A new role for exhaled nitric oxide as a functional marker of peripheral airway caliber changes: a theoretical study

Though considered as an inflammation marker, exhaled nitric oxide (FENO) was shown to be sensitive to airway caliber changes to such an extent that it might be considered as a marker of them. It is thus important to understand how these changes and their localization mechanically affect the total NO flux penetrating the airway lumen (JawNO), hence FENO, independently from any inflammatory status change. A new model was used which simulates NO production, consumption and diffusion inside the airway epithelium wall, then, NO excretion through the epithelial wall into the airway lumen and, finally, its axial transport by diffusion and convection in the airway lumen. This model may also consider the presence of a mucus layer coating the epithelial wall. Simulations were performed that showed the great sensitivity of JawNO to peripheral airways caliber changes. Moreover, FENO showed distinct behaviors depending on the location of the caliber change. Considering a bronchodilation, absence of FENO change was associated with dilation of central airways, FENO increase with dilation up to pre-acinar small airways, and FENO decrease with intra-acinar dilation due to amplification of the back-diffusion flux. The presence of a mucus layer was also shown to play a significant role in FENO changes. Altogether, the present work provides theoretical evidences that specific FENO changes in acute situations are linked to specifically located airway caliber changes in the lung periphery. This opens the way for a new role for FENO as a functional marker of peripheral airway caliber change

Contribution à l'étude des colonnes à bulles mettant en oeuvre une réaction de précipitation

Doctorat en sciences appliquéesinfo:eu-repo/semantics/nonPublishe

Development of a continuous “self-seeding” microfluidic crystallization device for active pharmaceutical ingredients

info:eu-repo/semantics/nonPublishe

Development of a Continuous "Self-seeding" Microfluidic Crystallization Device for Active Pharmaceutical Ingredients

info:eu-repo/semantics/publishe

Self-seeding effect of particle clusters for microfluidic crystallization

info:eu-repo/semantics/nonPublishe

Bubbly flow and gas-liquid mass transfer in square and circular microchannels for stress-free and rigid interfaces. CFD analysis

In this paper, the dynamics of bubbles and the mass transfer between bubbles and the surrounding liquid in square and circular microchannels are investigated, in the bubbly flow regime. For this purpose, a computational fluid dynamics analysis is used to carry out numerical simulations of the liquid flow and the mass transport around a spherical bubble in a square or a circular microchannel, for a stress-free or a rigid gas–liquid interface. The corresponding results are consolidated into correlations to calculate the bubble velocity and the interfacial rate of mass transfer as functions of the control parameters of the system. For each considered case, the flow structure, the concentration field around the bubble and the local interfacial rate of mass transfer are presented and shown to be intricately related.URL: http://link.springer.com/article/10.1007%2Fs10404-015-1578-0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Hydrogen peroxide concentration by pervaporation of a ternary liquid solution in microfluidics

Pervaporation in a microfluidic device is performed on liquid ternary solutions of hydrogen peroxide–water–methanol in order to concentrate hydrogen peroxide IJH2O2) by removing methanol. Thequantitative analysis of the pervaporation of solutions with different initial compositions is performed,varying the operating temperature of the microfluidic device. Experimental results together with amathematical model of the separation process are used to understand the effect of the operatingconditions on the microfluidic device efficiency. The parameters influencing significantly the performanceof pervaporation in the microfluidic device are determined and the limitations of the process are discussed.For the analysed system, the operating temperature of the chip has to be below the temperature at whichH2O2 decomposes. Therefore, the choice of an adequate reduced operating pressure is required,depending on the expected separation efficiency.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Continuous separation, with microfluidics, of the components of a ternary mixture: from vacuum to purge gas pervaporation

The general objective of this paper is to investigate the separation, with microfluidics, of the components of a ternary mixture, when using vacuum or purge gas pervaporation. The ternary mixture considered is a mixture of methanol (MeOH), water (H2O) and hydrogen peroxide (H2O2). In a previous work (Ziemecka in Lab Chip 15:504–511, 2015), we presented the proof of concept of a microfluidic device, which was able to partially separate MeOH from the other components of such a mixture, by using vacuum pervaporation. Here, our goal is to optimize the operation of this device, by considering vacuum pervaporation, but also purge gas pervaporation. First, we provide a mathematical model of the device. This model is used to discuss the influence of the operating parameters on the device operation. To apply this model to the considered mixture, we determined the MeOH and H2O permeability coefficients of PDMS membranes prepared from different concentrations of the curing agent. The model is then successfully compared to experimental data. The model and the experiments show that high efficiencies can be reached for both vacuum and purge gas pervaporation, provided a fine-tuning of the operating parameters. For instance, a good efficiency of the vacuum pervaporation is reached at high temperature and low pressure. For purge gas pervaporation, it is reached for low temperature and high pressure.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Bubbly flow and gas-liquid mass transfer in square and circular microchannels for stress-free and rigid interfaces. Dissolution model

A model is proposed to describe the dissolution of a chain of spherical pure gas bubbles into a nonvolatile liquid, along square and circular microchannels. The gas–liquid interface is considered stress-free or rigid. This model enables predicting, in each considered case, the evolution along the microchannel of the bubble diameter, the bubble velocity, the separation distance between two successive bubbles, the liquid fraction, the pressure in both the liquid and the gas phases, the concentration of the dissolved gas in the liquid phase and the mass transfer coefficient between the bubble and the liquid phase. The influence on the gas dissolution of the interfacial boundary condition, the microchannel type, the operating conditions and the physicochemical properties of the liquid and gas is analyzed. Existing experimental data for a nearly square microchannel are convincingly reproduced using the model. The validity and the different applications of the model are also discussed.SCOPUS: ar.jinfo:eu-repo/semantics/publishe