RESUMEN
A mid-infrared quantum cascade laser (Mid-IR QCL) coupled with a Single Pass Cell and a Multi Pass Cell, was utilized to measure ammonia (NH3) absorption spectroscopic parameters and determine NH3 impurities toward three emerging applications. We for the first time measured the pressure broadening coefficients perturbed by Air, O2, N2, He, CO2, CH4, and H2 and the line intensities of six NH3 transition lines near 1084.6 cm-1. The measured NH3-He, NH3-Air, and NH3-CO2 broadening coefficients align with HITRAN database, while NH3-H2 coefficients exhibit a maximum discrepancy of 46 %. Deviations between the measured line intensities and HITRAN database are minimal. Nevertheless, the uncertainties of line intensities have been significantly reduced from 20 % in HITRAN to below 3 %. The newly measured line parameters are utilized to address NH3 impurity requirements outlined in CCUS (ISO 27913:2016), Biomethane (EN 16723:2016), and H2 (ISO 14687:2019) standards. Based on the concept of optical gas standard (OGS), the NH3 impurity detection requirements in all three standards have been fulfilled with an uncertainty of 1.35 %. The precision of the NH3-OGS is 800 part per trillion (ppt) with an integration time of 100 s. The repeatability of the NH3-OGS is 130 ppt for a continuous measurement time of 48 min. Notably, the NH3-OGS effectively addresses the highly nonlinear adsorption-desorption dynamics, underscoring the potential of OGS as a calibration-free and SI-traceable metrological gas analysis instrument.
RESUMEN
Ammonia (NH3) is a promising fuel, because it is carbon-free and easier to store and transport than hydrogen (H2). However, an ignition enhancer such as H2 might be needed for technical applications, because of the rather poor ignition properties of NH3. The combustion of pure NH3 and H2 has been explored widely. However, for mixtures of both gases, mostly only global parameters such as ignition delay times or flame speeds were reported. Studies with extensive experimental species profiles are scarce. Therefore, we experimentally investigated the interactions in the oxidation of different NH3/H2 mixtures in the temperature range of 750-1173 K at 0.97 bar in a plug-flow reactor (PFR), as well as in the temperature range of 1615-2358 K with an average pressure of 3.16 bar in a shock tube. In the PFR, temperature-dependent mole fraction profiles of the main species were obtained via electron ionization molecular-beam mass spectrometry (EI-MBMS). Additionally, for the first time, tunable diode laser absorption spectroscopy (TDLAS) with a scanned-wavelength method was adapted to the PFR for the quantification of nitric oxide (NO). In the shock tube, time-resolved NO profiles were also measured by TDLAS using a fixed-wavelength approach. The experimental results both in PFR and shock tube reveal the reactivity enhancement by H2 on ammonia oxidation. The extensive sets of results were compared with predictions by four NH3-related reaction mechanisms. None of the mechanisms can well predict all experimental results, but the Stagni et al. [React. Chem. Eng. 2020, 5, 696-711] and Zhu et al. [Combust. Flame 2022, 246, 115389] mechanisms perform best for the PFR and shock tube conditions, respectively. Exploratory kinetic analysis was conducted to identify the effect of H2 addition on ammonia oxidation and NO formation, as well as sensitive reactions in different temperature regimes. The results presented in this study can provide valuable information for further model development and highlight relevant properties of H2-assisted NH3 combustion.
RESUMEN
OBJECTIVE: To investigate whether the variants A(-6)G and A(-20)C of angiotensinogen (AGT) gene are involved in the pathogenesis of essential hypertension in Kazakans. METHODS: T his case control study recruited 125 subjects with hypertension and 74 normotensive subjects from Kazakans of Xinjiang. Genomic DNA from leukocytes was analyzed for genetic variants A(-6)G and A(-20)C in 5' upstream core promoter of AGT gene by polymerase chain reaction (PCR), single strand conformation polymorphism (SSCP), restriction fragment length polymorphism (RFLP) and automatic sequencing. RESULTS: (1)There were only A(-6)G and A(-20)C variants in the -164 to +73 region of Kazakans' AGT gene. (2) The distributions of genotypes AA, AG, GG at locus -6 of AGT gene showed significant difference between the hypertensive group (0.39, 0.45, 0.16) and the normotensive group (0.49, 0.49, 0.02; Chi2=8.56, P=0.014). There were evident differences in the frequencies of the -6A and the -6G allele of the two groups (0.62, 0.38 and 0.73, 0.27; Chi2=5.35, P=0.021). (3) No significant difference was observed in the distribution of genotypes AA, AC, CC at locus -20 of AGT gene between the hypertensive group (0.69, 0.26, 0.05) and the normotensive group (0.65, 0.32, 0.03; Chi2=2.42, P=0.30). There was no distinct difference in the frequencies of the -20A allele and the -20C allele of the two groups (0.82, 0.18 and 0.82, 0.18; Chi2=0, P=0.99). (4) No significant difference was found at the levels of systolic and diastolic blood pressure between the groups corresponding to genotypes at the loci -6 and -20 of AGT gene. CONCLUSION: The results suggest that the polymorphism of A(-6)G in 5' upstream core promoter of the AGT gene may be involved in the pathogenesis of essential hypertension in Kazakans, while the A(-20)C variant may not play an important role in the etiology of essential hypertension in Kazakans.