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排序方式: 共有621条查询结果,搜索用时 15 毫秒
21.
Junya Kojima Masanori Ono Naoaki Kuji Hirotaka Nishi 《International journal of molecular sciences》2022,23(14)
In humans, the placenta provides the only fetomaternal connection and is essential for establishing a pregnancy as well as fetal well-being. Additionally, it allows maternal physiological adaptation and embryonic immunological acceptance, support, and nutrition. The placenta is derived from extra-embryonic tissues that develop rapidly and dynamically in the first weeks of pregnancy. It is primarily composed of trophoblasts that differentiate into villi, stromal cells, macrophages, and fetal endothelial cells (FEC). Placental differentiation may be closely related to perinatal diseases, including fetal growth retardation (FGR) and hypertensive disorders of pregnancy (HDP), and miscarriage. There are limited findings regarding human chorionic villous differentiation and placental development because conducting in vivo studies is extremely difficult. Placental tissue varies widely among species. Thus, experimental animal findings are difficult to apply to humans. Early villous differentiation is difficult to study due to the small tissue size; however, a detailed analysis can potentially elucidate perinatal disease causes or help develop novel therapies. Artificial induction of early villous differentiation using human embryonic stem (ES) cells/induced pluripotent stem (iPS) cells was attempted, producing normally differentiated villi that can be used for interventional/invasive research. Here, we summarized and correlated early villous differentiation findings and discussed clinical diseases. 相似文献
22.
Zijing Wang Fen Wang Angga Hermawan Yusuke Asakura Takuya Hasegawa Hiromu Kumagai Hideki Kato Masato Kakihana Jianfeng Zhu Shu Yin 《材料科学技术学报》2021,73(14):128-138
Acetone,as widely used reagents in industry and laboratories,are extremely harmful to the human.So the detection of acetone gas concentrations and leaks in special environments at room temperature is essential.Herein,the nanocomposite combining SnO-SnO2 (p-n junction) and Ti3C2Tx MXene was successfully synthesized by a one-step hydrothermal method.Because of the existence of a small amount of oxygen during the hydrothermal conditions,part of the p-type SnO was oxidized to n-type SnO2,forming in-situ p-n junctions on the surface of SnO.The hamburger-like SnO-SnO2/Ti3C2Tx sensor exhibited improved acetone gas sensing response of 12.1 (Rg/Ra) at room temperature,which were nearly 11 and 4 times higher than those of pristine Ti3C2Tx and pristine SnO-SnO2,respectively.Moreover,it expressed a short recovery time (9 s) and outstanding reproducibility.Because of the different work functions,the Schottky barrier was formed between the SnO and the Ti3C2Tx nanosheets,acting as a hole accumulation layer (HALs) between Ti3C2Tx and tin oxides.Herein,the sensing mechanism based on the formation of hetero-junctions and high conductivity of the metallic phase of Ti3C2Tx MXene in SnO-SnO2/Ti3C2Tx sensors was discussed in detail. 相似文献
23.
Yuko Habuta Naoaki Narishige Kazu Okumura Naonobu Katada Miki Niwa 《Catalysis Today》2003,78(1-4):131-138
Vanadium oxide spread highly on TiO2 (anatase, A) and SnO2, and rather densely on TiO2 (rutile, R) and ZrO2 to make the monolayer in less than 4–5 V nm−2. Profile of acid site of the monolayer was measured by temperature programmed desorption of ammonia, and its relation with the surface oxidation state was studied. The acid site density was high on the V2O5/TiO2 (A) independent of the degree of oxidation. On the other hand, that of V2O5/TiO2 (R) and V2O5/ZrO2 depended on the oxidation state, and the high value of the concentration was observed on the oxidized one. The strength of acid site generated on the V2O5 monolayer on TiO2 was as high as on the HZSM-5 zeolite. Turnover frequency (TOF) of propane conversion, and product selectivity were measured in propane oxidation. Among tested oxides, the V2O5/TiO2 (A) showed the high TOF and selectivity to form propylene, while those loaded on TiO2 (R) and ZrO2 the small TOF and poor selectivity. Therefore, the reaction profile of activity and selectivity could be related with the extent of spreading and solid acidity. An idea of limit of the acid site density ca. 1.5 nm−2 on the monolayer was elucidated. 相似文献
24.
The behavior of sulfur transformation during rapid hydropyrolysis of coal was investigated using a pressurized, continuous free fall pyrolyzer under the conditions of temperature ranging from 923 to 1123 K and hydrogen pressure up to 5 MPa. The yields of sulfur converted to gas, tar and char were determined, together with the analyses of sulfur form distributions in coals and chars. The results showed that the decomposition of inorganic sulfur species was affected only by the temperature, while the increases in temperature and hydrogen pressure obviously enhanced the removal of organic sulfur from coal. The extent of organic sulfur removal was proportional to the coal conversion, depending on coal type. A significant retention of gaseous sulfur products by the organic matrix of the char was observed during hydropyrolysis of a Chinese coal above 1023 K, even under the pressurized hydrogen atmosphere. The kinetic analysis indicates that the rate of organic sulfur removal from coal was 0.2th-order with respect to the hydrogen pressure, and the activation energy for total sulfur removal and organic sulfur removal is 17-26 and 13-55 kJ/mol, respectively. The low activation energies suggest that the transformation and removal of sulfur from coal might be controlled by the diffusion and/or thermodynamic equilibrium during hydropyrolysis under the pressurized conditions. 相似文献
25.
Tomohiro Toigawa Yasuhiro Tsubata Takeshi Kai Takuya Furuta Yuta Kumagai Tatsuro Matsumura 《溶剂提取与离子交换》2021,39(1):74-89
ABSTRACT Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process. 相似文献
26.
Seiji Kumagai Hirotaka Ishizawa Yuta Aoki Yasuhiro Toida 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2010,156(2):270-277
A molded carbon/silica composite with high micro- and mesoporosity, as well as a high bulk density, was fabricated by activating a disk-molded precursor made from carbonized rice husk (RH) and beet sugar (BS) at 875 °C in CO2. The pore structure of the RH- and BS-based carbon/silica composite (RBC) was analysed in relation to the bulk density. An activation time of 2.0 h provided the largest BET specific surface area (1027 m2/g) and total pore volume (0.68 cm3/g) and a low bulk density (0.54 g/cm3). An RBC that was first activated for 1 h was immersed again in BS syrup and then activated in CO2 for 1 h. This two-step activation process provided both a high bulk density (0.69 g/cm3) and a highly textured structure (BET specific surface area, 943 m2/g; total pore volume, 0.56 cm3/g). The immersion in BS syrup was useful for improving the texture without reducing the bulk density, in comparison to one-step activation for 1.0 h. The suspension of the RBCs was basic because of the residual inorganic compounds of potassium and calcium. However, the basicity of the suspension was alleviated by washing the RBCs with water. 相似文献
27.
28.
Kumagai S. Yoshimura N. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2001,8(4):673-678
Tracking and erosion behaviors of high temperature vulcanized (HTV)-silicone rubber (SIR) of 0.5 to 6.0 mm thicknesses were investigated in order to obtain the optimum thickness for enhancing tracking and erosion resistance under various leakage current levels. Under low leakage current, thinner samples showed a higher tracking and erosion resistance, while under medium and high leakage current, thicker samples showed better resistance to these behaviors. The optimum thickness to prolong the time to tracking and erosion failure appeared in the range of 1.0 to 3.0 mm thickness. The content of an initial low molecular weight (LMW) silicone fluid was shown to be closely related to the development of leakage current and high temperature thermal spots. The results indicate that the sample thickness is crucial to the ability of HTV-SIR to withstand a large number of high temperature thermal spots under condition of high level leakage current 相似文献
29.
Viliame Savou Guido Grause Shogo Kumagai Yuko Saito Tomohito Kameda Toshiaki Yoshioka 《能源学会志》2019,92(4):1149-1157
Pyrolysis is a promising technique for the recovery of useful gas, tar, and solid products from biomass waste. However, the low tar yields obtained from lignocellulosic biomass are a significant drawback. To enhance tar yields, sugarcane bagasse, which is the most abundant agricultural waste in Fiji, was pretreated at ambient temperature and atmospheric pressure using various sulfuric acid (H2SO4) concentrations. Here, the ether bonds of cellulose, hemicellulose, and lignin were partially hydrolyzed. The pretreated samples were then pyrolyzed at 500 °C, and it was confirmed that H2SO4-pretreatment disrupted the bagasse cell structure, with the thermogravimetry and differential thermogravimetry results confirming that decomposition occurred at lower temperatures after pretreatment. In addition, tar yields were significantly enhanced from 5.6 wt% to 13.4 wt% for the untreated and 3 M H2SO4-pretreated samples respectively. The main components detected in this tar product were levoglucosan, andcellulose-and hemicellulose-derived products, whose proportions were increased following pretreatment. Thus, our work demonstrates that dilute acid pretreatment enhances tar production from sugarcane bagasse due to the production of shorter chain components via the partial hydrolysis of ether bonds. 相似文献
30.
Yoshinao Mishima Naoaki Yoshida Kiyohito Ishida Takaharu Iwadachi Ikuo Ohnuma Kenzo Munakata Munenori Uchida 《Fusion Engineering and Design》2007,82(1):91-97
Beryllides have remarkable characteristics besides their low density, such as high radiation resistance, high chemical stability, low hydrogen isotope retention and good high temperature mechanical strength especially for fusion applications. In order to have a practical usage for industrial applications, it is important to compile a set of quantitative data on such properties. It is also important to develop fabrication and processing paths to assure the processing of inherently brittle beryllides.The characterization and manufacturing technologies development have been carried out mainly on the Be12Ti interemetallic compounds at the Be-rich side of the Be-Ti binary system. In the present paper, up-dated results on several properties are described for the compound fabricated by hot isostatic pressing (HIP) and ingot metallurgy. Mechanical properties of the compounds having a duplex microstructure with neighboring phases are evaluated by compressive tests from room temperature to 1273 K. Radiation damage of the compound is preliminary studied by charged particle irradiation. Oxidation in air and the interaction with water vapor are evaluated. Thermal desorption of the deuterium is examined by using transmission electron microscopy (TEM) and thermal desorption spectrometry (TDS). Through these evaluations it seems that Be12Ti is superior as neutron multiplier with respect to pure Be metal. 相似文献