扫描隧道显微镜钨针尖的制备与表征

采用直流电化学刻蚀方法制备扫描隧道显微镜钨针尖,研究了电化学刻蚀过程中NaOH溶液浓度、钨丝浸入长度和刻蚀电压对针尖形貌的影响。通过扫描电子显微镜(SEM)测量针尖曲率半径和针尖纵横比值,以表征针尖的尺寸和形状;通过能谱仪(EDS)分析针尖表面成分,以表征表面清洁度;通过场发射显微镜(FEM)得到Fowler-Nordheim (F-N)曲线来检测针尖发射性能。实验结果表明,当溶液浓度为2 mol/L、钨丝浸入长度为4 mm、刻蚀电压为3 V时,可以得到曲率半径约为100 nm、纵横比值为13的针尖,且表面无钨的氧化层。FEM结果显示当对针尖施加500 V的负偏压时,针尖可以稳定发射50 nA量级的电流,且针尖性能具有良好的一致性。

Quantitative Estimation of Pipeline Slope Disaster Risk in China

China’s economic development is closely related to oil and gas resources,and the country is investing heavily in pipeline construction.Slope geological hazards seriously affect the long-term safe operation of buried pipelines,usually causing pipeline leakage,property and environmental losses,and adverse social impacts.To ensure the safety of pipelines and reduce the probability of pipeline disasters,it is necessary to predict and quantitatively evaluate slope hazards.While there has been much research focus in recent years on the evaluation of pipeline slope disasters and the stress calculation of pipelines under hazards,existing methods only provide information on the occurrence probability of slope events,not whether a slope disaster will lead to pipeline damage.Taking the 2015 Xinzhan landslide in Guizhou Province,China,as an example,this study used discrete elements to simulate landslide events and determine the risk level and scope for pipeline damage,and then established a pipe-soil coupling model to quantitatively evaluate the impact of landslide hazards for pipelines in medium-and high-risk areas.The results provide a reference for future pipeline disaster prevention and control.

Study on the thermal decomposition characteristics of C_(4)F_(7)N-CO_(2)mixture as ecofriendly gas-insulating medium

The authors explored the thermal decomposition characteristics of perfluoroisobutyronitrile–carbon dioxide(C_(4)F_(7)N–CO_(2))gas mixture as eco-friendly dielectric medium.The main by-products and decomposition mechanism of C_(4)F_(7)N–CO_(2)gas mixture under different temperature and gas pressure conditions were revealed and analysed.It was found that the thermal decomposition of 6%C_(4)F_(7)N–94%CO_(2)gas mixture starts at about 350°C(0.15 MPa),producing C_(3)F_(6) and CO first.Some other characteristic by-products such as CF_(4),C_(2)F_(6),CF_(3)CN,COF_(2) and(CN)_(2) could also be detected at higher temperature.The yield of C_(3)F_(6),(CN)_(2) increased with the temperature(lower than 450℃)first and then decreased when it reached to 500℃.While the yield of CO,C3F8,COF_(2) and CF_(3)CN increased with temperature(350–550℃).The generation of CF_(4) and C_(2)F_(6) begins at temperatures higher than 500℃,which can be used as the feature component of severe overheating fault.The thermal decomposition amount and by-products yield of C_(4)F_(7)N–CO_(2)gas mixture slowed down with the increase of gas pressure,indicating that C_(4)F_(7)N–CO_(2)gas mixture is quite suitable used at high-pressure equipment,especially high-voltage devices such as gas insulated switchgear.

Liver injury induced by levothyroxine tablets in a patient with hypothyroidism

To the Editor: On March 9, 2018, a 31-year-old woman presented with liver dysfunction after thyroid cancer surgery. She was physically healthy;had no chronic diseases, such as hypertension and diabetes;had no history of infectious diseases, such as hepatitis and tuberculosis;had no history of drugs, food allergies, smoking, and alcohol consumption;and presented no obvious complaints during the disease course. B-ultrasound in the physical examination 3 years prior showed “left thyroid-occupying position.” On February 5, 2018, she had undergone surgery at our hospital. Laboratory findings on February 6, 2018 revealed white blood cells (WBCs) 9.06 × 10^9/L (3.50–9.50 × 10^9/L);neutrophils (NEs) 5.66 × 10^9/L (1.80–6.30 × 10^9/L);triiodothyronine (T3) 0.94 (0.80–2.00) ng/mL;thyroxine (T4) 6.4 (5.1–14.1)μg/dL;free T3 (FT3) 3.95 (3.10–6.80) pmol/L;free T4 (FT4) 15.57 (12.00–22.00) pmol/L;thyroid-stimulating hormone (TSH) 2.56 (0.27–4.20) mU/L;thyroid peroxidase antibody (TPOAb) 8.2 (0–34.0) IU/mL;thyroglobulin antibody (TgAb)<10 (≤115) IU/mL;total bilirubin (T-BIL) 21.5 (5.0–22.0)μmol/L;direct bilirubin (D-BIL) 6.3 (0–10.2)μmol/L;alanine transaminase (ALT) 27.5 (7.0–40.0) U/L;aspartate transaminase (AST) 22.7 (13.0–35.0) U/L;and alkaline phosphatase (ALP), 48.9 (35.0–100.0) U/L. Hepatitis C antibody, hepatitis B surface antigen, and hepatitis B core antibody immunoglobulin M tested negative. On February 7, 2018, intra-operative pathology during left thyroidectomy indicated micro-papillary carcinoma. On February 11, 2018, she was discharged and prescribed levothyroxine tablets A (LTA;Merck KGaA, Darmstadt, Germany) 100 μg and calcium carbonate D3 tablets (CC-D3;Pfizer, China) 600 mg once daily.

A linked data-based approach for clinical treatment selecting support

Treatment plan selection is a complex process because it sometimes needs sufficient experience and clinical information.Nowadays it is even harder for doctors to select an appropriate treatment plan for certain patients since doctors might encounter difficulties in obtaining the right information and analyzing the diverse clinical data.In order to improve the effectiveness of clinical decision making in complicated information system environments,we first propose a linked data-based approach for treatment plan selection.The approach integrates the patients’clinical records in hospitals with open linked data sources out of hospitals.Then,based on the linked data net,treatment plan selection is carried on aided by similar historical therapy cases.Finally,we reorganize the electronic medical records of 97 colon cancer patients using the linked data model and count the similarity of these records to help treatment selecting.The experiment shows the usability of our method in supporting clinical decisions.

波折钢板剪力墙内嵌墙板与框架的相互作用分析

随着高层建筑的不断发展,水平荷载愈发成为结构设计中不可忽略的因素,钢板剪力墙因其优越的抗侧力性能,在实际工程中得到广泛的应用,研究人员对其受力性能开展了深入的研究。普通平钢板剪力墙具有较高的极限承载力,但在往复荷载作用下滞回曲线出现"捏拢",尤其是薄钢板会发出巨大噪声,影响结构舒适性。波折钢板由于波折的存在,具有更高的面外刚度,呈现出面内剪切屈曲的受力特征,延性较好。与普通平钢板剪力墙相比,其抗侧性能及墙板抗侧机制仍有待研究,且在水平荷载和竖向荷载共同作用下的受力性能研究也比较缺乏。通过有限元方法分析了内嵌波折钢板的抗侧力机制,提出相对应的框架柱门槛抗弯刚度要求,研究了竖向荷载对墙板性能的影响,给出工程实用设计建议。首先,利用有限元软件ABAQUS模拟循环加载试验,将试验与有限元拟合结果进行对比,验证利用ABAQUS软件分析波折钢板墙的有效性与准确性;通过对两个典型算例的荷载-位移曲线分析,指出波折钢板墙的两种不同的抗侧力机制,分析这两个算例的框架弯矩分布,表明波折钢板通过"四边受剪"或"拉力带"两种机制抵抗侧向力,且抗侧力机制由内嵌钢板的几何参数决定。如果波折板主要通过"拉力带"抵抗侧向荷载,由于波折的存在,"拉力带"不能充分发展,就会出现残余承载力较低的情况;其次,以非加劲平钢板剪力墙边缘柱的截面抗弯刚度要求为基础,分析框架在弹性和弹塑性两种情况下,边缘柱截面抗弯刚度对墙板性能的影响,指出正则化高厚比越大,柱截面抗弯刚度对墙板性能的影响越大,当正则化高厚比λ_n≤0.45时可以认为波折钢板主要通过"四边受剪"机制抵抗侧向力,这时对框架柱的抗弯刚度要求较小,可以采用截面抗弯刚度EI≥0.5EI~*的框架柱,在实际工程中推荐使用λ_n≤0.45的波折钢板以保证足够的残余承载力;最后,针对正则化高厚比小于0.45的波折钢板墙,研究竖向荷载对墙板性能的影响,改变作用在柱子上的轴向压力,观察墙板承载力的变化情况,指出竖向荷载对墙板极限承载力影响很小,但由于边缘柱在残余状态下产生较大的竖向压缩,导致墙板剪力不能有效传递,进而引起柱子残余承载力下降,正则化高厚比越大的墙板,残余承载力下降越严重,实际工程中可以通过增大柱截面面积避免这种情况的出现。