Search

Your search keyword '"Bai XUE"' showing total 12,675 results
Start Over Author "Bai XUE"
12,675 results on '"Bai XUE"'

262. Towards First-principle Characterization of Cosmic-ray Transport Coefficients from Multi-scale Kinetic Simulations

Author

Bai, Xue-Ning

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract

A major uncertainty in understanding the transport and feedback of cosmic-rays (CRs) within and beyond our Galaxy lies in the unknown CR scattering rates, which are primarily determined by wave-particle interaction at microscopic gyro-resonant scales. The source of the waves for the bulk CR population is believed to be self-driven by the CR streaming instability (CRSI), resulting from the streaming of CRs downward a CR pressure gradient. While a balance between driving by the CRSI and wave damping is expected to determine wave amplitudes and hence the CR scattering rates, the problem involves significant scale separation with substantial ambiguities based on quasi-linear theory (QLT). Here we propose a novel "streaming box" framework to study the CRSI with an imposed CR pressure gradient, enabling first-principle measurement of the CR scattering rates as a function of environmental parameters. By employing the magnetohydrodynamic-particle-in-cell (MHD-PIC) method with ion-neutral damping, we conduct a series of simulations with different resolutions and CR pressure gradients and precisely measure the resulting CR scattering rates in steady state. The measured rates show scalings consistent with QLT, but with a normalization smaller by a factor of several than typical estimates based on single-fluid treatment of CRs. A momentum-by-momentum treatment provides better estimates when integrated over momentum, but is also subject substantial deviations especially at small momentum. Our framework thus opens up the path towards providing comprehensive subgrid physics for macroscopic studies of CR transport and feedback in broad astrophysical contexts., Comment: 26 pages, 8 figures, accepted for publication in ApJ

Published
2021
Full Text
View/download PDF

283. Adipose tissue deficiency and chronic inflammation in diabetic Goto-Kakizaki rats.

Author

Bai Xue, Siddharth Sukumaran, Jing Nie, William J Jusko, Debra C Dubois, and Richard R Almon

Subjects
Medicine, Science
Abstract

Type 2 diabetes (T2DM) is a heterogeneous group of diseases that is progressive and involves multiple tissues. Goto-Kakizaki (GK) rats are a polygenic model with elevated blood glucose, peripheral insulin resistance, a non-obese phenotype, and exhibit many degenerative changes observed in human T2DM. As part of a systems analysis of disease progression in this animal model, this study characterized the contribution of adipose tissue to pathophysiology of the disease. We sacrificed subgroups of GK rats and appropriate controls at 4, 8, 12, 16 and 20 weeks of age and carried out a gene array analysis of white adipose tissue. We expanded our physiological analysis of the animals that accompanied our initial gene array study on the livers from these animals. The expanded analysis included adipose tissue weights, HbA1c, additional hormonal profiles, lipid profiles, differential blood cell counts, and food consumption. HbA1c progressively increased in the GK animals. Altered corticosterone, leptin, and adiponectin profiles were also documented in GK animals. Gene array analysis identified 412 genes that were differentially expressed in adipose tissue of GKs relative to controls. The GK animals exhibited an age-specific failure to accumulate body fat despite their relatively higher calorie consumption which was well supported by the altered expression of genes involved in adipogenesis and lipogenesis in the white adipose tissue of these animals, including Fasn, Acly, Kklf9, and Stat3. Systemic inflammation was reflected by chronically elevated white blood cell counts. Furthermore, chronic inflammation in adipose tissue was evident from the differential expression of genes involved in inflammatory responses and activation of natural immunity, including two interferon regulated genes, Ifit and Iipg, as well as MHC class II genes. This study demonstrates an age specific failure to accumulate adipose tissue in the GK rat and the presence of chronic inflammation in adipose tissue from these animals.

Published
2011
Full Text
View/download PDF

284. Paleomagnetic evidence for a disk substructure in the early solar system

Author

Borlina, Cauê S., Weiss, Benjamin P., Bryson, James F. J., Bai, Xue-Ning, Lima, Eduardo A., Chatterjee, Nilanjan, and Mansbach, Elias N.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Physics - Geophysics
Abstract

Astronomical observations and isotopic measurements of meteorites suggest that substructures are common in protoplanetary disks and may even have existed in the solar nebula. Here, we conduct paleomagnetic measurements of chondrules in CO carbonaceous chondrites to investigate the existence and nature of these disk sub-structures. We show that the paleomagnetism of chondrules in CO carbonaceous chondrites indicates the presence of a 101 $\pm$ 48 $\mu$T field in the solar nebula in the outer solar system ($\sim$3 to 7 AU from the Sun). The high intensity of this field relative to that inferred from inner solar system ($\lesssim$3 AU) meteorites indicates a factor of $\sim$5 to 150 mismatch in nebular accretion between the two reservoirs. This suggests substantial mass loss from the disk associated with a major disk substructure, possibly due to a magnetized disk wind., Comment: 16 pages, 3 figures, published in Science Advances

Published
2021
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results