Simulating Error-Opening of Pressure Relief Valves of a Station on a Continuous Undulating Oil Pipeline with Large Elevation Difference

For oil pipeline in mountain areas,high hydrostatic pressure in the pipeline may cause error-opening of pressure relief valves,and oil is discharged from the pipeline to the pressure relief tanks,bringing spilling-over risk of the pressure relief tanks.Therefore,simulating the error-opening situations of the pressure relief valves and investigating the oil discharge process are necessary for checking the possibility of the spilling-over accident and then proposing measures to improve the pressure relief system.This research focuses on a continuous undulating oil pipeline with large elevation difference and a station along this pipeline,which is named B station in this paper,is studied.By OLGA software,simulation model of the pressure relief system of B station is established,and the accuracy of the model is verified by reconstructing a real accident and making a comparison with the actual accident data.The maximum discharge rate reached 8284 m3/h when the pressure relief valve was opened by mistake in the inlet and outlet of the station.The accumulated filling time of the two pressure relief tanks is 200 s,which is in good agreement with the accident data.On this basis,for error-opening of the pressure relief valves at the inlet and outlet of B station,simulation is performed to investigate variations of the discharge velocity,discharge flow rate,accumulated discharge volume and ventilation volume of the vent valve.The discharge velocity is found to be over the maximum velocity allowed for safety consideration.According to the accumulated discharge volume,it is inferred that spilling over of the pressure relief tanks will be caused once error-opening of the pressure relief valve occurs.Also it is judged that the existing breathing valve can not satisfy the ventilation requirement in case of failure of the pressure relief valves.From these simulation results,it is proposed that increasing the number of vent valves,replacing the manual valves with electrically operated valves,and employing security control interlock protection program are improvement measures to guarantee safe,efficient and reliable operation of the pressure relief system at B station.

Gold nanoparticles with surface-anchored chiral poly（acryloyI-L（D）-valine） induce differential response on mesenchymal stem cell osteogenesis

Chirality is one of the most distinctive biochemical signatures of life, and plays crucial roles in maintaining normal functions of living cells or organisms. Pioneering work from another group has demonstrated the dependency of cell differentiation on the chirality of nano-coated substrates, but the effect of the chiral surface of nanoparticles on stem cell fates has not been investigated. In this study, the influence of molecular chiral poly（acryloyl-L（D）-valine） （L（D）- PAV）-anchored gold nanoparticles （L（D）-PAV-AuNPs） on the differentiation of mesenchymal stem cells （MSCs） was investigated. Though osteogenic differentiation of MSCs was not affected by D-PAV-AuNPs, it was significantly promoted by L-PAV-AuNPs in terms of calcium deposition, alkaline phosphatase （ALP） activity, and expression of collagen type I and osteocalcin （OCN） at both mRNA and protein levels. L-PAV-AuNPs could activate the P38 mitogen-activated protein kinase （MAPK） pathway, and may exert mechanical stress on MSCs because of high amounts of internalization. These results provide new insights on surface chirality at the nanoscale as a direct regulator to guide the differentiation of MSCs, and the use of these nanomaterials for strategic regenerative medicine.

A tarsus construct of a novel branched polyethylene with good elasticity for eyelid reconstruction in vivo

Branched polyethylene(B-PE)elastomer was investigated for its potential medical application as a tarsus construct.The in vitro results showed that the B-PE and processed B-PE films or scaffolds did not exhibit noticeable cytotoxicity to the NIH3T3 fibroblasts and human vascular endothelial cells(ECs).The B-PE scaffolds with a pore size of 280–480 mm were prepared by using a gelatin porogen-leaching method.The porous scaffolds implanted subcutaneously in rats exhibited mild inflammatory response,collagen deposition and fast fibrovascularization,suggesting their good biocompatibility.Quantitative real-time PCR analysis showed low expression of pro-inflammatory genes and up-regulated expressions of collagen deposition and vascularization-related genes,validating the results of historical evaluation in a molecular level.The B-PE scaffolds and Medpor controls were transplanted in rabbits with eyelid defects.The B-PE scaffolds exhibited a similar elastic modulus and provided desirable repair effects with mild fibrous capsulation,less eyelid deformities,and were well integrated with the fibrovascular tissue compared with the Medpor controls.