Retraction     

Fukuhara A  Matsuda M  Nishizawa M  Segawa K  Tanaka M  Kishimoto K  Matsuki Y  Murakami M  Ichisaka T  Murakami H  Watanabe E  Takagi T  Akiyoshi M  Ohtsubo T  Kihara S  Yamashita S  Makishima M  Funahashi T  Yamanaka S  Hiramatsu R  Matsuzawa Y  Shimomura I 《Science (New York, N.Y.)》2007,318(5850):565

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Trampoline effect in extreme ground motion     

Aoi S  Kunugi T  Fujiwara H 《Science (New York, N.Y.)》2008,322(5902):727-730

In earthquake hazard assessment studies, the focus is usually on horizontal ground motion. However, records from the 14 June 2008 Iwate-Miyagi earthquake in Japan, a crustal event with a moment magnitude of 6.9, revealed an unprecedented vertical surface acceleration of nearly four times gravity, more than twice its horizontal counterpart. The vertical acceleration was distinctly asymmetric; the waveform envelope was about 1.6 times as large in the upward direction as in the downward direction, which is not explained by existing models of the soil response. We present a simple model of a mass bouncing on a trampoline to account for this asymmetry and the large vertical amplitude. The finding of a hitherto-unknown mode of strong ground motion may prompt major progress in near-source shaking assessments.  相似文献   

Leiomodin is an actin filament nucleator in muscle cells     

Chereau D  Boczkowska M  Skwarek-Maruszewska A  Fujiwara I  Hayes DB  Rebowski G  Lappalainen P  Pollard TD  Dominguez R 《Science (New York, N.Y.)》2008,320(5873):239-243

Initiation of actin polymerization in cells requires nucleation factors. Here we describe an actin-binding protein, leiomodin, that acted as a strong filament nucleator in muscle cells. Leiomodin shared two actin-binding sites with the filament pointed end-capping protein tropomodulin: a flexible N-terminal region and a leucine-rich repeat domain. Leiomodin also contained a C-terminal extension of 150 residues. The smallest fragment with strong nucleation activity included the leucine-rich repeat and C-terminal extension. The N-terminal region enhanced the nucleation activity threefold and recruited tropomyosin, which weakly stimulated nucleation and mediated localization of leiomodin to the middle of muscle sarcomeres. Knocking down leiomodin severely compromised sarcomere assembly in cultured muscle cells, which suggests a role for leiomodin in the nucleation of tropomyosin-decorated filaments in muscles.  相似文献   

Molecular structures of gellan gum imaged with atomic force microscopy in relation to the rheological behavior in aqueous systems in the presence or absence of various cations     

Funami T  Noda S  Nakauma M  Ishihara S  Takahashi R  Al-Assaf S  Ikeda S  Nishinari K  Phillips GO 《Journal of agricultural and food chemistry》2008,56(18):8609-8618

Aqueous solutions of gellan gum with comparable molecular masses but with different acyl contents were investigated by atomic force microscopy and rheological measurements in the presence or absence of various cations. For a high-acyl sample, no continuous network structures were identified microscopically, except in the presence of Ca (2+), where structural inhomogeneity was the highest in terms of the height distribution of molecular assemblies. Rheological thermal hysteresis between sol-gel transitions was detected in the presence of K (+) and Ca (2+), particularly Ca (2+). The storage modulus at 20 degrees C was larger in the order Na (+) < Ca (2+) < K (+). For a low-acyl sample, continuous network structures were identified in the presence of each cation, involving greater thermal hysteresis than the corresponding data for the high-acyl sample. Structural homogeneity was the highest in the presence of K (+). Thermal hysteresis and elasticity of the system were discussed in terms of continuousness and homogeneity of network structures.  相似文献   

Soil microorganisms have a threshold concentration of glucose to increase the ratio of respiration to assimilation     

Kozue SAWADA  Shinya FUNAKAWA  Takashi KOSAKI 《Soil Science and Plant Nutrition》2008,54(2):216-223

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Seasonal changes of nitrate concentrations in baseflow headwaters of coniferous forests in Japan: A significant indicator for N saturation     

Zhao Zhang  Takehiko Fukushima  Peijun Shi  Fulu Tao  Yuichi Onda  Takashi Gomi  Shigeru Mizugaki  Yuko Asano  Ken'ichirou Kosugi  Shinya Hiramatsu  Hikaru Kitahara  Koichiro Kuraji  Tomomi Terajima  Kazuo Matsushige 《CATENA》2008

Understanding the seasonal and regional patterns of nitrogen (N) components in the headwaters of forested watersheds is important for forests management. Here, we investigated the NO₃-N concentration and its seasonal variations in the baseflow headwaters in Japanese coniferous forests with different N saturation status in five regions (i.e., Nagano, Tokyo, Aichi, Kochi and Mie). We found that the ratios of NO₃-N to DON were significantly higher in the N-saturated regions including Nagano (14.1 ± 2.2) and Tokyo (16.5 ± 4.1), compared with the regions, which didn't experience N saturation including Aichi (1.4 ± 0.2), Kochi (5.1 ± 1.8), and Mie (2.2 ± 0.5). In comparison with the regions without experiencing N saturation, the relatively higher NO₃-N concentration, as well as its contrastive variation between growing season and dormant season, was also characteristic of the seasonal NO₃-N concentration in the N-saturated regions. Our findings have indicated that NO₃-N concentration, its seasonal variations, and the ratio of NO₃-N to DON, are the better and applicable indicators for evaluating N saturation status in Japanese coniferous forests.  相似文献   

Isolated chloroplast division machinery can actively constrict after stretching     

Yoshida Y  Kuroiwa H  Misumi O  Nishida K  Yagisawa F  Fujiwara T  Nanamiya H  Kawamura F  Kuroiwa T 《Science (New York, N.Y.)》2006,313(5792):1435-1438

Chloroplast division involves plastid-dividing, dynamin, and FtsZ (PDF) rings. We isolated intact supertwisted (or spiral) and circular PDF machineries from chloroplasts of the red alga Cyanidioschyzon merolae. After individual intact PDF machineries were stretched to four times their original lengths with optical tweezers, they spontaneously returned to their original sizes. Dynamin-released PDF machineries did not retain the spiral structure and could not be stretched. Thus, dynamin may generate the motive force for contraction by filament sliding in dividing chloroplasts, in addition to pinching-off the membranes.  相似文献   

Pole and global shape of 25143 Itokawa     

Demura H  Kobayashi S  Nemoto E  Matsumoto N  Furuya M  Yukishita A  Muranaka N  Morita H  Shirakawa K  Maruya M  Ohyama H  Uo M  Kubota T  Hashimoto T  Kawaguchi J  Fujiwara A  Saito J  Sasaki S  Miyamoto H  Hirata N 《Science (New York, N.Y.)》2006,312(5778):1347-1349

The locations of the pole and rotation axis of asteroid 25143 Itokawa were derived from Asteroid Multiband Imaging Camera data on the Hayabusa spacecraft. The retrograde pole orientation had a right ascension of 90.53 degrees and a declination of -66.30 degrees (52000 equinox) or equivalently 128.5 degrees and -89.66 degrees in ecliptic coordinates with a 3.9 degrees margin of error. The surface area is 0.393 square kilometers, the volume is 0.018378 cubic kilometers with a 5% margin of error, and the three axis lengths are 535 meters by 294 meters by 209 meters. The global Itokawa revealed a boomerang-shaped appearance composed of two distinct parts with partly faceted regions and a constricted ring structure.  相似文献   

Relationship between crack propagation and the stress intensity factor in cutting parallel to the grain of hinoki (<Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis>)     

Masumi Minagawa  Yosuke Matsuda  Yuko Fujiwara  Yoshihisa Fujii 《Journal of Wood Science》2018,64(6):758-766

The method of digital image correlation (DIC) was applied to the digital image of orthogonal cutting parallel to the grain of hinoki, and the strain distribution near the cutting edge was evaluated. The wood fracture associated with chip generation was considered as mode I fracture, and the stress intensity factor K_I for fracture mode I was calculated from the strain distribution according to the theory of linear elastic fracture mechanics for the anisotropic material. The calculated K_I increased prior to crack propagation and decreased just after the crack propagation. The change in K_I before and after crack propagation, ΔK_I, decreased in accordance with the crack propagation length, although the variance in ΔK_I should depend on the relationships between the resolution of DIC method and the dimensions of cellular structure. The calculated K_I in this study was almost on the same order as reported in the literatures. It was also revealed, for the case of chip generation Type 0 or I, the stress intensity factor for fracture mode II could be negligible due to the higher longitudinal elastic properties of wood in the tool feed direction than the one radial ones, and the mode I fracture was dominant.  相似文献