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相同和易性和强度条件下天然砂和机制砂混凝土配合比研究 被引量:4
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作者 林天乐 陈振光 +4 位作者 张春英 范同发 马腾 张利锋 钱晓倩 《混凝土与水泥制品》 2023年第5期17-21,26,共6页
研究了相同和易性和强度等级条件下,天然砂混凝土和机制砂混凝土配合比的差异。结果表明:在坍落度40~200 mm、强度等级C20~C45范围内时,通过同时提高2%~4%的砂率和0.037~0.082的浆骨比,可以使机制砂混凝土具有与天然砂混凝土相同的和易... 研究了相同和易性和强度等级条件下,天然砂混凝土和机制砂混凝土配合比的差异。结果表明:在坍落度40~200 mm、强度等级C20~C45范围内时,通过同时提高2%~4%的砂率和0.037~0.082的浆骨比,可以使机制砂混凝土具有与天然砂混凝土相同的和易性;当水灰比相同时,砂率和浆骨比的调整并不影响机制砂混凝土的28 d抗压强度,水灰比定则对机制砂混凝土仍然适用;当坍落度相同时,随着强度等级的提高,机制砂混凝土较天然砂混凝土的浆骨比增量增加;在低坍落度(40 mm)条件下,对于不同强度等级的混凝土,掺加减水剂均可减少机制砂对混凝土砂率和浆骨比的影响。 展开更多
关键词 机制砂 天然砂 配合比 和易性 混凝土强度 坍落度
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Establishment and characterization of two new human embryonic stem cell lines,SYSU-1 and SYSU-2 被引量:3
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作者 HUANG Guo LI Wei-qiang +7 位作者 chen Rui chen zhen-guang ZHANG Xiu-ming MAO Fu-xiang HUANG Shao-liang LI Shu-nong Bruce T Lahn Andy Peng Xiang 《Chinese Medical Journal》 SCIE CAS CSCD 2007年第7期589-594,共6页
Background Human embryonic stem cells can propagate indefinitely in vitro and are able to differentiate into derivatives of all three embryonic germ layers. The excitement surrounding human embryonic stem cells lies l... Background Human embryonic stem cells can propagate indefinitely in vitro and are able to differentiate into derivatives of all three embryonic germ layers. The excitement surrounding human embryonic stem cells lies largely in their potential to produce specialized cells that can be used for transplant therapies. However, further investigation requires additional cell lines with varying genetic background. Therefore, efforts to derive and establish more human embryonic stern cell lines are highly warranted. Methods Surplus embryos (blastocysts) from donors were used to isolate the inner cell mass by immunosurgery. All cells were cultured continuously on irradiated murine embryonic fibroblasts feed layer and likely human embryonic stem cell colonies were subsequently characterized by cell surface marker staining, karyotyping and teratoma formation. Results Two human embryonic stern cell lines (SYSU-1 and SYSU-2) were established from surplus embryos. The two lines express several pluripotency markers including alkaline phosphatase, SSEA- 4, Tra-1-60, Oct-4, Nanog and Rex-1. They remain in undifferentiated state with normal karyotype after prolonged passages and can form embryoid bodies in vitro and teratoma in vivo. Conclusion Two new human embryonic stem cell lines have been established from surplus embryos. They can be used to understand selfrenewal and differentiating mechanisms and provide more choices for regenerative medicine. 展开更多
关键词 embryonic stem cells blastocysts inner cell mass cell differentiation
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