BackgroundBreast cancer is the most common type of cancer in females. Aberrant expression of microRNA-21 (miR-21) has previously been reported in breast cancer tissue. The aim of this study was to investigate expression levels of serum miR-21 in breast cancer patients and evaluate its prognostic value in Chinese females.MethodsReal-time quantitative (RQ)-PCR was used to analyze miR-21 expression in archived serum, tumor tissue, and adjacent normal tissue from 549 participants (326 with breast cancer, 223 without breast cancer). We also analyzed associations between serum miR-21 expression and breast cancer subtypes and patient prognosis. Recurrence and survival were analyzed by using the multivariate Cox proportional hazards model.ResultsExpression of miR-21 was significantly higher in breast cancer tissues compared with normal adjacent breast tissues (P<0.001). The 2-ΔΔCt values for serum miR-21 in breast cancer patients versus healthy controls were 9.12±3.43 and 2.96±0.73, respectively. Multivariate Cox proportional hazards model suggested that serum miR-21 expression was an independent poor prognostic factor for both recurrence (hazard ratio [HR]= 2.942; 95% confidence interval [CI]=1.420-8.325; P=0.008) and disease-free survival (HR=2.732; 95% CI=1.038-7.273, P=0.003) in breast cancer.ConclusionsIncreased serum miR-21 expression level was correlated with poor prognosis of breast cancer patients, indicating that serum miR-21 may be a novel prognostic marker for recurrence and survival of breast cancer patients before resection.

Our findings suggest that the circulating miR-21 expression level can predict poor prognosis in patients with breast cancer.

The existence of pressure pulsations greatly increases the vibration and noise of pumps and harms their service life. In this paper, a casing treatment was employed to explore its impact on the pressure pulsations. A U-tube type groove was created at the inlet end-wall of a centrifugal pump and front cover of the impeller to connect the impeller with the inlet pipe by passing impeller leading edge. An unsteady numerical investigation was launched of the pump with and without this casing treatment, to study its influence on the pressure pulsations inside the pump and the mechanisms behind. The numerical results of the pump without casing treatment was first compared with the test performance of the pump to validate the numerical method, and gave excellent agreements with the test results. The CFD results also showed that the casing treatment increases the head coefficient and efficiency of the pump. Pressure pulsations at a reduced mass flow condition were studied by monitoring unsteady pressure signals generated by the CFD at various locations inside the pump. A Fast Fourier transform (FFT) was performed on the signals. The pump employs a double tongues volute with each tongue covering 180[Formula: see text] circumference. However, the two tongues are not identical with regard to the discharge of the pump. These geometric features of the volute and the pump’s operating condition generate several pressure pulsations in the frequencies of [Formula: see text], [Formula: see text], [Formula: see text] in the original pump. Due to the circumferential unifying capability of the casing treatment and its improvement to the impeller flow, these pulsations at impeller inlet are weakened or disappear when the U-tube is present. The pressure pulsation inside the impeller is less affected by the treatment. The [Formula: see text] pulsation at volute tongues also decreases or disappears for the same reasons, but [Formula: see text] pulsation increases slightly and this is due to the improved pressure recovery in the volute by the treatment which increases the pressure difference across one of the volute tongues. The unsteady radial force of the impeller exerting on journal bearings becomes more uniform and smaller when the casing treatment is employed.

Centrifugal pumps may run under off-design conditions such as low flows. Under such conditions, back-flow may occur at the impeller inlet and block a part of the flow path and cause energy loss. Casing treatment has been widely used in centrifugal compressors to improve their performance at low flow conditions, but there is little in the open literature on the effect of casing treatment on the performance of centrifugal pumps. In this paper, a SC100-200 centrifugal pump is studied with a casing treatment. First, the CFD method employed was described and verified by the experimental results of the pump. CFD indicates that the starting point of the back-flow is around discharge coefficient of 0.111 of the pump, and the back-flow intensity gradually increases with the decrease of flow rate reaching another critical point at discharge coefficient of 0.061 where the back-flow upstream traveling distance suddenly increases significantly. Then a casing treatment is created in the inlet end-wall and front cover using a U-tube type configuration. The numerical simulation was carried and it is found that a part of the back-flow at the inlet and front-side cavity of the centrifugal pump is sucked to the U-tube of the casing treatment and returns to the pump inlet, the back-flow and entropy production at the impeller inlet are reduced, and the head and efficiency of the pump is little affected. Further research shows that the longer the length of the U-tube is, the stronger the suction effect will be, and the smaller the back-flow of the pump.