Risk Assessment Based on Fault Tree Analysis for Damaged Pipe Repair During Operation in Petrochemical Plant

In petrochemical plant, the in-operation repairing is usually a repairing strategy with pressured inoperation repairing for avoiding huge economic losses caused by unplanned shutdown when some slight local leakage happens in pipes. This paper studies the effects of repairing strategies on the failure probability of the pipe systems in process industries based on the time-average fault tree approach, especially the in-operation repairing strategies including pressured in-operation repairing activities. The fault tree model can predict the effect of different repairing plans on the pipe failure probability, which is significant to the optimization of the repairing plans. At first pipes are distinguished into four states in this model, i.e., successive state, flaw state, leakage state and failure state. Then the fault tree approach, which is usually applied in the studies of dynamic equipment, is adopted to model the pipe failure. Moreover, the effect of pressured in-operation repairing is also considered in the model. In addition, this paper proposes a series of time-average parameters of the fault tree model, all of which are used to calculate node parameters of the fault tree model. At last, a practical case is calculated based on the fault tree model in a repairing activity of pipe thinning.

Experimental Effect of Umbilical Cord Mesenchymal Stem Cells on Stress Urinary Incontinence Rats Model and Efficient Tracking in vivo with MRI

Objective To assess the effect of intra-sphincteric injections of human umbilical cord mesenchymal stem cells(HUMSCs)on leak point pressure(LPP)changes in an animal model of stress urinary incontinence(SUI).Meanwhile,to investigate in vivo MRI tracking HUMSCs in SUI rats using a clinically available paramagnetic contrast agent(Gd-DTPA)and commercially available effentence transfection reagents..Materials and Methods HUMSCs were dual labeled with Gd-DTPA and PKH26,the labeling efficiency and longevity of Gd-DTPA maintenance were measured and cell viability and proliferation were assessed.39 female Sprague–Dawley SUI rats.12 normal rats and 12 SUI rats received periurethral injection of PBS and 12 SUI rats were given periurethral injection of dual labeled HUMSCs.3 SUI rat sreceived periurethral injection of u nlabeled HUMSCs.Six weeks after injection,LPP was undertaken in animals.All rats were sacrificed and frozen urethra sections were submitted to pathology and immunohistochemistry assessment.Results The labeling efficiency of Gd-DTPA was up to 80%,the labeling procedure did not influence cell viability and proliferation.The signal intensity on T1-weighted imaging and T1 values of labeled cells were significantly higher than those of unlabeled cells.In vitro,differentiated HUMSCs expressed myosin heavy chain(MHC)and desmin,markers of striated muscles.In vivo,immunohistochemistry of rat urethras revealed dual labeled HUMSCs in situ and at the injection site.LPP was significantly improved in animals injected with HUMSCs.Atrophic urethras with implanted HUMSCs were positively stained for MHC and desmin.The distribution and migration of labeled cells could be tracked by MRI more than 14 days after t ransplantation.Conclusion HUMSCs have the ability to differentiate striated muscles,as demonstrated by MHC and desmin expression.Periurethral injection of HUMSCs in an animal model of SUI restored the damaged external urethral sphincter and significantly improved LPP.MRI can track Gd-DTPA–labled HUMSCs in an animal model of SUI in vivo.

The effect of different inflation volumes of laryngeal mask airway on efficacy of closed circuit controlled ventilation in pediatric cancer patients

Objective： The laryngeal mask airway （LMA） is an established way for airway control during spontaneous ventila- tion. Its ability to deliver positive pressure ventilation without leakage especially in low flow states is still controversy. The aim of this study is to test the possibility of using LMA in pediatric closed circuit controlled ventilation, and to find out the optimum cuff volume to perform closed system ventilation. Methods： Twenty children scheduled for elective surgeries were enrolled in a crossover study. Laryngeal mask airway was used. In stage I, the cuff was inflated with the maximum volume of air as rec- ommended by the manufacturers. Adjustment of volume of air inflated into the LMA cuff to the minimum volume to obtain the effective seal was done at stage II. The leak pressure, intracuff pressure and the leak volume were measured in both stages. Results： The cuff filling volume was significantly lower compared to the maximum cuff inflation volume in stage I. Leakage values showed significantly less values in stage II of the study with smaller cuff inflation volumes. The airway leakage pressure was significantly lower in stage fl in comparison to stage I. Cuff inflation pressure in stage I showed marked elevation which dropped significantly after adjustment of cuff volume in stage I1. Conclusion： Laryngeal mask airway is an effective tool to provide closed circuit controlled ventilation in pediatrics. Inflation of the cuff by the minimum volume of air needed to reach the just sealing pressure is suggested to minimize the leakage volume.