Particle concentration measurement and flow regime identification in multiphase pipe flow using a generalised dual-frequency inversion method

An acoustic particle concentration measurement method, originally developed for marine sediment, in which the backscattered energy received by emitter-receiver transducers in the megahertz range is used to construct concentration profiles in suspensions of solid particles in a carrier fluid is applied to suspensions of general engineering interest. Four particle species with range of densities and sizes are used. Concentration profiles in horizontal, turbulent pipe flow at a Reynolds number of 50,000 and three nominal volume fractions are presented for each particle species, using experimentally determined acoustic coefficients, in order to isolate the influence of particle size and density on transport and settling in solid-liquid multiphase flows. It is clear from the results that the method allows the degree of segregation in real suspensions and slurries to be measured, and has a range of potential applications in the nuclear and minerals processing industries, for example. Lastly, the limiting conditions of the method are explored through the concept of an acoustic penetration depth

Activation of Host Translational Control Pathways by a Viral Developmental Switch

In response to numerous signals, latent herpesvirus genomes abruptly switch their developmental program, aborting stable host–cell colonization in favor of productive viral replication that ultimately destroys the cell. To achieve a rapid gene expression transition, newly minted capped, polyadenylated viral mRNAs must engage and reprogram the cellular translational apparatus. While transcriptional responses of viral genomes undergoing lytic reactivation have been amply documented, roles for cellular translational control pathways in enabling the latent-lytic switch have not been described. Using PEL-derived B-cells naturally infected with KSHV as a model, we define efficient reactivation conditions and demonstrate that reactivation substantially changes the protein synthesis profile. New polypeptide synthesis correlates with 4E-BP1 translational repressor inactivation, nuclear PABP accumulation, eIF4F assembly, and phosphorylation of the cap-binding protein eIF4E by Mnk1. Significantly, inhibiting Mnk1 reduces accumulation of the critical viral transactivator RTA through a post-transcriptional mechanism, limiting downstream lytic protein production, and impairs reactivation efficiency. Thus, herpesvirus reactivation from latency activates the host cap-dependent translation machinery, illustrating the importance of translational regulation in implementing new developmental instructions that drastically alter cell fate

The Composition of the Mobile Phase Affects the Dynamic Chiral Recognition of Drug Molecules by the Chiral Stationary Phase

More than half of all pharmaceuticals are chiral compounds. Although the enantiomers of chiral compounds have the same chemical structure, they can exhibit marked differences in physiological activity; therefore, it is important to remove the undesirable enantiomer. Chromatographic separation of chiral enantiomers is one of the best available methods to get enantio-pure substances, but the optimization of the experimental conditions can be very time-consuming. One of the most widely used chiral stationary phases, amylose tris(3,5-dimethylphenyl carbamate) (ADMPC), has been extensively investigated using both experimental and computational methods; however, the dynamic nature of the interaction between enantiomers and ADMPC, as well as the solvent effects on the ADMPC-enantiomer interaction, are currently absent from models of the chiral recognition mechanism. Here we use QM/MM and molecular dynamics (MD) simulations to model the enantiomers of flavanone on ADMPC in either methanol or heptane/2-propanol (IPA) (90/10) to elucidate the chiral recognition mechanism from a new dynamic perspective. In atomistic MD simulations, the 12-mer model of ADMPC is found to hold the 4/3 left-handed helical structure in both methanol and heptane/IPA (90/10); however, the ADMPC polymer is found to have a more extended average structure in heptane/IPA (90/10) than in methanol. This results from the differences in the distribution of solvent molecules close to the backbone of ADMPC leads to changes in the distribution of the (ρ, ψ) dihedral angles of the glycoside bond (between adjacent monomers) that define the structure of the polymer. Our simulations have shown that the lifetime of hydrogen bonds formed between ADMPC and flavanone enantiomers in the MD simulations are able to reproduce the elution order observed in experiments for both the methanol and the heptane/IPA solvent systems. Furthermore, the ratios of hydrogen-bonding-lifetime-related properties also capture the solvent effects, in that heptane/IPA (90/10) is found to make the separation between the two enantiomers of flavanone less effective than methanol, which agrees with the experimental separation factors of 0.9 versus 0.4 for R/S, respectively. © 2017 American Chemical Society