Evaluation of an optical system in the fibercolonoscope: trial manufacture of an instrument with 30 degrees deviation optical system

To evaluate the best optical system for colonoscopy a colonofibrescope was manufactured in which the optical system had a 30 degrees prograde deviation. In this test model, frontal view was easily obtained and close-up observations were possible. At areas with prominent semilunar folds, the zone behind them also came into full view. The bowel lumen could be visualized by angulation, the same as with conventional instruments. The passage trough the sigmoid-descending junction was easy, and visualization or the colon up to the distal transverse colon was accomplished within a short time in the majority of cases without fluoroscopic control.     

Plug closure of patent ductus arteriosus by transfemoral catheter method. A comparative study with surgery and a new technical modification

Plug closure of patent ductus arteriosus without thoracotomy is reliable and can be a good alternative to surgical closure for selected patients. We report our experiences with plug closure in 87 consecutive patients (age range, 3 to 38 years). Closure was successful in 83 patients (95 percent). There has been no mortality, and the failure in four patients (5 percent) was mainly due to an oversized ductus. A major complication during the procedure was dislodgment of the plug into either the aorta or the pulmonary artery, which occurred in five patients (6 percent). The late results were quite satisfactory, with no recurrence of shunting or any other complications. Comparison of these results with those of 100 patients treated surgically showed that the new catheter method did not seem to carry a higher risk but had certain advantages over thoracotomy. A simpler and less time-consuming method using a single catheter has been devised and successfully used in the most recent nine patients without failure. Simplification of the technique has signficantly reduced the time of the procedure and the dose of radiation.     

Studies of the effect of pivalic acid on the hydrogenation rate and the enantio-differentiating ability for the hydrogenation of 2-octanone over a tartaric acid-NaBr-modified nickel catalyst

The effects of the addition of pivalic acid to the reaction media on the hydrogenation rate and the enantio-differentiating ability (e.d.a.) for the hydrogenation of 2-octanone were studied over an (R,R)-tartaric acid-NaBr-in-situ-modified nickel catalyst. It was revealed that the modification with both tartaric acid and NaBr was necessary for increasing the e.d.a. by the addition of pivalic acid to the reaction media. The role of pivalic acid in the enantio-differentiating hydrogenation of 2-octanone was different from that of acetic acid in the hydrogenation of methyl acetoacetate.     

Enantio-differentiating hydrogenation of methyl acetoacetate over modified Raney nickel catalysts prepared by two-step modifications

Two-step modifications of the Raney nickel were examined for the enantio-differentiating hydrogenation of methyl acetoacetate. Among the two-step modifications attempted in this study, the combination of ‘pre-modification with disodium tartrate and NaBr in water’ and ‘in-situ modification with tartaric acid’ resulted in the highest optical yield (84%). This modification process is a greener process than the conventional one carried out under weakly acidic conditions, because this process generated almost no Ni²⁺ ions. The pre-modification with the tartrate and NaBr preferentially eliminated Al³⁺ from the Raney nickel surface.     

High-temperature creep of yttrium-aluminium garnet single crystals

High-temperature creep in single crystals of Y₃Al₅O₁₂ (YAG) was studied by constant strainrate compression tests. The creep resistance of YAG is very high: a stress of ~ 300 MPa is needed to deform at a strain rate of 10^–6 (s^–1) at a temperature as high as 1900 K (~0.84 T _m, (melting temperature)). YAG deforms using the 111 {1¯10} slip systems following a power law with stress exponent n ~ 3 and activation energy E* ~ 720 kJ mol^–1. However, a small dependence of n on temperature and of E* on stress was observed. This stress-dependence of activation energy combined with the observed dislocation microstructures suggests that the high creep resistance of YAG is due to the difficulty of dislocation glide as opposed to the difficulty of climb. Present dislocation creep data are compared with diffusion creep data and a deformation mechanism map is constructed. Large transition stresses (2–3 GPa for 10 m grain size) are predicted, implying that deformation of most fine-grained YAG will occur by diffusion creep.     

Xe capillary target for laser-plasma extreme ultraviolet source

A cryogenic Xe jet system with an annular nozzle has been developed in order to continuously fast supply a Xe capillary target for generating a laser-plasma extreme ultraviolet (EUV) source. The cooling power of the system was evaluated to be 54 W, and the temperature stability was +/-0.5 K at a cooling temperature of about 180 K. We investigated experimentally the influence of pressure loss inside an annular nozzle on target formation by shortening the nozzle length. Spraying caused by cavitation was mostly suppressed by mitigating the pressure loss, and a focused jet was formed. Around a liquid-solid boundary, a solid-Xe capillary target (10070 microm phi) was formed with a velocity of < or =0.01 ms. Laser-plasma EUV generation was tested by focusing a Nd:YAG laser beam on the target. The results suggested that an even thinner-walled capillary target is required to realize the inertial confinement effect.     

Dehydrogenation of Methane over Mo/ZSM-5. Effects of Additives in the Methane Stream

The dehydrogenation of methane was carried out over a Mo/ZSM-5 catalyst. It was revealed that the purity of the methane was very critical for the evaluation of the catalyst activity. In order to study the phenomenon, the effects of the addition of O₂, CO₂, CO or H₂ to the feed were investigated. A small amount of O₂ increased the amounts of aromatic compounds and CO produced. The addition of H₂ scarcely affected the conversion of methane, but it prevented the deactivation of the catalyst, i.e., benzene production remained constant during a 6 h test.     

Low-Temperature Synthesis of Praseodymium-Doped Ceria Nanopowders

Praseodymium-doped ceria (CeO₂) nanopowders have been synthesized via a simple but effective carbonate-coprecipitation method, using nitrates as the starting salts and ammonium carbonate as the precipitant. The precursors produced in this work are ammonium rare-earth double carbonates, with a general formula of (NH₄)_0.16Ce_{1− x} Pr _x (CO₃)_1.58·H₂O (0 < x ≤ 0.20), which directly yield oxide solid solutions on thermal decomposition at a very low temperature of ∼400°C. Praseodymium doping causes a gradual contraction of the CeO₂ lattice, because of the oxidation of Pr³⁺ to smaller Pr⁴⁺, and suppresses crystallite coarsening of the oxides during calcination. Dense ceramics have been fabricated from the thus-prepared nanopowders via pressureless sintering for 4 h at a low temperature of 1200°C.     

Infrared spectroscopy of graft polymers separated from graft copolymers of wool and silk with methyl methacrylate

The HCl- or papain-decomposition residues obtained from reduced wool fibers grafted with 1.5–3.0% methyl methacrylate were extractively fractionated successively with cold acetone, hot acetone, and benzene. Each fraction was examined by infrared spectroscopy. Generally, the 715 cm^?1 spectral band considered to be due to vc-s-c was found in the hot acetone-soluble fraction. It was concluded that the thiol groups on wool keratin provide the main sites of grafting, as might be expected. A similar result was obtained for grafted silk fibroin fibers, the methionine residue being presumed to be related to some of the grafting sites at least. Furthermore, a sort of stereoregularity was observed in some of the graft polymer fractions, isotactic-rich material being obtained in the case of silk fibers. In the range of very low grafting, a stereoregulating effect on the structure of the polymer formed within fibers appears to be present in relation to the grafting or adsorption sites of monomers and the fine structure of fibers.