关键词： 胶原纤维   分子动力学模拟   点突变   成骨不全症   机械性能  

摘要： 现代人对胶原机械性能和结构的理解程度，对于生物医学材料以及纳米技术的应用至关重要。而且，点突变与许多胶原类疾病有关，其中包括成骨不全症（OI）。我们进行一系列传统研究以及能够操纵原子的分子动力学模拟，以便检测点突变对于胶原纤维结构和机械性能的影响，包括甘氨酸到丙氨酸，天冬氨酸，半胱氨酸和丝氨酸的突变以及羟脯氨酸到精氨酸，天冬酰胺，谷酰胺和赖氨酸的突变。

关键词： 高压输电线路   机械手   动力学分析  

摘要： 高压输电线路长期暴露在外,不可避免地会产生输电线路故障,需及时发现、维修。本方案是配套500 kV六分裂输变线路高压特种作业机器人的高压特种作业机械手,对其进行动力学分析仿真。在建立SimMechanics机械手模型的基础上分别进行正向动力学分析和逆向动力学分析。借助Mat-lab图形方式生成机械手系统的三维动画。

关键词： Mg2Ni-based compounds   Mechanical alloying   X-ray diffraction   Hydrogen absorption kinetic   Annealing treatment  

摘要： Mg2Ni-based compounds were prepared using a high-energy milling technique, with a planetary ball mill, and subsequent annealing at 350 degrees C. X-ray diffraction analyses revealed that Mg2Ni phase was obtained after 10 milling hours, in addition to Ni phase. Increasing the ballmilling duration from 10 to 17 h causes a decrease in the crystal size of particles from 93 to 76 nm. However, the subsequent annealing of all Mg2Ni-based materials highly increases their crystallite sizes with calculated values in the range of 261-235 nm. In the same way, X-ray diffraction patterns of annealed compounds show the presence of highly crystallized Mg2Ni phases. The particle size of Mg2Ni/Ni particles is estimated at 25 lm after 10 milling hours and drops to 5 lm at longer times. The scanning electron microscopy images of Mg2Ni/Ni particles demonstrated a drastic increase of their sizes up to 100 lm upon annealing. The hydrogenation reactivity and kinetic of Mg2Ni/Ni were both characterized by solid-gas reactions. The hydrogen absorption capacity value was about 3.5 H/f. u for milled and annealed Mg2Ni/Ni compound. The highest hydrogen absorption kinetic was obtained during the first 5 h of absorption time, where 95 % of the maximum absorption capacity was reached.

关键词： Medical Contraindication   Implants and Prostheses   Pulmonary Artery   Left Ventricular Assist Device   Invasive hemodynamic monitoring   Right heart cardiac catheterization   Cannulation   PVR gene   Right Atrium  

摘要： "Fixed" pulmonary hypertension (PH), defined as a mean pulmonary artery pressure (PAP) > 25 mm Hg, a pulmonary vascular resistance (PVR) >2.5 Wood units (WU) and a transpulmonary gradient (TPG) > 12 mm Hg after pharma-cologic manipulation, is a contraindication for heart transplantation (HTx).1 Long-term mechanical unloading with a left ventricular assist device (LVAD) has been shown to lower PVR and reverse fixed PH,2^ converting seemingly ineligible patients into potential transplant candidates. In this population, serial invasive assessment of pulmonary hemodynamics is of utmost importance. However, whereas PAP can still be measured accurately by right heart catheterization after LVAD implantation, this is not the case in patients with a biventricular assist device (biVAD) due to cannulation of the right atrium and the pulmonary artery.

关键词： cross-linking   riboflavin   nonlinear optics   cornea   keratoconus  

摘要： In this study we test the hypothesis that nonlinear optical (NLO) multiphoton photoactivation of riboflavin using a focused femtosecond (FS) laser light can be used to induce cross-linking (CXL) and mechanically stiffen collagen as a potential clinical therapy for the treatment of keratoconus and corneal ectasia. Riboflavin-soaked, compressed collagen hydrogels are cross-linked using a FS laser tuned to 760 nm and set to either 100 mW (NLO CXL I) or 150 mW (NLO CXL II) of laser power. FS pulses are focused into the hydrogel using a 0.75 NA objective lens, and the hydrogel is three-dimensionally scanned. Measurement of hydrogel stiffness by indentation testing show that the calculated elastic modulus (E) values are significantly increased over twofold following NLO CXL I and II compared with baseline values (P < 0.05). Additionally, no significant differences are detected between NLO CXL and single photon, UVA CXL (P > 0.05). This data suggests that NLO CXL has a comparable effect to conventional UVA CXL in mechanically stiffening collagen and may provide a safe and effective approach to localize CXL at different regions and depths within the cornea. c The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

关键词： Hydrodynamics   Membrane bioreactor (MBR)   Membrane fouling   Particle image velocimetry (PIV)  

摘要： The influence of mechanically induced hydrodynamics on membrane fouling in a novel rotating flat-sheet membrane bioreactor (RFMBR) with the comparison of a common membrane bioreactor (CMBR) is analyzed here by the particle image velocimetry (PIV). Obtained results suggest that the fluid velocity has a slight impact on membrane fouling. With the increase in fluid velocity, the membrane fouling does not necessarily mitigate. In contrast, the variations in turbulence intensity have a great negative correlation with the changes in membrane fouling rate for both MBRs, which means that the turbulence induced by fluctuating velocities is helpful for the alleviation of membrane fouling. When comparing the membrane fouling between RFMBR and CMBR, it can be concluded that the membrane fouling rate for RFMBR is much slower compared to CMBR when consuming the same energy, indicating a more outstanding filtration performance of RFMBR.

关键词： Graphene   Collagen   MD simulation   Ripple   Pull-out force   Tissue engineering  

摘要： The reinforcement of biological polymers, such as collagen, with nanoscale fillers for use in tissue engineering and regenerative medicine is a promising research area that is just beginning to be explored. We study the mechanical properties of Type I collagen embedded with graphene nanoribbons (GNRs) as an important template employed in tissue repair. The graphene-collagen interfacial bonding properties play a significant role during load transfer in the nanocomposite and, hence, as the primary goal of this work, a set of pull-out studies, using molecular dynamics (MD) simulation, are performed to characterise the interfacial mechanical properties. The dependence of the pull-out force on the presence of ripples on the surface of the GNRs, arising due to thermal fluctuations, is also examined, as well as the influence of the pull-out velocity. (C) 2012 Elsevier B. V. All rights reserved.

关键词： Medical physics Biological physics  

摘要： We introduce a novel mechanistic model of the yield of tissue damage at the end of radiation treatment and of the subsequent healing kinetics. We find explicit expressions for the total number of functional proliferating cells as well as doomed (functional but non-proliferating) cells as a function of time post treatment. This leads to the possibility of estimating-for any given cohort of patients undergoing radiation therapy-the probability distribution of those kinetic parameters (e.g. proliferation rates) that determine times to injury onset and ensuing resolution. The model is suitable for tissues with simple duplication organization, meaning that functionally competent cells are also responsible for tissue renewal or regeneration following injury. An extension of the model to arbitrary temporal patterns of dose rate is presented. To illustrate the practical utility of the model, as well as its limitations, we apply it to data on the time course of urethral toxicity following fractionated radiation treatment and brachytherapy for prostate cancer.

关键词： Mechanical properties   Relaxation   Thermal history   Aluminosilicate glass  

摘要： One of the fundamental characteristics of glass is its brittleness. The recently experienced demand for stronger and more damage resistant glasses creates opportunities for fundamental studies of the mechanical properties as a function of thermal history. This is because the properties of glassy materials are not only determined by their chemical composition, but also by their thermal history due to the non-equilibrium nature of the glassy state. Hence, understanding the relaxation behavior of the mechanical properties of glass is of great scientific and technological importance. In this paper, we have investigated the thermal history dependence of Young's modulus, Vickers hardness, and cracking behavior for an alkaline earth aluminosilicate glass composition over a wide range of fictive temperatures (approximate to 130 K). Young's modulus, hardness, and brittleness index monotonically increase with decreasing fictive temperature, whereas the crack resistance decreases. We find that all of the mechanical properties appear to follow a common underlying stretched exponential relaxation behavior, with the stretching exponent beta(m) in the range from 0.30 to 0.49 close to the Phillips value of 3/7 for structural relaxation dominated by long-range interactions. (C) 2012 Elsevier B.V. All rights reserved.