7055铝合金中低比例动态再结晶的模拟

研究7055铝合金在温度为390~470°C和应变速率为0.01~1 s^(−1)条件下热变形和动态再结晶行为。电子背散射衍射(EBSD)表征结果表明,7055铝合金在热变形下动态再结晶含量较低,动态再结晶含量为1%~13%。为了模拟低比例动态再结晶问题,对JMAK动态再结晶模型进行修正。应用修正的模型,结合商业有限元软件DEFORM-3D,对7055铝合金的热压缩过程进行数值模拟,模拟得到的动态再结晶比例和晶粒尺寸的平均绝对相对误差(AARE)分别为13.7%和6.3%,与实验结果吻合良好。为了进一步证实该模型的有效性,采用该方法对7055铝合金工业化热轧过程进行模拟,模拟结果表明热轧板的动态再结晶分布不均匀,与实验观察结果一致。

Stem cell transplantation for spinal cord injury： a meta-analysis of treatment effectiveness and safety

OBJECTIVE： The aim of this study was to evaluate the effectiveness and safety of stem cell transplantation for spinal cord injury（SCI）.DATA SOURCES： PubM ed, EMBASE, Cochrane, China National Knowledge Infrastructure, China Science and Technology Journal, Wanfang, and Sino Med databases were systematically searched by computer to select clinical randomized controlled trials using stem cell transplantation to treat SCI, published between each database initiation and July 2016. DATA SELECTION： Randomized controlled trials comparing stem cell transplantation with rehabilitation treatment for patients with SCI. Inclusion criteria：（1） Patients with SCI diagnosed according to the American Spinal Injury Association（ASIA） International standards for neurological classification of SCI;（2） patients with SCI who received only stem cell transplantation therapy or stem cell transplantation combined with rehabilitation therapy;（3） one or more of the following outcomes reported： outcomes concerning neurological function including sensory function and locomotor function, activities of daily living, urination functions, and severity of SCI or adverse effects. Studies comprising patients with complications, without full-text, and preclinical animal models were excluded. Quality of the included studies was evaluated using the Cochrane risk of bias assessment tool and Rev Man V5.3 software, provided by the Cochrane Collaboration, was used to perform statistical analysis. OUTCOME MEASURES： ASIA motor score, ASIA light touch score, ASIA pinprick score, ASIA impairment scale grading improvement rate, activities of daily living score, residual urine volume, and adverse events.RESULTS： Ten studies comprising 377 patients were included in the analysis and the overall risk of bias was relatively low level. Four studies did not detail how random sequences were generated, two studies did not clearly state the blinding outcome assessment, two studies lacked blinding outcome assessment, one study lacked follow-up information, and four studies carried out selective reporting. Compared with rehabilitation therapy, stem cell transplantation significantly increased the lower limb light touch score（odds ratio（OR） = 3.43, 95% confidence interval（CI）： 0.01 – 6.86, P = 0.05）, lower limb pinprick score（OR = 3.93, 95%CI： 0.74 – 7.12, P = 0.02）, ASI grading rate（relative risk（RR） = 2.95, 95%CI： 1.64 – 5.29, P = 0.0003）, and notably reduced residual urine volume（OR = –8.10, 95%CI： –15.09 to –1.10, P = 0.02）. However, stem cell transplantation did not significantly improve motor score（OR = 1.89, 95%CI： –0.25 to 4.03, P = 0.08） or activities of daily living score（OR = 1.12, 95%CI： –1.17 to 4.04, P = 0.45）. Furthermore, stem cell transplantation caused a high rate of mild adverse effects（RR = 14.49, 95%CI： 5.34 – 34.08, P 〈 0.00001）; however, these were alleviated in a short time. CONCLUSION： Stem cell transplantation was determined to be an efficient and safe treatment for SCI and simultaneously improved sensory and bladder functions. Although associated minor and temporary adverse effects were observed with transplanted stem cells, spinal cord repair and axon remyelination were apparent. More randomized controlled trials with larger sample sizes and longer follow-up times are needed to further validate the effectiveness of stem cell transplantation in the treatment of SCI.

电子胃肠镜在小儿消化道出血中的临床应用

目的回顾性分析进行内镜检查的14岁以下儿童消化道出血的发病年龄、出血原因和出血部位,进一步研究不同原因的消化道出血对外周血红细胞(RBC)、血红蛋白(Hb)和红细胞压积(HCT)的影响。方法选择2012年1月-2018年9月该院消化科因消化道出血住院的123例患儿,对发病年龄、临床表现、出血病因、出血部位以及RBC、Hb和HCT进行归纳总结。结果儿童消化道出血多见于学龄前期儿童,平均发病年龄(4.55±3.90)岁,临床以呕血73例、便血50例、腹痛17例为主要表现,上消化道出血105例,下消化道出血18例。上消化道出血原因为胃溃疡28例、出血性或糜烂性胃炎27例和十二指肠球部溃疡19例等,出血部位于胃体43处、胃窦39处和十二指肠球部16处等。下消化道出血原因为Meckel憩室7例、直肠结肠炎5例、肠息肉4例,出血部位于小肠处7例、直肠处7例和乙状结肠处6例。十二指肠球部溃疡、Meckel憩室、食道胃底静脉曲张导致的消化道出血,其RBC、Hb和HCT影响较大(P<0.05)。结论儿童上消化道出血发病率明显高于下消化道出血;上消化道出血原因以胃溃疡、出血性或糜烂性胃炎、十二指肠球部溃疡最为常见,出血部位以胃体、胃窦、十二指肠球部最常见。下消化道出血原因以Meckel憩室、直肠结肠炎、结肠息肉最为常见,出血部位以小肠、直肠、乙状结肠最常见,而十二指肠球部溃疡、Meckel憩室、食道胃底静脉曲张导致消化道出血对患儿临床危害较大,风险较高。

Tribological Properties of a Dendrite-reinforced Ti-based Metallic Glass Matrix Composite under Different Conditions

The tribological properties of the in-situ dendrite-reinforced metallic glass matrix composite（Ti42Zr22V14-Cu5Be17）prepared by copper mould casting were analyzed at different normal loads under the dry condition and rainwater.The results showed that the average value of the frictional coefficients and micro-hardness ascended with increasing the normal load,while the wear rate showed a trend of decline under the dry condition.The electrochemical test results showed that the surface of samples was pitting corroded in the rainwater.The matrices were corroded first.Then the dendrites were exposed,leading to the damage of the surface.Both the frictional coefficients and wear rate of the composite in the rainwater were larger than those under the dry condition,primarily owing to the corrosion of chloride ions on the worn surface.The wear mechanisms of composites were mainly adhesive wear,accompanied by the abrasive wear under the dry condition and corrosive wear in the rainwater.The composites have higher wear resistance both under the dry condition and rainwater due to the lower wear rate.