Second trimester ultrasound screening for chromosomal abnormalities

The use of prenatal ultrasound has proven efficacious for the prenatal diagnosis of chromosomal abnormalities. The first sonographic sign of Down syndrome, the thickened nuchal fold, was first described in 1985. Since that time, multiple sonographically-identified markers have been described as associated with Down syndrome. The genetic sonogram, involving a detailed search for sonographic signs of aneuploidy, can be used to both identify fetuses at high risk for aneuploidy and, when normal, can be used to decrease the risk for aneuploidy for a pregnancy when no sonographic markers are identified. Combining the genetic sonogram with maternal serum screening may be the best method of assessing aneuploidy risk for women who desire such an assessment in the second trimester. Trisomy 18, Trisomy 13, and triploidy are typically associated with sonographically identified abnormalities and have a high prenatal detection rate. The use of the described sonographic signs in low-risk women requires further investigation, however, patients at increased risk for aneuploidy due to advanced maternal age or abnormal serum screening can benefit from a genetic sonogram screening for sonographic signs of aneuploidy to adjust their baseline risk of an affected fetus. Copyright © 2002 John Wiley & Sons, Ltd.     

CuAPO-5分子筛催化氧化水溶液中苯酚的性能

以水热晶化法合成了铜磷铝分子筛CuAPO-5，并用XRD、SEM，FT—IR，UV—Vis等对样品进行了表征，结果表明Cu^2＋进入到了AlPO4-5分子筛骨架中。研究了以CuAPO-5为催化剂，H2O2为氧化剂对水溶液中苯酚的催化氧化性能。在苯酚初始浓度200mg／L、H2O2添加量1200mg／L、pH值5．0、处理温度80℃时，处理240min时苯酚去除率达到100％，TOC去除率达81．76％，析出到溶液中Cu^2＋浓度仅为0．527mg／L。温度从40℃上升到80℃时，苯酚的去除率及TOC去除率明显增大，表明温度对催化剂的活性影响显著，相比于均相催化剂骨架Cu催化过氧化氢分解需要更多的能量。重复性实验表明，催化剂性能稳定。     

Molecular Weight Changes and Polymeric Matrix Changes Correlated with the Formation of Degradation Products in Biodegraded Polyethylene

The molecular weight changes in abiotically and biotically degraded LDPE and LDPE modified with starch and/or prooxidant were compared with the formation of degradation products. The samples were thermooxidized for 6 days at 100°C to initiate degradation and then either inoculated with Arthobacter paraffineus or kept sterile. After 3.5 years homologous series of mono- and dicarboxylic acids and ketoacids were identified by GC-MS in abiotic samples, while complete disappearance of these acids was observed in biotic environments. The molecular weights of the biotically aged samples were slightly higher than the molecular weights of the corresponding abiotically aged samples, which is exemplified by the increase in from 5200 g/mol for a sterile sample with the highest amount of prooxidant to 6000 g/mol for the corresponding biodegraded sample. The higher molecular weight in the biotic environment is explained by the assimilation of carboxylic acids and low molecular weight polyethylene chains by microorganisms. Assimilation of the low molecular weight products is further confirmed by the absence of carboxylic acids in the biotic samples. Fewer carbonyls and more double bonds were seen by FTIR in the biodegraded samples, which is in agreement with the biodegradation mechanism of polyethylene.     

CA-125 as a maternal serum marker for Down's syndrome in the first and second trimesters

CA-125, alpha-fetoprotein (AFP), and human chorionic gonadotropin (HCG) were determined in maternal serum in the first trimester from 14 women with a Down's syndrome fetus and 61 women with a healthy fetus. In the second trimester, 15 and 60 serum samples were determined from women with a Down's syndrome and a healthy fetus respectively. In both trimesters, maternal serum CA-125 was found to be elevated in Down's syndrome pregnancies compared with controls. Using discrimination functions, our preliminary results indicate that CA-125 is a better marker than AFP and HCG respectively for a Down's syndrome fetus in the first trimester and improves the detection rate in the second trimester.     

Mesoporous molecular sieve-based materials for catalytic oxidation of VOC: A review

As the main contributor of the formation of particulate matter as well as ozone, volatile organic compounds(VOCs) greatly affect human health and the environmental quality. Catalytic combustion/oxidation has been viewed as an efficient, economically feasible and environmentally friendly way for the elimination of VOCs. Supported metal catalyst is the preferred type of catalysts applied for VOCs catalytic combustion because of the synergy between active components and support as well as its flexi...     

Prediction of aqueous solubility of PCBs based on molecular structure

The thermodynamic relationships among aqueous solubility and molar volume (MV) , total molecular surface area (TSA) and molecular connectivity index (MCI) for highly hydrophobic chemicals. PCBs are established and discussed, respectively. Good linear relationships exist among In Cs and MV, TSA or MCI.     

有机磷农药毒性预测模型研究

选用化合物分子拓扑学的信息理论指数、价分子连接性指数，运用多元非线性回归分析，对１１４种有机磷农药大鼠经口、小鼠经口及大鼠经皮急性毒性ＬＤ５０、神经毒性作用进行了定量预测分析。回归模型相关指数Ｒ＾２均在０．８１以上，残差呈正态分布，预测效果满意，显示了系统具有较强的预测能力。     

Adsorptive behaviors of humic acid onto freshly prepared hydrous manganese dioxides

This study focused on the adsorptive behaviors of humic acid onto freshly prepared hydrous MnO₂(s) (δMnO₂), and investigated the feasibility of employing δMnO₂ for humic acid removal from drinking water. Effects of such parameters as molecular mass of humic acid, kinds of divalent cations on adsorptive behaviors and possible mechanisms involved were investigated. This study indicated that humic acid with higher molecular mass exhibited more tendency of adsorbing onto δMnO₂ than that with lower molecular mass. Ca²⁺ facilitated more humic acid adsorption than Mg²⁺; UV-Vis spectra analysis indicated higher capabilities of Ca²⁺ coordinating with acidic functional groups of humic acid than that of Mg²⁺. Additionally, ζ potential characterization indicated that Ca²⁺ showed higher potential of increasing gz potential of δMnO₂ than Mg²⁺. Ca²⁺ of 1.0 mmol/L increased ζ potential of δMnO₂ from −37 mV (pH 7.9) to +7 mV (pH 7.2), while 1.0 mmol/L Mg²⁺ increased to lower value as −9 mV (pH 6.5), correspondingly. Fourier transform infrared (FTIR) spectra demonstrated the adsorption of humic acid onto δMnO₂, showing the important roles of-COO⁻ functional groups and surface Mn-OH in the adsorption of humic acid onto δMnO₂. Translated from Acta Scientiae Circumstantiae, 2005, 25(3): 351–355 [译自: 环境科学学报]     

剩余臭氧气体分解实验研究

应用强电离介质阻挡放电技术产生的高浓度臭氧气体 ,溶于水后生成的高浓度臭氧水 ,是一种强氧化剂 ,在工业上广泛应用。然而常用的混合器中臭氧不可能被完全利用 ,排出的剩余臭氧气体的浓度较高 ,远大于一类区浓度限值 0 .1 6mg/m3。论述一种利用分子筛吸附与加热相结合的分解方法 ,具有良好效果 ,且设备简单易操作 ,已应用于小型高浓度臭氧水产生设备配套装置中。     

分子表面积的解析计算和它与正辛醇/水分配系数的相关性

详细列出了分子表面积计算中所用的公式，并详尽地说明了所涉及各量的计算方法和应用注意的问题。在此基础上编写的ＳＡＳＡ程序成功地应用于酚取代衍生物，所得表面积对于氯化酚能很好地预言其正辛醇／水分配系数，但对于带７种不同取代基的酚取代衍生物，除了分子表面积，还必须引入代基当量作描述变量，才能较好地预言其正辛醇／水分配系数，而且个别化合物应 被看作ｏｕｔｌｉｅｒ，不能正确地被预言。