An anisotropy
index seeks to quantify how directionally dependent the properties of a system are. In
this article, the focus is on quantifying the elastic anisotropy of crystalline
materials.
...Previous elastic anisotropy indices are reviewed and their shortcomings discussed. A new
scalar log-Euclidean anisotropy measure A
L
is
proposed, which overcomes these deficiencies. It is based on a distance measure in a
log-Euclidean space applied to fourth-rank elastic tensors.
A
L
is an absolute measure of anisotropy where the limiting
case of perfect isotropy yields zero. It is a universal measure of anisotropy applicable to all
crystalline materials. Specific examples of strong anisotropy are highlighted. A
supplementary
material provides an anisotropy table giving the
values of A
L
for 2,176 crystallite
compounds.
A recent survey in Germany revealed the wide presence of 'Candidatus Phytoplasma ulmi' in native elm stands. Accessions were studied for their genetic variability and phylogenetic relationship based ...on the conserved groEL and the variable imp gene. While the groEL sequences revealed a high intraspecific homology of more than 99%, the homology of the imp gene dropped to 71% between distantly related sequences. Twenty-nine groEL and 74 imp genotypes were distinguished based on polymorphic sites. Phylogenetic analysis of the groEL gene clustered all 'Ca. P. ulmi' strains and separated them from related phytoplasmas of the 16SrV group. The inferred phylogeny of the imp gene resulted in a different tree topology and separated the 'Ca. P. ulmi' genotypes into two clusters, one closely related to the flavescence dorée phytoplasma strain FD-D (16SrV-D), the other affiliated with the flavescence dorée phytoplasma strains FD-C and FD70 and the alder yellows phytoplasma (16SrV-C). In both phylograms, 'Ca. P. ulmi' genotypes from Scots elm trees formed a coherent cluster, while genotypes from European white elms and field elms grouped less strictly. The regional distribution pattern was congruent for some of the groEL and imp genotypes, but a strict linkage for all genotypes was not apparent.
Pirellula sp. strain 1 ("Rhodopirellula baltica") is a marine representative of the globally distributed and environmentally important bacterial order Planctomycetales. Here we report the complete ...genome sequence of a member of this independent phylum. With 7.145 megabases, Pirellula sp. strain 1 has the largest circular bacterial genome sequenced so far. The presence of all genes required for heterolactic acid fermentation, key genes for the interconversion of C1 compounds, and 110 sulfatases were unexpected for this aerobic heterotrophic isolate. Although Pirellula sp. strain 1 has a proteinaceous cell wall, remnants of genes for peptidoglycan synthesis were found. Genes for lipid A biosynthesis and homologues to the flagellar L- and P-ring protein indicate a former Gram-negative type of cell wall. Phylogenetic analysis of all relevant markers clearly affiliates the Planctomycetales to the domain Bacteria as a distinct phylum, but a deepest branching is not supported by our analyses.
Compacted DNA nanoparticles deliver transgenes efficiently to the lung following intrapulmonary dosing. Here we show that nucleolin, a protein known to shuttle between the nucleus, cytoplasm, and ...cell surface, is a receptor for DNA nanoparticles at the cell surface. By using surface plasmon resonance (SPR), we demonstrate that nucleolin binds to DNA nanoparticles directly. The presence of nucleolin on the surface of HeLa and 16HBEo- cells was confirmed by surface biotinylation assay and immunofluorescence. Rhodamine-labeled DNA nanoparticles colocalize with nucleolin on the cell surface, as well as in the cytoplasm and nucleus, but not with transferrin or markers of early endosome or lysosome following cellular uptake. Reducing nucleolin on the cell surface by serum-free medium or siRNA against nucleolin treatment leads to significant reduction in luciferase reporter gene activity, while overexpressing nucleolin has the opposite effect. Competition for binding to DNA nanoparticles with exogenous purified nucleolin decreases the transfection efficiency by 60–90% in a dose-dependent manner. Therefore, the data strongly suggest that cell surface nucleolin serves as a receptor for DNA nanoparticles, and that nucleolin is essential for internalization and/or transport of the nanoparticles from cell surface to the nucleus.
Herein we study the inverse problem on inferring depth profile of near-surface residual stress in a weakly anisotropic medium by boundary measurement of Rayleigh-wave dispersion if all other relevant ...material parameters of the elastic medium are known. Our solution of this inverse problem is based on a recently developed algorithm by which each term of a high-frequency asymptotic formula for dispersion relations can be computed for Rayleigh waves that propagate in various directions along the free surface of a vertically-inhomogeneous, prestressed, and weakly anisotropic half-space. As a prime example of possible applications we focus on a thick-plate sample of AA 7075-T651 aluminum alloy, which has one face treated by low plasticity burnishing (LPB) that induced a depth-dependent prestress at and immediately beneath the treated surface. We model the sample as a prestressed, weakly-textured orthorhombic aggregate of cubic crystallites and assume that by nondestructive and/or destructive measurements we have ascertained everything about the sample, including the LPB-induced prestress, before it is put into service. Under the supposition that the prestress be partially relaxed but other material parameters remain unchanged after the sample undergoes a period of service, we examine the possibility of inferring the depth profile of the partially relaxed stress by boundary measurement of Rayleigh-wave dispersion.
•This study concerns ultrasonic measurement of residual stress induced by low plasticity burnishing (LPB).•An aluminum thick-plate sample surface-treated by LPB serves as primary example.•Using Rayleigh-wave dispersion to infer near-surface depth profile of the stress is studied.•Such inference is possible if velocity measurements have ±0.1% accuracy and stress is the only unknown.•The usable frequency window where Δv∕v≈±0.1% determines the depth above which the stress-profile can be inferred.
This article considers the influence of incompressibility on the compliance and stiffness constants that appear in the weakly nonlinear theory of elasticity. The formulation first considers the ...incompressibility constraint applied to compliances, which gives explicit finite limits for the second-, third-, and fourth-order compliance constants. The stiffness/compliance relationships for each order are derived and used to determine the incompressible behavior of the second-, third-, and fourth-order stiffness constants. Unlike the compressible case, the fourth-order compliances are not found to be dependent on the fourth-order stiffnesses.
'Candidatus Magnetobacterium bavaricum' is unusual among magnetotactic bacteria (MTB) in terms of cell size (8-10 μm long, 1.5-2 μm in diameter), cell architecture, magnetotactic behaviour and its ...distinct phylogenetic position in the deep-branching Nitrospira phylum. In the present study, improved magnetic enrichment techniques permitted high-resolution scanning electron microscopy and energy dispersive X-ray analysis, which revealed the intracellular organization of the magnetosome chains. Sulfur globule accumulation in the cytoplasm point towards a sulfur-oxidizing metabolism of 'Candidatus M. bavaricum'. Detailed analysis of 'Candidatus M. bavaricum' microhabitats revealed more complex distribution patterns than previously reported, with cells predominantly found in low oxygen concentration. No correlation to other geochemical parameters could be observed. In addition, the analysis of a metagenomic fosmid library revealed a 34 kb genomic fragment, which contains 33 genes, among them the complete rRNA gene operon of 'Candidatus M. bavaricum' as well as a gene encoding a putative type IV RubisCO large subunit.
Genetic programs underlying multicellular morphogenesis and cellular differentiation are most often associated with eukaryotic organisms, but examples also exist in bacteria such as the formation of ...multicellular, spore-filled fruiting bodies in the order Myxococcales. Most members of the Myxococcales undergo a multicellular developmental program culminating in the formation of spore-filled fruiting bodies in response to starvation. To gain insight into the evolutionary history of fruiting body formation in Myxococcales, we performed a comparative analysis of the genomes and transcriptomes of five Myxococcales species, four of these undergo fruiting body formation (Myxococcus xanthus, Stigmatella aurantiaca, Sorangium cellulosum, and Haliangium ochraceum) and one does not (Anaeromyxobacter dehalogenans). Our analyses show that a set of 95 known M. xanthus development-specific genes--although suffering from a sampling bias--are overrepresented and occur more frequently than an average M. xanthus gene in S. aurantiaca, whereas they occur at the same frequency as an average M. xanthus gene in S. cellulosum and in H. ochraceum and are underrepresented in A. dehalogenans. Moreover, genes for entire signal transduction pathways important for fruiting body formation in M. xanthus are conserved in S. aurantiaca, whereas only a minority of these genes are conserved in A. dehalogenans, S. cellulosum, and H. ochraceum. Likewise, global gene expression profiling of developmentally regulated genes showed that genes that upregulated during development in M. xanthus are overrepresented in S. aurantiaca and slightly underrepresented in A. dehalogenans, S. cellulosum, and H. ochraceum. These comparative analyses strongly indicate that the genetic programs for fruiting body formation in M. xanthus and S. aurantiaca are highly similar and significantly different from the genetic program directing fruiting body formation in S. cellulosum and H. ochraceum. Thus, our analyses reveal an unexpected level of plasticity in the genetic programs for fruiting body formation in the Myxococcales and strongly suggest that the genetic program underlying fruiting body formation in different Myxococcales is not conserved. The evolutionary implications of this finding are discussed.
The first measurement of the helicity dependence of the photoproduction cross section of single neutral pions off protons is reported for photon energies from 600 to 2300 MeV, covering nearly the ...full solid angle. The data are compared to predictions from the SAID, MAID, and BnGa partial wave analyses. Strikingly large differences between data and predictions are observed, which are traced to differences in the helicity amplitudes of well-known and established resonances. Precise values for the helicity amplitudes of several resonances are reported.
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