Hydrogen absorption/desorption properties of light metal hydroxide systems

In light metal hydroxide systems, hydrogen desorption generally occurs in exothermic reactions; therefore, these reactions are irreversible in principle. However, according to theoretical calculation of thermodynamics, some of these systems can desorb hydrogen in endothermic reactions. In this research, several hydroxide systems were studied to clarify the reversibility of these systems. Six types of hydroxide systems (XH + Y(OH)_n, X: Li, Na, Y: Li, Na, Mg) were prepared by ball-milling, then the desorption properties of these systems were evaluated. As a result, NaH + LiOH and NaH + NaOH systems desorbed hydrogen in endothermic reactions. Also, NaH + NaOH system absorbed hydrogen almost 100% reversibly under 300°C and 1.0 MPa H₂ pressure. The reversibility in NaH + LiOH system was not accomplished in our experimental condition, because high pressure of GPa order is required for the rehydrogenation. In order to modify the desorption kinetics, we added KH catalyst to NaH + LiOH and NaH + NaOH systems. The hydrogen desorption temperature of the two systems was decreased by addition of 1 mol% of KH. The catalytic effect on hydrogen desorption properties was sustained even after the rehydrogenation of KH-added NaH + NaOH system.     

Return cycle mapping after entrainment of ventricular tachycardia

BACKGROUND: The central common pathway, which is the target for ablation in reentrant ventricular tachycardia, can be localized by entrainment mapping techniques. However, localization of the pathway is not always possible because of the elevated pacing threshold and the low voltage and fractionated potentials at the pathway. We examined whether return cycle mapping after entrainment localizes the pathway without pacing at the pathway or recording the potentials from the pathway and determined the required electrode resolution to localize the pathway. METHODS AND RESULTS: Epicardial mapping was performed with 253 unipolar electrodes during and after entrainment of 13 morphologies of ventricular tachycardia that were induced in dogs 4 days after infarction. The return cycle was calculated by subtracting the first activation time from the second activation time after the last stimulus and the return cycle distribution map was constructed for each stimulation site. The return cycle isochrones equal to the ventricular tachycardia cycle length converged on the lines of conduction block irrespective of the stimulation site, and the central common pathway was localized at the region between the intersections of the return cycle isochrones after entrainment from different stimulation sites. The potentials from the central common pathway were not required to localize the pathway, and the mapping accuracy did not change with or without analysis of the potentials from the pathway. According to the correlation between the electrode resolution and the mapping accuracy, an interelectrode distance of 8.5 mm was estimated as sufficient resolution for successful tachycardia termination during radiofrequency ablation guided by return cycle mapping. CONCLUSIONS: Return cycle mapping after entrainment localizes the central common pathway without pacing at the pathway or recording the potentials from the pathway. This new mapping technique could improve the success rate of the ablative procedures.     

Atomic environment of tantalum in the intermediate fluorite phase of SrBi2Ta2O9 thin films

The intermediate phase involved in the production of ferroelectric material SrBi₂Ta₂O₉ has a fluorite structure. If the structure of the intermediate phase were ideal, all the metal ions would have identical cubic oxygen environments. However, the tantalum ions are much smaller than the strontium and bismuth ions which could result in local deviations from the original structure. We present results of X-ray absorption spectroscopy studies which indicate the local tantalum atomic environments for the intermediate fluorite phase and the ferroelectric final Aurivillius phase material, a layer-structure perovskite. For both phases NEXAFS studies indicated very similar electronic structures at the tantalum sites. The EXAFS analysis revealed local structural information and indicated that the intermediate phase has a defect fluorite structure with the oxygen environment for the tantalum being related to that of the TaO₆ octahedra of the final phase material.     

Kinetic study of isotopic exchange reaction between hydrogen and water vapor over a pt/sdbc hydrophobic catalyst sheet

The isotopic exchange reaction between hydrogen and water vapor was studied for the temperature range 313 K to 353 K using 2.2% platinum supported on a hydrophobic styrene-divinylbenzene copolymer (SDBC) sheet. With increasing relative humidity, the exchange rate increased, giving a stepped profile with a knee shape, and the reaction order with respect to hydrogen increased from almost zero to first order. In order to explain this unusual behavior, a simple kinetic model was proposed assuming that the water molecules are adsorbed in a multilayer on the platinum surface, and are subject to the exchange equivalent to finite number of layers. On the other hand, this multilayer of adsorbed water inhibits the transfer of HD to the platinum surface.     

Acquired amylase production induced by radiotherapy in a myeloma patient

A 55-year-old patient with multiple myeloma (IgG-lambda) diagnosed in November 1988 was admitted because of bone pain throughout the body. After plasmapheresis and several courses of chemotherapy, a massive tumor of the left thoracic wall involving the rib appeared. Radiotherapy was performed to ameliorate the severe chest pain, after which myelomatous pleural effusion appeared on the left side. The serum, urine and pleural effusion revealed increased activity of amylase of the salivary type. Amylase activity was also detected in the supernatant of myeloma cells cultured from pleural effusion. We reviewed 12 cases of ectopic amylase-producing multiple myeloma. All the cases except one have been reported from Japan, and hyperamylasemia in these cases was detected at diagnosis or during course of the illness. Moreover, cytogenetic analysis of myeloma cells of previous reports revealed structural abnormalities including chromosome 1, near the amylase gene locus. This case also showed t (1; 10) (q 21?; q 26) by examination of 8 metaphase derived from bone marrow. These observations suggested that ectopic amylase production was induced by irradiation to the plasmacytoma of thoracic wall.     

Identification and partial characterization of a glycoprotein species with high affinity for methylmercury in peripheral nervous tissues of man and experimental animals

A small amount of a glycoprotein species (21-kDa glycoprotein) with high affinity for methylmercury (MeHg) was detected in the post-nuclear or post-mitochondrial supernatant fraction of the homogenate of rat sciatic nerve on electrophoresis and autoradiography after binding of Me203Hg to the fraction. The 21-kDa glycoprotein was also found in the subcellular fractions of mouse, hamster, guinea pig, rabbit and human peripheral nervous tissues. Experiments with the cellular fractions of the tissues revealed that the 21-kDa glycoprotein is localized mainly in the myelin fraction, whereas it was not found in the cellular fractions of brain, spinal cord and nonneural tissues, such as kidney and liver. The specific binding activity of the 21-kDa glycoprotein with MeHg was 12-15 fold that of the major myelin protein, Po. It was shown that the interaction of the 21-kDa glycoprotein with MeHg was mediated through sulfhydryl groups in experiments with iodoacetamide and dithiothreitol. The amino acid compositions of the rat and human 21-kDa glycoproteins were similar but very different from that of a typical metallothionein. The N-terminal amino acid sequences of the two components of the rat 21-kDa glycoprotein were identical to those of P0 and PMP-22, respectively. The in vitro binding of MeHg was also observed in the myelin fraction obtained from the sciatic nerves of MeHg-dosed rats.     

Study of crystallization of LiNbO3 films from metal alkoxides

The crystallization process of epitaxial LiNbO₃ films on sapphire (0 0 0 1) substrates was investigated by Raman microprobe spectroscopy. LiNbO₃ gel films were prepared by the sol-gel method using metal alkoxide precursors on sapphire (0 0 0 1) substrates and heat treated at various temperatures below 500 °C to produce epitaxial LiNbO₃ films. Analyses by electron spectroscopy for chemical analysis and SEM revealed LiNbO₃ films were stoichiometric and homogeneous. Raman spectra of the film prepared at 250 °C indicated that the NbO₆ octahedral coordination structure in LiNbO₃ began to form as the initial state of crystallization. As the heat-treatment temperature was raised, the Raman bands became sharper and increased in spectral intensity and were seen to be the characteristic Raman bands of crystalline LiNbO₃. Refractive indices of the obtained films indicated appropriate values. As a method to crystallize the more highly preferred orientation to (0 0 6) LiNbO₃ film at relatively low temperature, the formation of an underlayer film from diluted solution prior to multiple dip-coating, was found to be very promising.     

Gigahertz SAW filter developed using new submicrometre techniques

A photolithographic technique was developed that uses 1/10-reduction photoprinting with a phase-shifting mask to make gigahertz SAW devices. Combined with a positive-type resist, this new technique produces IDT electrodes with smaller deviations in width compared with using a negative-type resist. Very sharp 40 nm thick AI electrodes with 0.4 μm lines and spaces were achieved. A 2.5 GHz SAW filter suitable for optical communication systems was developed     

Static and dynamic finite element analysis of transformation toughening in ceramic materials

Computational studies have been conducted for the phenomenon of ‘transformation toughening’ which is observed in zirconia-containing ceramics such as PSZ (partially stabilized zirconia). The new constitutive modeling for transformation plasticity in which a stress history-dependent internal state variable is employed has been applied to the finite element analysis of stationary and growing macro-cracks under static and dynamic loading. The transformation toughening effect is discussed, along with the influence on it of the size of the transformed damage zone and the various parameters in the equations to be solved, through the observation of the behavior of the general crack tip energy release parameter, the T^*-integral.