A Catalytic Michael/Horner–Wadsworth–Emmons Cascade Reaction for Enantioselective Synthesis of Thiochromenes

A catalytic enantioselective sulfa‐Michael/Horner–Wadsworth–Emmons reaction cascade has been developed, taking advantage of phosphonate as an electrophilic activator and a traceless binding site. Using a chiral bifunctional urea derivative as the catalyst, a variety of aryl and heteroaryl substituted thiochromenes was obtained in excellent yield with a high level of enantioselectivity.     

NUMERICAL METHOD FOR THE PREDICTION OF INCOMPRESSIBLE FLOW AND HEAT TRANSFER IN DOMAINS WITH SPECIFIED PRESSURE BOUNDARY CONDITIONS

A variety of engineering applications involve incompressible flows in devices for which boundary pressures are known. The purpose of this article is to present a mathematical formulation and a computational method for the prediction of incompressible flow in domains with specified pressure boundaries. The computational treatment of specified pressure boundaries in complex geometries is presented within the framework of a nonstaggered technique based on curvilinear boundary-fitted grids. The construction of the discretization equations for unknown velocities on specified pressure boundaries and the solution of the discretization equations using the SIMPLE algorithm are discussed. The proposed method is applied for predicting incompressible forced flows in branched ducts and in buoyancy-driven flows. These examples illustrate the utility of the proposed method in predicting incompressible flows with specified boundary pressures encountered in practical applications.     

Role of physicochemical factors on bacterial attachment in textile fibrous media

One of the possible approaches to remove the Pseudomonas bacteria from surface water by using textile fibrous media has been studied in this article. The attachment of Pseudomonas bacteria inside textile fibrous media was studied using laboratory column experiment which led to the understanding of the physiochemical interaction between textile surface and the bacteria. Colloid‐filtration theory was used to investigate the effects of various physicochemical factors like pH, ionic strength (M) and mass (g) of the porous media on bacterial attachment. The quantitative assessment of bacterial attachment on the textile surface media was carried out by determining the collision efficiency. The physicochemical factors mentioned above were optimized to obtain maximum collision efficiency so as to achieve maximum bacterial attachment on the textile media surface. Bacterial attachment is found to be directly related to the ionic strength of the suspending medium and the mass of the textile media. A significant improvement in collision efficiency is observed when the ionic strength of the suspended medium is increased. Maximum collision efficiency is achieved at high level of ionic strength and medium level of pH with high level of mass of the textile media.     

Properties of spray-deposited cobalt oxide selective coatings on aluminium and galvanised iron substrates

Highly stable selective coatings of cobalt oxide have been prepared on commercial aluminium and galvanised iron substrates by the method of spray pyrolysis. The optothermal, structural and optical properties of these films have been investigated to determine the optimum growth parameters. Best selectivity values are obtained for films with thicknesses 0·30 μm on aluminium and 0·32 μm on galvanised iron. The optimised films on aluminium give = 0·88 and _100°C = 0·15 whereas those on galvanised iron give = 0·88 and _100°C = 0·13. The films are extremely adherent and are stable up to 500°C in the case of aluminium and 350°C in the case of galvanised iron substrates.     

Dynamic control of arabinose and xylose utilization in E. coli

The common bacterium Escherichia coli (E. coli) can utilize the pentose sugars arabinose and xylose for growth and energy. When fed both these sugars, the bacterium preferentially utilizes arabinose and only when all the arabinose is exhausted from the media does it start to use xylose. This hierarchical utilization of the two sugars is dictated by two proteins: AraC and XylR. These proteins act as controllers of sugar utilization and dictate the timing and rate of utilization of these sugars. While the biochemical interactions defining individual arabinose and xylose utilization systems are well understood, it is not completely understood how the hierarchical utilization is maintained by the bacterium, and how the regulatory crosstalk between the two systems facilitates this hierarchy. To help answer these questions, in this work, we systematically experimentally characterize the regulatory crosstalk between the two sugar utilization systems. Our work demonstrates extensive interaction between the two sugar systems. Specifically, data from our experiments suggest that the xylose system can regulate arabinose gene expression and consequently, cellular physiology dynamically via promiscuous transport and maybe through cross interactions between regulator and non‐cognate sugar. Put together, we demonstrate that arabinose and xylose utilization networks exhibit an example of distributed control in a biological system. This design likely ensures that the system does not fail under perturbations (mutations). Our results help understand multi‐process control in biological systems and bring to light design criteria for synthetic biology applications.

     

Rheological behavior of highly filled ethylene propylene diene rubber compounds

The rheological behavior of highly filled ethylene propylene diene rubber (EPDM) compounds was studied with respect to the effect of curative system, grafted rubber, shear rate, temperature and die swell using a Monsanto Processability Tester (MPT) to gain an understanding of the molecular parameters that control the surface finish. All systems show pseudoplastic behavior. At a particular shear rate, shear viscosity increases with blend ratio. The dependence of flow behavior on extrusion velocity indicates a surface effect. The extrudate die swell and maximum recoverable deformation are related by a linear relationship, which is independent of sulfur/accelerator ratio, extrusion temperature and shear rates and blend ratio. The principal normal stress difference increases nonlinearly with shear stress. Activation energy decreases with shear rate in most cases. The faster relaxing system produces extrudate of better surface quality.