[en] We study high-order harmonic generation (HHG) by solving a two-dimensional time-dependent Schrödinger equation (TDSE) for a hydrogen molecular ion H₂ ⁺. A double plateau structure is detected in harmonic spectra, the wavelet time-frequency analysis and an extended semiclassical analysis show that the width of the first plateau can be used to estimate the internuclear distance of H₂ ⁺. (paper)

[en] The low-order harmonic generation of hydrogen molecular ion interacting with a linearly polarized laser field has been investigated theoretically by using a simple two-state model. The validity of the two-state model is carefully examined by comparing the harmonic spectra of hydrogen molecular ion obtained from this model with those from the three-dimensional time-dependent Schrödinger equation. When combined with the Morlet transform of quantum time-frequency spectrum, the two-state model can be used to study the dynamical origin of the low-order harmonic generation of hydrogen molecular ion driven by low-frequency pulses. In addition, some interesting structures of the time profiles for low order harmonics are obtained. (paper)

[en] Terahertz (THz) wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional (1D) time-dependent Schrödinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound–bound and continuum–continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime. (paper)

[en] Based on spectrum analysis, we provide the arithmetic expressions of the quasi 11 yr cycle, 110 yr century cycle of relative sunspot numbers, and quasi 22 yr cycle of solar magnetic field polarity. Based on a comparative analysis of the monthly average geopotential height, geopotential height anomaly, and temperature anomaly of the northern hemisphere at locations with an air pressure of 500 HPa during the positive and negative phases of AO (Arctic Oscillation), one can see that the abnormal warming period in the Arctic region corresponds to the negative phase of AO, while the anomalous cold period corresponds to its positive phase. This shows that the abnormal change in the Arctic region is an important factor in determining the anomalies of AO. In accordance with the analysis performed using the successive filtering method, one can see that the AO phenomenon occurring in January shows a clear quasi 88 yr century cycle and quasi 22 yr decadal cycle, which are closely related to solar activities. The results of our comparative analysis show that there is a close inverse relationship between the solar activities (especially the solar magnetic field index changes) and the changes in the 22 yr cycle of the AO occurring in January, and that the two trends are basically opposite of each other. That is to say, in most cases after the solar magnetic index MI rises from the lowest value, the solar magnetic field turns from north to south, and the high-energy particle flow entering the Earth's magnetosphere increases to heat the polar atmosphere, thus causing the AO to drop from the highest value; after the solar magnetic index MI drops from the highest value, the solar magnetic field turns from south to north, and the solar high-energy particle flow passes through the top of the Earth's magnetosphere rather than entering it to heat the polar atmosphere. Thus the polar temperature drops, causing the AO to rise from the lowest value. In summary, the variance contribution rate of the changes in the quasi 110 yr century cycle and quasi 22 yr decadal cycle for the AO reaches 62.9%, indicating that solar activity is an important driving factor of the AO.

[en] The photoluminescence emission of the ZnO microcavity coupled with the plasmon has three kinds of modes: the emission modes in the band-edge emission band, the wide emission modes and the thin emission modes in the defect-related emission band. The emission modes in the band-edge emission band are the plasmon coupled exciton polariton with the effective refractive index of 2.04. The exciton coupling equation with the effective refractive index can describe the coupling between the exciton, plasmon and microcavity very well. The wide emission modes in the visible band are the plasmon coupled transverse Fabry–Perot modes with the effective refractive index of 1.84 at the wavelength of 580 nm (2.14 eV). The thin emission modes in the visible band are the plasmon coupled WGM with the effective refractive index of 1.87 at the wavelength of 566.1 nm (2.190 eV). Because of the phase difference of the two polarizations in the total internal reflections, doubled modes are observed for the WGM, which leads to the thin modes in the visible band

[en] Highlights: • Laves and sigma phase nucleated at grain/sub-grain boundaries during solution annealing. • Prior-formation of Laves phase particles impeded the recovery and recrystallization of the deformed microstructure. • Precipitation of sigma and Laves phase particles at boundaries led to the embrittlement. -- Abstract: The microstructural evolution, precipitation, and mechanical properties of 27Cr-4Mo-2Ni steels were investigated by using SEM/EBSD and TEM/STEM technique, and the RT impact test. Experimental results demonstrate that the elongated grains are gradually transformed to recrystallization grains after high temperature annealing. Both sigma and Laves phase were found nucleated at grain boundaries and/or sub-grain boundaries during annealing below 1100 °C except for Nb(C, N) and TiN particles. Recrystallization of 111 orientated deformation regions were impede due to the pinning effect of Laves phase particles at sub-grain boundaries accompanied by the missing of γ-fiber texture. The recrystallization grains are still kept elongated along the rolling direction for the hindrance of fine Nb(C, N) formed at initial hot rolled grain boundaries. Formation of Laves and sigma phase particles shows great influence on the mechanical properties, such as the decrease of the tensile elongation and the impact toughness, and the emergence of brittle fracture during the tensile or impact test. Solution treatment should be strictly controlled above 1050 °C with water quenching to avoid the embrittlement of the test steels.

[en] The sluggish Ni(II)/Ni(III) redox cycle does not benefit perxymonosulfate (PMS) activation for recalcitrant pollutant degradation. To solve this problem, a heterogeneous catalyst, Cu_0.2Ni_0.8O/SBA-15 (CNS), was constructed to activate PMS for decomposing two sulfonamide antibiotics, sulfachlorpyridazine (SACP) and sulfapyridine (SAP). SACP and SAP were completely degraded over Cu_0.2Ni_0.8O/SBA-15/PMS (CNSP) after 90 min. O₂^.- was the dominant active species involved in the degradation of SACP and SAP. Structural analysis and elemental valence state observations indicated that Cu(Ⅰ) provided electrons through Cu–O–Ni bonds to realize the charge compensation for Ni(Ⅲ) in the CNSP system. Thus, the in situ Cu(I)/Cu(II) promoting the Ni(II)/Ni(III) cycle could accelerate the PMS activation. This work provides new insights into the electron transfer between transition metals and the charge compensation mechanism for PMS activation. The degradation mechanism was proposed based on the XPS results before and after the reaction, a radical quenching test, and an EPR test. Combined with the SACP and SAP degradation intermediates identified by LC-MS, we suggest that the choice of treatment process depends on the occurrence of a steric hindrance effect between the molecular structure of the degradation target and free radicals.

[en] Highlights: • A novel method was developed to detect extreme drought-induced loss of ecosystem function globally. • Large well-known extreme drought events were detected mainly in semi-arid regions. • GPP reduction caused by functional loss could explain ≥70% of the interannual variation in GPP in drought-affected areas. Quantifying the ecological patterns of loss of ecosystem function in extreme drought is important to understand the carbon exchange between the land and atmosphere. Rain-use efficiency [RUE; gross primary production (GPP)/precipitation] acts as a typical indicator of ecosystem function. In this study, a novel method based on maximum rain-use efficiency (RUE_max) was developed to detect losses of ecosystem function globally. Three global GPP datasets from the MODIS remote sensing data (MOD17), ground upscaling FLUXNET observations (MPI-BGC), and process-based model simulations (BESS), and a global gridded precipitation product (CRU) were used to develop annual global RUE datasets for 2001–2011. Large, well-known extreme drought events were detected, e.g. 2003 drought in Europe, 2002 and 2011 drought in the U.S., and 2010 drought in Russia. Our results show that extreme drought-induced loss of ecosystem function could impact 0.9% ± 0.1% of earth's vegetated land per year and was mainly distributed in semi-arid regions. The reduced carbon uptake caused by functional loss (0.14 ± 0.03 PgC/yr) could explain >70% of the interannual variation in GPP in drought-affected areas (p ≤ 0.001). Our results highlight the impact of ecosystem function loss in semi-arid regions with increasing precipitation variability and dry land expansion expected in the future.