Search

Your search keyword '"Zhou, Ya‐Nan"' showing total 354 results
Start Over Author "Zhou, Ya‐Nan"
354 results on '"Zhou, Ya‐Nan"'

30. New Generalizations of Cosmography Inspired by the Pade Approximant

Author

Zhou, Ya-Nan, Liu, De-Zi, Zou, Xiao-Bo, and Wei, Hao

Subjects
General Relativity and Quantum Cosmology, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Theory
Abstract

The current accelerated expansion of the universe has been one of the most important fields in physics and astronomy since 1998. Many cosmological models have been proposed in the literature to explain this mysterious phenomenon. Since the nature and cause of the cosmic acceleration are still unknown, model-independent approaches to study the evolution of the universe are welcome. One of the powerful model-independent approaches is the so-called cosmography. It only relies on the cosmological principle, without postulating any underlying theoretical model. However, there are several shortcomings in the usual cosmography. For instance, it is plagued with the problem of divergence (or an unacceptably large error), and it fails to predict the future evolution of the universe. In the present work, we try to overcome or at least alleviate these problems, and we propose two new generalizations of cosmography inspired by the Pad\'e approximant. One is to directly parameterize the luminosity distance based on the Pad\'e approximant, while the other is to generalize cosmography with respect to a so-called $y_\beta$-shift $y_\beta=z/(1+\beta z)$, which is also inspired by the Pad\'e approximant. Then, we confront them with the observational data with the help of the Markov chain Monte Carlo (MCMC) code emcee, and find that they work fairly well., Comment: 16 pages, 3 tables, 5 figures, revtex4; v2: discussions added, Eur. Phys. J. C in press; v3: published version

Published
2016
Full Text
View/download PDF

31. Hojman Symmetry in $f(T)$ Theory

Author

Wei, Hao, Zhou, Ya-Nan, Li, Hong-Yu, and Zou, Xiao-Bo

Subjects
General Relativity and Quantum Cosmology, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Theory
Abstract

Today, $f(T)$ theory has been one of the popular modified gravity theories to explain the accelerated expansion of the universe without invoking dark energy. In this work, we consider the so-called Hojman symmetry in $f(T)$ theory. Unlike Noether conservation theorem, the symmetry vectors and the corresponding conserved quantities in Hojman conservation theorem can be obtained by using directly the equations of motion, rather than Lagrangian or Hamiltonian. We find that Hojman symmetry can exist in $f(T)$ theory, and the corresponding exact cosmological solutions are obtained. We find that the functional form of $f(T)$ is restricted to be the power-law or hypergeometric type, while the universe experiences a power-law or hyperbolic expansion. These results are different from the ones obtained by using Noether symmetry in $f(T)$ theory. Therefore, it is reasonable to find exact cosmological solutions via Hojman symmetry., Comment: 10 pages, revtex4; v2: discussions added, Astrophys. Space Sci. in press; v3: published version

Published
2015
Full Text
View/download PDF

37. Branched‐Chain Amino Acids Deficiency Promotes Diabetic Neuropathic Pain Through Upregulating LAT1 and Inhibiting Kv1.2 Channel.

Author

Zhou, Ze‐Yu, Wang, Ji‐Ying, Li, Zhi‐Xiao, Zheng, Hong‐Li, Zhou, Ya‐Nan, Huang, Li‐Na, Wang, Li‐Juan, Ding, Xiao‐Wei, Sun, Xin, Cai, Ke, Zhao, Rui, Shi, Yan, Chen, Alex F., Pan, Zhi‐Qiang, Cao, Jing, Lin, Fu‐Qing, and Zhao, Jian‐Yuan

Subjects
DORSAL root ganglia, DIABETES complications, AMINO acids, NEURALGIA, GENE expression
Abstract

Diabetic neuropathic pain (DNP), one of the most common complications of diabetes, is characterized by bilateral symmetrical distal limb pain and substantial morbidity. To compare the differences is aimed at serum metabolite levels between 81 DNP and 73 T2DM patients without neuropathy and found that the levels of branched‐chain amino acids (BCAA) are significantly lower in DNP patients than in T2DM patients. In high‐fat diet/low‐dose streptozotocin (HFD/STZ)‐induced T2DM and leptin receptor‐deficient diabetic (db/db) mouse models, it is verified that BCAA deficiency aggravated, whereas BCAA supplementation alleviated DNP symptoms. Mechanistically, using a combination of RNA sequencing of mouse dorsal root ganglion (DRG) tissues and label‐free quantitative proteomic analysis of cultured cells, it is found that BCAA deficiency activated the expression of L‐type amino acid transporter 1 (LAT1) through ATF4, which is reversed by BCAA supplementation. Abnormally upregulated LAT1 reduced Kv1.2 localization to the cell membrane, and inhibited Kv1.2 channels, thereby increasing neuronal excitability and causing neuropathy. Furthermore, intraperitoneal injection of the LAT1 inhibitor, BCH, alleviated DNP symptoms in mice, confirming that BCAA‐deficiency‐induced LAT1 activation contributes to the onset of DNP. These findings provide fresh insights into the metabolic differences between DNP and T2DM, and the development of approaches for the management of DNP. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

43. Cosmological Applications of Pade Approximant

Author

Wei, Hao, Yan, Xiao-Peng, and Zhou, Ya-Nan

Subjects
Astrophysics - Cosmology and Extragalactic Astrophysics, General Relativity and Quantum Cosmology, High Energy Physics - Theory
Abstract

As is well known, in mathematics, any function could be approximated by the Pad\'e approximant. The Pad\'e approximant is the best approximation of a function by a rational function of given order. In fact, the Pad\'e approximant often gives better approximation of the function than truncating its Taylor series, and it may still work where the Taylor series does not converge. In the present work, we consider the Pad\'e approximant in two issues. First, we obtain the analytical approximation of the luminosity distance for the flat XCDM model, and find that the relative error is fairly small. Second, we propose several parameterizations for the equation-of-state parameter (EoS) of dark energy based on the Pad\'e approximant. They are well motivated from the mathematical and physical points of view. We confront these EoS parameterizations with the latest observational data, and find that they can work well. In these practices, we show that the Pad\'e approximant could be an useful tool in cosmology, and it deserves further investigation., Comment: 19 pages, 8 figures, 1 table, revtex4; v2: discussions added, accepted for publication in JCAP; v3: published version

Published
2013
Full Text
View/download PDF

44. Cosmological Evolution of Einstein-Aether Models with Power-law-like Potential

Author

Wei, Hao, Yan, Xiao-Peng, and Zhou, Ya-Nan

Subjects
General Relativity and Quantum Cosmology, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Theory
Abstract

The so-called Einstein-Aether theory is General Relativity coupled (at second derivative order) to a dynamical unit time-like vector field (the aether). It is a Lorentz-violating theory, and gained much attention in the recent years. In the present work, we study the cosmological evolution of Einstein-Aether models with power-law-like potential, by using the method of dynamical system. In the case without matter, there are two attractors which correspond to an inflationary universe in the early epoch, or a de Sitter universe in the late time. In the case with matter but there is no interaction between dark energy and matter, there are only two de Sitter attractors, and no scaling attractor exists. So, it is difficult to alleviate the cosmological coincidence problem. Therefore, we then allow the interaction between dark energy and matter. In this case, several scaling attractors can exist under some complicated conditions, and hence the cosmological coincidence problem could be alleviated., Comment: 15 pages, 6 tables, revtex4; v2: discussions added, Gen. Rel. Grav. in press; v3: published version

Published
2013
Full Text
View/download PDF

47. Facile Synthesis of Ni(OH) 2 through Low-Temperature N-Doping for Efficient Hydrogen Evolution.

Author

Liu, Zi-Zhang, Fan, Ruo-Yao, Yu, Ning, Zhou, Ya-Nan, Zhang, Xin-Yu, Dong, Bin, and Yan, Zi-Feng

Subjects
METALS at low temperatures, CHARGE exchange, MASS transfer, SURFACE area, NICKEL
Abstract

Nickel hydroxide is a potentially cheap non-precious metal catalytic material for alkaline hydrogen evolution reactions (HERs). Herein, a nickel form (NF)-based nitrogen-modified nickel hydroxide (N-Ni(OH)2/NF) with interlaced two-dimensional (2D) nanosheet structures was synthesized by a simple one-step ammonia vapor-phase hydrothermal method for efficient electrocatalytic HERs. The effect of the reaction temperature of the catalyst preparation on the HERs' performance was studied in detail. The HER activity of N-Ni(OH)2/NF is enhanced by the large specific surface area, mass transfer and electron conductivity provided by a unique and suitable 2D nanostructure and nitrogen doping. The obtained N-Ni(OH)2/NF not only shows a superior HERs performance, but also exhibits good stability during long-term electrolysis. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results