Pseudo-Fluid Simulation of Transient Behaviors in a CFB Riser

The kinetic theory of granular flow (KTGF) is modified to fit the Einstein's equation for effective viscosity of dilute flow. A pseudo-fluid approach based on this modified KTGF is used to simulate the dynamic formation and dissipation of clusters in a circulating fluidized bed riser. The agglomeration of particles reduces slip velocity within particle clusters, and hence results in two reverse trends: discrete particles are lifted by air while particle clusters fall down along the wall. The dynamic equilibrium of these two types of motion leads to the characteristic sigmoid profile of solid concentration along the longitudinal direction. The predicted solid velocity, lateral and longitudinal profiles of solid volume fraction and annulus thickness are in reasonable agreement with experimental results

Simulation of the clustering phenomenon in a fast fluidized bed:The importance of drag correlation

Drag force is a key parameter in the numerical modeling of gas-particle flow in circulating fluidized beds. The reliability of current drag force correlations over the regime of fast fluidization has, however, not been thoroughly investigated. In this article, a drag force correlation accounting for the clustering effects for Geldart A particles is used to simulate the behaviors typical of fast fluidization, including dynamic evolution of clusters as well as time- averaged axial and lateral voidage profiles. Diverse images of clusters are captured and the time-averaged profiles of voidage are shown to be in quantitative agreement with the present empirical correlation. The results based on different constitutive correlations of drag force show the importance of the choice of drag force in modeling fast-fluidized beds. This drag force correlation, based on a simple averaging assumption, could give some basic insights about the magnitude of the drag reduction

Olefin Preparation via Palladium-Catalyzed Oxidative De-Azotative and De-Sulfitative Internal Cross-Coupling of Sulfonylhydrazones

A novel reactivity of sulfonylhydrazones under Pd catalysis is described, where SO₂ and N₂ are formally extruded to afford the product of an apparent internal coupling reaction. The reaction is effective with both carbocyclic and heterocyclic aromatic precursors

Palladium-Catalyzed Coupling of Sulfonylhydrazones with Heteroaromatic 2‑Amino-Halides (Barluenga Reaction): Exploring the Electronics of the Sulfonylhydrazone

This paper describes a new reactivity of the Pd-catalyzed coupling of 2-amino-3-bromo-aromatic and heteroaromatic compounds with sulfonylhydrazones (Barluenga reaction).The new catalyst system and modulation of the electronic nature of hydrazone that were needed for successful reaction are described herein

RALF1-FERONIA complex affects splicing dynamics to modulate stress responses and growth in plants

Wang L, Yang T, Wang B, et al. RALF1-FERONIA complex affects splicing dynamics to modulate stress responses and growth in plants. SCIENCE ADVANCES. 2020;6(21): eaaz1622.The environmentally responsive signaling pathways that link global transcriptomic changes through alternative splicing (AS) to plant fitness remain unclear. Here, we found that the interaction of the extracellular rapid alkalinization FACTOR 1 (RALF1) peptide with its receptor FERONIA (FER) triggered a rapid and massive RNA AS response by interacting with and phosphorylating glycine-rich RNA binding protein7 (GRP7) to elevate GRP7 nuclear accumulation in Arabidopsis thaliana. FER-dependent GRP7 phosphorylation enhanced its mRNA binding ability and its association with the spliceosome component U1-70K to enable splice site selection, modulating dynamic AS. Genetic reversal of a RALF1-FER-dependent splicing target partly rescued mutants deficient in GRP7. AS of GRP7 itself induced nonsense-mediated decay feedback to the RALF1-FER-GRP7 module, fine-tuning stress responses, and cell growth. The RALF1-FER-GRP7 module provides a paradigm for regulatory mechanisms of RNA splicing in response to external stimuli

An Efficient Catalytic Asymmetric Synthesis of a β²‑Amino Acid on Multikilogram Scale

We describe herein a scalable catalytic asymmetric hydrogenation process for the multikilogram-scale production of a β²-amino acid. A short and efficient synthesis of the starting unsaturated <i>N</i>-Boc-protected β²-enamide was developed followed by extensive catalysis screening and optimization studies that identified a simple Ru-BINAP catalyst system to directly afford the (<i>S</i>) product in high enantiomeric excess and yield. The final process enabled the multikilogram production in >99% ee, to be used as a key component for one of our clinical candidates

Stereoselective C-Glycosylation Reactions with Arylzinc Reagents

A general, transition-metal-free, highly stereoselective cross-coupling reaction between glycosyl bromides and various arylzinc reagents leading to β-arylated glycosides is reported. The stereoselectivity of the reaction is explained by invoking anchimeric assistance via a bicyclic intermediate. Stereochemical probes confirm the participation of the 2-pivaloyloxy group. Finally, this new method was applied to a short and efficient stereoselective synthesis of Dapagliflozin and Canagliflozin