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21.
Bacteria appeared early in the evolution of cellular life on planet Earth, and therefore the universally essential genes or biological pathways found across bacterial domains may represent fundamental genetic or cellular systems used in early life. The essential genes and the minimal gene set required to support bacterial life have recently been experimentally and computationally identified. It is, however,still hard to estimate the ancient genes present in primitive cells compared to the essential genes in contemporary bacteria, because we do not know how ancestral primitive cells lived and proliferated, and therefore cannot directly evaluate the essentiality of the genes in ancestral primitive cells. The cell wall is normally essential for bacterial proliferation and cellular division of walled bacterial cells is normally highly controlled by the essential FtsZ cell division machinery. But, bacteria are capable of reverting to their cell wall deficient ancestral form, called the "L-form". Unlike "normal" cells, L-forms divide by a simple physical mechanism based on the effects of membrane dynamics, suggesting a mode of primitive proliferation before the appearance of the cell wall. In this review, we summarize the experimental and computational investigations of minimal gene sets and discuss the minimal cellular modules required to support the proliferation of primitive cells, based on L-form proliferation. 相似文献
22.
Solar Physics - From a morphological study of the evolution of six active regions, we found two types of processes for the development of magnetic shear configurations between sunspots: (A)... 相似文献
23.
We present a new method for the automatic identification and classification of dynamic Hα dark features found in time series of full-disk solar images at three Hα wavelengths (center, and ± 0.8 Å). The simultaneous Hα observations are obtained by the multi-channel Flare Monitoring Telescope (FMT) at Hida Observatory. The program was developed in order to replace the present visual detection and classification of the phenomena. Usually, an obvious dark feature found in the Hα ?0.8 Å observations probably corresponds to some phenomenon such as a surge or chromospheric network enhancement, or filament activity. Thus, one of our aims in this program is to distinguish each phenomenon by its own properties and key parameters. We optimized the threshold values of the key parameters such as the area and darkness of the transiently darkening features in Hα ?0.8 Å so that the computer can reasonably identify surges and filament activations. In comparison, for a 7-day observation period, the number of dark events detected by the program contains 89% of the events recognized visually. However, 10 times more events are detected automatically. The missing events are mainly caused by the deletion of data with poor visibility. It is found that the dark events can be identified with more precise starting and ending times by a machine than by a human. Some statistical studies of surges or other activities can be carried out based on the computer-produced database. With some modifications the program can be applied to monitor real-time dynamic features on disk, including flare ribbons. 相似文献
24.
25.
Slitless flash spectrograms in heights below 8000 km above the solar limb were obtained by the University of Kyoto Expedition at Atar, Mauritania. The integrated intensities of Fexiv
5303, Fex
6374, Fexi
7892, and the continuum are measured as a function of height above the solar limb at eleven points (P.A. = 284–300°) around the third contact point. It is found that a significant amount of the emission in Fex
6374 originates in chromospheric levels well below 8000 km. This implies that the interspicular region of the chromosphere is occupied by coronal material. The average values of the electron temperature and the electron density in the interspicular region are derived from the Fex
6374 and the Fexi
7892 intensities on the assumption of spherical symmetry: T
e = 0.9–1.1 × 106 K and N
e = 9–10 × 108 cm–3. The intensity variations of the coronal lines and the continuum with position angle are also studied. Strong correlations between Fexiv
5303 and the continuum and between Fex
6374 and Fexi
7892 are found. From the Fex
6374 intensities it is inferred that there is a density fluctuation in the innermost corona by at least a factor of two.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 271. 相似文献
26.
Yoshinori Suematsu Sumisaburo Saito Yasuhiro Funakoshi Hiroki Kurokawa 《Solar physics》1988,116(2):285-290
A coronal condensation was observed simultaneously with Fexiv 5303, Fex 6374, Fe xi 7892, and H filtergraphs. The size and shape of the condensation in 5303 are different from those in other filtergrams. H filtergrams taken around the eclipse time show that a small transient prominence exists in close proximity to the condensation core and behaves like a post-flare loop system, though the appearance is quite different and no flare-report exists. A small-scale energetic phenomenon seems to have occurred at the top of magnetic loops.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 285. 相似文献
27.
A channelised long run-out debris slide triggered by the Noto Hanto Earthquake in 2007, Japan 总被引：2，自引：1，他引：1
Yasuhiko Okada Hirotaka Ochiai Ushio Kurokawa Yasuhiro Ogawa Shiho Asano 《Landslides》2008,5(2):235-239
A strong earthquake (M
J 6.9, M
W 6.6–6.7) at about 11 km depth hit the western shore of the Noto Peninsula on Honshu, Japan, at about 00:42 coordinated universal
time (9:42 a.m. local time) on 25 March 2007 (the Noto Hanto Earthquake in 2007). The earthquake triggered only 61 landslides, with most
traveling short distances. It caused one long run-out landslide in the Nakanoya district of Monzen town, Wajima city, Ishikawa
Prefecture, when a portion of a deep-seated landslide transformed into a moderate debris slide down a channel. The rock slide
occurred on a south-facing convex-shaped slope on a small spur where earthquake ground shaking likely was strongly amplified
by topography. A portion of the rock slide reached a small channel floored by materials containing abundant groundwater. Constant-volume
box-shear tests on normally consolidated saturated specimens revealed that the apparent angle of internal friction of the
channel-floor material was 33–36° at 10-mm shear displacement and did not show much decrease in effective normal stress during
shearing. In situ rock-sliding testing on the exposed channel materials showed a low kinetic-friction angle of about 21°.
We suggest that an unsaturated portion of the rock slide slid down the channel, with sliding between the rock-slide mass and
the channel floor. Because the slope angle of the travel path nearly equaled the kinetic-friction angle, the unsaturated rock
slide mass may have traveled at a moderately slow speed, or it might have decelerated and accelerated. Slow speed is supported
by accounts from local residents that suggest movement of debris continued for 3 days after the main shock. 相似文献
28.
Yoichi Okura Hikaru Kitahara Akiko Kawanami Ushio Kurokawa 《Engineering Geology》2003,67(3-4):243-254
The authors investigated factors affecting the travel distance of a surface failure and developed a simple model for estimating the distance based on soil properties and topographic factor. The authors conducted field surveys and various soil tests for a number of surface failures that occurred during torrential rain at the end of August 1998 in southern Fukushima Prefecture, Japan. The authors studied the effects of various factors such as landslide volume, pore-water pressure, slope inclination, and the internal friction near the slip surfaces on the travel distances. The analyses showed no clear relationship between landslide volume and equivalent coefficient of friction, which was likely attributable to the very small range of volume compared to other studies on catastrophic landslides. The effect of excess pore-water pressure was likely negligible because undrained conditions were not to be maintained at the shallow flow depths. A positive correlation was shown between slope inclination and equivalent coefficient of friction. This correlation was attributable to two factors, one was positive correlation between the internal friction on the slip surface and slope inclination, and the other was the kinetic energy dissipation of moving mass that occurred at the inclination changing point between a slope and a sedimentary flat surface. The authors then developed a predictive model for critical flow inclination of landslide by installing the factors of soil properties and slope inclination factors. The model predicted equivalent coefficient of frictions, which were very similar to the observed values, thus verifying the effectiveness of the model. 相似文献
29.
The evolutional characteristics of the red asymmetry of H flare line profiles were studied by means of a quantitative analysis of H flare spectra obtained with the Domeless Solar Telescope at Hida Observatory. Red-shifted emission streaks of H line are found at the initial phase of almost all flares which occur near the disk center, and are considered to be substantial features of the red asymmetry. It is found that a downward motion in the flare chromospheric region is the cause of the red-shifted emission streak. The downward motion abruptly increases at the onset of a flare, attains its maximum velocity of about 40 to 100 km s-1 shortly before the impulsive peak of the microwave burst, and rapidly decreases before the intensity of H line reaches its maximum. Referring to the numerical simulations made by Livshits et al. (1981) and Somov et al. (1982), we conclude that the conspicuous red-asymmetry or the red-shifted emission streak of H line is due to the downward motion of the compressed chromospheric flare region produced by the impulsive heating by energetic electron beam or thermal conduction.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 258. 相似文献
30.
Morphological and evolutional features of Ellerman bombs were studied with H filtergrams of two active regions very close to the solar limb. We quantitatively determined the elongated or spike-like shape of the bomb. The mean apparent length of 174 bombs is 1.1 arc sec, while 80% of 204 bombs have a diameter of less than 0.6 arc sec. The mean lifetime of 77 bombs is about 12 min at H - 1.2 Å. The first maximum brightness of a typical bomb is attained, on average in about 2 min. Bombs grow longer in the first brightening phase and their mean upward velocity explains the blue asymmetry of H emission profiles of moustaches. 相似文献