Numerical Modeling of Mass Transfer in the Interaction between River Biofilm and a Turbulent Boundary Layer

In this article dedicated to the modeling of vertical mass transfers between the biofilm and the bulk flow, we have, in the first instance, presented the methodology used, followed by the presentation of various results obtained through analyses conducted on velocity fields, different fluxes, and overall transfer coefficients. Due to numerical constraints (resolution of relevant spatial scales), we have restricted the analysis to low Schmidt numbers (Sc=0.1, Sc=1, and Sc=10) and a single roughness Reynolds number (Re*=150). The analysis of instantaneous concentration fields from various simulations revealed logarithmic concentration profiles above the canopy. In this zone, the concentration is relatively homogeneous for longer times. The analysis of results also showed that the contribution of molecular diffusion to the total flux depends on the Schmidt number. This contribution is negligible for Schmidt numbers Sc≥0.1, but nearly balances the turbulent flux for Sc=0.1. In the canopy, the local Sherwood number, given by the ratio of the total flux (within or above the canopy) to the molecular diffusion flux at the wall, also depends on the Schmidt number and varies significantly between the canopy and the region above. The exchange velocity, a purely hydrodynamic parameter, is independent of the Schmidt number and is on the order of 10% of in the present case. This study also reveals that nutrient absorption by organisms near the wall depends on the Schmidt number. Such absorption is facilitated by lower Schmidt numbers.

The Absorption and Transport of Magnolol in Caco-2 Cell Model

Objective： To investigate the absorption and transport mechanism of magnolol in Caco-2 cell model. Methods： A human intestinal epithelial cell model Caco-2 cell in vitro cultured was applied to study the absorption and transport of magnolol, the effects of time, donor concentration, P-gp inhibitor verapamil, pH and temperature on the absorption and transport of magnolol were investigated. The determination of magnolol was performed by high performance liquid chromatography, then the values of apparent permeability coefficient （Papp） and Pratio Basolateral-to-Apical （BL-to-AP）/Apical-to-Basolateral （AP-to-BL） were calculated. Results： In Caco-2 cell model, comparing the amounts of transport of AP-to-BL and BL-to-AP, the latter was larger. At the same donor concentration, either the amounts of transport of AP-to-BL or BL-to-AP increased with increase in donor concentration and incubation time. Verapamil could significantly improve the amounts of transport of AP- to-BL. The transport of AP-to-BL and BL-to-AP depended on temperature, and there was no significant effect of pH on the transport of AP-to-BL. Conclusion： Magnolol could be transported through the intestinal mucosa via a passive diffusion mechanism primarily, coexisting with a carrier-mediated transport, at the same time, the efflux mechanism could be involved.

＂Fluidic Diode＂ for Passive Unidirectional Liquid Transport Bioinspired by the Spermathecae of Fleas

We present a device for passive unidirectional liquid transport. The capillary channels used are bioinspired by the shape of the spermathecae （receptaculum seminis） of rabbit fleas （Spilopsyllus cuniculi） and rat fleas （Xenopsytla cheopis）. The spermatheca is an organ of female fleas that stores sperm until suitable conditions to lay eggs are found. We translated and multiplied the natural form and function of a spermatheca to create a continuous capillary system from which we designed our microfluidic device based directly on the model from nature. Applying the Young-Laplace equation, we derived a theoretical description of local liquid transport, which enables model-guided design. We arranged the bioinspired capillaries in parallel and engraved them in poly（methyl methacrylate） （PMMA） plates by CO2 laser ablation. The fabricated structures transport soapy water passively （i.e., without external energy input） in the forward direction at velocities of about 1 mm＇s i while halting the liquid fronts completely in the backward direction. The bio- inspired capillary channels are capable of unidirectional liquid transport against gravity. Distance and velocity measurements prove the feasibility of the concept. Unidirectional passive liquid transport might be advantageous in technical surfaces for liquid man- agement, for instance, in biomedical microfluidics, lab-on-chip, lubrication, electronics cooling and in micro-analysis devices.

An Optimised Surface Structure for Passive, Unidirectional Fluid Transport Bioinspired by True Bugs

Some true bug species use droplet-shaped,open-capillary structures for passive,unidirectional fluid transport on their body surface in order to spread a defensive fluid to protect themselves against enemies.In this paper we investigated if the shape of the structures found on bugs(bug-structure)could be optimised with regard to better performance in unidirectional fluid transportation.Furthermore,to use this kind of surface structure in technical applications where fluid surface interaction occurs,it is necessary to adapt the structure geometry to the contact angle between fluid and surface.Based on the principal of operation of the droplet-shaped structures,we optimised the structure shape for better performance in targeted fluid flow and increase in flexibility in design of the structure geometry.To adapt the structure geometry and the structure spacing to the contact angle,we implemented an equilibrium simulation of the,the structure surrounding,fluid.In order to verify the functionality of the optimised structure,we designed and manufactured a prototype.By testing this prototype with pure water used as fluid,the functionality of the optimised structure and the simulation could be proved.This kind of structure may be used on technical surfaces where targeted fluid transport is needed,e.g.evacuation of condensate in order to prevent the surface from mold growth,microfluidics,lab-on-a-chip applications and on microneedles for efficient drug/vaccine coating.

2 Tbit/s based coherent wavelength division multiplexing passive optical network for 5G transport

Future high-speed mobile communication systems require low latency and high capacity networks.Coherent wavelength division multiplexing(WDM)passive optical network(PON)scheme is expected to play a vital role in these systems.In this paper,coherent WDM-PON scheme based on dual-polarization 16-quadrature amplitude modulation(DP-16 QAM)transceiver has been investigated.The aim of this scheme is to build a 2 Tbit/s(125 Gbit/s/λ×16 wavelengths)network that will be used in the construction of the transport architecture of fifth generation(5 G)and beyond 5 G(B5 G)cellular networks either in mobile front haul(MFH)or mobile back haul(MBH).The results indicate that the proposed scheme is very adequate for both 5 G and B5 G cellular networks requirements.