Preparation of glass-fiber membranes grafted with poly(NIPAAm containing triphenylmethane leucocyanide) and permeation of solutes through the membranes

Glass-fiber membranes (GF membranes) grafted with poly(N-isopropylacrylamide containing triphenylmethane leucocyanide) [poly(NIPAAm–LeCN)] were prepared. Ultraviolet irradiation of the GF membranes with poly(NIPAAm–LeCN) induced a change in the phase-transition temperature of the poly(NIPAAm) segments. The changes in both the phase-transition temperature of the poly(NIPAAm) segments and the permeation rate of solutes are discussed in relation to the dissociation of LeCN molecules. © 1995 John Wiley & Sons, Inc.     

A Mathematical Model of Perception with Reference to Peripheral Vision and its Application to the Hermann Grid Illusion

Central vision and peripheral vision are two of main components of visual perception. The functional differences between the two visions are considered with two points of view: the physiological receptive field and the psychological perceptive field.

The authors propose a retinal model of lateral inhibition. The output is discrete summation of ganglion cell responses through the Difference of Gaussian (DOG) function of the coupling width. The coupling width is given by the size of receptive field, according to Fisher’s findings that the distribution of the ganglion cell density decreases from the fovea to the peripheral area. Sampling points of the summation correspond to the positions of the ganglion cells, so that a number of points in all the same in each receptive field. The coupling width was determined by the data of Jung and Spillmann’s (1970) psychological experiment. As an application of this model, the Hermann grid illusion is quantitatively explained.

     

Hydrothermal processing of metal based compounds and carbon dioxide for the synthesis of organic compounds

Reservation of carbon-based resources including fossil fuel is an important issue for futuristic development. As a possible carbon resource, we had proposed a process for the reduction of CO₂ by hydrothermal method. In the process, CO₂, aqueous solvent, and reductant are to react under hydrothermal condition, to generate organic compounds. In this report, the extension of the process to continuous-type process has been focused. For the experiments, newly developed continuous-type equipment was used. Metallic materials such as carbon steel cutting chaff was treated at 200 °C, 2.0 MPa under the constant flow of CO₂ gas and solvent, with or without the hydrogenation catalyst, Ni. During the experimental period, reaction gas and liquid are collected successively. The samples are analyzed with GC and TOC. In treatment without Ni powder, organic compound was detected in neither reaction gas nor solution, while the occurrence of CO was confirmed. On the other hand, in the experiment with Ni powder additionally, formic acid was generated. It has been confirmed that the reaction process proceeds even in the continuous-type treatment including the catalytic effect of Ni.     

Structural anisotropy of silica hydrogels prepared under magnetic field

Birefringence measurements have been carried out on the Pb-doped silica hydrogels prepared under various magnetic fields up to 5T. The silica gels prepared at 5T were used as a medium of crystal growth of PbBr₂, whose result implied the structural anisotropy; an aligned array of crystallites was obtained by transmission electron microscopy. While the samples prepared at 0, 1, and 3T have no birefringence, we found that the samples have negative birefringence on the order of magnitude 10^− 6 as if the direction of the magnetic field is the optic axis of a uniaxal crystal. To the authors' knowledge, the birefringent silica hydrogels were obtained by gelation under magnetic field for the first time. Also, scanning microscopic light scattering experiments have been performed. The results indicate that the characteristic length distribution for birefringent samples is narrower than that for non-birefringent ones.     

Effects of titanium surface modifications on bonding behavior of hydroxyapatite ceramics and titanium by hydrothermal hot-pressing

In order to improve the interface strength in the bonded body of hydroxyapatite (HA) ceramics and Ti disks prepared by a hydrothermal hot-pressing (HHP) method, the effects of Ti surface modification on the bonding behavior were investigated. The reaction layer composed of titanium dioxide and sodium titanate was formed on the Ti surface using a 5 M NaOH solution with the objective of increasing the interface strength between the Ti substrate and HA ceramics to be formed by the HHP method. Three conditions with different temperature and treatment times were tested to modify the Ti surface. A mixture of calcium hydrogen phosphate dihydrate and calcium hydroxide was used as a starting powder material for solidifying HA. Solidification of HA and its bonding with Ti were achieved simultaneously by using the HHP method at the low temperature as low as 323 K. 3-point bending tests were conducted to obtain an estimate of the interface fracture toughness of HA/Ti. The Ti surface modification conducted at 323 K for 2 h using the hydrothermal NaOH solution was shown to be most effective among the three conditions tested. The hydrothermal Ti surface modification enabled us to increase significantly the interface fracture toughness. The enhancement of the interface fracture toughness was possibly due to the presence of anatase formed on the Ti surface and the good adhesion in the bioactive layer.     

Aquatic toxicity and biodegradability of advanced cationic surfactant APA-22 compatible with the aquatic environment

Cationic surfactant is a chemical substance used in hair conditioner, fabric softener and other household products. By investigating the relationship between the aquatic toxicity and the chemical structures of two types of mono alkyl cationic surfactants, alkyl trimethylammonium salts and alkyl dimethylamine salts, we have found that the C22 alkyl chain length is effective to reduce the toxicity. Besides, we have recognized that the amidopropyl functional group contributes to the enhanced biodegradability by investigating the biodegradation trend of (alkylamidopropyl)dimethylamine salt (alkyl chain length: C18). Based on these findings, we have developed mono alkyl cationic surfactant called APA-22, N-[3-(dimethylamino)propyl]docosanamide salt. APA-22 is formed by the C22 alkyl chain, amidopropyl functional group and di-methyltertiary amine group. We evaluated the aerobic and anaerobic biodegradability of APA-22 by two standard methods (OECD Test Guideline 301B and ECETOC technical document No.28) and found that this substance was degraded rapidly in both conditions. The toxicity to algae, invertebrate and fish of this substance are evaluated by using OECD Test Guideline 201, 202 and 203, respectively. All acute toxicity values are >1 mg/L, which indicates that environmental toxicity of this substance is relatively less toxic to aquatic organism. In addition, we estimated the biodegradation pathway of APA-22 and observed the complete disappearance of APA-22 and its intermediates during the test periods. Based on the environmental data provided above, we concluded that APA22 is more compatible with the aquatic environment compared to other cationic surfactants with mono long alkyl chain.     

X-ray absorption study on LiNi0.8Co0.15Al0.05O2 cathode material for lithium-ion batteries

LiNi_0.8Co_0.15Al_0.05O₂, being one of the promising cathode materials for lithium-ion batteries, shows distinct capacity fades after charge/discharge cycling and/or storage at high temperatures. The origin of the capacity fade has been explored by investigating the electronic and structural changes of the cathode material using X-ray absorption spectroscopy (XAS). Ni K-edge XAS measurements were performed in two different modes: surface-sensitive conversion electron yield (CEY) mode and bulk-sensitive transmission mode. Ni K-edge XANES data revealed that, after the cycling and aging tests, the bulk-averaged Ni valences were reduced, implying the existence of divalent Ni atoms. Further reductions of Ni atoms were observed at the surface of the cathode material particles, and the ranges of the Ni valence change upon charging became narrower, indicating the existence of the Ni atoms that did not oxidize. These changes which occur prominently at the surface are probably the main causes of the capacity fade.     

Multiperiod fringe projection interferometry using a backpropagation method for surface profile measurement

Interference fringes with different periods are projected on an object surface. There is a constant phase point where the phase of the fringe is kept at a constant value while the period is scanning. Multiple optical fields with different periods on the object surface are made from detected phases of the fringes. The multiple optical fields are backpropagated to the constant phase point of the phase where all of the phases of the multiple backpropagated fields become the same value and the amplitude of the sum of the multiple backpropagated fields becomes maximum. The distance of the backpropagation provides the position of the object surface. Some experiments show that this method can measure an object surface with discontinuities of several millimeters with high accuracy of several micrometers.     

Design of novel biomimetic polymer gels with self-oscillating function

We report a novel biomimetic gel that undergoes autonomous swelling-deswelling oscillations without on-off switching of external stimuli, similar to heartbeat. The mechanical oscillation of gel was produced via oscillating chemical reaction, called the Belousov-Zhabotinsky (BZ) reaction. We have prepared an ionic gel consisting of the cross-linked poly(N-isopropylacrylamide) chain to which ruthenium tris(2,2′-bipyridine), a catalyst for the BZ reaction, was covalently bonded. The BZ reaction occurring within the gel matrix generates periodic redox changes of the catalyst moiety. This chemical oscillation is converted into the mechanical oscillation of the polymer network. As a result, the gel exhibits a periodical swelling-deswelling change. The self-oscillating behaviors of the gel were investigated in detail. When the gel size is smaller than the chemical wavelength, the redox change occurs homogeneously in the gel. In this case, the volume change is isotropic and the mechanical oscillation synchronizes with chemical oscillation without a phase difference. The period and amplitude can be controlled by changing the outer substrate concentrations. In the case of rectangular shape, chemical wave propagates along the length of the gel. The wavelength and velocity depend on the reaction rate of autocatalytic process as well as the diffusivity of the activator. The dynamic behavior that locally shrunken (or swollen) parts propagate was observed, similar to the peristaltic motion of worms. By using lithography technique, a ciliary motion actuator made of the gel has been demonstrated. These self-oscillating gels may be useful in a number of important applications to intelligent biomaterials such as pulse generator or chemical pacemaker, auto-mobile actuators or micropumps with peristaltic motion, device for signal transmission, etc.     

Comparison of Monte Carlo calculation methods for effective delayed neutron fraction

Monte Carlo calculation methods to estimate the effective delayed neutron fraction β_eff are investigated: one is proposed by Meulekamp et al. and the other is by Nauchi et al. It is revealed that both the methods calculate the delayed neutron fraction weighted with the importance functions defined by Kobayashi. The accuracy of the methods are also examined for several simple benchmark systems. Consequently, it is found that Meulekamp’s method causes ∼5% discrepancies in the β_eff values for fast systems; Nauchi’s method gives good results for fast bare systems but ∼10% discrepancies for fast reflected systems. Both the methods calculate the β_eff values approximately within the accuracy of ∼2% for thermal systems.