Irradiation effects of boron carbide used as control rod elements in fast breeder reactors

The paper describes radiation effects on 8₄C pellets used as control rod elements in the Enrico Fermi Fast Breeder Reactor. Pellet swelling (Δ$\text{V/V}$) caused by irradiation was less than 1% in which crystal lattice swelling was less than 20%. Many microcracks, a main cause of pellet swelling, appeared in the irradiated pellets. The production of microcracks was related to graphite precipitation in the pellets before irradiation. Open pores which did not exist in the unirradiated pellets were formed in the irradiated ones. In a unit cell of B₄C, the α-axis elongated by 0.025 Å and the $\text{c-}\text{axis}$ shrank by 0.07 Å by irradiation. Moreover, we found three recovery stages which were from room temperature to 400°C, from 400 to 750°C and from 850 to 1100°C. The recovery mechanisms in the irradiated pellets are discussed in terms of the helium behavior.     

Photo-induced radicals in glucose and cellobiose

Photo-induced radicals in glucose and cellobiose, the model compounds of cellulose molecule, were studied by ESR spectrometry. Very poor formation of radicals in glucose as compared to those in cellobiose was observed. However, a spectrum showing a singlet line was easily produced by the use of light involving shorter wavelengths. It was estimated to be due to the radical formed at the reducing C₁ position of glucose molecule. By paper chromatography, the photo-irradiated cellobiose was confirmed to split into glucose through scission of glucosidic bonds in the molecule. The ESR spectrum of the acid-hydrolyzed cellulose similar to that of the unhydrolyzed sample was a seven-line spectrum, but the relative signal intensity was here markedly low. This phenomenon seems to be caused by the reduction of amorphous portion in the samples due to acid hydrolysis. It was concluded that the glucosidic bonds in cellobiose and cellulose molecules are very active toward light and play an important role in the radical formation in photo-irradiated samples.     

Numerical study of transverse lattice waves connected with martensitic transformation

The behavior of the transverse lattice wave connected with the nucleation process of martensite is studied, taking into account the anharmonicity, by use of one-dimensional model for the crystal. The key factor which determines the behavior of the transverse lattice waves according to the model is its amplitudeA with respect to the critical amplitudeA _c. As far asA < A _c, the presence of the transverse lattice wave does not lead to the initiation of the martensite. Depending on the variation ofA andA _c with temperature, the model suggests two alternative processes for the initiation of the martensitic transformation. 1) In case the variation ofA _c with temperature is larger than the variation ofA with temperature, the transverse lattice wave develops into the stable nuclei of the martensite, as soon asA _c becomes smaller thanA with decrease of temperature. 2) In case the variation ofA with temperature is larger than the variation ofA _c with temperature, the transverse lattice wave represents the heterophase fluctuation whenA « A _c. The stable martensite is formed with the reduction ofA as temperature is reduced. The presently available experimental data suggest the process 1) as the nucleation mechanism of the martensite. The prominent role of the interface energy between the martensite and the austenite in determining both the structure of the martensite and the dispersion relationship of the transverse lattice wave in the austenite is pointed out.     

The effect of excess gate current on input impedance of a JFET amplifier

When JFET is used as an amplifier, it should be regarded that the effect of excess gate current on the input impedance is changed by gain of the amplifier. The input impedance or conductance with gain of the JFET amplifier is experimentally analyzed applying small signal equivalent circuit.     

Successfully operated case of posterior fossa tuberculoma in childhood (author's transl)

A case of intracerebellar tuberculoma is described in which a tuberculoma was removed successfully through the administration of antituberculous agents, and a full recovery was obtained. The patient was a 3-year-old boy who had been receiving antituberculous agents for about 4 months because of acute inflammation followed by osteomyelitis of his right big toe, which was suspected to be tuberculous, and because of pulmonary tuberculosis diagnosed in a chest roentgenogram taken about 1 month after osteomyelitis was cured. While his osteomyelitis was being treated, disturbance in his gait, due to progressive spastic paraparesis, was not iced, and thereafter left cerebellar symptoms with impairment of equilibrium appeared additionally. Then, he was reffered to our clinic for further neurosurgical examination, and was admitted on November 1, 1974 after right carotid and vertebral angiography was performed via the right axillar artery, in which findings suggesting left cerebellar tumor and internal hydrocephalus were obtained. After he was admitted to our clinic, a diagnosis of tumor of the left cerebellum and internal hydrocephalus was more precisely confirmed by pneumoventriculography. Suboccipital craniectomy was then carried out and the tumor, weighing 60 gm, was completely removed from the left cerbellar hemisphere. The tumor was confirmed as tuberculoma not only by histological findings but also by the vertification of tuberculous bacilli in it. Though, moderate fever lasted for about 2 weeks postoperatively, no obvious meningitic signs or new neurological deficits were noted. The patient showed marked improvement especially in his gait disturbance, and was discharged ambulatory 40 days after the operation, and has since been asymptomatic except for slight ataxic gait. The antituberculous agents have been continuously administered postoperatively.     

Occurrence and determination of a herbicide benthiocarb in rivers and agricultural drainages

The occurrence and determination of a herbicide, benthiocarb, 4-chlorobenzyl N,N-diethylthiolcarbamate (Saturn^®) in rivers and agricultural drainages was investigated. Benthiocarb residues were detected in water samples when it has been applied to rice paddies, after rice seedling transplantation, in concentrations of between 10.00 and 0.11 μg/l. These residues entered into rivers and agricultural drainages as a result of overflows from rice paddies. However, benthiocarb residues could not be found in water samples after the termination of its application to rice paddies, suggesting that the applied benthiocarb might be degraded by microbial and physico-chemical actions such as photochemical reactions occurring on the soil surface. Benthiocarb residue levels were higher in longer rivers than in agricultural drainage. The contribution of rainfall to the benthiocarb concentrations was shown. Benthiocarb in water was extracted with n-hexane and identified by a gas chromatography using a flame photometric detector (sulphur filter 394 nm) and a combined gas chromatography-mass spectrometry-computer system. The minimum detectable amount of benthiocarb in water sample by gas chromatography was 0.56 ng and about 100 ng of benthiocarb could be identified by a gas chromatography-mass spectrometry-computer system.     

Electron-microscopic imaging of single-walled carbon nanotubes grown on silicon and silicon oxide substrates

Direct imaging of single-walled carbon nanotubes (SWNTs) suspended on pillar-patterned Si or SiO2 substrates is investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The suspended nanotubes are successfully observed by direct TEM imaging and it is seen that they have either individual or bundles of SWNTs. Low energy (< or =2 keV) SEM produces high contrast images of suspended SWNTs. On the contrary, when SWNTs contact a SiO2 substrate, they are imaged using electron-beam induced current. The image brightness depends on the length of SWNTs.