Positional small-angle X-ray scattering

Positional small-angle X-ray scattering has been implemented and developed as a new nondestructive technique to study the formation and growth of flaws in polymers. The technique consists of measuring the intensity of scattering at a constant scattering angle while the sample is moved through the incident x-ray beam. Examples of applications of the technique from several different materials are presented.     

Electrodiffusional determination of momentum transfer in annular flows: Axial developing and swirling decaying flows

Two types of developing flows were studied: the axial developing flow occuring downstream of fixed beds of spheres, and the swirling decaying flow induced by a tangential inlet. In both flows, the momentum transfer was investigated for different axial distances and for a Reynolds number range of 90 to 3780 using an electrochemical method. Measurement of the wall shear stress was achieved by means of the limiting electrodiffusional current on circular microelectrodes. Comparisons of swirling flow and axial developing and developed flows are made in terms of velocity gradients and friction factors.Notation A microcathode surface area - C _s potassium ferricyanide concentration - d microelectrode diameter - e=R ₂–R ₁ thickness of the annular gap - F Faraday constant - f _ax,f _df,f _e friction factors - I _L limiting diffusional current - k _F local mass transfer coefficient - L _e entrance length - R ₁ external radius of the inner cylinder - R ₂ internal radius of the outer cylinder - Reynolds number - S _ax,S _df,S _e velocity gradients - U _m mean axial velocity - x axial coordinate - kinematic viscosity This paper was presented at the Workshop on Electrodiffusion Flow Diagnostics, CHISA, Prague, August 1990.     

Entrance effect on mass transfer in a parallel plate electrochemical reactor

The influence of different fluid inlet types, slits or tubes, on mass transfer in a rectangular reactor was studied. Measurements of mass transfer coefficients were made using the limiting diffusion current technique based on ferricyanide ion reduction at a large nickel electrode located downstream of abrupt expansions. The overall mass transfer coefficients obtained were 3 to 13 times greater than those obtained in fully developed flows. Overall mass transfer coefficients were correlated for Reynolds numbers ranging from 400 to 3500 by a unique equation by introducing a nondimensional expansion factor defined by the ratio of the fluid inlet cross-section to that of the reactor. The correlation equation obtained was compared with literature data.     

Lagrangian trajectory model for turbulent swirling flow in an annular cell: comparison with residence time distribution measurements

Knowledge of the flow field can be very useful for reactor design and optimization. Data concerning the displacement and trajectories of reactive elements are of primary interest for a better understanding of process running. Results can be deduced from computational fluid dynamics or experimental measurements. However, numerical simulation is difficult to achieve for complex flow such as swirling decaying flow, and trajectories need to be calculated on the basis of velocity field measurements. This problem can be simplified by using a Lagrangian formulation, in which case the only major difficulty is to express the influence of turbulence on calculated trajectories. Velocity fluctuations can be considered as pure random functions or related to turbulence correlations. These two methods were used to calculate trajectories of elementary fluid particles in a swirling decaying flow on the basis of hydrodynamic characteristics obtained by particle image velocimetry (PIV) studies. Trajectory dispersion was then compared with experimental results obtained by PIV measurements of the instantaneous flow field. This comparison shows the great dependence of velocity fluctuation (and thus of trajectories) on spatial correlations. Finally, the correct mathematical formulation of velocity fluctuation was checked by using the trajectory calculation algorithm to determine residence time distribution (RTD). A comparison with experimental RTD confirmed the efficiency of the method for determining trajectories in swirling decaying flow.     

Inverse method for the dynamical analysis of wall shear rates using three-segment probes in parallel plate rheometer

Mass transfer measurements were conducted on a Parallel Plate Rheometer (PPR) using the limiting diffusion current method, i.e. the polarography technique. The database constructed was exploited for the validation of the inverse method under a well-controlled unsteady shear flow. This method is based on a numerical sequential estimation. It has been applied to determine of the wall shear rate in the upper disk of the PPR. It requires the numerical inversion of the convection diffusion equation in order to apply it to instantaneous mass transfer measurements. This requires the use of electrochemical probe, which allows the determination of the local mass transfer rate for known flow kinematics. A multi-segment electrochemical probe has been used. The directional characteristics of the three-segment probe were highlighted. The directional angle effect and the frequencies of oscillations effect were studied in order to test the robustness of the inverse method within the presence of such factors. The obtained results demonstrate that the inverse method allows a good determination of the shear rate, which follows the experimental one for different cases tested in a satisfactory way.     

Chemical Synthesis and Isolation of Trans‐Palmitoleic Acid (Trans‐C16:1 n‐7) Suitable for Nutritional Studies

Trans‐palmitoleic acid (trans‐9 C16:1, or trans‐C16:1 n‐7, TPA) is typically found in ruminant‐derived foods (milk and meat). Of note, previous epidemiological studies associated high levels of circulating TPA with a lower risk of type 2 diabetes and metabolic syndrome in humans. At the current time, TPA intakes in humans are ensured by ruminant‐derived foods. However, due to the very low commercial availability of TPA, there are no supplementation studies carried out so far. Therefore, the ability for dietary TPA to prevent type 2 diabetes and metabolic syndrome has never been experimentally assessed. Here, a method (among others) to get dozens of grams of pure TPA as ethyl ester, to perform dedicated supplementation studies, is reported. For that purpose, it starts from food sources containing high amounts of cis‐palmitoleic acid (cis‐9 C16:1, or cis‐C16:1 n‐7, CPA), dealing with fatty acids ethyl esters all along the experiment. CPA is purified with flash liquid chromatography, then submitted to a cis/trans isomerization step. Finally, TPA is separated from CPA by low‐temperature crystallization in methanol. The final product is fully characterized by ¹H and ¹³C nuclear magnetic resonance spectrometry. It is possible to produce ≈70 g of 85%‐purity TPA suitable for nutritional studies. Practical Applications: The synthesized trans‐palmitoleic acid may serve for supplementation (or nutritional) studies aiming at unravelling its physiological impacts suggested by epidemiological work. Depending on the amount of synthesized trans‐palmitoleic acid, one may carry out nutritional studies on rodents or even on humans.     

Investigations in an external-loop airlift photobioreactor with annular light chambers and swirling flow

Photosynthetic microorganisms could serve as valuable compounds, but also for environmental applications. Their production under controlled conditions implies to design specific reactors, named photobioreactors, in which light supply is the main constraint. This paper was devoted to an original external-loop airlift photobioreactor (PBR) with annular light chambers in which a swirling motion was induced. The aim was to characterize this novel geometrical configuration in terms of gas-liquid hydrodynamics, and to test its potentiality for algal cultures. This PBR consisted of two identical columns connected by flanges defining tangential inlets, each column being made of two transparent concentric tubes (6 L in liquid volume, 50 m⁻¹ in specific illuminated area). Firstly, the global flow characteristics (circulation and mixing times) were determined by a tracer method and modelled by an axial dispersed plug flow with complete recirculation (Péclet number). By means of a double optical probe, both local and global time-averaged parameters of the gas phase were measured, namely void fraction, bubble velocity, frequency and size. The gas-liquid mass transfer were also characterized, in tap water and in culture medium, by measuring overall volumetric mass transfer coefficients. In a second time, cultures of the microalga Chlamydomonas reinhardtii were run in batch mode. The variations of biomass concentration and pigment content with time from inoculation were successfully obtained. All these findings highlighted: (i) some significant differences in terms of gas-liquid hydrodynamics between the present PBR and the usual airlift systems, (ii) the interest of this configuration for algal cultures, even if complementary studies and technological improvements are still required for definitively validating its scale-up.     

Elaboration of controlled structure foams with the SMX static mixer

A better control of the foaming process is important for food industry, as the structure of the liquid/gas mixture is a key parameter for the end‐used properties of foams. The main concern of this study is to present a methodology applicable to the parametric study of the foaming process that can help either to optimize the operating conditions or to adapt the formulation. We focused on the valorization of egg white proteins (EWPs). The method allows studying the effect of the process parameters on the foam structure and the effect of the thermal pretreatment of the EWP in the dry state on the rheology and the stability of foams. The foaming is achieved with a SMX10 static mixer, which allows the production of controlled structure foams. It is, therefore, possible to investigate the dependence of foam properties by comparing foams with the same alveolar structure in relation with their formulation. © 2012 American Institute of Chemical Engineers AIChE J, 59: 132–145, 2013     

Quantitative Analysis of Mutant Subclones in Chronic Myeloid Leukemia: Comparison of Different Methodological Approaches

Identification and quantitative monitoring of mutant BCR-ABL1 subclones displaying resistance to tyrosine kinase inhibitors (TKIs) have become important tasks in patients with Ph-positive leukemias. Different technologies have been established for patient screening. Various next-generation sequencing (NGS) platforms facilitating sensitive detection and quantitative monitoring of mutations in the ABL1-kinase domain (KD) have been introduced recently, and are expected to become the preferred technology in the future. However, broad clinical implementation of NGS methods has been hampered by the limited accessibility at different centers and the current costs of analysis which may not be regarded as readily affordable for routine diagnostic monitoring. It is therefore of interest to determine whether NGS platforms can be adequately substituted by other methodological approaches. We have tested three different techniques including pyrosequencing, LD (ligation-dependent)-PCR and NGS in a series of peripheral blood specimens from chronic myeloid leukemia (CML) patients carrying single or multiple mutations in the BCR-ABL1 KD. The proliferation kinetics of mutant subclones in serial specimens obtained during the course of TKI-treatment revealed similar profiles via all technical approaches, but individual specimens showed statistically significant differences between NGS and the other methods tested. The observations indicate that different approaches to detection and quantification of mutant subclones may be applicable for the monitoring of clonal kinetics, but careful calibration of each method is required for accurate size assessment of mutant subclones at individual time points.     

Transfert photonique dans un photoréacteur à écoulement tourbillonnaire

Photonic transfer has been analyzed for two hydrodynamic conditions in an annular photoreactor: a swirling decay- ing flow generated by a tangential inlet, and an axial flow generated by a radial inlet. The photonic transfer coefficient was determined by carrying out the homogeneous photoreduction of potassium ferrioxalate. A comparison of the two hydrodynamic conditions is made in aqueous solution and in a suspension of black carbon in order to reduce the light penetration depth. The last condition emphasizes the interest in using tridimensional flow to design a photoreactor.