Showing papers by "Hanyang University published in 1981"

Giant Polytene Chromosomes from the Ovaries of a Drosophila Mutant

Abstract: The chromosomes of the ovarian nurse cells of Drosophila melanogaster fall apart during their cycles of endoreduplication. However, chromosomal synapsis occurs in the pseudonurse cells produced in certain mutant females. The resulting polytene chromosomes undergo developmental changes that are strikingly different from those recorded for the giant chromosomes of the larval salivary gland cells.

Reactions of Molybdenum and Tungsten Carbides with Oxygen at High Temperatures

Abstract: The interaction of Mo2C, W2C and WC with O2 has been measured between 1300 and 2100 K and 10−4 and 40 mbar O2. The weight loss of the carbides is very similar to that of Mo or W, respectively. The reason for this is a metallic surface layer produced on the samples by a fast CO reaction. Its thickness is reduced again by the evaporation of volatile oxides. The superimposition of these two reactions finally results in a steady state with a constant layer thickness between 0.1 and 100 µm. The layer growth and steady state conditions can be calculated from literature data for binary systems. The theoretical values are in agreement with experimental results and show similar trends.

Calculation of Neutron and Gamma-Ray Flux-to-Dose-Rate Conversion Factors

Abstract: This paper presents flux-to-dose-rate conversion factors for neutrons and gamma rays based on the American National Standard Institute(ANSI) N666. These data are used to calculated the dose rate distribution of neutron and gamma ray in radiation fields. Neutron flux-to-dose-rate conversion factors for energies from to 20 MeV are presented; the corresponding energy range for gamma rays is 0.01 to 15 MeV. Flux-to-dose-rate conversion factors were calculated, under the assumption that radiation energy distribution has nonlinearity in the phantom, have different meaning from those values obtained by monoetiergetic radiation. Especially, these values were determined with the cross section library. The flux-to-dose-rate conversion factors obtained in this work were in a good agreement to the values presented by ANSI. Those data will be a useful for the radiation shielding analysis and the radiation dosimetry in the case of continuous energy distributions.