Synthesis of graft copolymer from copolymerization of styrene‐terminated poly(ethylene oxide) macromonomer and styrene with CpTiCl3/methylaluminoxane catalyst

Copolymerization of styrene (St) and St‐terminated poly(ethylene oxide) macromonomer (SEOM) with CpTiCl₃/methylaluminoxane (MAO) catalyst in toluene was investigated. The copolymerization of St and SEOM proceeded easily to give a graft copolymer consisting of syndiotactic polystyrene as the main chain and hydrophilic poly(ethylene oxide) as the side chain. A number of side chains in the graft copolymer could be controlled by the amount of SEOM in the feed. The reactivity of SEOM was determined from copolymerization of St and SEOM with the CpTiCl₃/MAO catalyst, and the reactivity of SEOM depended on the molecular weight of SEOM. The thermal properties of the graft copolymer such as the melting temperature were influenced by the introduction of SEOM. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2904–2910, 2004     

Spin structure of the nucleon

Based on an infinite sublayer quark model, we determine the fraction of nucleon spin carried by subquarks.     

Dark Matter Candidate Particles, CP Violation and Higgs Bosons

In a previous paper, we proposed the infinite sub-layer quark model, in which the proton and the neutron are made up of an infinite number of point-like (structure-less) quarks u _∞ and anti-quarks u _∞ ^CP at an infinite sub-layer level. In this paper, we propose that the dark matter is also made of an infinite number of quarks u _∞ and anti-quarks u _∞ ^CP . A pair of the ultimate quarks u _∞ and anti-quarks u _∞ ^CP would be produced in the first moments after the Big Bang and then remain as the dark matter for all time, stable against decay and subject only to the weak interaction and gravity. It is then shown that CP is violated in the doublet of u _∞ and u _∞ ^CP quarks to account for the asymmetry of the number of particles and anti-particles in the present universe. Furthermore, it is shown that the Higgs bosons are composed of u _∞ and u _∞ ^CP dark matter particles and give the masses to gauge bosons, quarks and leptons.     

In-process monitoring and control of doping gas concentration during vapor phase silicon epitaxial growth by using a flame photometric detector

An in-process monitoring and control method of the doping gas concentration during epitaxial growth of Si was developed. A flame photometric detector (FPD) can be used as a monitor for the PH₃ and B₂H₆ dopant concentrations in the injected doping gases. A combination of this dopant monitor with an automatic control system of the silicon source (SiHCl₃) gas concentration using an infrared spectrophotometer as a monitor, makes possible an automatic in-process control of the concentrations of dopant and of silicon source gas supplied to the reactor. The present system provides an accurate and reproducible control of impurity concentrations in Si epitaxial layers. Good correlation between the monitored signal (or the doping gas concentration) and the impurity concentration incorporated into the growth layers was confirmed for PH₃ (n-type) and B₂H₆ (p-type) doping. For the B₂H₆ doping, a divergence from the linear relationship between the doping gas concentration and the impurity concentration in the layers was observed in the level of acceptor concentration below about 10¹⁵ atoms/cm³. The transient response of the present system was measured by growing epitaxial layers with increasing and decreasing step-changes in the dopant gas flow during continuous deposition of the layers. Some interesting, but complicated, transient responses of impurity concentration in the growth layer were observed. The responses are different between the PH₃ doping and the B₂H₆ doping, and also different between increasing and decreasing steps especially for the B₂H₆ doping.     

Two-dimensional DNA origami assemblies using a four-way connector

Two-dimensional self-assembly of DNA origami structures was carried out using a connector that has connection sites at all four edges. By utilizing this four-way connector, five and eight origami monomers were assembled to form a cruciate and a hollow square structure, respectively.     

Two new steroid glycosides and a new sesquiterpenoid glycoside from the underground parts of Trillium kamtschaticum

Two new steroid glycosides, named trikamsterosides A and B, and a new sesquiterpenoid glycoside named trikamsesuquiside A were isolated from the underground parts of Trillium kamtschaticum PALL. along with 18 known compounds comprising 12 steroids, one sesquiterpenoid glycoside, one phenylpropanoid, one flavonoid glycoside, and three phenylpropanoid sucrose esters. Their chemical structures were determined on the basis of spectroscopic data and chemical evidence. Among them, one phenylpropanoid sucrose ester showed almost the same radical-scavenging effect on 1,1-diphenyl-2-picrylhydrazyl as that of alpha-tocopherol.     

Programmed‐Assembly System Using DNA Jigsaw Pieces

A novel method for assembling multiple DNA origami structures has been developed by using designed 2D DNA origami rectangles, so‐called “DNA jigsaw pieces” that have sequence‐programmed connectors. Shape and sequence complementarity were introduced to the concavity and convex connectors in the DNA rectangles for selective connection with the help of nonselective π‐stacking interactions between the side edges of the DNA jigsaw piece structures. Single DNA jigsaw piece units were assembled into unidirectional nanostructures with the correct alignment and uniform orientation. Three and five different DNA jigsaw pieces were assembled into predesigned and ordered nanostructures in a programmed fashion. Finally, three‐, four‐, and five‐letter words have been displayed by using this programmed DNA jigsaw piece system.     

Total synthesis of apoptolidin: construction of enantiomerically pure fragments

A general strategy for the total synthesis of the antitumor agent apoptolidin (1) is proposed, and the chemical synthesis of the defined key building blocks (4, 5, 6, 8, and 9) in their enantiomerically pure forms is described. The projected total synthesis calls for a dithiane coupling reaction to construct the C(20)-C(21) bond, a Stille coupling reaction to form the C(11)-C(12) bond, and a Yamaguchi macrolactonization to assemble the macrolide ring, as well as two glycosidation reactions to fuse the carbohydrate units onto the molecule. First and second generation syntheses to the required fragments for apoptolidin (1) are described.