Hydration and dehydration behavior of <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide gel particles

Thermal response of N-isopropylacrylamide (NiPAM) gel particles of submicron size was investigated by means of ultrasonic velocity and density focusing on the hydration and dehydration behavior. Hydration number, defined as the number of water molecules bound to one NiPAM monomer unit, was quantitatively evaluated in the course of the volume phase transition. Hydration numbers at low and high temperatures were about 7.5 (20 °C) and 3 (40 °C), respectively. Hydration number decreases markedly near the volume phase transition temperature, and the decrease is responsible to the formation of hydrophobic bonding and dehydration. The hydration number is independent both of the size and the composition of gel particles in the shrunken state, although there exists a composition dependence in the swollen state. It was also found that the self-assemblies formed by hydrophobic interaction are more bulky compared to those in the hydrated state.     

Bridging rate coding and temporal spike coding by effect of noise

It is controversial whether temporal spike coding or rate coding is dominant in the information processing of the brain. We show by a two-layered neural network model with noise that, when noise is small, cortical neurons fire synchronously and intervals of synchronous firing robustly encode the signal information, but that the neurons desynchronize with moderately strong noise to encode waveforms of the signal more accurately. Further increase of noise just deteriorates the encoding. A positive role of noise in the brain is suggested in a meaning different from stochastic resonance, coherence resonance, and deterministic chaos.     

A chromophore-labeled poly(N-propargylamide): a new strategy for a stimuli-responsive conjugated polymer

A new stimuli-responsive conjugated polymer was synthesized, where, following the change of secondary conformation from helical to disordered state, the fluorescence property of the side chain chromophore changes upon sensing external stimuli.     

Photo-initiated bromination of octakis(1,1,2-trimethylpropyl)octasila- cubane with tetrabromomethane

Bromination reactions of octasilacubane via radical intermediates are demonstrated. In the absence of oxygen, UV-light irradiation of octakis(1,1,2-trimethylpropyl)octasilacubane (1) with tetrabromomethane in benzene resulted in the formation of only exo,exo-4,8-dibromoctakis(1,1,2-trimethylpropyl)tetracyclo[3.3.0.0^2,7.0^3,6]octasilane(2). However, in the presence of oxygen, the reaction of 1 with tetrabromomethane took place without irradiation, producing 2 and a novel type of the monooxidation product, dibromooxahomosecocubane (3). For the formation of these products, an electron-transfer mechanism involving successive cleavage of the Si–Si bonds, followed by skeletal rearrangement is proposed.     

Cohomology of open torus manifolds

The notion of an open torus manifold is introduced. A compact open torus manifold is a torus manifold introduced earlier. It is shown that the equivariant cohomology ring of an open torus manifold M is the face ring of a simplicial poset when every face of the orbit space Q is acyclic. This result extends an earlier result by Masuda and Panov, and the proof here is more direct. Reisner’s theorem is then applied to our setting, and a necessary and sufficient condition is given for the equivariant cohomology ring of M to be Cohen-Macaulay in terms of the orbit space Q.     

Inhibition of experimental pulmonary metastasis of Lewis lung carcinoma by orally administered beta-glucan in mice

The inhibitory effect on experimental pulmonary metastasis of Lewis lung carcinoma (3LL) of SSG, a (1----3)-beta-D-glucan obtained from the fungus Sclerotinia sclerotiorum IFO 9395, administered orally was examined in mice. Oral administration of SSG for 10 consecutive days just after the intravenous implantation of tumor cells significantly inhibited the experimental pulmonary metastasis of 3LL at a dose of 2000 micrograms. However, SSG administered orally involving other timings was less effective. In comparison with oral administration, SSG was effective when administered intraperitoneally for 10 consecutive days at a dose of 200 micrograms. These results suggest that SSG given by both parenteral and nonparenteral routes is effective in the inhibition of experimental pulmonary metastasis of tumors.     

Bitter principles of Picrasma ailanthoides planchon: Nigakilactones J,K, L,M and N

Five new crystalline bitter principles were isolated from the stem-chips of Picrasma ailanthoides Planchon (Simaroubaceae). Structures of nigakilactones J, K, L, M and N were shown to be 1a, 2a, 3d, 4c and 4b, respectively.     

Fixed point free low dimensional real algebraic actions ofA 5 on contractible varieties

Dedicated to Professor Sh?r? Araki on the occasion of his 60th birthday.     

Nonlinearizable actions of dihedral groups on affine space

Let be a reductive, non-abelian, algebraic group defined over . We investigate algebraic -actions on the total spaces of non-trivial algebraic -vector bundles over -modules with great interest in the case that is a dihedral group. We construct a map classifying such actions of a dihedral group in some cases and describe the spaces of those non-linearizable actions in some examples.