Assessing Vegetation Resistace from Observed Temporal Water Surface Profiles of Flood Flows in Rivers

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Bigradient Phase Referencing

We propose bigradient phase referencing (BPR), a new radio-observation technique, and report its performance using the Japanese very-long-baseline-interferometry network (JVN). In this method, a weak source is detected by phase-referencing using a primary calibrator, in order to play a role as a secondary calibrator for phase-referencing to a weak target. We will be given the opportunity to select a calibrator from lots of milli-Jansky sources, one of which may be located at the position closer to the target. With such a smaller separation, high-quality phase-referencing can be achieved. Furthermore, a subsequent more-sophisticated calibration can relocate array's focus to a hypothetical point much closer to the target; a higher quality of phase referencing is available. Our demonstrative observations with strong radio sources have proved the capabilities of BPR in terms of image dynamic ranges and astrometric reproducibility. The image dynamic range on a target has been improved with a factor of about six compared to that of normal phase-referencing; the resultant position difference of target's emission between two epochs was only 62+-50 micro-arcsecond, even with less than 2300-km baselines at 8.4 GHz and fast-switching of a target-calibrator pair of a 2.1-degree separation.Comment: 10 pages, 4 figures, accepted for publication in PAS

Very Long Baseline Array Imaging of Parsec-scale Radio Emissions in Nearby Radio-quiet Narrow-line Seyfert 1 Galaxies

We conducted Very Long Baseline Array (VLBA) observations of seven nearby narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz (18cm) with milli-arcsecond resolution. This is the first systematic very long baseline interferometry (VLBI) study focusing on the central parsec-scale regions of radio-quiet NLS1s. Five of the seven were detected at a brightness temperature of >~5x10^6 K and contain radio cores with high brightness temperatures of >6x10^7 K, indicating a nonthermal process driven by jet-producing central engines as is observed in radio-loud NLS1s and other active galactic nucleus (AGN) classes. VLBA images of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear structures. A large portion of the radio power comes from diffuse emission components that are distributed within the nuclear regions (<~300 pc), which is a common characteristic throughout the observed NLS1s. Jet kinetic powers limited by the Eddington limit may be insufficient to allow the jets escape to kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of <~10^7 M_sun.Comment: 12 pages, 3 figures, 3 tables, accepted for publication in Ap

Atomic scale friction between clean graphite surfaces

We investigate atomic scale friction between clean graphite surfaces by using molecular dynamics. The simulation reproduces atomic scale stick-slip motion and low frictional coefficient, both of which are observed in experiments using frictional force microscope. It is made clear that the microscopic origin of low frictional coefficients of graphite lies on the honeycomb structure in each layer, not only on the weak interlayer interaction as believed so far.Comment: 4 pages, 7 figure

Studies on dose distribution, dynamics of DNA repair proteins and radio-sensitization associated with high LET radiation

学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 上坂 充, 東京大学教授 高橋 浩之, 東京大学教授 鄭 雄一, 東京大学准教授 中島 義和, 東京大学講師 細谷 紀子, 放射線医学総合研究所チームリーダー, 藤森 亮University of Tokyo(東京大学