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.     

运输问题的对偶模型

线性规划原问题与对偶模型之间的转化方法一直是普通高校经营类本科生《运筹学》课程的教学重点。运输问题是线性规划中的一类典型问题,其属于非常规线性规划模型,掌握运输问题原模型与对偶模型之间的转化过程对于学习后续相关内容极为重要。文章首先推导出"常规"与"非常规"线性规划问题模型的对偶形式,然后总结线性规划模型与对偶问题模型的对应关系,最后举例说明运输问题模型的对偶形式。     

Tracer identifiability of multiphase transport systems

Using the two-component Markov process of Ref. (3) to describe tracer flow in a multiphase spacially inhomogeneous transport (plug-flow) system a mathematical framework is established for the conduction of tracer experiments for system identification.Transport velocities are assumed known. The problem of unique identification of the exchange coefficients between various phases using boundary measurements is studied. Cases of different output-boundary configurations are considered (accessible and inaccessible outputs). Sufficient conditions for identifiability are given.     

A membrane analogy supplementing photo-elasticity

In this paper is described a new method of finding the sum of the principal stresses in a two-dimensional model by means of ordinate measurements on a stretched rubber membrane as suggested by Den Hartog. The method is applied in detail on a bar with central circular hole in tension and is found to be easy in operation and of good accuracy.     

乳状液膜技术研究进展

本文介绍了乳状液膜技术的研究进展,从组分、载体、表面活性剂、稳定性、提铜及膜相循环使用等方面的研究进行了论述.     

Magnetic microbead transport during resistive pulse sensing

Tunable resistive pulse sensing (TRPS) experiments have been used to quantitatively study the motion of 1 μm superparamagnetic beads in a variable magnetic field. Closed-form theory has been developed to interpret the experiments, incorporating six particle transport mechanisms which depend on particle position in and near a conical pore. For our experiments, calculations indicate that pressure-driven flow dominates electrophoresis and magnetism by a factor of ∼100 in the narrowest part of the pore, but that magnetic force should dominate further than ∼1 mm from the membrane. As expected, the observed resistive pulse rate falls as the magnet is moved closer to the pore, while the increase in pulse duration suggests that trajectories in the half space adjacent to the pore opening are important. Aggregation was not observed, consistent with the high hydrodynamic shear near the pore constriction and the high magnetization of aggregates. The theoretical approach is also used to calculate the relative importance of transport mechanisms over a range of geometries and experimental conditions extending well beyond our own experiments. TRPS is emerging as a versatile form of resistive pulse sensing, while magnetic beads are widely used in biotechnology and sensing applications.     

New light on the history of transport

The remarkable preservative effects of peat bogs for organic material, especially wood, is well known. This has made possible the detailed examination of ancient wooden trackways built across the peat bogs of northern Europe. The construction of these, and the nature of associated artifacts, throws much light also on the nature of the vehicles that used them. This article, based on a four-year research programme supported by the Volkswagenwerk Foundation, is largely concerned with work in Lower Saxony; complementary results have been obtained from Schleswig-Holstein, Denmark, and the Netherlands.     

物联网在智能公交及停车场中的应用

随着信息化的不断推进,物联网从最初的提出到现在被越来越多的应用到了生活中各行各业、各个领域,在智能交通中也有各种形式广泛的应用。随着基于物联网的智能公交及停车场在多个省市中的初步推广运用,城市公交系统的现代化水平和服务能力得到提升,对城市道路交通拥堵和交通节能减排也起到了有效缓解的作用。文章在阐述基本概念的基础上,探讨和分析物联网在智能交通中的一部分——智能公交管理中的应用,以及在智能公交停车场管理中的应用。     

Cell encapsules with tunable transport and mechanical properties

We utilized a microfluidic device with hydrodynamic flow focusing geometry to produce uniform agarose droplets in the range of 50 to 110 μm. The transport property of the thermally gelled particles was tailored by layer-by-layer (LBL) polyelectrolytes coating on the surface and was measured via the release rates of Rhodamine B. The mechanical strength of the capsules was further enhanced by a coating of silica nano-particles in addition to polyelectrolyte coatings. We demonstrated that yeast cells can be successfully encapsulated into agarose capsules.     

论铁路运输企业财务风险管理

本文通过分析铁路运输企业财务风险的产生原因,针对当前铁路运输企业所处的经济环境提出了实施铁路企业财务风险管理、应对财务风险的相关措施.     

Flagellated Janus particles for multimodal actuation and transport

Catalytic Janus particles rely on chemical decomposition to self-propel and have displayed enormous potential for targeted drug delivery and cellular penetration. Catalytic propulsion mechanisms are limiting, however, with fuel requirements and specialized fluid properties being necessary to achieve propulsion. We have improved the dynamic propulsion of catalytic Janus particles by functionalizing flagellar filaments to one of their hemispheres. Flagellated Janus particles, torqued by rotating magnetic fields, swim along their rotation axis using the explicit chirality and flexibility of flagella, mimicking flagellar rotation of live bacteria. Depending on the working fluid, flagellated Janus particles can propel using either catalytic or swimming propulsion. We demonstrate experimentally that flagellated Janus particles behave predictably under the two actuation modes and can precisely follow trajectories under closed-loop feedback control. Flagellated Janus particles were demonstrated to swim in both Newtonian and shear-thickening fluids. These are the first Janus particles developed that can be propelled interchangeably between catalytic and flagellar swimming propulsion, allowing two distinct propulsion mechanisms for future use within in vivo operations.     

Microstripes for transport and separation of magnetic particles

We present a simple technique for creating an on-chip magnetic particle conveyor based on exchange-biased permalloy microstripes. The particle transportation relies on an array of stripes with a spacing smaller than their width in conjunction with a periodic sequence of four different externally applied magnetic fields. We demonstrate the controlled transportation of a large population of particles over several millimeters of distance as well as the spatial separation of two populations of magnetic particles with different magnetophoretic mobilities. The technique can be used for the controlled selective manipulation and separation of magnetically labelled species.     

Pressure-driven transport of particles through a converging-diverging microchannel

Pressure-driven transport of particles through a symmetric converging-diverging microchannel is studied by solving a coupled nonlinear system, which is composed of the Navier–Stokes and continuity equations using the arbitrary Lagrangian–Eulerian finite-element technique. The predicted particle translation is in good agreement with existing experimental observations. The effects of pressure gradient, particle size, channel geometry, and a particle’s initial location on the particle transport are investigated. The pressure gradient has no effect on the ratio of the translational velocity of particles through a converging-diverging channel to that in the upstream straight channel. Particles are generally accelerated in the converging region and then decelerated in the diverging region, with the maximum translational velocity at the throat. For particles with diameters close to the width of the channel throat, the usual acceleration process is divided into three stages: Acceleration, deceleration, and reacceleration instead of a monotonic acceleration. Moreover, the maximum translational velocity occurs at the end of the first acceleration stage rather than at the throat. Along the centerline of the microchannel, particles do not rotate, and the closer a particle is located near the channel wall, the higher is its rotational velocity. Analysis of the transport of two particles demonstrates the feasibility of using a converging-diverging microchannel for passive (biological and synthetic) particle separation and ordering.     

Changes in erythrocyte membrane glycoproteins during leukaemia

Changes in erythrocyte membrane glycoproteins during, leukaemia were investigated in one hundred patients. Control group contained normal ones. The total protein and protein bound total carbohydrates (neutral sugars) in the glycoproteins extracted from the erythrocyte membrane showed significant reduction in total protein and protein bound total carbohydrates before radiotherapy. However, after the radiotherapy there was further reduction in total protein by 10.41% whereas there was increase in total carbohydrates by 9.98%. Qualitative analysis reveals that with the help of lectins one can pin point the sugars which appear or disappear due to leukaemia. The test could be of a diagnostic value.     

铁路预制T梁运输技术

大吨位预制铁路桥梁运输安全、畅通是实现我国铁路全面提速的一项重要保证,是实现整体运输秩序良好的重要环节。为了更好地有效组织大吨位预制铁路桥梁运输工作进行,特总结这两年装车经验为本梁厂和其它需要运输桥梁的单位分享。