Synthesis,hydrophilicity, and oxygen permeability of poly[(trimethylsilyl)propyne]-gr-poly(N,N-dimethylacrylamide)

N,N-dimethylacrylamide (DMAA) was graft copolymerized on poly[(trimethylsilyl)propyne] (PTMSP) by single electron reduction of PTMSP with potassium naphthalenide (K-Naph), followed by anion polymerization of DMAA from the carbanion formed in the reduction. A hard and practically non-water-swelling PTMSP-gr-poly(DMAA) was obtained under the conditions using controlled amount of K-Naph and DMAA. The graft copolymer was characterized with regard to structure, number-averaged molecular weight, and the amount of grafting poly(DMAA) determined by the relative absorbance of the IR absorption band assigned to the CO and SiC H functionalities (A_CO/A_{SiC H}). The oxygen permeability and water contact angle (θ) of the graft copolymer were evaluated while varying the amount of grafting poly(DMAA). The graft copolymer proved to be highly oxygen permeable (165 Barrers) and hydrophilic (θ = 27°). Its transparency was also elucidated with UV–vis spectra. This graft copolymer was proposed as a promising candidate for use as a hard contact lens material. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 603–610, 1998     

Formation of Giant Liposomes from Crystalline Complexes of Monoalkylammonium Surfactants and 4-Hydroxybiphenyl

A parallel rather than a perpendicular alignment of aromatic compounds with respect to surfactant molecules (see schematic representation) is preferred for the formation of a liposome structure, because the perpendicular alignment would reduce the hydrophilicity of the aggregate. This is the result of studies on crystalline complexes of monoalkylammonium halides and various aromatic compounds.     

SugarDrawer: A Web-Based Database Search Tool with Editing Glycan Structures

In life science fields, database integration is progressing and contributing to collaboration between different research fields, including the glycosciences. The integration of glycan databases has greatly progressed collaboration worldwide with the development of the international glycan structure repository, GlyTouCan. This trend has increased the need for a tool by which researchers in various fields can easily search glycan structures from integrated databases. We have developed a web-based glycan structure search tool, SugarDrawer, which supports the depiction of glycans including ambiguity, such as glycan fragments which contain underdetermined linkages, and a database search for glycans drawn on the canvas. This tool provides an easy editing feature for various glycan structures in just a few steps using template structures and pop-up windows which allow users to select specific information for each structure element. This tool has a unique feature for selecting possible attachment sites, which is defined in the Symbol Nomenclature for Glycans (SNFG). In addition, this tool can input and output glycans in WURCS and GlycoCT formats, which are the most commonly-used text formats for glycan structures.     

Synthesis of polymers in aqueous solutions: Esterification reaction of poly(methacrylic acid) with alkyl halides using DBU in aqueous solutions

A convenient esterification reaction of poly(methacrylic acid) (PMAA) with certain alkyl halides was performed using 1,8-diazabicyclo-[5.4.0]-7-undecene (DBU) as a base in aqueous solution or in water. The esterification reaction of PMAA with propargyl bromide (PB) proceeded very smoothly and quantitatively at 30°C to give corresponding poly(propargyl methacrylate), although the rate of the reaction decreased with increasing water. The reaction of PMAA with benzyl bromide, o-nitrobenzyl bromide, and p-nitrobenzyl bromide gave corresponding poly(methacrylic ester) using DBU under suitable reaction conditions in water. The esterification reactions of PMAA with PB were carried out using certain organic bases such as triethylamine, 4(N,N-dimethylamino)pyridine and pyridine. Inorganic bases such as sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide were also tried under the same conditions as with DBU. However, the degrees of estrification with all these bases was much lower than that with DBU. © 1996 John Wiley & Sons, Inc.     

Growth of bubble-free Ti-doped Al2O3 single crystal by the czochralski method

The behaviour of bubble entrapment in Ti-doped Al₂O₃ single crystals grown by the Czochralski method was studied from the view point of crystal growth conditions such as the crystal rotation rate and kinds of growth atmosphere. The entrapment of bubbles was not correlated with the shape of solid-liquid interface dependent on crystal rotation rate. We found that the use fo He atmosphere, instead of the conventional atmosphere such as Ar, suppresses the formation of bubbles.     

Crown ether strategy toward chemical activation of biological protein functions

The chemical activation of biological proteins is outlined, in which small molecules are used to alter the chemical and physical properties of biological proteins through direct or indirect interactions. Crown ethers have the potential to modulate the protein functions by supramolecular complexations, because they bind alkylammonium and other ionic residues of the proteins as well as ionic components in their systems. Two interesting examples are described in which crown ether derivatives improved the protein functions: (1) enhancement of reactivity and enantioselectivity in lipase‐catalyzed asymmetric reactions; and (2) generation of catalytic activity in the oxidation with cytochrome c. This chemical activation based on crown ether chemistry can be viewed as a complementary method to biological mutation in modifying the biological protein functions.     

An Outer Approximation Algorithm Guaranteeing Feasibility of Solutions and Approximate Accuracy of Optimality

We treat a concave programming problem with a compact convex feasible set. Assuming the differentiability of the convex functions which define the feasible set, we propose two solution methods. Those methods utilize the convexity of the feasible set and the property of the normal cone to the feasible set at each point over the boundary. Based on the proposed two methods, we propose a solution algorithm. This algorithm takes advantages over classical methods: (1) the obtained approximate solution is always feasible, (2) the error of such approximate value can be evaluated properly for the optimal value of such problem, (3) the algorithm does not have any redundant iterations.     

Growth of LiNbO3 epitaxial films by oxygen radical-assisted laser molecular beam epitaxy

LiNbO₃ films were epitaxially grown on c-sapphire substrates using oxygen radical-assisted laser molecular beam epitaxy (MBE). X-ray diffraction-based structural analysis showed that the films were epitaxial. Triple-axis rocking curve measurements of the LiNbO₃ (0 0 0 6) reflection revealed that the film was highly c-oriented with an extremely narrow mosaic; the full width at half maximum of the LiNbO₃ (0 0 0 6) rocking curve was 0.0036°, comparable to the value of high-quality bulk crystals. The surface of the film was very smooth, with a surface roughness r.m.s. value, measured by atomic force microscope, of 0.4 nm for a film of thickness 15 nm. The chemical composition of the film measured by X-ray photoelectron spectroscopy (XPS) was stoichiometric within the accuracy of XPS measurement.     

Low temperature thermodynamical properties of the organic chain conductor (TMTSF)AsF

We report on specific heat measurements of the quasi-one-dimensional organic salt (TMTSF)₂AsF₆ in its spin density wave state between 75 mK and 7 K. Similarly to (TMTSF)₂PF₆, we find discontinuities in the lattice contribution at 1.9 K an d 3.5 K ascribed to sub-spin density wave phases. Time-dependent effects due to dynamics of low-energy excitations in metastable states occur only below 0.2 K which yields an activation energy for the equilibrium energy relaxation process of 0.34 K, 4-5 times smaller than found for (TMTSF)₂PF₆. Finally the reduction of the low-energy excitations contribution to the specific heat in comparison to PF₆ reveals an intermediate cubic-like regime between 0.25 and 0.5 K that we tentatively describe as the phason contribution of the incommensurate spin density wave modulation. Received: 17 March 1998 / Revised: 27 July 1998 / Accepted: 22 September 1998     

A Complete Frequency-Field Chart for the Antiferromagnetic Resonance in MnF2

Antiferromagnetic resonance (AFMR) measurements on a well characterized single crystal sample of MnF₂ have been performed using various kinds of millimeter and submillimeter sources up to 570 GHz and a superconducting magnet up to 20 T. All the AFMR modes predicted from the theory have been observed. We report a complete frequency-field chart for these AFMR modes.