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By means of the ultrasonic surface impact (amplitude of 30 μm, strike number of 48,000 times/mm2), nanograins have been achieved in the surfaces of both Ti6Al4V(TC4) and Ti3Zr2Sn3Mo25Nb(TLM) titanium alloys, mainly because of the dislocation motion. Many mechanical properties are improved, such as hardness, residual stress, and roughness. The rotating–bending fatigue limits of TC4 and TLM subjected to ultrasonic impact are improved by 13.1% and 23.7%, separately. Because of the bending fatigue behavior, which is sensitive to the surface condition, cracks usually initiate from the surface defects under high stress amplitude. By means of an ultrasonic impact tip with the size of 8 mm, most of the inner cracks present at the zone with a depth range of 100~250 μm in the high life region. The inner crack core to TC4 usually appears as a deformed long and narrow α-phase, while the cracks in TLM specimens prefer to initiate at the triple grain boundary junctions. This zone crosses the grain refined layer and the deformed coarse grain layer. With the gradient change of elastic parameters, the model shows an increase of normal stress at this zone. Combined with the loss of plasticity and toughness, it is easy to understand these fatigue behaviors. 相似文献
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目的研究晚期肺癌化疗患者发生医院感染的病原学特点,分析其危险因素,降低晚期肺癌化疗患者医院感染率。方法选择2012年1月-2015年12月收治的532例晚期肺癌化疗患者为研究对象,采集患者痰液或呼吸道分泌物标本进行细菌培养,应用SAS 9.3软件进行统计分析,并分析晚期肺癌化疗患者发生医院感染的危险因素。结果 125例晚期肺癌化疗患者发生医院感染,感染率为23.50%,其主要感染部位为呼吸道、胃肠道、口腔黏膜,分别占52.00%、15.20%、14.40%;共分离病原菌104株,其中革兰阴性菌51株占49.04%、革兰阳性菌30株占28.85%、真菌23株占22.11%;logistics回归显示,住院时间长、接受侵入性操作、使用抗菌药物是晚期肺癌化疗患者发生医院感染的危险因素。结论晚期肺癌化疗患者医院感染率较高,主要病原菌以革兰阴性菌为主,通过缩短患者住院时间、减少侵入性操作、合理使用抗菌药物等措施,降低晚期肺癌化疗患者医院感染的发生。 相似文献
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Xia Li Wang Junni Xie Xishao Xiang Shilong Zhang Xiaohui Chen Jianghua Han Fei 《中华肾脏病杂志》2020,36(7):497-502
Objective To observe the clinical characteristics and prognosis of patients with rapidly progressive glomerulonephritis (RPGN) caused by lupus nephritis, antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis, or primary glomerulonephritis who were treated with peritoneal dialysis (PD) and then withdrew PD because of renal recovery. Methods Data of the above patients were retrospectively analyzed. The patients were diagnosed as RPGN and received PD therapy in Kidney Disease Center, the First Affiliated Hospital, College of Medicine, Zhejiang University from February 2009 to August 2018. The patients were divided into early withdrawal group (PD time≤183 days, n=24) and late withdrawal group (PD time>183 day, n=24). The differences of clinical characteristics between the two groups were compared. The cumulative incidence of adverse events in both groups was analyzed using Kaplan-Meier curves. Cox proportional hazards model was used to analyze the risk factors influencing the prognosis of patients. Results Forty-eight RPGN patients were included. The median time of maintaining PD was 178(76, 378) days. Compared with the late withdrawal group, the patients in early withdrawal group had lower levels of urine volume, serum albumin and parathyroid hormone, and lower rates of gross hematuria and hypertension at the beginning of PD, and received higher rates of methylprednisolone impulse, combined immunosuppressive agents, and hemodialysis or continuous renal replacement therapy (all P<0.05). At the time of PD withdrawal, the levels of serum creatinine, serum calcium, serum albumin and parathyroid hormone in the early withdrawal group were significantly lower than those in the late withdrawal group (all P<0.05). The Kaplan-Meier curves showed that there was no significant difference in the cumulative survival of patients in both groups (log-rank test χ2=3.485, P=0.062). Cox regression analysis revealed serum creatinine≥209 μmol/L at the time of PD withdrawal was an independent risk factor for poor prognosis (HR=5.253,95%CI 1.757-15.702, P=0.003). Conclusions PD can be used for RPGN patients caused by lupus nephritis, ANCA-associated vasculitis and primary nephritis. Serum creatinine≥209 μmol/L at the time of PD withdrawal is an independent risk factor for poor prognosis. 相似文献
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高校医学生会利用假期时间对将要学习的科目进行预习,力求提前了解或掌握,以利于日后对知识的充分理解。预习对于医学科目学习有一定必要性,然而传统的假期预习模式常存在缺乏引导、效率难以提升等问题。目前,慕课在医学教育领域的应用有所发展。对于医学生,其自主学习的模式、课程设计等契合医学课程的预习需求和假期学习的特点,有助于提升医学生的学习能力和假期预习效果。医学生将慕课作为假期预习资源可有多种学习模式选择。慕课平台的功能拓展和学校教师的辅助可以有效深入慕课在医学生假期预习中的应用,为医学生带来更合理的假期学习安排。 相似文献
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目的探讨胫前动脉踝上穿支皮瓣修复足踝部软组织缺损的临床疗效。方法回顾性研究2018年4月至2019年6月采用胫前动脉踝上穿支皮瓣修复足踝部软组织缺损19例的资料,其中男11例,女8例;年龄为21~75岁,平均39岁。根据前踝上穿支皮瓣解剖学基础,按照足踝部软组织缺损大小和形状,在小腿下端前外侧设计并切取皮瓣转位修复创面。切取胫前动脉踝上穿支皮瓣面积为6.0 cm×5.0 cm^14.0 cm×8.0 cm,均为带蒂皮瓣转位。根据皮瓣成活、感染控制、弹性色泽、外观形态、供区瘢痕、皮肤感觉、患者认可等情况,对患者足踝部软组织缺损的修复情况进行综合评价。结果本组19例皮瓣全部成活,软组织缺损、肌腱、骨质及钢板外露均得以修复。供区均I期愈合。术后门诊随访2~16个月,皮瓣血运良好,颜色接近周围正常皮肤,臃肿不明显,患者对外观表示满意;供区皮片愈合良好,无明显增生、挛缩及溃疡,踝关节功能良好。结论胫前动脉踝上穿支皮瓣是修复足踝部软组织缺损较为理想的方法之一,手术操作简便,穿支较恒定,血供可靠,具有一定的临床应用价值。 相似文献
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