無配偶生殖をするイチゴツナギ属植物の偽受精への生長物質の影響

京都大学0048新制・論文博士農学博士論農博第92号新制||農||44(附属図書館)学位論文||S40||N139(農学部図書室)1200(主査)教授 西山 市三, 教授 今村 駿一郎, 教授 赤井 重恭学位規則第5条第2項該当Kyoto UniversityDA

Field-Induced Ferromagnetic Order and Colossal Magnetoresistance in La_{1.2}Sr_{1.8}Mn_2O_7: a ^{139}La NMR study

In order to gain insights into the origin of colossal magneto-resistance (CMR) in manganese oxides, we performed a ^{139}La NMR study in the double-layered compound La_{1.2}Sr_{1.8}Mn_2O_7. We find that above the Curie temperature T_C=126 K, applying a magnetic field induces a long-range ferromagnetic order that persists up to T=330 K. The critical field at which the induced magnetic moment is saturated coincides with the field at which the CMR effect reaches to a maximum. Our results therefore indicate that the CMR observed above T_C in this compound is due to the field-induced ferromagnetism that produces a metallic state via the double exchange interaction

Interannual variability of the vertical descent rate in the Antarctic polar vortex

To investigate a descent rate in the Antarctic polar vortex, we analyzed the long-lived trace gas data derived from the Halogen Occultation Experiment on board the Upper Atmosphere Research Satellite during the 6-year period from 1992 to 1997. By comparing the Antarctic fall (February and March) and spring (September and October) methane profiles, we estimated the middle stratospheric descent for each of the six winters. Large year-to-year variations are seen (1.2–1.8 km month−1 at 0.6 ppmv), which consist of a biennial oscillation and a decreasing trend for the period analyzed. The descent rate is larger in the even years (1992, 1994, and 1996) than in the odd years (1993, 1995, and 1997). Dynamical fields for the 6 years are also analyzed using the United Kingdom Meteorological Office assimilation data. The differences between the even and odd years are clear in the midwinter. In the even years the downward and poleward movement of the westerly jet occurs earlier. The thermal wind relation infers that this event is associated with the development of a "warm pool" around the Antarctic stratopause, resulting from adiabatic heating due to the downward motion of air. Planetary wave activity over the winter season is more vigorous in the even years than in the odd years, suggesting a close relationship between the mean flow and planetary waves