The behavior of capillary suspensions at diverse length scales: From single capillary bridges to bulk

Liquid-liquid-solid systems are becoming increasingly common in everyday life with many possible applications. Here, we focus on a special case of such liquid-liquid-solid systems, namely, capillary suspensions. These capillary suspensions originate from particles that form a network based on capillary forces and are typically composed of solids in a bulk liquid with an added secondary liquid. The structure of particle networks based on capillary bridges possesses unique properties compared with networks formed via other attractive interactions where these differences are inherently related to the properties of the capillary bridges, such as bridge breaking and coalescence between adjacent bridges. Thus, to tailor the mechanical properties of capillary suspensions to specific requirements, it is important to understand the influences on different length scales ranging from the dynamics of the bridges with varying external stimuli to the often heterogeneous network structure.     

Enhanced Power Density of Alcohol Biofuel Cell by Polymer-assisted Crosslinks of 3D Graphene on Carbon Paper as the Bioanode

Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device.     

Particle manipulation via integration of electroosmotic flow of power-law fluids with standing surface acoustic waves (SSAW)

Standing surface acoustic wave (SSAW) based microfluidic devices have shown great promise toward fluid and particle manipulation applications in medicine, chemistry, and biotechnology. In this article, we present an analytical model for investigating continuous manipulation of particles (both synthetic and biological) within electroosmotic flow of non-Newtonian bio-fluids in a microfluidic channel under the influence of standing surface acoustic waves (SSAW). The particles are injected along the center of channel into the electroosmotically driven flow of power-law fluids, wherein their transport through the SSAW region is dictated by the hydrodynamic, electrophoretic, and acoustic forces. We first present a mathematical model to analyze the characteristics of electroosmotic flow of non-Newtonian power-law fluids in a hydrophobic slit microchannel. Next, we investigate the trajectories of particles in the flow field due to the combined effect of electroosmotic, electrophoretic, and acoustophoretic forcing mechanisms. The effect of key parameters such as particle size, their physical properties, input power, flow rate, and flow behavior index on the particle trajectories is examined while including the effect of the channel walls. The presented model delineates the methodologies of improving SSAW-based particle separation technology by considering the fluid rheology as well as the surface properties of the channel walls. Therefore, we believe that this model can serve as an efficient tool for device design and quick optimizations to explore novel applications concerning the integration of electroosmotic flows with acoustofluidic technologies.     

浅水区海底管道周围海床渗透压力计算研究

我国海上油田开采起步较晚，大部分油田处于浅水区，因此，在设计管道时，应充分考虑由浅水区波浪引起的管道周围海床渗流力。根据浅水波相关假设，考虑自由水面非线性影响，推导出椭圆余弦波的波面方程，在此基础上进一步得到一个关于速度势的表达式，并根据该表达式得出作用于海床表面的波压公式。考虑海床土的压缩性，推导出一阶近似椭圆余弦波作用下浅水区埋置管道周围海床的渗流压力解析解，最后将计算结果与大型水槽试验及以往研究成果作对比。结果表明，在椭圆余弦波的作用下，由一阶椭圆余弦波理论得到的计算结果与试验结果规律基本一致，与相似工况下的现有理论成果数值基本相同，具有一定的可行性和工程价值。     

纳米阵列中气体驱替液体的流动特征

纳米尺度下气体驱动液体流动特征在纳流控芯片及页岩气开发中具有广泛的应用前景. 利用管径规格为292.8 nm,206.2 nm,89.2 nm,67.0 nm,26.1 nm的氧化铝膜为纳米阵列,进行气驱水实验和单相气体流动实验,分析纳米尺度下气驱水流动特征. 实验表明,纳米阵列中气驱水时气体流量随驱动压力变化经历三个阶段:第一阶段流量缓慢增大,且比单相气体流量降低约一个数量级;第二阶段纳米阵列中的水被大量驱替出,流量迅速增大;第三阶段纳米阵列中的水全部被驱替出,流动特征与单相气体流动保持一致. 分析表明,气驱水第一阶段存在气液界面毛细管力的“钉扎”作用及固液界面相互作用力的影响,是产生非线性流动的主要原因;而一旦“钉扎”作用破坏,气体进入管道推动界面运动,气柱与液柱之间的毛细曲面曲率变化,毛细管力减小,气体流量急剧增大,其中毛细管力随驱替压力增大急剧变化,是造成第二阶段气体流量突变的主要原因.      

On the effect of fractional statistics on quantum ion acoustic waves

In this paper, I study the effect of a small deviation from the Fermi–Dirac statistics on the quantum ion acoustic waves. For this purpose, a quantum hydrodynamic model is developed based on the Polychronakos statistics, which allows for a smooth interpolation between the Fermi and Bose limits, passing through the case of classical particles. The model includes the effect of pressure as well as quantum diffraction effects through the Bohm potential. The equation of state for electrons obeying fractional statistics is obtained and the effect of fractional statistics on the kinetic energy and the coupling parameter is analyzed. Through the model, the effect of fractional statistics on the quantum ion acoustic waves is highlighted, exploring both linear and weakly nonlinear regimes. It is found that fractional statistics enhance the amplitude and diminish the width of the quantum ion acoustic waves. Furthermore, it is shown that a small deviation from the Fermi–Dirac statistics can modify the type structures, from bright to dark soliton. All known results of fully degenerate and non-degenerate cases are reproduced in the proper limits.     

INFLUENCE OF FRICTION ON THE MOTION OF BASE WITH AN ECCENTRIC ROTOR

偏心转子惯性力引起的底座运动受到地面摩擦的影响，与光滑情形的理论结果存在定性差异。转子逆时针匀速旋转的惯性力若小于构件总重，则底座随摩擦因子增加而出现连续、一次停顿和两次停顿的振动及完全静止的4种状态。因惯性力对正压力及摩擦力的影响，底座在连续及一次停顿的振动时右向位移较大；而底座跳起时如``蛤蟆夯'则整体向左移动。     

小鼠小梁细胞与肌成纤维细胞的同步辐射红外显微光谱

原发性开角型青光眼是常见的致盲性眼部疾病。眼压升高是原发性开角型青光眼发生和发展最主要的危险因素，是由小梁网途径的房水外流排出系统发生病变、房水流出阻力增加所致。研究表明，房水中存在的转化生长因子-β能够使小梁细胞纤维化，诱导小梁细胞过度增殖，从而阻碍房水外流，导致原发性开角型青光眼的发生。原发性开角型青光眼发病隐蔽，病程进展缓慢，早期没有任何症状，往往到晚期视力视野有显著损害时，才会被发现，因此原发性开角型青光眼的早期诊断尤为重要。同步辐射红外显微成像结合高亮度、高分辨率的同步辐射源，同时配备傅里叶变换红外光谱仪与红外显微镜，可以实现细胞的检测。这对从分子层面获取细胞的变化信息，深入理解疾病的发病机制以及疾病的早期诊断具有非常重要的意义。虽然有很多红外光谱在生物医学领域的研究报道，但是应用红外光谱显微成像技术研究细胞等生物医学体系仍然是亟待发展的领域，并且目前未找到关于红外光谱用于小梁网细胞的检测报道。在体外用转化生长因子-β对老鼠小梁网细胞进行诱导，使其转化为肌成纤维细胞，模拟小梁细胞纤维化过程。对小梁网细胞以及经转化生长因子-β诱导形成的肌成纤维细胞进行同步辐射红外显微成像及光谱分析，并进一步探讨同步辐射用于早期诊断原发性开角型青光眼的可行性。研究表明肌成纤维细胞内的弹性蛋白明显高于小梁网细胞，而弹性蛋白中95%为非极性氨基酸，即氨基酸的侧链基团R基只有C和H两种元素。对比两种细胞的红外谱图，发现在2 934，2 900和2 845 cm-1，肌成纤维细胞的 CH₃，CH₂和CH的伸缩振动明显强于小梁网细胞，推测可能是由于转化生长因子-β诱导后细胞内弹性蛋白增加所致。在细胞层面检测了小梁网细胞的过度增殖，为将来可以直接获取细胞的红外光谱从而检测小梁网细胞的增殖程度，进而检测原发性开角型青光眼等疾病奠定了基础。得出同步辐射红外谱学与显微成像有望成为检测原发性开角型青光眼新手段的结论，也为将来便携式红外显微光谱仪临床实时检测青光眼等疾病提供了依据。     

Stratification phenomenon in an inclined rheology of UCM nanomaterial

This investigation presents the unsteady rheology of Maxwell nanomaterial induced to flow over an inclined surface. Simultaneous effects of stratification, thermal radiation, heat source/sink and magnetic field are taken into account. Viscous dissipation and mixed convection due to concentration and temperature differences are also analyzed. The governing partial differential equations for the Maxwell nanofluid which incorporate the effects of Brownian and thermophoresis effects are simplified by using appropriate similarity transformations, and solved analytically by using homotopy analysis method (HAM). The effects of involved physical parameters on the flow field are analyzed graphically and numerically.