1,155 research outputs found
Link between \emph{Zitterbewegung} and topological phase transition
Topological quantum state described by the global invariant has been
extensively studied in theory and experiment. In this letter, we investigate
the relationship between \emph{Zitterbewegung} and the topology of systems that
reflect the properties of the local and whole energy bands, respectively. We
generalize the usual two-band effective Hamiltonian to characterize the
topological phase transition of the spin- topological insulator. By studying
\emph{Zitterbewegung} dynamics before and after topological phase transition,
we find that the direction of quasiparticles' oscillation can well reflect
topological properties. Furthermore, we develop a quantitative calculation
formula for the topological invariant in the spin- Chern insulator and give
the selection rule of the corresponding dynamics. Finally, we demonstrate that
our theory is valid in different topological systems. The topological invariant
can be represented by local dynamical properties of the high-symmetry points in
the first Brillouin zone, which provides a new measurement method from the
dynamical perspective.Comment: 6 pages, 1 figure. Comments are welcom
Joint implications of BBN, CMB, and PTA Datasets for Scalar-Induced Gravitational Waves of Second and Third orders
Assuming the evidence for gravitational wave background from recent data
release of pulsar timing arrays to be interpreted as the scalar-induced
gravitational waves (SIGWs), we study the second and third order gravitational
waves simultaneously, by jointly analyzing a combination of PTA, big-bang
nucleosynthesis (BBN), and cosmic microwave background (CMB) datasets. We
obtain the primordial curvature spectral amplitude and
the spectral peak frequency $10^{-7.4}\ \mathrm{Hz}<f_\ast<10^{-6.4}\
\mathrm{Hz}10^{-4.3}M_\odot<m_{\mathrm{pbh}}<10^{-2.3}M_\odotA_\zeta\gtrsim0.06$. In addition, we anticipate that
future PTA projects can not only test the above results, but also have powerful
abilities to explore the origin and evolution of the universe, particularly,
the inflation.Comment: 12 pages, 2 figure
Evaluation of Cardioprotective Effects of Genistein against Diabetes-induced Cardiac Dysfunction in Rats
Purpose: To investigate the possible cardioprotective effects and potential pharmacological mechanism of genistein.Methods: Six-week old ZDF and lean rats were randomized into 4 groups (8 rats/group), including group 1 (control lean rats); group 2 (lean rats treated with genistein, 2.5 mg/kg); group 3 (control ZDF rats); and group 4 (ZDF treated with genistein). Two groups (2 and 4) were treated with genistein for 12 weeks, and cardiac functions and metabolic alterations were determined. Macrophage/monocyte chemo-attractant protein-1 (MCP-1), vascular cellular adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 (ICAM-1) secretion and their messenger RNA transcription level also were observed.Results: Genistein attenuated diabetes-induced cardiac dysfunction and pathological alterations, by improving glucose tolerance and insulin resistance; facilitating Akt activation and glucose utilization, and attenuating oxidative stress and interrelated MAP kinase and NF-κB signalling pathways. In addition, genistein treatment markedly reduced diabetic-induced MCP-1 (83.33 %), VCAM-1 (74.66 %) and ICAM-1 (71.42 %) secretion and mRNA transcription in ZDF rats.Conclusion: The results demonstrate the putative effects of genistein against cardiovascular dysfunction by improving glucose homeostasis, attenuating oxidative stress and reduced diabeticinduced endothelial dysfunction in ZDF rats. Thus, genistein is a potential candidate for the prevention of cardiovascular diseases.Keywords: Cardiac dysfunction, Genistein, Oxidative stress, Inflammatory response, Insulin resistance, Glucose toleranc
A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz
A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz is carried out
using the Shanghai Tian Ma 65 m Radio Telescope (TMRT-65m) with a sensitivity
of < 7 mK. Thirty-five spectral lines of 12 different molecules and radicals
are detected in total. Except for SiS, the detected molecules are all
carbon-chain molecules, including HC3N, HC5N, HC7N, HC9N, C6H, C6H-, C8H, SiC2,
SiC4, c-C3H2 and l-C5H. The presence of rich carbon-bearing molecules is
consistent with the identity of IRC +10216 as a carbon-rich AGB star. The
excitation temperatures and column densities of the observed species are
derived by assuming a local thermodynamic equilibrium and homogeneous
conditions.Comment: This is the authors' version of the manuscript; 16 pages, 5 figures,
6 tables; Accepted for publication in A&A 8/17/201
The Third Order Scalar Induced Gravitational Waves
Since the gravitational waves were detected by LIGO and Virgo, it has been
promising that lots of information about the primordial Universe could be
learned by further observations on stochastic gravitational waves background.
The studies on gravitational waves induced by primordial curvature
perturbations are of great interest. The aim of this paper is to investigate
the third order induced gravitational waves. Based on the theory of
cosmological perturbations, the first order scalar induces the second order
scalar, vector and tensor perturbations. At the next iteration, the first order
scalar, the second order scalar, vector and tensor perturbations all induce the
third order tensor perturbations. We present the energy density spectrum of the
third order gravitational waves for a monochromatic primordial power spectrum.
The shape of the energy density spectrum of the third order gravitational waves
is different from that of the second order scalar induced gravitational waves.
And it is found that the third order gravitational waves sourced by the second
order scalar perturbations dominate the energy density spectrum.Comment: 33 pages, 4 figure
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