Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis

Fracture during the assembly process is an important failure mode for high-lock bolts used in the aviation industry, which greatly increases the potential of unpredictable accidents during service. In the current study, the underlying reasons for fracture during the assembly of a TC4 high-lock bolt was investigated using a tensile test and finite element analysis (FEA). The microstructure of the as-received bolt consisted of a high proportion of α phase, some β phase, and a small amount of α′ phase formed via martensite phase transformation during the rammer process. The experimental force–displacement curves revealed an average yield load of 55.9 kN and a breaking load of 67.65 kN. The corresponding yield strength was calculated to be 0.9 GPa, which was smaller than the standard value of TC4. This was attributed to the preload-induced stress concentration on the thread surface, leading to obvious strain hardening, which can lead to crack initiation. The effect of preload was further confirmed by the fractographies in which the initial crack was observed on the thread surface. The fractographies suggested that hybrid fracture occurred on the tensile loaded bolt. The initial failure was brittle fracture on the thread surface, transforming into ductile fracture in the screw. The results can contribute to understanding the effect of preload on the load carry capacity of high-lock bolts and provide a strategy to design its assembly specification.     

传统扬琴的地域特征

扬琴是一种有着广泛的世界性和民族性的击弦乐器,于明代自国外传至中国。四百多年采扬琴在中国传统音乐文化环境的影响下,不断和民间音乐融合,并在一代代的扬琴艺人的探索和创新中,发展成了具有中国特色的民族乐器,成为世界扬琴三大体系之一的中国扬琴体系,同时形成了中国传统扬琴的四大流派。     

Prenatal Bisphenol a Exposure and Postnatal Trans Fat Diet Alter Small Intestinal Morphology and Its Global DNA Methylation in Male Sprague-Dawley Rats,Leading to Obesity Development

In this study, we aimed to determine whether a postnatal trans fat diet (TFD) could aggravate prenatal bisphenol A (BPA) exposure effects on offspring’s small intestine and adulthood obesity, due to the relatively sparse findings on how the interaction between these two variables interrupt the small intestinal cells. Twelve pregnant rats were administered with either unspiked drinking water (control; CTL) or BPA-spiked drinking water throughout pregnancy. Twelve weaned pups from each pregnancy group were then given either a normal diet (ND) or TFD from postnatal week (PNW) 3 until PNW14, divided into control offspring on normal diet (CTL-ND), BPA-exposed offspring on normal diet (BPA-ND), control offspring on trans fat diet (CTL-TFD), and BPA offspring on trans fat diet (BPA-TFD) groups. Body weight (BW), waist circumference, and food and water intake were measured weekly in offspring. At PNW14, small intestines were collected for global DNA methylation and histological analyses. Marked differences in BW were observed starting at PNW9 in BPA-TFD (389.5 ± 10.0 g; p < 0.05) relative to CTL-ND (339.0 ± 7.2 g), which persisted until PNW13 (505.0 ± 15.6 g). In contrast, water and food intake between offspring were significantly different (p < 0.01–0.05) at earlier ages only (PNW4–6 and PNW7–9, respectively). Furthermore, substantial differences in the general parameters of the intestinal structures were exclusive to ileum crypt length alone, whereby both BPA-ND (150.5 ± 5.1 μm; p < 0.001), and BPA-TFD (130.3 ± 9.9 μm; p < 0.05) were significantly longer than CTL-ND (96.8 ± 8.9 μm). Moreover, BPA-ND (2.898 ± 0.147%; p < 0.05) demonstrated global small intestinal hypermethylation when compared to CTL-ND and CTL-TFD (1.973 ± 0.232% and 1.913 ± 0.256%, respectively). Prenatal BPA exposure may significantly affect offspring’s physiological parameters and intestinal function. Additionally, our data suggest that there might be compensatory responses to postnatal TFD in the combined BPA prenatal group (BPA-TFD).     

植物多糖对家兔动脉粥样硬化脂质过氧化及炎症反应的干预

目的:探讨枸杞多糖、黄芪多糖对家兔动脉粥样硬化(As)脂质过氧化及炎症反应的干预机制。方法:将48只雄性新西兰大白兔随机分为4组:正常组(12只),As模型组(12只),枸杞多糖(LBP)治疗组和黄芪多糖(APS)治疗组。10周后,测定各组空腹甘油三酯(TG)、总胆固醇(TCh)、高密度脂蛋白胆固醇(HDL-C)、一氧化氮(NO)、丙二醛(MDA)、C反应蛋白(CRP)、内皮素-1(ET-1)的含量以及超氧化物歧化酶(SOD)活性,并计算HDL-C/TCh,同时计算主动脉内膜粥样斑块面积。结果:模型组与正常组比较,TG、TCh、ET-1、NO、CRP、MDA明显升高(P<0.01),HDL-C/TCh、SOD活性明显下降(P<0.01),主动脉内膜粥样斑块面积较大;而LBP和APS治疗组与模型组比较,TG、ET-1、NO、CRP明显下降(P<0.01),HDL-C/TCh和SOD活性明显升高(P<0.01),主动脉内膜粥样斑块面积明显减少(P<0.01)。结论:枸杞多糖和黄芪多糖对动脉粥样硬化有明显的预防和治疗作用,机制可能与降低血脂、抗氧化、调节免疫等功能有关。     

Impact of pathological response after preoperative transcatheter arterial chemoembolization (TACE) on incidences of microvascular invasion and early tumor recurrence in hepatocellular carcinoma: a multicenter propensity score matching analysis

BackgroundTo study the influence of pathological responses (PR) after transcatheter arterial chemoembolization (TACE) on incidences of microvascular invasion (MVI) and early recurrence in hepatocellular carcinoma (HCC) patients.MethodsBetween 2013 to 2015, consecutive HCC patients who underwent liver resection with “curative” intent at three hospitals were enrolled in this study. Patients with different areas of PR after preoperative TACE were compared with those without preoperative TACE on the incidences of MVI, early recurrence rates and patterns of recurrence before and after propensity score matching (PSM).ResultsOf 1,970 patients, 737 patients who received preoperative TACE were divided into three groups according to the areas of PR: ≥90% (n=226), 60–90% (n=447), and <60% (n=64). PR ≥90% was an independent protective factor of incidences of MVI [odds ratio (OR), 0.144; 95% confidence interval (CI), 0.082–0.245, P<0.001) and early recurrence (HR, 0.742; 95% CI, 0.561–0.963, P=0.032); while PR<60% was an independent risk factor of incidences of MVI (OR, 6.076; 95% CI, 3.004–11.728, P<0.001) and early recurrence (HR, 1.428; 95% CI, 1.095–1.929; P=0.009). Furthermore, patients with PR <60% were significantly more likely to develop multiple intrahepatic recurrences involving multiple hepatic segments when compared with patients without preoperative TACE.ConclusionsThis study indicated the area of PR after TACE was closely associated with the incidences of MVI and early tumor recurrence. Patients with PR <60% were at significantly higher risks of having more MVI, early and multiple tumor recurrences     

A new heparin fragment decreases liver ischemia-reperfusion injury

<正>To the Editor:Ischemia-reperfusion injury following surgery and transplantation can lead to irreversible multiorgan failure.Intracellular calcium overload is associated to cellular death during ischemiareperfusion.A recently discovered heparin fragment (HF),trisulfated disaccharide (TD),that acts on sodium-calcium exchanger(NCX) decreasing intracellular Ca²⁺,showed effectiveness on protecting hepatocytes from ischemia-reperfusion injury [1],     

The kinase p38α functions in dendritic cells to regulate Th2-cell differentiation and allergic inflammation

Dendritic cells (DCs) play a critical role in controlling T helper 2 (Th2) cell-dependent diseases, but the signaling mechanism that triggers this function is not fully understood. We showed that p38α activity in DCs was decreased upon HDM stimulation and dynamically regulated by both extrinsic signals and Th2-instructive cytokines. p38α-specific deletion in cDC1s but not in cDC2s or macrophages promoted Th2 responses under HDM stimulation. Further study showed that p38α in cDC1s regulated Th2-cell differentiation by modulating the MK2−c-FOS−IL-12 axis. Importantly, crosstalk between p38α-dependent DCs and Th2 cells occurred during the sensitization phase, not the effector phase, and was conserved between mice and humans. Our results identify p38α signaling as a central pathway in DCs that integrates allergic and parasitic instructive signals with Th2-instructive cytokines from the microenvironment to regulate Th2-cell differentiation and function, and this finding may offer a novel strategy for the treatment of allergic diseases and parasitic infection.     

白塞综合征20例临床特征及心血管影像学分析

回顾性分析2018年1月—2020年8月首都医科大学附属北京安贞医院风湿免疫科治疗的白塞综合征患者20例的临床及影像学检查资料.20例患者中,男4例,女16例,平均年龄41.2岁,平均病程17.0年.超声、CT及MR检查发现心血管系统受累13例,主要表现为主动脉瓣脱垂并重度关闭不全,主动脉瘤、主动脉假性动脉瘤、主动脉溃...     

青藤碱渗透不同动物皮肤的行为研究

目的 :建立青藤碱的透皮吸收研究方法 ,比较青藤碱渗透小鼠皮肤、裸鼠皮肤、家兔皮肤、大鼠皮肤、猪耳皮肤及人体皮肤的透皮吸收行为。方法 :青藤碱的含量测定采用HPLC法 ,计算透皮速率常数J,比较青藤碱渗透上述 6种实验皮肤的透皮速率常数。结果 :青藤碱透过 6种皮肤的透皮速率常数分别为 46 6 7± 16 35、40 34± 8 40、17 6 0± 9 46、2 3 71± 8 79、44 5 6± 11 2 7、38 33± 13 81。结论 :青藤碱对 6种皮肤的渗透性 ,以裸鼠及猪耳皮肤的透皮速率常数与人体皮肤较为接近。     

子宫内膜癌磁共振成像诊断和分期

回顾性分析子宫内膜癌的磁共振（MRI）表现和手术病理结果，探讨MRI诊断和分期的价值。材料和方法：18例子宫内膜癌诊断和分期均经手术和病理检查。术前MRI检查采取冠状面和矢状面的T1WI和T2WI成像，双盲法MRI阅片，子宫内膜癌MRI分期基本按FIGO分期原则。结果：病灶区在T1WI像上为等信号（不伴出血），T2WI呈现5种表现。MRI分期准确率达83．8％，分辨工期的准确率达90．9％。结论：子宫内膜癌MRI表现多样化，有44．4％病例表现不典型。MRI对子宫内膜癌（尤其对占多数的Ⅰ期病例）的分期具有很高的价值。