Study on strength characteristics and thickening characteristics of classified-fine cemented backfill in gold mine.

For some new mines, the utilization rate of tailings is not satisfactory when using unclassified tailings as backfill aggregate for cemented backfill. At the same time, with the progress of mineral processing technology, the tailings discharged by the concentrator gradually become finer. Therefore, cemented filling with fine-grained tailings as aggregate will become the development direction of filling technology in the future. In this paper, the feasibility of fine particle tailings backfill is studied by taking the particle tailings of-200 mesh as aggregate in Shaling gold mine. The calculation shows that the utilization rate of tailings is increased from 45.1% to 90.3% by using-200 mesh tailings as filling aggregate. The response surface central composite design method (RSM-CCD) was used to study the strength of backfill with alkali-activated cementitious material as binder by taking the mass concentration of backfill slurry and sand-binder ratio as input factors. The results show that the 28-day strength of the backfill with graded fine-grained tailings as filling aggregate can reach 5.41 MPa when the sand-binder ratio is 4, which can fully meet the needs of the mine for the strength of the backfill. The thickening test of-200 mesh fine particle tailings was carried out by static limit concentration test and dynamic thickening test. In the case of adding 35 g/t BASF 6920 non-ionic flocculant, the concentration of 64.74% tail mortar can reach 67.71% after 2 h of static thickening, and the concentration can reach 69.62% after 2 h of static thickening. The feeding speed of thickener should be controlled between 0.4 and 0.59 t/(m2 h). In this case, the underflow concentration of thickener is relatively high, which is 64.92-65.78%, and the solid content of overflow water is less than 164 ppm. The conventional full tailings thickening process was improved by using the design of high-efficiency deep cone thickener and vertical sand silo. The feasibility of fine-grained tailings as filling aggregate was demonstrated by combining the filling ratio test of fine-grained tailings, the data of thickening test and the improved thickening process. The research results can provide reference for other mines to use fine-grained tailings as filling aggregate to design filling system.

[Protective effect and mechanism of curcumin on aorta in rats with metabolic syndrome].

To investigate the protective effect and mechanism of curcumin on aorta in rats with metabolic syndrome,72 SD rats were randomly divided into blank control group,model control group,positive control group,curcumin low,middle and high dose groups.The rat model of metabolic syndrome was established in all groups except the blank control group. After the intervention by curcumin,the blood pressure,blood lipid,blood glucose,serum insulin and insulin sensitivity index were measured. The contents of serum leptin(LP),adiponectin(ADP) and tumor necrosis factor-α(TNF-α) in rat aorta were detected by enzyme-linked immunosorbent assay(ELISA),and the pathological changes of rat thoracic aorta were observed by HE staining and electron microscope scanning. Western blot assay was used to detect the expression of inducible nitric oxide synthase(i NOS) and endothelial nitric oxide synthase(e NOS) in rats. The results showed that the blood lipid level,fasting blood glucose,fasting insulin,insulin sensitivity index,systolic blood pressure,LP,TNF-α and intima/media thickness ratio in the model control group were significantly higher than those in the blank control group. As compared with the model control group,the levels of blood lipids,fasting blood glucose,fasting insulin,insulin sensitivity index,systolic blood pressure,LP,TNF-α and intima/media thickness ratio were significantly decreased in positive control group,low,middle and high dose curcumin groups. The difference was statistically significant. The results of HE staining showed that the intima of the thoracic aorta in the model group was significantly thickened; the endothelial cell membrane was wrinkled and the organelle was ruptured. The intima of the thoracic aorta in the positive control group was slightly thickened and the structure of endothelial cells was intact,with no foam cells and no abnormality in the adventitia. There was no significant thickening of the thoracic aorta in the low,middle and high dose curcumin groups,and the endothelial cells were still intact. The results of Western blot assay showed that the expression levels of i NOS and e NOS were decreased significantly in the model group,while the expression levels of i NOS and e NOS were increased significantly in the positive control group and curcumin groups. The results indicated that curcumin had a certain protective effect on the aorta of rats with metabolic syndrome and improves the aortic endothelial dysfunction,and its mechanism may be related to the fact that curcumin could reduce the production of oxygen free radicals and up-regulate the expression of i NOS and e NOS in aorta.

[Efficacy and safety of tirofiban use after successful percutaneous coronary intervention for patients with moderate to high risk non-ST segment elevation acute coronary syndromes].

OBJECTIVE: To evaluate the efficacy and safety of tirofiban use immediately after successful percutaneous coronary intervention (PCI) in patients with moderate to high risk non-ST segment elevation acute coronary syndromes (NSTE-ACS). METHODS: NSTE-ACS patients undergoing successful PCI (n = 246) were randomized by the envelope method to tirofiban group (n = 122, 10 µg/kg bolus within 3 min followed by 0.10-0.15 µg×kg(-1)×min(-1) for 36 h i.v.) or control group (n = 124, saline i.v. for 36 h). The primary efficacy composite end point was death, myocardial infarction, target vascular revascularization or ischemic stroke at 30 days. The second end point was the occurrence of composite end point at 7 days or 6 months. Key safety end points were bleeding and thrombocytopenia 3 days after PCI. RESULTS: Baseline characteristics were well-balanced between the two groups (P > 0.05). The primary end point occurred in 0.9% (1/117) patients in the tirofiban group and 3.3% (4/123) patients of those in the control group (P = 0.40). There was no significant difference in the composite end point at 7 days [0.8% (1/122) vs. 3.2% (4/124), P = 0.38] between the groups, however, there was a trend towards lower composite efficacy end points at 6 months in tirofiban group compared to control group [0.9% (1/117) vs. 5.9% (7/118), P = 0.07]. The probability of survival free of composite end point was significantly higher in the tirofiban group than that in the control group (99.2% vs. 94.2%, log-rank test, P = 0.03). There was no GUSTO severe or moderate bleeding or severe thrombocytopenia within 3 days post-PCI. There was no significant difference in mild bleeding [13.1% (16/122) vs. 7.3% (9/124), P = 0.13] or mild thrombocytopenia [0.8% (1/122) vs. 0.8% (1/124), P = 1.00] between the groups. CONCLUSION: Tirofiban use after successful PCI can improve 6-month event-free survival without increasing the risk of bleeding for patients with moderate to high risk NSTE-ACS.

[Effects of cardiac resynchronization therapy in patients with advanced congestive heart failure evaluated by real-time 3-dimensional echocardiography].

OBJECTIVE: To quantitatively assess the effects of cardiac resynchronization therapy (CRT) in patients with advanced congestive heart failure by real-time 3-dimensional(3D) echocardiography (RT-3DE). METHODS: Eighteen patients with advanced congestive heart failure underwent CRT with New York Heart association(NYHA) class III and IV and wide QRS complex (>120 ms) were included (17 dilated cardiomyopathy and 1 ischemic cardiomyopathy). Before CRT and 8 months after CRT, the clinical and RT-3DE parameters and outcome were analyzed. RESULTS: The biventricular pacemaker was successfully implanted in 17 patients (94.4%). Compared with before CRT, NYHA class of patients decreased by 1.5 class (P < 0.01), left ventricular ejection fraction increased by 25% (P < 0.01), left ventricular end systolic volume decreased by 38% (P < 0.01), left ventricular systolic dyssynchrony index (SDI) improved significantly (14.2% before CRT vs. 9.8% after CRT, P < 0.01 ) post CRT. Change in SDI and change in LVEF was positively correlated (r = 0.62, P < 0.01) . The procedure complications and outcome during and after CRT included coronary sinus dissection (n = 1), left ventricular lead dislodgement (n = 1), phrenic nerve stimulation (n = 1), sudden cardiac death (n = 1). Three non-response patients were complicated with atrial fibrillation, nonspecific intraventricular block and dilated cardiomyopathy with postero-lateral scar tissue. CONCLUSIONS: CRT could improve the cardiac function, correct the mechanical desynchronization and reverse left ventricular remodeling in patients with congestive heart failure, and SDI quantification by RT-3DE could predict increase of LVEF after CRT, however, there were complications related to the implantation procedure and possibilities of non-response.

[Angiotensin(1-7) attenuates left ventricular dysfunction and myocardial apoptosis on rat model of adriamycin-induced dilated cardiomyopathy].

OBJECTIVE: To investigate the effect of Angiotensin(1-7) [Ang(1-7)] on left ventricular dysfunction and myocardial apoptosis on rat model of adriamycin-induced dilated cardiomyopathy (ADR-DCM). METHODS: Weight-matched adult male Wistar rats were randomly divided into 3 groups: (1) the ADR-DCM group (n = 25), in which 2.5 mg/kg of ADR was weekly intravenously injected for 10 weeks. (2) Ang(1-7) group (n = 25), in which ADR rats were simultaneously treated with angiotensin-(1-7) (24 µg×kg(-1)×h(-1), ip.) for 12 weeks. (3) normal control group (n = 10). Hemodynamics and echocardiography examination were performed at 12 weeks. The malondialdehyde (MDA) was measured by TBA methods. The plasma concentration of AngII was determined by immunoradiometric assay. The pathological change was analyzed by histological hematoxylin-eosin staining. Myocardial apoptosis was assessed by TUNEL method. The protein expression of pro-apoptotic protein caspase-3, Bax and anti-apoptotic protein Bcl-xl in cardiomyocytes were detected by Western blot. RESULTS: Mortality was significantly lower in Ang(1-7) group than in ADR-DCM group (16% vs. 40%, P < 0.01). Compared to the control group, left ventricular end-diastolic diameter (LVEDD), left ventricular end systolic diameter (LVESD) and left ventricular end-diastolic pressure (LVEDP) were significantly increased in ADR-DCM group (all P < 0.01) while fractional shorting (FS), +dp/dtmax and -dp/dtmax were significantly reduced in ADR-DCM group (all P < 0.01). LVEDD, LVESD and LVEDP were significantly reduced while FS, +dp/dtmax and -dp/dtmax were significantly higher in Ang(1-7) group compared to the ADR-DCM group, but still higher than the control group (all P < 0.01). The concentrations of AngII and MDA were higher in the ADR-DCM group than in the control group (P < 0.01), which were significantly reduced by Ang(1-7) treatment (P < 0.01). The TUNEL-positive cells and apoptosis index, the expression of pro-apoptotic protein caspase-3 and Bax were significantly higher while the expression of anti-apoptotic protein Bcl-xl was significantly lower in the ADR-DCM group than in the control group (all P < 0.01) which could all be partially reversed by Ang(1-7) treatment (all P < 0.01). CONCLUSION: Ang(1-7) could significantly attenuate left ventricular dysfunction and myocardial apoptosis in this model by downregulating pro-apoptotic protein caspase-3 and Bax and upregulating anti-apoptotic protein Bcl-xl expression.