Antioxidant action of several β‐adrenergic blockers and related compounds

The aim of the present study was to investigate the effect of several β‐adrenergic blockers and related compounds with respect to generation of reactive oxygen species, especially hydroxyl radicals. Measurements were done using a chemiluminescence technique and the Co(II)‐EDTA + H₂O₂ system as a source of active oxygen species.     

矿山振动机械本质安全技术研究及应用

目前矿山开采领域所使用的振动机械(包括振动磨、振动筛等)的振动负荷都无一例外地传递给弹簧、机架、基础,对机器相关零部件及周围会造成不同程度的安全影响,安装要求也较高。从设备的安全性角度来说,无法达到本质安全要求。按照传统振动机械的设计理论,振动负荷向外传递无法避免,无法实现本质安全。提出振动机械设计理论,可以实现本质安全化设计。实际应用结果表明,外传的振动负荷降低95%以上,且可达到节能50%以上。     

含海水污水的短程硝化反硝化

采用SBR工艺通过控制游离氨(FA)浓度实现了含海水生活污水的短程硝化反硝化脱氮,并研究了不同海水盐度情况下,温度、pH值、NH₄⁺-N负荷等诸因素对短程硝化反硝化的影响.试验结果表明:大生活用水范围内的海水盐度情况下仍可实现短程硝化反硝化,但不同海水盐度情况下的NH₄⁺-N去除率与NHH₄⁺-N负荷有关,随着海水占生活污水比例的增加NH₄⁺-N负荷应逐渐减少.当NH₄⁺-N负荷小于0.15kg/(kg·d)时,短程硝化的NH₄⁺-N去除率仍可达到90%以上.升高温度有利于提高短程硝化脱氮效率,当温度从20℃升高到30℃时,亚硝化比增长速率增加1倍.反应温度应保持在25℃～30℃,pH值的最佳范围为7.5～8.5.较高的进水pH值有利于通过游离氨浓度控制亚硝酸型硝化的形成.     

地铁引起的地面振动传播

依埋深波源在弹性半空间的传播原理,提出了地铁波源引起的地面振动实用计算公式和传递系数。对地铁波源的P波、S波引起的地面面波叠加,得出地面振动计算公式。实用计算公式与数个地铁工程运行所致的地面振动现场实测作了比较,能满足工程精度。     

紫外活化过硫酸钠灭活水中噬菌体MS2的特性及机制

水环境中的病毒对常见的消毒技术有较强的抵抗力.为了开发水中病毒的高效灭活技术,以噬菌体MS2为对象,研究紫外活化过硫酸钠（UV/PS）体系灭活病毒的特性和机制.采用双层平板法对噬菌体MS2进行定量检测,研究UV/PS对水样中噬菌体MS2的灭活率和动力学特征,并考察PS用量、pH值和噬菌体初始浓度等因素对灭活效果的影响.利用透射扫描电镜观察UV/PS处理前后噬菌体的形貌,利用电子顺磁共振波谱法确认反应体系中存在的自由基种类.在自由基淬灭实验的基础上,分析计算UV/PS体系中各因素对噬菌体灭活的贡献率.结果表明,当紫外辐照强度为160 μW·cm^-2时,UV/PS处理4 min即可去除4.39 lg的噬菌体MS2,较单独使用同样辐照剂量的UV消毒灭活率高1.44 lg.UV/PS体系对噬菌体MS2的灭活动力学过程符合一级反应动力学模型.增加体系中的PS初始浓度能明显提高对噬菌体的灭活率和灭活速率,而pH和噬菌体初始浓度对UV/PS灭活噬菌体的影响较小.UV/PS处理可导致噬菌体的衣壳破损,促进了噬菌体颗粒团聚.UV/PS体系中存在SO₄^-·和·OH,是噬菌体MS2灭活的重要因素.·OH比SO₄^-·对噬菌体MS2灭活的贡献更大.     

应用气液两相流模型模拟湖泊风生流

采用了基于两相流理论的三维相间界面计算模型模拟湖泊风生流,并采用交错网格的有限体积法求解。该模型应用于昆明市滇池的风生流模拟,实际计算表明该模型算法程序简单,计算结果合理,能较真实的反映湖泊风生流的流态特征。     

Screening for trisomy 21 in twin pregnancies in the first trimester: does chorionicity impact on maternal serum free β-hCG or PAPP-A levels?

In a study of 180 twin pregnancies I have examined the distribution of maternal serum free β-human chorionic gonadotrophin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A), in addition to fetal nuchal translucency thickness (NT), in twins classified as monochorionic or dichorionic, based on ultrasound appearance at 10–14 weeks of gestation. In 45 monochorionic and 135 dichorionic twin pregnancies the median MoM free β-hCG was not significantly different (1.00 vs 1.01), whilst that for PAPP-A was lower (0.89 vs 1.01) but again with no statistical significance. Previous reports of an increased fetal NT in monochorionic twins pregnancies could not be confirmed (1.03 vs 1.00). It is concluded that the existing pseudo risk twin correction algorithm is appropriate for both monochorionic and dichorionic twins in providing accurate first trimester risks for trisomy 21. Copyright © 2001 John Wiley & Sons, Ltd.     

The Impact on Environmental Kuznets Curve by Trade and Foreign Direct Investment in China

1 INTRODUCTIONAs the globalization of world economy speeds up,international trade and foreign investment mainly bytransnational corporations are continuously expanding.It is against this background that the relationship betweentrade, FDI, economic growth and environmental pollutionstarted to attract close attention from scholars both athome and abroad (Dean, 1992; 2001; Copeland andTaylor, 2003; OECD, 1997; Beladi, 1999; MA, 2003).Although the idea that "economy and environment win-w…     

First trimester PAPP-A in the detection of non-Down syndrome aneuploidy

Combined first trimester screening using pregnancy associated plasma protein-A (PAPP-A), free β-human chorionic gonadotrophin, and nuchal translucency (NT), is currently accepted as probably the best combination for the detection of Down syndrome (DS). Current first trimester algorithms provide computed risks only for DS. However, low PAPP-A is also associated with other chromosome anomalies such as trisomy 13, 18, and sex chromosome aneuploidy. Thus, using currently available algorithms, some chromosome anomalies may not be detected. The purpose of the present study was to establish a low-end cut-off value for PAPP-A that would increase the detection rates for non-DS chromosome anomalies. The study included 1408 patients who underwent combined first trimester screening. To determine a low-end cut-off value for PAPP-A, a Receiver–Operator Characteristic (ROC) curve analysis was performed. In the entire study group there were 18 cases of chromosome anomalies (trisomy 21, 13, 18, sex chromosome anomalies), 14 of which were among screen-positive patients, a detection rate of 77.7% for all chromosome anomalies (95% CI: 55.7–99.7%). ROC curve analysis detected a statistically significant cut-off for PAPP-A at 0.25 MoM. If the definition of screen-positive were to also include patients with PAPP-A<0.25 MoM, the detection rate would increase to 88.8% for all chromosome anomalies (95% CI: 71.6–106%). This low cut-off value may be used until specific algorithms are implemented for non-Down syndrome aneuploidy. Copyright © 2001 John Wiley & Sons, Ltd.     

Maternal serum levels of total activin-A in first-trimester trisomy 21 pregnancies

Maternal serum total activin-A concentration was measured in 45 pregnancies affected by trisomy 21 and 493 control unaffected pregnancies at 10–14 weeks of gestation. In the trisomy 21 pregnancies total activin-A concentration was significantly higher (1.36 MoM of the unaffected pregnancies) and in 16% of cases the level was above the 95th centile of normal. The log₁₀ SD for the control group and the trisomy 21 group were 0.17 and 0.22, respectively. The median pregnancy associated plasma protein-A (PAPP-A) in this trisomy 21 series was 0.49 and for free β-hCG was 2.05. In the trisomy group there were significant positive associations between total activin-A and PAPP-A (0.6071) and free β-hCG (0.4255). The low median difference and the high overlap in values between trisomic and unaffected pregnancies make total activin-A of little practical use in first-trimester screening for trisomy 21. Copyright © 2001 John Wiley & Sons, Ltd.