Nuclear structure explored by β-delayed decay spectroscopy of spin-polarized radioactive nuclei at TRIUMF ISAC-1

Spin-polarized radioactive nuclear beams at TRIUMF enable a new spectroscopic method which efficiently assigns spins and parities of the daughter levels by taking advantage of the asymmetric β-decay of the polarized parent nucleus. This method was successfully applied to structure studies of ²⁹Mg and ³⁰Mg in connection with the physics of the “island of inversion”. In ²⁹Mg, two low-lying levels with intruder configuration were assigned. In ³⁰Mg, coexistence of spherical shape, prolate shape and γ-collectivity was strongly suggested.     

Macromolecular Recognition and Macroscopic Interactions by Cyclodextrins

Herein macromolecular recognition by cyclodextrins (CDs) is summarized. Recognition of macromolecules by CDs is classified as main‐chain recognition or side‐chain recognition. We found that CDs form inclusion complexes with various polymers with high selectivity. Polyrotaxanes in which many CDs are entrapped in a polymer chain were prepared. Tubular polymers were prepared from the polyrotaxanes. CDs were found to recognize side‐chains of polymers selectively. CD host polymers were found to form gels with guest polymers in water. These gels showed self‐healing properties. When azobenzene was used as a guest, the gel showed sol‐gel transition by photoirradiation. When ferrocene was used, redox‐responsive gels were obtained. Macroscopic self‐assembly through molecular recognition has been discovered. Photoswitchable gel association and dissociation have been observed.     

Enhanced Phosphorescence Emission by Incorporating Aromatic Halides into an Entangled Coordination Framework Based on Naphthalenediimide

Phosphorescence emission at room temperature is turned on in an entangled porous coordination polymer (PCP) with naphthalenediimide (NDI) as chromophore, by incorporating halogenated guests into the pores. The phosphorescent efficiency is drastically increased by the incorporation of aromatic halide guests in comparison with the incorporation of nonaromatic derivatives. Aromatic halide guests trigger a structural transformation, which allows a strong interaction with the NDI ligand in the framework through charge‐transfer complexation, and provides an extra population process of the triplet state. The long‐lived photoinduced triplet states, with an emission wavelength in the red region of the visible spectrum, demonstrated by this PCP, may open the door for potential uses, for example, as singlet‐oxygen generators or for bio‐imaging applications.     

Macroscopic observations of molecular recognition: discrimination of the substituted position on the naphthyl group by polyacrylamide gel modified with β-cyclodextrin

Macroscopic molecular recognition observations were realized using polyacrylamide-based gels modified with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), 1-naphthylmethyl (1Np), and 2-naphthylmethyl (2Np) moieties, which are denoted as αCD(x)-gel, βCD(x)-gel, 1Np(y)-gel, and 2Np(y)-gel, where x and y indicate the mol % of CD and Np moieties, respectively. The αCD(5)-gel did not adhere to either the 1Np(5)-gel or 2Np(5)-gel, whereas the βCD(5)-gel interacted with both to form alternating or checkered assemblies. Although the difference in the association constants of β-CD for the model polymers was small, the βCD(x)-gel successfully discriminated between 1Np(y)-gel and 2Np(y)-gel at the appropriate x and y.     

Creation of coating surfaces possessing superhydrophobic and superoleophobic characteristics with fluoroalkyl end-capped vinyltrimethoxysilane oligomeric nanocomposites having biphenylene segments

Fluoroalkyl end-capped vinyltrimethoxysilane oligomeric nanocomposites having biphenylene units [R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2)] were prepared by the sol-gel reaction of the corresponding oligomer [R(F)-(VM)(n)-R(F)] with 4,4'-bis(triethoxysilyl)-1,1'-biphenyl [Ar-Si(OEt)(3)] under alkaline conditions. R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2) nanocomposites were applied to the surface modification of PMMA to exhibit not only a good oleophobicity imparted by fluorine but also a fluorescent emission ability on the surface. Methanol sol solutions of R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2) nanocomposites were effective for the surface modification of glass through the dipping technique to exhibit good oleophobicity with superhydrophobicity on the modified glass surface. On the other hand, 1,2-dichloroethane sol solutions enabled R(F)-(VM-SiO(2))(n)-R(F)/Ar-SiO(2) nanocomposites to exhibit both superhydrophobic and superoleophobic characteristics on the modified surface through dipping the glass in these sol solutions.     

Mössbauer spectroscopic study of γ-ray irradiated potassium borate glasses

Potassium borate glasses denoted by the formula xK₂O · (100 ? x)B₂O₃ · 7Fe₂O₃ were irradiated with ⁶⁰Co-γ-rays at room temperature. Mössbauer parameters for the irradiated glasses containing alkali equal to or higher than 20 mole% showed that the s-electron density at the iron nucleus increased without any change of the steric configuration of oxygen atoms around the iron nucleus. The increase of s-electron density was ascribed to electron transfer from the nonbridging oxygen to the iron nucleus. The presence of the nonbridging oxygen was also confirmed by the irradiation effect of the borate glass (x = 30) prepared using the enriched isotope of ⁵⁷Fe₂O₃. Mössbauer parameters for the irradiated glass suggest that the newly observed Fe²⁺ ions are in tetrahedral symmetry.     

Uranium determination by133Xe in mineral separates from igneous rocks comparative study with fission track and thermal release characters of133Xe

Samples of an andesite (Asama-yama, Japan) and a basalt (Kilauea, Hawaii) were finely fractioned by density and the U distributions among the separates were determined by homogenized fission track method. Groundmass was found to be enriched with U; one half of the andesite U and almost all of the basalt U are accounted for by the groundmass U. Cerium and other REE are correlated with U. In the andesite separates Na is accompanied by these elements, but Fe and Co are rather anticorrelated. Uranium concentrations in the bulk samples and some of the separates were then compared with those determined by¹³³Xe extracted by heating at 1600°C. Fissiogenic¹³³Xe seems to become labile in groundmass, especially of the andesite, during reactor irradiations for 5 h or more. Stepwise heating experiments suggested that¹³³Xe in U-rich groundmass tends to escape at low temperatures and the remaining¹³³Xe is mostly retained in highly refractory sites in phenocryst rather poor in U.     

Maleimidophenyl isocyanates as postpolymerization modification agents and their applications in the synthesis of block copolymers

The maleimide structure is highly reactive, exemplified by thiol–ene click reactions with thiols and Diels–Alder reactions with furans. Although postpolymerization modifications and macromolecular conjugations involving maleimide units have been widely studied, mostly due to their selectivity and high reactivity, little has been reported on the one‐pot postpolymerization introduction of maleimides in polymer chains. Herein, we report p‐maleimidophenyl isocyanate and its derivatives as modification agents to introduce maleimide moieties by reaction with hydroxy groups into polymer chains. The high reactivity of the resulting modification agents and of the corresponding maleimide structures once inserted in the polymer chains was examined by studying their reaction kinetics. Furthermore, these modification agents were successfully applied to the synthesis of macromonomers for graft polymerization and various block copolymers, with, for example, AB‐type, star‐shaped, and H‐shaped architectures. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2396–2406     

Determination of chromium(vi) in natural waters by the sorption of chromium-diphenylcarbazone with xad-2 resin

The sorption of the chromium(III)-diphenylcarbazone complex (Cr-DPC) with XAD-2 has been investigated, for use in the separation of Cr(VI) from Cr(III) species in natural waters. Cr-DPC is formed from the reaction of Cr(VI) with diphenylcarbazide, but Cr(III) species give no reaction in aqueous solution. The addition of sodium chloride or sodium beta-naphthalenesulphonate markedly enhances the sorption. The Cr-DPC sorbed on XAD-2 can be almost completely eluted with organic solvents, especially methanol, but about 5% of it is irreversibly sorbed and cannot be eluted. The excess of diphenylcarbazide and some of the organic matter in natural waters are also sorbed on XAD-2 but most of this can also be eluted with methanol. Organic matter which interferes with measurement of the absorbance of Cr-DPC can almost all be removed by extraction with chloroform. By use of these techniques, Cr(VI) in sea-water has been determined by the standard-addition method. Although about 50 litres of sea-water are necessary for the analysis, organic and colloidal Cr(III) species do not interfere.     

The stability of the modified plane Poiseuille flow in the presence of a transverse magnetic field

The stability against small disturbances of the pressure-driven plane laminar motion of an electrically conducting fluid under a transverse magnetic field is investigated. Assuming that the outer regions adjacent to the fluid layer are electrically non-conducting and not ferromagnetic, the appropriate boundary conditions on the magnetic field perturbations are presented. The Chebyshev collocation method is adopted to obtain the eigenvalue equation, which is then solved numerically. The critical Reynolds number R_c, the critical wave number α_c, and the critical wave speed c_c are obtained for wide ranges of the magnetic Prandtl number P_m and the Hartmann number M. It is found that except for the case when P_m is sufficiently small, the magnetic field has both stabilizing and destabilizing effects on the fluid flow, and that for a fixed value of M the fluid flow becomes more unstable as P_m increases.