Imatinib mesylate in clinically suspected gastric stromal tumors

Gastrointestinal stromal tumors （GISTs） occur most frequently in the stomach.Diagnosis of gastric GIST is not always clear before surgery.Flexible endoscopy may suggest the nature of the lesion （a bulky tumor with preserved mucosa）; however,biopsy is rarely diagnostic.Therefore,diagnostic medication with safe drugs may provide a feasible way under such conditions after an informed consent is obtained.Based on the excellent efficacy of imatinib mesylate （IM） in the treatment of GIST,we successfully applied it in the diagnostic medication of two patients with clinically suspected gastric stromal tumors.In conclusion,the diagnostic medication with IM can be an alternative option for patients with suspected GIST that can not be confirmed pathologically.

高转速浮装式机械密封端面变形影响因素分析及优化

Floating mechanical seals play an important part in the high-speed rotating machine,and its face deformation will lead to seal failure,also directly affects the device operation performance and service life.In this paper,based on the finite element method,a two-dimensional model of the thermal coupling numerical analysis high speed floating mechanical seal was established,and the influence of different parameters such as rotating speed,pressure,temperature and axial compression force on the deformation of seal face is analyzed.It is found that the dynamic and static face deformation increases exponentially with the increase of rotational speed.At high speed,with the increase of working pressure and temperature,the sealing face deformation increases linearly.When the working pressure reaches 8MPa,the sealing face is in dynamic balance,and no further deformation occurs.Under the condition of high speed and negative temperature difference,the deformation of the sealing end face is positive,with the increase of the axial compression force,the end face shrinked inward,and the deformation rate sudden decrease when the force reaches 4MPa.On the contrary,while the temperature difference is positive,the deformation of the seal end face is negative,and the end face expands outward,meanwhile the expansion of deformation are posi-tively correlated with the axial compression force.According to the analysis results,the control optimization method of the end face deformation is put forward,and the accuracy of the numerical analysis results is verified by the high-speed floating mechanical seal test platform,which provides theoretical guidance for the design and use of high-speed floating sealing ring.

高速动压式胀圈密封温升变形及试验研究

针对高速旋转机械的高转速、低磨损和长寿命的要求,研制出非接触且磨损小的动压式胀圈密封,但是当密封设计不当时,密封环变形会严重影响其密封性能和稳定性,因此,本文针对动压式胀圈密封结构参数对温升、变形的影响展开分析。利用有限元分析软件建立流固热耦合分析模型,通过数值模拟和试验相结合的方法分析胀圈动静环主要结构参数对密封环温升、变形的影响规律,基于响应面法对密封进行多参数结构优化。研制出动压式胀圈密封的试验样机及试验系统,并进行实际运转试验。结果发现,动压式胀圈密封可大幅降低密封温升和摩擦磨损,从而提高其密封性能和稳定性;减小螺旋角、选择合适的槽坝比可降低密封环的温度峰值和变形峰值;减小轴向厚度可降低密封环端面温度和变形,减弱端面温度分布和变形分布不均的程度;增大压差可降低切口间隙端面的最大变形和变形不均的程度,增加转速可降低主密封面变形峰值。研究结果为解决旋转设备轴承腔的高速密封难题提供了新思路和新方法,为动压式胀圈密封的结构设计提供参考,并促进其性能提升和工程应用。

考虑蠕变特性的航空发动机阀门用非金属垫片的密封性能研究

The valve gasket for aero-engine is prone to creep under extreme conditions such as high temperature and high pressure.The creep failure of the gasket leads to valve leakage,which seriously threatens the safe and reliable operation of aero-engine.Aiming at the creep failure of FEP gasket in use,a timehardening creep model of valve gasket seal is established.The effects of time,operating pressure,material and structural parameters on the creep and sealing properties of FEP gaskets are analyzed.The results show that the compression rebound rate of gaskets decreases with the increase of time,and small compression rebound rate will decrease the sealing performance.The creep behavior of FEP gasket increases with the increase of operating pressure.Reducing the fillet radius can reduce the probability of shear failure,but also reduce the contact stress.Increasing the height of the boss can reduce the deformation behavior of the gasket,but reduce the contact stress on the sealing surface.When the gasket bevel angle is 85°,the creep property and contact stress of the gasket are higher than those of other sizes.But large bevel angle leads to the gasket unsticking.Replacing the FEP material with the polyimide material can improve the creep resistance of gaskets and the contact stress of sealing surface.Considering the service life and sealing effect of gasket,the material is replaced with polyimide plastic,the fillet radius is 0.20mm,the bevel angle is 85°and the boss height is 0.2mm.

高速气体环瓣式浮环密封泄漏特性的试验研究

密封的泄漏特性是对密封性能的关键表征。本文试验研究了应用于某高速发动机的气体环瓣式浮环密封在改变转速、密封压差、周向弹簧比压条件下的泄漏特性以及不同弹簧比压下的磨损情况。试验结果表明,密封环泄漏量随压力升高而线性增长,但随转速增加,泄漏量略有降低;随着周向弹簧比压增加,泄漏量存在极小值,在4~5N/m的范围内,泄漏量较小;弹簧比压增大,密封环与转子(又称跑道)表面之间磨损加剧,严重情况下会发生石墨环和转子表面之间的粘着磨损,在满足泄漏要求的前提下应选用小的弹簧力。为了研究环瓣式浮动环密封中三处泄漏点对总密封性能的影响,试验测定了主、次密封和搭接头三处泄漏点的静态泄漏量,其中主密封泄漏量占比最大约70%;次密封约为20%;搭接头处的泄漏量最小。研究表明,使用前预跑合能明显提高浮环的密封性能。

基于热-固耦合的船舶艉轴密封环材料对密封性能的影响研究

在采用螺旋桨推进的船舶中,为防止海水沿螺旋桨流入船内,在艉轴管中设置了密封。由于其工作于恶劣的深水环境中,因此选用可靠的艉轴密封环材料对船舶运行至关重要。本文根据不同船舶艉轴密封环材料对密封性能的影响,利用有限元软件建立热-固耦合数值分析模型,计算得到了不同材料密封环的温度场、变形场、应力场,分析了弹性模量、热膨胀系数、导热系数等材料参数对密封环变形、温升、摩擦磨损及泄漏量的影响,最终选取了最优的船舶艉轴机械密封动环材料。结果表明:SiC动环材料的密封环组合端面温升最小,S30408动环材料的端面变形最大,密封端面的热变形大于力变形,热膨胀系数对密封性能影响最大,综合考虑温升和材料参数对密封环变形和密封性能的影响,选择最优的动环材料为Cr2O3。

Comparison of tumor regression grading systems for locally advanced gastric adenocarcinoma after neoadjuvant chemotherapy

BACKGROUND Current tumor regression grade(TRG)evaluations are based on various systems which brings confusion for oncologists and pathologists when interpreting results.The recent six-tier system(JGCA2017-TRG)recommended by the Japanese Gastric Cancer Association(JGCA)is worth investigating,as four-tier TRG systems are favored in various parts of the world.AIM To compare the predictive accuracies of five published TRG systems.METHODS Data were retrospectively collected from patients with locally advanced gastric cancer(LAGC)who underwent neoadjuvant chemotherapy followed by D2 Lymphadenectomy between January 2005 and January 2014 at our institution.Outcomes were overall survival(OS)and disease-free survival(DFS),which were evaluated separately using the following TRG systems:JGCA2017,JGCA,Becker,AJCC/CAP,and Mandard.RESULTS All five published TRG systems were independent predictors for OS and DFS.Concordance indices of the JGCA2017,JGCA,Becker,AJCC/CAP-TRG,and Mandard systems were 0.651/0.6480.652/0.649,0.693/0.695,0.688/0.685,and 0.674/0.675 for OS and DFS,respectively.The four-tier Becker system showed the highest c-index,which was significantly greater than that of the six-tier JGCA2017 and five-tier JGCA systems(P<0.05 in OS and DFS).When residual tumor percentages were reset as:“no residual tumor”,<10%,<100%,and“no response”,the rearranged cutoff values achieved a maximum c-index with 0.728 for OS and 0.737 for DFS,which was superior to the other five systems.CONCLUSION The newly introduced six-tier JGCA-TRG system cannot increase prognostic stratification.The four-tier Becker system is more suitable for LAGC patients.A population-based study is warranted to define the optimal criterion for TRG in LAGC patients.

Management recommendations for patients with chronic kidney disease during the novel coronavirus disease 2019(COVID-19)epidemic

COVID-19 has become a pandemic and it has already spread to at least 171 countries/regions.Chronic kidney disease(CKD)is a global public health problem with a total of approximately 850 million patients with CKD worldwide and 119.5 million in China.Severe COVID-19 infection may damage the kidney and cause acute tubular necrosis,leading to proteinuria,hematuria and elevated serum creatinine.Since the SARS-CoV-2 enters the cells by binding to the angiotensin-converting enzyme 2 receptor,some doctors question its ability to increase the risk and severity of developing COVID-19.Neither clinical data nor basic scientific evidence supports this assumption.Therefore,patients who take angiotensin-converting enzyme inhibitor or angiotensin receptor blocker are not advised to change their therapy.Patients with CKD are generally the elderly population suffering from multiple comorbidities.Moreover,some patients with CKD might need to take glucocorticoids and immunosuppressants.Dialysis patients are recurrently exposed to a possible contaminated environment because their routine treatment usually requires three dialysis sessions per week.Considering all the above reasons,patients with CKD are more vulnerable to COVID-19 than the general population.The development of COVID-19 may worsen the impaired kidney function and further lead to rapid deterioration of kidney function and even death.Strict comprehensive protocols should be followed to prevent the spread of COVID-19 among patients with CKD.In this review,we provide some practical management recommendations for health care providers,patients with CKD,dialysis patients and dialysis facilities.