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稳定同位素交换反应平衡常数与平衡分馏因子的关系——过量因子的实质及计算方法
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作者 张继习 刘耘 《矿物学报》 CAS CSCD 北大核心 2011年第1期126-132,共7页
理论计算稳定同位素平衡分馏因子(α),是以计算平衡常数K为桥梁,但是K与α之间并非简单的指数关系,二者之间还存在一个较为神秘的过量因子X(excess factor)。然而,几乎所有的理论计算工作都直接忽略了过量因子,并没有人详细研究过过量... 理论计算稳定同位素平衡分馏因子(α),是以计算平衡常数K为桥梁,但是K与α之间并非简单的指数关系,二者之间还存在一个较为神秘的过量因子X(excess factor)。然而,几乎所有的理论计算工作都直接忽略了过量因子,并没有人详细研究过过量因子的实质及其可以被忽略的条件,因此,针对这个现状,本文从最基础的理论推导开始,精确推导了α和K之间的关系,并得到了过量因子的具体表达式,同时也给出了β因子(一种物质与其理想气态原子之间的平衡分馏因子)和同位素约化配分函数比(RPFR)之间的具体关系式。本文还以石膏与溶液中硫酸根之间的硫和氧同位素的分馏为实例,具体展示了过量因子产生的原因和计算方法,也提供了精确的石膏和硫酸根之间的硫和氧同位素的平衡分馏参数。 展开更多
关键词 平衡分馏因子 平衡常数 过量因子 β因子 Bigeleisen-Mayer公式 石膏-硫酸根分馏
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负支离轴共焦非稳腔过量噪声的研究
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作者 吴超 唐霞辉 +2 位作者 李根 王炜 王振 《激光技术》 CAS CSCD 北大核心 2016年第6期882-887,共6页
为了解决条状负支离轴非稳腔输出线宽增宽的问题,分析非稳腔的主要两个参量——有效菲涅耳数N_(eff)和几何放大率M与输出模式的过量噪声因子K取值的函数关系,从负支腔的具体结构出发,采用经典波动方程的理论唯像的将过量噪声因子表示成... 为了解决条状负支离轴非稳腔输出线宽增宽的问题,分析非稳腔的主要两个参量——有效菲涅耳数N_(eff)和几何放大率M与输出模式的过量噪声因子K取值的函数关系,从负支腔的具体结构出发,采用经典波动方程的理论唯像的将过量噪声因子表示成输出平面横模分布的泛函,利用边界衍射波的方法将输出横模近似地解析表述成N_(eff)和M的函数。利用该关系数值计算了K随N_(eff)和M变化的情况。结果表明,K随N_(eff)呈现准周期性变化,在N_(eff)≈s+0.85处(s为正整数)呈现周期性峰值,输出线宽将被增宽到自然线宽的2000倍左右。该研究对分析非稳腔的输出损耗是有帮助的,并为实际激光器的设计提供了参考。 展开更多
关键词 激光光学 经典波动方程 过量噪声因子 模式双正交 负支离轴共焦非稳腔 横模
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短沟道下共栅结构宽带CMOS LNA的设计
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作者 王小力 袁刚 《微电子学》 CAS CSCD 北大核心 2009年第2期141-145,共5页
基于短沟道MOS器件的过量因子随沟道长度降低缓慢增加的特征,研究了短沟道下共栅结构宽带低噪声放大器的噪声性能,并在0.18μm CMOS工艺下设计实现了共栅结构的宽带低噪声放大器。流片测试结果表明,在1.8 V电源电压、4.1 mA工作电流下,... 基于短沟道MOS器件的过量因子随沟道长度降低缓慢增加的特征,研究了短沟道下共栅结构宽带低噪声放大器的噪声性能,并在0.18μm CMOS工艺下设计实现了共栅结构的宽带低噪声放大器。流片测试结果表明,在1.8 V电源电压、4.1 mA工作电流下,该系统获得6.1 dB的最小噪声系数;综合性能与长沟道下相近,符合理论分析和设计要求。 展开更多
关键词 CMOS 过量因子 共栅结构 低噪声放大器 宽带低噪声放大器
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Upregulation of hypoxia inducible factor 1α mRNA is associated with elevated vascular endothelial growth factor expression and excessive angiogenesis and predicts a poor prognosis in gastric carcinoma 被引量:29
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作者 Jie Ma Li Zhang +2 位作者 Guo-Qing Ru Zhong-Sheng Zhao Wen-Juan Xu 《World Journal of Gastroenterology》 SCIE CAS CSCD 2007年第11期1680-1686,共7页
AIM: To investigate the implication of the hypoxia inducible factor HIF-1α mRNA in gastric carcinoma and its relation to the expression of vascular endothelial growth factor (VEGF) protein, tumor angiogenesis inva... AIM: To investigate the implication of the hypoxia inducible factor HIF-1α mRNA in gastric carcinoma and its relation to the expression of vascular endothelial growth factor (VEGF) protein, tumor angiogenesis invasion/metastasis and the patient's survival. METHODS: In situ hybridization was used to examine expression of HIF-1α mRNA, and immunohistochemical staining was used to examine expression of VEGF protein and CD34 in 118 specimens from patients with gastric carcinoma. RESULTS: The positive rates of HIF-1α mRNA and VEGF protein were 49.15% and 55.92%, respectively. Positive expressions of HIF-1α and VEGF in stage T3-T4 tumors and those with vessel invasion, lymph node metastasis and distant metastasis were dramatically stronger than stage T1-T2 cases and those without vessel invasion, lymph node metastasis and distant metastasis. The mean microvascular density (MVD) in stage T3-T4 tumors and those with vessel invasion, lymph node metastasis and distant metastasis was significantly higher than stage T1-T2 tumors and those without vessel invasion, lymph node metastasis and distant metastasis. The mean MVD in tumors with positive HIF-1α and VEGF expression was significantly higher than that in tumors with negative HIF-1α and VEGF expression. The expression of HIF- 1α was positively correlated with VEGF protein. There were positive correlations between MVD and expression of HIF-1α and VEGF. The mean survival time and the S-year survival rate in cases with positive expression HIF-1α and VEGF and MVD value ≥ 41.5/0.72 mm^2 were significantly lower than those with negative expression of HIF-1α and VEGF and MVD value 〈 41.5/0.72 mm^2. CONCLUSION: Overexpression of HIF-1α is found in gastric carcinoma. HIF-1α may induce the angiogenesis in gastric carcinoma by upregulating the transcription of VEGF gene, and take part in tumor invasion and metastasis. They can be used as prognostic markers of gastric cancer in clinical practice. 展开更多
关键词 Gastric carcinoma HIF-1α Vascularendothelial growth factor Microvascular density Prognosis
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Inhibiting Human Copper Transfer and Tumor Growth
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《Bulletin of the Chinese Academy of Sciences》 2015年第4期250-250,共1页
Copper is a trace element that is required by almost all forms of life.Acting as cofactors for various key metabolism enzymes,copper takes part in many vital biological processes.Previous studies have found the concen... Copper is a trace element that is required by almost all forms of life.Acting as cofactors for various key metabolism enzymes,copper takes part in many vital biological processes.Previous studies have found the concentration of copper is significantly higher in tumor cells than in normal cells.In addition,copper can promote angiogenesis by activating VEGF and FGF signaling. 展开更多
关键词 metabolism activating angiogenesis vital signaling enzymes biochemical regulate targeting Nature
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