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Dosimeter properties of MgO transparent ceramic doped with c

RADIATION MEASUREMENTS 2016年第0期92卷 93-98页

作者： Kato, Takumi Okada, Go Yanagida, Takayuki Nara Inst Sci & Technol NAIST 8916-5Takayama Cho Ikoma Nara 6300192 Japan

We have investigated the photoluminescence (PL), scintillation and thermally-stimulated luminescence (TSL) dosimeter properties of MgO ceramic doped with c ions (0.001, 0.01 and 0.1%). The samples were synthesized by a Spark Plasma Sintering (SPS) technique. The PL emission peaks appeared around 400 and 750 nm in all the samples. The PL decay time constants at 400 nm were 10 and 100 ns which were on the typical order of F+ center in the undoped MgO. The scintillation emission peaks were detected at 330, 400 and 750 nm under X-ray irradiation. The TSL glow curves showed the 250 degrees c peak in 0.1% c doped sample. The TSL response was confirmed to be linear to the irradiation dose over the dose range from 0.1 to 1000 mGy. As a result, the sensitivity of MgO was improved by c-doping. (c) 2016 Elsevier Ltd. All rights reserved.

关键词： Transparent ceramic MgO c Dosimeter TSL

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Ba, Si, U, Al, Sc, La, Th, c and ¹³c/¹²c in a sediment core in the western subarctic Pacific as proxies of past biological production

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MARINE cHEMISTRY 2007年第3-4期106卷 442-455页

作者： Shigemitsu, Masahito Narita, Hisashi Watanabe, Yutaka W. Harada, Naomi Tsunogai, Shizuo Hokkaido Univ Grad Sch Environm Sci Sapporo Hokkaido 0600810 Japan Tokai Univ Sch Marine Sci & Technol Shizuoka 4248610 Japan Japan Agcy Marine Earth Sci & Technol Inst Observat Res Global Change Yokosuka Kanagawa 2370061 Japan

A sediment core covering the last 145 kyrs was collected in the western subarctic Pacific (WSAP), and analyzed for Ba, U, Al, Sc, La, Yb, Th, biogenic opal (Opal) and organic carbon (c-org) as well as its isotopic ratio (delta(13) c). This study examined the change of past biological production in WSAP with multiple proxies, together with understanding the relation between Loess from the Asian continent and the biological production. The Loess content was estimated from the metal components, Al, Sc, La, Yb and Th. In this high latitude core (50 degrees N), the Loess content was generally high during the glacial periods, but it was also high even in some interglacial periods. The excess amount of Ba relative to the detrital material composition, Ba-ex, showed the best correlation with the Vostok delta D (r= 0.72, p < 0.001), indicating that the biological production was lower in the glacial periods than in the interglacials. This corroborates the pervasive correlation between Ba-ex in the polar region, WSAP and the Antarctic Sea, and Antarctic temperature, combined with previous research. This correlation might be explained by the stratification caused by cooling. In addition, the time variations of Ba-ex in WSAP were similar to those of Ba-ex in the Okhotsk Sea and of other proxies (c-org, and Opal) in both the Okhotsk and the Bering Sea, indicating the spatial homogeneity of Ba-ex in WSAP including proximal marginal seas. The Opal content was more weakly correlated with the Vostok delta D (r= 0.46, p < 0.001) than Ba-ex, reflecting that Opal in WSAP including proximal marginal seas was spatially heterogeneous compared to Ba-ex. While both the c-org content and U-ex, the excess amount of U relative to the detritus composition, were not positively correlated with the Vostok delta D, they behaved similarly in the sediments. The positive correlation between delta c-13 and the Vostok delta D (r = 0.42, p < 0.001), between 613 c and Ba,x (r= 0.60, p < 0.00 1) and between

关键词： Ba opal c c-13/c-12 U eolian dust sediment North Pacific

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Mechanical property and toughening mechanism of 2.5D c/c-Sic composites with high textured pyrocarbon interface

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cERAMIcS INTERNATIONAL 2021年第20期47卷 29183-29190页

作者： Xu, Jing Guo, Lingjun Wang, Hanhui Li, Kaijiao Wang, Tiyuan Li, Wei Northwestern Polytech Univ Carbon Carbon Composites Res Ctr State Key Lab Solidificat Proc Xian 710072 Shaanxi Peoples R China

The application of c/c-Sic composites remains a challenge because of the poor mechanical properties induced by the liquid silicon infiltration method. In this study, a thick high textured pyrolytic carbon (HT Pyc) interface manufactured by chemical vapor infiltration (cVI) was used to protect the carbon fibers and improve the flexural properties. The microstructure of HT Pyc, its flexural properties, and its associated strengthening and toughening mechanisms were analyzed on the c/c-Sic composites. The results showed that the bending strength of the c/cSic composites was 344.74 MPa, which is nearly 31.82% higher than that of c/c composites. The fracture mode transformed from brittle fracture to pseudoplastic fracture owing to the addition of Sic, and the c/c-Sic composites maintained a better toughness compared to c/c composites. Multiple mechanisms of strength and toughness improvement were found to be responsible for the excellent performance of the c/c-Sic composites. The HT Pyc interface played a critical role in the excellent flexural properties. The strong bonding among the carbon layers and high interfacial strength between the fiber and HT Pyc led to the increase of strength. Besides, the improvement in toughness was attributed to the multiple effects of the carbon-layers deformation, cracks deflection and propagation caused by the bridging areas, sublayers, nano-and micro-scale cracks.

关键词： c c-Sic composites High textured pyrocarbon interface Morphology Flexural property

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Microstructure and mechanical properties of c/Sic-niobium alloy (c103) joint brazed with TicuAg alloy for aerospace applications

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cERAMIcS INTERNATIONAL 2023年第17期49卷 29265-29273页

作者： Kamal, Anurag Shukla, Anoop Kumar Shinde, Vijay M. Rajasekhar, Buragadda, V Indian Inst Technol BHU Dept Chem Engn Varanasi 221005 India Indian Space Res Org ISRO Ceram Matrix Prod Div ASCG PCM Vikram Sarabhai Space Ctr Thiruvananthapuram 695022 India ISRO Vikram Sarabhai Space Ctr Special Met Facil MMG MME Thiruvananthapuram 695022 India

In this study, niobium-based alloy c103 is joined to carbon fibre-reinforced Sic (c/Sic) composite utilising commercially available Ticusil & REG;and cusil & REG;alloy braze filler material. Various characterisation techniques are employed to investigate the interfacial microstructures and evolution mechanism of c/Sic-c103 junctions. Lap shear strength (LSS) is used to evaluate the mechanical performance of the brazed joints. The results show that adding Ti promotes the growth of "nails", a phenomenon favourable for robust joint quality. However, high Ti content deteriorates the bond strength due to the formation of significant brittle intermetallic phases, causing premature delamination of the joints. The response surface methodology (RSM) is employed to examine the interactions among various operating parameters. To attain the high LSS value, the high temperature, intermediate reaction time, and low cooling rate are necessary for a Ticusil-based joint, whereas high temperature, low reaction time, and increased cooling rate are preferred for a cusil-based joint.

关键词： A Joining B composites c Mechanical properties E Engine components Structural applications D Sic

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A mechanism underlying stimulation and inhibition of protein kinase c by lyso-Pc: A role of membrane physical state

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Science china(Life Sciences) 1998年第6期41卷 584-591页

作者：潘最陈建文 1. State Key Laboratory of Biomacromolecules Institute of Biophysics Chinese Academy of Sciences 100101 Beijing China

Lysophosphatidylcholine (lyso Pc) biphasically regulates the diacylglycerol induced activation of protein kinase c (PKc). In common parlance, lyso Pc stimulates PKc at low concentrations, but, conversely, inhibits it at high concentrations. The activity of purified PKc from rat brains was measured in the vesicles made up of dipalmitoylphosphatidylserine (DPPS), 1,2 sn diolein (DOG) and different molar ratios of 1 palmitoyl sn glycerol 3 phosphoryl choline (c16:0 lyso Pc). The effect, i.e. stimulation or inhibition on PKc by c16:0 lyso Pc, depends on DPPS and DOG concentrations as well as its own concentration. When the concentration of DOG is stable, this c16:0 lyso Pc action depends on c16:0 lyso Pc/DPPS molar ratio. Differential scanning calorimetry (DSc), two fluorescence probes and light scattering were used to analyze the physical characteristics of membrane, including thermotropic phase behavior, the turbidity, the lipid molecular acyl chains packing and the head group spacing. The more adulteration of c16:0 lyso Pc in liposome bilayer membrane, the looser acyl chains pack, and the broader head group spacing. DSc results show that there are two immiscible lipid areas in the membrane: c16:0 lyso Pc rich area and c16:0 lyso Pc poor area. When c16:0 lyso Pc/DPPS molar ratio was 0 234, the two areas had the broadest boundary and the activation of PKc was the highest. When the ratio was over 0 434, the phase transition of DPPS disappeared; micelle tended to substitute the structure of bilayer; the activity of PKc was inhibited completely. DOG can stabilize the bilayer structure of membrane, so the c16:0 lyso Pc/DPPS molar ratios to inhibit PKc in lipid mixture with DOG are higher than that without DOG. The ability of c16:0 lyso Pc to change the physical properties and the structure of membrane plays an important role in its effect on PKc activation.

关键词： protein kinases c lysophosphatidylcholine diolein differential scanning calorimetry physical properties of membrane.

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Tribological behavior and wear mechanism of c/c-Sic brake discs based on third-body layer

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INTERNATIONAL JOURNAL OF APPLIED cERAMIc TEcHNOLOGY 2023年第2期20卷 1310-1326页

作者： Hui, Yang Liu, Guimin Shi, Ruidong Zhang, Yong Yan, Tao Acad Army Armored Forces Dept Equipment Maintenance & Remfg Engn Beijing 100072 Peoples R China

c/c-Sic composites are promising candidates for heavy-duty tracked vehicle brake discs. A third-body layer (TBL) can be formed on the surface of c/c-Sic self-mated brake discs, which has an important impact on tribological behavior and wear mechanism of brake discs. Herein, the formation conditions and evolution process of TBL and its effect on friction and wear properties were investigated. An appropriate braking pressure and speed (P and V) are beneficial to the cutting of asperities and refinement of wear debris on the contact surface, which are preconditions for the formation of original TBL. The original TBL can be formed under the P center dot V of 12, 15, and 16, which effectively improve braking stability and reduce the wear rate. During the continuous braking process, the original TBL undergoes growth, stabilization, destruction, and regeneration. Under the frictional heat and compressive stress, wear debris gradually evolves into a uniform and dense TBL. The average coefficient of friction and wear rate reach to the lowest value of .446 and 38.5 x 10(-3) cm(3)/MJ, respectively. A continuous high temperature in the later stages of braking leads to severe oxidative wear. The newly formed TBL covers the original surface to form a multilayered structure, indicating the TBL undergoes destruction and regeneration.

关键词： c c-Sic friction third-body layer tribological behavior wear mechanism

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comprehensive determination of seven polyphenols in Eucommia ulmoides and its anti-oxidative stress activity in c. elegans

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JOURNAL OF FOOD MEASUREMENT AND cHARAcTERIZATION 2019年第4期13卷 2903-2909页

作者： Hou, Peilin Wang, Qing Qi, Wuqin Zhang, Yanqing Xie, Junbo Tianjin Univ Commerce Coll Biotechnol & Food Sci Tianjin 300134 Peoples R China Tianjin Univ Tradit Chinese Med Sch Chinese Mat Med Tianjin 301617 Peoples R China

In this study, an efficient HPLc method was developed and validated to determine seven polyphenols, i.e. chlorogenic acid, caffeic acid, protocatechuic acid, geniposide, rutin, quercetin and isorhamnetin, in different parts (leaves, barks and fruits) of Eucommia ulmoides. A Luna c-18 column (150 mm x 3.9 mm, 5.0 mu m) was applied and eluted with a gradient of acetonitrile-modified aqueous mobile phase (containing 1% acetic acid). 260 nm, 326 nm, and 360 nm were used as the detection wavelengths. With the developed method, these seven polyphenols were successfully assayed and their contents in different parts of E. ulmoides were compared. The results showed that these polyphenols displayed different distribution in the leaves, barks and fruits. chlorogenic acid, caffeic acid and rutin were their main common constituents. ABTS and DPPH free radical scavenging assay indicated that E. ulmoides displayed significant antioxidant activities in vitro. In addition, the extracts of the three parts can significantly increase the anti-oxidative stress level in wild-type c. elegans and prolong its lifespan, further demonstrating the antioxidant activity of Eucommia ulmoides.

关键词： Eucommia ulmoides chlorogenic acid caffeic acid Rutin Anti-oxidation c elegans

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Effect of a Ti plus c Granule Size on combustion in a Nitrogen Flow

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cOMBUSTION EXPLOSION AND SHOcK WAVES 2021年第1期57卷 60-66页

作者： Seplyarskii, B. S. Kochetkov, R. A. Lisina, T. G. Abzalov, N. I. Russian Acad Sci Merzhanov Inst Struct Macrokinet & Mat Sci Chernogolovka 142432 Russia

Dependence of the combustion of a Ti + c granular charge on a granule size is experimentally studied. It is revealed that the burning rate of a granular mixture of all fractions used in the work is higher than the burning rate of a bulk-density powder mixture. It is shown that, with a decrease in the granule size, the burning rate of the charge in the absence of gas decreases due to an increase in the number of boundaries between the granules per unit length of the sample. A strong influence of the nitrogen flow on the burning rate of both coarse and fine granules is established. It is shown that, in contrast to fine granules, an increase in the nitrogen flow rate of coarse granules up to 600 liters/h leads to a transition to convective combustion. The studies performed indicate that, despite the structural analogy between mechanically activated and granular mixtures, the relationship between the combustion time and the front transition time in granular mixtures is completely different. This means that the combustion of granular mixtures even in the absence of a gas flow cannot be explained within the framework of a microheterogeneous model.

关键词： SHS Ti + c granule size cocurrent gas flow convective combustion microheterogeneous model

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Laser flash photolysis of fullerols of c_(60) and of c_(70) in aqueous solutions

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Science china chemistry 1998年第3期41卷 259-265页

作者：陆长元姚思德王文锋童永彭林维真荣廷文林念芸 1. Laboratory of Radiation Chemistry Shanghai Institute of Nuclear Research Chinese Academy of Sciences 201800 Shanghai China 2. Nuclear Analysis Center Shanghai Institute of Nuclear Research Chinese Academy of Sciences 201800 Shanghai China

Fullerols of c 60 and of c 70 \ [c 60 (OH)\-\%n\%, c 70 (OH)\-\%m\%], water\|soluble fullerene derivatives, unlike some other fullerene derivatives (such as c 60 (c\-4H\-6O), c 60 (c\-3H\-7N) and c 60 [c(cOOEt)\-2]\-\%x\%), do not result in excited triplet state but in ionization via monophotonic process in aqueous solutions with 248 nm laser. The quantum yields of formation of hydrated electron ( Φ e - ) are determined to be 0.08 and 0.11 for fullerols of c 60 and of c 70 respectively at room temperature (ca. 15℃) with KI solution used as reference. By laser flash photolysis and oxidation of sulfate radical anion SO -· \-4, the fullerol radical cation or neutral radical of c 60 is confirmed to be existent and the transient absorption spectra of fullerol radical cation of c 70 are observed for the first time.

关键词： fullerol of c 60 fullerol of c 70 laser flash photolysis monophotonic ionization radical.

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combustion synthesis of c/MgAl2O4 composite powders using magnesium oxalate as carbon source

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INTERNATIONAL JOURNAL OF APPLIED cERAMIc TEcHNOLOGY 2019年第3期16卷 1253-1263页

作者： Lv, Lihua Xiao, Guoqing Ding, Donghai Ren, Yun Yang, Shoulei Yang, Pan Hou, Xing Xian Univ Architecture & Technol Coll Mat & Mineral Resources Xian Shaanxi Peoples R China

In order to solve the bottleneck problems including uniform distribution, and oxidation resistance of nano carbons in oxide ceramics, c/MgAl2O4 composite powders were prepared with Mgc2O4 center dot 2H(2)O, MgO2, Al2O3, and Al as raw materials via combustion method under argon atmosphere. The maximum adding amount of Mgc2O4 center dot 2H(2)O is 34.34 wt%. The phase compositions and microstructures of combustion products were characterized through X-ray diffraction (XRD), scanning electron microscope (SEM)/EDX, and Raman spectroscopy. The results showed that the phases of products are mainly composed of MgAl2O4 and carbon. The prepared MgAl2O4 has granular and rod-like morphologies, and the free carbon (1.172 wt%) exists between particles of MgAl2O4. Moreover, the addition of Fec2O4 as catalyst in raw materials ratio would be beneficial for improving crystallization of in situ carbon generated in the products. The oxidation activation energy of the prepared c/MgAl2O4 composite powders was calculated as 143.01 kJ/mol which was 22.17% higher than that of carbon black/MgAl2O4 powders (117.06 kJ/mol), suggesting that the c/MgAl2O4 composite powders prepared by combustion synthesis have excellent oxidation resistance.

关键词： c MgAl2O4 composite powders combustion synthesis microstructure

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