Lattice Boltzmann simulation of natural convection in nanofluid-filled 2D long enclosures at presence of magnetic field

In this paper, the effects of a magnetic field on natural convection flow in filled long enclosures with Cu/water nanofluid have been analyzed by lattice Boltzmann method. This study has been carried out for the pertinent parameters in the following ranges: the Rayleigh number of base fluid, Ra = 10³–10⁵, the volumetric fraction of nanoparticles between 0 and 6 %, the aspect ratio of the enclosure between A = 0.5 and 2. The Hartmann number has been varied from Ha = 0 to 90 with interval 30 while the magnetic field is considered at inclination angles of θ = 0°, 30°, 60° and 90°. Results show that the heat transfer decreases by the increment of Hartmann number for various Rayleigh numbers and the aspect ratios. Heat transfer decreases with the growth of the aspect ratio but this growth causes the effect of the nanoparticles to increase. The magnetic field augments the effect of the nanoparticles at high Rayleigh numbers (Ra = 10⁵). The effect of the nanoparticles rises for high Hartmann numbers when the aspect ratio increases. The rise in the magnetic field inclination improves heat transfer at aspect ratio of A = 0.5.     

Flowfield characteristics on a vent slot mixer in supersonic flow

A research was conducted on a new mixing device referred as a “vent slot mixer”, using experimental and computational methods. The experiment was conducted in a laboratory-scale supersonic wind-tunnel of Mach number 2. Inflow air was under atmospheric air condition, and hydrogen gas was used as fuel. In addition, the computational simulation approach was performed to support the experimental result. The vent slot mixer can directly entrain the main airflow into the recirculation region, inducing complex flow structures in the recirculation region. This also leads to gradual development of the shear layer to reduce the total pressure loss mainly induced by a recompression shock. Contrary to typical shear layers of step mixer, for the vent slot mixer, two-dimensional large-scale structures and weak shocks were clearly identified around the shear layer through experimental and computational methods. When the fuel was injected from one circular injector in the recirculation region, the high fuel concentration of the vent slot mixer was evenly distributed along the spanwise direction, but with the step mixer the fuel was highly concentrated along the region downstream of the injector. Therefore, the vent slot mixer is effective to uniformly spread the fuel toward the spanwise direction in the recirculation region. As the fuel injection rate increased, the shear layer downstream of the vent slot mixer grew uniformly along the spanwise direction; consequently, shock structures such as a recompression shock and weak shocks on the shear layer were significantly mitigated at J = 3.2.     

Theoretically calculated rovibronic transition spectra of KRb

Spectroscopic properties of all the electronic states of KRb dissociating into 4s(K) + 5s(Rb), 4s(K) + 5p(Rb), 4p(K) + 5s(Rb), and 4s(K) + 4d(Rb) and some higher-lying excited states are studied with ab initio calculations. Spectroscopic constants, dipole moments, and the nature of the electronic wave functions for these states are reported. Intensities for the singlet-singlet and triplet-triplet transitions are theoretically calculated from the potential energy curves and the transition dipole moments. © 1996 John Wiley & Sons, Inc.     

Silver(I) ion selective ionophores containing dithiocarbamoyl moieties on steroid backbone

Tweezer-type and non-tweezer-type ionophores containing dithiocarbamoyl groups on a 7-deoxycholic amide or cholane derivatives were designed and synthesized. Potentiometric evaluation of the poly(vinyl chloride) (PVC) membranes containing those deoxycholic amides/cholanes linked with tweezer-type dithiocarbamoyl moieties showed excellent affinity and selectivity to silver(I) ion over alkali, alkaline earth and other transition metal cations. On the other hand, deoxycholic amides/cholanes substituted with one dithiocarbamoyl group, i.e., non-tweezer-type ionophores, resulted in relatively poor potentiometric sensitivity and detection limits. The enhanced potentiometric properties of newly synthesized tweezer-type dithiocarbamoyl containing ionophores have been further improved by employing silver ion complexing reagent in the internal reference solution, which resulted in greatly reduced detection limit (∼100 ppt) for the electrodes based on them.     

Direct transesterification of poly(methyl acrylate) for functional polyacrylate syntheses

Post‐polymerization modification is an important synthetic method to produce macromolecules with various chemical and physical properties. With this technique, functional groups of polymer molecules within the same structural scaffold can be varied, and thus, accurate research on structure‐property relationships is possible. To add practicality, the direct post‐polymerization of commodity polymers has been pursued, but only limited success has been realized. In this report, a study on various transesterification methods for the synthesis of functional polyacrylates beginning with a poly(methyl acrylate) (PMA), one common acrylate polymer, is presented. The Zn‐based catalytic system, a combination of Zn₄(OCOCF₃)₆O and 4‐dimethylaminopyridine with instant methanol removal, exhibited the highest reactivity among many catalysts and conditions. Assorted alcohols were reacted with PMA to produce the corresponding polyacrylates. This method was successfully extended to post‐polymerization modification of a PMA‐containing block copolymer, PS‐b‐PMA and synthesis of acrylate copolymers with functional group density control. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2554–2560     

The Na2 2 3pi(g) state: new observations and hyperfine structure

Many more Na2 2 3pi(g) v = 0-43, omega = 0, 1, 2 levels have been observed by sub-Doppler continuous wave perturbation facilitated optical-optical double resonance fluorescence excitation spectroscopy and the hyperfine structure of the omega = 0 and 2 levels has been resolved. New molecular constants for the less perturbed v = 0-43 levels have been obtained with these new and the previously reported data. The hyperfine coupling scheme of the observed 2 3pi(g) levels is close to Hund's case a(beta) with a Fermi contact constant b(F) = 160+/-5 MHz, which is smaller than the Fermi contact constants of other Na2 triplet Rydberg states, b(F) = 200-245 MHz.     

Facile fabrication of networked patterns and their superior application to realize the virus immobilized networked pattern circuit

A facile route to fabricate a protein-immobilized network pattern circuit for rapid and highly sensitive diagnosis was developed via the evaporation directed impromptu patterning method and selective avian influenza virus (AIV) immobilization. The response to the 10 fg mL(-1) anti-AI antibody demonstrates that this easy and simple circuit has about 1000 times higher sensitivity compared to those of conventional approaches.     

Microfluidics assisted synthesis of well-defined spherical polymeric microcapsules and their utilization as potential encapsulants

In this article, the development of a novel technique to fabricate spherical polymeric microcapsules by utilizing microfluidic technology is presented. Atom transfer radical polymerization (ATRP) was employed to synthesize well-defined amphiphilic block copolymers. An organic polymer solution was constrained to adopt the spherical droplets in a continuous water phase at a T-junction microchannel, and the generation of the droplets was studied quantitatively. The flow conditions of two immiscible solutions were adjusted for the successful generation of the polymer droplets. The morphology of the microcapsules was examined. The efficiency of these polymer microcapsules as containers for the storage and controlled release of loaded molecules was evaluated by encapsulating the microcapsules with Congo-red dye and investigating the release performance using temperature controlled UV-VIS spectroscopy.