Spin selectivity in the oxygenation of singlet phenylhalocarbenes with oxygen

Singlet phenylhalocarbenes are shown to react with triplet oxygen and the apparent spin-forbidden oxygenation rates are strongly dependent on substituents, i.e. in the decreasing order of Br>Cl?F for halogen and of p-NO₂>H?p-MeO for p-substituents. These results suggest the oxygenation of triplet halocarbene equilibrated with ground-state singlet, resulting in the first estimation of energy difference between the singlet and triplet states.     

Copper(II)-cetyltrimethylammonium chloride-chromal blue G ternary complex and its application to the spectrophotometric determination of copper(II)

A sensitive spectrophotometric method for the determination of copper(II) based on a ternary complex with chromal blue G, a triphenylmethane reagent in the presence of cetyltrimethylammonium chloride, is described. The sensitivity of color reaction between copper and chromal blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride, a cationic surfactant. The color development of the ternary complex can be utilized in the highly sensitive spectrophotometric determination of copper. The molar absorptivity of the binary complex between copper and chromal blue G ε_630nm = 9.56 × 10³liters · mol⁻¹ · cm⁻¹ is enchanced on ternary complex formation to ε_{542 nm} = 4.78 × 10⁴liters · mol⁻¹ · cm⁻¹. The ternary complex gave a maximal absorbance at 542 nm in the pH range 9.8–11. Beer's law is obeyed up to at least 1.2 ppm of copper. The maximal absorbance of the ternary complex was found to develop within 5 min and then it remains constant for several hours. The formation constant of the ternary complex is calculated to be 8.6 × 10¹⁰ under these conditions.     

Y-ligation: An efficient method for ligating single-stranded DNAs and RNAs with T4 RNA ligase

Very efficient ligation ofoligodeoxyribonucleotides was attained through asimple molecular construct, which is composed of onestem and two branches (Y-shape), with use of T4 RNAligase. Single-stranded DNAs (naturally, RNAs also) ofmore than 100 nucleotides (even 800 nts) wereconsiderably ligated, approximately as theoreticallyexpected. Owing to the molecular construct adopted,such a tiny amount of ligation products could beamplified to a sufficient amount by PCR and thenrecovered as single-stranded DNAs. This advantage ofbeing amplifiable is shown to be useful for bothcombinatorial chemistry and evolutionary molecularengineering, which deal with a pool of diversity molecules.     

Selective Ion Exchange in Supramolecular Channels in the Crystalline State

Artificial ion channels are of increasing interest because of potential applications in biomimetics, for example, for realizing selective ion permeability through the transport and/or exchange of selected ions. However, selective ion transport and/or exchange in the crystalline state is rare, and to the best of our knowledge, such a process has not been successfully combined with changes in the physical properties of a material. Herein, by soaking single crystals of Li₂([18]crown‐6)₃[Ni(dmit)₂]₂(H₂O)₄ ( 1 ) in an aqueous solution containing K⁺, we succeeded in complete ion exchange of the Li⁺ ions in 1 with K⁺ ions in the solution, while maintaining the crystalline state of the material. This ion exchange with K⁺ was selectively conducted even in mixed solutions containing K⁺ as well as Na⁺/Li⁺. Furthermore, remarkable changes in the physical properties of 1 resulted from the ion exchange. Our finding enables not only the realization of selective ion permeability but also the development of highly sensitive biosensors and futuristic ion exchange agents, for example.     

Experimental investigation of water laminar mixed-convection flow with sub-millimeter bubbles in a vertical channel

This paper describes flow and heat transfer characteristics of laminar mixed-convection flows of water with sub-millimeter bubbles in a vertical channel. We use thermocouples and a particle tracking velocimetry technique for the temperature and velocity measurements. The working fluid used is tap water, and hydrogen bubbles generated by electrolysis of the water are used as the sub-millimeter bubbles. The Reynolds number of the main flow ranges from 100 to 200. The ratio of the heat transfer coefficient with sub-millimeter-bubble injection to that without injection (the heat transfer coefficient ratio) ranges from 1.24 to 1.38. The heat transfer coefficient ratio decreases with the increase in the Reynolds number. We conclude from velocity measurements that this decrease is mainly caused by a decrease in the advection effect due to sub-millimeter bubbles.     

Visualization of flow and vortex structure around a swimming loach by dynamic stereoscopic PIV

Loach has a unique swimming style of bending the whole body and staying at the bottom of water. We studied the three-dimensional flow field around and behind the loach using stereoscopic-PIV. We captured flow fields in horizontal and vertical plane, and it seems loach leaves vortex tube arches. From the analysis of body motion and flow field, we propose flow structure with vortex tube arches connected along the loach body. After being released, they are separated and flow away and dissipate. This research article was submitted for the special issue on Animal locomotion: The hydrodynamics of swimming (Vol. 43, No. 5).