38 research outputs found
Ferroelectricity of Ice Nanotubes inside Carbon Nanotubes
We report that ice nanotubes with odd number of side faces inside carbon
nanotubes exhibit spontaneous electric polarization along its axes direction by
using molecular dynamics simulations. The mechanism of this nanoscale
quasi-one-dimensional ferroelectricity is due to low dimensional confinement
and the orientational order of hydrogen bonds. These ferroelectric fiber
structural materials are different from traditional perovskite structural bulk
materials.Comment: 4 pages and 4 figure
Bulk-fragment and tube-like structures of AuN (N=2-26)
Using the relativistic all-electron density-functional calculations on the
AuN (N=2-26) in the generalized gradient approximation, combined with the
guided simulated annealing, we have found that the two- to three-dimensional
structural transition for AuN occurs between N=13 and 15, and the AuN (16<= N
<=25) prefer also the pyramid-based bulk fragment structures in addition to the
Au20. More importantly, the tubelike structures are found to be the most stable
for Au24 and Au26, offering another powerful structure competitor with other
isomers, e.g., amorphous, bulk fragment, and gold fullerene. The mechanism to
cause these unusual AuN may be attributed to the stronger s-d hybridization and
the d-d interaction enhanced by the relativistic effects.Comment: 12 pages and 3 figure
Structure-dependent ferroelectricity of niobium clusters (NbN, N=2-52)
The ground-state structures and ferroelectric properties of NbN (N=2-52) have
been investigated by a combination of density-functional theory (DFT) in the
generalized gradient approximation (GGA) and an unbiased global search with the
guided simulated annealing. It is found that the electric dipole moment (EDM)
exists in the most of NbN and varies considerably with their sizes. And the
larger NbN (N>=25) prefer the amorphous packing. Most importantly, our
numerical EDM values of NbN (N>=38) exhibit an extraordinary even-odd
oscillation, which is well consistent with the experimental observation,
showing a close relationship with the geometrical structures of NbN. Finally,
an inverse coordination number (ICN) function is proposed to account for the
structural relation of the EDM values, especially their even-odd oscillations
starting from Nb38.Comment: 11 pages and 4 figure
Genomic and biologic comparisons of cyprinid herpesvirus 3 strains
Cyprinid herpesvirus 3 (CyHV-3) is the archetypal fish alloherpesvirus and the etiologic agent of a lethal disease in common and koi carp. To date, the genome sequences of only four CyHV-3 isolates have been published, but no comparisons of the biologic properties of these strains have been reported. We have sequenced the genomes of a further seven strains from various geographical sources, and have compared their growth in vitro and virulence in vivo. The major findings were: (i) the existence of the two genetic lineages previously described as European and Asian was confirmed, but inconsistencies between the geographic origin and genotype of some strains were revealed; (ii) potential inter-lineage recombination was detected in one strain, which also suggested the existence of a third, as yet unidentified lineage; (iii) analysis of genetic disruptions led to the identification of non-essential genes and their potential role in virulence; (iv) comparison of the in vitro and in vivo properties of strains belonging to the two lineages revealed that inter-lineage polymorphisms do not contribute to the differences in viral fitness observed; and (v) a negative correlation was observed among strains between viral growth in vitro and virulence in vivo. This study illustrates the importance of coupling genomic and biologic comparisons of viral strains in order to enhance understanding of viral evolution and pathogenesis
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Blumenols as shoot markers of root symbiosis with arbuscular mycorrhizal fungi.
High-through-put (HTP) screening for functional arbuscular mycorrhizal fungi (AMF)-associations is challenging because roots must be excavated and colonization evaluated by transcript analysis or microscopy. Here we show that specific leaf-metabolites provide broadly applicable accurate proxies of these associations, suitable for HTP-screens. With a combination of untargeted and targeted metabolomics, we show that shoot accumulations of hydroxy- and carboxyblumenol C-glucosides mirror root AMF-colonization in Nicotiana attenuata plants. Genetic/pharmacologic manipulations indicate that these AMF-indicative foliar blumenols are synthesized and transported from roots to shoots. These blumenol-derived foliar markers, found in many di- and monocotyledonous crop and model plants (Solanum lycopersicum, Solanum tuberosum, Hordeum vulgare, Triticum aestivum, Medicago truncatula and Brachypodium distachyon), are not restricted to particular plant-AMF interactions, and are shown to be applicable for field-based QTL mapping of AMF-related genes