61,648 research outputs found
Periodic ripples in suspended graphene
We study the mechanism of wrinkling of suspended graphene, by means of
atomistic simulations. We argue that the structural instability under edge
compression is the essential physical reason for the formation of periodic
ripples in graphene. The ripple wavelength and out-of-plane amplitude are found
to obey 1/4-power scaling laws with respect to edge compression. Our results
also show that parallel displacement of the clamped boundaries can induce
periodic ripples, with oscillation amplitude roughly proportional to the 1/4
power of edge displacement. The results are fundamental to graphene's
applications in electronics.Comment: 5 Figure
General response theory of topologically stable Fermi points and its implications for disordered cases
We develop a general response theory of gapless Fermi points with nontrivial
topological charges for gauge and nonlinear sigma fields, which asserts that
the topological character of the Fermi points is embodied as the terms with
discrete coefficients proportional to the corresponding topological charges.
Applying the theory to the effective non-linear sigma models for topological
Fermi points with disorders in the framework of replica approach, we derive
rigorously the Wess-Zumino terms with the topological charges being their
levels in the two complex symmetry classes of A and AIII. Intriguingly, two
nontrivial examples of quadratic Fermi points with the topological charge `2'
are respectively illustrated for the classes A and AIII. We also address a
qualitative connection of topological charges of Fermi points in the real
symmetry classes to the topological terms in the non-linear sigma models, based
on the one-to-one classification correspondence.Comment: 8 pages and 2 figures, revised version with appendi
Topological Classification and Stability of Fermi Surfaces
In the framework of the Cartan classification of Hamiltonians, a kind of
topological classification of Fermi surfaces is established in terms of
topological charges. The topological charge of a Fermi surface depends on its
codimension and the class to which its Hamiltonian belongs. It is revealed that
six types of topological charges exist, and they form two groups with respect
to the chiral symmetry, with each group consisting of one original charge and
two descendants. It is these nontrivial topological charges which lead to the
robust topological protection of the corresponding Fermi surfaces against
perturbations that preserve discrete symmetries.Comment: 5 pages, published version in PR
Revealing a topological connection between stabilities of Fermi surfaces and topological insulators/superconductors
A topology-intrinsic connection between the stabilities of Fermi surfaces
(FSs) and topological insulators/superconductors (TIs/TSCs) is revealed. In
particular, a one-to-one relation between the topological types of FSs and
TIs/TSCs is rigorously derived; combining it with a well-established
topological theory of FSs, we produce a complete table illustrating precisely
topological types of all TIs/TSCs, while a valid part of it was postulated
before. Moreover, we propose and prove a general index theorem that relates the
topological charge of FSs on the natural boundary of a strong TI/TSC to its
bulk topological number. Implications of the general index theorem on the
boundary quasi-particles are also addressed.Comment: 5 pages with Supplemental Material, more content is adde
Effect of carrot puree edible films on quality preservation of fresh-cut carrots
peer-reviewedFinancial support from the high level talent fund of Henan University of Technology Science and Technology (No. 2012BS024) is gratefully acknowledged.The effect of edible films based on carrot puree, chitosan, corn starch, gelatin, glycerol and cinnamaldehyde on fresh-cut carrots was studied during storage. Several parameters, such as firmness, colour, weight loss, total carotenoids, total phenols, polyphenol oxidase (PPO) activity and peroxidase (POD) activity in coated carrots were determined at regular intervals and then compared with the uncoated carrots throughout the storage period. Significant and expected changes were observed in all carrot samples that were compared. The coating treatment significantly (P < 0.05) delayed the senescence, reduced the deterioration of exterior quality and retained total carotenoids well compared with control (P < 0.05). In addition, significant inhibition of PPO activity (P < 0.05) and POD activity (P < 0.05) as well as reduced accumulation of polyphenols (P < 0.05) were observed for all coated samples. All of these favourable responses induced by coating treatment on minimally processed fresh-cut carrots showed beneficial physiological effects, which would give some useful references to the fresh-cut fruit and vegetable processing industry and satisfy people’s requirements allowing for extending product shelf life without negatively affecting the sensory quality or acceptability.Henan University of Technology Science and Technolog
PMH34: COMPARISON OF OLANZAPINE VERSUS QUETIAPINE IN THE TREATMENT OF HOSPITALIZED PATIENTS WITH SCHIZOPHRENIA
This report highlights ILCA's work in the past, and discusses current activities and future plans with particular reference to mixed crop-livestock systems, market-oriented smallholder dairying, conservation of biodiversity, biological efficiency of livestock, livestock production under trypanosomiasis risk, livestock and resource management policy, and strengthening national research capacities
Unified theory of PT and CP invariant topological metals and nodal superconductors
As PT and CP symmetries are fundamental in physics, we establish a unified
topological theory of PT and CP invariant metals and nodal superconductors,
based on the mathematically rigorous theory. Representative models are
constructed for all nontrivial topological cases in dimensions , and
, with their exotic physical meanings being elucidated in detail.
Intriguingly, it is found that the topological charges of Fermi surfaces in the
bulk determine an exotic direction-dependent distribution of topological subgap
modes on the boundaries. Furthermore, by constructing an exact bulk-boundary
correspondence, we show that the topological Fermi points of the PT and CP
invariant classes can appear as gapless modes on the boundary of topological
insulators with a certain type of anisotropic crystalline symmetry.Comment: 4 pages, 1 figure and supplemental material, to be published in PR
Topological Weyl and Node-Line Semimetals in Ferromagnetic Vanadium-Phosphorous-Oxide -VOPO Compound
We propose that the topological semimetal features can co-exist with
ferromagnetic ground state in vanadium-phosphorous-oxide -VOPO
compound from first-principles calculations. In this magnetic system with
inversion symmetry, the direction of magnetization is able to manipulate the
symmetric protected band structures from a node-line type to a Weyl one in the
presence of spin-orbital-coupling. The node-line semimetal phase is protected
by the mirror symmetry with the reflection-invariant plane perpendicular to
magnetic order. Within mirror symmetry breaking due to the magnetization along
other directions, the gapless node-line loop will degenerate to only one pair
of Weyl points protected by the rotational symmetry along the magnetic axis,
which are largely separated in momentum space. Such Weyl semimetal phase
provides a nice candidate with the minimum number of Weyl points in a condensed
matter system. The results of surface band calculations confirm the non-trivial
topology of this proposed compound. This findings provide a realistic candidate
for the investigation of topological semimetals with time-reversal symmetry
breaking, particularly towards the realization of quantum anomalous Hall effect
in Weyl semimetals.Comment: 5 pages, 4 figure
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