| 1. |
|
|
| 2. |
- Lu, Quanming, et al.
(författare)
-
Features of separatrix regions in magnetic reconnection : Comparison of 2-D particle-in-cell simulations and Cluster observations
- 2010
-
Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115:11
-
Tidskriftsartikel (refereegranskat)abstract
- In collisionless magnetic reconnection, the in-plane Hall currents are carried mainly by the magnetized electrons. The in-plane Hall currents are directed toward the X line along the magnetic field lines just inside the separatrices and away from the X line along the separatrices. Such a current system leads to the quadrupole out-of-plane magnetic field with the peaks between the regions carrying the in-plane currents. Simultaneously, the electron flow toward the X line along the separatrices causes electron density depletions along the separatrices. In this paper, the features of separatrix regions in magnetic reconnection and the relations between the electron density depletions and the out-of-plane magnetic field are investigated with both two-dimensional particle-in-cell simulations and Cluster observations. We conclude that the electron density depletions are formed because of the magnetic mirror, and they are outside the peaks of the out-of-plane magnetic field. Such a theoretical prediction is confirmed by both simulations and observations.
|
|
| 3. |
- Lu, San, et al.
(författare)
-
Magnetotail reconnection onset caused by electron kinetics with a strong external driver
- 2020
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetotail reconnection plays a crucial role in explosive energy conversion in geospace. Because of the lack of in-situ spacecraft observations, the onset mechanism of magnetotail reconnection, however, has been controversial for decades. The key question is whether magnetotail reconnection is externally driven to occur first on electron scales or spontaneously arising from an unstable configuration on ion scales. Here, we show, using spacecraft observations and particle-in-cell (PIC) simulations, that magnetotail reconnection starts from electron reconnection in the presence of a strong external driver. Our PIC simulations show that this electron reconnection then develops into ion reconnection. These results provide direct evidence for magnetotail reconnection onset caused by electron kinetics with a strong external driver.
|
|
| 4. |
- Song, Dan-Na, et al.
(författare)
-
Luminescent Thermochromic Silver Iodides as Wavelength-Dependent Thermometers
- 2020
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:18, s. 13067-13077
-
Tidskriftsartikel (refereegranskat)abstract
- Luminescent thermochromic materials with a dramatic shift of emission band under different temperatures are highly desirable in temperature sensing fields. However, the design of the synthesis of such compounds remains a great challenge. In this work, two new luminescent thermochromic silver iodides, (emIm)Ag3I4 (1) and (emIm)Ag2I3 (2) (emIm = 1-ethyl-3-methyl imidazole), have been synthesized under solvothermal conditions. Compound 1 features a [Ag3I4]− anionic layer, while compound 2 possesses an infinite [Ag2I3]− chain structure, both of which are charge balanced by emIm+ cations. Particularly, they display luminescent thermochromism with a significant wavelength shift of emission maximum with temperature change. They represent rare examples of infinite layered or chain silver iodides that show luminescent thermochromism. Furthermore, the results indicate that compounds 1 and 2 are promising wavelength-dependent luminescent thermometers.
|
|
| 5. |
- Wang, Kuan, et al.
(författare)
-
Threshold switching memristor-based stochastic neurons for probabilistic computing
- 2021
-
Ingår i: Materials Horizons. - : Royal Society of Chemistry. - 2051-6347 .- 2051-6355. ; 8:2, s. 619-629
-
Tidskriftsartikel (refereegranskat)abstract
- Biological neurons exhibit dynamic excitation behavior in the form of stochastic firing, rather than stiffly giving out spikes upon reaching a fixed threshold voltage, which empowers the brain to perform probabilistic inference in the face of uncertainty. However, owing to the complexity of the stochastic firing process in biological neurons, the challenge of fabricating and applying stochastic neurons with bio-realistic dynamics to probabilistic scenarios remains to be fully addressed. In this work, a novel CuS/GeSe conductive-bridge threshold switching memristor is fabricated and singled out to realize electronic stochastic neurons, which is ascribed to the similarity between the stochastic switching behavior observed in the device and that of biological ion channels. The corresponding electric circuit of a stochastic neuron is then constructed and the probabilistic firing capacity of the neuron is utilized to implement Bayesian inference in a spiking neural network (SNN). The application prospects are demonstrated on the example of a tumor diagnosis task, where common fatal diagnostic errors of a conventional artificial neural network are successfully circumvented. Moreover, in comparison to deterministic neuron-based SNNs, the stochastic neurons enable SNNs to deliver an estimate of the uncertainty in their predictions, and the fidelity of the judgement is drastically improved by 81.2%.
|
|
| 6. |
- Wang, Rongsheng, et al.
(författare)
-
An Electron-Scale Current Sheet Without Bursty Reconnection Signatures Observed in the Near-Earth Tail
- 2018
-
Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 45:10, s. 4542-4549
-
Tidskriftsartikel (refereegranskat)abstract
- Observations of a current sheet as thin as the electron scale are extremely rare in the near-Earth magnetotail. By measurement from the novel Magnetospheric Multiscale mission in the near-Earth magnetotail, we identified such an electron-scale current sheet and determined its detailed properties. The electron current sheet was bifurcated, with a half-thickness of nine electron inertial lengths, and was sandwiched between the Hall field. Because of the strong Hall electric field, the super-Alfvenic electron bulk flows were created mainly by the electric field drift, leading to the generation of the strong electron current. Inevitably, a bifurcated current sheet was formed since the Hall electric field was close to zero at the center of the current sheet. Inside the electron current sheet, the electrons were significantly heated while the ion temperature showed no change. The ions kept moving at a low speed, which was not affected by this electron current sheet. The energy dissipation was negligible inside the current sheet. The observations indicate that a thin current sheet, even as thin as electron scale, is not the sufficient condition for triggering bursty reconnection.
|
|
| 7. |
- Wang, Rongsheng, et al.
(författare)
-
Interaction of Magnetic Flux Ropes Via Magnetic Reconnection Observed at the Magnetopause
- 2017
-
Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 122:10, s. 10436-10447
-
Tidskriftsartikel (refereegranskat)abstract
- Using the high-resolution field and plasma data obtained from the Magnetospheric Multiscale mission at the magnetopause, a series of three flux transfer events was observed one after another inside southward ion flows, without time gap between any two successive flux ropes. Using the plasma measurements, the current densities within the flux ropes were studied in detail. The currents within the first two flux ropes, dubbed Fr1 and Fr2, were composed of a series of well-separated filamentary currents. The thickness of the filamentary currents and the gap between them were sub ion scale, occasionally dropped down to electron scale. In the third flux rope Fr3 which was closest to the expected reconnection X line, the current displayed a singular compact current layer, was ion scale in width and concentrated on its center. Considering the location of the flux ropes relative to the reconnection X line, we suggested that the current density could be a singular structure when the flux rope was just created and then fragmented into a series of filamentary currents as time. By examining the interregions between Fr1 and Fr2, and between Fr2 and Fr3, reconnection was only confirmed to occur between Fr2 and Fr3 and no reconnection signature was found between Fr1 and Fr2. It seems that magnetic field compression resulted from collision of two neighboring flux ropes is one necessary condition for the occurrence of the coalescence.
|
|
| 8. |
|
|
| 9. |
- Li, Ji-Lei, et al.
(författare)
-
Uncovering and quantifying the subduction zone sulfur cycle from the slab perspective
- 2020
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Sulfur belongs among H2O, CO2, and Cl as one of the key volatiles in Earth’s chemical cycles. High oxygen fugacity, sulfur concentration, and δ34S values in volcanic arc rocks have been attributed to significant sulfate addition by slab fluids. However, sulfur speciation, flux, and isotope composition in slab-dehydrated fluids remain unclear. Here, we use high-pressure rocks and enclosed veins to provide direct constraints on subduction zone sulfur recycling for a typical oceanic lithosphere. Textural and thermodynamic evidence indicates the predominance of reduced sulfur species in slab fluids; those derived from metasediments, altered oceanic crust, and serpentinite have δ34S values of approximately −8‰, −1‰, and +8‰, respectively. Mass-balance calculations demonstrate that 6.4% (up to 20% maximum) of total subducted sulfur is released between 30–230 km depth, and the predominant sulfur loss takes place at 70–100 km with a net δ34S composition of −2.5 ± 3‰. We conclude that modest slab-to-wedge sulfur transport occurs, but that slab-derived fluids provide negligible sulfate to oxidize the sub-arc mantle and cannot deliver 34S-enriched sulfur to produce the positive δ34S signature in arc settings. Most sulfur has negative δ34S and is subducted into the deep mantle, which could cause a long-term increase in the δ34S of Earth surface reservoirs.
|
|
| 10. |
|
|
| 11. |
- Zhang, Pan, et al.
(författare)
-
Nanochannel-Based Transport in an Interfacial Memristor Can Emulate the Analog Weight Modulation of Synapses
- 2019
-
Ingår i: Nano letters (Print). - : AMER CHEMICAL SOC. - 1530-6984 .- 1530-6992. ; 19:7, s. 4279-4286
-
Tidskriftsartikel (refereegranskat)abstract
- By exploiting novel transport phenomena such as ion selectivity at the nanoscale, it has been shown that nanochannel systems can exhibit electrically controllable conductance, suggesting their potential use in neuromorphic devices. However, several critical features of biological synapses, particularly their conductance modulation, which is both memorable and gradual, have rarely been reported in these types of systems due to the fast flow property of typical inorganic electrolytes. In this work, we demonstrate that electrically manipulating the nanochannel conductance can result in nonvolatile conductance tuning capable of mimicking the analog behavior of synapses by introducing a room-temperature ionic liquid (IL) and a KCl solution into the two ends of a nanochannel system. The gradual conductance-tuning mechanism is identified through fluorescence measurements as the voltage-induced movement of the interface between the immiscible IL and KCl solution, while the successful memorization of the conductance tuning is ascribed to the large viscosity of the IL. We applied a nanochannel-based synapse to a handwritten digit-recognition task, reaching an accuracy of 94%. These promising results provide important guidance for the future design of nanochannel-based neuromorphic devices and the manipulation of nanochannel transport for computing.
|
|
| 12. |
- Zhao, Qiao, et al.
(författare)
-
On the formation of a side product with hexahydroaporphine-like structure in the Grewe cyclization of dextromethorphan
- 2017
-
Ingår i: Research on Chemical Intermediates. - : Springer Science and Business Media LLC. - 0922-6168 .- 1568-5675. ; 43:3, s. 1689-1708
-
Tidskriftsartikel (refereegranskat)abstract
- Factors leading to the formation of a hexahydroaporphine-like cyclizing side product were studied systematically for the first time and the ratio of this side product was controlled effectively. To understand better the electronic effect of substrates on the formation of side products, different 1-benzyloctahydroisoquinolines with substituted groups on nitrogen or benzene ring were compared. A plausible mechanism of cyclizing reaction was proposed, and key intermediates as well as transition states were analyzed using DFT calculations.
|
|
