Hybrid atomistic�Ccontinuum simulations of fluid flows involving interfaces

In this work, we use an hybrid atomistic–continuum (HAC) simulation method to study transient and steady isothermal flows of Lennard-Jones fluids near interfaces. Our hybrid method is based on a domain decomposition algorithm. The flow domain is composed of two overlapping regions: an atomistic region described by molecular dynamics, and a continuum region described by a finite volume discretization of the incompressible Navier–Stokes equations. To show the interest of such an hybrid method to compute flows near fluid/solid interface, we first applied our hybrid scheme to the classical Couette flow, where the moving wall is modelled at the atomistic scale. In addition, we also studied an oscillatory shear flow. Then, to compute flows near fluid/fluid interface, we applied our method to a two-phase Couette flow (liquid/gas), where the interface is modelled at the molecular scale. We show that hybrid results can sometimes differ from those provided by analytical solutions deduced from continuum mechanics equations combined with usual boundary/interface relations. For the Couette and oscillatory shear flows, a good agreement is found between hybrid simulations and macroscopic analytical solutions, however, we noticed that the fluid in contact with the wall can be more entailed than what expected. For the liquid/gas Couette flow, the hybrid simulation exhibits an unexpected jump of the velocity in the interfacial region, corresponding to a partial slip between the two fluid phases. Those interesting results highlight the interest of using an HAC method to deal with systems for which surfaces/interfaces effects are important.     

Contribution of Yeast Studies to the Understanding of BCL-2 Family Intracellular Trafficking

BCL-2 family members are major regulators of apoptotic cell death in mammals. They form an intricate regulatory network that ultimately regulates the release of apoptogenic factors from mitochondria to the cytosol. The ectopic expression of mammalian BCL-2 family members in the yeast Saccharomyces cerevisiae, which lacks BCL-2 homologs, has been long established as a useful addition to the available models to study their function and regulation. In yeast, individual proteins can be studied independently from the whole interaction network, thus providing insight into the molecular mechanisms underlying their function in a living context. Furthermore, one can take advantage of the powerful tools available in yeast to probe intracellular trafficking processes such as mitochondrial sorting and interactions/exchanges between mitochondria and other compartments, such as the endoplasmic reticulum that are largely conserved between yeast and mammals. Yeast molecular genetics thus allows the investigation of the role of these processes on the dynamic equilibrium of BCL-2 family members between mitochondria and extramitochondrial compartments. Here we propose a model of dynamic regulation of BCL-2 family member localization, based on available evidence from ectopic expression in yeast.     

Dissolution and geopolymerization of synthetic fly ash glass

Journal of Materials Science - Two fly ash glasses were synthesized and dissolved in KOH at a water/solid ratio of?≤?0.3. We measured reaction kinetics, gel formation, and...     

Systemic Concocting of Cross-Linked Enzyme Aggregates of Candida antarctica Lipase B (Novozyme 435) for the Biomanufacturing of Rhamnolipids

In the present study, Candida antarctica lipase B was immobilized on amine-functionalized silica microspheres as cross-linked enzyme aggregates (CLEA) and utilized for the biomanufacturing of rhamnolipids (RL). Lipase CLEA synthesized under optimized conditions of 2.0:1.0 by volume of silica microsphere/enzyme concentration, a 1.0:2.5 (v/v) ratio of enzyme/2-propanol, 7 mM glutaraldehyde concentration, when incubated at pH 9.0 and 40 °C, for a cross-linking time of 30 min were observed to exhibit superior biocatalytic properties and a maximum enzyme load of 770 U g⁻¹. Lipase CLEA exhibited enhanced pH stability in acidic and alkaline media and increased temperature resistance as compared to free lipase. Both free and CLEA lipases were used to synthesize RL in different solvent systems. After 12 h, from initiation of the esterification, the degree of esterification (molar conversion yield) reached 46% and 71% in the batch mode. ¹H and ¹³C nuclear magnetic resonance (NMR) and high-performance liquid chromatographic (HPLC) analysis confirm RL production by CLEA lipase. The CLEA showed greater confrontation to enzyme-mediated bioprocess approach as compared to its soluble counterpart and exhibited excellent RL production and catalytic activity even after its tenth successive reuse.     

Robust Detection of Somatic Mosaicism and Repeat Interruptions by Long-Read Targeted Sequencing in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is the most complex and variable trinucleotide repeat disorder caused by an unstable CTG repeat expansion, reaching up to 4000 CTG in the most severe cases. The genetic and clinical variability of DM1 depend on the sex and age of the transmitting parent, but also on the CTG repeat number, presence of repeat interruptions and/or on the degree of somatic instability. Currently, it is difficult to simultaneously and accurately determine these contributing factors in DM1 patients due to the limitations of gold standard methods used in molecular diagnostics and research laboratories. Our study showed the efficiency of the latest PacBio long-read sequencing technology to sequence large CTG trinucleotides, detect multiple and single repeat interruptions and estimate the levels of somatic mosaicism in DM1 patients carrying complex CTG repeat expansions inaccessible to most methods. Using this innovative approach, we revealed the existence of de novo CCG interruptions associated with CTG stabilization/contraction across generations in a new DM1 family. We also demonstrated that our method is suitable to sequence the DM1 locus and measure somatic mosaicism in DM1 families carrying more than 1000 pure CTG repeats. Better characterization of expanded alleles in DM1 patients can significantly improve prognosis and genetic counseling, not only in DM1 but also for other tandem DNA repeat disorders.     

Optimizing the early detection of low pathogenic avian influenza H7N9 virus in live bird markets

In Southeast Asia, surveillance at live bird markets (LBMs) has been identified as crucial for detecting avian influenza viruses (AIV) and reducing the risk of human infections. However, the design of effective surveillance systems in LBMs remains complex given the rapid turn-over of poultry. We developed a deterministic transmission model to provide guidance for optimizing AIV surveillance efforts. The model was calibrated to fit one of the largest LBMs in northern Vietnam at high risk of low pathogenic H7N9 virus introduction from China to identify the surveillance strategy that optimizes H7N9 detection. Results show that (i) using a portable diagnostic device would slightly reduce the number of infected birds leaving the LBM before the first detection, as compared to a laboratory-based diagnostic strategy, (ii) H7N9 detection could become more timely by sampling birds staying overnight, just before new susceptible birds are introduced at the beginning of a working day, and (iii) banning birds staying overnight would represent an effective intervention to reduce the risk of H7N9 spread but would decrease the likelihood of virus detection if introduced. These strategies should receive high priority in Vietnam and other Asian countries at risk of H7N9 introduction.     

Simulation of nanosecond IR laser annealing of cerium gadolinium oxide

Laser induced densification of ceramic oxide has shown great promises. However to control this process in regards of the final properties of the material, it is necessary to understand phenomena occurring during laser matter interaction, especially heat diffusion through the material. A thermal simulation of cerium gadolinium oxide (CGO) submitted to infrared laser pulses is presented. In order to determine the temperature profile during laser treatment, optical properties of CGO must be known; for this purpose, ellipsometry measurements were performed in order to obtain absorption coefficient and reflectivity. Finally, a thermal model based on heat equation was developed. Experimental observations of irradiated CGO surfaces were in agreement with the simulation results, in particular at maximum temperature when the material reaches fusion.     

Influence of the carbon texture of platinum/carbon aerogel electrocatalysts on their behavior in a proton exchange membrane fuel cell cathode

Seven carbon aerogels (CAs) with different pore size distributions were synthesized and used as a catalyst support in proton exchange membrane fuel cell (PEMFC) cathodes. The cathodes were tested in 50 cm² membrane electrode assemblies. The results demonstrate that the CA texture significantly influences performance by impacting gas diffusion and proton transport. Also, the Nafion^® loading must be adapted to the CA texture, since its easier penetration into large pores favors their obstruction and results in higher proton resistance and mass-transport voltage losses. Under fixed experimental conditions (notably Nafion^®/carbon ratio = 1), the best CA support displays high specific surface area and pore volume, a majority of mesopores with a pore size distribution peak around 25–30 nm and with some macropores. The work confirms that the carbon support structure must be controlled to reduce mass-transport voltage losses. Doing so would lead to reduce PEMFC overall cost per kW.     

Analyzing the influence of different synthetic talcs in waterborne polyurethane nanocomposites obtainment

Waterborne polyurethane (WPU) nanocomposites were produced utilizing synthetic talc in gel form in order to improve its physical–chemical properties. Synthetic talc manufactured in nano‐gel form are interesting because their interaction with water occurs through hydrogen bonding favoring fillers dispersion within the WPU matrix. WPUs are environmental friendly materials because no organic solvents are used in its production. The nanocomposites obtained with the three synthetic talc nano‐gel fillers presented a good dispersion even when higher amounts of fillers were added, as seen by X‐ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, and atomic force microscopy analyses. The addition of synthetic talcs improved WPU nanocomposites mechanical properties. Storage and loss modulus results proved fillers incorporation into the WPU matrix corroborating with Fourier transform infrared spectroscopy results. Results demonstrated that synthetic talcs in nano‐gel form are interesting to obtain WPU nanocomposites with superior mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46107.