Array of nanosheets render ultrafast and high-capacity Na-ion storage by tunable pseudocapacitance

Sodium-ion batteries are a potentially low-cost and safe alternative to the prevailing lithium-ion battery technology. However, it is a great challenge to achieve fast charging and high power density for most sodium-ion electrodes because of the sluggish sodiation kinetics. Here we demonstrate a high-capacity and high-rate sodium-ion anode based on ultrathin layered tin(II) sulfide nanostructures, in which a maximized extrinsic pseudocapacitance contribution is identified and verified by kinetics analysis. The graphene foam supported tin(II) sulfide nanoarray anode delivers a high reversible capacity of ∼1,100 mAh g−1 at 30 mA g−1 and ∼420 mAh g−1 at 30 A g−1, which even outperforms its lithium-ion storage performance. The surface-dominated redox reaction rendered by our tailored ultrathin tin(II) sulfide nanostructures may also work in other layered materials for high-performance sodium-ion storage.Dongliang Chao, Changrong Zhu, Peihua Yang, Xinhui Xia, Jilei Liu, Jin Wang, Xiaofeng Fan, Serguei V. Savilov, Jianyi Lin, Hong Jin Fan, Ze Xiang She

Evolution and Flare Activity of Delta-Sunspots in Cycle 23

The emergence and magnetic evolution of solar active regions (ARs) of beta-gamma-delta type, which are known to be highly flare-productive, were studied with the SOHO/MDI data in Cycle 23. We selected 31 ARs that can be observed from their birth phase, as unbiased samples for our study. From the analysis of the magnetic topology (twist and writhe), we obtained the following results. i) Emerging beta-gamma-delta ARs can be classified into three topological types as "quasi-beta", "writhed" and "top-to-top". ii) Among them, the "writhed" and "top-to-top" types tend to show high flare activity. iii) As the signs of twist and writhe agree with each other in most cases of the "writhed" type (12 cases out of 13), we propose a magnetic model in which the emerging flux regions in a beta-gamma-delta AR are not separated but united as a single structure below the solar surface. iv) Almost all the "writhed"-type ARs have downward knotted structures in the mid portion of the magnetic flux tube. This, we believe, is the essential property of beta-gamma-delta ARs. v) The flare activity of beta-gamma-delta ARs is highly correlated not only with the sunspot area but also with the magnetic complexity. vi) We suggest that there is a possible scaling-law between the flare index and the maximum umbral area

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.</p

Leaf development and photosynthetic properties of three tropical tree species with delayed greening

Leaf developmental patterns were characterized for three tropical tree species with delayed greening. Changes in the pigment contents, photosynthetic capacity, stomata development, photosystem 2 efficiency, rate of energy dissipation, and the activity of partial protective enzymes were followed in developing leaves in an attempt to elucidate the relative importance of various photoprotective mechanisms during leaf ontogeny. Big leaves of Anthocephalus chinensis, a fast-growing light demanding species, expanded following an exponential pattern, while relatively small leaves of two shade-tolerant species Litsea pierrei and Litsea dilleniifolia followed a sigmoidal pattern. The juvenile leaves of A. chinensis and L. pierrei contained anthocyanin located below the upper epidermis, while L. dilleniifolia did not contain anthocyanin. Leaves of A. chinensis required about 12 d for full leaf expansion (FLE) and photosynthetic development was delayed 4 d, while L. pierrei and L. dilleniifolia required 18 or 25 d for FLE and photosynthetic development was delayed 10 or 15 d, respectively. During the leaf development the increase in maximum net photosynthetic rate was significantly related to changes in stomatal conductance and the leaf maturation period was positively related to the steady-state leaf dry mass per area for the three studied species. Dark respiration rate of leaves at developing stages was greater, and pre-dawn initial photochemical efficiency was lower than that of mature leaves. Young leaves displayed greater energy dissipation than mature leaves, but nevertheless, the diurnal photoinhibition of young L. dilleniifolia leaves was higher than that of mature leaves. The young red leaves of A. chinensis and L. pierrei with high anthocyanin contents and similar diurnal photoinhibition contained more protective enzymes (superoxide dismutase, ascorbate peroxidase) than mature leaves. Consequently, red leaves may have higher antioxidant ability

Micro-Raman and photoluminescence investigation of ZnxCd1-xSe thin film under high pressure

Journal of Applied Physics8495198-5201JAPI

Dynamic characterization method of accelerometers based on the Hopkinson bar calibration system

The dynamic characterization of accelerometers is the prerequisite and insurance for highly accurate measurement of dynamic acceleration signals. The main problem of dynamic characterization is the lack of effective methods to deal with model coefficients and the order coupling effect, which could severely influence the identification accuracy. This paper presents a novel approach to solve the identification coupling problem through synchronous iteration and compensation. In order to guarantee the precision of the dynamic model, the Hopkinson bar dynamic calibration system with a traceable excitation acceleration signal is proposed. The feasibility of dynamic modelling is proved by the data comparison of experiment result and model regression result in the time domain. Based on the dynamic model, a dynamic compensation model is established, which improves the dynamic performance by frequency coverage extension. Finally, the results of the dynamic modelling and dynamic compensation are demonstrated by means of the calibration experiment in the paper

Photoluminescence and growth mechanism of amorphous silica nanowires by vapor phase transport

10.1016/j.physe.2005.12.159Physica E: Low-Dimensional Systems and Nanostructures312218-223PELN