2,925 research outputs found
Nonlinear thermal transport and negative differential thermal conductance in graphene nanoribbons
We employ classical molecular dynamics to study the nonlinear thermal
transport in graphene nanoribbons (GNRs). For GNRs under large temperature
biases beyond linear response regime, we have observed the onset of negative
differential thermal conductance (NDTC). NDTC is tunable by varying the manner
of applying the temperature biases. NDTC is reduced and eventually disappears
when the length of the GNR increases. We have also observed NDTC in triangular
GNRs, where NDTC exists only when the heat current is from the narrower to the
wider end. These effects may be useful in nanoscale thermal managements and
thermal signal processing utilizing GNRs.Comment: 5 pages, 4 figure
Acoustically evoked potentials in two cephalopods inferred using the auditory brainstem response (ABR) approach
It is still a matter of debate whether cephalopods can detect sound frequencies above 400 Hz. So far there is no proof for the detection of underwater sound above 400 Hz via a physiological approach. The controversy of whether cephalopods have a sound detection ability above 400 Hz was tested using the auditory brainstem response (ABR) approach, which has been successfully applied in fish, crustaceans, amphibians, reptiles and birds. Using ABR we found that auditory evoked potentials can be obtained in the frequency range 400 to 1500 Hz (Sepiotheutis lessoniana) and 400 to 1000 Hz (Octopus vulgaris), respectively. The thresholds of S. lessoniana were generally lower than those of O. vulgaris
Observation of Spin Hall Effect in Weyl Semimetal WTe2 at Room Temperature
Discovery of topological Weyl semimetals has revealed the opportunities to
realize several extraordinary physical phenomena in condensed matter physics.
Specifically, these semimetals with strong spin-orbit coupling, broken
inversion symmetry and novel spin texture are predicted to exhibit a large spin
Hall effect that can efficiently convert the charge current to a spin current.
Here we report the direct experimental observation of a large spin Hall and
inverse spin Hall effects in Weyl semimetal WTe2 at room temperature obeying
Onsager reciprocity relation. We demonstrate the detection of the pure spin
current generated by spin Hall phenomenon in WTe2 by making van der Waals
heterostructures with graphene, taking advantage of its long spin coherence
length and spin transmission at the heterostructure interface. These
experimental findings well supported by ab initio calculations show a large
charge-spin conversion efficiency in WTe2; which can pave the way for
utilization of spin-orbit induced phenomena in spintronic memory and logic
circuit architectures
Large deformation of spherical vesicle studied by perturbation theory and Surface evolver
With tangent angle perturbation approach the axial symmetry deformation of a
spherical vesicle in large under the pressure changes is studied by the
elasticity theory of Helfrich spontaneous curvature model.Three main results in
axial symmetry shape: biconcave shape, peanut shape, and one type of myelin are
obtained. These axial symmetry morphology deformations are in agreement with
those observed in lipsome experiments by dark-field light microscopy [Hotani,
J. Mol. Biol. 178, (1984) 113] and in the red blood cell with two thin
filaments (myelin) observed in living state (see, Bessis, Living Blood Cells
and Their Ultrastructure, Springer-Verlag, 1973). Furthermore, the biconcave
shape and peanut shape can be simulated with the help of a powerful software,
Surface Evolver [Brakke, Exp. Math. 1, 141 (1992) 141], in which the
spontaneous curvature can be easy taken into account.Comment: 16 pages, 6 EPS figures and 2 PS figure
Evidence of a universal and isotropic 2\Delta/kBTC ratio in 122-type iron pnictide superconductors over a wide doping range
We have systematically investigated the doping and the directional dependence
of the gap structure in the 122-type iron pnictide superconductors by point
contact Andreev reflection spectroscopy. The studies were performed on single
crystals of Ba1-xKxFe2As2 (x = 0.29, 0.49, and 0.77) and SrFe1.74Co0.26As2 with
a sharp tip of Pb or Au pressed along the c-axis or the ab-plane direction. The
conductance spectra obtained on highly transparent contacts clearly show
evidence of a robust superconducting gap. The normalized curves can be well
described by the Blonder-Tinkham-Klapwijk model with a lifetime broadening. The
determined gap value scales very well with the transition temperature, giving
the 2{\Delta}/kBTC value of ~ 3.1. The results suggest the presence of a
universal coupling behavior in this class of iron pnictides over a broad doping
range and independent of the sign of the doping. Moreover, conductance spectra
obtained on c-axis junctions and ab-plane junctions indicate that the observed
gap is isotropic in these superconductors
Resonant peak splitting for ballistic conductance in magnetic superlattices
We investigate theoretically the resonant splitting of ballistic conductance
peaks in magnetic superlattices. It is found that, for magnetic superlattices
with periodically arranged identical magnetic-barriers, there exists a
general -fold resonant peak splitting rule for ballistic conductance,
which is the analogy of the -fold resonant splitting for transmission in
-barrier electric superlattices (R. Tsu and L. Esaki, Appl. Phys. Lett. {\bf
22}, 562 (1973)).Comment: 9 pages, 3 figures, latex forma
A polymorph of tetraethylammonium chloride
The structure of the title compound, C8H20N+·Cl−, is compared with a polymorph that was described earlier in the same space group. Differences in the conformations of the ethyl groups of the cation exist between the polymorphs. This study is given here in order to provide additional unit-cell data for use in qualitative identification of crystalline samples obtained in syntheses in which Et4N+·Cl− is either used or generated
The conserved aromatic residue W-122 is a determinant of potyviral coat protein stability, replication, and cell-to-cell movement in plants
Coat proteins (CPs) play critical roles in potyvirus cell-to-cell movement. However, the underlying mechanism controlling them remains unclear. Here, we show that substitutions of alanine, glutamic acid, or lysine for the conserved residue tryptophan at position 122 (W-122) in tobacco vein banding mosaic virus (TVBMV) CP abolished virus cell-to-cell movement in Nicotiana benthamiana plants. In agroinfiltrated N. benthamiana leaf patches, both the CP and RNA accumulation levels of three W-122 mutant viruses were significantly reduced compared with those of wild-type TVBMV, and CP accumulated to a low level similar to that of a replication-deficient mutant. The results of polyprotein transient expression experiments indicated that CP instability was responsible for the significantly low CP accumulation levels of the three W-122 mutant viruses. The substitution of W-122 did not affect CP plasmodesmata localization or virus particle formation; however, the substitution significantly reduced the number of virus particles. The wild-type TVBMV CP could complement the reduced replication and abolished cell-to-cell movement of the mutant viruses. When the codon for W-122 was mutated to that for a different aromatic residue, phenylalanine or tyrosine, the resultant mutant viruses moved systemically and accumulated up to 80% of the wild-type TVBMV level. Similar results were obtained for the corresponding amino acids of W-122 in the watermelon mosaic virus and potato virus Y CPs. Therefore, we conclude that the aromatic ring in W-122 in the core domain of the potyviral CP is critical for cell-to-cell movement through the effects on CP stability and viral replication.Peer reviewe
Variability of Soft X-ray Spectral Shape in Blazars Observed by ROSAT
In paper 1 (Cheng et al. 2001) we have shown that the soft X-ray spectra of
two types of Seyfert 1 galaxies statistically vary differently with increasing
intensity. In order to understand how the spectrum of blazars changes, the
spectral shape variability of 18 blazars observed by ROSAT/PSPC mode are
studied by presenting the correlation of Hardness Ratio 1 versus Count Rates
(HR1-CTs). According to our criteria, 10 blazars show a positive HR1-CTs
relation, and only 2 blazars display an anti-correlation of HR1 versus CTs. The
rest 6 blazars do not indicate any clear correlation. From these we can see
that most blazars of our sample statistically show a hardening spectrum during
overall flux increase, though some vary randomly. By investigating the photon
index of these objects and different radiation theories, we argue that the
dominance of the synchrotron or inverse Compton emission in the soft X-ray band
may interpret the dichotomy of spectral variability well, and that different
spectral variations might represent a sequence of synchrotron peaked frequency.Comment: 11 pages, 3 figures, CJA
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