A comparison of centrifugation and tangential flow filtration for nanoparticle purification: A case study on acetalated dextran nanoparticles

Tangential fiow filtration (TFF) is a purification method commonly used in a multitude of fields,including particle engineering.Currently,there is still a lack of comprehensive understanding of the effects of key TFF parameters on nanoparticle (NP) characteristics (purification outcomes).The present study aimed to investigate the influence of various factors on the characteristics of TFF-purified NP.The most commonly used NP purification method,centrifugation,was studied as a control.A design of experiment approach was implemented to investigate the influence of transmembrane pressure,flow rate,and initial drug loading on NP characteristics using paclitaxel as a model small molecule.Following the determination of optimized TFF parameters,the two purification methods were assessed using other model small molecules (i.e.tacrolimus and resveratrol).The results indicated that the TFF parameters and initial loading of the drug played important roles in the purified NP outcomes.Compared with the centrifugation method,TFF resulted in smaller NP with higher drug loading.TFF was able to circumvent issues associated with conventional centrifugation,while yielding similar results,and can potentially serve as a suitable large-scale purification method for polymeric NP.

Particle dynamics in dense shear granular flow

The particle dynamics in an annular shear granular flow is studied using the discrete element method, and the influences of packing fraction, shear rate and friction coefficient are analyzed. We demonstrate the existence of a critical packing fraction exists in the shear granular flow. When the packing fraction is lower than this critical value, the mean tangential velocity profile exhibits a rate-independent feature. However, when the packing fraction exceeds this critical value, the tangential velocity profile becomes rate-dependent and varies gradually from linear to nonlinear with increasing shear rate. Furthermore, we find a continuous transition from the unjammed state to the jammed state in a shear granular flow as the packing fraction increases. In this transforming process, the force distribution varies distinctly and the contact force network also exhibits different features.

Dynamic and Numerical Study of Waves in the Tibetan Plateau Vortex

In terms of its dynamics, The Tibetan Plateau Vortex （TPV） is assumed to be a vortex in the botmdary layer forced by diabatic heating and friction. In order to analyze the basic characteristics of waves in the vortex, the governing equations for the vortex were established in column coordinates with the balance of gradient wind. Based on this, the type of mixed waves and their dispersion characteristics were deduced by solving the linear model. Two numerical simulations with triple-nested domains--one idealized large-eddy simulation and one of a TPV that took place on 14 August 2006---were also carried out. The aim of the simulations was to validate the mixed wave deduced from the governing equations. The high-resolution model output data were analyzed and the results showed that the tangential flow field of the TPV in the form of center heating was cyclonic and convergent in the lower levels and anticyclonic and divergent in the upper levels. The simulations also showed that the vorticity of the vortex is uneven and might have shear flow along the radial direction. The changing vorticity causes the formation and spreading of vortex Rossby （VR） waves, and divergence will cause changes to the n^otion of the excitation and evolution of inertial gravity （IG） waves. Therefore, the vortex may contain what we call mixed ：inertial gravity-vortex Rossby （IG-VR） waves. It is suggested that some strongly developed TPVs should be studied in the future, because of their effects on weather in downstream areas.