Simulation Investigation on the Structure and Its Influence on the Impinging Pressure of the Carbon Dioxide Jet

An improved understanding of the mechanisms of SC-CO₂ jet drilling technology is important for the application of this new technology. The flow field structure and dynamic fluctuation of SC-CO₂ jets are the key factors affecting the jet erosion performance. To improve the erosion performance of the SC-CO₂ jet, it is necessary to study the relationship between the different flow fields of the jet. In this study, a numerical simulation model for SC-CO₂ jet drilling technology is established. Based on the modified real-gas model, the pressure distribution and flow field characteristics of the SC-CO₂ jet were obtained by the simulation investigation, and the reliability of the model was verified. The results show that the flow field structure of a supercritical CO₂ jet has typical compressible flow field characteristics. As the jet is fully expanded, its pressure fluctuation is slight and less affected by the distance between the nozzle and the wall. When the jet is in the state of under-expansion, the flow field structure characteristics have a significant impact on the pressure distribution and peak pressure. At the same time, when the distance is large, when nozzle pressure ratio = 5, the pressure ratio has a more significant impact on the flow field and the pressure peak and distribution. The pressure distribution of different flow fields should be fully considered in the application.

Oxidation-absorption process for simultaneous removal of NOx and SO2 over Fe/Al2O3@SiO2 using vaporized H2O2

3% Fe/Al₂O₃ and 3% Fe/Al₂O₃@SiO₂ were prepared to investigate the performance in simultaneous removal of NO_x and SO₂ using vaporized H₂O₂. Certain paraments were changed to explore the activity of catalysts, including temperature, H₂O₂ concentration, GHSV and coexistence gases component. A 24-h durability test was conducted on 3% Fe/Al₂O₃@SiO₂. Moreover, a series of characterizations were employed to analyze the physical and chemical properties of catalysts, including XRD, BET, SEM, TEM, FTIR and XPS. Compared with 3% Fe/Al₂O₃, 3% Fe/Al₂O₃@SiO₂ exhibited more excellent catalytic activity, which could achieve the peak removal efficiency of 100% for SO₂ and 93.76% for NO_x. Moreover, 3% Fe/Al₂O₃@SiO₂ kept stable simultaneous removal efficiency in a 24-h test. The characterization results indicated that the BET area was greatly improved and the core-shell structure was synthesized with the formation of more micropores and mesopores by the coating of SiO₂, which could improve the activity of catalyst at high temperature and high SO₂ concentration. Besides, the mechanism of SO₂ molecules on simultaneous removal was investigated. On one hand, a part of H₂O₂ was consumed by SO₂ molecules without catalyst, which resulted in the drop of NO_x removal by the decrease of oxidants. The main products were sulfites and bisulfites, which were broken down into SO₂ over the catalyst. On the other hand, the presence of SO₂ was beneficial for NO_x removal by increasing oxygen vacancies on the catalyst surface and facilitating the absorption of NO₂ by NaOH solution.

Systematic evaluation of COVID-19 related Internet health rumors during the breaking out period of COVID-19 in China

Background: To adapt the scientific evaluation tool for the confusion evaluation of health rumors and to test this tool to the confusion evaluation of coronavirus disease 2019 (COVID-19)-related health rumors on Chinese online platforms during the outbreak period of COVID-19in China. Methods: The design of our study was systematic evaluation of COVID-19-related health rumors. Retrieved from 7 rumor-repellent platforms, rumors about COVID-19 were collected during the publication from December 1, 2019, to February 6, 2020, and their origins were traced. Researchers evaluated rumors using the confusion evaluation tool in 6 dimensions(creators, evidence selection, evidence evaluation, evidence application, backing and publication platform, conflict of interest). Items were scored using a seven-point Likert scale. The scores were converted into percentages, and the median of rumors from different sources was compared with rank-sum test. Results: Our research included 127 rumors. Scores were converted to percentages, median and interquartile range are used to describe the data. The median score: creators 25.00%(interquartile range, IQR, 16.67-37.50%), evidence selection 27.78% (IQR, 13.89-44.44%),evidence evaluation 33.33% (IQR, 25.00-45.83%), evidence application 36.11% (IQR, 22.22-47.22%), backing and publication platform 8.33% (IQR, 4.17-20.83%), conflict of interest75.00% (IQR, 50.00-83.33%). Almost 40% rumors came from WeChat and the rumors with the lowest scores were concentrated on the WeChat platform. The rumors about prevention methods have relatively lower scores. Conclusion: Most rumors included were not highly confusing for evaluators of this project.WeChat is the "worst-hit area" of COVID-19 related health rumors. More than half rumors focus on the description of prevention methods, which reflects the panic, anxiety and blind conformity of the public under public health emergencies.

Oxidation of NO x Using Hydrogen Peroxide Vapor over Mo/TiO2

xMo/TiO₂ catalysts (x = 1, 2, 3, and 4%) were prepared using the coprecipitation method in the present study. The coprecipitation method was used in the thermal catalytic decomposition of H₂O₂ steam to treat NO _x at a low temperature range (80-160 °C). Several characterization techniques have been employed, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller measurements, transmission electron microscopy (TEM), scanning electron microscopy and energy-dispersive X-ray spectrometry (SEM-EDXS), and Fourier transform infrared spectroscopy. The activity tests showed that the incorporation of molybdenum into TiO₂ led to a significant increase in the catalytic oxidation of NO, and under the condition of H₂O₂/NO = 6:1 (molar ratio), the NO _x removal rate of 2% Mo/TiO₂ is the highest, reaching 92.56%. XRD, TEM, and SEM-EDXS analyses showed that Mo was well dispersed on the surface of an anatase-phase TiO₂. XPS analysis indicated that Mo mixed with slag mainly existed in the form of Mo⁶⁺. Moreover, in comparison with the mostly reported SCO catalysts, used for the elimination of NO, the prepared Mo/TiO₂ catalyst showed excellent stability and sulfur resistance.

Experiment and simulation study of the effect of ethanol and compound additives on the urea-based selective non-catalytic reduction process under moderate temperature conditions

An experiment and simulation study of the effect of using liquid additives on the selective non-catalytic reduction (SNCR) process is presented, providing a novel way for plants reducing NO_X emissions. An experimental study is conducted in an entrained flow reactor, and CHEMKIN is applied for simulation study. Ethanol additive can effectively shift the temperature window of the NO_XOUT process to a lower range and the NO_XOUT efficiency ranges from 29 to 56% at 700-800°C. Furthermore, ethanol additive has a significant inhibitory effect on ammonia slip. Na₂SO₄ and C₂H₅OH can be combined into a compound additive, which has a synergistic effect on NO reduction. The addition of methanol can greatly promote denitrification efficiency from 650°C to 725°C, indicating the potential of compound additives in NO reduction. The HNCO + OH = H₂O + NCO pathway is also proven to be enhanced for ethanol decomposition, thereby providing OH•, which is active in NO reduction. Finally, the reaction routes for ethanol on the urea-based SNCR process at the proper temperature are proposed.

[Cell infiltration in nasal polyps and it's pathological significance]

OBJECTIVE

To study the relation between inflammatory cells infiltration in nasal polyp tissues and it's pathogenesis.

METHOD

Nasal mucosa from 10 normal individual and 4 patients of nasal polyps were studied with immunohistochemical technique and histopathologic examination.

RESULT

The number of eosinophils, CD68 positive cells and monocytes was significantly higher (P < 0.05) in nasal polyps tissues than in the normal controls.

CONCLUSION

Infiltration of inflammatory effector cells such as eosinphils and chronic inflammatory changes of the nasal mucosa might play a role in nasal polyps sprouting.

Capillary electrophoretic separation of cationic porphyrins

Cationic porphyrins have a wide variety of uses including those as nucleic acid binding and cleaving agents, as potential pharmacological agents, as electron donor/acceptors in intramolecular electron transfer processes and as analytical reagents. Herein, we report the separation of cationic porphyrins by capillary electrophoresis on fused silica in phosphate buffer at pH 2-5. The porphyrins studied in this work were synthesized from alkylation of the parent tetrapyridylporphyrin (TPyP) to give various pyridinium porphyrins. For example, methylation of TPyP gives a mixture of the mono-, cis-di-, trans-di-, tri- and tetramethylated porphyrins [e.g., 5,10,15,20-tetrakis(N-methyl-4-pyridiniumyl)-21H,23H-p orphyrin, TMPyP(4)]. Capillary electrophoresis on a synthetic mixture showed separation of four of these compounds. Mixtures after alkylation with iodopropionic acid and bromopropylamine were also separated. The cis-di- and trimethylated TMPyP derivatives were separated on a small preparative scale by centrifugal partition chromatography. Capillary electrophoresis was also used to separate metallo TMPyP(4) complexes including those of cobalt, copper, iron, manganese, palladium, tin, vanadium and zinc. The conformational isomers (atropisomers) of 5,10,15,20-tetrakis(N-methyl-2-pyridiniumyl)-21H,23H-p orphyrin, TMPyP(2), were also separated. Net charge, molecular mass and molecular shape all contribute to the differential retention of cationic porphyrins under capillary electrophoresis conditions. Additional factors affecting the separations, including aggregation and protonation of the porphyrins, were probed by evaluating the separation of TMPyP(4) and its butyl and octyl analogs as a function of solution conditions. Cationic porphyrins are difficult to separate using traditional chromatographic methods; capillary electrophoresis and centrifugal partition chromatography provide excellent new techniques for separation of this class of compounds.