We propose a new regularization method based on virtual adversarial loss: a new measure of local smoothness of the conditional label distribution given input. Virtual adversarial loss is defined as the robustness of the conditional label distribution around each input data point against local perturbation. Unlike adversarial training, our method defines the adversarial direction without label information and is hence applicable to semi-supervised learning. Because the directions in which we smooth the model are only "virtually" adversarial, we call our method virtual adversarial training (VAT). The computational cost of VAT is relatively low. For neural networks, the approximated gradient of virtual adversarial loss can be computed with no more than two pairs of forward- and back-propagations. In our experiments, we applied VAT to supervised and semi-supervised learning tasks on multiple benchmark datasets. With a simple enhancement of the algorithm based on the entropy minimization principle, our VAT achieves state-of-the-art performance for semi-supervised learning tasks on SVHN and CIFAR-10.

No abstract

No abstract

This paper reports the two-photon absorbing and orange-red fluorescence emitting properties of a series of new 2,1,3-benzothiadiazole (BTD)-based D-pi-A-pi-D-type and star-burst-type fluorescent dyes. In the D-pi-A-pi-D-type dyes 1-6, a central BTD core was connected with two terminal N,N-disubstituted amino groups via various pi-conjugated spacers. The star-burst-type dyes 8 and 10 have a three-branched structure composed of a central core (benzene core in 8 and triphenylamine core in 10) and three triphenylamine-containing BTD branches. All the BTD-based dyes displayed intense orange-red color fluorescence in a region of 550-689 nm, which was obtained by single-photon excitation with good fluorescent quantum yield up to 0.98 as well as by two-photon excitation. Large two-photon absorption (TPA) cross-sections (110-800 GM) of these BTD dyes were evaluated by open aperture Z-scan technique with a femtosecond Ti/sapphire laser. The TPA cross-sections of D-pi-A-pi-D-type dyes 2-6 with a benzene, thiophene, ethene, ethyne, and styrene moiety, respectively, as an additional pi-conjugated spacer are about 1.5-2.5 times larger than that of 1c with only a benzene spacer. The TPA cross-sections significantly increased in three-branched star-burst-type BTDs 8 (780 GM) with a benzene core and 10 (800 GM) with a triphenylamine core, which are about 3-5 times larger than those of the corresponding one-dimensional sub-units 9 (170 GM) and 11 (230 GM), respectively. The ratios of sigma/e(pi) between three-branched and one-dimensional dyes were 6.5:3.8 (for 8 and 9) and 6.0:4.0 (for 10 and 11), which are larger than those predicted simply on the basis of the chromophore number density (1:1), according to a cooperative enhancement of the two-photon absorbing nature in the three-branched system.

No abstract

Novel conveyer gels exhibiting autonomous peristaltic motion without external stimuli were prepared by copolymerizing temperature-responsive N-isopropylacrylamide (NIPAAm), ruthenium tris(2,2'-bipyridine) (Ru(bpy)(3)) as the catalyst for the Belousov-Zhabotinsky (BZ) reaction, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). When the gel was immersed in the catalyst-free BZ solution, the BZ reaction occurred in the gel and the chemical wave propagated followed by the peristaltic motion of the gel. In this study, we investigated the influence of the AMPS feed ratio on the network structure and the swelling-deswelling properties of the poly(NIPAAm-co-Ru(bpy)(3)-co-AMPS) gels. The gel had a microphase-separated structure when the AMPS feed ratio was less than 5 mol % due to the effect of the poor solvent in the polymerization process. On the other hand, when the AMPS feed ratio is more than 10 mol %, the gel is a homogeneous structure. The microphase-separated structure highly improved the swelling-deswelling kinetics and generated a swelling-deswelling amplitude of more than 10% of the gel thickness, which was approximately 10 times larger than that of the gel with a homogeneous network structure. Further, we attempted to transport an object by utilizing the peristaltic motion of poly(NIPAAm-co-Ru(bpy)(3)-co-AMPS) gels. A cylindrical poly(acrylamide) (PAAm) gel was transported on the gel surface with the propagation of the chemical wave when the AMPS feed ratio was low (less than 2.5 mol %). We have proposed a model to describe the mass transport phenomena based on the Hertz contact theory, and the relation between the transportability and the peristaltic motion was discussed. It was found that the microphase-separated structure of the gel had an important role for mass transport phenomena.

It's alive! A polymer gel has been developed that can generate a peristaltic motion without external stimuli. The motion is produced by dissipating the chemical energy of an oscillating reaction that occurs inside the gel. Although the gel is solely composed of a synthetic polymer, it shows independent motion as if it were alive. The motion of the gel can be harnessed to transport objects with millimeter dimensions (see picture).

A novel self‐oscillating gel actuator with gradient structure, which generates a pendulum motion by fixing one edge of the gel without external stimuli was achieved. The gel was synthesized by copolymerizing the ruthenium catalyst for the Belousov‐Zhabotinsky reaction with N‐isopropylacrylamide and 2‐acrylamido‐2‐methylpropane sulfonic acid. Furthermore, we clarified that the period and amplitude for the self‐oscillating behavior of the gel actuator are controllable by changing the composition, temperature, and size of the gel. The maximum amplitude of the novel gel actuator is about a 100 times larger than that of the conventional self‐oscillating gel system.magnified image