The calculation algorithm, power consumption of all consumers involved in the operation and production tasks developed by the example of workplaces equipped with CNC machines is developed. The algorithm takes into account the actual status, operating modes and switching sequence of all electricity consumers
The influence of iron microstructure on tool capacity during cutting process
© Published under licence by IOP Publishing Ltd. An overview of machinability by cutting cast irons is given. The effect of the microstructure of cast iron on the tool's working capacity during cutting has been studied. The reasons for the tool failure during drilling are revealed
Energy planning in production shops with numerically controlled machine tools
© 2017, Allerton Press, Inc. A method is proposed for planning the energy expenditures in production buildings with numerically controlled machine tools. The calculations take account of the individual production operations, as well as the actual state of the machine-tool drives
Evolution of a behavior-linked microsatellite-containing element in the 5' flanking region of the primate AVPR1A gene
<p>Abstract</p> <p>Background</p> <p>The arginine vasopressin V1a receptor (V1aR) modulates social cognition and behavior in a wide variety of species. Variation in a repetitive microsatellite element in the 5' flanking region of the V1aR gene (<it>AVPR1A</it>) in rodents has been associated with variation in brain V1aR expression and in social behavior. In humans, the 5' flanking region of <it>AVPR1A </it>contains a tandem duplication of two ~350 bp, microsatellite-containing elements located approximately 3.5 kb upstream of the transcription start site. The first block, referred to as DupA, contains a polymorphic (GT)<sub>25 </sub>microsatellite; the second block, DupB, has a complex (CT)<sub>4</sub>-(TT)-(CT)<sub>8</sub>-(GT)<sub>24 </sub>polymorphic motif, known as RS3. Polymorphisms in RS3 have been associated with variation in sociobehavioral traits in humans, including autism spectrum disorders. Thus, evolution of these regions may have contributed to variation in social behavior in primates. We examined the structure of these regions in six ape, six monkey, and one prosimian species.</p> <p>Results</p> <p>Both tandem repeat blocks are present upstream of the <it>AVPR1A </it>coding region in five of the ape species we investigated, while monkeys have only one copy of this region. As in humans, the microsatellites within DupA and DupB are polymorphic in many primate species. Furthermore, both single (lacking DupB) and duplicated alleles (containing both DupA and DupB) are present in chimpanzee (<it>Pan troglodytes</it>) populations with allele frequencies of 0.795 and 0.205 for the single and duplicated alleles, respectively, based on the analysis of 47 wild-caught individuals. Finally, a phylogenetic reconstruction suggests two alternate evolutionary histories for this locus.</p> <p>Conclusion</p> <p>There is no obvious relationship between the presence of the RS3 duplication and social organization in primates. However, polymorphisms identified in some species may be useful in future genetic association studies. In particular, the presence of both single and duplicated alleles in chimpanzees provides a unique opportunity to assess the functional role of this duplication in contributing to variation in social behavior in primates. While our initial studies show no signs of directional selection on this locus in chimps, pharmacological and genetic association studies support a potential role for this region in influencing V1aR expression and social behavior.</p
Optimizing the regimes of Advanced LIGO gravitational wave detector for multiple source types
We develop here algorithms which allow to find regimes of signal-recycled
Fabry-Perot--Michelson interferometer (for example, Advanced LIGO), optimized
concurrently for two (binary inspirals + bursts) and three (binary inspirals +
bursts + millisecond pulsars) types of gravitational waves sources. We show
that there exists a relatevely large area in the interferometer parameters
space where the detector sensitivity to the first two kinds of sources differs
only by a few percent from the maximal ones for each kind of source. In
particular, there exists a specific regime where this difference is ~0.5 for
both of them. Furthermore we show that even more multipurpose regimes are also
possible, that provide significant sensitivity gain for millisecond pulsars
with only minor sensitivity degradation for binary inspirals and bursts.Comment: 10 pages, 14 figures, 3 tables. Minor corrections in main text are
done in version 2 and two plots and one table are added for the sake of
clarity of the obtained result
- …