Investigation of Technological and Load Intensity Parameters of the Finishing Process of Materials on Equipment with Tools Translational Kinematics

The regularities of the formation of the resulting raster tool trajectories based on Lissajous figures for the lapping process of planes are established. This makes it possible to maximize the cutting ability of the tool, which contributes to its more uniform wear and increased productivity and processing quality. Optimal parameters of productivity and roughness of the treated surface during lapping of zirconium ceramics are achieved through the use of ASM paste 28/20 µm. Based on Preston’s hypothesis, an exponential dependence of the change in the contact area during the lapping of planes of different initial shape of the macrorelief is obtained. The obtained theoretical and practical results of the study of the process of flat lapping with constant and variable clamping force of the treated surface to the surface of the tool. The influence of the force factor on the formation of the surface in the process of abrasive lapping has been established. Studies have been carried out and the main technological recommendations of precision surface treatment of workpieces based on hard, brittle ceramic material and bronze samples on equipment with a raster trajectory of the tool movement are presented. The optimal pressure value when processing ceramics should be considered 203–270 kPa (2.1–2.8 kg/cm²).     

Experimental Study on Self-Centering Performance of the SMA Fiber Reinforced ECC Composite Beam

The combination of superelastic shape memory alloy fibers and ECC materials can form a new SMA fiber reinforced ECC composite material (SMAF-ECC) with good self-centering performance. In order to study the self-centering performance of the new composite material, 6 groups of pre-notch beam specimens were made for three-point bending cyclic loading tests, and the failure phenomenon, hysteresis curve, self-centering effect and influencing factors of the specimens were analyzed. The research results show that when the SMA fibers are effectively anchored in the ECC matrix, the SMA fibers can exert the superelastic properties to provide the ECC beams with recoverying force, and realize the crack self-closure and deflection self-recovery function for the beams, with the minimum residual crack width and deflection is only 0.9 mm and 1.3 mm respectively. Increasing fiber content can cause a small increase in the self-centering ability of the beams. However, only when the fiber diameter is appropriate, better self-centering effect can be achieved, but the difference caused by fiber diameter in the test was only 5%. SMA Fiber end forms have significant influence on self-centering performance. The knotted end beam can get a more than 70% self-centering ratio, while the straight end beams and bended end beams have no self-centering ability. The research results provide important reference for the research and application of this new self-centering materials and their structures.     

郑州地区支气管哮喘的病因学和临床实验研究

目的：进行郑州地区支气管哮喘的病因学和临床实验研究。方法：通过曝片调查本地区气传致敏花粉散布规律；经皮试了解致敏原与哮喘发病的关系；采用ＥＬＩＳＡ法测定不同病型、病期哮喘病人的血清ＩｇＥ水平；检测实验性哮喘豚鼠血和肺组织ＬＰＯ、ＳＯＤ水平变化及ＰＧＥ１和氨茶硷的影响，并对２例顽固性哮喘患者静脉点滴ＰＧＥ１观察疗效。结果：郑州地区空气中全年均有花粉散布并出现两次飘散高峰，导致哮喘的季节性发病或加重。９０９％的外源性哮喘患者皮试阳性，花粉、霉菌、屋尘和螨为主要致敏原。外源性哮喘及发作期患者血清ＩｇＥ水平明显高于内源性哮喘及缓解期病人。ＰＧＥ１能抑制哮喘豚鼠肺组织ＬＰＯ水平升高，对顽固性哮喘患者静脉点滴ＰＧＥ１疗效显著。结论：支气管哮喘与花粉飘散及致敏原消长密切相关，血清ＩｇＥ含量肺组织ＬＰＯ水平的升高对支气管哮喘发病有重要意义。ＰＧＥ１对治疗顽固性哮喘是一种具有发展前景的药物。     

声辐射力脉冲成像技术在评价肝纤维化程度的临床价值

目的分析声辐射力脉冲成像技术(acoustic radiation force impulse,ARFI)在评价慢性肝病患者肝纤维化程度中的临床价值。方法利用声辐射力脉冲成像技术对61例慢性肝病患者和56例正常人肝脏右叶进行检查,测得感兴趣区肝脏组织弹性量化值,即声触诊组织量化值(virtual touch quantification,VTQ),并与肝脏穿刺病理结果相对照。结果①61例慢性肝病患者病理活检结果:S0期8例,S1期12例,S2期10例,S3期13例,S4期18例;②VTQ值与肝纤维化程度有很好的相关性(Spearman r=0.737,P<0.01),不同阶段肝纤维化VTQ平均值是,正常对照组=1.03±0.26,S0=1.05±0.20,S1=1.14±0.28,S2=1.36±0.45,S3=2.01±0.76,S4=2.43±0.39;③正常对照组与S0组与S1组之间、S0组与S1组之间的VTQ值差异无统计学意义(P>0.05),其他各组之间的VTQ值差异均有统计学意义(P=0.000或P=0.016)。结论声脉冲辐射力成像技术能够反映肝组织弹性硬度的定量性息,对评估肝纤维化程度有重要价值。     

Share control of surgery robot master manipulator guiding tool along the standard path

Recently, minimally invasive surgery (MIS) robotics enters the phase of autonomous operation. However, because of the high variability of the environment, conducting a fully autonomous surgery is still extremely difficult. This paper presents a share control system, the objective of which is to suggest the optimum path of tool guidance through the use of force on the master manipulator (hereinafter as master), meaning the surgeon's hand. Owing to this type of control, the surgeon has full control over the position of the tool the entire time and is supported by the system to better and faster guide the tool during surgery. The force should be felt by the surgeon but, simultaneously, must not hinder or impact the surgical process. Furthermore, the share control system presented in the paper can be turned on or off at any moment during surgery.     

Age related differences in maximal and rapid torque characteristics of the leg extensors and flexors in young,middle-aged and old men

The decline in maximal and rapid isometric torque characteristics may compromise functional living abilities in aging adults while loco-motor muscle groups, such as the leg extensors and flexors, may exhibit different torque–time age related decreases. The purpose of the present study was to examine the age-related differences in maximal and rapid torque characteristics of the leg extensor and flexor muscle groups in young, middle-aged, and old men. Sixty-five healthy men were categorized by age as young (n = 25; mean ± SD age = 24.9 ± 3.0 years), middle-aged (n = 22; age = 50.6 ± 4.0 years), and old (n = 18; age = 66.8 ± 4.5 years). Participants performed maximal voluntary contractions (MVCs) of the leg extensors and flexors and an estimated thigh cross sectional area (eThighCSA) assessment. Peak torque (PT), peak rate of torque development (RTDpeak), absolute RTD and the contractile impulse (IMPULSE) were calculated at time intervals of 30, 50, 100 and 200 ms from the torque–time curve. Relative RTD was calculated at 10, 20, 30, 40 and 50% of MVC from the normalized torque–time curves. PT, RTDpeak and later rapid torque variables (RTD100, RTD200, and IMPULSE200) were greater (P ≤ 0.05) in the young and middle-aged when compared to the old men for both muscle groups. Early (RTD30,50; IMPULSE30,50) and late (IMPULSE100) rapid torque variables were greater (P ≤ 0.05) for the young and middle-aged than the old men for the leg extensors but not the leg flexors, except for RTD30, in which there was no difference between young and old. There were no differences for all relative RTD variables between age groups (P > 0.05). eThighCSA was lower in the old compared to the young (P = 0.001) and middle-aged (P = 0.016) men. Maximal and rapid torque characteristics were preserved in middle-aged men but greatly reduced in older men with differential effects at early and late portions of the torque–time curve between the leg extensors and flexors. Significant decreases in absolute maximal and rapid torque production with no change in relative RTD across age groups and lower eThighCSA in old men may suggest that the loss of rapid torque producing capacities observed in older men may be largely a function of mechanisms associated with loss of muscle strength and muscle mass.     

Ideal,catch, and slip bonds in cadherin adhesion

Classical cadherin cell-cell adhesion proteins play key morphogenetic roles during development and are essential for maintaining tissue integrity in multicellular organisms. Classical cadherins bind in two distinct conformations, X-dimer and strand-swap dimer; during cellular rearrangements, these adhesive states are exposed to mechanical stress. However, the molecular mechanisms by which cadherins resist tensile force and the pathway by which they convert between different conformations are unclear. Here, we use single molecule force measurements with an atomic force microscope (AFM) to show that E-cadherin, a prototypical classical cadherin, forms three types of adhesive bonds: catch bonds, which become longer lived in the presence of tensile force; slip bonds, which become shorter lived when pulled; and ideal bonds that are insensitive to mechanical stress. We show that X-dimers form catch bonds, whereas strand-swap dimers form slip bonds. Our data suggests that ideal bonds are formed as X-dimers convert to strand-swap binding. Catch, slip, and ideal bonds allow cadherins to withstand tensile force and tune the mechanical properties of adhesive junctions.