The application of myocardial contrast echocardiography in assessing microcirculation perfusion in patients with acute myocardial infarction after PCI.

BACKGROUND: To evaluate the myocardial microcirculation perfusion of patients with acute ST-segment elevation myocardial infarction (STEMI) with a different index of microcirculatory resistance (IMR) after percutaneous coronary intervention (PCI) by myocardial contrast echocardiography (MCE) and analyse the value of MCE in predicting myocardial perfusion after PCI. METHODS: Fifty-six patients with acute STEMI who underwent an emergency PCI were selected from October 2018 to October 2019 in our hospital. According to the IMR values measured during PCI treatment, the patients were divided into three groups. Traditional ultrasound and MCE were performed one week after PCI. The left ventricular ejection fraction (LVEF), ventricular wall motion score index (WMSI), A value, ß value and A × ß value (which refers to the patient's myocardial blood flow) were measured. The receiver operating characteristic curve was drawn to evaluate the effectiveness of the MCE parameters in the diagnosis of myocardial microcirculation perfusion disorders. RESULTS: The results showed that there was no significant difference in the LVEF among the groups. The WMSI in Group 3 was statistically different from that in Groups 1 and 2 (P < 0.05), but there was no statistically significant difference in the WMSI between Groups 1 and 2. Among the three groups, the A value, ß value and A × ß value were significantly different (P < 0.05). According to Spearman's correlation analysis, the MCE quantitative parameters (i.e. the A value, ß value and A × ß value) were negatively correlated with the IMR value (r = -0.523, -0.471, -0.577, P < 0.01). CONCLUSIONS: The A value, ß value and A × ß value were negatively correlated with the IMR value. Furthermore, MCE could be used to observe the myocardial perfusion in patients with acute STEMI after PCI and may be one of the indicators used to accurately evaluate myocardial microcirculation.

[Laboratory evaluation of remediation of nitrobenzene contaminated aquifer by using groundwater circulation well].

A two-dimension simulated sand box was set up to investigate the influencing factors, such as the initial groundwater level, aeration rate and the initial groundwater rate, that affect groundwater circulation well (GCW) by determining the intensity of groundwater circulation which was characterized by the variation of groundwater level before and after aeration. The optimal operating parameters were used to remediate nitrobenzene contaminated aquifer. The results demonstrated that: GCW could be well operated under the conditions of 45 cm groundwater level, 0.7 m3 · h(-1) aeration rate. The effects of groundwater velocity less than 1.0 m · d(-1) could be ignored. The lateral mobility rate of nitrobenzene was faster than that of longitudinal. The average concentration of nitrobenzene was 246.97 mg · L(-1) on day 50 of leakage. During the remediation of circulation well, an efficient organics remediation region was gradually formed around the circulation well. The organics in this region was removed preferentially, and the concentration decreased continuously. Besides the efficient remediation region, there was a transient region, where the concentration of organics was influenced by the combined effects of adsorption/desorption and migration potential of organics. During the whole remediation process, the concentration of nitrobenzene went through three stages described as rapid removal, slow removal. After 14h aeration, the nitrobenzene average concentration was reduced to 71.19 mg L(-1). The residual nitrobenzene was distributed in regions far away from GCW. Therefore, nitrobenzene contaminated aquifer could be well remediated by GCW, and there were optimal operation conditions and appropriate remediation time which guaranteed the best remediation effect.

Remediation of nonaqueous phase liquid polluted sites using surfactant-enhanced air sparging and soil vapor extraction.

A two-dimensional laboratory sand tank was installed to study the remediation efficiency of surfactant-enhanced air sparging (-SEAS) coupled with soil vapor extraction (SVE) in nonaqueous phase liquid (NAPL) polluted sites. During initial stages of remediation, it was more reasonable to use conventional air sparging coupled with SVE. When most free NAPLs were removed and contaminant removal rate was maintained at a relatively low level, surfactant was added to the groundwater. During enhanced remediation, lower interfacial tension caused residual NAPLs in the porous media to slightly migrate, making the downstream contaminant concentration somewhat higher. The polluted area, however, was not more enlarged than before. The decrease in surface tension resulted in increased air saturation in the groundwater and the extent of the air influence zone. After 310 hours, 78.7% of the initial chlorobenzene mass had volatilized, 3.3% had migrated out of the sand profile, 17.5% was in the vadose zone, and 0.5% remained in the groundwater, thus revealing that SEAS/SVE can effectively improve the remediation of NAPL polluted sites.

Study on mechanisms and effect of surfactant-enhanced air sparging.

In an attempt to enhance the effectiveness of air sparging, two sets of experiments were designed to investigate the mechanisms and effect of surfactant-enhanced air sparging (SEAS). The first set was performed at different surface tensions and with different kinds of surfactants (sodium dodecyl benzene sulfonate and Tween-80 [Uniqema Americas LLC, Wilmington, Delaware]), which were added into the contaminated aquifer of different media (particle distribution size = 0.25 to 0.5 mm and 5 to 10 mm). The results indicated that the air saturation in the aquifer increased rapidly at an early stage, then the increase of air saturation slowed down with the increase of airflow rate. The air saturation of medium sand increased with the decrease in water surface tension, and maximum air saturation was achieved at a surface tension of approximately 5 x 10(-2) N/m (50 dyn/cm), which was considered to be the optimum surface tension for air sparging enhancement in the medium sand aquifer. The increase of air saturation in gravel was the result of the increase of foamability and foam stability. The second group of experiments is about the removal of chlorobenzene from the medium sand aquifer. The experiments indicated that chlorobenzene removal by SEAS was more complete and efficient than that of conventional air sparging technology. However, the increase of removal rate and the decrease of lingering concentration by SEAS was not significant, with a further decrease in the surface tension when the surface tension dropped to 5.04 X 10(-2) N/m (50.4 dyn/cm).

Study on influencing factors on removal of chlorobenzene from unsaturated zone by soil vapor extraction.

This paper deals with the influencing factors on removal of chlorobenzene from unsaturated soils by soil vapor extraction (SVE) method. A series of one-dimensional column experiments were conducted to study the influencing factors for SVE method, the factors included extracted vapor flow rate, soil grain size, extraction mode, soil organic matter content and water content. The results indicated that: (1) the increase of vapor flow rate led to higher contaminant removal efficiency, but the increment of removal was not significant at higher flow rate levels; (2) soil grain sizes had a great impact on chlorobenzene removal efficiency, the coarser the sand, the higher the removal rate; (3) pulsed vapor extraction and continuous vapor extraction almost had the same contaminant removal effects in the sand column; (4) the higher organic content in the soil could decrease the removal efficiency; (5) water content in the soil had different impact on the contaminant removal efficiency which related with the organic content in the soil.