Control of vortex formation from a vertical cylinder in shallow water: Effect of localized roughness elements

Vortex formation from a vertical cylinder in shallow water is controlled by placement of a narrow transverse strip of roughness elements on the bed (bottom surface). A technique of high-image-density particle image velocimetry is employed to obtain global, instantaneous representations of the flow patterns, which lead to phase- and time-averaged patterns of streamline topology and Reynolds stress on planes at and above the bed. Near the bed, the overall form of the streamline topology is maintained, even at larger heights of the roughness elements. With increasing height of the elements, the downstream saddle point is further displaced in the streamwise direction. Correspondingly, the streamwise extent of the negative pocket of the streamwise velocity component, i.e., the region of reverse flow along the bed surface, increases substantially in the streamwise direction. The Reynolds stress in the very near-wake, at locations upstream of the roughness elements, is significantly attenuated, even for small height of roughness. This attenuation occurs not only near the bed surface, but also at the midplane of the shallow water wake, and thereby indicates that the consequence of localized roughness is to exert a global influence. In fact, corresponding patterns of instantaneous velocity and vorticity indicate that consistent formation of large-scale vortices in the very near-wake region is attenuated with relatively small surface roughness on the bed. Downstream of the roughness elements, the patterns of Reynolds stress near the bed surface, as well as at the midplane of the water layer, are significantly altered relative to the case of no roughness. Near the bed, highly concentrated patterns of positive and negative Reynolds stress in the absence of roughness give way to lower-level regions of Reynolds stress in the form of alternating concentrations; the particular pattern depends on the height of the roughness elements. At the midplane of the water layer, the Reynolds stress patterns maintain their same overall form, but the extrema of the Reynolds stress concentrations are attenuated in magnitude and are shifted in the downstream direction, with increasing height of the roughness elements. These observations are complemented by patterns of instantaneous velocity and vorticity.     

Entropy analysis for third grade fluid flow with Vogel model viscosity in annular pipe

The steady-state flow of a third grade fluid between concentric circular cylinders is considered and entropy generation due to fluid friction and heat transfer in the annular pipe is examined. Depending upon the fluid viscosity, entropy generation in the flow system varies. The third grade fluid is employed to account for the non-Newtonian effect while Vogel model is accommodated for temperature-dependent viscosity. The analysis is based on perturbation technique. The closed form solutions for velocity, temperature and entropy fields are presented. Entropy generation due to fluid friction and heat transfer in the flow system is formulated. The influence of viscosity parameters A and B on the entropy generation number is investigated. It is found that entropy generation number reduces with increasing viscosity parameter A, which is more pronounced in the region close to the annular pipe inner wall and opposite is true for increasing viscosity parameter B.     

All-optical transistor action with bistable switching in a photonic crystal cross-waveguide geometry

We demonstrate all-optical switching action in a nonlinear photonic crystal cross-waveguide geometry with instantaneous Kerr nonlinearity, in which the transmission of a signal can be reversibly switched on and off by a control input. Our geometry accomplishes both spatial and spectral separation between the signal and the control in the nonlinear regime. The device occupies a small footprint of a few micrometers squared and requires only a few milliwatts of power at a 10-Gbit/s switching rate by use of Kerr nonlinearity in AlGaAs below half the electronic bandgap. We also show that the switching dynamics, as revealed by both coupled-mode theory and finite-difference time domain simulations, exhibits collective behavior that can be exploited to generate high-contrast logic levels and all-optical memory.     

4-[(3-Bromo-4-hydroxy­phenyl)­amino]-6,7-di­methoxyquinazolin-1-ium chloride methanol solvate and 4-­[(3-hydroxy­phenyl)­amino]-6,7-di­methoxy-1-quinazolinium chloride

The title compounds, C₁₆H₁₅BrN₃O₃⁺·Cl⁻·CH₄O (WHI–P154) and C₁₆H₁₆N₃O₃⁺·Cl⁻ (WHI–P180), are potent inhibitors [WHI–P154 with IC₅₀ = 5.6 µM and WHI–P180 with IC₅₀ = 4.0 µM for epidermal growth factor receptor (EGFR) kinase inhibition] of the EGFR tyrosine kinase as well as Janus Kinase 3. The molecular structures of these compounds are very similar except for the dihedral angle between the anilino and quinazoline moieties which is 1.10 (5)° for WHI–P154, and 45.66 (6) and 25.29 (7)° for the two mol­ecules of WHI–P180 in the asymmetric unit. The nitro­gen at the N3 position is protonated in both structures and participates in hydrogen bonding with the chlorine anions.     

Retrieving seasonally adjusted quarterly growth rates from annual growth rates that are reported quarterly

Most macroeconomic time series are reported on a quarterly basis. However, in many cases, official statistical agencies report annual (or ‘year-on-year’) growth rates rather than the quarterly data themselves. In this paper, we demonstrate how to recover seasonally adjusted quarterly growth rates from annual growth rates that are reported quarterly. As an illustration, we apply the technique to the highly seasonal UK Retail Sales series. Using only the annual growth rates calculated from the underlying data, we find that our procedure generates estimated seasonally adjusted quarterly growth rates that are almost indistinguishable from the ‘true’ seasonally adjusted quarterly growth rates.     

Novel metal complexes containing 6-methylpyridine-2-carboxylic acid as potent α-glucosidase inhibitor: synthesis,crystal structures,DFT calculations,and molecular docking

Molecular Diversity - The World Health Organization (WHO) report shows that diabetes mellitus (DM) will be one of the ten deadly diseases in the near future. The best way to prevent DM is to...     

Copper(II) complexes with pyridine-2,6-dicarboxylic acid from the oxidation of copper(I) iodide

Via an oxidation reaction of Cu(I) iodide with pyridine-2,6-dicarboxylic acid (H₂L) in DMF three copper(II) complexes, [(CH₃)₂NH₂]₂[CuL₂] (1), K₂[CuL₂]?H₂L?H₂O (2) and [Cu(L)(H₂O)]_n (3), were synthesized and characterized. The structures of 1–3 were determined by single crystal X-ray diffraction studies. In-situ DMF decomposition produces dimethylamine base under solvothermal conditions and a proton transfer reaction takes place for the complex formation of 1. 3-D networks are stabilized in 1 and 2 via hydrogen bonds. Complex 3 is a 1-D coordination polymer with Cu-O semi-coordination bonds. Thermal decomposition of the complexes results in the corresponding metal oxides. Also, the electrochemical behavior of 1 was determined to be a metal-centered and diffusion-controlled, one-electron reduction process.     

Enantioselective synthesis of cyclic, quaternary oxonitriles

Quaternary oxonitriles are stereoselectively generated from the union of five-, six-, and seven-membered 2-chloroalkenecarbonitriles with chiral alcohols via a Claisen rearrangement. The strategy rests on a new conjugate addition-elimination of allylic alkoxides to 2-chlorocycloalkenecarbonitriles to afford substituted 2-alkoxyalkenenitriles. Subsequent thermolysis unmasks a cyclic oxonitrile while selectively forming a new quaternary center with enantiomeric ratios typically greater than 9:1. The overall alkylation strategy addresses the challenge of enantioselectively generating hindered, quaternary centers while simultaneously installing ketone, nitrile, and olefin functionalities.