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981.
在沙尘暴应急监测方法研究中,通过对总悬浮颗粒物采样仪器及各种采样参数的研究确定和降尘采样器的研制,制定出沙尘暴应急监测方法。  相似文献   
982.
We present the first confirmed case by molecular analysis of a metaphyseal chondrodysplasia, McKusick type, in a 22-week fetus. Two novel compound heterozygous mutations, 64T> A and 79G > T, were found in the highly conserved regions of the RMRP gene. Twenty-two heterozygous g.1018 T> C mutations, two homozygous g.1018 T> C mutations, two heterozygous insertion mutations g.799_g.800insC and one heterozygous insertion mutation g.849_g.850insT were found among 100 normal controls. Careful radiological examination of the fetus for skeletal dysplasia allowed definitive diagnosis, proper genetic counselling and future prenatal diagnosis. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
983.
984.
臭氧层破坏是当前面临的全球性环境问题,为了履行自己的国际义务,认真分析本国消耗臭氧层物(ODS)的生产、消费现状,科学评估其发展趋势,提出削减消耗臭氧层物质的措施。  相似文献   
985.
Enteric duplication cyst is a congenital abnormality that is believed to arise from abnormal recanalization of the bowel during embryogenesis. Previous reports suggest that the condition may be suspected prenatally by sonographic demonstration of an intra-abdominal cystic mass in the second and third trimesters. We present the sonographic features of a fetus with ileal duplication cyst at 12 weeks of gestation, which show that the condition may present in the first trimester of pregnancy. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
986.
Second-trimester serum inhibin-A is increasingly used as a fourth marker in addition to the triple test to screen for Down syndrome. We investigated whether fetal gender had an effect on serum inhibin-A concentration. A retrospective analysis was done on 316 normal pregnancies and 48 Down syndrome pregnancies in which maternal serum inhibin-A assays were performed between 15 and 20 weeks of gestation and in which the fetal sex was known. The median inhibin-A MoM (95% CI) for normal pregnancies in the presence of a male fetus was 0.93 (range 0.88–1.03). This was significantly lower than that in the presence of a female fetus (median MoM=1.04). The gender difference was not observed in the Down syndrome pregnancies. The increased inhibin-A concentration would lead to a 2.3-fold higher false-positive rate in the presence of a female fetus (10.6% vs 4.6%; p<0.05, Chi-square test). Because of the small number of cases studied, the results need to be substantiated by a larger series. If the gender effect is confirmed, adjustment for fetal sex may be necessary when inhibin-A is used as a screening marker. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
987.
988.
New ‘critical levels’ (CLE) for assessing the effects of atmospheric ammonia on sensitive ecosystems have recently been adopted by the United Nations Economic Commission for Europe (UNECE) of 1 and 3 [2–4] μg NH3 m?3 of ambient air (including water vapour), for different species sensitivities and their associated habitats. Based on these values, we examined how indicator choice affects estimates of stock-at-risk in the European ‘Natura 2000’ network.We applied an atmospheric model, FRAME, to estimate surface air concentrations of ammonia at 5 km and 1 km resolution for the UK network of Natura sites, optionally including calibration with the National Ammonia Monitoring Network. As a base indicator, we estimated the overall percentage area of the UK Natura network that exceeded critical level thresholds (‘Area Weighted Indicator’, AWI). We compared this with an alternative approach, estimating the percentage number of Natura sites where the critical level was exceeded (‘Designation Weighted Indicator’, DWI), which we consider more relevant under the terms of the Habitats Directive.Using the AWI (with 1 km calibrated ammonia), we estimate that 11.2%, 1.3% and 0.2% area of the UK Natura network exceeds the critical level values of 1, 2 and 3 μg NH3 m?3, respectively. By contrast, using the DWI, the equivalent exceedances are 59.1%, 23.6% and 9.8%. The highest regional exceedance (DWI, critical level 1 μg NH3 m?3) was calculated for England (91.9% exceeded), and the lowest for Scotland (24.0% exceeded). High resolution maps show that the larger threat estimated by the DWI approach is explained by (i) an anti-correlation between NH3 concentration and Natura site area and (ii) the fact that exceedance over part of a Natura site is considered to represent a threat to the integrity of the whole site.  相似文献   
989.
假稻对铬的富集作用及其耐受能力研究   总被引:2,自引:0,他引:2  
假稻属的李氏禾(Leersia hexandra)是中国境内发现的铬超富集植物。研究以其同属植物假稻(Leersiajapon ica)为材料,测定了假稻对铬(Cr^3+)的富集能力及其在模拟铬污染的实验条件下的光合、生理和根系形态学指标。结果发现:(1)在0~40 mg·L^-1的Cr^3+浓度范围内,假稻根茎和叶中铬的含量随铬质量浓度的提高而升高,在培养液中铬浓度为40 mg·L^-1时,根茎中铬含量高达2 292.00 mgLkg^-1,其生物富集系数为57.30;(2)浓度为10~40 mg·L^-1的Cr^3+处理对假稻的叶绿素a和b含量、胞间CO2浓度(Ci)和气孔限制(LS)和净光合速率无明显影响;(3)叶片中脯氨酸含量变化趋势呈单峰型,在20 mg·L^-1的Cr^3+时假稻叶片脯氨酸含量达到最高;(4)随着Cr^3+浓度的升高,假稻根系的根尖数表现出升高的趋势,而根表面积(相对于对照组)也表现出增加的趋势。以上结果表明,假稻的根茎对Cr^3+有很强的富集能力,且对Cr^3+有较强的耐受性,这种耐受性有其光合生理和根系形态学上的基础,说明假稻在净化铬(Cr^3+)污染的水体环境上很有应用前景。  相似文献   
990.
不同材料固定香菇废弃菌柄对铅和镉的吸附   总被引:1,自引:0,他引:1  
研究了用聚乙烯醇-海藻酸钠(PVA-SA),海藻酸钠(SA)和琼脂三种材料固定香菇(Lentinus edodes)废弃菌柄制作成吸附小球的理化特性,初步比较了三种小球和自由菌粉的吸附能力,在此基础上进一步分析了PVA-SA香菇小球吸附Pb2+和Cd2+的动力学。结果表明,PVA-SA香菇小球的成球性,机械强度和耐酸性最好。固定小球的吸附能力比自由菌粉的有所下降,以Cd的吸附率降低幅度较大,PVA-SA香菇小球和SA香菇小球对Pb的吸附率降低幅度较小,吸附率分别为92.4%和92.7%,对Cd的吸附率分别为55.9%和58.66%。伪二级动力学模型能够很好的拟合固定小球对Pb2+和Cd2+吸附的动力学过程,相关系数R2分别为0.9999和0.9904,由伪二级动力学方程得到的Pb2+和Cd2+理论平衡吸附量qe分别为0.4926和0.1448mg/g,跟实验测定获得的数据0.4635mg/g和0.1423mg/g相近。  相似文献   
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