Wave-Packet Surface Propagation for Light-Induced Molecular Dissociation

Recent advances in laser technology have enabled tremendous progress in photochemistry, at the heart of which is the breaking and formation of chemical bonds. Such progress has been greatly facilitated by the development of accurate quantum-mechanical simulation method, which, however, does not necessarily accompany clear dynamical scenarios and is rather often a black box, other than being computationally heavy. Here, we develop a wave-packet surface propagation (WASP) approach to describe the molecular bond-breaking dynamics from a hybrid quantum-classical perspective. Via the introduction of quantum elements including state transitions and phase accumulations to the Newtonian propagation of the nuclear wave-packet, the WASP approach naturally comes with intuitive physical scenarios and accuracies. It is carefully benchmarked with the H2+ molecule and is shown to be capable of precisely reproducing experimental observations. The WASP method is promising for the intuitive visualization of strong-field molecular dynamics and is straightforwardly extensible toward complex molecules.Comment: 24 pages, 4 figure

Popularization and application of the capillary foam deliquification technology in horizontal wells with low pressures and low liquid flow rates: A case study on middle–shallow gas reservoirs in the Western Sichuan depression

The application effect of the foam deliquification technology in horizontal wells is poor because the foaming agent fails to reach the target location. In view of this, the adaptability of the capillary foam deliquification technology in the Western Sichuan Gas Field in the Sichuan Basin was analyzed from the aspects of gas flow rate, liquid flow rate and casing program of gas wells, and the design of injection depth and the selection of capillary size, tool string parameters (the maximum length and the minimum counterweight) and foam deliquification parameters (foaming agent type selection, ground injection concentration and rate) were optimized. Then, a standardized capillary operation process was developed. Finally, a field application test was carried out. And the following research results were obtained. First, the capillary foam deliquification technology has a popularization potential in the horizontal wells of middle–shallow depth, low pressure and low liquid flow rate, but it is not suitable for the wells with too low gas flow rate, too high liquid flow rate or too high condensate content. Second, the well deviation angle at the injection depth shall be between 70° and 80°, the selection of capillary size shall satisfy the requirement for tension strength by the well depth, the foam deliquification parameters shall be optimized based on the specific well conditions and the liquid loading characteristics, and the capillary operation shall comply with the standardized process. Third, by the end of July 2017, the capillary foam deliquification technology had been successfully applied in 9 horizontal wells in the Western Sichuan Gas Field with a cumulative gas increment of 295 × 104 m3. Fourth, 4 supporting technologies of the capillary foam deliquification are formed, including capillary sticking prevention, integrated agent injection and pressure measurement, combined cleaning and deliquification and capillary wellhead suspension. In conclusion, the capillary foam deliquification technology provides a technological support for the deliquification and production stabilization of horizontal wells with middle–shallow depth, low pressures and low liquid flow rates in the Western Sichuan Depression, and also provides technological reference for the deliquification of horizontal wells in the similar type of gas reservoirs. Keywords: Horizontal well, Capillary, Deliquification, Bottom-hole cleaning, Pressure measurement, Sticking prevention, Suspension, Sichuan basin, Western sichuan gas fiel

Association between Metformin Use and Coronary Artery Calcification in Type 2 Diabetic Patients

Objectives. Type 2 diabetes mellitus (T2DM) is associated with coronary artery calcification (CAC) which is an independent risk factor for cardiovascular events. Metformin is the first-line antidiabetic medication. We aimed to investigate the association between metformin use and CAC. Methods. We included 369 patients with T2DM in this cross-sectional study. CAC scores, clinical characteristics, and antidiabetic drug prescription information of the patients were acquired. Baseline parameters were balanced for metformin and nonmetformin users using the propensity score matching (PSM) strategy. Results. Among the 369 subjects who met our inclusion criteria, 288 subjects were included for further analysis after PSM. Metformin prescription rather than other antidiabetic medications was related to lower CAC scores (OR [95% CI] = 0.55 [0.34–0.90]; P=0.018). Further multivariable logistic regression analysis demonstrated that metformin was negatively associated with CAC severity (OR [95% CI] = 0.58 [0.34–0.99]; P=0.048), which was independent of age, BMI, eGFR, gender, cigarette smoking, duration of diabetes, hypertension, statin prescription, and number of nonmetformin antidiabetic agents. A subgroup analysis revealed a significant association between metformin and CAC scores in smokers (OR [95% CI] = 0.38 [0.16–0.93]; P=0.035), but the association was not observed in never-smokers (OR [95% CI] = 0.72 [0.34–1.51]; P=0.383). Conclusions. Metformin usage was independently associated with lower CAC scores in T2DM patients. The negative correlation between CAC scores and metformin was most prominent in patients with a history of cigarette smoking

Ultrafast photoinduced C-H bond formation from two small inorganic molecules

Abstract The formation of carbon-hydrogen (C-H) bonds via the reaction of small inorganic molecules is of great significance for understanding the fundamental transition from inorganic to organic matter, and thus the origin of life. Yet, the detailed mechanism of the C-H bond formation, particularly the time scale and molecular-level control of the dynamics, remain elusive. Here, we investigate the light-induced bimolecular reaction starting from a van der Waals molecular dimer composed of two small inorganic molecules, H2 and CO. Employing reaction microscopy driven by a tailored two-color light field, we identify the pathways leading to C-H photobonding thereby producing HCO+ ions, and achieve coherent control over the reaction dynamics. Using a femtosecond pump-probe scheme, we capture the ultrafast formation time, i.e., 198 ± 16 femtoseconds. The real-time visualization and coherent control of the dynamics contribute to a deeper understanding of the most fundamental bimolecular reactions responsible for C–H bond formation, thus contributing to elucidate the emergence of organic components in the universe

Preparation, microstructure and degradation performance of biomedical magnesium alloy fine wires

With the development of new biodegradable Mg alloy implant devices, the potential applications of biomedical Mg alloy fine wires are realized and explored gradually. In this study, we prepared three kinds of Mg alloy fine wires containing 4 wt% RE(Gd/Y/Nd) and 0.4 wt% Zn with the diameter less than 0.4 μm through casting, hot extruding and multi-pass cold drawing combined with intermediated annealing process. Their microstructures, mechanical and degradation properties were investigated. In comparison with the corresponding as-extruded alloy, the final fine wire has significantly refined grain with an average size of 3–4 μm, and meanwhile shows higher yield strength but lower ductility at room temperature. The degradation tests results and surface morphologies observations indicate that Mg–4Gd–0.4Zn and Mg–4Nd–0.4Zn fine wires have similar good corrosion resistance and the uniform corrosion behavior in SBF solution. By contrast, Mg–4Y–0.4Zn fine wire shows a poor corrosion resistance and the pitting corrosion behavior