Sequential Chiral Induction and Regulator-Assisted Chiral Memory of Pillar[5]arenes

Chirality transfer is widely observed in life processes, and many artificial chiral transfer systems have been developed. In these systems, chiral information is transferred from chiral inducers to chiral acceptors by a direct chiral induction process and a direct chiral memorization process. We have developed ternary nondirect chiral transfer systems based on pillar[5]arenes, in which a third factor was introduced as a regulator. The planar chirality of an acceptor was induced and memorized by a chiral inducer with precise control by a regulator. In the chiral induction period, the feed sequence of the chiral inducer and regulator affected the chiral induction behavior of the chiral acceptor. The chiral memory ability of the acceptor was substantially improved by the combined action of the chiral inducer and regulator.     

Energy gap of spin nanotube

Recently some quantum spin systems on tube lattices, so-called spin nanotubes, have been synthesized. They are expected to be interesting low-dimensional systems like the carbon nanotubes. As a first step of theoretical study on the spin nanotube, we investigate the three-leg spin tube, which is the simplest one, using numerical analyses of finite clusters and a finite-size scaling technique. The spin gap, which is one of the most interesting quantities reflecting the macroscopic quantum effect, was revealed to be open for any finite rung exchange couplings, in contrast to the three-leg spin ladder system which is gapless. We also found a quantum phase transition caused by an asymmetric rung interaction. When one of the three rung coupling constants is changed, the spin gap vanishes very rapidly.     

Genetic algorithms applied to neutron penumbral imaging

Penumbral imaging is a technique for imaging of neutrons or other penetrating radiations. The technique uses the fact that spatial information can be recovered from the shadow or penumbra that an unknown source casts of a simple large circular aperture. The limitation is that the straightforward image reconstruction will introduce some significant distortion for a large field of view because of non-isoplanaticity of the aperture point spread function. In this paper, a genetic algorithm (GA) is proposed for reconstruction of penumbral images and the technique allows distortion-free reconstruction over a large field of view. Furthermore, because in GA the complicateda priori constraints can be easily incorporated by appropriate modification of the cost function, the algorithm is also very tolerant of the noise.     

Strong photoluminescence and laser operation of InAs quantum dots covered by a GaAsSb strain-reducing layer

GaAsSb strain-reducing layers (SRLs) are applied to cover InAs quantum dots (QDs) grown on GaAs substrates. The compressive strain induced in InAs QDs is reduced due to the tensile strain induced by the GaAsSb SRL, resulting in a redshift of photoluminescence (PL) peaks of the InAs QDs. A strong PL signal around a wavelength of 1.3 μm was observed even at room temperature. A laser diode containing InAs QDs with GaAsSb SRLs in the active region was fabricated, which exhibits laser oscillation in pulsed operation at room temperature. These results indicate that GaAsSb SRLs have a high potential for fabricating high efficient InAs QDs laser diodes operating at long-wavelength regimes.     

On the Inozemtsev Model

The BC _N Inozemtsev model is investigated. Finite-dimensional spaces which are invariant under the action of the Hamiltonian of the BC _N Inozemtsev model are introduced and it is shown that commuting operators of conserved quantities also preserve the finite-dimensional spaces. The BC ₂ Inozemtsev model is studied in more detail.     

Dot character display using a negative-film diffraction grating matrix

A diffraction grating matrix made of negative film is applied to display dot characters. Using an X-Y plotter of a personal computer, a multiple grating pattern is plotted in a matrix form. The photograph of the pattern is the negative-film diffraction grating matrix. When a laser light illuminates the grating matrix, the diffracted light displays a dot character. Several alphabetic characters are displayed in this way.     

Highly Sensitive and Robust Linear Probe for Detection of mRNA in Cells

A stemless linear probe was designed that robustly detects mRNA in cells with high sensitivity. The probe is modified at some positions with base surrogates prepared from D ‐threoninol, with anthraquinone moieties near the 5′‐ and 3′‐termini, and with perylene moieties. Even in cell lysate that involves various proteins and enzymes, background emission was very low. When the probe was hybridized with RNA, chromophores are intercalated between the base pairs, resulting in a remarkable light‐up signal. The signal‐to‐background ratio was as high as 1600 under our standard buffer conditions. In the HeLa cell lysate, the linear probe had sufficient signal‐to‐background ratio (S/B=40) for reliable mRNA detection. No degradation was observed after a 24 h incubation in HeLa cell lysate. In cells, a probe designed to target DsRed resulted in distinct blue fluorescence only in cells transfected with plasmid encoding DsRed; no fluorescence was observed in control cells.     

Cationic polymerization of seven‐membered cyclic monothiocarbonate 1,3‐dioxepan‐2‐thione

The cationic ring‐opening polymerization of a seven‐membered cyclic monothiocarbonate, 1,3‐dioxepan‐2‐thione, produced a soluble polymer through the selective isomerization of thiocarbonyl to a carbonyl group {? [SC(C?O)O(CH₂)₄]_n? }. The molecular weights of the polymer could be controlled by the feed ratio of the monomer to the initiators or the conversion of the monomer during the polymerization, although some termination reactions occurred after the complete consumption of the monomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1014–1018, 2005     

Ethylene and 1‐hexene copolymerization with CO‐prereduced phillips CrOx/SiO2 catalyst in the presence of Al–alkyl cocatalyst

Phillips catalyst has been contributing to about 40% of world high‐density polyethylene production because of its ability to give products with unique microstructures like broad molecular weight distribution as well as short and long chain branches. Even after 50 years' effort, some crucial problems concerning the nature of active sites, polymerization, and branching mechanisms are still kept mysterious. In this work, ethylene and 1‐hexene copolymerization with Phillips catalyst prereduced by CO was carried out in the presence of triethyl aluminum (TEA) cocatalyst. The microstructures of polymers were investigated by ¹³C NMR and gel permeation chromatography (GPC) methods. A hybrid‐type kinetics was found for both homo‐ and copolymerization kinetics, which indicated that there existed two types of active sites namely site A and site B. Site A with instant activation, high activity, and fast decay was transformed from a metathesis site, namely Cr(II) site, coordinated with CO or CO₂ through desorption of CO or CO₂ by TEA, which contributed to the formation of short chain branches, especially methyl branches. Site B with slow activation, low activity, and slow decay was generated from reduction of residual chromate (VI) by TEA. Both 1‐hexene and TEA can decrease the molecular weight of polyethylene as well as enhance short chain branching. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4632–4641, 2005