[en] Using a unitary transformation, the Dirac equation with a time-dependent linear potential is transformed into a Schroedinger equation for a particle moving in an effective external magnetic field, which can be solved by the Lewis-Riesenfeld invariant theory. The wavefunction is written in a complete form. It is also shown that in the non-relativistic limit, matrix elements of the velocity operator go to the classical velocity when there is an arbitrary external potential and a magnetic field

[en] Exact solutions to the Dirac equations with a time-dependent mass and a static magnetic field or a time-dependent linear potential are given. Matrix elements of the coordinate, momentum and velocity operator are calculated. In the large quantum number limit, these matrix elements give the classical solution

[en] Using the trial-function method, the general solution of the Schroedinger equation for the time-dependent linear potential is obtained. Based on the Heisenberg correspondence principle, the solution of the classical equation of motion is derived from the quantum matrix elements. (author)

[en] Objective: To analysis the value of ungated computed tomography in evaluating coronary artery calcification and the factors influencing coronary artery calcification in patients with chronic obstructive pulmonary disease (COPD). Methods: A preliminarily evaluation of coronary artery calcification was performed in 329 patients who met the diagnostic criteria of COPD and underwent chest CT scan during January 2016-December 2017 in our hospital. Finally, 67 patients were enrolled, including 53 males and 14 females, aged from 55 to 82 years, with an average age 68.71 ± 8.10 years. All enrolled patients were evaluated for coronary artery calcium score (CACS) with a thin layer reconstruction on mediastinal window. Patients were divided into calcification-free group (CACS = 0, n = 28) and calcification group (CACS > 0, n = 39). In the univariate analysis, independent samples t test or χ² square test was used to compare the indexes between the 2 groups. A Logistic regression analysis was used to determine the influencing factors of coronary artery calcification. Scatter plot was used to present the correlation between the percentage of forced expiratory volume in one second (FEV1%) and CACS in the calcification group. Results: Duration of COPD and FEV1% were significant different between two groups in the univariate analysis (P < 0.05). Feeding the duration of COPD and FEV1% in the logistic regression, only FEV1% significantly (P = 0.001) contributed to the CACS (OR = 0.932, 95% CI: 0.893 ∼ 0.972). There was a negative correlation between FEV1% and CACS in the calcification group. Conclusion: Ungated CT can evaluate coronary artery calcification in COPD patients. FEV1% was a protective factor of coronary artery calcification in COPD patients. (authors)

[en] A (CCO)_0.25(YSZ)_0.75 solid solution (YSZ is Y₂O₃-stabilized ZrO₂; CCO is an abbreviation of Ce_0.9Ca_0.1O_1.9) was successfully synthesized by a solid-state method. A composite anode material, NYC_x (60 wt% NiO+40 wt% (CCO)_x(YSZ)_1-x), for SOFCs (solid oxide fuel cells) was prepared. XRD results suggest that a solid solution reaction occurs between YSZ and CCO after sintering at 1400 deg. C for 10 h. From the impedance results, the conclusion can be drawn that the (CCO)_0.25(YSZ)_0.75 solid solution is a mixed conductor (ionic and electronic). Its total conductivity is greater than that of YSZ. The NYC_x (x>0) anodes exhibited better performance than the commonly used Ni+YSZ anode with regards to overpotential and anode interfacial impedance, with the NYC_0.25 anode exhibiting the best performance

[en] Highlights: • Highly CO₂-soluble ethylene oxide diphosphates were designed and synthesized. • Solubility were determined and correlated by Bartle and Chrastil model. • Partial molar volumes of these compounds in scCO₂ were estimated. • Branched side chain played an important role in the enhancement of solubility. -- Abstract: The solubility of newly synthesized chelating agents, i.e., tetraethylene glycol bis (2-ethylhexyl) dimethyl diphosphate (EG4EH), tetraethylene glycol bis (n-octyl) dimethyl diphosphate (EG4Oct), and tetraethylene glycol bis (2-butoxyethyl) dimethyl diphosphate (EG4BOE) in supercritical carbon dioxide (scCO₂) were determined at temperatures ranging from (318.15 to 333.15) K and pressures ranging from (12 to 21) MPa. Solubility increases in the order of EG4Oct (MW = 606.33) < EG4BOE (MW = 582.26) < EG4EH (MW = 606.33), indicating that branched side chains of the ligands play an important part in increasing solubility in scCO₂. Semi empirical density-based models proposed by Bartle and Chrastil were used to correlate the experimental data, and AARD values were calculated to be (1.2 to 2.9)% and (0.40 to 0.93)% for Bartle and Chrastil model, respectively. Additionally, the partial molar volumes of those compounds were estimated following the theory developed by Kumar and Johnston

[en] Polyethylene glycol (PEG) esters are important, nontoxic and biodegradable non-ionic surfactants. A key procedure in producing PEG esters is their separation from unreacted or excess acids. We propose an adsorption method using the weakly basic anion exchange resins for the separation of organic acids and PEG esters for the first time. With α-tocopheryl polyethylene glycol succinate (TPGS) and α-tocopheryl succinate (α-TS) as the examples of PEG ester and organic acid, respectively, single-component equilibrium experiments revealed the great potential of this method. Studies on the adsorption equilibrium, thermodynamics and kinetics of α-TS onto a weakly basic anion exchange resin were also carried out. This research is not only important for the production of TPGS, but also instructive for the separation of other PEG-esters from the reaction mixtures

[en] On the basis of remote-sensing information and geological environments for the formation of in-situ leachable sandstone-type uranium deposits such as geomorphic features, distribution of drainage system, and paleo-alluvial (diluvial) fans and time-space distribution regularities of orehosting rocks and sandstone bodies in Songliao and Liaohe faulted-depressed basins, image features, tectonic patterns and paleo-geographic environment of the prospective areas are discussed for both basins, and based on a great number of petroleum-geological data and comparison analysis, a remote sensing-geological prospecting model for in-situ leachable sandstonetype uranium deposits in the region is established, providing indications for selection of prospective area

[en] ZrN films were prepared using microwave electron cyclotron resonance (MW-ECR) plasma enhanced unbalanced magnetron sputtering (PE-UMS) technique. The plasma characteristics near the holder were diagnosed by Langmuir probe for various deposition conditions and the films obtained were characterized by electron probe microanalysis x-ray diffraction and microhardness. As the N₂ flow rate increases from 2 to 20sccm, the ion density initially increases from 8.07 x 10⁹ to 8.31 x 10⁹ cm^-3 and then decreases to 7.52 x 10⁹ cm^-3, while the N₂⁺ ion density increases monotonically from 3.12 x 10⁸ to 3.35 x 10⁹ cm^-3 and the electron temperature does not vary much. The N concentration in the films increases and the grain size decreases as the N₂⁺ ion density increases. And the films become more and more amorphous as the N/Zr ratio is above 1.4. The corresponding microhardness of the deposited films increases from 22.5 GPa to the maximum of 26.78 GPa, and then decreases linearly to 19.82 GPa as the N₂ flow rate increases from 8 to 14sccm. The mechanism of the influence of the plasma characteristics on the microstructure and mechanical properties of the deposited films were discussed. (author)

[en] The unique composite of Ni@NiO core/shell structure and active carbon (AC) had been synthesized through a two-step method. The Ni"2"+ was first reduced to Ni on the surface of AC supporter. Then the NiO shell was obtained after the following oxidized treatment. The transmission electron microscopy (TEM) observed that Ni@NiO particles with thin shell were sporadically dispersed on AC surface without vast reaggregation. And the electrochemical impedance spectroscopy (EIS) showed that Ni@NiO_c_o_r_e_-_s_h_e_l_l/AC composite had higher electrical conductivity. Thus, the outside thin NiO shell would expose more electroactive surface and shorten the ionic diffusion distance. While the Ni core could accelerate the electronic transport due to its low contact resistance. When employed as supercapacitor electrodes, Ni@NiO_c_o_r_e_-_s_h_e_l_l/AC composite exhibited a high specific capacitance of ca. 700 F g"−"1 at 0.5 A g"−"1 and remained above 90% of the initial capacity after 1000 cycles at 1 A g"−"1. The high specific capacitance and long cycle life of the hybrid structure made it alternative for energy storage systems