21 results on '"Liu, Kaijun"'
Search Results
2. sj-docx-3-tag-10.1177_17562848231170945 – Supplemental material for Development and validation of a deep learning-based approach to predict the Mayo endoscopic score of ulcerative colitis
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Qi, Jing, Ruan, Guangcong, Ping, Yi, Xiao, Zhifeng, Liu, Kaijun, Cheng, Yi, Liu, Rongbei, Zhang, Bingqiang, Zhi, Min, Chen, Junrong, Xiao, Fang, Zhao, Tingting, Li, Jiaxing, Zhang, Zhou, Zou, Yuxin, Cao, Qian, Nian, Yongjian, and Wei, Yanling
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FOS: Clinical medicine ,111199 Nutrition and Dietetics not elsewhere classified ,FOS: Health sciences ,111599 Pharmacology and Pharmaceutical Sciences not elsewhere classified ,111299 Oncology and Carcinogenesis not elsewhere classified - Abstract
Supplemental material, sj-docx-3-tag-10.1177_17562848231170945 for Development and validation of a deep learning-based approach to predict the Mayo endoscopic score of ulcerative colitis by Jing Qi, Guangcong Ruan, Yi Ping, Zhifeng Xiao, Kaijun Liu, Yi Cheng, Rongbei Liu, Bingqiang Zhang, Min Zhi, Junrong Chen, Fang Xiao, Tingting Zhao, Jiaxing Li, Zhou Zhang, Yuxin Zou, Qian Cao, Yongjian Nian and Yanling Wei in Therapeutic Advances in Gastroenterology
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- 2023
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3. Nano-Micron Exsolved Spinels in Titanomagnetite and Their Implications for the Formation of the Panzhihua Fe–Ti–V Oxide Deposit, Southwest China
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Liu Kaijun, Zhao Fude, Li Yongli, Fei Huang, and Zhibin Zhang
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Materials science ,Fractional crystallization (geology) ,010504 meteorology & atmospheric sciences ,Spinel ,Biomedical Engineering ,Oxide ,Geochemistry ,Bioengineering ,General Chemistry ,Electron microprobe ,engineering.material ,010502 geochemistry & geophysics ,Condensed Matter Physics ,01 natural sciences ,Grain size ,Petrography ,chemistry.chemical_compound ,chemistry ,Mineral redox buffer ,engineering ,General Materials Science ,Mafic ,0105 earth and related environmental sciences - Abstract
The nano-micron exsolved spinels with various mineralogical characteristics in titanomagnetite from Fe–Ti oxide gabbros in the Panzhihua Fe–Ti–V oxide deposit, SW China, have been studied by field emission scanning electron microscopy (FE-SEM) and electron probe microanalysis (EPMA) based on comparisons of physical and chemical conditions at different stratigraphic heights to investigate the compositional inheritance between titanomagnetite and exsolved spinel and further explore the relationship between the morphology and growth of exsolved spinels. Restored chemical data for titanomagnetite combined with evidence from petrography and whole-rock geochemistry imply fractional crystallization of the Panzhihua Fe–Ti–V oxide deposit, where the titanomagnetite of thick massive oxides at the bottom of the No. VIII orebody represents the early crystallizing phase characterized by high temperature and oxygen fugacity. The chemical variation in the exsolved spinel, which has the same trend as the restored composition of titanomagnetite, represents inheritance from the parent rock within the Panzhihua deposit. Exsolved spinel continuously adjusts morphology and grain size to decrease the total energy of the manganate-spinel system from fine-grained spinels parallel to the {100} plane of titanomagnetite to spinels with complex stellate morphology to bulky granular spinels with high degrees of idiomorphism. The unusual multiple magma replenishment during the mineralizing process and at different stratigraphic heights in the Panzhihua intrusion had an important influence on the thermal evolution history of the orebody, resulting in the identifiable spatial distribution patterns of spinel morphology and grain size. Using spinel exsolution as a discriminator for the provenance of magmatic ore deposits may provide intuitive and easy mineralogical evidence to qualitatively discuss the evolution of the metallogenetic environment and the ore-forming conditions for similar large mafic intrusions.
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- 2021
4. 基于色散拐点微纳光纤耦合器的通孔悬臂梁振动传感器
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范俊豪 Fan Junhao, 杨祥文 Yang Xiangwen, 罗彬彬 Luo Binbin, 邹雪 Zou Xue, 刘开俊 Liu Kaijun, 吴德操 Wu Decao, 郭裕丰 Guo Yufeng, 石胜辉 Shi Shenghui, and 赵明富 Zhao Mingfu
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Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials - Published
- 2022
5. Morphology Evolution of Nano-Micron Pyrite: A Review
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Yinghui Wang, Xing Miaomiao, Liu Kaijun, Wenyuan Gao, Ren Yaqun, Fei Huang, Lin Meng, Zhang Zhibin, Yan Yingcan, Li Yongli, and Shang Gao
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Morphology (linguistics) ,Materials science ,Biomedical Engineering ,Bioengineering ,Nanotechnology ,General Chemistry ,010501 environmental sciences ,engineering.material ,010502 geochemistry & geophysics ,Condensed Matter Physics ,01 natural sciences ,Nano ,engineering ,General Materials Science ,Pyrite ,0105 earth and related environmental sciences - Published
- 2017
6. Two-Dimensional gcPIC Simulation of Rising-Tone Chorus Waves in a Dipole Magneitic Field
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Lu, Quanming, Ke, Yangguang, Wang, Xueyi, Liu, Kaijun, Gao, Xinliang, Chen, Lunjin, and Wang, Shui
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Rising-tone chorus waves have already been successfully produced in a mirror magnetic field with the use of one- and two-dimensional particle-in-cell (PIC) simulations. However, in reality, the background magnetic field in the inner Earth's magnetosphere is a dipole magnetic field, unlike symmetric mirror fields. In this paper, with the two-dimensional (2-D) general curvilinear PIC (gcPIC) code, we investigate the generation of rising-tone chorus waves in the dipole magnetic field configuration. The plasma consists of three components: immobile ions, cold background, and hot electrons. In order to save computational resource, the topology of the magnetic field is roughly equal to that at L = 0.6 R-E, although the plasma parameters corresponding to those at L = 6 R-E (R-E is the Earth's radius) are used. Whistler mode waves are first excited around the magnetic equator by the hot electrons with a temperature anisotropy. The excited whistler mode waves propagate almost parallel and antiparallel to the background magnetic field in their source region, which is limited at vertical bar lambda vertical bar
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- 2019
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7. 基于薄包层极大倾角光纤光栅的灵敏度增强型振动传感器
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刘开俊 LIU Kaijun, 罗彬彬 LUO Binbin, 邹雪 ZOU Xue, 吴德操 WU Decao, 石胜辉 SHI Shenghui, 蒋上海 JIANG Shanghai, 邓欧 DENG Ou, 邹祥龙 ZOU Xianglong, 巫涛江 WU Taojiang, and 赵明富 ZHAO Mingfu
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Atomic and Molecular Physics, and Optics - Published
- 2021
8. Micro-texture and in situ sulfur isotope of pyrite from the Baiyunpu Pb–Zn deposit in central Hunan, South China: Implications for the growth mechanism of colloform pyrite aggregates
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Liu Kaijun, Li Yongli, Fei Huang, Shang Gao, Lin Meng, Lei Chen, Xinyi Qi, Chenwei Chai, and Limin Su
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Acicular ,010504 meteorology & atmospheric sciences ,Inner core ,chemistry.chemical_element ,Mineralogy ,Geology ,Crystal growth ,engineering.material ,010502 geochemistry & geophysics ,01 natural sciences ,Sulfur ,Crystal ,δ34S ,chemistry ,engineering ,Pyrite ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Electron backscatter diffraction - Abstract
Colloform pyrite textures have been detected in various geological bodies and have received much attention in recent years. Although these textures have been proved to be formed by the aggregation of micro-grains with different sizes, further work is needed to understand the mechanism for developing them. We carried out a detailed study on the micro-textures, crystal preferred orientations (CPOs), trace element, and sulfur isotope compositions of colloform pyrite aggregates from the Baiyunpu Pb–Zn deposit in Hunan, China. Results showed that the inner core of colloform pyrite had an irregular outline with flattening at their contact boundaries and was commonly formed by the compaction of multiple spherical aggregates. The outer layers concentrically grew around the core. Field emission-scanning electron microscope (FE-SEM) suggested both the inner core and the outer layers were composed of a large number of nano- or micron-scale grains (~300 nm granular crystals to acicular and elongated crystals up to ~100 μm in length). Electron backscatter diffraction (EBSD) revealed an initial random CPO in the core and either 〈1 0 0〉 or 〈1 1 0〉 CPOs in subsequent layers. In situ sulfur isotope compositions obtained by secondary-ion mass spectrometry (SIMS) showed that the δ34S values of colloform pyrite ranged from −8.4 to −0.2‰, which were interpreted to be mainly derived from thermochemical sulfate reduction (TSR). Colloform pyrite aggregates are considered to grow from the core outward through the accretion of layers, including (1) formation and aggregation of microcrystals in core A1 and (2) growth and geometrical selection of crystals in outer layers. The growth and transformation of pyrite from disorderly granular microcrystals in the core to elongated crystals radiating from the aggregated center in the outer concentric zones is thought to be controlled by geometrical selection. Factors affecting the epitaxial relationship between the substrate and the growing crystals, such as interface energy, ambient temperature and degree of sulfur supersaturation, may control the abrupt changes in CPO recorded in colloform pyrite aggregates.
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- 2020
9. Particle-in-Cell Simulations of the Fast Magnetosonic Mode in a Dipole Magnetic Field: 1-D Along the Radial Direction
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Min, Kyungguk, Liu, Kaijun, Denton, Richard, and Boardsen, Scott
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An electromagnetic particle-in-cell code is used to investigate self-consistent evolution of the fast magnetosonic mode in a one-dimensional configuration along the radial direction in a dipole background magnetic field. A previous observation of this wave mode is used to select the simulation parameters. A partial shell velocity distribution of energetic protons with a moderate pitch angle anisotropy is used to excite the waves self-consistently. Consistent with local linear theory analysis, wave growth occurs only at exact harmonics of the local proton cyclotron frequency, Omega(p). However, radial propagation quickly removes the waves from the region where they can grow, leading to a time scale of wave amplification much longer than that predicted by linear theory. In addition, radial propagation from multiple wave sources makes the frequency spectrum measured at a single point much broader. The warm background plasma plays an important role in two ways. First, it increases the phase speed of the fast magnetosonic mode; and second, it causes the breakup of the extraordinary mode dispersion relation in the vicinity of the harmonics, where the broken dispersion curves are connected with multiple ion Bernstein modes. In this case, the waves propagating radially are absorbed at locations where their frequency reaches integer multiples of Omega(p) and background protons experience perpendicular heating at those locations.
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- 2018
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10. Equatorial Evolution of the Fast Magnetosonic Mode in the Source Region: Observation-Simulation Comparison of the Preferential Propagation Direction
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Min, Kyungguk, Boardsen, Scott, Denton, Richard, and Liu, Kaijun
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Recent analysis of an event observed by the Van Allen Probes in the source region outside the plasmapause has shown that fast magnetosonic waves (also referred to as equatorial noise) propagate preferentially in the azimuthal direction, implying that wave amplification should occur during azimuthal propagation. To demonstrate this, we carry out 2-D particle-in-cell simulations of the fast magnetosonic mode at the dipole magnetic equator with the simulation box size, the magnetic field inhomogeneity, and the plasma parameters chosen from the same event recently analyzed. The self-consistently evolving electric and magnetic field fluctuations are characterized by spectral peaks at harmonics of the local proton cyclotron frequency. The azimuthal component of the electric field fluctuations is larger than the radial component, indicating wave propagation mainly along the azimuthal direction. Because the simulation box is within the source region, this also implies wave amplification mainly during azimuthal propagation. The excellent agreement between the wave polarization properties of the present simulations and the recently reported observations is clear evidence that the main wave amplification occurs during azimuthal propagation in the source region.
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- 2018
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11. P‐6.9: High‐reliability a‐Si:H TFT with Repressing Photo‐degradation on G8.6 LCDs
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Yang Fengyun, Wei Chao, Zhang Hejing, Liu Zhen, Cho An-Thung, Hsu James, Liu Kaijun, and Mo Qionghua
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Materials science ,Reliability (semiconductor) ,Thin-film transistor ,business.industry ,Optoelectronics ,Photodegradation ,business - Published
- 2019
12. Power stability optimization method of wireless power transfer system against wide misalignment
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Guang Yang, Kai Song, Guo Wei, Rengui Lu, Liu Kaijun, and Chunbo Zhu
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Engineering ,business.product_category ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Transmitter ,Electrical engineering ,Solenoid ,02 engineering and technology ,Electromagnetic coil ,Electric vehicle ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Physics::Accelerator Physics ,Wireless ,Wireless power transfer ,business ,Coupling coefficient of resonators - Abstract
Wireless power transfer (WPT) system has been introduced to many applications. However, it allows very limited misalignment of the power receiver relative to the power transmitter, which is not suitable for some applications such as electric vehicle (EV) wireless charging. This paper presents methods to improve output stability over large misalignment from the perspective of compensation topology and magnetic coupler. For compensation topology, multi-level non-resonant topology is proposed and analyzed. By adjusting the component of the topology, output power can be modified. For magnetic coupler, solenoid type coil is applied with a quadrature pick-up in order to stabilize coupling coefficient. Experiment results show that proposed design methods can stabilize transmission power against a wide range of misalignment.
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- 2017
13. Scalings for the Alfven-cyclotron instability: Linear dispersion theory and hybrid particle-in-cell simulations
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Gary, S. Peter, Fu, Xiangrong, Cowee, Misa M., Winske, Dan, and Liu, Kaijun
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The Alfven-cyclotron instability is driven by an ion temperature anisotropy such that T-perpendicular to/T-|| >1 where and || denote directions perpendicular and parallel to a uniform background magnetic field B-o, respectively. The computations presented here consider a model of a magnetized, homogeneous, collisionless plasma. Two representations of the proton velocity distribution are considered: a single bi-Maxwellian and a magnetospheric-like configuration of two components, a more dense, relatively cool, isotropic component and a less dense, relatively hot, bi-Maxwellian component which drives the instability. Only wave propagation parallel to B-o is considered. Using numerical solutions of the full kinetic linear dispersion equation, concise analytic expressions for the scaling of the dimensionless maximum instability growth rate and the corresponding dimensionless real frequency are derived as functions of three dimensionless variables: the hot proton temperature anisotropy, the relative hot proton density, and the hot proton (||). Furthermore, using one-dimensional hybrid particle-in-cell simulations of this same instability, a third relation for the scaling of the maximum amplitude of the dimensionless fluctuating magnetic field energy density is derived.
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- 2017
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14. Proton velocity ring-driven instabilities and their dependence on the ring speed: Linear theory
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Min, Kyungguk, Liu, Kaijun, and Gary, Peter
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Linear dispersion theory is used to study the Alfven-cyclotron, mirror and ion Bernstein instabilities driven by a tenuous (1%) warm proton ring velocity distribution with a ring speed, v(r), varying between 2v(A) and 10v(A), where v(A) is the Alfven speed. Relatively cool background protons and electrons are assumed. The modeled ring velocity distributions are unstable to both the Alfven-cyclotron and ion Bernstein instabilities whose maximum growth rates are roughly a linear function of the ring speed. The mirror mode, which has real frequency omega(r)=0, becomes the fastest growing mode for sufficiently large v(r)/v(A). The mirror and Bernstein instabilities have maximum growth at propagation oblique to the background magnetic field and become more field-aligned with an increasing ring speed. Considering its largest growth rate, the mirror mode, in addition to the Alfven-cyclotron mode, can cause pitch angle diffusion of the ring protons when the ring speed becomes sufficiently large. Moreover, because the parallel phase speed, v(vertical bar ph), becomes sufficiently small relative to v(r), the low-frequency Bernstein waves can also aid the pitch angle scattering of the ring protons for large v(r). Potential implications of including these two instabilities at oblique propagation on heliospheric pickup ion dynamics are discussed.
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- 2017
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15. Ring/Shell Ion Distributions at Geosynchronous Orbit
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Thomsen, M, Denton, M, Gary, S, Liu, Kaijun, and Min, Kyungguk
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One year's worth of plasma observations from geosynchronous orbit is examined for ion distributions that may simultaneously be subject to the ion Bernstein (IB) instability (generating fast magnetosonic waves) and the Alfven cyclotron (AC) instability (generating electromagnetic ion cyclotron waves). Confirming past analyses, distributions with robust partial derivative fp(v(perpendicular to))/partial derivative v(perpendicular to) > 0 near v(|)| = 0, which we denote as ring/shell distributions, are commonly found primarily on the dayside of the magnetosphere. A new approach to high-fidelity representation of the observed ring/shell distribution functions in a form readily suited to both analytical moment calculation and linear dispersion analysis is presented, which allows statistical analysis of the ring/shell properties. The ring/shell temperature anisotropy is found to have a clear upper limit that depends on the parallel beta of the ring/shell (beta|| r) in a manner that is diagnostic of the operation of the AC instability. This upper limit is only reached in the postnoon events, which are primarily produced by the energy-and pitch angle-dependent magnetic drifts of substorm-injected ions. Further, it is primarily the leading edge of such injections, where the distribution is strongly ring-like, that the AC instability appears to be operating. By contrast, the ratio of the ring energy to the Alfven energy remains well within the range of 0.25-4.0 suitable for IB instability throughout essentially all of the events, except those that occur in denser cold plasma of the outer plasmasphere. Plain Language Summary One year's worth of plasma observations from geosynchronous orbit is examined for ion distributions that may simultaneously be subject to the ion Bernstein (IB) instability (generating fast magnetosonic waves) and the Alfven cyclotron (AC) instability (generating electromagnetic ion cyclotron waves). Confirming past analyses, ring/shell distributions are commonly found primarily on the dayside of the magnetosphere. A new approach to high-fidelity representation of the observed ring/shell distribution functions allows statistical analysis of the ring/shell properties. Clear evidence is found for the operation of the AC instability, but only in the afternoon events, which are primarily produced by the energy-and pitch angle-dependent magnetic drifts of substorm-injected ions. Further, it is primarily at the leading edge of such injections, where the distribution is strongly ring-like, that the AC instability appears to be operating. By contrast, the IB instability seems to be driven throughout essentially all of the events, except those that occur in denser cold plasma of the outer plasmasphere. These results suggest that fast magnetosonic waves should typically dominate over electromagnetic ion cyclotron waves during most substorm injections.
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- 2017
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16. MicroRNA-520c inhibits glioma cell migration and invasion by the suppression of transforming growth factor-β receptor type 2
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Chaojia Wang, Jie Luo, Hu Shengli, Yuqiang Zhang, Huibin Chen, Liu Kaijun, and Hui Wang
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0301 basic medicine ,Male ,Cancer Research ,Blotting, Western ,Biology ,Protein Serine-Threonine Kinases ,Real-Time Polymerase Chain Reaction ,Immunoenzyme Techniques ,03 medical and health sciences ,Cell Movement ,Glioma ,medicine ,Tumor Cells, Cultured ,Gene silencing ,Humans ,Neoplasm Invasiveness ,RNA, Messenger ,Cell Proliferation ,Cell growth ,Brain Neoplasms ,Reverse Transcriptase Polymerase Chain Reaction ,Receptor, Transforming Growth Factor-beta Type II ,Cell migration ,General Medicine ,Cell cycle ,Middle Aged ,medicine.disease ,Prognosis ,Cell biology ,Gene Expression Regulation, Neoplastic ,MicroRNAs ,030104 developmental biology ,Oncology ,Cancer cell ,Cancer research ,Female ,A431 cells ,Receptors, Transforming Growth Factor beta ,Transforming growth factor - Abstract
Dysregulation of microRNAs (miRNAs) is actively involved in the development and progression of glioma. miR-520c was previously found to inhibit glioblastoma cell migration. However, the clinical significance of miR-520c and its biological function in glioma remain largely unknown. In the present study, we found that miR-520c expression in glioma tissues was significantly decreased compared to adjacent non‑cancerous tissues. The low level of miR-520c was prominently correlated with advanced World Health Organization (WHO) grade and decreased overall survival of glioma patients. Overexpression of miR-520c in U251 cells significantly decreased the migration and invasion of the cancer cells, while miR-520c silencing promoted U87 cell migration and invasion in vitro. Mechanistically, miR-520c inversely regulated transforming growth factor-β receptor type 2 (TGFBRII) abundance in the glioma cells. Herein, TGFBRII was found to be a downstream target of miR-520c in glioma. Furthermore, an inverse correlation between TGFBRII and miR-520c expression was observed in the glioma cases. In constrast, restoration of TGFBRII expression abrogated the effects of miR-520c overexpression in U251 cells with increased cell migration and invasion. In addition, miR-520c overexpression blocked TGF-β1‑induced cell migration and invasion in U251 cells. Collectively, miR-520c may serve as a prognostic predictor and a therapeutic target for glioma patients.
- Published
- 2016
17. Scalings of Alfven-cyclotron and ion Bernstein instabilities on temperature anisotropy of a ring-like velocity distribution in the inner magnetosphere
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Gary, Peter, Min, Kyungguk, and Liu, Kaijun
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A ring-like proton velocity distribution with f(p)(v)/v>0 and which is sufficiently anisotropic can excite two distinct types of growing modes in the inner magnetosphere: ion Bernstein instabilities with multiple ion cyclotron harmonics and quasi-perpendicular propagation and an Alfven-cyclotron instability at frequencies below the proton cyclotron frequency and quasi-parallel propagation. Recent particle-in-cell simulations have demonstrated that even if the maximum linear growth rate of the latter instability is smaller than the corresponding growth of the former instability, the saturation levels of the fluctuating magnetic fields can be greater for the Alfven-cyclotron instability than for the ion Bernstein instabilities. In this study, linear dispersion theory and two-dimensional particle-in-cell simulations are used to examine scalings of the linear growth rate and saturation level of the two types of growing modes as functions of the temperature anisotropy T/T-parallel to for a general ring-like proton distribution with a fixed ring speed of 2v(A), where v(A) is the Alfven speed. For the proton distribution parameters chosen, the maximum linear theory growth rate of the Alfven-cyclotron waves is smaller than that of the fastest-growing Bernstein mode for the wide range of anisotropies (1T/T-parallel to
- Published
- 2016
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18. Proton velocity ring-driven instabilities in the inner magnetosphere: Linear theory and particle-in-cell simulations
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Min, Kyungguk and Liu, Kaijun
- Abstract
Linear dispersion theory and electromagnetic particle-in-cell (PIC) simulations are used to investigate linear growth and nonlinear saturation of the proton velocity ring-driven instabilities, namely, ion Bernstein instability and Alfven-cyclotron instability, which lead to fast magnetosonic waves and electromagnetic ion cyclotron waves in the inner magnetosphere, respectively. The proton velocity distribution is assumed to consist of 10% of a ring distribution and 90% of a low-temperature Maxwellian background. Here two cases with ring speeds v(r)/v(A)=1 and 2 (v(A) is the Alfven speed) are examined in detail. For the two cases, linear theory predicts that the maximum growth rate (m) of the Bernstein instability is 0.16(p) and 0.19(p), respectively, and (m) of the Alfven-cyclotron instability is 0.045(p) and 0.15(p), respectively, where (p) is the proton cyclotron frequency. Two-dimensional PIC simulations are carried out for the two cases to examine the instability development and the corresponding evolution of the particle distributions. Initially, Bernstein waves develop and saturate with strong electrostatic fluctuations. Subsequently, electromagnetic Alfven-cyclotron waves grow and saturate. Despite their smaller growth rate, the saturation levels of the Alfven-cyclotron waves for both cases are larger than those of the Bernstein waves. Resonant interactions with the Bernstein waves lead to scattering of ring protons predominantly along the perpendicular velocity component (toward both decreasing and, at a lesser extent, increasing speeds) without substantial change of either the parallel temperature or the temperature anisotropy. Consequently, the Alfven-cyclotron instability can still grow. Furthermore, the free energy resulting from the pitch angle scattering by the Alfven-cyclotron waves is larger than the free energy resulting from the perpendicular energy scattering, thereby leading to the larger saturation level of the Alfven-cyclotron waves.
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- 2016
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19. Ion Bernstein instability dependence on the proton-to-electron mass ratio: Linear dispersion theory
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Min, Kyungguk and Liu, Kaijun
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Fast magnetosonic waves, which have as their source ion Bernstein instabilities driven by tenuous ring-like proton velocity distributions, are frequently observed in the inner magnetosphere. One major difficulty in the simulation of these waves is that they are excited in a wide frequency range with discrete harmonic nature and require time-consuming computations. To overcome this difficulty, recent simulation studies assumed a reduced proton-to-electron mass ratio, m(p)/m(e), and a reduced light-to-Alfven speed ratio, c/v(A), to reduce the number of unstable modes and, therefore, computational costs. Although these studies argued that the physics of wave-particle interactions would essentially remain the same, detailed investigation of the effect of this reduced system on the excited waves has not been done. In this study, we investigate how the complex frequency, = (r)+i, of the ion Bernstein modes varies with m(p)/m(e) for a sufficiently large c/v(A) (such that pe2/e2(me/mp)(c/vA)2 >> 1) using linear dispersion theory assuming two different types of energetic proton velocity distributions, namely, ring and shell. The results show that low- and high-frequency harmonic modes respond differently to the change of m(p)/m(e). For the low harmonic modes (i.e., (r)approximate to(p)), both (r)/(p) and /(p) are roughly independent of m(p)/m(e), where (p) is the proton cyclotron frequency. For the high harmonic modes (i.e., p<
- Published
- 2016
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20. Pickup proton instabilities and scattering in the distant solar wind and the outer heliosheath: Hybrid simulations
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Liu, Kaijun, Eberhard, Möbius, Gary, S. Peter, and Winske, Dan
- Abstract
The growth of magnetic field fluctuations driven by the injection of pickup ions perpendicular to a background magnetic field in a homogeneous, collisionless plasma is studied using one-dimensional hybrid simulations. Freshly ionized protons are continuously injected into the simulations at constant rates and relative speeds consistent with conditions in the distant solar wind and the outer heliosheath. The pickup protons initially form a ring-velocity distribution unstable to the electromagnetic proton cyclotron instability and lead to enhanced magnetic fluctuations. After an exponential growth phase of the instability, the fluctuating magnetic fields exhibit linear temporal growth followed by a more-slowly growing quasi-steady phase. The excited fluctuations pitch angle scatter the pickup protons toward an isotropic shell velocity distribution with the most significant scattering occurring in the exponential growth phase. The scattering rate of the freshly injected pickup protons during the linear temporal growth phase remains relatively constant and it increases with the pickup proton injection rate. More importantly, significant pitch angle scattering only occurs after the accumulated pickup proton density exceeds a critical value, the scattering-onset density. The scattering-onset density also increases with the pickup proton injection rate and the scattering onset typically occurs during the exponential growth phase of the magnetic fluctuations. Scaling relations for the scattering rate and the scattering-onset density versus the pickup proton injection rate are derived from the simulation results. These relations suggest that significant scattering of pickup protons in the outer heliosheath occurs in a relatively limited spatial range close to the heliopause, related to the issue of whether the secondary ENA mechanism is a possible explanation for the ENA ribbon observed by IBEX. Implications of the results on pickup proton dynamics in the distant solar wind are also discussed.
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- 2012
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21. Evolution of Earth-size planetary atmospheres: from planets to exoplanets
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Liu, Kaijun, Jarvinen, Riku, Sillanpaa, Ilkka, Schmidt, Walter, Esa Kallio, and Janhunen, Pekka
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