At speeds above 300-350 km/h, the main source of noise from trains is the aerodynamic noise caused by the air flow over the train structure. The sound level increases with train speed at a rate of between 60 and 80 times the logarithm of the speed so that, as speeds increase further, the noise increases dramatically. The main aerodynamic noise is produced by the air flow passing over the pantograph, the train nose, the bogie region and cavities such as the pantograph recess and the inter-coach gap. Experimental and numerical methods for studying aerodynamic noise are reviewed including the use of microphone arrays, wind tunnels, computational fluid dynamics and semi-empirical methods. Potential mitigation measures that can control aerodynamic noise are also reviewed.

Expression and characteristics of matrix metalloproteinase-9 (MMP-9) and TIMP metallopeptidase inhibitor-1 (TIMP-1) in the placenta of pregnancy induced hypertension (PIH) were detected in Uygur to analyze its correlation with PIH, and to provide a theoretical basis for clinical work. Ninety cases of placental tissue patients who were hospitalized in the Department of Obstetrics of People's Hospital of Xinjiang Uygur from December 2014 to September 2016 were collected, including 30 cases of severe preeclampsia, 30 cases of mild preeclampsia, and 30 cases of normal group. The distribution of MMP-9 and TIMP-1 in placenta was mainly in the cytoplasm of trophoblast cells, vascular endothelial cells and villous mesenchymal cells. The distribution of MMP-9 positive particles in the placenta tissue of the severe group was significantly reduced. The difference of MMP-9 in the three groups was statistically significant. Severe group was statistically significantly different from normal and mild group. With the aggravation of PIH, positive expression of MMP-9 was gradually decreased. TIMP-1 was expressed in each group, and difference was not statistically significant. Positive expression ratio of MMP-9/TIMP-1 in severe group was lower than that in normal pregnancy and mild group, and positive expression ratio of the two groups became smaller as the condition worsened. Positive expression of MMP-9 in placental tissue of patients with PIH decreased significantly with the severity of PIH. TIMP-1 in placental tissue of PIH patients did not change much in each group, and had no significant correlation with PIH.

A numerical investigation of the aeroacoustic characteristics of the flow past a circular cylinder is presented for Reynolds numbers in the range 2.67 × 10 4 − 3.67 × 10 5 , which falls within the upper subcritical and critical regimes. This is based on Computational Fluid Dynamics simulations using a Delayed Detached-Eddy Simulation (DDES) model for the aerodynamics of the near-field, which feeds the equivalent source terms into the Ffowcs Williams-Hawkings equation for far-field noise prediction. The accuracy of DDES in predicting unsteady flow quantities is assessed from an engineering viewpoint through comparisons with experimental data. Good agreement is found for both the near-field flow quantities and the far-field noise spectra. The aerodynamic and aeroacoustic characteristics are investigated from two aspects, the effect of varying the Reynolds number and the sensitivity to the spanwise computational dimension. The results in terms of the vortex shedding frequency, hydrodynamic forces and far-field noise levels only show small variations in the subcritical range. However in the critical range, the vortex shedding frequency increases and the noise level decreases considerably after allowing for the typical sixth power dependence. A spanwise length of 3D is found to be sufficient for most Reynolds numbers in the critical range, but in the subcritical range, a longer spanwise length is needed and the sound level may be under-predicted by up to around 4.5 dB by using 3D.

Emerging pseudorabies virus (PRV) variant has led to frequent outbreaks of PRV infection among Bartha-K61-vaccinated swine population in Chinese swine farms and caused high mortality in pigs of all age since late 2011. Here, we generated a gE/gI-deleted PRV (rPRVXJ-delgI/gE-EGFP) based on PRV variant strain (PRV-XJ) through homologous DNA recombination. Compared to parental strain, rPRVXJ-delgI/gE-EGFP showed similar growth kinetics in vitro. Its safety and immunogenicity were evaluated in weaned piglets. Our results showed that piglets immunized with rPRVXJ-delgI/gE-EGFP did not exhibit any clinical symptoms, and a high level of gB-specific antibody was detected. After lethal challenge with variant PRV (PRV-FJ strain), all vaccinated piglets survived without showing any clinical symptoms except slight fever within 7 days post-challenge. In unvaccinated piglets, typical clinical symptoms of pseudorabies were observed, and the piglets were all died at 5 days post-challenge. These results indicated that a live rPRVXJ-delgI/gE-EGFP vaccine could be a maker vaccine candidate to control the currently epidemic pseudorabies in China.

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