Magnetothermal force on heated or cooled pipe flow

The effects of the magnetothermal force on the flows of heat and fluid through a pipe are investigated numerically when the pipe wall is either heated or cooled at constant heat flux. The flow is laminar and a paramagnetic fluid is presumed as the working fluid. Because the magnetic susceptibility of a paramagnetic fluid depends on the inverse of its temperature, the magnetothermal force is induced by coupling of the temperature field and magnetic induction. First, the effects are discussed using the case of a magnetic field induced by a single-turn concentrically placed electric coil. It is found that the effects of the magnetothermal force differ according to whether the pipe is cooled or heated. When cooled, the heat and fluid flows are affected behind the coil; the flow is repelled from the wall to the center and the thermal boundary layer thickens. By decomposing the force into the radial and axial directions in the heated and cooled cases, it is clarified that the axial force changes from positive to negative depending on the coil location in the heated case. Therefore, it can be concluded that the effects are not simply oppositional in the heated and cooled cases. In relation to the heat transfer, only when the coil is placed at the threshold of the heating/cooling zone do the effects on the local heat transfer become the opposite of each other. At other coil locations, the suppression of heat transfer is dominant ahead of the coil in the heated case, as indicated in previous work by our group. However, in the cooled case, this effect occurs behind the coil. For a more practical case, a solenoid coil is employed in the simulation. It is then found that the effect on the heat transfer becomes remarkable at the solenoid edges, especially for the heat-transfer suppression in both the heated and cooled cases.     

Wave turbulence and intermittency in directional wave fields

The evolution of surface gravity waves is driven by nonlinear interactions that trigger an energy cascade similarly to the one observed in hydrodynamic turbulence. This process, known as wave turbulence, has been found to display anomalous scaling with deviation from classical turbulent predictions due to the emergence of coherent and intermittent structures on the water surface. In the ocean, waves are spread over a wide range of directions, with a consequent attenuation of the nonlinear properties. A laboratory experiment in a large wave facility is presented to discuss the sensitivity of wave turbulence on the directional properties of model wave spectra. Results show that the occurrence of coherent and intermittent structures become less likely with the broadening of the wave directional spreading. There is no evidence, however, that intermittency completely vanishes.     

Single Crystal to Single Crystal (SC‐to‐SC) Transformation from a Nonporous to Porous Metal–Organic Framework and Its Application Potential in Gas Adsorption and Suzuki Coupling Reaction through Postmodification

A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH₂ groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m² g^?1. The material also possesses good CO₂ (8 wt %) and H₂ (1.87 wt %) adsorption capabilities.     

Control over Nanostructures and Associated Mesomorphic Properties of Doped Self‐Assembled Triarylamine Liquid Crystals

We have synthesized a series of triarylamine‐cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by ¹H NMR and UV/Vis spectroscopy that their supramolecular self‐assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable‐temperature polarizing optical microscopy (VT‐POM), variable‐temperature X‐ray diffraction (VT‐XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar‐ or columnar‐packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self‐assemblies as electroactive materials from solution to mesophases.     

Improvement in flow-sheet of extraction chromatography for trivalent minor actinides recovery

Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate...