Mechanical analysis of cuff tear arthropathy during multiplanar elevation with the AnyBody shoulder model

Background

This numerical study analysed the mechanics of cuff tear arthropathy with the AnyBody shoulder model.

Methods

The model simulated three frequent characteristics of cuff tear arthropathy: A supero-posterior massive rotator cuff tear, a proximal and static migration of the humeral head, and a contact between the humeral head and the scapula (glenoid &; acromion) with friction. The mechanics of the cuff tear arthropathy with and without friction were studied by analysing: the mechanics of the deltoid (i.e. length &; strength), the gleno-humeral and acromio-humeral contact forces, the friction moment, and the maximum elevation angle. Elevations in the frontal, scapular and sagittal planes were simulated.

Findings

Compared to an intact condition, the cuff tear arthropathy model without friction estimated a deltoid strength of − 18% (frontal = − 13%, scapular = − 17%, sagittal = − 25%), a gleno-humeral contact force of − 34% (frontal = − 60%, scapular = − 46%, sagittal = + 5%), estimated an acromio-humeral contact force of 240 N (frontal = 213 N, scapular = 184 N, sagittal = 324 N) and a maximum elevation angle of 77° (frontal = 80°, scapular = 87°, sagittal = 65°). Contact friction enhanced this behaviour, decreasing even more the gleno-humeral contact force and the maximum elevation angle, while increasing the acromio-humeral contact force.

Interpretation

This novel cuff tear arthropathy model suggests that friction and plane of elevation greatly influence the mechanics of the shoulder with cuff tear arthropathy. It also shows that the AnyBody simulation tool may be useful to study musculoskeletal pathologies and not only normal conditions.     

Friction and shear highly associated with pressure ulcers of residents in long‐term care – Classification Tree Analysis (CHAID) of Braden items

Aims Among various risk assessment scales for the development of pressure ulcers in long‐term care residents that have been published in the last three decades, the Braden scale is among the most tested and applied tools. The sum score of the scale implies that all items are equally important. The aim of this study is to show whether specific items are of greater significance than others and therefore have a higher clinical relevance. Design Data analysis of six pressure ulcer prevalence studies (2004–2009). Methods A total of 17 666 residents (response rate 79.6%) in 234 long‐term care facilities participated in 6 annual point prevalence studies that were conducted from 2004 to 2009 throughout Germany. For the classification of the sample regarding pressure ulcers as a dependent variable and the Braden items as predictor variables, Chi‐square Automatic Interaction Detector (CHAID) for modelling classification trees has been used. Results Pressure ulcer prevalence was 5.4% including pressure ulcer grade 1 and 3.4% for pressure ulcer grades 2–4. CHAID analysis for the classification tree provided the item ‘friction and shear’ as the most important predictor for pressure ulcer prevalence. On the second level, the strongest predictors were ‘nutrition’ and ‘activity’ and on the third level they were ‘moisture’ and ‘mobility’. Residents with problems regarding ‘friction and shear’ and poor nutritional status present with an 18.0 (14.8) pressure ulcer prevalence which is 3–4 times higher than average. Conclusion CHAID analyses have shown that all items of the Braden scale are not equally important. For residents in long‐term care facilities in Germany, the existence of ‘friction and shear’ as a potential and especially as a manifest problem has had the strongest association with pressure ulcer prevalence.     

多参数监护仪的质量检测和故障分析

多参数监护仪可连续长时间地监测病人的重要生命特征参数,为抢救病人提供第一手临床信息资料和多种生命特征参数,被广泛地应用于各医疗机构中。本文简要介绍了多参数医用监护仪中心电、无创血压和血氧饱和度几个性能参数的测量原理和检测方法,分析了检测过程中常见的故障及处理方法。     

CS-160型高速涡轮牙钻机故障检修一例

针对高速涡轮牙钻机在教学使用中出现的一次压缩机卡缸故障,进行分析和检修,总结设备损坏的原因和设备使用及操作的注意事项。     

Adaptive fault tolerant control design for Takagi–Sugeno fuzzy systems with interval time‐varying delay

This paper deals with the problem of fault‐tolerant control (FTC) of continuous‐time Takagi–Sugeno fuzzy systems with interval time‐varying delay by using adaptive observer. Through constructing an appropriate type of Lyapunov function, a delay‐dependent criterion is established to reduce the conservatism of designing an active FTC (AFTC). In comparison with the existing techniques in the literature, the proposed approach simplifies the design of an AFTC and gives in only one step of the estimate of state vector, the estimate of actuator fault and the controller gains. Some simulation examples are included to demonstrate the effectiveness of the proposed approach. Copyright © 2013 John Wiley & Sons, Ltd.     

Required coefficient of friction during level walking is predictive of slipping

The required coefficient of friction (RCOF) is frequently reported in the literature as an indicator of slip propensity. This study aimed to further develop slip prediction models based on RCOF by examining slips under moderately slippery conditions where the RCOF was approximately equal to the available coefficient of friction. Baseline RCOFs were found for normal walking trials and then an unexpected slip was introduced with a moderately slippery boot-floor contaminant combination for thirty-one subjects. Slip outcomes (i.e., whether a subject experienced a slip) were assessed based on the displacement of a marker placed on the heel. A logistic regression analysis was used to model the impact of RCOF on slipping. Results showed that subjects who walked with a greater RCOF were found to have a higher probability of slipping. The predicted probability of a slip across the RCOF ranged from 3% to 95% and an increase of 0.01 in RCOF was associated with a slipping odds ratio of 1.7. Thus, modest differences in RCOF can have a dramatic impact on slip propensity. This study shows that RCOF can be a sensitive and valid predictor of slipping in realistic frictional environments.     

Influence of the Punch Speed on the Die Wall/Powder Kinematic Friction During Tableting

Influence of the compaction speed on the final tablet properties is an important challenge during the scale-up of a solid dosage form. This strain rate sensitivity is generally attributed to the time dependent deformation behavior of the powder. In this work, we studied the influence of the speed on another important factor during compaction: friction between the tablet/powder and the die. An original experimental methodology was developed to study the evolution of the kinematic friction coefficient between the tablet and the die as a function of the sliding speed of the tablet on the die wall. This methodology made it possible to separate the speed used to make the tablet from the speed used to measure the friction coefficient. Results indicate that the kinematic coefficient of friction increases with the sliding speed following a logarithmic trend. This trend was observed for 4 different pharmaceutical excipients. Moreover, it was proved that the speed dependency is an intrinsic property of the friction between a tablet and a die lubricated using magnesium stearate.     

A Comprehensive Study about the Role of Crosslink Density on the Tribological Behavior of DLC Coated Rubber

The friction and wear behavior of coated rubber components is strongly dependent on the substrate properties. This work deals with the impact of the crosslink density, i.e., the hardness of the rubber substrate on the tribological performance of uncoated and coated rubber. The hardness of nitrile butadiene rubber (NBR) is varied altering the sulfur content. Both the uncoated and coated rubber samples are characterized in terms of surface and mechanical properties. Tribological tests comprise the examination of the macroscopic contact area and the temperature in the contact zone. It was found that the functional layer enhances the wear resistance significantly. Apparently, the wear and friction behavior of the coated rubber correlates with the hardness and the bulk properties of the substrate material.     

直线电机滑台摩擦特性和摩擦模型

为了提高直线电机在高速、高加速工况下的运动精度,需要对直线电机滑台的摩擦特性进行研究。本文通过直线电机实验台研究了加速度和速度对摩擦力的影响。实验结果表明：加速度越大,预滑动阶段结尾处的临界摩擦力也越大;加速度越大,混合润滑区摩擦滞后现象越显著,使得Stribeck曲线出现后移;在高速运动下,黏滞摩擦力并不随速度呈线性变化,黏滞摩擦因子会随着速度增加而逐渐减小。针对这些摩擦特性,提出了考虑加速度影响的Stribeck二元摩擦模型。结合实验数据辨识出了模型参数并通过对比其他工况下的实验数据和模型预测值,验证了Stribeck二元模型的有效性。     

格列本脲改善小鼠局灶性脑缺血再灌注损伤后期的神经运动功能障碍

目的:研究格列本脲对脑缺血再灌注损伤小鼠后期神经运动功能障碍的影响?方法:应用C57BL/6小鼠,制备局灶性脑缺血再灌注损伤模型,经灌胃给予格列本脲(20 mg/kg)连续治疗5周,每周监测小鼠的空腹血糖与体重变化?通过角测试?圆柱体测试?转棒实验及踏空实验等观察小鼠的行为学改变,免疫组织化学染色法观察缺血脑区星形胶质细胞的变化?结果:格列本脲(20 mg/kg)连续治疗5周,不影响小鼠的空腹血糖;与对照组比较,从治疗第2周开始,能显著增加小鼠的体重(P < 0.01);从治疗第3周开始,能减少踏空实验中小鼠的足失误率(P < 0.05)及延长转棒实验中的棒上停留时间(P < 0.05),并减少缺血脑区胶质瘢痕的形成范围(P < 0.05)?结论:格列本脲连续治疗能够促进小鼠脑缺血再灌注损伤后期神经运动功能的恢复?