Microfluidic trapping of giant unilamellar vesicles to study transport through a membrane pore

We present a microfluidic platform able to trap single GUVs in parallel. GUVs are used as model membranes across many fields of biophysics including lipid rafts, membrane fusion, and nanotubes. While their creation is relatively facile, handling and addressing single vesicles remains challenging. The PDMS microchip used herein contains 60 chambers, each with posts able to passively capture single GUVs without compromising their integrity. The design allows for circular valves to be lowered from the channel ceiling to isolate the vesicles from rest of the channel network. GUVs containing calcein were trapped and by rapidly opening the valves, the membrane pore protein α-hemolysin (αHL) was introduced to the membrane. Confocal microscopy revealed the kinetics of the small molecule efflux for different protein concentrations. This microfluidic approach greatly improves the number of experiments possible and can be applied to a wide range of biophysical applications.     

An integrated microfluidic platform to fabricate single-micrometer asymmetric giant unilamellar vesicles (GUVs) using dielectrophoretic separation of microemulsions

We present a microfluidic technique that generates asymmetric giant unilamellar vesicles (GUVs) in the size range of 2–14 μm. In our method, we (i) create water-in-oil emulsions as the precursors to build synthetic vesicles, (ii) deflect the emulsions across two oil streams containing different phospholipids at high throughput to establish an asymmetric architecture in the lipid bilayer membranes, and (iii) direct the water-in-oil emulsions across the oil–water interface of an oscillating oil jet in a co-flowing confined geometry to encapsulate the inner aqueous phase inside a lipid bilayer and complete the fabrication of GUVs. In the first step, we utilize a flow-focusing geometry with precisely controlled pneumatic pressures to form monodisperse water-in-oil emulsions. We observed different regimes in forming water-in-oil multiphase flows by changing the applied pressures and discovered a hysteretic behavior in jet breakup and droplet generation. In the second step of GUV fabrication, an oil stream containing phospholipids carries the emulsions into a separation region where we steer the emulsions across two parallel oil streams using active dielectrophoretic and pinched-flow fractionation separations. We explore the effect of applied DC voltage magnitude and carrier oil stream flow rate on the separation efficiency. We develop an image processing code that measures the degree of mixing between the two oil streams as the water-in-oil emulsions travel across them under dielectrophoretic steering to find the ideal operational conditions. Finally, we utilize an oscillating co-flowing jet to complete the formation of asymmetric giant unilamellar vesicles and transfer them to an aqueous phase. We investigate the effect of flow rates on properties of the co-flowing jet oscillating in the whipping mode (i.e., wavelength and amplitude) and define the phase diagram for the oil-in-water jet. Assays used to probe the lipid bilayer membrane of fabricated GUVs showed that membranes were unilamellar, minimal residual oil remained trapped between the two lipid leaflets, and 83% asymmetry was achieved across the lipid bilayers of GUVs.     

隐性知识形成的主体相对性模式识别

知识属于认识领域的范畴,不同的主体在对同一事物不同状态的反映过程中,由于实践能力、认识能力以及价值目标的不同,会形成不同的隐性知识。鉴于此,用神经网络模型对确定的主体在对同一事物不同状态的认识过程中的认识模式进行识别,以确定其在某一时期的认识习惯,把握其知识形成机制,以期对其未来的知识形成进行预测。     

Throughput of underwater acoustic networks with significant multipath delays

All existing works regarding the throughput of underwater acoustic networks (UWANs) explicitly ignore multipath effect of underwater acoustic channels (UWACs), which, however, is a prominent feature in underwater environments. In this paper, we investigate the throughput of UWANs with significant multipath delays. We extend the popular delay matrix model to make it suitable for analysis of throughput in UWANs with multipath delays. We differentiate between two cases of successful transmissions corresponding to different channel models. With the extended model, we derive the upper bounds of throughput for UWANs under different channel models with various fair constraints. We also show the necessary conditions for achieving these upper bounds under different scenarios. In addition, with derived upper bounds and necessary conditions, we offer designing rules for optimal schedules in UWANs with different channel models. Some examples of optimal schedules which could achieve the upper bounds under different scenarios are also provided.     

虚拟型学习团队形成与界定

知识经济时代，企业组织的产权模式从排他性向共享性转变，组织结构趋向扁平化，跨越组织职能和边界的工作团队成为组织架构的基础。组织理论的演进与嬗变，使得高新技术企业在实现资源内聚和资源外取过程中，形成了新的虚拟型学习团队模式，并与虚拟团队和学习团队有所区别。     

Manipulating particle trajectories with phase-control in surface acoustic wave microfluidics

We present a 91 MHz surface acoustic wave resonator with integrated microfluidics that includes a flow focus, an expansion region, and a binning region in order to manipulate particle trajectories. We demonstrate the ability to change the position of the acoustic nodes by varying the electronic phase of one of the transducers relative to the other in a pseudo-static manner. The measurements were performed at room temperature with 3 μm diameter latex beads dispersed in a water-based solution. We demonstrate the dependence of nodal position on pseudo-static phase and show simultaneous control of 9 bead streams with spatial control of −0.058 μm/deg ± 0.001 μm/deg. As a consequence of changing the position of bead streams perpendicular to their flow direction, we also show that the integrated acoustic-microfluidic device can be used to change the trajectory of a bead stream towards a selected bin with an angular control of 0.008 deg/deg ± 0.000(2) deg/deg.     

材料成型实验教学改革探索

材料成型实验是一门实践性强的综合实验课程。本文针对材料成型实验中存在的问题,通过改善教学条件,在实验教学模式、师资队伍建设、考核体系等多个方面进行改革和探索,明显提升了教学质量。     

材料成型实验教学改革探索

材料成型实验是一门实践性强的综合实验课程。本文针对材料成型实验中存在的问题,通过改善教学条件,在实验教学模式、师资队伍建设、考核体系等多个方面进行改革和探索,明显提升了教学质量。     

论数字鸿沟的产生、发展及消亡

通过对信息不公平在当今时代的表现形式——数字鸿沟的产生、概念,以及近年来数字鸿沟的相关数据发展变化情况进行分析,得出信息不公平将伴随人类社会长期存在,但是数字鸿沟终会消亡的结论。     

大图书馆理念的内涵及形成和发展

阐述了大图书馆理念是一种全新的图书馆管理理念,是网络经济时代的产物;大图书馆理念是文献信息资源共享的基础,也是新世纪图书馆发展的动力。     

锻炼习惯的形成与引导

长期以来，中学体育教学在“体育就是体质教育”的观念影响下，不少教师对增强学生体质的教育，只追求体育锻炼的 “近期效益”。完成学习任务，而忽视了学 生锻炼习惯的培养，这种“近期效益”的观念，已远远地落后于国际潮流。实践证明，一个人终生健康，得益于终生体育，而终生体育的关键环节——中学体育教育，其要求不仅是中学生在中学期间学习和掌握体育的基本知识、技术和技能，更重要 的是提高培养他们对体育的兴趣和爱好，养成炼身的习惯。本文试从中学生锻炼习惯形成的心理轨迹及引导方法作出初步的研究和分析。 １、锻炼习惯的心…     

心理契约形成机理的博弈分析

通过构建心理契约的基本博弈模型、不确定状态下的博弈模型及动态博弈模型,分析心理契约形成的内在机理。研究发现,组织或者员工履行责任所获取的收入越高,履行责任的成本越低,不履行责任受到的惩罚越重,不履行责任给对方造成的损失越低,得到的期望收益越高,双方越可能选择"履行"策略。心理契约需要组织与员工双方共同构建。     

Signal analysis of medical acoustic sounds with applications to chest medicine

The stethoscope is widely used for listening to heart sounds (cardiology), lung sounds (chest medicine) and digestive, bowel sounds, etc. An obvious development from this is to seek to automate the process by which a physician listens to and interprets the sounds. In parallel with signal processing developments, medical usage of diagnostic instrumentation is changing. The study described in this paper aimed to prove the feasibility of an automatic stethoscope for particular screening and monitoring algorithms, for which we envisage genuine clinical applicability. The first algorithm is to enable non-specialists to screen for pulmonary fibrosis. The algorithm was found to distinguish effectively between signals representing patients with chronic obstructive pulmonary disease (COPD), those with pulmonary fibrosis and normal individuals. A clear demarcation was observed between signals from patients in different diagnostic categories, with orders of magnitude differences between the groups. The second application is the monitoring of asthmatic patients. The proportion of wheeze within a given time recording is an objective indicator of the patient's condition, which can be used to monitor the person's progress during treatment. The proposed usage of each algorithm is demonstrated through a conceptual device, in which the ability to objectively quantify the patient's condition represents a powerful opportunity to improve clinical outcomes.     

一次绕线机低功率热丝改造

本文主要论述了公司为了满足市场对低功率热丝的需求,针对已有的日立一次绕线机只能生产单一产品的实际情况,通过大量实验和理论分析,逐层深入剖析一次绕线机控制原理,然后确定改造方案,终于成功完成了一次绕线机低功率热丝改造。     

中国二元经济结构的形成与消解

本文分析了中国二元经济结构的历史成因，表明了尽快打破城乡二元经济结构的必要性与紧迫性，指出了中国二元经济结构的特殊困境与消解思路。     

信息形成机制与信息源失真研究

信息源失真是最本质的信息失真。本文在界定数据和信息内涵的基础上,分析了信息的形成过程,构建了信息的处理机制。探讨了信息源失真的原因：在数据搜集阶段,数据搜集工具、处理者认知能力、调查对象的主观故意、沟通障碍会影响数据的准确与全面;在数据处理阶段,数据处理方法工具不当、处理者知识积累偏误及生理心理因素会影响数据处理结果;信息把关人也会故意传播虚假信息。最后提出了解决信息源失真的方法和思路,有些信息源失真也许根本就没有很好的解决办法．需要信息接受者仔细鉴别。     

Mixing enhancement in T-junction microchannel with acoustic streaming induced by triangular structure

The T-shaped microchannel system is used to mix similar or different fluids, and the laminar flow nature makes the mixing at the entrance junction region a challenging task. Acoustic streaming is a steady vortical flow phenomenon that can be produced in the microchannel by oscillating acoustic transducer around the sharp edge tip structure. In this study, the acoustic streaming is produced using a triangular structure with tip angles of 22.62°, 33.4°, and 61.91°, which is placed at the entrance junction region and mixes the inlets flow from two directions. The acoustic streaming flow patterns were investigated using micro-particle image velocimetry (μPIV) in various tip edge angles, flow rate, oscillation frequency, and amplitude. The velocity and vorticity profiles show that a pair of counter-rotating streaming vortices were created around the sharp triangle structure and raised the Z vorticity up to 10 times more than the case without acoustic streaming. The mixing experiments were performed by using fluorescent green dye solution and de-ionized water and evaluated its performance with the degree of mixing (M) at different amplitudes, flow rates, frequencies, and tip edge angles using the grayscale value of pixel intensity. The degree of mixing characterized was found significantly improved to 0.769 with acoustic streaming from 0.4017 without acoustic streaming, in the case of 0.008 μl/min flow rate and 38 V oscillation amplitude at y = 2.15 mm. The results suggested that the creation of acoustic streaming around the entrance junction region promotes the mixing of two fluids inside the microchannel, which is restricted by the laminar flow conditions.     

Dispersion relations for acoustic waves in heterogeneous multi-layered structures contacting with fluids

The paper describes a method and a computer application for the computation of the velocity of acoustic waves excited in complicated multi-layered structures consisting of anisotropic piezoelectric and isotropic layers. The structure assumes to be unbounded in the lateral directions. The top and bottom layers are either semi-infinite in the vertical direction or they contact with media such as fluids, gases or vacuum. A special homogenization technique enables to account for bristle-like layers contacting with a fluid. The program is supplied with a user friendly graphical interface and can be useful for researchers working on acoustic sensors.     

信用的起源、发展、形成与应用型态

从经济学的角度探讨了信任、信誉、信用三者之间的关系及信用在经济活动中的应用。信任起源于人与人之间的交往,信誉是正向信任的累积效应,信用则是信誉的长期积累并具有商品特性,尤其是具有货币的流通、贮藏、支付等功能。