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101.
Y-α-sialon ceramics with different compositions were hot-press sintered. Varying the m or n value in theα-Sialon general formula, both the α-sialon grain morphology and phase assemblages present diversification, therefore, affecting the toughness and hardness. Meanwhile, varying the compositional parameters also influenced the composition and structure of the intergranular glass phase, as well as its oxidation behavior at 1100-1200 ℃. The oxidation of the intergranular phase Mt in the Y-α-sialon ceramics was significantly enhanced with further rising the oxidation temperature to 1300 ℃. 相似文献
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Emily B. Button Andrew S. Mitchell Marcia M. Domingos Jessica H.-J. Chung Ryan M. Bradley Ashkan Hashemi Phillip M. Marvyn Ashley C. Patterson Ken D. Stark Joe Quadrilatero Robin E. Duncan 《Lipids》2014,49(4):305-316
Neuroinflammation is a component of age-related neurodegenerative diseases and cognitive decline. Saturated (SFA) and monounsaturated (MUFA) fatty acids are bioactive molecules that may play different extrinsic and intrinsic roles in neuroinflammation, serving as exogenous ligands for cellular receptors, or endogenous components of cell structural, energetic and signaling pathways. We determined the fatty acyl profile of BV2 microglial cells before and after acute activation with lipopolysaccharide (LPS). We also investigated the effect of SFA and MUFA pretreatment on the production of an invasive, neurotoxic phenotype in BV2 cells. Acute activation of BV2 microglia resulted in an increase in the relative content of SFA (12:0, 16:0, 18:0, 20:0, 22:0, and 24:0 increased significantly), and a relative decrease in the content of MUFA (16:1n7, 18:1n7, 18:1n9, 20:1n9, 24:1n9 decreased significantly). In agreement, the major stearoyl-CoA desaturase (SCD) isoform in BV2 cells, SCD2, was significantly down-regulated by LPS. We next treated cells with SFA (16:0 or 18:0) or MUFA (16:1n7 or 18:1n9), and found that levels of secreted IL6 were increased, as was secreted MMP9-mediated proteolytic activity. To test the functional significance, we treated SH-SY5Y neuronal cells with conditioned medium from BV2 cells pretreated with fatty acids, and found a small but significant induction of cell death. Our findings suggest differential intrinsic roles for SFA and MUFA in activated microglial cells, but similar extrinsic roles for these fatty acid species in inducing activation. Expansion of SFA is important during microglial cell activation, but either supplemental SFA or MUFA may contribute to chronic low-grade neuroinflammation. 相似文献
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利用有机酸对Y型分子筛进行改性,采用XRD、XRF、XPS和IR等对其进行表征,结果表明,分子筛经过离子交换降低钠含量,水热焙烧后,采用有机络合剂进行处理,更有利于得到结晶度高和非骨架铝含量低的分子筛;在相同柠檬酸或草酸比例下,采用柠檬酸处理的样品,其硅铝物质的量比和结晶度均高于草酸处理样品;有机酸处理有利于分子筛非骨架铝的脱除,尤其分子筛外表面非骨架铝的脱除,提高分子筛结晶度和硅铝物质的量比。m(柠檬酸)∶m(分子筛)=a∶1~(a+0.10)∶1时,晶胞尺寸变化不大;m(柠檬酸)∶m(分子筛)=(a+0.15)∶1时,分子筛晶胞进一步收缩,结晶度降低;随着柠檬酸比例增加,脱铝处理分子筛的B/L降低。 相似文献
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《Materials Science & Technology》2013,29(2):144-150
AbstractThe microstructures of silicon alloyed γ-Ti–Al alloys containing silicide particles have been studied after thermomechanical treatments to investigate microstructural evolution. Important parameters including temperature, forging strain, and sequence of thermomechanical treatments were systematically studied. Isothermal forging below the eutectoid temperature resulted in inhomogeneous dynamic recrystallisation with fine equiaxed grains in recrystallised areas and residual α2 + γ lamellae elsewhere. Eutectic silicides play an important role in destruction of the as cast structure by promoting dynamic recrystallisation during deformation and static recrystallisation on subsequent annealing. There is evidence that silicon, in solution, also enhances recrystallisation. The presence of fine silicides produced by precipitation in the solid state restricts the size of grains produced by both dynamic and static recrystallisation. Silicon also alters significantly the phase equilibrium between the α and γ phases. 相似文献
108.
研究了相变温度附近等温热处理温度和保温时间对含长周期结构Mg97Zn1Y2合金的组织的影响,并对演变机理进行了探讨。主要研究结论如下:500℃固溶处理时,随着时间的增加,长周期结构有增长的趋势。采用等温热处理可以将Mg97Zn1Y2合金中的枝晶组织转变为球状晶,当合金保温温度范围从540℃~600℃时,组织尺寸由大-小-大的顺序变化,即经过了粗化、分离及球化至最后粗化三个过程。在等温热处理温度为575℃的组织大致演变趋势为:枝晶态-不规则球形+块状-球形状,当保温时间15min,其组织为均匀、圆整的球状晶。 相似文献
109.
Abstract A transfer admittance is treated as a two‐terminal network driven by cascaded dependent sources. By complex‐curve fitting, each of the four admittances of a conventional two‐port model can be approximated over a wideband with a rational function of frequency. A SPICE2‐acceptable R‐L‐C two‐port model can then be derived by applying continued fractions to the rational functions. Examples are included to demonstrate the applications of this method. 相似文献
110.
The effect of Zn and Y on hot-tearing susceptibility (HTS) of Mg–xZn–2xY (x?=?1, 1.67, 2.67) alloys is investigated. It is found that the microstructure of the alloys is mainly composed of α-Mg, long-period stacking-ordered (LPSO) phase and W-phase. Both theoretical and experimental results illustrated that HTS of the investigated alloys is in the following order: Mg–1Zn–2Y > Mg–1.67Zn–3.34Y > Mg–2.67Zn–5.34Y. For Mg–2.67Zn–5.34Y alloy, LPSO phase content reaches at the maximum and its grain size reaches at minimum of 16.4 µm, and the pinning effect of the LPSO phase on grain boundaries is considered to be an important reason for reducing HTS of the alloy. 相似文献