关键词： nanoimprint   lithography   anti-reflection   hot imprint   chalcogenide glass   optical fiber   mid-infrared   supercontinuum  

摘要： Thermal nanoimprinting is a fast and versatile method for transferring the anti-reflective properties of subwavelength nanostructures onto the surface of highly reflective substrates, such as chalcogenide glass optical fiber end faces. In this paper, the technique is explored experimentally on a range of different types of commercial and custom-drawn optical fibers to evaluate the influence of geometric design, core/cladding material, and thermo-mechanical properties. Up to32.4% increased transmission and 88.3% total transmission are demonstrated in the 2–4.3 μm band using a mid-infrared(IR) supercontinuum laser.

关键词： 动力学模型   优化算法   参数辨识  

摘要： 针对六自由度机械臂的动力学参数较多,一般需要多次辨识,且辨识精度有限问题,提出一种六自由度机械臂动力学动力学参数的一次性辨识方法。首先将六自由度机械臂的前后三个关节分为两部分,采用遗传算法分别优化设计激励轨迹信号,并进行动力学参数的一次性整体辨识,充分考虑了关节之间的耦合作用,消除了由于多次辨识实验所带来的实验条件不一致的误差。然后利用最小二乘法确定辨识参数的初值,避免了初值取值不当所带来辨识精度有限的问题。最后,通过设计动力学参数辨识实验,验证了所提方法的有效性。

关键词： MgH2   ZrH2 nanoparticles   Moderate conditions   Hydrogenation kinetics  

摘要： Magnesium hydride (MgH2) has attracted extensive attention over the past decades due to its highly reversible hydrogen storage density (7.6 wt%). But intrinsic high activation energy barriers for de/rehydrogenation of MgH2/Mg restrict its potential application as an on-board hydrogen carrier. Herein, ZrH2 nanocatalyst homogeneously distributed on the surfaces of MgH2 exhibits pronounced low temperature de/rehydrogenation kinetics, resulting from the vast lattice distortions between ZrH2 and MgH2/Mg phases. The ZrH2 doped MgH2 composite (MgH2-ZrH2) starts to release H-2 at 203 degrees C, 102 degrees C lower than that of undoped MgH2. Most importantly, MgH2-ZrH2 quickly absorbs 5.90 wt% H-2 at the temperature as low as 65 degrees C. Further deep investigations found that H atoms preferentially accumulates around ZrH2, since the lower hydrogen dissociation energy on the surfaces of ZrH2 (1.421 eV) than that of pure Mg (2.301 eV). Then, the large lattice disordered zone between ZrH2 and Mg phases enables H atoms diffuse easily into the lattice of Mg nearby, thus triggering the formation of MgH2. These findings are critically important to understand the mechanism of other metal hydride catalysts, as well as offer an opportunity for the practical on-board fuel cell applications in the future.

关键词： 右美托咪定   机械通气   镇静   血流动力学  

摘要： 目的:分析在有创机械通气患者治疗中应用不同剂量的右美托咪定所取得的镇静价值及对患者血流动力学的影响。方法:选取85例有创机械通气患者,随机将患者分成两组,对照组有42例患者,观察组有43例患者。对照组给予患者大剂量的右美托咪定治疗方法,观察组给予患者小剂量的右美托咪定治疗方法。结果:在T_(0)时间点,两组血压、心率对比,差异无统计学意义(P>0.05);在T_(1)、T_(2)、T_(3)时间点,两组血压、心率差异有统计学意义(P<0.05)。在T 0时间点,两组镇静评分差异无统计学意义(P>0.05);在T_(1)、T_(2)、T_(3)时间点,观察组镇静评分高于对照组,差异有统计学意义(P<0.05)。T 0时间点,两组相关指标差异无统计学意义(P>0.05);T_(1)、T_(2)、T_(3)时间点,两组相关指标差异有统计学意义(P<0.05)。结论:在有创机械通气患者治疗中,给予患者大剂量的右美托咪定治疗方法,血流动力学发生了较大幅度的变化,取得了良好的镇静效果。给予患者小剂量的右美托咪定治疗方法,血流动力学更为稳定,应在临床治疗中大力推广使用。

关键词： columnar polycrystal   compression test   FeCrNi alloy   mechanical properties   molecular dynamics simulation   plastic deformation  

摘要： In this work, mechanical properties and plastic deformation behaviors of columnar polycrystal are examined by compression tests using molecular dynamics simulation. The results show that anisotropic mechanical properties occur to the fcc FeCrNi samples with different inclined angles between the orientation of columnar grains and loading direction. The yield stress and flow stress of the alpha = 0 degrees sample are the highest, while the values of alpha = 45 degrees sample are the lowest among the tested samples. The reasons for these differences derive from the geometric constraint of grain boundaries (GBs) and the available slip systems of different grains. The GBs serve as obstacles where extended dislocations are incorporated rather than dislocation pile-ups at GBs. For the alpha = 0 degrees sample, the GBs bending toward the radius direction coupled with less partial dislocation motion and twinning compensates the compression strain. The strain-assisted GBs migration along loading direction extensively takes place in alpha = 90 degrees sample, whereas the numerous partial dislocation activity and GBs gliding occur in samples with the angle close to 45 degrees. This results from the higher Schmid factors of slip systems of columnar grains within these samples and long mean free sliding path for GBs gliding. Besides, the influence of radius size is probed, exhibiting a constant Young's modulus, but slightly different plastic deformation characteristics.

关键词： ionic block copolymer   molecular dynamics simulation   tension–   recovery  

摘要： Polymer electrolytes have attracted ever-increasing attention in the field of energy storage and conversion due to their significantly improved safety features and processability compared with liquid electrolytes and inorganic solid electrolytes. The mechanical integrity of ionic copolymers is one of the most important properties that need to be considered in the development of polymer electrolytes. In this study, the uniaxial tension-recovery studies are conducted in single-ion diblock copolymers via coarse-grained molecular dynamics simulation, where the fraction of the charged block is varied to form spherical, cylindrical, and lamellar morphologies. It is found that the dynamic hysteresis loss and permanent displacement have strong dependence on the fraction of the charged block and charge ratio. The change in the radius of gyration greatly varies for the different morphology. Furthermore, the charged copolymers are subjected to more changes in bond orientation during tension and also preserve more changes at recovery. It is likely that the charged monomers and counterions contribute to the stronger crosslinking effect in charged copolymers, reducing chain slippage and hysteresis loss.

关键词： Mitochondrial calcium dynamics   MCU complex   MICU 1/2/3   MCUR1   EMRE   Letm1   NCLX  

摘要： Mitochondria play vital role in regulating the cellular energetics and metabolism. Further, it is a signaling hub for cell survival and apoptotic pathways. One of the key determinants that calibrate both cellular energetics and survival functions is mitochondrial calcium (Ca2+) dynamics. Mitochondrial Ca2+ regulates three Ca2+ -sensitive dehydrogenase enzymes involved in tricarboxylic acid cycle (TCA) cycle thereby directly controlling ATP synthesis. On the other hand, excessive Ca2+ concentration within the mitochondrial matrix elevates mitochondrial reactive oxygen species (mROS) levels and causes mitochondrial membrane depolarization. This leads to opening of the mitochondrial permeability transition pore (mPTP) and release of cytochrome c into cytosol eventually triggering apoptosis. Therefore, it is critical for cell to maintain mitochondrial Ca2+ concentration. Since cells can neither synthesize nor metabolize Ca2+, it is the dynamic interplay of Ca2+ handling proteins involved in mitochondrial Ca2+ influx and efflux that take the center stage. In this review we would discuss the key molecular machinery regulating mitochondrial Ca2+ concentration. We would focus on the channel complex involved in bringing Ca2+ into mitochondrial matrix i.e. Mitochondrial Ca2+ Uniporter (MCU) and its key regulators Mitochondrial Ca2+ Uptake proteins (MICU1, 2 and 3), MCU regulatory subunit b (MCUb), Essential MCU Regulator (EMRE) and Mitochondrial Ca2+ Uniporter Regulator 1 (MCUR1). Further, we would deliberate on major mitochondrial Ca2+ efflux proteins i.e. Mitochondrial Na+/Ca2+/Li+ exchanger (NCLX) and Leucine zipper EF hand-containing transmembrane1 (Letm1). Moreover, we would highlight the physiological functions of these proteins and discuss their relevance in human pathophysiology. Finally, we would highlight key outstanding questions in the field.

关键词： Nanomaterials   Water remediation   Cost effective   Thermodynamics   Sorption mechanism  

摘要： Developing low cost sorbents for efficient elimination of organophosphorus pesticides from wastewater remains motivational. In this study, nanoparticles of water treatment residuals (nWTRs) derived from drinking water industry were produced and used for chlorpyrifos (CPF) removal from contaminated waste water. Batch sorption equilibrium study revealed that CPF sorption by nWTRs follow in order Langmuir > Temken > Kiselev adsorption models. The maximum adsorption capacity of nWTRs for CPF has shown 5 folds increase (50 mg g(-1)) compared to that of the conventional bulk WTRs and superior to most of the low cost adsorbents. Experimental parameters such as nWTR dosage, CPF concentration, and solution pH and exposure time were optimized. Remarkable CPF removal efficiency of 92% was achieved using nWTRs at pH 7 in contact time period of 30 min. The goodness-of-fit of the kinetic models tested showed that the power function model was successful in describing the kinetics of CPF adsorption with the lowest standard error (SE) of 0.0136. The thermodynamic parameters indicate the spontaneous and exothermic nature of CPF sorption on nWTRs sorbent. A possible mechanism of CPF removal by nWTRs includes formation of Al-CPF and Fe-CPF complexes and H-bonding. The novel nano-sorbent exhibits great potential as an efficient low cost sorbent for CPF removal from contaminated wastewater. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.

关键词： Heavy metals  

摘要： Water pollution by heavy metals is of increasing concern due to its devastating effects on the environment and on human health. For the removal of heavy metals from water sources, natural materials, such as spent-coffee-grains or orange/banana/chestnut peels, appear to offer a potential cheap alternative to more sophisticated and costly technologies currently in use. However, in order to employ them effectively, it is necessary to gain a deeper understanding - at the molecular level - of the heavy metals-bioorganic-water system and exploit the power of computer simulations. As a step in this direction, we investigate via atomistic simulations the capture of lead ions from water by hemicellulose - the latter being representative of the polysaccharides that are common components of vegetables and fruit peels - as well as the reverse process. A series of independent molecular dynamics simulations, both classical and ab initio, reveals a coherent scenario which is consistent with what one would expect of an efficient capture, i.e. that it be fast and irreversible: (i) binding of the metal ions via adsorption is found to happen spontaneously on both carboxylate and hydroxide functional groups;(ii) in contrast, metal ion desorption, leading to solvation in water, involves sizable free-energy barriers.