A Coloring Problem With Restrictions of Adjacent Colors

The coloring problem is a well-known problem of graphs. This paper considers a new coloring problem with restrictions such that some pairs of colors cannot be used for adjacent vertices, called coloring problem with restrictions of adjacent colors . The restriction of adjacent colors can be represented by a graph H called a restriction graph , i.e., each vertex represents a color and each edge means that the two colors corresponding to the two end-vertices of the edge cannot be used for adjacent vertices. This paper shows some properties of the new coloring problem. It also presents a necessary and sufficient condition such that a restriction graph H cannot be replaced with a more simple graph, when H is a cactus with no 3-cycle.     

Synthesis of polymers bearing azo-dye chromophore with photocrosslinkable moiety for nonlinear optics

Summary Novel photocrosslinkable second-order nonlinear optical(NLO) polymers were synthesized from radical homopolymerization of 4-[N-ethyl-N-(2-methacryloyloxyethyl)]amino-4-(2-cinnamoyloxyethyloxycarbonyl)-2-nitroazobenzene(MACN) or copolymerization of MACN with 2-(cinnamoxyloxy)ethyl methacrylate(CM), and from polycondensation of 4-[N,N-bis(2-hydroxyethyl)]amino-4-(2-cinnamoyloxyethyloxycarbonyl)-2-nitroazobenzene(HACN) with p-phenylenediacyloyl chloride(PD). For the purpose of obtaining an optimized condition of UV irradiation for poling treatment involving photocrosslinking, photoreactivity of these NLO polymer films was investigated. There was observed considerably different photoreaction behavior, especially in photofading of the NLO chromophore, between MACN polymer and HACNPD polycondensate; the latter faded more rapidly than the former. A reason for this phenomenon was considered.     

A novel series of quinoline containing asymmetrically substituted polydiacetylenes for third-order nonlinear optical material

Summary A series of novel unsymmetrical diacetylenes have been prepared which have quinolyl moiety as one of the directly linked sidegroups to the acetylenic backbone. One of the diacetylenes exists in two crystal forms, one of which is solid state reactive. The polydiacetylenes obtained from the monomers have generally long effective conjugation length as indicated by their absorption spectra. The third-order nonlinear optical susceptibility (χ⁽³⁾) of one of the polydiacetylenes has been evaluated and found to be in the order of 10⁻¹¹ esu. Received: 17 June 1998/Revised version: 24 August 1998/Accepted: 27 August 1998     

Proposal of new gene filtering method, BagPART, for gene expression analysis with small sample

A significant problem in gene expression analysis is that the sample size is substantially lower than the number of genes. Bagging is an effective method of solving this problem in the case of small sample datasets. We have devised a combination method, called the BagPART filtering method, that uses the projective adaptive resonance theory (PART) to select important genes and achieve a binary classification more accurately (p<10(-10)) than conventional methods, particularly when the sample size is small.     

Thermal stability of embedded metal nanoparticles elongated by swift heavy ion irradiation: Zn nanoparticles in a molten state but preserving elongated shapes

Solid Zn and V nanoparticles (NPs) embedded in silica were elongated by swift heavy ion (SHI) irradiation with 200 MeV Xe(14+) ions to a fluence of 5.0 × 10(13) ions cm(-2). Isochronal annealing was carried out in a vacuum from 200 to 1000 °C in steps of 100 °C for 10 min each. The degree of shape elongation was evaluated at room temperature (RT) by two different optical methods: linear dichroism spectroscopy and birefringence spectroscopy. In the as-irradiated state, the samples showed an absorption band at 5 eV due to radiation-induced defects in the silica in addition to the anisotropic absorption due to the elongated metal NPs. After annealing at 400 °C the defect band had completely disappeared, while the degree of shape elongation was almost unchanged or rather slightly increased in both the Zn and V NPs. The elongation of the Zn NPs slightly decreased but maintained a certain value after annealing at 500 °C, which is much higher than the melting point (MP) of Zn NPs (~420 °C). This observation indicates that shape elongation is mostly maintained even if the Zn NPs are in the molten state to some extent during annealing. The elongation of the Zn NPs was almost eliminated after annealing at 600 °C. In the case of the V NPs, elongation was maintained up to 800 °C but mostly eliminated at 900 °C. Since the recovery temperature of 900 °C from the elongated to the spherical shape is much lower than the MP of bulk V (1890 °C), we consider that the elongation is eliminated without melting of V NPs, i.e. via solid state mass transportation. The melting of NPs is not the key factor for the recovery to the spherical shape.     

Electron‐beam‐induced discharge phenomena of teflon films for space use

We investigated the discharge phenomena of Teflon FEP (fluorinated ethylene propylene) films used as thermal control material of spacecraft by electron‐beam irradiation simulating hot plasma in space. FEP films of two thicknesses, 25 and 127 μm, were tested. The results obtained were as follows.

• (1) In 127‐μm‐thick FEP film, a surface discharge triggered by high electric field at the triple junction of the edge of the metal frame occurred.
• (2) In 25‐μm‐thick FEP film, punchthrough discharge accompanied by surface flashover occurred.
• (3) Discharge frequency increased as nearly the 1/2 power of the electron‐beam current density under constant irradiation energy. On the other hand, it increased linearly with the irradiation energy under constant beam current density, but with sufficient threshold electron energy to cause discharge.

These results were explained by comparison between the surface electric field and the bulk electric field in FEP film obtained analytically by using a two‐dimensional charging model. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 10–19, 1999