Selective Cation Exchange in Substituted Tobermorites

Selective cation exchange in tobermorites with three levels of Al³⁺ and Na⁺ substitution for Si⁴⁺ has been investigated. The cation exchange selectivity for a tobermorite with 2 mol% Al³⁺ and 0 mol% Na⁺ substitution increased as follows: Mg²⁺ > Ba²⁺ > Sr²⁺. Cation exchange in the above tobermorite is postulated to take place mainly from edge and planar surface sites and apparently from interlayer Ca²⁺ sites. Tobermorites with 10 and 15 mol% Al³⁺ (and Na⁺) substitution have additional Na⁺ exchange sites in the interlayers and show the following selectivity: Ba²⁺ > Sr²⁺ > Mg²⁺. The cation exchange selectivity in the substituted tobermorites can be explained by the hydrated radii of cations and the steric limitations of the ion exchange cavity in tobermorite; the latter was determined by ²⁷Al and ²⁹Si magic angle spinning nuclear magnetic resonance spectroscopy. These basic selective cation exchange studies of substituted tobermorites are of relevance in nuclear waste treatment and disposal.     

Optical tristability in two-section laser diode

Optical tristability in the current/light output characteristics of a two-section laser diode is observed. Three stable optical outputs are obtained at the same current. Two different types of tristability are observed by controlling injection conditions. The tristability is caused by a cavity structure having a saturable absorber and a complex resonance cavity.<>     

Education and research in Japan

Good education has given Japanese industry and research an advantage over many other countries. Using personal experience of education and research in Japan, the authors outline the present education process and some future developments. The pervasiveness and homogeneity of the main-stream education system in Japan is first described. The programme of study and spartan life of students in university faculties are then outlined. The types of research open to successful students in Japan are illustrated by a broad outline of its funding and examples of research programmes     

A translocation t(8;14) and c-myc gene rearrangement associated with the histological transformation of B-cell acute lymphocytic leukemia (FAB-L2) into Burkitt''s type (FAB-L3) leukemia

During the late rainy season and winter season in 1990, outbreaks of suspected trypanosomiasis in native cattle (Bos indicus) occurred on 13 farms in Petchaboon province, Thailand. Forty-two cattle presented with nervous symptoms including circling, excitation, jumping, aggressive behavior, lateral recumbency, convulsion and finally death. Blood samples from 39 cattle on the two farms in which the outbreaks occurred were collected and examined for the presence of Trypanosoma evansi. It was found that all 16 blood samples from cattle on farm A were positive of T. evansi by mouse inoculation and indirect fluorescent antibody test (IFAT). In cattle from farm B, on the other hand only 37.5% and 39% of the samples were positive by mouse inoculation and IFAT, respectively. T. evansi was detected on impression smears of organs from the three cattle which died with nervous symptoms and also in smears made from their cerebrospinal fluid. In addition, trypanosomes were isolated from the cerebrum, cerebellum, pons and spinal cord by mouse inoculation.     

Effects of citrate ions on the formation of ferric oxide hydroxide particles

The effects of citrate ions on the formation of - and -FeOOH particles were investigated using various techniques. The formation and crystallization of both particles were inhibited by citrate ions, and their particle sizes decreased with increase in the concentration of these ions. Finally, aggregated amorphous particles were formed. The effects of citrate ions appeared to be more significant for -FeOOH than for -FeOOH. This difference could be explained by the pH dependence of the affinity of citrate ions to Fe³⁺ ions. The amorphous -FeOOH particles prepared in the presence of > 10 mol% citrate ions selectively adsorbed water molecules.     

Investigation of Tribo-chemistry by means of Stable Isotopic Tracers: TOF-SIMS Analysis of Langmuir–Blodgett Films and Examination of their Tribological Properties

Deuterium-substituted and ¹³C-substituted octadecanoic acids were applied to study tribo-chemistry of binary-component Langmuir–Blodgett film deposited on Si(100) surfaces. Time-of-flight secondary ion mass spectroscopy was employed to study structure of the film. The isotopic tracers give typical fragment ions composed of the isotopes. Among these typical fragment ions, we paid attention to quasi-molecular ions and deuterium ion as “fingerprint region” of the film structure. The tribological properties of the binary-component film were evaluated by ball-on-plate type tribo-testers. The combination of octadecanol with octadecanoic acid affords good tribological properties, whereas the combination of octadecylamine with the acid gave poor results. The surface analysis of the plate after the tribo-test revealed that the alcohol and the acid were retained on the track even after the rubbing. On the other hand simultaneous removal of the acid and the amine from the surfaces were observed. Interactions between the acid and the amine were considered by the results of the tribo-tests and the surface analysis of the binary-component film.     

X-ray computed tomography used to measure fiber orientation in CFRP laminates

This paper explains a new method to measure the fiber orientation in carbon fiber reinforced plastics (CFRP) laminates from X-ray CT images. In the method, the fiber orientation is analyzed by the application of digital image correlation (DIC) method to the acquired tomographic images. Using DIC, the brightness pattern, which results from the radiodensity difference between fiber and resin, is compared between two different planes in the thickness direction. Then, the three-dimensional displacement of the brightness pattern, which indicates the fiber orientation, can be measured. This study applied the proposed method to a quasi-isotropic CFRP laminate. After X-ray CT imaging, the sample was sectioned and polished. The fiber orientation was then measured experimentally using microscopy. The fiber orientation calculated using the proposed method agrees very well with the experimentally measured one. After demonstrating the validity of the proposed method, we applied it to a plain woven CFRP laminate. Results revealed that an invalid fiber orientation might be calculated for fibers parallel to the plane of the CT image, or for the fiber orientation of the pattern around the outer edge of CT images.     

Ultrasonic motors using piezoelectric ceramic multimode vibrators

The development is reported of an ultrasonic motor using piezoelectric ceramic multimode vibrators consisting of circular or annular plates in which degenerate horizontal vibration modes of the same or different form are used. Two orthogonal nonaxisymmetric vibration modes were used in the same-form case, and the combination of a nonaxisymmetric vibration mode and a radial vibration mode was used in the different-forms case. Some details of the motor design and its experimental characteristics are presented. The ultrasonic motor presented here has a special advantage in its thin construction.     

Adsorbed Atoms and Molecules Destined for a Reaction

The idea of an activation complex is popular for explaining reaction rates, but the characteristics of reactions and catalysis may not be explained in this way. A predestined state for each reaction composed of surface atoms and adsorbed species is responsible for these features. Two single Sn atoms trapped in adjacent half-unit cells of an Si(111) 7 × 7 surface is an example of a predestined state. An isolated Sn atom in a half-unit cell does not migrate to other half-unit cells at room temperature, but when two single Sn atoms are in adjacent half-unit cells they undergo rapid combination to form an Sn₂ dimer. In addition, these two single Sn atoms replace the center Si adatoms and an Si₄ cluster is formed. The spatial distribution of molecules desorbing from surfaces may reflect the predestined states for the desorption processes. The spatial distribution in the temperature-programmed desorption (TPD) of NO on Pd(110) and Pd(211) surfaces and that in the temperature-programmed reaction (TPR) of NO + H₂ were studied. N₂ desorbing from Pd(110) by the recombination of N atoms obeys cos⁶ – cos⁷ but the N₂ produced by a catalytic reaction of NO with H₂ obeys cos. In contrast, the N₂ desorbing with NO at 490 K in the TPD of Pd(110) shows a sharp off-normal distribution expressed by cos⁴⁶( – 38). The adsorption of NO on Pd(211) predominantly occurs on the (111) terrace but the spatial distribution suggests that the predestined states for the reaction and desorption are formed on both the (111) terrace and (100) step surfaces.