Modeling and experimental studies on combustion characteristics of porous coal char: Volume reaction model

A generalized single‐particle model for the prediction of combustion dynamics of a porous coal char in a fluidized bed is analyzed in the present work using a volume reaction model (VRM). A fully transient nonisothermal model involving both heterogeneous and homogeneous chemical reactions, multicomponent mass transfer, heat transfer with intraparticle resistances, as well as char structure evolution is developed. The model takes into account convection and diffusion inside the particle pores, as well as in the boundary layer. By addressing the Stefan flow originated due to nonequimolar mass transfer and chemical reactions, this work enables a more realistic analysis of the combustion process. The model, characterized by a set of partial differential equations coupled with nonlinear boundary conditions, is solved numerically using the implicit finite volume method (FVM) with a FORTRAN code developed in‐house. The use of a FVM for solving such an elaborate char combustion model, based on the VRM, was not reported earlier. Experiments consisting of fluidized‐bed combustion of a single char particle were carried out to determine the internal surface area of a partially burned char particle and to enable model validation. Predicted results are found to compare well with the reported experimental results for porous coal char combustion. The effects of various parameters (i.e., bulk temperature and initial particle radius) are examined on the dynamics of combustion of coal char. The phenomena of ignition and extinction are also investigated. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 299–315, 2010     

Rate coefficients for the reaction of OH with HONO between 298 and 373 K

Rate coefficients, k₁, for the reaction OH + HONO → H₂O + NO₂, have been measured over the temperature range 298 to 373 K. The OH radicals were produced by 266 nm laser photolysis of O₃ in the presence of a large excess of H₂O vapor. The temporal profiles of OH were measured under pseudo-first-order conditions, in an excess of HONO, using time resolved laser induced fluorescence. The measured rate coefficient exhibits a slight negative temperature dependence, with k₁ = (2.8 ± 1.3) × 10^?12 exp((260 ± 140)/T) cm³ molecule^?1 s^?1. The measured values of k₁ are compared with previous determinations and the atmospheric implications of our findings are discussed.     

Defect-Free Synthesis of a Fully π-Conjugated Helical Ladder Polymer and Resolution into a Pair of Enantiomeric Helical Ladders**

Fully π-conjugated ladder polymers with a spiral geometry represent a new class of helical polymers with great potential for organic nanodevices, but there is no precedent for an optically active helical ladder polymer totally composed of achiral units. We now report the defect-free synthesis and resolution of a fully π-conjugated helical ladder polymer with a rigid helical cavity, which has been achieved by quantitative and chemoselective acid-promoted alkyne benzannulations of a rationally designed, random-coil achiral polymer followed by chromatographic enantioseparation. Because of a sufficiently high helix-inversion barrier, the isolated excess one-handed helical ladder polymer with a degree of polymerization of more than 15 showed a strong circular dichroism with a dissymmetry factor of up to 1.7×10⁻² and is thermally stable, maintaining its optical activity in solution even at 100 °C, as well-supported by molecular dynamics simulation.     

A noble interaction: An assessment of noble gas binding ability of metal oxides (metal = Cu,Ag, Au)

An in silico study is performed on the structure and the stability of noble gas (Ng) bound MO complexes (M = Cu, Ag, Au). To understand the stability of these Ng bound complexes, dissociation energies, dissociation enthalpy, and dissociation free energy change are computed. The stability of NgMO is also compared with that of the experimentally detected NgMX (X= F, Cl, Br). It is found that MO has lower Ng binding ability than that of MX. All the dissociation processes producing Ng and MO are endothermic in nature and for the Kr‐Rn bound MO (M = Cu, Au), and Xe and Rn bound AgO cases, the corresponding dissociation processes are turned out to be endergonic in nature at standard state. The Wiberg bond indices of Ng? M bonds and Ng→M electron transfer gradually increase from Ar to Rn and for the same Ng they follow the order of NgAuO > NgCuO > NgAgO. Energy decomposition analysis shows that the Ng? M bonds in NgMO are partly covalent and partly electrostatic in nature. Electron density analysis further highlights the partial covalent character in Ng? M bonds. © 2016 Wiley Periodicals, Inc.     

Fluid flow and heat transfer characteristics for a square prism (blockage ratio = 0.1) placed inside a wind tunnel

Experimental investigations in fluid flow and heat transfer have been carried out to study the effect of wall proximity due to flow separation around a square prism at Reynolds number 2.6 × 10⁴, blockage ratio 0.1, different height-ratios and various angles of attack. The static pressure distribution has been measured on all faces of the square prism. The results have been presented in the form of pressure coefficient, drag coefficient for various height-ratios. The pressure distribution shows positive values on the front face whereas on the rear face negative values of the pressure coefficient have been observed. The positive pressure coefficient for different height-ratios does not vary too much but the negative values of pressure coefficient are higher for all points on the surface as the bluff body approaches towards the upper wall of the wind tunnel. The drag coefficient decreases with the increase in angle of attack as the height-ratio decreases. The maximum value of drag coefficient has been observed at an angle of attack nearly 50° for the square prism at all height-ratios. The heat transfer experiments have been carried out under constant heat flux condition. Heat transfer coefficient are determined from the measured wall temperature and ambient temperature and presented in the form of Nusselt number. Both local and average Nusselt numbers have been presented for various height-ratios. The variation of local Nusselt number has been shown with non-dimensional distance for different angles of attack. The variation of average Nusselt number has also been shown with different angles of attack. The local as well as average Nusselt number decreases as the height-ratio decreases for all non-dimensional distance and angle of attack, respectively, for the square prism. The average Nusselt number for the square prism varies with the angle of attack. But there is no definite angle of attack at which the value of average Nusselt number is either maximum or minimum.     

Capturing a Pentacyclic Fragment-Based Library Derived from Perophoramidine: Their Design,Synthesis and Evaluation as Anticancer Compounds by DNA Double-Strand Breaks (DSB) and PARP-1 Inhibition

Herein we have reported the discovery of a pentacyclic building block comprised of fused indole-quinoline and piperidinone from the natural product perophoramidine as a formidable anticancer agent. The compounds were synthesized in six steps where the key steps involved a blue LED mediated intramolecular cyclopropanation of the indole intermediates and concomitant reduction of the associated aryl nitro moiety to nitroso in the molecule. Cytotoxicity screening of the compounds against an array of cancer cells that is, MCF7, HCT116 and A549 demonstrated 0.6 to 9 μM IC₅₀s by few of the compounds. γH2AX immunofluorescence assay of the two most potent molecules from the phenotypic screening with anti-γ-H2AX Alexa Fluor 488 antibody revealed extensive DNA damage of the A549 cells which indicated probable PARP inhibition (similar to Perophoramidine). Through molecular docking and molecular dynamic (MD) simulation studies the binding efficiency of our compounds with poly(ADP-ribose)polymerase 1 (PARP 1) enzyme was determined. Chemiluminescent PARP Assay with Histone-coated strips indicated that the most active compounds from the phenotypic screening induced PARP-1 inhibition with IC₅₀s of 1.3→1.5 μM.     

Spectra of K3Mn(CN)6

The polarised optical spectra of single crystal of K₃Mn(CN)₆ is reported at liquid nitrogen temperature. A new system of transition is located along with its hot components which is verified by temperature variation studies. The crystal field parameters to reproduce the bands are given.