Occurrence state of fluoride in barite ore and the complexation leaching process.

Barite ore is typically associated with difficult-to-remove vein minerals, but commercial barite products require a high BaSO4 content. We investigated the occurrence state of fluoride in barite ore using various analytical techniques, which indicated that elemental fluorine in barite predominantly exists as fluorite. Fluoride was then leached from barite ore via complexation. The effects of HCl and AlCl3 concentrations, temperature, time, and liquid-solid ratio on the leaching rate were examined, and the leaching conditions were optimized using an orthogonal array method. The fluorine leaching rate approached 93.11% after stirring for 30 min at 90 °C and 300 rpm with 3 mol/L HCl, 0.4 mol/L AlCl3, a liquid-solid ratio of 10:1 mL/g, and an ore sample size of -75 µm + 48 µm. According to the leaching kinetics, the process conformed to the solid membrane diffusion control model at a high temperature and the joint chemical reaction-diffusion control model at a low temperature. The apparent activation energy was 56.88 kJ/mol. Furthermore, aluminum and fluorine coordination numbers increased with increasing Al3+/F- molar concentration ratios. Competing complexation reactions of Al3+, H+, and F- occurred at three levels. This complexation approach effectively leaches fluoride from barite, improves barite product quality, and reduces environmental pollution.

Determination of carbonate content in barite ore by headspace gas chromatography.

This paper reports a method for determining the carbonate content in barite ore using headspace gas chromatography. Based on the acidification reaction, the carbonate in the barite ore was converted to CO2 in a closed headspace vial. When the carbonate content was significant, the pressure caused changes in the CO2 and O2 signals and affected the measurement accuracy. It was found that carbonate content is proportional to the intensity ratio of the CO2 to O2 signals. Thus, the carbonate content in barite ore can be measured indirectly using a theoretical model. The results showed that the carbonate in 3 g of barite ore sample with a particle size of 74 µm could react completely with a hydrochloric acid solution (2 mol/L) at 65°C for 5 min. The method described herein had good precision (relative standard deviation < 4.14%) and accuracy (relative differences < 6.12%). Further, the limit of quantification was 0.07 mol/L. Owing to its simplicity and speed, this method can be used for the batch determination of carbonate content in barite ore.

Determination of barium sulfate in barite ore by phase conversion-partial pressure-corrected headspace gas chromatography.

Barium sulfate (BaSO4) content is used to evaluate the grade of barite ore. In the present study, we report a method to determine the BaSO4 content in barite ore by phase conversion-headspace gas chromatography with partial pressure correction. In this method, the ore sample is roasted with sodium carbonate and potassium carbonate after pretreatment with hydrochloric acid. The roasted product is subsequently placed in a closed headspace bottle to react with hydrochloric acid. The ratio of CO2 to O2 signals is detected by a thermal conductivity detector for gas chromatography. Finally, the BaSO4 content in barite ore is calculated using this ratio. The method demonstrates good precision (relative standard deviation < 0.84%) and accuracy (relative error < 3.40%), with the uncertainty at 95% confidence interval at approximately +/- 0.57%. Moreover, this approach is expected to be used for the batch testing of BaSO4 content in barite ores in industrial applications.

[Mechanisms for reversal of pulmonary hypertension by rapamycin in rats].

OBJECTIVE: To investigate the effects of rapamycin (RAP) on pulmonary hypertension (PH) in rats, and to provide new insights into medication selection for the clinical treatment of PH. METHODS: Fifty male Sprague-Dawley rats were randomly divided into blank control, PH model, solvent control, RAP 1, and RAP 2 groups. A rat model of PH was induced by left pneumonectomy (PE) and monocrotaline (MCT). At 5 days after PH model establishment, the solvent control group and the RAP 1 group received an intramuscular injection of solvent and RAP, respectively. At 35 days after PH model establishment, the RAP 2 group received an intramuscular injection of RAP. The mean pulmonary artery pressure (mPAP) and the right ventricle/left ventricle plus septum weight ratio (RV/LV+S) were measured in each group. Histopathological changes in the right lung were evaluated by hematoxylin-eosin (HE) staining. The relative expression of alpha-smooth muscle actin (α-SMA) and smooth muscle protein 22-alpha (SM22α) in each group was determined using real-time PCR. RESULTS: At 35 days after surgery, the PH model and the solvent control groups had significantly higher mPAP and RV/LV+S than the blank control group, while the RAP 1 and the RAP 2 groups had significantly lower mPAP than the solvent control group (P<0.05). The RV/LV+S in the RAP 1 group was significantly lower than that in the solvent control group (P<0.05); however, there was no significant difference in RV/LV+S between the RAP 2 and the solvent control groups (P>0.05). HE staining in the right lung showed the substantially thickened pulmonary artery wall and narrowed arterial lumen in the PH model and the solvent control groups compared with the blank control group. Different degrees of reversal of the pulmonary artery wall thickening were observed after RAP administration. The results of real-time PCR revealed that the relative expression of α-SMA and SM22α in the PH model and the solvent control groups was significantly lower than in the blank control group, while the relative expression of α-SMA and SM22α in the RAP 1 and the RAP 2 groups was significantly higher than in the solvent control group (P<0.05). CONCLUSIONS: RAP can reverse the increase in pulmonary artery pressure and the right ventricular hypertrophy probably by regulation of the phenotypic conversion of vascular smooth muscle cells.

[Relationship between Hes-1 and airway inflammation and remodeling in a rat model of asthma].

OBJECTIVE: To study the changes of Hes-1, the target gene of Notch signaling pathway, and its relationship with airway inflammation and remodeling in a rat model of asthma. METHODS: Forty-eight rats were randomly divided into an asthma group and a control group. The rats in the asthma group were sensitized and challenged by ovalbumin (OVA), and normal saline was used in the control group. Two groups were further divided into 3 subgroups according to time points after challenging, i.e. 4 weeks, 8 weeks and 12 weeks (n=8 rats each). Pathological changes of lungs were observed by light microscopy and the thickness of bronchial smooth muscle layer (Wam) was measured. The levels of IL-4 and INF-γ in rat serum and bronchoalveolar lavage fluids (BALF) were measured using ELISA. Expression levels of Hes-1 protein and mRNA were determined by immunohistochemistry and quantitative real-time PCR respectively. RESULTS: Together with the extension of challenging, the Wam of rats in the asthma group increased, a decrease of INF-γ level and an increase of IL-4 level in serum and BALF were also observed, and the differences were statistically significant compared with those in the corresponding control group (P<0.05). Hes-1 protein and mRNA levels also increased gradually after OVA challenging and were higher than those in the control group (P<0.05). The levels of Hes-1 protein and mRNA were positively correlated with Wam and IL-4 in serum and BALF, but were inversely correlated with INF-γ in serum and BALF (P<0.05). CONCLUSIONS: Levels of Hes-1 protein and mRNA increased, which were closely related with the levels of airway inflammatory factors and remodeling of airway smooth muscle. Hes-1 may play an important role in the pathogenesis of asthma.

[Effects of paclitaxel on proliferation and transition of phenotype in platelet-derived growth factor-BB-induced pulmonary vascular smooth muscle cells].

OBJECTIVE: To investigate the effects of paclitaxel on the phenotypic modulation induced by platelet-derived growth factor (PDGF-BB) in rat pulmonary vascular smooth muscle cells (PVSMC). METHODS: The proliferation of PVSMC isolated from SD rats cultured in vitro was induced by PDGF-BB and then intervened by different concentration of paclitaxel. MTT and [³H]-thymidine incorporation were used to detect the changes of cell proliferation. The expression level of alpha-smooth muscle-actin (SM-α-actin) and smooth muscle protein 22alpha (SM22α) were tested by Western blot. Confocal laser scanning microscopy was applied to observe the change of fluorescence intensity. RESULTS: Treatment with PDGF-BB for 24 hours results in a significant increase in [³H]-thymidine incorporation and marked change in phenotype and cytoskeleton, Paclitaxel inhibited the proliferation of PVSMC induced by PDGF-BB, the inhibition rate was 45.4%, 35.4%, 21.6% (P < 0.01) tested by[³H]-thymidine incorporation and 40.0%, 30.0%, 18.0% (P < 0.01) tested by MTT. Meanwhile, the paclitaxel promoted the expression level of SM-α-actin and SM22α. Fluorescence intensity of F-actin decreased significantly. CONCLUSION: Paclitaxel may play an important role in vascular remodeling by changing the phenotypes and cytoskeleton of VSMC stimulated by PDGF-BB.