人体颞下颌关节盘拉伸力学特性研究

通过对４具新鲜尸体的５个颞颌关节盘共８０个试件进行不同应变水平下的应力松弛试验和等应变速度下的拉伸破坏试验，测定了关节盘的横向拉伸力学性质，用拟线性粘弹性理论和二相理论对实验结果进行分析并建立了组织的本构方程。结果表明：关节盘的生理二相区在５％应变内；盘前带的横向拉伸强度、拉伸模量和破坏能量大于中间带和后带，中、后带差异不大；盘的应力松弛程度较低，初始应力松弛率在８％～１５％左右。同时证明，在较低应变下可以用获取的本构方程模拟关节盘的流变学特性     

Probabilistic analysis of peri-implant strain predictions as influenced by uncertainties in bone properties and occlusal forces

OBJECTIVES: The purpose of this study was to examine the influence of variability in bone properties and loading on peri-implant crestal and cancellous bone strains using a probabilistic approach, in combination with finite element (FE) analysis. MATERIAL AND METHODS: Oblique occlusal loading was applied to a single endosseous implant embedded in a two-dimensional (2-D) FE model of a premolar section of a mandible. Perfect bonding was assumed at all interfaces. Five independent parameters (cortical bone thickness (T), cortical (ECORT) and cancellous (ECANC) bone Young's moduli, and vertical (FVERT) and horizontal (FHOR) occlusal forces) were assigned statistical distributions based on data in the literature. Two cancellous bone distribution models were examined, one with a lower mean and range (LM) and the second with a higher mean and range (HM) of cancellous bone Young's modulus values. Sets of randomly chosen values for the five parameters were selected from the distributions and FE analyses were performed for all randomly selected sets. RESULTS: In the LM model, 50% of the cases experienced hyper-physiologic peri-implant crestal strains in the region of commonly reported saucerization, compared with about 25% of the cases in the HM model. Relative probabilistic sensitivities (%) of bone strains to the independent input parameters (T, ECORT, ECANC, FVERT and FHOR) were as follows: 29, 11, 30, 13, and 17 for the LM model, and 17, 11, 35, 21, and 15 for the HM model, respectively. CONCLUSION: Probabilistic analyses of FE models suggest that up to twice as many cases in the LM distribution may be at risk of saucerization as compared with the HM distribution model. Although based on hypothetical distribution values and the limitations inherent to a 2-D analysis, this probabilistic study demonstrated that FE models are very sensitive to the often arbitrarily assigned values for cancellous bone Young's modulus, and also to values used for cortical bone thickness, when the cancellous bone modulus is low.     

弹性应变率比值联合乳腺超声影像报告和数据系统诊断乳腺结节的应用价值

目的 探讨弹性应变率比值(SR)与乳腺超声影像报告和数据系统(BI-RADS-US)联合诊断乳腺结节的应用价值。方法 回顾性分析经病理确诊的471例乳腺结节,术前行常规超声及应变弹性成像检查,应用SR联合BI-RADS-US对乳腺结节分类进行分级调整,以病理结果为金标准,通过受试者工作特征(ROC)曲线下面积评估联合法与BI-RADS-US单独诊断乳腺结节的效能,比较两者敏感度、特异度及准确性。结果 471例乳腺结节中,良性180例,恶性291例,联合法诊断乳腺癌的ROC曲线下面积明显高于BI-RADS-US(0.798比0.730;Z=2.583,P=0.010)。SR法、BI-RADS-US及联合法诊断乳腺癌的敏感度分别为86.6%、99.0%、96.6%,特异度分别为67.2%、47.2%、63.3%,准确性分别为79.2%、79.2%、83.9%。联合法较BI-RADS-US单独诊断乳腺癌特异度从47.2%提高到63.3%(χ ²=14.25,P<0.001),将57.5%(42/73)BI-RADS 4A类中的良性结节降为3类。结论 SR联合BI-RADS-US可明显提高乳腺癌的诊断效能,提高诊断特异度,避免不必要的穿刺活检。     

心血管磁共振特征追踪技术诊断早期高血压性心脏病

目的探讨心血管磁共振特征追踪(CMR-FT)技术对早期高血压性心脏病(HHD)的诊断价值。方法选取54例HHD患者,其中26例左心室射血分数(LVEF)≤50%(LVEF≤50%组),28例LVEF>50%(LVEF>50%组);另选40名健康志愿者作为对照组。行心血管磁共振(CMR)检查,检测各项心功能参数及整体纵向应变(GLS)。结果3组间左心室舒张末期容积(LVEDV)、左心室收缩末期容积(LVESV)、每搏输出量(SV)、LVEF、心输出量(CO)、心指数(CI)、心率(HR)、左心室收缩期质量及舒张期质量、GLS差异均有统计学意义(P均<0.05)。GLS与LVEDV、LVESV、HR、左心室收缩期质量及舒张期质量均呈正相关(r=0.340、0.460、0.284、0.640、0.570,P均<0.01),与SV、LVEF、CO、CI均呈负相关(r=-0.223、-0.516、-0.052、-0.260,P均<0.05)。结论CMR-FT可用于评估左心室功能,有助于早期诊断HHD。     

Characterization and evolution of the coronavirus porcine epidemic diarrhoea virus HLJBY isolated in China

A strain of porcine epidemic diarrhoea virus (PEDV), namely HLJBY, was isolated in Heilongjiang province, China. To provide insight into the understanding of the phylogenetic and the current epidemiological status of PEDV, PEDV HLJBY was compared with CV777 and other PEDV strains deposited in the GenBank. The homology between the entire genomic nucleotide sequences of PEDV HLJBY and CV777 was 97.7%. The homology of M gene was the highest (99.0%). However, the homology of ORF3 gene was 97.7%, and protein of ORF3 was 90.1%. In addition, HLJBY showed the highest nucleotide identity (99.9%) with PEDV‐SX/China/2017 strain and lowest similarity (91.2%) to PEDV/Belgorod/dom/2008 strain. We analysed the changes in S gene and its protein of PEDV HLJBY with 65 historic PEDV strains. The highest nucleotide identity was 99.9% compared with PEDV‐SX/China/2017 strain, and the lowest nucleotide identity was 60.0% compared with PEDV/Belgorod/dom/2008 strain. The length of deduced amino acid sequences of S proteins varied from 1,372 to 1,390 amino acids (aa). Compared with most aa sequences of S proteins, HLJBY exhibited 5 aa deletions (position 55, 59–61, 144). Analysis and comparison of open reading frame 3 (ORF3) proteins between HLJBY strain and other PEDV strains were also focused in this study. We revealed that the length of deduced amino acid sequences of ORF3 proteins was 80–224 aa among tested strains and the identity of HLJBY ORF3 amino acids with other PEDV strains was 71.4%–98.9%. ORF3 protein of both HLJBY strain and PEDV‐SX/China/2017 strain consists of 91 aa, with 133 aa deletions at their C' end in relation to the other tested PEDV strains. The phylogenetic tree based on different proteins or genes resulted in different phylogenetic groups. For pathogenicity evaluation of PEDV HLJBY strain, colostrum deprivation piglets were challenged with PEDV HLJBY, and PEDV reference strain CV777 as a control, the results showed that animals challenged with either of these PEDV strains developed diarrhoea, and histopathological examination of small intestines of challenged animals showed acute viral enteritis with villous atrophy in either PEDV HLJBY‐P10 or PEDV CV777‐P8 inoculated piglets.     

Marek's disease viruses circulating in commercial poultry in Italy in the years 2015–2018 are closely related by their meq gene phylogeny

Marek's disease (MD) is a lymphoproliferative disease important to the poultry industry worldwide; it is caused by Gallid alphaherpesvirus 2 (GaHV‐2). The virulence of GaHV‐2 isolates has shifted over the years from mild to virulent, very virulent and very virulent +. Nowadays the disease is controlled by vaccination, but field strains of increased virulence are emerging worldwide. Economic losses due to MD are mostly associated with its acute form, characterized by visceral lymphomas. The present study aimed to molecularly classify a group of 13 GaHV‐2 strains detected in vaccinated Italian commercial chicken flocks during acute MD outbreaks, and to scrutinize the ability of predicting GaHV‐2 virulence, according to the meq gene sequence. The full‐length meq genes were amplified, and the obtained amino acid (aa) sequences were analysed, focusing mainly on the number of stretches of four proline molecules (PPPP) within the transactivation domain. Phylogenetic analysis was carried out with the Maximum Likelihood method using the obtained aa sequences, and the sequences of Italian strains detected in backyard flocks and of selected strains retrieved from GenBank. All the analysed strains showed 100% sequence identity in the meq gene, which encodes a Meq protein of 339 aa. The Meq protein includes four PPPP motifs in the transactivation domain and an interruption of a PPPP motif due to a proline‐to‐serine substitution at position 218. These features are typically encountered in highly virulent isolates. Phylogenetic analysis revealed that the analysed strains belonged to a cluster that includes high‐virulence GaHV‐2 strains detected in Italian backyard flocks and a hypervirulent Polish strain. Our results support the hypothesis that the virulence of field isolates can be suggested by meq aa sequence analysis.     

A potential endemic strain in China: NADC34‑like porcine reproductive and respiratory syndrome virus

Porcine respiratory and reproductive syndrome virus (PRRSV) causes an economically important disease affecting commercial pork production worldwide. NADC34‐like PRRSV has had a strong impact on the U.S. and Peruvian pig industries in recent years and also emerged in northeastern China in 2017. However, the endemic status of NADC34‐like PRRSV in China is unclear. In this study, we examined 650 tissue samples collected from 16 Provinces in China from 2018 to 2019. Six NADC34‐like PRRSV strains were detected in samples from three Provinces, and the complete genomes of four of these strains were sequenced. Phylogenetic analysis showed that these novel PRRSV strains belong to sublineage 1.5 (or NADC34‐like PRRSV), forming two groups in China. Sequence alignment suggested that these novel strains share the same 100‐aa deletion in the Nsp2 protein that was identified in IA/2014/NADC34 isolated from the United States in 2014. Recombination analysis revealed that five of eight complete genome sequences are derived from recombination between IA/2014/NADC34 and ISU30 or NADC30. The number and distribution of NADC34‐like PRRSVs is increasing in China. Importantly, compared with the currently endemic strain NADC30‐like PRRSV, NADC34‐like PRRSV has the potential to be an endemic strain in China. This study will help us understand the epidemic status of NADC34‐like PRRSV in China and provide data for further monitoring this type of PRRSV in China.     

Relative stiffness, transverse displacement and dynamization in comparable external fixators

Several unilateral external fixators were laboratory tested under applied axial, bending, and torsional loads. In certain cases the shear movement at the fracture site was substantial, up to 4 mm, and in all cases it was as significant as axial displacement. Also, under average full weight bearing, all the fixator/bone screw frameworks will allow too much axial movement at the fracture. This could inhibit healing and cause peak bone and screw stresses to approach yield.     

大学生自杀意念的外在保护因素分析

目的:分析在校大学生预防自杀意念的外在保护因素。方法:采用分层抽样、三阶段抽样等方法,应用NCS-R自杀意念量表,对某北京高校两个学年的大学生(n=1256)的学习与生活状况进行调查,并进行logistic回归分析。结果:在校大学生有自杀意念的有173人(占13.77%);积极参加班级活动、经常参加体育锻炼等则是大学生群体减少自杀意念的保护因素,差异有统计学意义(均P<0.05)。结论:积极参加班级课外活动及体育锻炼对预防自杀意念有正向影响,建议作为大学生自杀预防的外在保护因素而加以重视。