A Non-Ersatz Material Approach for the Topology Optimization of Elastic Structures Based on Piecewise Constant Level Set Method

The topology optimization of a linearized elasticity system with the area (volume) constraint is investigated. A non-ersatz material approach is proposed. By introducing a fixed background domain, the linearized elasticity system is extended into the background domain by a characteristic function. The piecewise constant level set (PCLS) method is applied to represent the original material region and the void region. A quadratic function of PCLS function is proposed to replace the characteristic function. The functional derivative of the objective functional with respect to PCLS function is derived, which is zero in the void region and nonzero in the original material region. A penalty gradient algorithm is proposed. Four numerical experiments of 2D and 3D elastic structures with different boundary conditions are presented, illustrating the validity of the proposed algorithm.     

Feasibility assessment of shear wave elastography to lumbar back muscles

Low back pain is often associated with tensional changes in the paraspinal muscles detected by palpatory procedures. Shear wave elastography (SWE), recently introduced, allows the stiffness of muscles to be assessed noninvasively. The aim of this work was to study the feasibility of using SWE on the three main lumbar back muscles (multifidus, longissimus, and iliocostalis) in vivo after analyzing their muscular architecture ex vivo. We determined the orientation of fibers in the multifidus, longissimus, and iliocotalis muscles in seven fresh cadavers using gross anatomy and B‐Mode ultrasound imaging. We then quantified the stiffness of these three muscles at the L3 level ex vivo and in 16 healthy young adults. Little pennation was observed in the longissimus and iliocostalis, in which the direction of fibers was almost parallel to the line of spinous processes. The multifidus appeared as a multiceps and multipennate muscle. Given the random layering of millimetric fascicles, tendons, and fatty spaces, the multifidus had multiple fiber orientations. Muscular fascicles and fibers were oriented from 9° to 22° to the line of spinous processes. The shear moduli related to stiffness were 6.9 ± 2.7 kPa for the longissimus, 4.9 ± 1.4 kPa for the iliocostalis, and 5.4 ± 1.6 kPa for the multifidus. SWE is a feasible method for quantifying the stiffness of the lumbar back muscles. Clin. Anat. 30:774–780, 2017. © 2017Wiley Periodicals, Inc.     

Identification and estimation of single‐index models with measurement error and endogeneity

Economic variables are often measured with an error and may be endogenous. In this paper, we give new identification results for the ratio of partial effects in linear index models with measurement error and endogeneity. The identification restrictions include independence of covariates and error terms, and the derivative of some conditional mean functions being nonzero. We propose a local polynomial regression estimator to estimate the single‐index parameters. We apply these tools to estimate the labour‐supply elasticity and find that the labour‐supply elasticity for married men is positive, while the coefficients for married women are negative for the full sample and positive for the working sample.     

Correlation between 25-hydroxyvitamin D level and arterial elasticity in middle-aged and elderly cadres in Guiyang,China: A retrospective observational study

There is evidence that serum 25-hydroxyvitamin D [25-(OH) D] levels may be associated with cardiovascular disease and its risk factors. This study aimed to investigate the relationship between 25-(OH) D levels and blood pressure (BP), blood lipids, and arterial elasticity in middle-aged and elderly cadres in China.In this retrospective study, we included 401 civil servants and cadres aged >42 years who underwent medical examinations at Guiyang Municipal First People''s Hospital, China in 2018. The participants were assigned to deficiency (≤20 ng/mL), insufficiency (20–30 ng/mL), and sufficiency (≥30 ng/mL) groups according to 25-(OH) D levels in their blood. Demographics, brachial–ankle pulse wave velocity (baPWV), BP, ankle–brachial index (ABI), and blood lipids were compared among groups. The associations between 25-(OH) D and other parameters were evaluated using linear regression analysis.Median (range) 25-(OH) D levels in the deficiency (n = 162), insufficiency (n = 162), and sufficiency (n = 77) groups were 15.32 (2.93–19.88), 25.12 (20.07–29.91), and 33.91 (30.23–82.42) ng/mL, respectively. There were significant differences in systolic BP, pulse pressure, baPWV (left and right sides), ABI (left side), high-density lipoprotein-cholesterol, and triglycerides (TGs; all P < .05) among groups. Multivariate linear regression revealed that TG, left baPWV, and right baPWV were significantly negatively correlated with 25-(OH) D levels (all P < .05).In this study, 25-(OH) D levels were found to be associated with TG, left baPWV, and right baPWV values. 25-(OH) D deficiency may be associated with reduced arterial elasticity.     

Microscopic observation of chemical modification in sections using scanning acoustic microscopy

A scanning acoustic microscope (SAM) calculates the speed of sound (SOS) through tissues and plots the data on the screen to form images. Hard tissues result in greater SOS; based on these differences in tissue properties regarding SOS, SAM can provide data on tissue elasticity. The present study evaluated whether tissue modifications, such as formalin fixation, periodic acid‐Schiff (PAS) reactions and protein degradation, changed the acoustic properties of the tissues and whether SAM could be a useful tool for following chemical changes in sections. The fixation process was observable by the increased SOS. During the PAS reaction, the glycosylation of tissues was characterized by an increased SOS. Mucous or glycogen distribution was visualized and was found to be statistically comparable among lesions and states. Protease digestion by pepsin led to a decreased SOS. Tissue sensitivity to proteases varied due to the stage, cause and duration of inflammation or ageing. Changes in acoustic properties were more sensitive than those in optical histology. SAM facilitates the visualisation of the time course or distribution of chemical modifications in tissue sections, thus aiding their comparison among tissues. SAM may be an effective tool for studying changes such as protein cross‐linkage, tissue repair and ageing.     

实时二维剪切波弹性成像诊断自身免疫性肝病患者肝纤维化程度

目的评估实时二维剪切波弹性成像(2D-SWE)诊断自身免疫性肝病(AILD)患者肝纤维化程度的效能。方法回顾性分析102例AILD的临床2D-SWE资料。采用Kendall’s tau-b检验分析肝硬度测值(LSM)与肝纤维化分期、炎症分级的相关性;绘制受试者工作特征(ROC)曲线,以肝活体组织检查(LB)作为金标准,评估2D-SWE诊断各期肝纤维化的效能;以Logistic回归分析观察影响其诊断准确率的因素。结果LSM与纤维化分期呈正相关(r=0.58,P<0.01),与炎症分级无显著相关(r=0.29,P<0.01)。2D-SWE诊断≥F2期、≥F3期和F4期肝纤维化的ROC曲线下面积分别为0.93、0.86及0.86;截断值为8.10 kPa、10.20 kPa及13.50 kPa时,敏感度分别为89.16%、80.00%及88.46%,特异度分别为84.21%、76.60%及82.89%。对F4期肝纤维化,白蛋白是影响2D-SWE诊断准确率的独立影响因素(OR=1.10,P=0.01)。结论2D-SWE可评估AILD肝纤维化程度,对≥F2期诊断效能更优,且干扰因素较少。     

剪切波弹性成像用于肾脏疾病研究进展

作为超声新技术之一,超声弹性成像可无创简便地评估组织弹性及硬度。肾脏疾病进展过程中可能伴随肾脏实质硬度的改变。采用不同弹性成像方式可定量或半定量评价肾脏弹性及硬度的变化。本文对超声剪切波弹性成像用于肾脏疾病研究进展进行综述。