Reversible Pore Size Control of Elastic Microporous Material by Mechanical Force

Nanoporous materials, such as zeolites, activated carbons, and metal–organic frameworks (MOFs), are peculiar platforms in which a variety of guest molecules are stored, reacted, and/or separated. The size of the nanopores is essential to realize advanced functions. In this work, we demonstrate a very simple but innovative method for the control of nanopore size, that is, reversible and continuous control by mechanical force loaded to soft nanoporous materials. The elastic properties of several microporous materials, including zeolites, zeolite‐templated carbon (ZTC), activated carbon, and MOFs (e.g., ZIF‐8), are examined and it is found that ZTC is a material that is suitable for the aforementioned idea thanks to its extraordinary soft properties compared to the others. The original pore size of ZTC (1.2 nm) can be contracted to 0.85 nm by using a relatively weak loading force of 135 MPa, whereas the other microporous materials barely contracted. To demonstrate the change in the physical properties induced by such artificial deformation, in situ gas adsorption measurements were performed on ZTC with and without loading mechanical force, by using CO₂, CH₄, and H₂, as adsorbates. Upon the contraction by loading 69 or 135 MPa, CO₂ adsorption amount is increased, due to the deepening of the physisorption potential well inside the micropores, as proved by the increase of the heat of adsorption. Moreover, the adsorption amount is completely restored to the original one after releasing the mechanical force, indicating the fully reversible contraction/recovery of the ZTC framework against mechanical force. The experimental results are theoretically supported by a simulation using Grand Canonical Monte Carlo method. The similar adsorption enhancement is observed also on CH₄, whereas H₂ is found as an exception due to the weak interaction potential.     

Some characterizations of minimally thin sets in a cylinder and Beurling-Dahlberg-Sjögren type theorems

This paper shows that some characterizations of minimally thin sets connected with a domain having smooth boundary and a half-space in particular can also be given for a minimally thin set at infinity of a cylinder.

     

On Central Elements in the Universal Enveloping Algebras of the Orthogonal Lie Algebras

We present an analogy of the famous formula that the square of the Pfaffian is equal to the determinant for an alternating matrix for the case where the entries are the generators of the orthogonal Lie algebras. This identity clarifies the relation between the two sets of central elements in the enveloping algebra of the orthogonal Lie algebras. We employ systematically the exterior calculus for the proof.     

Contributions to multivariate analysis by Professor Yasunori Fujikoshi

The purpose of this article is to review the findings of Professor Fujikoshi which are primarily in multivariate analysis. He derived many asymptotic expansions for multivariate statistics which include MANOVA tests, dimensionality tests and latent roots under normality and nonnormality. He has made a large contribution in the study on theoretical accuracy for asymptotic expansions by deriving explicit error bounds. A large contribution has been also made in an important problem involving the selection of variables with introducing “no additional information hypotheses” in some multivariate models and the application of model selection criteria. Recently he is challenging to a high-dimensional statistical problem. He has been involved in other topics in multivariate analysis, such as power comparison of a class of tests, monotone transformations with improved approximations, etc.     

Reaction of α,β‐unsaturated ketones using cerium (IV) sulfate tetrahydrate in acetic acid

The reaction of α,β‐unsaturated ketones with cerium (IV) sulfate tetrahydrate [Ce(SO₄)₂·4H₂O, CS] in acetic acid gave the corresponding β‐acetoxy ketones. In the case of 2‐cyclohexen‐1‐one with CS in acetic acid, benzobicyclo[2.2.2]octen‐2‐one was obtained. The reaction mechanism also was proposed. Moreover, we report the aromatization and esterification of (R)‐(?)‐carvone by CS in acetic acid. Copyright © 2007 John Wiley & Sons, Ltd.     

Numerical investigation on propagation mechanism of spinning detonation in a circular tube

Spinning detonations propagating in a circular tube were numerically investigated with a one-step irreversible reaction model governed by Arrhenius kinetics. The time evolution of the simulation results was utilized to reveal the propagation mechanism of single-headed spinning detonation. The track angle of soot record on the tube wall was numerically reproduced with various levels of activation energy, and the simulated unique angle was the same as that of the previous reports. The maximum pressure histories of the shock front on the tube wall showed stable and unstable pitch modes for the lower and higher activation energies, respectively. The shock front shapes and the pressure profiles on the tube wall clarified the mechanisms of two modes. The maximum pressure history in the stable pitch remained nearly constant, and the single Mach leg existing on the shock front rotated at a constant speed. The high and low frequency pressure oscillations appeared in the unstable pitch due to the generation and decay of complex Mach interaction on the shock front shape. The high-frequency oscillation was self-induced because the intensity of the transverse wave was changed during propagation in one cycle. The high-frequency behavior was not always the same for each cycle, and therefore the low frequency oscillation was also induced in the pressure history.     

Charge‐mosaic membrane prepared from microspheres

A new type of charge‐mosaic membrane was prepared from poly(4‐vinyl pyridine) microspheres 250–350 nm in diameter as an anion‐exchange element and from linear poly(sodium styrene sulfonic acid) as a cation‐exchange element. The mosaic structure on the surface of the membrane and the continuous connection of the microspheres in the membrane were confirmed by scanning electron microscopy observations and the electrical conductivity of the membrane. The microspheres were continuously connected from one side to the other side of the membrane surface when the weight fraction of the microspheres increased more than 20–25 wt % in the membrane. The flux of KCl, the permeability coefficient of KCl, the volume flux, and the selectivity dialysis separation of the electrolyte (KCl) and nonelectrolyte (glucose and saccharose) of the membrane indicated that it had the characteristic properties of a charge‐mosaic membrane. Ion‐exchange membranes composed of each raw material of the charge‐mosaic membrane did not show these properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1251–1261, 2003