82,357 research outputs found
Fine-Scale Mapping of the Nasonia Genome to Chromosomes Using a High-Density Genotyping Microarray
abstract: Nasonia, a genus of four closely related parasitoid insect species, is a model system for genetic research. Their haplodiploid genetics (haploid males and diploid females) and interfertile species are advantageous for the genetic analysis of complex traits and the genetic basis of species differences. A fine-scale genomic map is an important tool for advancing genetic studies in this system. We developed and used a hybrid genotyping microarray to generate a high-resolution genetic map that covers 79% of the sequenced genome of Nasonia vitripennis. The microarray is based on differential hybridization of species-specific oligos between N. vitripennis and Nasonia giraulti at more than 20,000 markers spanning the Nasonia genome. The map places 729 scaffolds onto the five linkage groups of Nasonia, including locating many smaller scaffolds that would be difficult to map by other means. The microarray was used to characterize 26 segmental introgression lines containing chromosomal regions from one species in the genetic background of another. These segmental introgression lines have been used for rapid screening and mapping of quantitative trait loci involved in species differences. Finally, the microarray is extended to bulk-segregant analysis and genotyping of other Nasonia species combinations. These resources should further expand the usefulness of Nasonia for studies of the genetic basis and architecture of complex traits and speciation.The final version of this article, as published in G3 - Genes|Genomes|Genetics, can be viewed online at: http://www.g3journal.org/content/3/2/20
Fine-scale characteristics of interplanetary sector
The structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions was studied. Such regions consist of intermediate (nonspiral) average field orientations in some cases, as well as a number of large angle directional discontinuities (DD's) on the fine scale (time scales 1 hour). Such DD's are found to be more similar to tangential than rotational discontinuities, to be oriented on average more nearly perpendicular than parallel to the ecliptic plane to be accompanied usually by a large dip ( 80%) in B and, with a most probable thickness of 3 x 10 to the 4th power km, significantly thicker previously studied. It is hypothesized that the observed structures represent multiple traversals of the global heliospheric current sheet due to local fluctuations in the position of the sheet. There is evidence that such fluctuations are sometimes produced by wavelike motions or surface corrugations of scale length 0.05 - 0.1 AU superimposed on the large scale structure
Effective behavior of nematic elastomer membranes
We derive the effective energy density of thin membranes of liquid crystal
elastomers as the Gamma-limit of a widely used bulk model. These membranes can
display fine-scale features both due to wrinkling that one expects in thin
elastic membranes and due to oscillations in the nematic director that one
expects in liquid crystal elastomers. We provide an explicit characterization
of the effective energy density of membranes and the effective state of stress
as a function of the planar deformation gradient. We also provide a
characterization of the fine-scale features. We show the existence of four
regimes: one where wrinkling and microstructure reduces the effective membrane
energy and stress to zero, a second where wrinkling leads to uniaxial tension,
a third where nematic oscillations lead to equi-biaxial tension and a fourth
with no fine scale features and biaxial tension. Importantly, we find a region
where one has shear strain but no shear stress and all the fine-scale features
are in-plane with no wrinkling
Unresolved fine-scale structure in solar coronal loop-tops
New and advanced space-based observing facilities continue to lower the
resolution limit and detect solar coronal loops in greater detail. We continue
to discover even finer sub-structures within coronal loop cross sections, in
order to understand the nature of the solar corona. Here, we push this lower
limit further to search for the finest coronal loop sub-structures, through
taking advantage of the resolving power of the Swedish 1- m Solar Telescope
(SST) / CRisp Imaging Spectro-Polarimeter (CRISP), together with
co-observations from the Solar Dynamics Observatory (SDO) / Atmospheric Image
Assembly (AIA). High resolution imaging of the chromospheric H-alpha 656.28 nm
spectral line core and wings can, under certain circumstances, allow one to
deduce the topology of the local magnetic environment of the solar atmosphere
where its observed. Here, we study post-flare coronal loops, which become
filled with evaporated chromosphere that rapidly condenses into chromospheric
clumps of plasma (detectable in H-alpha) known as a coronal rain, to
investigate their fine-scale structure. We identify, through analysis of three
datasets, large-scale catastrophic cooling in coronal loop-tops and the
existence of multi-thermal, multi-stranded sub-structures. Many cool strands
even extend fully-intact from loop-top to foot-point. We discover that coronal
loop fine-scale strands can appear bunched with as many as 8 parallel strands,
within an AIA coronal loop cross-section. The strand number density vs
cross-sectional width distribution, as detected by CRISP within AIA-defined
coronal loops, most-likely peaks at well below 100 km and currently 69% of the
sub-structure strands are statistically unresolved in AIA coronal loops.Comment: 10 pages, 10 figures, submitted to Ap
Pressure spectra for vortex models of fine-scale homogeneous turbulence
Pressure spectra at large wave numbers are calculated for Lundgren–Townsend vortex models of the fine scales of homogeneous turbulence. Specific results are given for the Burgers vortex and also for the Lundgren-strained spiral vortex. For the latter case, it is found that the contribution to the shell-summed spectrum produced by the interaction between the axisymmetric and nonaxisymmetric components of the velocity field is proportional to k^–7/3 (k=||k|| is the modulus of the wave number) in agreement with Kolmogorov-type dimensional arguments. Numerical estimates of the dimensionless prefactors for this component are obtained in Kolmogorov scaling variables and comparisons are made with results from the Batchelor–Kolmogorov theory, and with experimental measurement
Resolving the fine-scale structure in turbulent Rayleigh-Benard convection
We present high-resolution direct numerical simulation studies of turbulent
Rayleigh-Benard convection in a closed cylindrical cell with an aspect ratio of
one. The focus of our analysis is on the finest scales of convective
turbulence, in particular the statistics of the kinetic energy and thermal
dissipation rates in the bulk and the whole cell. The fluctuations of the
energy dissipation field can directly be translated into a fluctuating local
dissipation scale which is found to develop ever finer fluctuations with
increasing Rayleigh number. The range of these scales as well as the
probability of high-amplitude dissipation events decreases with increasing
Prandtl number. In addition, we examine the joint statistics of the two
dissipation fields and the consequences of high-amplitude events. We also have
investigated the convergence properties of our spectral element method and have
found that both dissipation fields are very sensitive to insufficient
resolution. We demonstrate that global transport properties, such as the
Nusselt number, and the energy balances are partly insensitive to insufficient
resolution and yield correct results even when the dissipation fields are
under-resolved. Our present numerical framework is also compared with
high-resolution simulations which use a finite difference method. For most of
the compared quantities the agreement is found to be satisfactory.Comment: 33 pages, 24 figure
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