Results 1 - 10 of 297
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[en] On the basis of the features outlined, JAEA staff will produce the medical radioisotopes of 99Mo, 90Y, 64Cu, and 67Cu from a neutron beam generated by the natC(d,n) reaction. One of the unique features of the proposal is the capability to produce all of the above-mentioned medical radioisotopes by means of accelerator neutrons. Thus, the natC(d,n) reaction produces fast neutrons possessing an energy spectrum up to 40 MeV with a most probable energy of 14 MeV that can be used to measure the production yields of 99Mo, 90Y,
[en] The neutrinoless double beta (0ν ββ) decays of 76Ge to 0+ and 2+ states in 76Se were studied by the β-γ coincidence method, where a 171 cc Ge detector is surrounded by a 4π NaI detector. The half-lives for the 0+ → 0+ and 0+ → 2+ 0ν ββ decays were obtained as T1/2(0+ → 0+) ≥ 7.4 x 1022 years and T1/2(O+ → 2+) ≥ 5.6 x 1022 years. The present status of 100Mo double beta decays by using Si(Li) detectors were discussed. 7 refs
[en] A new procedure for introducing tritium into the carbohydrate portions of glucosyl- and galactosylceramides was developed using a new catalyst, CrO3-graphite, which specifically oxidizes the primary alcohol group to the aldehyde. About 10% of the glycolipid was converted to the aldehyde and the aldehyde produced was then reduced back to the original form with KB3H4. After methanolysis, more than 96.7% of the radioactivities of [3H]glucosyl- and [3H]galactosylceramides were found to be located in the carbohydrate portions, and the specific activities of the [3H]galactosyl- and [3H]glucosylceramides were 2.08 to 4.30 X 10(4) cpm/nmol, which could be increased greatly by purifying the aldehydes and reducing them with KB3H4. In addition, beta-galactosidase activity was successfully determined with [3H]galactosylceramide as the enzyme substrate; the Km was 18.73 mM and the Vmax was 11.63 nmol/mg/h, indicating that no significant structural modification occurs during the oxidation
[en] Brain ischemia produces cerebral acidosis that is associated with a rise in lactic acid levels. It is generally thought that the acidosis is due to lactic acid. To investigate this, rats were made hypoglycemic with insulin and the cerebral ischemia was produced. P-31 MR imaging and H-1 MR spectroscopy were used to measure pH and lactate. Hypoclygemia inhibited the rise in lactic acid levels but did not affect pH. Therefore, the fall in pH produced by cerebral ischemia cannot be due to lactic acidosis
[en] We propose a new method to significantly increase the quantum efficiency of a photomultiplier tube by employing a multi-photocathode and a mirror to produce photoelectrons by reusing photons transmitted by a single photocathode. In order to estimate the expected performance of the new photomultiplier, we studied the spectral responses of the reflectance, transmittance, and quantum efficiency of a K2CsSb photocathode as a function of the wavelength of incident light. A large enhancement of the quantum efficiency is expected in the regions between λ=280 and 650 nm. (author)
[en] Two-detector coincidence Doppler broadening (CDB) method of positron annihilation radiation is applied to the study of precipitates in metals. As the first step, the CDB spectra for many kinds of elements are measured to obtain the 'fingerprint' of each element for the chemical analysis of the precipitates in metals. Utilizing the fingerprint of Cu, we made chemical analysis of nano-particles formed in the initial stage of thermal aging in a Fe-Cu alloy, and found that the particles are consisting of Cu only and free from vacancies, which demonstrates the usefulness of this method in the study of the precipitates.
[en] It is investigated whether a new method to analyze the short lifetime component by using the positron age-momentum correlation technique (AMOC) can be applied to determine the lifetime of para-positronium in some insulation materials. The results indicate that the method is not applicable to the case.
[en] Pre-precipitation solute clustering in Al-Li-Cu-Mg-Ag and Al-Cu-Mg-Ag alloys has been investigated by coincidence Doppler broadening (CDB) spectroscopy of positron annihilation and three-dimensional atom probe (3DAP) analysis. Although Ag-Mg co-clusters form in the Al-Cu-Mg-Ag alloy in the early stage of aging, no evidence for the co-cluster formation was obtained from the Li containing alloy using 3DAP. While CDB spectra indicated that vacancies are associated with Ag after aging for 15 s in the Al-Cu-Mg-Ag alloy, vacancy-Ag association is suppressed in the Li containing alloy. Based on the 3DAP and CDB results, the reasons for the completely different clustering behaviors observed in these two similar alloys are discussed