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61.
In monocarpic plants, stem cells are fated to die. However, the potential mechanism of stem cell death has remained elusive. Here, we reveal that the levels of two forms of reactive oxygen species (ROS), superoxide anion free radical () and hydrogen peroxide (H2O2), show dynamic changes in the shoot apex during the plant life cycle of Arabidopsis thaliana. We found that the level of decreased and disappeared at four weeks after bolting (WAB), while H2O2 appeared at 3 WAB and showed a burst at 5 WAB. The timing of dynamic changes in and H2O2 was delayed for approximately three weeks in clv3-2, which has a longer lifespan. Moreover, exogenous application of H2O2 inhibited the expression of the stem cell determinant WUSCHEL (WUS) and promoted the expression of the developmentally programmed cell death (dPCD) marker gene ORESARA 1 (ORE1). These results indicate that H2O2 triggers an important signal inducing dPCD in stem cells. Given that plays roles in maintaining WUS expression and stem cell activity, we speculate that the dynamic shift from to H2O2 in the shoot apex results in stem cell death. Our findings provide novel insights for understanding ROS-mediated regulation during plant stem cell death. 相似文献
62.
Masayuki Nagai Tatsuya Saeki Tadashi Nishino 《Journal of the American Ceramic Society》1990,73(5):1456-1460
Hydroxyapatite and Cl− -containing hydroxyapatite powders are prepared and characterized. Reversible substitution of CO2- 3 for OH− at the surface is presumed to be responsible for the sensor function. The role of Cl− , which is necessary to realize the sensor function and is incorporated during soaking treatment, is considered as follows. It may reduce the strain caused by the incorporation of CO2- 3 (which is larger than OH− ), and, hence, promote the reversible substitution reaction. This behavior is presumed because Cl− -containing hydroxyapatite samples exhibit sensor characteristics typical of CO2 without any treatment. 相似文献
63.
Ken‐Ichiro Ishimori Tsuyoshi Yaita Takaumi Kimura Takashi Yamada Satoshi Shinoda 《溶剂提取与离子交换》2013,31(4):489-500
The extraction equilibria of Am(III) and Eu(III) by using a tripodal ligand, tris(2‐pyridylmethyl)amine (tpa), with various lipophilic anions have been investigated. The extractability of both Am(III) and Eu(III) was increased by the combination of tpa and counteranions due to a synergistic effect. The separation factors between Am(III) and Eu(III) were also increased from 7.6 to 49 by the combination of counteranions and organic solvents. The extraction equilibria of Am(III) and Eu(III) with tpa in 1,2‐dichloroethane were determined by slope analysis. It was found that three anions and one molecule of the ligand coordinated to Am(III) and Eu(III) was extracted regardless of the anions. 相似文献
64.
Carbon Nanotubes: Simple Salt‐Coordinated n‐Type Nanocarbon Materials Stable in Air (Adv. Funct. Mater. 18/2016)
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65.
Kazuya Ogawa Naoyuki Makiuchi Yoshiaki Kobuke 《International journal of molecular sciences》2013,14(1):322-331
A conjugated-bisimidazolylporphyrin bridged by bis(ethynylfluorene) was synthesized and organized into linear polymer through self-coordination having mean molecular weights, Mw and Mn, of ~2.1 × 105 Da and ~1.6 × 105 Da, respectively. A large two-photon absorption cross section value of 3.4 × 105 GM (per dimer unit) was observed. This value was comparable to that of the previously reported self-assembled linear polymer consisting of butadiyne-bridged imidazolylporphyrins. The two-photon absorption properties could be controlled by tuning the wavelength and absorption intensity of the one-photon absorption. 相似文献
66.
Hirokazu Ozaki Atsushi Kara Zixue Cheng 《Quality and Reliability Engineering International》2011,27(7):895-903
In this paper, we investigate service‐level assurance in high‐availability multi‐unit systems using the M‐for‐N backup scheme. M‐for‐N shared protection (backup) systems with priority control (i.e. prioritized protection switching and prioritized re‐housing of repaired units) can be applied to actual telecommunication devices that are subject to service‐level agreement (SLA) involving reliability measures. A priority level is assigned to each end user in such a system and the switching and unit re‐housing process is subject to the priority. The main contribution of this paper is to give a practical computation method of the user‐perceived availability under the priority control. Our case studies for real telecommunication systems reveal the effect of priority control on the user‐perceived availability. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
67.
N. Fujita K. IshiiH. Ogawa 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(9):1023-1025
We have developed the two-dimensional mapping technique with in-air-PIXE (2D-PIXE) using a metal capillary as a guide to extract ion beam to air. The metal capillary is the conventional injection needle with a 200 μm inside diameter. For the target which is the character made of the copper wires on aluminum basement, 2D-PIXE measurements were performed by irradiating 3 MeV proton beam. As a result, the character was tend to be restored clearly by this method. We discuss about the result of the two-dimensional map from a viewpoint of the signal-to-noise ratio and the resolution. This technique is expected to be applicable to various fields such as biology, nano-technology, archeology and so on. 相似文献
68.
Theories of the biaxial tensile properties, the uniaxial tensile properties, and the shear-deformation properties of plain-weave fabrics are presented in a general form, a simplified stereo-model of the structure of plain-weave fabrics being used throughout these theories. In the first part of this series, the biaxial tensile-deformation theory is presented with the aid of the model, and the forces required to stretch the fabric along the warp and weft directions at the same time are theoretically calculated from the properties of yarns and from the structure of the fabrics. In this biaxial theory, both warp and weft yarns are assumed to be perfectly flexible, and the forces caused by yarn-bending are ignored. The compressibility of the yarn under the action of a lateral compressive force is also introduced into the theory, and it is shown that the compressive properties of yarns have a great influence on the tensile properties of the fabrics. 相似文献
69.
A mechanical model of the 2/2-twill weave is presented in order to investigate the tensile properties of this weave under biaxial extension. The theory predicts that the compressional deformations of the warp and the weft at their cross-over point produce a superior effect on the tensile properties of the weave, especially in the relatively small-extension state. Experimental investigation to examine the accuracy of this theory is also reported, and good agreement between the theory and the experimental result is demonstrated. 相似文献
70.
Hiroaki Takeda Takeshi Shimada Yoshiaki Katsuyama Tadashi Shiosaki 《Journal of Electroceramics》2009,22(1-3):263-269
The electric properties of BaTiO3–(Bi1/2Na1/2)TiO3 (BT–BNT) solid solution ceramics were studied as a lead-free PTCR (positive temperature coefficient of resistivity) thermistor material usable over 130°C. For determining the maximum switching temperature T s, the phase diagram of BT–BNT binary system was clarified. Two semiconductorization processes and their electric properties are described. The lanthanum(La)-doped BBNT ceramics sintered in air still showed dielectric behaviors, but the niobium(Nb)-doped ones had a low resistivity at room temperature, ρ RT, on the order of 103 Ωcm and showed a PTC behavior. Sintering under a low O2 atmosphere produces BT–BNT ceramics with less than 102 Ωcm compared to those prepared in air. Our current research produced the BBNT ceramics with T s values around 210°C by increasing the (Bi1/2Na1/2) content in the ceramics. 相似文献