| 3381. |
- Liu, Yueqiang, 1971, et al.
(author)
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Modelling of plasma response to RMP fields in MAST and ITER
- 2011
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In: Nuclear Fusion. - 1741-4326 .- 0029-5515. ; 51, s. 083002-
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Journal article (peer-reviewed)abstract
- The resonant magnetic perturbation (RMP) fields, including the plasma response, are computed within a linear, full toroidal, single-fluid resistive magnetohydrodynamic (MHD) model, and under realistic plasma conditions for MAST and ITER. The response field is found to be considerably reduced, compared with the vacuum field produced by the magnetic perturbation coils. This field reduction relies strongly on the screening effect from the toroidal plasma rotation. Computations also quantify three-dimensional (3D) distortions of the plasma surface, caused by RMP fields. A correlation is found between the computed mode structures, the plasma surface displacement and the observed density pump-out effect in MAST experiments. Generally, the density pump-out tends to occur when the surface displacement peaks near the X-points.
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| 3382. |
- Liu, Yueqiang, 1971, et al.
(author)
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Modelling resonant field amplification due to low-n peeling modes in JET
- 2010
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In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 52:4, s. 045011-
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Journal article (peer-reviewed)abstract
- The MHD code MARS-F is used to model low-n, low-frequency, large-amplitude resonant field amplification peaks observed in JET low-pressure plasmas. The resonant response of a marginally stable, n = 1 ideal peeling mode is offered as a candidate to explain the experimental observation. It is found that, unlike the response of a stable resistive wall mode, the peeling mode response is not sensitive to the plasma rotation, nor to the kinetic effects.
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| 3383. |
- Liu, Yueqiang, 1971, et al.
(author)
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Modification of ∆′ by magnetic feedback and kinetic effects
- 2012
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In: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 19, s. 092510-
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Journal article (peer-reviewed)abstract
- Two possible ways of modifying the linear tearing mode index, by active magnetic feed- back and by drift kinetic effects of deeply trapped particles, are analytically investigated. Mag- netic feedback schemes, studied in this work, are found generally stabilizing for ∆′ . The drift kinetic effects from both thermal particles and hot ions tend to reduce the power of the large solution from the outer region. This generally leads to a destabilization of ∆′ for the toroidal analytic equilibria considered here.
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| 3384. |
- Liu, Yueqiang, 1971, et al.
(author)
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Multimachine Data-Based Prediction of High-Frequency Sensor Signal Noise for Resistive Wall Mode Control in ITER
- 2016
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In: Fusion Science and Technology. - : Informa UK Limited. - 1536-1055 .- 1943-7641. ; 70:3, s. 387-405
-
Journal article (peer-reviewed)abstract
- The high-frequency noise measured by magnetic sensors, at levels above the typical frequency of resistive wall modes, is analyzed across a range of present tokamak devices including DIII-D, JET, MAST, ASDEX Upgrade, JT-60U, and NSTX. A high-pass filter enables identification of the noise component with Gaussian-like statistics that shares certain common characteristics in all devices considered. A conservative prediction is made for ITER plasma operation of the high-frequency noise component of the sensor signals, to be used for resistive wall mode feedback stabilization, based on the multimachine database. The predicted root-mean-square n = 1 (n is the toroidal mode number) noise level is 10(4) to 10(5) G/s for the voltage signal, and 0.1 to 1 G for the perturbed magnetic field signal. The lower cutoff frequency of the Gaussian pickup noise scales linearly with the sampling frequency, with a scaling coefficient of about 0.1. These basic noise characteristics should be useful for the modeling-based design of the feedback control system for the resistive wall mode in ITER.
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| 3385. |
- Liu, Yu Ping, et al.
(author)
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Lindqvist Polyoxoniobate Ion-Assisted Electrodeposition of Cobalt and Nickel Water Oxidation Catalysts
- 2015
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:30, s. 16632-16644
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Journal article (peer-reviewed)abstract
- A method has been developed for the efficient electrodeposition of cobalt and nickel nanostructures with the assistance of the Lindqvist ion [Nb6O19](8). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry, and a range of electrochemical techniques have been used to characterize the morphology, composition, catalytic water oxidation activity and stability of the films in alkaline solution. SEM images show that films consisting of nanoparticles with diameters of ca. 30 to 40 nm are formed after 40-50 potential cycles of deposition. Nb and Co/Ni are detected in the films by EDX. ICP-MS results show an elemental ratio of 1:1 for Co:Nb and 1:3 for Ni:Nb, respectively. Raman spectra reveal the presence of both [Nb6O19](8) and Co(OH)(2)/Ni(OH)(2). The films exhibit excellent stability and efficiency for electrocatalytic water oxidation in alkaline solution. Turnover frequencies of 12.9 and 13.2 s(-1) were determined by rotating ring disk electrode voltammetry at an overpotential of 480 mV for Co and Ni films, respectively. Fourier transformed large amplitude alternating current (FTAC) voltammetry reveals an additional underlying oxidation process for Co under catalytic turnover conditions, which indicates that a Co-IV species is involved in the efficient catalytic water oxidation reactions. FTAC voltammetric data also suggest that the Ni films undergoes a clear phase transformation upon aging in aqueous 1 M NaOH and the electrogenerated higher oxidation state Ni from beta-NiOOH is the more active form of the catalyst.
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| 3386. |
- Liu, Ying, et al.
(author)
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Reviewing estimates of the basic reproduction number for dengue, Zika and chikungunya across global climate zones
- 2020
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In: Environmental Research. - : Elsevier. - 0013-9351 .- 1096-0953. ; 182
-
Journal article (peer-reviewed)abstract
- BACKGROUND: Globally, dengue, Zika virus, and chikungunya are important viral mosquito-borne diseases that infect millions of people annually. Their geographic range includes not only tropical areas but also sub-tropical and temperate zones such as Japan and Italy. The relative severity of these arboviral disease outbreaks can vary depending on the setting. In this study we explore variation in the epidemiologic potential of outbreaks amongst these climatic zones and arboviruses in order to elucidate potential reasons behind such differences.METHODOLOGY: We reviewed the peer-reviewed literature (PubMed) to obtain basic reproduction number (R0) estimates for dengue, Zika virus, and chikungunya from tropical, sub-tropical and temperate regions. We also computed R0 estimates for temperate and sub-tropical climate zones, based on the outbreak curves in the initial outbreak phase. Lastly we compared these estimates across climate zones, defined by latitude.RESULTS: Of 2115 studies, we reviewed the full text of 128 studies and included 65 studies in our analysis. Our results suggest that the R0 of an arboviral outbreak depends on climate zone, with lower R0 estimates, on average, in temperate zones (R0 = 2.03) compared to tropical (R0 = 3.44) and sub-tropical zones (R0 = 10.29). The variation in R0 was considerable, ranging from 0.16 to 65. The largest R0 was for dengue (65) and was estimated by the Ross-Macdonald model in the tropical zone, whereas the smallest R0 (0.16) was for Zika virus and was estimated statistically from an outbreak curve in the sub-tropical zone.CONCLUSIONS: The results indicate climate zone to be an important determinant of the basic reproduction number, R0, for dengue, Zika virus, and chikungunya. The role of other factors as determinants of R0, such as methods, environmental and social conditions, and disease control, should be further investigated. The results suggest that R0 may increase in temperate regions in response to global warming, and highlight the increasing need for strengthening preparedness and control activities.
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| 3387. |
- Liu, Y., et al.
(author)
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Species delimitation of the white-tailed rubythroat Calliope pectoralis complex (Aves, Muscicapidae) using an integrative taxonomic approach
- 2016
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In: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 47:6, s. 899-910
-
Journal article (peer-reviewed)abstract
- Our knowledge of the systematics and taxonomy of Asian birds has improved much in the last two decades, and the number of recognised species has increased significantly as a result of in-depth studies using an integrative taxonomic approach. The Sino-Himalayan mountains harbor a high level of passerine diversity. Several allopatric or parapatric taxa that are currently treated as subspecies of polytypic species within that region are likely to deserve full species status, and thus their taxonomic status needs to be revisited. Based on analyses of multilocus data, vocalizations and morphology, we propose that the white-tailed rubythroat Calliope pectoralis should be treated as two species, the Himalayan rubythroat C. pectoralis sensu stricto in the Tian Shan and Himalayan mountains, and the Chinese rubythroat C. tschebaiewi in the mountains of southwestern and north-central China. According to our dating analyses based on mitochondrial loci, these two species diverged approximately 2.2 million yr ago. We further found that C. tschebaiewi was paraphyletic to C. pectoralis sensu stricto in nuclear data, which demonstrates a state of mitonuclear discordance that warrants further work. Our results suggest that geographic changes and glacial cycles in the Pleistocene may have caused allopatric divergence in the C. pectoralis complex. Our study stresses the importance of applying an integrative taxonomy approach to fully unravel the true avian diversity in the Sino-Himalayan Mountains.
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| 3388. |
- Liu, YJ, et al.
(author)
-
Splenic denervation suppresses mRNA gene expression and protein production of IL-1beta and IL-6 by peritoneal macrophages in both Trypanosoma brucei brucei-infected and non-infected rats
- 2004
-
In: Neuroimmunomodulation. - : S. Karger AG. - 1021-7401 .- 1423-0216. ; 11:2, s. 113-118
-
Journal article (peer-reviewed)abstract
- <i>Objective:</i> To test the hypothesis that the nervous system participates in modulating the immune response during experimental African trypanosomiasis caused by <i>Trypanosoma brucei brucei</i>. <i>Methods and Results:</i> Using in situ hybridization and immunochemistry, we studied the effects of splenic sympathectomy on mRNA gene expression and protein production of IL-1β and IL-6 in splenic and peritoneal macrophages (PMΦ) of Sprague-Dawley rats infected with <i>T. brucei brucei</i> and non-infected rats. The enhancements of mRNA gene expression and production of IL-1β and IL-6 by peritoneal macrophages were significantly suppressed by the splenic sympathectomy in both infected and non-infected rats. <i>Conclusions:</i> Our data indicate a probably stimulatory role of the sympathetic nervous system during the host immune response in both normal and <i>T. brucei brucei</i>-infected rats.
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| 3389. |
- Liu, Yueqiang, 1971, et al.
(author)
-
Toroidal modelling of RMP response in ASDEX Upgrade: coil phase scan, q(95) dependence, and toroidal torques
- 2016
-
In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 56:5
-
Journal article (peer-reviewed)abstract
- The plasma response to the vacuum resonant magnetic perturbation (RMP) fields, produced by the ELM control coils in ASDEX Upgrade experiments, is computationally modelled using the MARS-F/K codes (Liu et al 2000 Phys, Plasmas 7 3681, Liu et al 2008 Phys. Plasmas 15 112503), A systematic investigation is carried out, considering various plasma and coil configurations as in the ELM control experiments. The low q plasmas, with q95 3.8 (q95 is the safety factor q value at 95% of the equilibrium poloidal flux), responding to low a (n is the toroidal mode number) field perturbations from each single row of the ELM coils, generates a core kink amplification effect. Combining two rows, with different toroidal phasing, thus leads to either cancellation or reinforcement of the core kink response, which in turn determines the poloidal location of the peak plasma surface displacement, The core kink response is typically weak for the a = 4 coil configuration at low q, and for the n = 2 configuration but only at high q (q(95) similar to 5.5). A phase shift of around 60 degrees for low q plasmas, and around 90 degrees for high q plasmas, is found in the coil phasing, between the plasma response field and the vacuum RMP field, that maximizes the edge resonant field component, This leads to an optimal coil phasing of about 100 (-100) degrees for low (high) q plasmas, that maximizes both the edge resonant field component and the plasma surface displacement near the X-point of the separatrix. This optimal phasing closely corresponds to the best ELM mitigation observed in experiments. A strong parallel sound wave damping moderately reduces the core kink response but has minor effect on the edge peeling response. For low q plasmas, modelling shows that both the resonant electromagnetic torque and the neoclassical toroidal viscous (NTV) torque (due to the presence of 3D magnetic field perturbations) contribute to the toroidal flow damping, in particular near the plasma edge region. For high q plasmas, however, significant amount of torque is also produced in the bulk plasma region, and the contributions from the electromagnetic, the NTV, and the torque associated with the Reynolds stress, all
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| 3390. |
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