Analysis of unsteady gas–liquid flows in a rectangular tank: Comparison of Euler–Eulerian and Euler–Lagrangian simulations

We study the dynamics of gas–liquid flows experimentally and computationally in a rectangular bubble column where the gas source is introduced at the corner. The flow in this reactor is complex and inherently unsteady in nature. The two-dimensional liquid phase velocity field is calculated by an Eulerian approach solving the unsteady Reynolds Averaged Navier Stokes equations. The conservation equations are closed using a two parameter turbulence model. The two-way coupling was accounted for by adding source terms in the conservation equations of the continuous phase to take into account the interaction with the dispersed phase. Bubble tracking is achieved through a Lagrangian approach. Here the equations of motion are solved taking into account the drag, pressure, buoyancy and gravity forces. The time-averaged flows along with the variables which characterize turbulence are analyzed for a wide range of gas flow-rates using Euler–Lagrangian simulations. These simulation predictions are validated with Euler–Eulerian simulations where the gas-phase distribution is captured as a void fraction and PIV experiments. The motion of bubbles induces turbulence in the flow. The applicability of two parameter models for turbulence like the standard k–ε model on time-averaged flow properties is addressed. From the results of the time averaged velocity field, turbulence intensity, turbulent viscosity and gas hold-up profiles, it is concluded that the Euler–Lagrangian model is applicable at lower gas flow-rates. The Euler–Eulerian approach was found to be valid at lower as well as higher gas flow-rates.     

In Silico Approach Using Free Software to Optimize the Antiproliferative Activity and Predict the Potential Mechanism of Action of Pyrrolizine-Based Schiff Bases

In the current study, a simple in silico approach using free software was used with the experimental studies to optimize the antiproliferative activity and predict the potential mechanism of action of pyrrolizine-based Schiff bases. A compound library of 288 Schiff bases was designed based on compound 10, and a pharmacophore search was performed. Structural analysis of the top scoring hits and a docking study were used to select the best derivatives for the synthesis. Chemical synthesis and structural elucidation of compounds 16a–h were discussed. The antiproliferative activity of 16a–h was evaluated against three cancer (MCF7, A2780 and HT29, IC₅₀ = 0.01–40.50 μM) and one normal MRC5 (IC₅₀ = 1.27–24.06 μM) cell lines using the MTT assay. The results revealed the highest antiproliferative activity against MCF7 cells for 16g (IC₅₀ = 0.01 μM) with an exceptionally high selectivity index of (SI = 578). Cell cycle analysis of MCF7 cells treated with compound 16g revealed a cell cycle arrest at the G₂/M phase. In addition, compound 16g induced a dose-dependent increase in apoptotic events in MCF7 cells compared to the control. In silico target prediction of compound 16g showed six potential targets that could mediate these activities. Molecular docking analysis of compound 16g revealed high binding affinities toward COX-2, MAP P38α, EGFR, and CDK2. The results of the MD simulation revealed low RMSD values and high negative binding free energies for the two complexes formed between compound 16g with EGFR, and CDK2, while COX-2 was in the third order. These results highlighted a great potentiality for 16g to inhibit both CDK2 and EGFR. Taken together, the results mentioned above highlighted compound 16g as a potential anticancer agent.     

Ultrafast diagnosis of the genetic-related disorders using the combined technologies of multiplex PCR and multichannel microchip electrophoresis.

For the diagnosis of unexplained male infertility a multiplex PCR for 6 markers, which are well-known as candidate genes for studying male infertility and located on the human Y-chromosome, has been designed. The multiplex PCR products have been separated on a 12 channel microchip electrophoresis system, which can analyze different samples simultaneously. By combining the technologies of multiplex PCR with multichannel microchip electrophoresis, the number of the DNA markers that can be screened simultaneously is increased to be 72 marker (12 x 6) in a single run while the electrophoresis analysis time is reduced to be only 180 s.     

Converging spherical and cylindrical shocks with zero temperature gradient in the rear flow field

Résumé Nous avons étudié les ondes de choc sphériques et cylindriques convergentes près du centre (ou de l'axe) de l'implosion, lorsque celles-ci sont devenues intenses et que l'écoulement qui les suit est devenu «semblable à lui-même», ayant «oublié» les conditions initiales. Un tel écoulement devient probablement isotherme à cause de l'échange thermique intense par conduction ou par rayonnement. Nous avons donc étudié un écoulement isotherme à un moment donné, plutôt que l'écoulement adiabatique habituellement supposé (Guderley, 1942). Les deux genres d'écoulement sont comparés. Nous avons calculé l'exposant de la loi de la propagation des ondes de choc par la règle caractéristique de Whitham (1958) pour des valeurs différentes de =c _p/c _v; nous l'avons comparé avec l'exposant exact obtenu par l'intégration numérique des équations de similarité. Les deux valeurs ne concordent pas aussi bien que lorsque l'on admet que l'écoulement qui suit l'onde de choc est adiabatique.     

EXCITED STATE INTERACTIONS OF 7-AZAINDOLE WITH ALCOHOL AND WATER

Abstract— The fluorescence spectrum of 7-azaindole in alcohol is composed of two fluorescence bands. Effects of pH, temperature and solvent deuteration on the fluorescence spectra and quantum yields of 7-azaindole and other model compounds in ethanol and in water are reported. The long wavelength band arises from a tautomeric species formed in an adiabatic photoreaction involving double proton transfer between one molecule of 7-azaindole and one molecule of alcohol.
The fluorescence spectrum of 7-azaindole in water is composed of only one band, but the emission is weak and shows a large solvent isotope effect. The possibility of a double proton transfer reaction between 7-azaindole and water is discussed.     

Voltammetric oxidation of anthraquinones in acetonitrile and nitromethane

The voltammetric oxidation of seven anthraquinones to the singly-charged radical cations has been investigated in acetonitrile and nitromethane. The voltammetric waves can be used for the quantitative determination of anthraquinones. Benzoquinones, naphthaquinones and phenanthraquinones are not oxidized in these solvents.     

Heavy Vacuum Gas Oil Upregulates the Rhamnosyltransferases and Quorum Sensing Cascades of Rhamnolipids Biosynthesis in Pseudomonas sp. AK6U

We followed a comparative approach to investigate how heavy vacuum gas oil (HVGO) affects the expression of genes involved in biosurfactants biosynthesis and the composition of the rhamnolipid congeners in Pseudomonas sp. AK6U. HVGO stimulated biosurfactants production as indicated by the lower surface tension (26 mN/m) and higher yield (7.8 g/L) compared to a glucose culture (49.7 mN/m, 0.305 g/L). Quantitative real-time PCR showed that the biosurfactants production genes rhlA and rhlB were strongly upregulated in the HVGO culture during the early and late exponential growth phases. To the contrary, the rhamnose biosynthesis genes algC, rmlA and rmlC were downregulated in the HVGO culture. Genes of the quorum sensing systems which regulate biosurfactants biosynthesis exhibited a hierarchical expression profile. The lasI gene was strongly upregulated (20-fold) in the HVGO culture during the early log phase, whereas both rhlI and pqsE were upregulated during the late log phase. Rhamnolipid congener analysis using high-performance liquid chromatography-mass spectrometry revealed a much higher proportion (up to 69%) of the high-molecularweight homologue Rha–Rha–C₁₀–C₁₀ in the HVGO culture. The results shed light on the temporal and carbon source-mediated shifts in rhamonlipids’ composition and regulation of biosynthesis which can be potentially exploited to produce different rhamnolipid formulations tailored for specific applications.     

Green synthesis of new thiouracilodepsipeptides in ionic liquid: One‐pot four‐component reaction of isocyanides

Thiouracil‐containing depsipeptides were produced via one‐pot four‐component condensation/Passerini tandem reaction of thiouracil, 2‐chloroacetic acid derivatives, ketones, and isocyanides in ionic liquid as green reaction media in high yields.     

Palladium‐Mediated Cleavage of Proteins with Thiazolidine‐Modified Backbone in Live Cells

Chemical protein synthesis and biorthogonal modification chemistries allow production of unique proteins for a range of biological studies. Bond‐forming reactions for site‐selective protein labeling are commonly used in these endeavors. Selective bond‐cleavage reactions, however, are much less explored and still pose a great challenge. In addition, most of studies with modified proteins prepared by either total synthesis or semisynthesis have been applied mainly for in vitro experiments with very limited extension to live cells. Reported here is an approach for studying uniquely modified proteins containing a traceless cell delivery unit and palladium‐based cleavable element for chemical activation, and monitoring the effect of these proteins in live cells. This approach is demonstrated for the synthesis of a caged ubiquitin‐aldehyde, which was decaged for the inhibition of deubiquitinases in live cells.