20,397 research outputs found
A rapid staining-assisted wood sampling method for PCR-based detection of pine wood nematode Bursaphelenchus xylophilus in Pinus massoniana wood tissue
For reasons of unequal distribution of more than one nematode species in wood, and limited
availability of wood samples required for the PCR-based method for detecting pinewood nematodes in
wood tissue of Pinus massoniana, a rapid staining-assisted wood sampling method aiding PCR-based
detection of the pine wood nematode Bursaphelenchus xylophilus (Bx) in small wood samples of P.
massoniana was developed in this study. This comprised a series of new techniques: sampling, mass
estimations of nematodes using staining techniques, and lowest limit Bx nematode mass determination
for PCR detection. The procedure was undertaken on three adjoining 5-mg wood cross-sections, of
0.5 · 0.5 · 0.015 cm dimension, that were cut from a wood sample of 0.5 · 0.5 · 0.5 cm initially, then
the larger wood sample was stained by acid fuchsin, from which two 5-mg wood cross-sections (that
adjoined the three 5-mg wood cross-sections, mentioned above) were cut. Nematode-staining-spots
(NSSs) in each of the two stained sections were counted under a microscope at 100· magnification. If
there were eight or more NSSs present, the adjoining three sections were used for PCR assays. The
B. xylophilus – specific amplicon of 403 bp (DQ855275) was generated by PCR assay from 100.00% of
5-mg wood cross-sections that contained more than eight Bx NSSs by the PCR assay. The entire
sampling procedure took only 10 min indicating that it is suitable for the fast estimation of nematode
numbers in the wood of P. massonina as the prelimary sample selections for other more expensive
Bx-detection methods such as PCR assay
Resolving and Tuning Mechanical Anisotropy in Black Phosphorus via Nanomechanical Multimode Resonance Spectromicroscopy
Black phosphorus (P) has emerged as a layered semiconductor with a unique
crystal structure featuring corrugated atomic layers and strong in-plane
anisotropy in its physical properties. Here, we demonstrate that the crystal
orientation and mechanical anisotropy in free-standing black P thin layers can
be precisely determined by spatially resolved multimode nanomechanical
resonances. This offers a new means for resolving important crystal orientation
and anisotropy in black P device platforms in situ beyond conventional optical
and electrical calibration techniques. Furthermore, we show that
electrostatic-gating-induced straining can continuously tune the mechanical
anisotropic effects on multimode resonances in black P electromechanical
devices. Combined with finite element modeling (FEM), we also determine the
Young's moduli of multilayer black P to be 116.1 and 46.5 GPa in the zigzag and
armchair directions, respectively.Comment: Main Text: 13 Pages, 4 Figures; Supplementary Information: 5 Pages, 2
Figures, 2 Table
Two-dimensional Superconductivity from Dimerization of Atomically Ordered AuTe2Se4/3 Cubes
The emergent phenomena such as superconductivity and topological phase
transitions can be observed in strict two-dimensional crystalline matters.
Artificial interfaces and one atomic thickness layers are typical 2D materials
of this kind. Although having 2D characters, most bulky layered compounds,
however, do not possess these striking properties. Here, we report the 2D
superconductivity in bulky AuTe2Se4/3,where the reduction in dimensionality is
achieved through inducing the elongated covalent Te-Te bonds. The
atomic-resolution images reveal that the Au, Te and Se are atomically ordered
in a cube, among which are Te-Te bonds of 3.18 A and 3.28 A. The
superconductivity at 2.85 K is discovered, which is unraveled to be the
quasi-2D nature owing to the BKT topological transition. The nesting of nearly
parallel Fermi sheets could give rise to strong electron-phonon coupling. It is
proposed to further depleting the thickness could result in more
topologically-related phenomena.Comment: 16 pages, 5 figures,To be published in Nature Communication
Origin of sawtooth domain walls in ferroelectrics
Domains and domain walls are among the key factors that determine the
performance of ferroelectric materials. In recent years, a unique type of
domain walls, i.e., the sawtooth-shaped domain walls, has been observed in
BiFeO and PbTiO. Here, we build a minimal model to reveal the
origin of these sawtooth-shaped domain walls. Incorporating this model into
Monte-Carlo simulations shows that (i) the competition between the long-range
Coulomb interaction (due to bound charges) and short-range interaction (due to
opposite dipoles) is responsible for the formation of these peculiar domain
walls and (ii) their relative strength is critical in determining the
periodicity of these sawtooth-shaped domain walls. Necessary conditions to form
such domain walls are also discussed
A link prediction-based method for identifying potential cooperation partners: A case study on four journals of informetrics
© 2018 Portland International Conference on Management of Engineering and Technology, Inc. (PICMET). Global academic exchange and cooperation have become an increasing trend in both academia and industry, but how to quickly and effectively identify potential partners is becoming an urgent problem. This paper proposes a link prediction-based model to help researchers identify partners from a large collection of academic articles in a given technological area. We initially construct a co-authorship network, and take a series of indices based on network and similarity of researchers into consideration. A fitting model of link prediction is then established, in which logistic regression analysis is involved. An empirical study on four journals of informetrics is conducted to demonstrate the reliability of the proposed method
Anisotropic nonlinear elasticity in a spherical bead pack: influence of the fabric anisotropy
Stress-strain measurements and ultrasound propagation experiments in glass
bead packs have been simultaneously conducted to characterize the
stress-induced anisotropy under uniaxial loading. These measurements, realized
respectively with finite and incremental deformations of the granular assembly,
are analyzed within the framework of the effective medium theory based on the
Hertz-Mindlin contact theory. Our work shows that both compressional and shear
wave velocities and consequently the incremental elastic moduli agree fairly
well with the effective medium model by Johnson et al. [J. Appl. Mech. 65, 380
(1998)], but the anisotropic stress ratio resulting from finite deformation
does not at all. As indicated by numerical simulations, the discrepancy may
arise from the fact that the model doesn't properly allow the grains to relax
from the affine motion approximation. Here we find that the interaction nature
at the grain contact could also play a crucial role for the relevant prediction
by the model; indeed, such discrepancy can be significantly reduced if the
frictional resistance between grains is removed. Another main experimental
finding is the influence of the inherent anisotropy of granular packs, realized
by different protocols of the sample preparation. Our results reveal that
compressional waves are more sensitive to the stress-induced anisotropy,
whereas the shear waves are more sensitive to the fabric anisotropy, not being
accounted in analytical effective medium models.Comment: 9 pages, 8 figure
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