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A high time- and spatial-resolution radio interferometer for solar observations has been constructed at Nobeyama (Figure I.; Nakajima et al. 1994). The Nobeyama Radioheliograph consists of 84 antennas, 0.8m in diameter, arranged on a T-shape lines of 500m in the EW and 220m in the NS directions. The time resolution is 50 ms and the spatial resolution is 10”. The field of view is 40’ at the observing frequency 17GHz, which enables us to watch the whole sun. The radioheliograph has observed hundreds of flares during the few months since the beginning of regular observations in July ‘92, and such powerful performance has never before been demonstrated in the history of solar radio observations.
The magnetic properties of Ce@C82 have been studied. The magnetic anisotropy of Ce@C82 was analyzed taking account of the crystal field of the interior C82 cage acting on Ce3+ ion. Results showed that the reduction of the susceptibility at low temperature was caused due to the antiferromagnetic coupling between Ce3+ ion and C82 cage. The magnetization measurement at several temperatures also supported the antiferromagnetic interaction at low temperature. The magnetic susceptibility larger than the calculated one was measured at higher temperatures due to the magnetic interaction between the metallofullerenes and between the particles in the crystal. The magnetization of some frozen Ce@C82 solutions was found to depend on the applied field magnitude. The dependence suggested that the magnetic anisotropy of Ce ion induced a torque to restrict the rotational motion of Ce@C82 by the field.
A novel characterization method is applied to study the evolution of microstructures during densification of silicon nitride ceramics. This characterization method involves an immersion liquid for making green and sintered bodies transparent, and a subsequent direct optical microscopic examination. Granules were prepared with the spray drying processand formed into green bodies by CIP. After sintering at various temperatures, the specimens were examined for microstructural evolution. Large pores were located at the center and boundary regions of granules left in the green bodies; they were not removed by densification and resulted in large pores in the sintered body, possibly forming fracture origin in ceramics.
Processes limiting the growth of GaAs grown by an alternate gas supply are investigated by kinematical analysis. Based on these results, it is shown that the atomic layer epitaxial (ALE) window is expanded on the high temperature by the suppression of the decomposition of column III gas sources using a nitrogen carrier gas and on the low temperature side by the enhancement of their chemisorption to substrate surface atoms by a new method using a cracking tube. The latter enables us to achieve ALE of AlAs for the first time. Moreover, the carbon concentration is reduced by one order of magnitude by such a reaction control.
The Harman method was applied to measure thermal conductivity κ of thermoelectric materials, and the reliability of the measured κ was investigated. The quantitative κ requires a highly sensitive technique to measure minute Peltier heat. Temperature difference by Peltier heat pumping was successfully measured by developing the DC method of resistance measurement. κ of n-type Bi2Te3 sintered compact and n-type PbTe boules was measured at 295K by the Harman method. Static comparative method was also applied to obtain the standard value of κ. In the case of Bi2Te3, the κ by the Harman method agreed well with the standard value. In the case of PbTe in the electron concentration ne range <5 × 1024/m3, the κ almost agreed with the standard value. However, PbTe in the ne range ≥1 × 1025/m3 showed a larger κ than the standard value. The Harman method has an error to give the larger κ for the material with a large carrier component κ, of κ This error is due to the fast conduction of Peltier heat by the carrier. The reliable κ can be measured for the material with a small κ,.
By using Krätschmer-Huffman synthesis and HPLC separation method we have isolated a series of novel fullerenes and endohedral fullerenes. Various spectroscopic techniques, e.g., MS, NMR, UV-vis-NIR, TEM, X-ray diffraction spectrometry etc., were adopted to characterize the isolated fullerenes. Several fullerenes were revealed to hold novel structures and electronic properties. For examples, C80(D5d) was isolated and characterized to have an ellipsoidal structure which is in fact one of the shortest SW-nanotubes; The isolation of Sc2@C66 breaks the well-known isolated-pentagon-rule (IPR) for the first time, which shows that the unconventional fullerenes may be dramatically stabilized through encaging metal atoms; Sc2C2@C84 is a novel molecular endohedral fullerene in which the Sc2C2 cluster rotates rapidly along the main C2 axis of C84(D2d). This fullerene is predicted to be a molecular magnet and may be used as nano-switcher in electronics.
Liquid phase diffusion bonding was applied to the development of the joined thermoelectric material Pb-Sn-Te, which was expected to be superior to the monolithic Pb-Sn-Te. A Sn sheet 50μm thick was used for the inserted material. The sheet was sandwiched between Pb-Sn-Te segments with different hole concentrations, and subsequently the bonding was performed under 2MPa at 700K for 15min in Ar. The Sn sheet was changed to a SnTe interfacial layer of less than 10μm in thickness. The interfacial layer showed high toughness, and good ohmic and thermal contact up to 550K. Liquid phase diffusion bonding was an excellent technique for joining of thermoelectric material Pb-Sn-Te.
Occipital nerve block is usually considered to be a very simple and safe regional anaesthetic technique. We describe a case of sudden unconsciousness during a lesser occipital nerve block in a patient with an occipital bone defect. A 63-year-old man complained of headache, which was localized to the right occipital region. A right lesser occipital nerve block with a local anaesthetic was performed for treatment. During the lesser occipital nerve block, the patient suddenly became disturbed and lost consciousness. Two hours after the incident, the patient was fully awake without neurological sequelae. He had previously undergone a microvascular decompression for right trigeminal neuralgia. The patient had a bone defect following craniotomy. We believed that the loss of consciousness during lesser nerve block may be due to a subarachnoid injection. Occipital nerve block is relatively contraindicated in the presence of a bone defect.
Microstructure evolution was studied in silicon nitride ceramics by a novel characterization method, and its relevance to the strength was discussed. The characterization method involves an immersion liquid for making green and partially sintered bodies transparent, and a subsequent direct optical microscopic examination. Granules for compaction process were prepared with the spray-drying process and were found to contain pores or deep dimples. Green bodies formed by CIP with these granules contain regularly arrayed pores at the center of granules and also crack-like voids at the boundaries of granules. These pores were preserved in the sintering process and resulted in large pores in the sintered body. They behave as fracture origin in ceramics and reduce the fracture strength. The Weibull modulus was high due to the presence of uniformly distributed pores.
A parameter study of implosion, burn, and gain of D–T ignitor/D3He fuel pellets is presented for a D3He inertial confinement fusion reactor. It is found from burn simulation that attaining a quasi-isobaric state with a temperature of 4 keV and pR value of 2.5 g/cm2 for the D–T ignitor and 0.8 keV and 9.5 g/cm2 for the D3He main fuel would suffice to obtain a pellet gain of ∼40–50 required for the D3He reactor. With 30-MJ laser irradiation and the coupling efficiency of 10%, the density of the target is assumed to be imploded to 5,000 times the liquid density. However, in the implosion simulation to realize the above configuration it is found that after void closure the central hot D–T ignitor region is ignited, while the bulk of the D3He main fuel is still imploding with high velocities. This preignition of the D–T ignitor leads to a low compression of the main fuel and prevents the D–T/D3He pellet from obtaining the required pellet gain. The pellet gain obtained is only ∼3.
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